Back to School Series – Part 2
Ever receive a report and feel a bit confused? You may see an abbreviation, or a term and think “I should know what that means,” but you don’t. Have no fear! Laboratory analysis involves complicated processes and procedures, but we work to make data review easy for our clients by providing resources to help you understand what you are reading. Still have questions? Don’t ever hesitate to contact us! Our technical experts are here to help you sort through it all.
Decoding Your Report
Here are a few common terms that may appear on a standard results report to help you understand what they mean, and the potential for impact to your data.
- CCV: Continuing calibration verification. Ongoing calibration standard (run after every 10 or 20 samples, for example) to verify the calibration hasn’t drifted due to instrument conditions (i.e., does a 5 ppb standard still give 5 ppb?).
- Dilution water blank: The laboratory performs the appropriate check on the quality of the dilution water to ensure that when used as a blank, it has been evaluated to ensure blank QC criteria is met, and thus has no impact on results.
- Duplicate: A separate aliquot of a sample taken through the entire prep/analysis process. Used to determine precision in a matrix.
- Headspace: Term used in volatile organics analysis in waters. This is the airspace present once a sample has been collected. You do not want headspace in your sample container. Headspace in a volatiles samples is flagged; larger than a pea is reason for data rejection. Volatiles have a lower boiling point than water, and may off-gas in normal temperatures, which then compromises the results.
- LCS: Laboratory Control Sample. Matrix similar to that of samples spiked with a known amount of analyte and taken through the entire prep and analysis process. Compared to laboratory control limits to demonstrate that method is in control.
- MS: Matrix Spike. Similar to an LCS except that an actual sample is spiked. Used to determine if matrix interference is present in a sample matrix by comparison to the LCS (e.g., if LCS is in control and MS is out, it can be assumed to be matrix interference).
- Method Blank: Matrix similar to that of samples taken through the entire preparation and analysis procedure. Shows any potential contamination that may occur during prep/analysis or between samples.
- RL: Reporting Limit. This is the lowest level to which data are reported with a specified degree of accuracy. Typically it is the LOQ (Limit of Quantitation), or lowest calibration standard.
- Surrogates: Used for Organics analyses and added to every sample, standard and QC prior to analysis. A surrogate is a chemical similar to a target analyte that responds in a similar manner. Surrogate recoveries are compared to control limits to give an indication of method performance on each sample. If the surrogate is in control, there is confidence in the result reported on the target analyte.
- Sterility check: During microbiological analysis, the sterility check is used to confirm that no contamination occurred during the sample preparation process. Typically two sterility checks are used. The first check is done before the samples begin the testing process, and the second check is immediately after the last sample is tested.