Frequently Asked Questions

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. Please see the home page for more information on Industries and Applications.

Q) Will CHEMetrics develop or customise 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. Please contact us for more information regarding customised kits or chemistries.

Q) When can I use the mercury-free COD test kits? Are the mercury-free reagents USEPA 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 1,000 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 USEPA for reporting purposes in the USA.

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).

Please see the COD Procedure Notes document for more information.

COD Comparison Notes - comparing CHEMetrics Vials to alternative suppliers

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).

Hach Instruments that work with CHEMetrics COD Reagent Vials

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 in the USA.

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

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.

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

A) In many cases, we can recommend dilution when a sample is slightly coloured or turbid, when interferences are expected or when analyte concentration is high. However, sample dilution will reduce the sensitivity of your test kit and is not appropriate for all analytes, for instance, alkalinity, carbon dioxide, conductivity, dissolved oxygen, pH and ozone.

We recommend using distilled or deionised water to perform the sample dilutions. A 1:1 dilution (2× dilution: 1 part sample to 1 part distilled/deionised 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 (3× dilution) it would be necessary to multiply the result by 3.

High range Chlorine and Nitrate CHEMets test kits employ a dilution step as part of the test procedure and come complete with the required MiniPet®*. The MiniPet® is reusable. Each refill pack comes with 30 ampoules. MiniPets® and syringes can be purchased separately for use with other kits. Please see the Sample Dilution Accessories page for more information on the use of MiniPets®.

Q) Will dilution affect the accuracy of my test result?

A) The accuracy of the test kit will not change but if the original sample has been diluted then the accuracy of the final test result will decrease by the factor of dilution, assuming that the manual dilution procedure has been followed correctly and not introduced errors. We therefore recommend to use the most appropriate test kit for the purpose to minimise the amount of dilution required for your samples to provide the greatest level of accuracy, after factors such as discolouration, turbidity and/or interferences have been taken into consideration.

For instance, the Chlorine Dioxide CHEMets kit K-2705 has an accuracy in standard use of ±1 increment, i.e. ±1 ppm throughout the majority of the flat (high range) comparator range. However, with an original sample concentration of 70 ppm, and a 10× dilution (1 part sample to 9 parts distilled water) prior to testing, then the accuracy of the result for the original sample will be ±10 ppm of original sample concentration.

To provide an example of a Vacu-vials photometric test kit, Ammonia K-1503, the accuracy around 5.25 ppm is ±0.53 ppm using the standard test procedure and using a V-2000, V-3000 or Spectrophotometer. However, with an original sample of around 50 ppm concentration, employing a 10× manual sample dilution (1 part sample to 9 parts distilled water), the accuracy of the test result for the original sample becomes ±5.3 ppm.

Other options include sample filtration remove excess colour or turbidity that is not related to the actual sample analyte concentration. However, this may not always be appropriate depending on the testing environment or the analyte being measured. Another option is to use a photometric test kit rather than a visual test kit, in combination with a Sample Zeroing Accessory Pack (SZAP) to zero the instrument with the sample prior to measurement.

Turbidity and turbidity interference in colourimetric water analysis are discussed on the Turbidity Interference page.

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

A) Test Instructions for all kits and instruments are available for download on this web site. Click on the test kit catalogue number in the table on the relevant parameter pagea>. You may also contact us if you wish to request hard copies. Please provide us with the catalogue number of the kit and your fax number or mailing address.

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

A) SDSs in digital (pdf) format can be downloaded from the SDS page in the Support section of this site. If you need assistance, please contact us.

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

A) The calibration can be checked by analysing a standard solution of known concentration. We recommend testing at 25% and 75% of full range. We offer a range of verification kits for the V-2000 and SAM photometers using NIST traceable standards. We also presently offer a limited range of standard solutions, for Chemical Oxygen Demand and Hydrogen Peroxide.

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. We can arrange for CHEMetrics to generate a calibration equation from your data.

Q) What are the new replacement product Cat.No.s for the discontinued refills and accessory solutions?

A) CHEMetrics have streamlined a number of refills and accessory solutions in the product range to improve manufacturing and labelling processes and inventory management, and increase regulatory compliance. Historically components were assigned analyte specific part numbers even if they were identical. Now, CHEMEtrics have given all identical kit components across a variety of kits the same Cat. No. The formulations have therefore not changed but simply the Cat. No.s. The test kit Cat. No.s have not changed but stay as they are. These updated refills and accessory solutions now have revised packaging and labels to state which analytes each pertains to.

