- Dipslides & Incubators
- Humidity & Leak Detection
- Shelf-Life & Storage
- Water Quality
Yes. For example, or Chlorine paper (10-200ppm) will get a good reading, but the Mid-Level chlorine plastic strip (0-200ppm) will not work with trichloramines.
The difference is explained by the “type” of chlorine that each strip reacts to.
The paper strip is based on the potassium iodide starch reaction and will react to both “free” and “total” chlorine. The Mid-Level plastic chlorine test strip uses a red-ox indicator and only reacts to “free” chlorine.
“Free” chlorine is the combination of hypochlorous acid and hypochlorite present in the solution. The amount of each is dependent on the pH of the solution. At neutral pH and lower, the hypochlorous acid form dominates.
“Total” chlorine is the combination of “free” chlorine and “combined” chlorine (chlorine combined with ammonia to form monochloramine, dichloramine, and trichloramine).
Therefore, if you are monitoring solutions containing chloramines, you should use the paper chlorine strips. To get any response with the plastic strips, you would have to add much more chlorine.
No. The Phosphate test strip uses the Molybdenum Blue method and detects only orthophosphates.
Tripolyphosphates must be converted to orthophosphate first to be detected. This can be accomplished by treating the sample with acid first, and then neutralizing the solution before using the test strip.
Remember that the Phosphate test strip gives ppm as Phosphate, not phosphate ion. The result should be corrected for any dilutions/additions and multiplied by 3 to arrive at the phosphate ion ppm.
The ammonia 0-100ppm test strip technically has two test pads put together. One pad absorbs the dissolved ammonia and converts it to a gas, which the second pad registers and then changes color when dipped into an Ammonia solution.
We ran a test to see if it would work to detect ammonia gas. The short answer is yes, however, the color chart is not calibrated to the correct colors for this application.
The test was performed using 4 test strips:
- Strip 1 was left as is, dry.
- Strip 2 was dipped in DI water.
- Strip 3 was left dry and held over ammonia fumes from a bottle of cleaner for just a few seconds.
- Strip 4 was dipped in DI water, then held over ammonia fumes from a bottle of cleaner for just a few seconds.
The results of the test are shown below:
If you are experiencing different results (taste of bitterness, then no taste at all) with the PTC paper, there might be a few explanations.
Sensitivity to PTC is based on a genetic disposition, so it seems likely that a positive one time should give a positive the next time. There does appear to be evidence that results with the same individual can vary as much as 8 times. This may be what you are experiencing.
It does make sense to limit intake of food or drink prior to the test, since it may be possible to offset or mask the effect. Have a supply of water available to rinse out your mouth (spit) to eliminate the bitter taste. There is also mention in some literature that smoking can diminish a person’s ability to detect PTC.
PTC paper is very stable, so it’s unlikely the paper is too old to work. A couple of other unlikely possibilities might be that the paper didn’t get proper soaking treatment during manufacturing or the paper was Control paper and not PTC. These situations are both very unlikely, and could be tested by trying a strip from another vial or batch.
Iodine solutions prepared at the concentrations on the color chart should react with the paper. It is important to dip the strip the full 60 seconds. The reaction takes place very slowly.
On the other hand, the reaction of the same iodine paper to chlorine is very fast. If you have access to regular household bleach (typically 5-8% available chlorine depending on the manufacturer) you can take a tablespoon of bleach and mix it into a gallon of water. Using the test papers, the iodine strip should develop a deep blue/purple color. If it does not, then something is wrong with the test papers. If it does develop the deep blue/purple color with chlorine, then the problem is not the strips.
Can the Quick Response QAC (QAC-400) test strips be used to test clean surfaces by first dipping the strip in distilled water, and then pressing on a dry, cleaned food contact surface to obtain a result?
Answer: The QAC QR test strips and color chart were developed for use in water solutions, such as a three sink setup. They might detect qac residual on surfaces as described above, however, the color response won’t correlate to the color chart. The indicator in the test paper is fairly sensitive. It might work but it would need to be evaluated carefully.
The Glucose test strips were originally developed to test for glucose levels in urine for educational purposes (not medical diagnosis). Other uses include osmosis experiments where a glucose/starch solution is used to demonstrate the concept in a classroom setting.
The strips will also detect glucose levels in food, however, there are several things to consider:
1) The enzyme used to detect the glucose is specific for glucose sugar. Other sugars will not be detected by the test strip.
2) While exclusive for glucose sugar, other chemicals can interfere. The best (or worst) example is Vitamin C. The strips will not work well with foods high in Vitamin C.
3) In order for the enzyme to work properly, the solution being tested may need to sit for up to 3 hours to allow mutarotation to occur.
The pH of wine usually falls between 3 and 4. A lower pH tends to have an acidic taste, whereas a higher pH wine will spoil faster. The sulfite strips should work well within the pH range of 2.8 – 4.4. The lower the pH, the more acidic the sample. A pH of 3 is 10 times more acidic than a pH of 4. The pH scale is a logarithmic scale, like the Richter scale for earthquakes, only in the case of pH, lower numbers are stronger (a negative logarithmic scale).
The SDS for each taste test paper lists the ingredients. The concentration of ingredients is usually so small, it is less than what would be considered hazardous. Aside from these small quantities, the cellulose paper is the only other ingredient. In addition, the proper use of each taste test is to touch the strip to the tongue. These taste strips have been used safely in classrooms for decades.
The manufacturing facility where the PTC paper is produced (Cottonwood, AZ) is a typical manufacturing site. We don’t manufacture nuts or other products usually associated with allergy concerns. Please note, however, that the facility is not certified or considered an allergy-friendly manufacturing facility. In addition, the raw materials used in producing the taste test papers are not procured in any special fashion. We have no assurance that they were produced in an allergy-free environment.
Despite the above information, if you have a concern about a possible allergic reaction, perhaps it would be best to abstain from the activity.
The Vitamin C test strip uses 2,6-dichlorphenolindophenol as a red-ox indicator. This indicator changes from blue to colorless as the amount of ascorbic acid (Vitamin C) increases. Unfortunately, this indicator also detects other acids by changing from blue to red.
