Quick Response QAC Test Strip

Precision Laboratories QAC test papers and strips utilize an effect commonly referred to as the “protein-error of indicators” to quantify the QAC ppm levels. While first observed with proteins (thus the name), the technique utilizes pH indicators and buffering systems to create an environment where the test paper or strip reacts (develops color) proportional to the amount of analyte (QAC) present. The PL QAC test papers and strips have color charts calibrated to solutions prepared from OASIS 146, an industry standard QAC product. The performance of the papers and strips with alternate QAC products should always be verified. In addition, any additives should be evaluated to see if they contribute to the “protein-error” effect.

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.

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.

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.

Oasis 146
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%

 

Hyamine 3500-80%
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.

Active Ingredients

n-Alkyl (C14=50%, C12=40%, C16=10%) dimethylbenzyl ammonium chloride-80%

 

Bardac 2280
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.

Active Ingredients

Didecyldimethyl ammonium chloride-80%

 

Bardac 2250
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.

Active Ingredients

Didecyldimethyl ammonium chloride-50%

 

Sysco QAC Tablets
To prepare a 400ppm QAC solution, place 1 tablet into 2.82L (1 US Gal.) of water.

Active Ingredients

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.

Test:
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
1.1	0	0	0	≤50	50
1.86	0	50	100	200	400
2.2  /b/	0	0-50	50	100	200
3.0  /b/	0	50	100	200	400
4.0  /b/	0	50	100	200	400
5.0  /b/	≤ 50	100	200	400	≥400
6.0  /b/	50	200	400	higher	higher
7.0  /b/	100	400	≥400	higher	higher
8.0  /b/	200	400	higher	higher	higher
9.0  /b/	400	higher	higher	higher	higher
9.2	0	50	100	200	400

Higher temps:

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 – 60^oC.