For example, A-1600 (Bromine), A-5501 (Hydrogen Peroxide), A-7400 (Ozone) and A-7900 (Peracetic Acid) all share identical reagent formulations. These Cat. No.s have all been replaced with a single Cat. No. A-2500. The new label states that the accessory solution pack is appliable to Bromine, Hydrogen Peroxide, Ozone and Peracetic Acid.

Regarding the above Nitrate products, R-6902, R-6904 and R-6905 Nitrate CHEMets refills were packaged together with Cadmium and Zinc foil packs. The replacement for these refills is R-7002 which does not come with any foil pack. The foil packs are available separately with their own unique Cat. No.s, A-6900 (Cadmium) and A-6905 (Zinc). This means that when Nitrate customers want to re-order their consumables, they need to order two Cat. No.s, i.e. R-7002 and either A-6900 or A-6905.

Q) Are VACUettes now discontinued?

A) In July 2024, CHEMetrics replaced the VACUettes test kit products with a new range of High Range or HR CHEMets. HR CHEMets are similarly designed for testing high concentration samples. The primary difference between VACUettes and HR CHEMets is that the dilution is now performed in the sample cup rather than inside the ampoule. HR CHEMets allow measurement of a precise aliquot of sample using the supplied MiniPet®* or syringe, which is then transferred to the sample cup and diluted with distilled water up to the indicated line. The ampoules are then used in the same way as CHEMets. The micro test tube or dilution tip used in the VACUettes kit has been eliminated from the test procedure. HR CHEMets kits offer the same test chemistries as their discontinued VACUettes counterparts, with some slight revision of test kit ranges.

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 colour 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 section. 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.

Q) What is REACH?

A) EU REACH is a European Union regulation concerning the Registration, Evaluation, Authorisation and restriction of Chemicals, EC 1907/2006. The aim of EU REACH is to improve the protection of human health and the environment through superior and earlier identification of the intrinsic properties of chemicals.

Under EU REACH, manufacturers and importers are obliged to register substances they produce or import in quantities over 1 tonne per year with the European Chemicals Agency (ECHA) in Helsinki. The deadline for registration of 'dangerous substances' (produced over 1 tonne per year) was 30 November 2010. The deadline for registering non-dangerous substances of over 1 tonne per year was 31 May 2018.

The EU REACH Regulation was brought into UK law on 1 January 2021 and is known as UK REACH. UK REACH has a similar threshold of 1 tonne per year per chemical to require registration.

Q) Is Galgo registered under REACH?

A) Galgo (UK) Ltd does not import any particular chemical substance (constituent ingredient of a CHEMetrics test kit for example) in quantities of over 1 tonne per year. As a result company was not required to pre-register or register any chemical according to EU REACH. As Galgo (UK) Ltd did not have any EU REACH registrations, it has not been required to transfer anything to UK REACH. Galgo (UK) Ltd is not presently required to make any new registrations with UK REACH. If however, in the future, Galgo does start to import any particular chemical ingredient in quantities over 1 tonne a year, then registration with UK REACH will be necessary (for each relevant chemical), and we will inform our customers accordingly.

Q) What action is required?

A) Neither the downstream (end) user nor any distributor are presently required to do anything under UK REACH with regards to CHEMetrics products.

End users of chemicals must apply the risk management measures for any dangerous substances identified on the manufacturer's Safety Data Sheets (SDS); and should use chemical products safely, responsibly and in accordance with the supplied manufacturer's instructions and recommendations.

End users also have a right to make their use of a substance known to the supplier in order to make it an identified use and have it covered in the supplier’s chemical safety assessment. Alternatively they may conduct their own chemical safety assessment and report this use to the chemicals agency. Neither action is however a mandatory requirement.

Q) What is the best way to draw sample into the Titrets ampoule?

• We would recommend always using the Titrettor device when using Titrets ampoules, to make it easier to control the amount of sample you are drawing in to more accurately reach the endpoint.
• Always keep the tip of the Titrets assembly submerged in the sample or you will introduce air into the ampoule. If it does occur then use a new Titrets ampoule and refill the sample cup with sample. It is best to keep the tip nearer the bottom of the sample cup to reduce the likelihood of this occuring.
• Tilting the sample cup may facilitate drawing in sample into the ampoule.
• Avoid pressing the control bar on the Titrettor too firmly or for too long or you may introduce too much sample into the ampoule at once, potentially overshooting the end point.

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.

A) Titrets ampoules are based on a "reverse titration". If the ampoule fills completely and the endpoint is not reached (no colour 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 colour change). If an immediate colour change occurs, the sample concentration is above the range of the kit.