To help offset this effect, we include buffer salts in the formulation. This works for many applications, but it doesn’t work as well when the other acid is present in large amounts (such as in some fruit). In this situation, the starting blue color becomes more lavender.
This is why we have constructed a color scheme showing the effect of citric acid on the Vitamin C strip. Citric acid was chosen because of the likelihood that it would be present in some of the same solutions being tested for Vitamin C. The mechanism for the color change is based on the effect of pH on the indicator.
The Lead Acetate paper detects the presence of sulfur. The strip works best when wet (when testing for sulfur gas – the gas absorbs into the wet paper) or dipped into a test solution. The sulfur will form a black precipitate with the lead, lead sulfide. In dilute solutions, the paper may turn grey, and not black. The detection limit in solution is 5 ppm.
The potassium iodide test papers use the potassium iodide starch reaction. The iodide is oxidized to iodine that then reacts with the starch to form the blue/purple color. The strips can be used directly in solution being tested. There is no need to wet them with acid that we know of. These strips will react once the contact the solution. Be aware that concentrated solutions may immediately “bleach out” the strip. This usually results in a telltale stripe at the water/dry strip interface.
The pad for reading the results is the one at the bottom of the channel or well. When laid on a table with the “bump” facing up, it is the pad you can see. This is going to be the darker pad.
The other pad is flush with the “back” of the strip. When constructed, the first pad (the one to read) is laid in the channel and the second pad placed on top of the first pad. The two pads are then secured in place by taping the back of the card.
The color scale for the 0-100 ppm peroxide strip is very dependent on the pH of the solution being tested. The test pad on the strip is buffered in the range of 5.5-6.0. The capacity of this buffer system should be sufficient to keep the pH in that range for diluted, water-based peroxide solutions. The enzyme used in the test pad, which in conjunction with an indicator and the peroxide, produces the blue color on the scale in proportion to the level of peroxide present. This enzyme is most effective in a pH range of 5-7. Solutions with pH below 5 and above 7 significantly reduce the activity of the enzyme and may result in colors that do not match any on the color chart. If possible, adjust the pH of solutions being tested to the 5-7 range before using the strips. Make sure to take any dilution into account when arriving at the final peroxide concentration.
The dipslides estimate counts in CFU per mL. Drinking water is usually measured on a per 100 mL basis. The lowest dipslide number of 1000 CFU per mL which is equivalent to 100,000 CFU per 100 mL. This is well above the limit for swimming (200 CFU per 100 mL) and drinking water (< 1 CFU per 100 mL). Drinking water should be tested using EPA-accepted test methods such as pour plate and MPN.
If a dipslide is used as a substitute for a pour plate method, it is important to take the surface area of the dipslide into account. The surface area of the dipslide is 0.1 mL. A hard count of 1 colony is 1 per 0.1 mL or 10 CFU per mL. This is 1000 CFU per 100 mL – still 5x above the swimming limit and well above the drinking water limit. Note: The presence of a colony on a dipslide after incubation would be a FAIL for drinking water. The absence of a colony should NOT be considered a PASS. Due to the limited sample volume (or contact area) it is quite possible that water above the drinking water limit might not grow a colony on the dipslide.
The dipslides should be used to estimate gross contamination.
1) The pads on the strips are yellow when they are made. If they are not yellow then they have been exposed to heat, humidity, light, or some other detrimental condition.
2) The test strips will change color outside the pH range shown on the color chart. The strips will turn purple in alkaline waters. There is a way to check this. Concentrated bleach will turn the strips purple and then yellow and then white as the paper bleaches out. Dilute bleach will turn the strips purple and then eventually a greenish color if they sit out for a few minutes. In acids, there isn’t as much change. When testing vinegar (dilute acetic acid) they should remain yellow. I have tried the strips using both concentrated and dilute acetic acid – both were yellow. You might try adding a little vinegar or bleach to small samples of the water to confirm that the strips react as expected.
3) Temperature has a slight effect on the test results. It seems that raising the temperature from 25C to 70C causes the color to shift about ½ a color unit higher.
4) When testing RO, distilled, or tap water, the strips might not behave as one might expect. The indicators used with the strips require that the waters being tested have some buffering capacity. RO and distilled waters have little or no buffering capacity and the strips will not work in these waters. If the tap water has a very low buffer capacity (low hardness, low alkalinity, etc.) the color can take much longer than the recommended 1-2 second immersion and 10-15 development time. We ran a test to find results on various buffer solutions with the color transitioning from yellow to purple from pH 4-7 in 0.5 unit increments. These particular buffers did not develop very intense colors in the pH 5-6 region. The shades were close but the intensity was not as intense as the color chart. We would expect that the mash has sufficient buffer capacity.
Since the color of the strip remained yellow, that would seem to indicate that the pH was lower than 4.5. If this is not what you would expect we would suggest two things:
1) Try the bleach test described above in item (2) to make sure the strips are reacting like they should. If they do not turn purple, then it is possible that the strips are old.
2) Try a fresh vial of strips.
The 0-200 ppm chlorine test paper (145) performs best in neutral pH solutions (pH 6-8). High pH may slightly suppress the color development resulting in slightly lower results. Acidic waters do not appear to affect the color development.
In this video, we created some example “chambers” to show how the Ammonia Leak Cloth detects ammonia gas leaks or how the Cobalt Chloride moisture detection paper can detect humidity. All of our leak detection products work similarly, and some are even reusable. For example, when the Ammonia Leak Cloth is moved away from the leak, it reverts back to the original golden yellow color and can be reused.
Peracetic acid formulations usually contain acetic acid and hydrogen peroxide to stabilize the peracetic acid. The Precision Laboratories PAA test strips have been developed to determine the peracetic acid level in the presence of acetic acid and hydrogen peroxide.
The standards we use to evaluate the strip performance are prepared from an FMC VigorOx SP-15 concentrate that is about 17% peracetic acid. The actual peracetic acid content of the standards is verified using a drop count test kit.
Both the Chlor-Assure and the Mid-Level Chlorine test strips measure up to 200ppm. Both strips are complimentary to our Chlorine test Papers, although they have a slightly different chemistry. The Chlor-Assure test strips offer a 150ppm color block that the Mid-Level strip does not, however the Mid-Level strip is a bit less expensive.
