Understanding Quality Control: Standard Operating Proceduresby Energy Technical Services on 01/02/15
Understanding Quality Control: Standard Operating Procedures
Understanding Quality Control is a series written by Kailey Dickens,
environmental lab manager at ETS. The series focuses on real quality control issues and solutions as experienced in the lab at ETS.
Standard Operating Procedures – 40 CFR 136.7
The EPA requires the following 12 quality control elements, where applicable, in each standard operating procedure (SOP):
1. Demonstration of Capability
2. Method Detection Limit
3. Laboratory reagent blank
4. Laboratory fortified blank
5. Matrix spike
6. Internal standards
7. Calibration (initial and continuing)
8. Control charts
9. Corrective action
10. Quality control acceptance criteria
11. Definitions of preparation and analytical batches
12. Minimum frequency for conducting QC analysis
Now that’s a mouthful – but don’t fret. Writing a quality SOP does not involve reinventing the wheel. Many times, SOPs can be easily derived from pre-existing methods from ASTM, EPA, USGS, or Standard Methods. However, each SOP must contain the above 12 elements, regardless of whether or not they are included in the original method.
In some cases, one or more of the above is not applicable. In the instance of total suspended solids (TSS), it’s quite difficult to spike a sample with more solids, and is not required. However, it is required to include in the SOP that matrix spikes are not applicable for that specific analysis.
What the EPA does not require is crucial to a laboratory’s success – a quality SOP should include how to perform an analysis as if one has never seen glassware, reagents, or even a lab. Reagents should be identified with chemical name, chemical symbol, concentration, and volume. Glassware should be identified consistently through the SOP and specified in the introduction so a new analyst can easily find the required glassware. Following the TSS example, a quick Google search for “filter flask” can point a new analyst in the right direction, as seen below:
An SOP should be updated or revised once a year, or each time the method is changed. Each new analyst trained is an opportunity to identify existing errors or misunderstandings that arise from the current method. The SOP is insurance that each analyst is performing the analysis the exact same way. It also aids analysts in troubleshooting and instrument setup without needing to seek external assistance.
Happy New Year from ETS!