Quaternary Ammonium Disinfectant Compounds

Quaternary Ammonium Compound Test Strips

For disinfection & sanitizing in restaurants, hospitals, organic farming & more

Quaternary Ammonium Compound Test Strips

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.

Overview of Quaternary Ammonium Disinfection Compounds

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.)

Quaternary ammonium compound chemical structure

Quaternary ammonium compound disinfectant structure model from Indigo® Instruments.


Whatever formulation of quaternary ammonium you use, Indigo® quat test strips can confirm your disinfectant solutions are correctly diluted for optimum effectiveness.

Indigo® Quat/QAC Test Strip Ranges

  • 10-100ppm: ≤10-20-30-50-100ppm; read results in 10 seconds
  • 0-400ppm: 0-100-200-300-400ppm; read results in 10 seconds
  • 0-1500ppm: 0-200-400-750-1000ppm; read results in 5 seconds
  • 0-10000ppm: 0-1000-2500-5000-10000ppm; read results in 5 second

Common Features of Indigo® QAC Test Strips

  • clear instructions with the labeled color chart
  • indicators on high contrast plastic for accurate readings
  • stiff plastic strips can be dipped into tubes
  • accurate from 5-45oC (50-110oF)
  • 3 year guaranteed shelf life
  • Certificate of Analysis & Stability Statement online; SDS & Certificate of Conformance on request.

Note: All test strips Made in the USA & are Q/A'd against NIST standards.

Displaying 1 to 4 (of 4 products)
QAC QR Test Strips 0-400 ppm

QAC QR Test Strips 0-400 ppm

SKU: 33819-400
$8.95USD or lower Each
Quat Sanitizer Test Strips-High Level 1500ppm

Quat Sanitizer Test Strips-High Level 1500ppm

SKU: 33819-1500
$13.95USD or lower Each
Quat Test Strips Very High Level 10000ppm

Quat Test Strips Very High Level 10000ppm

SKU: 33819-10K
$16.95USD or lower Each
Residual Quat 10-100 ppm

Residual Quat 10-100 ppm

SKU: 33819-100
$13.95USD or lower Each
More Information

Quaternary Ammonium Disinfection Compound Chemical Structures

Quaternary ammonium compounds are cationic surfactants (positively charged surface-active agents) that are more chemically complex than other disinfectants. Their name derives from the central nitrogen that is bound to four (quaternary) organic groups.

Click on any of the quats listed below to view the structural variability that contributes to their diverse biological & antibacterial activity. Differences in aromatic & alkyl side groups & aliphatic chain lengths effect bactericidal activity with otherwise antibiotic resistant bacteria.

Indigo&ref; QAC test strips are calibrated for Oasis 146 but can accurately test any single or multi-quat based disinfectant. Many vary only in the length of their alkyl chains. Chemistry, microbiology & pharmacology instructors & researchers may find our 3D Molecular Model Builder useful in comparing the following:
  1. benzalkonium chloride
  2. benzethonium chloride
  3. cetalkonium chloride
  4. cetylpyridinium chloride
  5. cetrimonium
  6. cetrimide
  7. diisobutylphenoxyethoxyethyl dimethyl benzyl ammonium chloride
  8. tetraethylammonium bromide
  9. didecyldimethylammonium chloride
  10. ipratropium bromide

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.

Advantages & Disadvantages


  • Nontoxic, odorless, colorless, noncorrosive, nonirritating
  • Relatively stable in the presence of organic matter
  • Active over a wide pH range but best in the range of pH 8-11


  • Slower at killing some microorganisms
  • Not compatible with some detergents
  • Not compatible with hard water
  • Color charts start to deviate at 45oC (110oF) & above

Additional material that may interest you:
  1. Quaternary Ammonium Compounds-Organic Disinfectants. What are quats, how do they work & how to dilute?
  2. Test Strip Expiration Dates; Good Today, Dead Tomorrow? Don't toss good test strips away. Good today doesn't mean bad tomorrow.
  3. Diluting Chlorine, Peroxide, Quats is Easy. Understanding metric makes it very easy to dilute disinfectant to any ppm from bottles to bucketfuls.
  4. Can 10ppm of Sulfite & Quat Really Mean Zero? Test strips can detect residual QACs down to 10ppm which is considered safe.

How Quat Test Strips Work

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.

Temperature and QAC Strips PPM Reading Relationship

(Results for Hyamine 1622 (Fluka) warmed up from 35oC to 60oC (95-140oF))

T (oC)  vs QAC strips readings at: 0; 50; 100; 200; 400 ppm

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.