The Universal pH test paper does undergo some sublimation over time. This is evidenced by the slight discoloration of the color chart and vial. We have found that this sublimation does not normally adversely affect the performance of the test paper.
There are some interferences to consider:
The Phosphate test strip is measuring phosphate (as phosphorous) in ppm. We do not offer a strip that can read as low as ppb.
The Ammonia Leak Detection Cloth is treated with a dilute ethanol solution of bromothymol blue and phenolphthalein (10:1 ratio) and air dried. When dry, the cloth is a yellow-orange color. When exposed to ammonia vapors, the indicator dyes turn the cloth blue/green due to the alkaline nature of the ammonia.
In air, the cloth reverses back to the yellow-orange color as it absorbs CO2 from the air. The carbonic acid lowers the pH and thus the indicator dyes revert back to their acidic color. This reversal can be accelerated if the cloth is placed in an acidic environment (say a vinegar/acetic acid atmosphere.)
Since the ammonia leak detection cloth is simply measuring pH, any interferences present that create an acidic or alkaline environment competing with the effect of any ammonia gas would interact with the cloth.
The dyes are not bound to the cloth with any special binders. They will wash out. They may also discolor materials they contact.
Let’s say you’re testing the free chlorine content of 1% bleach, which has a pH of 11.8. If the pH is reduced to 8, for example, will the colorimetric response of the Extra High Level Chlorine test strip for this 1% bleach change, too? Yes, it does appear that pH will influence the result.
• A 1% (10,000 ppm) hypochlorite standard was prepared from ACS hypochlorite (11.75%). The pH of the 1% solution was 11.5. This was tested with the 0-10,000 Extra High Level Chlorine test strip. The color matched the 10,000 color block very well.
• The pH of the 1% standard was lowered by adding 9 drops of concentrated HCL. The pH was 8.05. The test strip read 7,500 ppm; lower than the non-adjusted solution.
• The pH 8.05, 1% solution was diluted 1:1 with water. Theoretically, this should be 5,000 ppm. When tested with the strips, it read much closer to the 2,500 ppm color block. The pH of the diluted solution was 8.10.
• A 0.1% (1,000 ppm) standard was prepared from the original 1% standard. The pH was 10.3. The test strip results matched the 1,000 ppm color very well.
• The pH of the 1,000 ppm standard was adjusted lower by adding one drop of concentrated HCl. The pH was 8.1. The test strip read lower than 1,000 ppm.
In summary, it appears that lowering the pH to about 8 will depress the chlorine test strip result by about one color block.
The Iron test strips only work on iron ions that are free in solution. They will not detect Iron that is complexed with a chelating agent, such as EDTA. Iron chelates are often used in products such as fertilizer to aid in improving the availability of the iron as a plant nutrient.
Various types of sulfites can be used – sulfite, bisulfite, and metabisulfite. Our original color chart was developed to measure sulfite ions in ppm (from sodium sulfite standards), however, we have checked standards and found that bisulfite and metabisulfite also match the same color chart.
No. The Chlorine Dioxide test strips have an inhibitor that prevents them from reacting with free chlorine. Thus the paper will not react in regular chlorine bleach solutions.
Our chlorine test papers are based on the potassium iodide starch reaction. As such, many oxidizing species will cause the paper to turn purple. The iodide that is impregnated in the paper is oxidized to iodine when exposed to a solution containing an oxidizer. The iodine then complexes with the starch (also impregnated in the paper) and turns the paper blue/purple. The iodide and starch impregnated into the paper are in excess, so that the intensity of the color developed depends on the amount and strength of the oxidizing species.
It is not advisable to use our chlorine test papers to measure chlorine concentrations made with non-regular bleach.
Non-regular bleach will turn the test paper blue/purple, however, the bleach formula contains additives that influence the color development of the strips and also affects the results of the verification methods.
We have tested the blue litmus with multiple pH buffers. The blue paper is blue at pH 8. At pH 7, the sample is maybe just a little red. The real change to red seems to start with pH 6.5 and lower.
All of our Peroxide test strips are suitable for detection of hydroperoxides and ether peroxides. Polymeric peroxides, which can form in diethylether, are not detected. Organic peroxides, such as di-terc-butyl peroxide, di-cumyl peroxide or terc-butyl perbenzoate, either do not react or react with significantly reduced sensitivity.
If you are using the 345 chlorine books to measure chlorine levels, you should use the same chart as the 145 chlorine test papers.
The colors for the 10, 50, 100, 200 ppm chlorine will be the same progressively more purple color. Above 200 ppm the purple will intensify further to the point that it will appear almost black.
At some point – usually above 1000 ppm the strip will actually bleach out and instead of purple it will be white. When this happens some users think that this means they have no available chlorine present when in fact they have too much and it overwhelms the chemistry on the strip. The tell-tale sign of this is the presence of a purple stripe at the sample-paper interface. You can demonstrate this to yourself by dipping a strip in straight bleach.
Yes! It’s called QAC QR5. Dip the test paper into the solution for 1 second, and wait 5-10 seconds before comparing to the color chart.
Yes, the cloths are reversible. As long as the cloth reverts back to the original goldenrod yellow color, it will continue to change when exposed to ammonia vapors. We aren’t certain of how many times it can be reused (it is somewhat dependent on the use). Eventually, it won’t revert back to its original color and can no longer be reused. It works best if exposed to vapors. If you get it wet, it will not be reusable.
An alternative test method for detecting sulfites in red wine would be to add approximately 1 teaspoon of citric acid to a 1 ounce sample of red wine in a small cup. Holding the Sulfite test strip above the solution for 5 minutes will result in the test strip reading the sulfite level.
The citric acid will cause sulfites in the wine to convert to sulfur dioxide gas. The gas will react with the test strip. We have tested some sulfite spiked red wine and found that the amount of sulfite added to spike the sample when reacted with acid correlates with the color chart as a measure of the sulfite in the wine sample. Other acids will work as well, but citric acid is probably the least hazardous choice (hydrochloric acid works well but it is not easily handled).
It is not a good idea to dilute the sample with water. While this helps to avoid the color stain, dilution of the hydrogen ion concentration will change the pH.
