Frequently Asked Questions



Custom tests
Instructions and
SDS (Safety Data Sheets)

Sample pH
Applications Definitions Instrument calibration Sample volume
COD Development time Instrument compatibility Shelf life
Color match Dilutions Number of tests per kit Soil analysis
Competition Disposal Range Standards
Conversions EPA Acceptance Sample color Titret usage


Q) What is the accuracy of the CHEMetrics test kits?

A) The accuracy of CHEMets, ULR CHEMets® and VACUettes® test kits is ± 1 color standard increment.

The accuracy of the Titrets® test kits varies with the analyte concentration because the Titret® ampoules have a non-linear scale.  At twice the minimum concentration for a particular kit range, with the exception of the Carbon Dioxide Titret kit catalog No. K-1910, the accuracy is ± 10% error.  For K-1910, the accuracy is ±30% at twice the minimum concentration.

To obtain information about the accuracy of a particular CHEMetrics® Instrumental Test Kit, click on the "Accuracy Information" link on the individual product page on this website.

CHEMetrics can provide a Certificate of Conformance that certifies the analytical performance of these water analysis products.


Q) What parameters do I need to test for in my specific industry?

A) The required testing parameters vary widely within specific industries. However, CHEMetrics has identified the most often tested parameters in several major industries. The information is available through CHEMetrics' Technical Services department. (See Applications.)

Q) Will CHEMetrics develop or customize a test kit for my specific application?

A) New CHEMetrics products often originate directly from customer requests for streamlined testing methods. To be considered for a custom product, the test should be run frequently, or it should be a procedure that is performed widely in the industry. Contact CHEMetrics' Technical Service Department for more information regarding customized kits or chemistries. 


Q) When can I use the mercury-free COD test kits? Are the mercury-free reagents EPA approved?

A) The mercury-free reagent is designed for use with samples that contain low levels of chloride. If your sample has less than approximately 100 ppm of chloride (less than approximately 1000 ppm for 0-15,000 ppm test range), the mercury-free test is applicable. If your samples contain higher concentrations of chloride, the mercury-containing test is required. The mercury-free reagents are not approved by the EPA for reporting purposes.

Q) I compared my COD test results to (Competitor) and they did not correspond.

A) If comparing product from two vendors, keep in mind that the accuracy of ALL COD vials commercially available is +/- 5%. Therefore, a difference of as much as 10% could result when comparing various product sources. For this reason CHEMetrics highly recommends that comparison data be generated with COD Standard solutions.

Data generated using COD standard solutions are dependable and should remove any bias associated with the comparative analyses of samples. In addition, ALL COD vials, commercially available, can produce varying test results if the instrumentation is not zeroed correctly. It is imperative that when zeroing the instrument, the reagent blank is from the same manufacturing lot. For example, if running Hach vials and CHEMetrics vials, it would be necessary to run a blank from the CHEMetrics lot and a blank from the Hach lot. The instrument would have to be re-zeroed when switching between lots (or vendors).

Q) Can I use CHEMetrics COD vials in my Hach instrument?

A) Because CHEMetrics COD kits are equivalent to Hach's, any instrument that can accept Hach's 16 mm COD vials (Reactor Digestion method) can accept CHEMetrics COD vials. Furthermore, CHEMetrics vials may be used with Hach’s factory-programmed COD calibrations. (No endorsement by Hach Company is implied or intended). 

Note: LED photometers do not produce accuracy and precision equivalent to that attainable with spectrophotometers. The use of LED instrumentation is not recommended for COD measurements which will be used for NPDES reporting. 

Color Match:

Q) The color match between my test ampoule and the color standards is poor. Why?

A) This condition may be influenced by the light source, background color of the sample and/or a chemical interference. To obtain the best color match, the light source should be fluorescent. The sample background color issue is addressed under the “Sample Color” heading. If a chemical interference is suspected, see the “Dilutions” heading or contact CHEMetrics' Technical Service department for assistance. 


Q) How do CHEMetrics products compare to HACH and other traditional style analysis products?

A) Those products typically use similar chemistries but customers who have used both often report that CHEMetrics vacuum sealed liquid reagent ampoules are faster (less mixing and measuring), safer (limited exposure to chemicals), and easier to use (less chance of operator error). These three factors add up to an overall savings in time and money. 


Q) How does ppm correspond to mg/L?

A) Most CHEMetrics kits report results as ppm, which is equivalent to mg/L for water samples.

Other helpful conversions:

1% = 10,000 ppm 
1 ppm = 1000 ppb

Q) How can I express nitrate results as NO3, instead of NO3-N? Phosphate results as PO4-P instead of PO4?

A) To convert nitrate results from NO3-N to NO3, the results must be multiplied by 4.43.

To convert phosphate results from PO4 to PO4-P, the results must be divided by 3.1. 

Custom tests:

Q) I routinely test for (your analyte) using a method that could be made faster, easier and safer with a self-filling ampoule. Will CHEMetrics develop a custom test kit for me?

