The International Mussel Watch 



If any of the above cases occur the analyst should reject the results of the analysis of the 

 particular batch of samples and should not carry out any further analysis of samples until the 

 source(s) of the errors have been identified and he/she is satisfied that the results of future analyses 

 will be within acceptable error limits. 



The accuracy of a method can only be checked with a SRM for which the mean values and 

 standard deviations are well documented (i.e. "certified"). Analysts who choose to use their own 

 specially prepared reference material (RM) for quality control purposes should note that they are 

 primarily checking the precision of measurements and not their accuracy. These internal RMs are 

 very convenient, for analyses where large quantities of materials are required for each 

 determination (e.g., analyses for organic contaminants) where the cost of SRMs for QC charts 

 would be prohibitive or for sample types and analytes for which no certified SRM is available. 



More detailed discussion of QA/QC practices is available in the published literature (see 

 e.g., Taylor, 1985 and UNEP, 1990 and references sited therein). 



7. Reporting of Results 



A example format for reporting analytical results for PCBs, and DDT, DDD and DDE is 

 given in Table D.3. Full details should be recorded for every entry. 



8. Sources and Description of Certified Mixtures 



Standards are commercially available through the National Institute of Standards and 

 Technology (formerly National Bureau of Standards (U. S. A.) and from chemical suppliers who 

 have agreed to prepare certified SRMs for the U.S. Environmental Protection Agency. Selected 

 chlorinated pesticide SRMs will be shipped by the Project to participating analysts during the Initial 

 Implementation Phase. 



The IOC reference solution of PCB congeners PCB 1 (IOC-KIEL) in iso-octane contains 

 16 congeners at concentrations of about 1 ng |il~l. Requests for a 500 u.1 vial should be directed to 

 Head of Marine Pollution and Monitoring Unit, IOC UNESCO, 7, Place de Fontenoy, 75700 

 Paris, FRANCE. 



A set of four mixtures (CLB 1-A, -B, -C, -D) in iso-octane can be purchased from the 

 National Research Council, Atlantic Research Laboratory, 1411 Oxford Street, Halifax, Nova 

 Scotia B3H 3ZI, CANADA. 



Table D.4 presents the different PCB congeners present in two available (PCB 1 and CLB 

 1) standards. 



108 