A better suggestion for measuring pH might be to use activated carbon (like that used in aquarium filters) to help take the color out of solution sample. This method doesn’t appear to affect the pH of the solution.
Our Wine pH test strips, measuring from 2.8-4.4 work great for testing kombucha tea as well.
The 145 chlorine paper test strips are primarily used for monitoring restaurant and kitchen sanitizing solutions where the target ppm level is between 100-150ppm. These test papers will not work well in pools.
Swimming pool chlorine levels are usually under 10ppm free chlorine. Our CHL-10, 0-10ppm chlorine test strip will work for this application.
In addition to low levels of chlorine, pool testing is complicated by other factors (ex. water quality, biological load issues, etc). For this reason pool strips are usually designed specifically for this application. Check out our 5-pad pool test strips.
Yes, we call it our Salinity Test Strip. This test strip measures the level of chloride present and can be used as an indirect indicator of sodium when the sodium is present due to sodium chloride salt.
If the sodium is due to NaCl and not from other sources, a ppm level of 500 ppm Cl would be equivalent to a ppm level of about 320ppm sodium based on the differences in molecular weight. A 1000ppm chloride result would therefore be about 640ppm sodium.
Theoretically, the color associated with a certain ppm color block will develop when the sample or standard is that exact ppm. If the sample is between two ppm color blocks, the color developed by the strip will be between the colors of those two blocks.
The color is not “fixed” for a certain range or for a given step. The color scale is a gradient that is “fixed” along the way at certain points. It is normal to select points that are at least double the previous ppm value. This allows for variation in paper, reagents, process, etc.
Keep in mind that variation in label print runs, test strips, test methods, etc. can contribute to the colors not being an exact match. We do our best to minimize this but some variation is inevitable.
Our test strips have been calibrated for use with all the commonly used hyamine and steramine quat (quaternary ammonium chloride) solutions. Some commercially available strips have errors as high as 50%. Use this guide to test your strips.
To prepare a 400ppm QAC solution, dilute 0.530ml of Oasis 146 into 100ml of water.
|Active Ingredients||Conc.||Active Ingredients||Conc.|
|Alkyl dimethylbenzyl ammonium chloride||3.00%||Octyldecyl dimethyl ammonium chloride||2.25%|
|di-n-octyl dimethyl ammonium chloride||0.90%||di-n-decyl dimethyl ammonium chloride||1.35%|
Prepare a stock solution by dissolving 1.25g in 100ml of water to produce a 10,000ppm solution. To prepare a 400ppm QAC solution, dilute 4ml of the stock solution into 100ml of water.
|n-Alkyl (C14=50%, C12=40%, C16=10%) dimethylbenzyl ammonium chloride-80%|
Prepare a stock solution by dissolving 1.25g Bardac 2280 in 100ml of water to produce a 10,000ppm solution. To prepare a 400ppm QAC solution, dilute 4ml of the stock solution into 100ml of water.
|Didecyldimethyl ammonium chloride-80%|
Prepare a stock solution by dissolving 2g Bardac 2250 in 100ml of water to produce a 10,000ppm solution. To prepare a 400ppm QAC solution, dilute 4ml of the stock solution into 100ml of water.
|Didecyldimethyl ammonium chloride-50%|
Sysco QAC Tablets
To prepare a 400ppm QAC solution, place 1 tablet into 2.82L (1 US Gal.) of water.
|Alkyl (C14=95%, C12=3%, C16=2%) dimethylbenzyl ammonium chloride-50%|
The accuracy of QAC tests strips does not depend on the pH value of solutions to be tested in the range of 1.86 – 9.2 pH, but rather it depends on buffering capacity. When the pH of a solution to be tested is a result of acidic or alkaline compounds without buffering capacity, then the accuracy of the test is not influenced. In the case that the pH of a solution to be tested is a result of a buffer, then the measure of influence depends on the buffering capacity of the solution.
Sets of control solutions with QAC concentrations 0 – 50 – 100 – 200 – 400 ppm were prepared in following solutions:
- Hydrochloric acid /0.1 M/, pH 1.1
- Tartaric acid /0.1M/ , pH 1.86
- McIlvaine buffers (0.1M citric acid, 0.2 M disodium hydrogen phosphate), pH 2.2 – 3.0 – 4.0 – 5.0 – 6.0 – 7.0 – 8.0 – 9.0
- Sodium tetraborate /0.01M/ , 9.20
The table below contains readings according to the regular color chart:
|pH buffer /b/||0 ppm QAC||50 ppm QAC||100 ppm QAC||200 ppm QAC||400ppm QAC|
|5.0 /b/||≤ 50||100||200||400||≥400|
Testing was run on set of control solutions 0 – 50 – 100 – 200 – 400 ppm Hyamine 1622 (Fluka) warmed up to temperatures in the range 35 – 60oC.
|T (oC)||QAC strips reading in control solutions 0 – 50 – 100 – 200 – 400 ppm|
|35||reading OK in the whole concentration range|
|40||reading OK in the whole concentration range|
|45||0 – 50 – 100 ppm OK, 200 and 400 ppm reading cca half color square higher|
|50||50 – 100 ppm reading cca half color square higher, 200 – 400 ppm reading 1 color square higher|
|55||reading 1 color square higher in the whole range|
|60||reading 1 color square higher in the whole range|
Testing was run on a set of control solutions at 100, 200, 300, and 400 ppm QAC using Oasis 146 stock.
The samples were split, so that one set was kept at room temp (76F) and one set was placed into the refrigerator (38F). Both the paper strips (SKU: 106) and the plastic backed test pads (SKU: QAC-400) were tested. The test papers showed no visual difference at any of the concentrations. The plastic backed strips did not show any visual difference, with the exception of the 100 ppm standard. The refrigerated standard read slightly lower (maybe ¼-½ a color unit, read as 50-75 ppm). The test was repeated several times and these results were confirmed.
The taste test strips exhibit a taste due to a dominant allele on chromosome number seven, and the ability to taste these compounds is present in about 70% of the U.S. population. The ability to taste is due to two different sets of alleles. These compounds are present in various naturally occurring foods, and are selected due to their similarity to bitter alkaloids and cardiac glycosides, used by the plant to reduce browsing by herbivores.
