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.
The peracetic acid test strips were developed for use in peracetic acid liquid preparations, not for peracetic acid generated using powders employing the “oxygen bleaching agent” approach.
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. 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.
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.
The Chlorine Dioxide 0-500 test strips will react to free chlorine solutions, in fact this is how we check the color chart. Only the Low Level Chlorine Dioxide 0-10ppm has an inhibitor for free chlorine. The Chlorine Dioxide 0-10ppm test strips include an inhibitor for free chlorine up to 4 ppm free chlorine.
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.
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.
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 – 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 |
Lower temps:
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 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 |
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.
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 commercially available concentrates that is about 15-18% peracetic acid. The actual peracetic acid content of the standards is verified using a drop count test kit.
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.
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.
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.
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.
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.
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.
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.
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.
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 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 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.
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.
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 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.
If you are using the 345 chlorine books to measure chlorine levels, you should use the same chart as the 145 chlorine test papers.
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.
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.
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.
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.
A health inspector using QT-40 test strips compared their results to a customer using our QAC QR5 test strips, and the results were the same. The strips, however, are different in color and appearance. So, what is the difference?
Our QAC QR5 uses a different formula from the other strips, but should react about the same. We calibrate our colors using an industry leader Quat formula and in most cases, but not all, the strips will work with chemicals that are similar.
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.
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.
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.
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.
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.
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.
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.