Indigo® quaternary ammonium compound test strips confirm optimal dilutions for disinfection & sanitizing in restaurants, hospitals, organic farming & more.
All come with 100 test strips/vial and a guaranteed 3 year minimum shelf life. Certificates of Analysis, Stability & SDS Statements are on-line; Certificates of Conformance available on request.
Buy Indigo® test strips, the brand you can trust for accuracy & technical support. Call us on our toll-free line for immediate assistance or e-mail us with your questions. 1 hour response is typical during business hours, M-F, slightly longer on weekends. Optional next business day delivery in any quantity of most items.
Quats are effective germ-killers and a key ingredient in many cleaning, disinfection & infection control products. They are found in every day products such as household toilet cleaners, antibacterial hand soaps, dish washing liquids, baby wipes, body washes, disinfectant sprays & more.
Quats are especially effective on hard, non-porous environmental surfaces. They are used in hospitals, long-term care facilities, households & food processing plants to name a few.
Quaternary ammonium compounds (quaternary ammonium salts) are cationic biocides (positively charged surface-active agents) that are more chemically complex than other disinfectants. Their name derives from the central nitrogen (quaternary ammonia) that is bound to four organic groups. They interfere with the metabolism of Gram-negative & Gram-positive vegetative bacteria and lipophilic viruses.
They have several advantages in the fight against antimicrobial resistance. Unlike antibiotics, disinfectants like quats are non-specific in their targeting of microorganisms. Their amphiphilic nature (having both hydrophobic & hydrophilic properties) allows for enhanced binding affinity that can disrupt bacterial cell membranes causing cell lysis.
(See More Info below to compare quat chemical structures.)
Whatever formulation of quaternary ammonium you use, Indigo® quat test strips can confirm your disinfectant solutions are correctly diluted for optimum effectiveness.
Note: All test strips Made in the USA & are Q/A'd against NIST standards.
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Buying your quats in concentrated form is cheaper than pre-diluted. BUT, knowing how to dilute them may not be obvious. Read this section in our blog: How to Dilute Quats.
Quat test strips do not measure the concentration of dissolved quaternary ammonium compounds (QACs) directly. They actually use acidobasic indicators (normally used for pH determination), buffers, surfactants, and other ingredients to create a micro-environment on the test pad where the indicator dyes react to the presence of the quat and not to the pH of the test solution. It is as a consequence of the interaction between the molecules of the indicator dyes and quat that results in a different color of the test pad that we observe.
This is based on what is known as the "pH indicator error" (when the indicators change color without a change in solution pH) which relies on a carefully calculated amount of buffer on the test strip that excludes any contribution to pH other than the quat itself. It is this "error" that is utilized for the detection of compounds of interest (The QACs in this case). In other words, the assumption is the quat has been dissolved in tap water that might be slightly acidic, neutral or slightly alkaline. "Alkaline water" for example would have absolutely no effect. However, some quat formulations have additives such as tetrasodium EDTA which strongly shifts pH towards an alkaline level of 11-12 that completely throws off the test strip reading.
Overall, this is a reliable semi quantitative test method that is accurate typically to +/- 10% & suitable for confirming the correct dilution of quat concentrates in the "field". For more precise lab work, instruments such as GC/MS can deliver quantitative results on the order of several magnitudes greater & over a wider dynamic range.
35oC: Readings ok for 0-400ppm
40oC: Readings ok for 0-400ppm
45oC: 0, 50, 100 ppm readings ok; 200 & 400 ppm read~ 1/2 color square higher
50oC: 50, 100 ppm read~ 1/2 color square higher; 200, 400 ppm read 1 color square higher
55oC: Readings 1 color square higher across whole range
60oC: Readings 1 color square higher across whole range
Follow the directions on the label. All our quat strips are "quick response". Dip the strip & compare to the color chart within 5-10 seconds. If you wait a minute as with other strips, the color will develop further & give a false high reading.
Some sources have raised concerns about the safety of quaternary ammonium compounds. Handling concentrated QACs may merit wearing PPC such as gloves, eye protection and even a respirator.