Thus, their presence is a result of natural selection both for the plants which produce them and the animal which benefits from the ability to sense them. It is a benefit to be able to detect them and avoid bitter tasting foods, some of which might be harmful if swallowed. Hence, it is a trait selected for in populations evolving in an area which had/has such plants.
Unlike PTC, which taste bitter if an individual can taste it at all, Sodium Benzoate might taste sweet, salty, or bitter. It would generally taste salty to an individual who can taste the bitterness of PTC.
YES. In the case of the genetics taste test strips, both PTC and Sodium Benzoate are salts of benzoic acid. Any possible toxicity would be in grams per kilogram of body weight, which is millions of times greater than anything which would be found in our taste test strips. Phenylthiocarbamide (PTC) is present at only 3-5 micrograms per strip. At this level, the compound is negligible and harmless.
1. Nutrient broth medium inoculated with Escherichia coli and Staphylococcus aureus and incubated at 37C for 24 hours, “starting cultures”.
2. A standard plate count procedure performed using 24 hour cultures of Escherichia coli and Staphylococcus aureus. Cultures diluted (10-1, 10-2…10-8) in 0.75% saline solution, plated on nutrient agar medium and incubated at 37C for 24 hours. The number of colony forming units (CFU’s) determined and the starting culture bacterial concentration
3. In conjunction with the dilution procedure, 0.1 ml of each diluted bacteria suspension was then applied to a standard microscope slide and allowed to air dry. A Protein test strip pressed onto the air-dried bacteria suspension was then applied to determine the presence of protein.
The Protein test strips were able to detect 1.0 x 10^6 bacteria per ml.
Glucose Apart from glucose, no other compound in urine is known to give a positive reaction. False positive reactions can be produced by a residual of oxidative compounds, from cleansing agents, for example. Larger amounts of vitamin C (e.g. from tablets, antibiotics or fruit juices) can result in lower or false negative results.
Ketones Urine ketone bodies include acetoacetic acid, acetone and beta-hydroxybutyric acid, and they are produced exclusively in the liver. Ketones in the urine signalize an abnormal carbohydrate metabolism.
Beta-hydroxybutyric acid is not detected, as it is not a ketone. Phenylketones in higher concentrations interfere with the test by producing variable colors. Phthalein compounds interfere by forming a red color.
Protein The Protein test pad contains changes color in the presence of albumin. Other urine proteins are indicated with less sensitivity (e.g. globulins, mukoproteins, hemoglobin, Bence-Jones protein).
The protein test is not influenced by the urine physiological range of pH values, but in strongly alkaline urine (pH >8) or in urines with extremely high buffering capacity, the test can provide false positive results. In addition, the presence of polyvinylpyrrolidone (blood substitute), quinine or the disinfectants residue (quat-based) can lead to false positive results. The residues of disinfectants on the base of nonionic or anionic detergents can also cause false negative results.
pH The pH value of fresh urine from healthy individuals varies from a pH of 5 and 6 to a pH of 8, depending on the individual’s food intake. Prevalence of meat products in the diet lead to a more acidic pH level, while a lacto-vegetable diet causes more alkaline urine with a pH greater than 7. Any inorganic acidic or alkaline substances presented in urine can interfere with the test.
These test strips are selective for glucose. You will not get a reaction with soft drinks or regular sugar, as they primarily contain fructose or sucrose. In solutions containing oxidizers (for example, iodine solutions in diffusion/osmosis experiments), a false blank may be observed.
The Ascorbic Acid test strip is based on discoloration of blue red-ox indicator, depending on the concentration of ascorbic acid. The Ascorbic Acid test strip is calibrated from 0.01% (10 mg/100 ml) to 0.1% (100 mg/100 ml). Red-ox indicator is also sensitive to acidic compounds, and its blue color turns to purple in the presence of acids.
The Vitamin C strips are buffered to a certain extent to keep the blue color of the pad, but in the presence of strong acids, contained in some fruits or juices, the color can turn to a purple-pink instead of a blue-white. In such cases, we recommend using a special color chart (See “Ascorbic Acid Color Changes” chart below) which shows results for Vitamin C in the presence of different concentrations of citric acid. Lemons and limes contain the highest amount of citric acid at about 5 percent. Grapefruits and oranges also have high content of citric acid at about 2.5 and 2 percent, respectively.
In the “Ascorbic Acid Color Changes” chart (click button below), the values are as follows:
Low = 0.5%; Medium = 1%; High = 5%
Hardness is mostly expressed in ppm (mg/l as CaCO3) or in German degrees (°d). There are also other units used for the expression of hardness, and the conversions are presented below.
The reaction of the Fluoride test strip is very dependent upon the acidity level of the solution to be tested. Before testing, the solution has to be acidified to a pH ≤ 0.5. For acidification, we recommend hydrochloric acid (muriatic acid), preferably concentrated (1-2-3 M) depending on the rough presumption of the fluoride concentration in the test sample because in the process of acidification, the solution is always more or less diluted with added HCl (dilution has to be noted and the result is then multiplied with the dilution factor).
For example, 1M HCl has pH about 0.1
0.1M HCl has pH about 1.09
If a high concentration of fluoride is predicted in the sample to be tested, then 1M HCl can be used for acidification, added to the sample in the ratio, 2 parts of 1M HCl and 1 part sample, meaning the sample is 3 times diluted and the result must be multiplied by 3. For example, if the result is read by comparing the test pad with the color chart at about 10ppm, then the actual result is 10 x 3 = 30ppm.
If a lower concentration of fluoride is predicted in the sample to be tested, then more concentrated HCl should be used to avoid a higher dilution than necessary. The final pH of the sample before testing should be between 0 and 0.5. After acidifying the solution, the test strips are easy to use. Simply dip the strip into the pH adjusted solution for one second, remove, and compare the strip to the included color chart after 10 seconds.
Hydrochloric Acid (muriatic acid) should be available at a local hardware or pool/spa store, as well as at any chemical supply distributors, such as Fisher Scientific or VWR.