A) If you've ever labored through a lab procedure, longing for a time-saving, self-filling ampoule method, call us! Our products often originate directly from customers eager for easier, more efficient ways to perform routine determinations. To be considered for a custom product, the test should be one that you perform frequently, or one that is widely used throughout your industry.

At CHEMetrics we have extensive experience with private-label packaging and service. We're very flexible in working with each customer's special needs, from printing labels to custom packaging. For more information on custom products and private labeling, call 1-800-356-3072and ask for Technical Services. We look forward to building a test that works for you. 


Q) What are CHEMets Kits? Vacu-vials Kits? VACUettes Kits? Titrets Kits?

A) Each of these CHEMetrics testing systems is based on the self-filling ampoule--a glass ampoule with liquid reagent vacuum-sealed inside. Sample is automatically drawn into the ampoule and mixed with reagent when the ampoule's tip is broken below the surface of the sample. The four variations of this technology are as follows:

CHEMets Kits - designed for visual analysis of samples with low to medium analyte concentration. Quantitation is performed by visual color comparison with liquid color standards.  CHEMets video

Vacu-vials Kits - designed for instrumental analysis of samples. Quantitation is performed photometrically or spectrophotometrically. Vacu-vials video

VACUettes Kits - designed for visual analysis of samples with high analyte concentration. Auto dilution feature on ampoule tip eliminates the need to perform manual dilutions of concentrated samples. Quantitation is performed by visual color comparison with liquid color standards. VACUettes video

Titrets Kits - designed for titrimetric analysis of samples. A valve assembly attached to the ampoule tip allows the analyst to draw small amounts of sample into the ampoule until a color change indicates the equivalence point of the titration. Quantitation is performed by reading the scale off the graduated ampoule.  Titrets video


Development Time:

Q) How important is the color development time allotment listed in the test procedures?

A) Timing is very important in colorimetric chemistries. Some chemistries will continue to develop color after the specified analysis time.  The most accurate test results will be obtained when the reading is taken at the time prescribed in the instructions.  Visual or instrumental readout after an extended period can give an erroneous result.


Q) Can I dilute my sample? What can I do if my developed sample color is darker than the darkest color standard?

A) In many cases, we can recommend dilution when a sample is slightly colored or turbid, when interferences are expected or when analyte concentration is high.  However, sample dilution is not appropriate for all analytes. 

We recommend using distilled or deionized water to perform the sample dilutions. A 1:1 dilution (1 part sample to 1 part distilled/deionized water) will double the range of your test kit. Higher dilutions can also be performed. Be sure to multiply your results to compensate for the dilution. For example, with a 1:2 dilution it would be necessary to multiply the result by 3. 


Q) How do I dispose of used reagent ampoules?

A) CHEMetrics' Safety Data Sheets (SDS) clearly list the chemical components of the solutions and reagents in our test kits. The operator must comply with local, state, and federal regulations for waste disposal. Contact your local regulatory agency or waste disposal company to learn the specific regulations governing your area. 

EPA Acceptance:

Q) Are CHEMetrics test kits EPA Accepted for reporting purposes?

A) CHEMetrics chlorine Vacu-vials® test kits (DPD chemistry) and COD vial methods (mercury-containing 0-150 and 0-1500 ppm ranges) are USEPA-accepted and may be used for compliance monitoring. In most other cases, the test kits are based on EPA methodologies.  Method references are listed in the catalog, on the web page, and in individual product instructions.


Q) How do I obtain current instructions for a CHEMetrics test kit?

A) Instructions in digital (pdf) format can be downloaded from the individual kit pages on this website. Or, CHEMetrics' Technical Services Department can email, fax, or mail instructions. Simply provide the catalog number of the test kit and your email address, fax number, or mailing address. 

SDS (Safety Data Sheets): 

Q) How can I obtain a Safety Data Sheet (SDS) for a CHEMetrics product?

A) SDSs in digital (pdf) format can be selected from a list provided under the "Support" tab on the home page of this website or by clicking on the following link: SDS Info.  Simply scroll to the catalog number of the product you need an SDS for, and click on the catalog number.  If you need assistance, contact our Techical Services Department at 540-788-9026 or

Instrument Calibrations:

Q) How can I check the calibration of my instrument?

A) The calibration can be checked by analyzing a standard solution of known concentration. We recommend testing at 25% and 75% of full range.

Q) How do I generate an instrument specific calibration curve?

A) To generate an instrument specific curve it will be necessary to prepare and analyze five standard solutions in the same matrix as your sample. The standard solutions should encompass the range of the test kit and should include a blank. The absorbance of each of the five standard solutions is plotted against the concentration. CHEMetrics' technical services staff can generate a calibration equation from your data.

Instrument compatibility:

Q) Can I use CHEMetrics ampoules in my spectrophotometer?

