Frequently Asked Questions
Accuracy:
A: Statements of accuracy are based on laboratory tests performed under ideal testing conditions using standards of known concentration prepared in deionized water.
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 Titrets® ampoules have a non-linear scale. For most Titrets kits, the accuracy is +/- 10% error at twice the minimum concentration for a particular kit range. The exceptions are Carbon Dioxide Titrets kit Cat. No. K-1910 and Total Alkalinity kit Cat. No. K-9810. For these two kits, 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 “Instrumental Accuracy Statement” link under the Technical Information tab or 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.
Applications:
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.)
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.
COD:
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.
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).
Color Match:
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.
Conversions:
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.
Custom Tests:
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.
Definitions:
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:
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.
Dilutions:
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.
Disposal:
A: Please see this bulletin for more information.
EPA Acceptance:
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.
Instructions:
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):
A: SDSs in digital (pdf) format can be found here: SDS Info. Simply search the catalog number of the product you need an SDS for, and click on the product under the test kits tab. If you need assistance, contact our Technical Services Department at 540-788-9026 or contact us.
Instrument Calibrations:
A: The calibration can be checked by analyzing a standard solution of known concentration. We recommend testing at 25% and 75% of full range.
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:
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:
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).
Range:
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.
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.
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:
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:
A: A general rule of thumb for colorimetric testing is that sample pH should be between 4 and 8.
Sample Volume:
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:
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. If no shelf life is listed on the product page, the shelf life is at least 1 year.
Soil Analysis:
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.
Standards:
A: CHEMetrics currently offers standards for COD and hydrogen peroxide. Standards for other analytes 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).
Storage:
A: COD Standards, Cat. Nos. A-7301 and A-7310, must be refrigerated during storage. All other CHEMetrics products should be stored at room temperature and in the dark. The shelf life of a few products can be extended by refrigeration, as specified on the individual product webpages and on the product labels. Prolonged exposure to extreme temperatures or light may adversely impact product performance or shorten the shelf life. Contact technical@chemetrics.com for more information about particular products.
Titret Usage:
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 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.