The solution to be tested must be at a pH of 0.5 in order for this test to be accurate. This pH measure can be accomplished using concentrated Hydrochloric acid (muriatic acid) to acidify the test solution, and measured with the pH 0-1.5 test strip.
Hydrochloric acid should be available at a local hardware store or pool/spa store, as well as at any chemical supply distributors, such as Fisher Scientific or VWR.
Monitoring the pH of the Mash, Wort, and Beer is necessary as the Yeast will develop differing physiological states, and the presence or absence of Organic Acids and the use of mineral Ions during the fermentation process will cause changes in acidity or alkalinity. This in turn affects Enzyme activity in the Yeast.
Prior to, and during the process of fermentation, a measure of the pH of the solution is quite important. The correct pH must be established initially, and should be monitored throughout the process in order to facilitate the complete breakdown of the initial carbohydrates to alcohol. This measure of pH may be accomplished with the Universal pH test paper. In addition, the pH 1-14 test strips can be used to test the acidity (pH) of the juice/must/beer prior to and during the process of fermentation. For an initial measure of the pH of the mash for beer, a narrow range measure can be obtained using the pH 4.6-6.2 test strips.
The pH of Yeast is best at 5.2-5.5. Malted Barley will release Phosphate Ions, and these will cause the water to be buffered at a pH of 5.6. Attaining an optimum pH range will ensure more complete conversion of starches in grain to fermentable sugars. In addition proper hop utilization will occur.
Typically, only two of the three pads changes color at any given pH level, which you match with the closest three blocks on the color chart. Changes can be subtle, and the colors may appear different under different lighting conditions (fluorescent, incandescent or sunlight). Three-pad pH test strips can provide for the most accurate results.
Prior to, and during the process of fermentation, a measure of the pH of the solution is quite important. The correct pH must be established initially, and should be monitored throughout the process in order to facilitate the complete breakdown of the initial carbohydrates to alcohol. This measure of pH may be accomplished with the Universal pH test paper. In addition, the pH 1-14 test strips can be used to test the acidity (pH) of the juice/must/beer prior to and during the process of fermentation. For an initial measure of the pH of juice, a narrow range measure for wine production can be obtained using the pH 2.8-4.4 test strips.
The pH test strips and papers are based on acidobasic indicators, which change their colors in a particular pH range. Acidobasic indicators are generally very stable compounds, and we have chosen the best indicators based on their properties for use in our test strips. They are so stable that special packaging (such as air-tight stoppers, unpermeable material for packing, dessicant, etc) is not necessary.
When stored, keep the strips out of direct sunlight. Sunlight can fade the color with time, like any other colored materials exposed to light for too long. The biggest issue in this situation is fading (bleaching) of the color scale on the label, which serves as a calibration for pH reading. Fading of the color scale on the label can occur faster than the fading of strips themselves.
Similarly, exposure to high humidity for a long period of time can also cause changes in the color reaction system. When the moisture dries on the paper, it causes fading or color changes.
Generally, the minimum expiration date for pH test strips and papers is 3 years when stored at 10 – 30C in a dry place, away from chemical fumes in laboratories.
We have several different packaging options, including:
- Clear resealable bags
- Amber resealable bags (light protection)
- Foil bags (light and humidity protection)
- Clear vials
- White flip-top vials (light and moisture protection)
- Amber bottles (light protection)
Some of our test strips are light sensitive or humidity sensitive and must be stored in more protective packaging than other strips. Our goal is to aim for at least 2 years stability from the date of manufacture, and this goal helps us determine the most appropriate packaging for each test strip.
Development time for test strips is dependent upon many factors. The kinetics of the color development are manipulated by altering the formula employed on the test pad, along with adjusting the conditions of the test (dip time, swirl versus dip, shake excess water off versus no shake, etc.) to offer the best color separation in the shortest time possible.
In the case of the different chlorine test strips, while the color developing indicator is the same, the formulas have been adjusted to slow the development of the color allowing the range of the test strip to be expanded to accommodate the higher chlorine values.
Specifying a specific development time is normally very important. The nature of these test strips is that the color continues to change over time. It is not like a titration with a definite endpoint. Reading the result before or after the specified development time will result in inaccurate results, just like under or over-titrating a sample would.
Our goal is to provide the best color separation at the values requested in the shortest time possible. We try to standardize this whenever we can, however, user requirements often require specific and unique instructions.
The Hydrion QAC test strips are reddish-orange in color before use. Our QAC test strips are yellow in color before use.
Instructions for the Hydrion QAC test strips tell you to dip the strip into solution for 10 seconds and then read immediately. This 10 second development time (soaking) is important. With the 10 second wait, the color of a 200 and 400 ppm standard matches the Hydrion color chart fairly well.
If the user takes the strip out too soon the color shifts significantly lower. For example, if dipped in a 400ppm solution, the strip stays brown, which looks more like 200ppm.
Our QAC test strips have different instructions for use. The strip should be dipped into solution for 1-2 seconds, then compared to the color chart immediately. Again, the time is important.
If the user waits too long, the strips will turn more blue, as if it’s actually beyond the 400ppm value on the color chart.
Our QAC test strips were developed to work best for multi-quats. The standards we use are from a brand called OASIS 146 which consists of:
• Alkyl dimethylbenzyl ammonium chloride …… 3.00%
• Octyldecyldimethyl ammonium chloride …….. 2.25%
• Di-n-octyldimethyl ammonium chloride ………. 0.90%
• Di-n-decyldimethyl ammonium chloride …….. 1.35%
Different quat formulas require adjustments to the color chart. Some even require custom charts.
When testing RO, distilled, or tap water, the strips may not behave like you would expect. The colors on the chart were developed for these strips using buffer solutions. The indicators used with the strips require that the waters being tested have some buffering capacity. RO and distilled waters have little or no buffering capacity, and the test strips will not work in these waters. If the tap water has a very low buffer capacity (low hardness, low alkalinity, etc.) the color can take much longer than the recommended 1-2 second immersion and 10-15 development time.
Sodium chloride salt is not an oxidizer and will not react with any of our chlorine strips.
However, if you are using salt in pools as a source of chlorine, and your question is, “Can I use chlorine test strips in a salt water pool?”, the answer is yes. In this instance, you must use a chlorine test strip with the correct range, such as the Residual Chlorine 0-5ppm or Low Level Chlorine 0-10ppm test strips.
