10 _^^__^____ 



method blanks, matrix spikes, duplicate samples, and laboratory control samples. Method 

 blanks are laboratory QC samples processed with the samples but containing only reagents. 

 Method blanks test for contamination which may have been contributed by the laboratory 

 diuing sample preparation. No contaminants were measured in these method blanks. Matrix 

 spike sample analyses provide a measure of the efficiency and effectiveness of sample 

 preparation and analysis procedures, in addition to an indication of how tightly a compound 

 is bound to its matrix. Matrix spikes are also used to assess the accuracy of analytical 

 measurements. Duplicate samples indicate variability in laboratory procedures and degrees 

 of difference between individual samples. Duplicate blank spike and duplicate matrix spike 

 samples were used to measure precision in laboratory procedures. 



Laboratory control samples in this case were standard reference materials analyzed 

 using identical procedures as samples. Accuracy for the laboratory analytical reference 

 materials was within the control limits for the metals as well as the PAHs with the exception 

 of fluoranthene, which was above the acceptable range. However, since no other QC 

 samples indicated problems with the analysis of this compound, no qualifiers were necessary. 



Monitoring Cruise at the Western Long Island Sound Disposal Site, June 1991 