A) Yes, CHEMetrics products can be used in many instruments other than our preprogrammed instruments.  Most spectrophotometers capable of accepting a 13 mm (1/2 inch) diameter cell can be used with Vacu-vials ampoules. CHEMetrics VACU-vials kits include a calibration equation for use with spectrophotometers. An excellent way to validate your spectrophotometer with CHEMetrics Vacu-vials ampoules is to analyze standards of known concentration when possible.

Number of Tests per Kit -- 
Reordering Accessory Solutions:

Q) How many tests can I perform with one test kit?

A) In most cases, 30 tests can be performed with each CHEMetrics kit. Detergents, filming (aliphatic) amines, and FoalWatch® kits contain 20 tests. Sulfite in wine kits contain 10 tests. COD kits are sold in 25-, 98-, and/or 150-count kits.  Most ampoule refill packs contain the same number of tests as the kit.

If a particular test procedure requires one or more accessory solutions to be employed in addition to the vacuum sealed ampoule, then 1 bottle of each accessory solution is provided in the test kit. The bottle(s) of accessory solution which are provided will allow for 30 to 90 tests to be performed (the equivalent of 1 to 3 ampoule refills). Additional accessory solution may be purchased, if needed. Accessory Solution Packs generally contain 6 additional bottles of a particular accessory solution (enough solution to perform approximately 200 additional tests). 


Q) What test range do I need for my application?

A) Because CHEMetrics' test kits are designed for use in a variety of industries, the ideal test range for a particular application may not be known. However, CHEMetrics' Technical Services staff can make a recommendation in many cases.

Q) How is it that some CHEMetrics kits offer 2 ranges (e.g., 0-1 and 1-10 ppm)?

A) A dual range kit contains 2 separate color comparators (low and high range). When a test is performed, the analyst will use either or both comparators to obtain the test result. No sample dilution or test repetition is required.

Q) What if I need to test outside of the range of CHEMetrics’ test kits?

A) The range of many of CHEMetrics’ test kits can be extended by performing dilutions as discussed under the “Dilutions” heading. For lower range testing see the “Custom tests” section. While the ranges of many of CHEMetrics’ test kits are based on industry demand, some are restricted due to the limitations of the test method or available technology.

Sample Color:

Q) My sample is colored. Can I use CHEMetrics test kits?

A) Slightly turbid or colored samples can be analyzed using the instrumental test kits. Visual test kits can sometimes be used, especially when analyte concentration approaches the high end of the test range.

Also see the “Dilutions” heading. 

Sample pH:

Q) In order to use CHEMetrics test kits, what pH does my sample need to be?

A) A general rule of thumb for colorimetric testing is that sample pH should be between 4 and 8.

Sample Volume:

Q) How much sample do I need to conduct the test?

A) In most cases we recommend that the user have at least 25 mL of sample for Vacu-vials, CHEMets, ULR CHEMets, and Titrets kits. Smaller volumes are needed for VACUettes kits.

Shelf Life:

Q) What is the shelf life of my CHEMetrics product?

A) The CHEMetrics water analysis product line employs vacuum packaging to ensure the longest possible shelf life.  CHEMetrics shelf-life claims are based on products stored in the dark and at room temperature.  For specific shelf-life information, please see the individual product page.  Unless otherwise specified, all products have a shelf life of at least 1 year.

Soil Analysis:

Q) Can I use CHEMetrics kits to analyze soils?

A) Although CHEMetrics' test kits are designed specifically for water analysis, it is sometimes possible to extract, digest, or distill soil samples for analysis with our kits. Soil analysis test procedures are not currently included with the kits. Contact CHEMetrics' Technical Services Department for information on soil analysis methods and references. 


Q) Does CHEMetrics offer standard solutions so that I can confirm/document the analytical performance of the test kit?

A) CHEMetrics currently offers standards for COD only. Standards can be obtained from a variety of sources, including Fisher Scientific (phone:800-766-7000) or Labchem (phone:412-826-5230). A detergent standard can be obtained from Ricca Chemical Company (phone: 817-461-5601).

Titret Usage:

Q) After drawing the initial aliquot of sample into the Titret ampoule, I am unable to get it to draw any more sample.

A) Titrets ampoules are vacuumed sealed and use the vacuum to draw sample into the ampoule, therefore, if the vacuum is lost, sample will not be drawn into the ampoule. The valve assembly should be firmly seated at the reference line and not removed once the ampoule has been snapped.  Also, it is important that pressure be applied to the bead valve ONLY when the valve assembly tip is submerged in the sample.

Q) What if my Titret ampoule fills all the way and I do not see a color change? What if I see an immediate color change?

A) Titrets ampoules are based on a "reverse titration". If the ampoule fills completely and the endpoint is not reached (no color change) then the sample concentration is below the range of the kit. (Not enough analyte was added to reach the equivalence point of the titration and effect a color change). If an immediate color change occurs, the sample concentration is above the range of the kit.