Salt is used to introduce chlorine to the water (no reaction to strips) but the salt generator or electrolysis unit takes the salt water and converts it to hypochlorous acid and sodium hypochlorite. It is the hypochlorius acid and hypochlorite ions that are commonly referred to as “available chlorine.” Hypochlorous acid is a strong oxidizer and will react with any of the chlorine strips.
Chlorine dioxide is less reactive than chlorine or ozone, which means lower concentrations of chlorine dioxide can be used to achieve effective disinfection. It can also be used when large amounts of organic matter are present.
Other advantages include:
- Its bacterial efficiency is unaffected by pH values between 4-10 units
- It has a lower contact time
- It does not react with ammonia
- It has no distinct smell
- It also provides excellent results in the destruction of spores, viruses, bacteria and other pathogens.
Chlorine bleach at concentrations of at least 1000ppm is an effective germicide for dangerous pathogens such as MRSA (Methicillin Resistant Staphylococcus aureus), VRE (Vancomycin Resistent Enterococci) and Clostridium difficile. The High Level Chlorine ( 0-1,000ppm) test strip is suitable for use with Deardorff-Fitzsimmons ACTIVATE disinfectant (5.25% Sodium Hypochlorite solution) for in vitro control of such dangerous pathogens.
However, the removal of free chlorine by organic contamination (blood/feces) can seriously reduce the sanitizing effects of chlorine cleaning solutions. To ensure the 1000ppm minimum strength for adequate disinfection, much higher initial concentrations, up to 10,000ppm (1%) chlorine levels are recommended to counteract this and can be check with our Extra High Level Chlorine (0-10,000ppm) test strip.
According to the EPA (Environmental Protection Agency), the following are standard definitions of clean, sanitize, and disinfect:
Clean – The process that physically removes debris from the surface or area by scrubbing, washing, and rinsing. It may be accomplished with soap or detergent and water.
Sanitize – A product that kills 99.9% of germs identified on its label. Sanitizers are used to reduce, but not necessarily eliminate microorganisms from the inanimate environment levels considered safe as determined by public health codes or regulations.
Disinfect – A product that kills nearly 100% of germs identified on its label. Disinfectants are used on hard inanimate surfaces and objects to destroy or irreversibly inactivate infectious fungi and bacteria, but not necessarily their spores. There are two major types of disinfectants: hospital and general use. Hospital disinfectants are the most critical to infection control while general disinfectants are typically used in households, swimming pools, and water purifiers.
The EPA lists more specific and technical details regarding the guidelines for sanitizers and disinfectants, but they go into far more detail than users generally need.
To determine the recommended bleach concentration for your application, locate the EPA registration number on your product label. Visit the EPA’s website, and enter the EPA Registration Number, then click Search. You should see the details about the product, and beneath that, a PDF bearing the date that this product was registered by the EPA (if there is a list, the PDF at the top of the list should show the most recent approval). Click on that most recently-approved PDF. The PDF should come up on your screen. Scroll down to the section that shows the directions for using the product as a sanitizer or disinfectant. Follow the directions listed for your intended use.
Each printing of color charts is preceded by an extensive review of the test strip performance. Chlorine standards are generated at 10, 50, 100, and 200ppm. These values are confirmed by at least one independent test method. Using these verified standards, samples of strips from several different production runs are used to determine the color associated with each standard value. Once the colors are selected, the color charts are printed. Prior to their use, the color charts are again checked with a fresh set of verified standards. After acceptance of the color charts, subsequent production runs of test papers are checked against the charts before they are packaged for sale.
Temperature will slightly affect the performance. The 145 chlorine test papers (0-200ppm) have been checked in solutions up to 70°C (158°F). At temperatures above 50°C, a 10ppm solution will not develop as much color as it should, resulting in a reading lower than expected. Solutions of 50, 100, and 200ppm chlorine appear to be influenced less. For practical purposes, solutions greater than 50ppm are not noticeably influenced by temperature.
Chlorine is one of the most popular chemicals for cleaning, sanitizing, and disinfecting. Two common examples will help illustrate this. Swimming pools are often treated with chlorine chemicals. In this application, the amount of chlorine needed is low, typically only 1-3ppm chlorine. On the other hand, disinfection of daycare and hospital facilities requires a much higher chlorine level, typically 600-1200ppm. In both examples, the 0-200ppm chlorine test paper is not the best choice. Precision Laboratories manufactures a whole range of chlorine test strips. Please consult our product listing for the chlorine test strip that best matches your application.
There are many online calculators that can help with this. A general rule of thumb is that 1 tablespoon of bleach in 1 gallon of water will yield a solution that is approximately 200 ppm in available chlorine. It is important to note that this is true if the starting bleach is normal bleach (5.25% sodium hypochlorite which is equivalent to 5% available chlorine). Today, bleach is often sold in concentrated form (8.25% sodium hypochlorite which is equivalent to 7.85% available chlorine). It is best to check the label. Another consideration is the age of the bleach. Bleach will lose potency over time, especially if the bottle has been opened several times.
The chlorine test paper will darken over time, so it is best to compare the color as directed (immediately after dipping into solution). Also, be aware that if two strips are stuck together, the color of the paper will be darker. Lastly, be careful not the lay the strip against the vial when comparing to the color chart, as this will also intensify the color. The chart provided was created holding the strip in the air next to the vial.
All available chlorine has some biocide strength, although hypochlorous acid is a far stronger biocide than hypochlorite ion or the chloramines. In solutions at pH of 5-7, hypochlorous acid is the most prevalent species. For this reason, most sanitizing solutions will work best in the neutral to slightly acidic pH range.
When chlorine gas (Cl2) or bleach (sodium hypochlorite or NaOCl) is added to water the result is the formation of hypochlorous acid (HClO).
Cl2 + H2O -> HOCl + H+ + Cl-
NaOCl +H2O -> HOCl + Na+ + OH-
Depending on the pH of the solution the hypochlorous acid exists in solution as either hypochlorous acid (HClO) or hypochlorite ion (OCl-).
