Appendix C: QA Comparison Exercise 

 Appendix C 



Host Country Interlaboratory QA Comparison Exercise 



The need for quality control and intercalibration of analyses for chemical contaminants in 

 environmental samples has been documented numerous times during the past two decades (see 

 References in main report). Some advantages of inter-comparison exercises include: 



• create a frame of reference so that data from multiple labs can be used in 

 comprehensive, regional assessments. 



• introduce and evaluate advanced analytical methods 



• permit self-evaluation by participating laboratories and assist with training new 

 staff 



• impose an external incentive to maintain internal quality control programs 



• identify variation between laboratories and common sources of error leading 

 to this variation. 



A goal of inter-comparison exercises is to reduce the inter-laboratory variation in analytical 

 results. Such exercises are a mutual learning experience and are not a "test" to determine how 

 close any particular analyst comes to the "correct" answer. With sufficient time and funding, a 

 step-wise inter-calibration exercise would sequentially include: 



• a) analysis of standard solutions, 



• b) check of participants ability to prepare quantitative standard mixtures, 



• c) analysis of cleaned extracts, 



• d) analysis of whole extracts (no clean-up), and finally 



• e) analysis of environmental samples. 



In the small interlaboratory comparison exercise initiated by the Project Secretariat, we 

 jumped directly to step "e" because of time and funding constraints. We did this in anticipation that 

 further iterations of this collaborative effort based on the results of this exercise would continue 

 and be supported by additional funding. 



The Project Secretariat distributed selected quality assurance (QA) Standard Reference 

 Materials (Table CI) to all Host-Country scientists who retained International Mussel Watch 

 samples for analysis in their own labs. The Standard Reference Materials (SRMs) are listed on 

 Table CI and included internal recovery standards, quantitation standards for GC, two quantitative 

 pesticide mixtures, a commercial PCB solution and a Florosil column elution standard. In addition 

 to the SRMs, we also included a freeze-dried homogenized mussel tissue. As we did not know the 

 specific analytical methods being used in each lab, we distributed SRMs of general utility for 

 contaminant analysis. We encouraged each participating analyst to report their own results (i.e., 



CI 