HOCl < = > OCl- + H+
Free available chlorine refers to the amount of hypochlorous acid AND hypochlorite ions present.
Combined (or bound) available chlorine arises when nitrogen (usually in the form of ammonia) is present to form what are called chloramines (mono-, di-, and trichloramines are possible).
Total available chlorine is the sum of the free available chlorine and the combined available chlorine.
The full surface area of the agar (10 square centimeters) should be covered.
There are two techniques for sampling viscous fluids.
1. Measure a 1mL sample using a sterile graduated cylinder.
2. Either pipette or carefully pour (using aseptic technique) the sample onto the paddle. Tilt the paddle at a 15-degree angle, allowing the sample to flow by first impacting the “top” of the paddle, then flowing down towards the “bottom” (opposite side) of the paddle. A Thinly-applied film should be made. The surface area of paddle is approximately 10 square centimeters.
3. Insert the paddle back into the vial and incubate in an UPRIGHT position. (There should not be sample dripping downward, but even so, it should not harm the agar growing surface.)
4. Counts are expressed as CFU/cm3.
1. Use a sterile cotton swab (or other sterile transfer device such as a loop) to collect material to be sampled.
2a. Non-Quantitative Application: Apply sample to agar paddle surface as a thin film using aseptic technique.
2b. Quantitative Application: A known amount (1mL) of sample is aseptically applied to the top edge of the paddle, then spread using a loop (or similar spatula-type device) over the remaining 10 square centimeter paddle surface.
3. Insert the paddle back into the vial and incubate in an UPRIGHT position.
4. Counts are expressed as CFU/cm3 (when a 1mL sample is applied).
No, you need to “swab” the agar surface with the sample. Growth should include HPC (heterotrophic plate counts), as well as coliform counts.
Yes. Nutrient-TTC (NUT), Tryptic Soy (TSA), and MacConkey (MAC) agars can all be used for marine waters. Testing is essentially identical as for freshwater.
If you are incubating at room temperature, we recommend an incubation period of 36 hours. If you are incubating at 86-90 degrees Fahrenheit (30 degrees Celsius), we recommend an incubation period of 24 hours. It is acceptable to incubate Microslides for 48 hours or more, however, keep in mind that the longer the Microslides are left to incubate, the larger the colonies may appear on the agar surface. When large numbers of microorganisms are present, an extended incubation period may result in Microslides that are difficult to interpret due to confluent growth.
No, the Microslide is not acceptable to use.
Although you should determine what is an acceptable level of bacteria for your unique system, a general guide would be less than 105-106 CFU/ml for cooling water and less than 106-107 CFU/ml for metalworking fluid.
A color change is a result of a microbial-induced pH change in the media.
It could also be the result of a chemical reaction. The TTC dye that is added to Nutrient-TTC turns colonies red in color, and this dye reacts when the sugar in the media is broken down. If the color change is due to a chemical reaction, it should happen within the first 15-30 minutes and no colonies would be visible on the Microslide surface within that time period.
The print on a Microslide vial is as follows: XXX/XXX BBE: YY-MM-DD XXXXXX. Where XXX/XXX is the media on side one /side two of the paddle, BBE is the expiration date, and the last set of numbers is the batch number. Side one of the paddle is marked by a laser indentation line on the tip of the paddle.
The shelf-life of Microslides is 6-9 months if properly stored. Store out of direct sunlight at room temperature (do no refrigerate).
No. Microslides can be set out at room temperature, or placed in a warm area such as the top of a refrigerator to “incubate”. Growth will still develop if Microslides are not incubated, it will simply take more time (at least 48 hours). Yogurt incubators or bottle warmers can also be used to speed up growth.
Currently, our pH test strips are designed for testing buffered solutions, and the calibrations (color charts) are made on buffers against a pH-meter measurement. For non- or low-buffered solutions, these strips are not suitable. For this purpose, there are special pH test pads designed for low-ionic and low-buffered waters, such as water in aquariums or pools. Please see our Aquarium and Pool test strips.
Test strips should be stored in closed vials/bags,in a cool, dry place out of direct sunlight.
The ideal condition is 25C (77F). A range of 20C (68F) – 30C (86F) is acceptable. Test strips should not be stored in a refrigerator or freezer. Test Strips should not be stored where they can be exposed to heat (for example, inside a vehicle or shed).
In some cases, our test strips are packaged in a flip-top vial which has a desiccant liner included to prevent moisture from reacting with the test strips prior to use. This desiccant liner provides a very dry environment inside when closed. The capacity of the liner is sufficient to last over 5 years of opening and closing, as long as it is closed promptly when not in use. Leaving the vial open will shorten the shelf-life of the desiccant liner. Be careful not to introduce moisture into the vial with wet fingers.
Many of our test strips have a minimum shelf-life of 2 years when stored and handled correctly. In reality, the strips are stable for much longer. We have experienced test strips over 3 years old that still perform to specification.
We suggest the test strips be used within one year from the date of opening, given proper storage and handling.
If you believe that the solution you are using contains chlorine and yet after testing it with chlorine test paper, the strip is still white, you may be seeing what is referred to as the “bleaching out effect.” At high concentrations of bleach, the available chlorine will overwhelm the indicators used in the strips. If this happens, instead of developing a purple color, the strip will very quickly turn to white. The best indicator of this effect is the presence of a thin blue line on the strip separating the wet portion from the dry portion of the strip.
Testing should be done at least once daily in smaller restaurants, and more frequently in busy establishments as each time the rinse solution is used, it will get slightly diluted.
Unless otherwise stated, Precision Laboratories test strips have a shelf-life of two years from the date of purchase when stored properly.
No. Litmus papers are qualitative strips, meaning they employ a color change, not a specific color chart, to indicate whether a water sample is acidic, basic or neutral. The specific pH value is not determined.
This depends upon your local health code. In many areas, the level is 50-100ppm available chlorine. It is best to check with your local health inspector for the level required in your area. Federal regulations (21 CFR Part 178) permit the use of hypochlorite solutions on food processing equipment and contact areas (tables) but state that solutions used for sanitizing equipment not exceed 200ppm available chlorine. If higher concentrations are used, a final rinse in potable water is required.