FISHERY BULLETIN: VOL. 72. NO. 2 



RETENTION TIME IN MINUTES 



Figure 4. — A. Aroclor 1254 standard; column; 4% SE-30/6% 

 QF-1, 100/120 mesh Supelcoport. B. Sample of a 28-mmS. leucop- 

 sarus taken in November 1955 at CalCOFI station 83.55. Aroclor 

 1254, 4.2 ppm; pesticides not measured. Same column as A. C. 

 Standard of six DDT analogs. Same column as A. D. Sample of 

 one 37-mm S. leucopsarus taken in March 1954 at CalCOFI sta- 

 tion 85.45. 1.0 ppm total DDT. Same column as A. 



It is apparent (Figure 3) that the seventh of the 

 Aroclor peaks is not interfered with by the DDT 

 series. The two ortho-para prime peaks bracket- 

 ing it are generally small or absent. Therefore, it 

 may be used to correct the DDT series for PCB 

 interference and to quantify the Aroclor 1254. 



An estimate of peak area, peak height times 

 width at one-half peak height, was used in 

 quantification. Increasing chart speed makes it 

 possible to measure the width more accurately. 

 Peak area rather than peak height is a more accu- 

 rate measurement of the combined effects of two 

 CHC when their retention times are about the 

 same. Because GLC operating conditions may 

 thange gradually during a sample run, one pes- 

 ticide standard was injected for every two samples 



so that each sample would have an adjacent stan- 

 dard for quantification. 



To correct the areas of the combined peaks of the 

 DDT series and Aroclor 1254 to the area repre- 

 senting pesticide only, we letX equal the area of 

 each peak at the respective retention time of each 

 of the DDT series and Y equal the area of Aroclor 

 peak no. 7. Then for our operating conditions and 

 Aroclor standard, the areas allotted to the compo- 

 nents were: 



Area of 

 DDT series 



X- 0.247 

 X 



X- 0.547 



X- 0.737 



X- 0.957 



An estimate of Aroclor 1254 was obtained by mul- 

 tiplying the area of the no. 7 Aroclor peak by 12.3 

 and quantifying against the area of thep,p'DDE 

 standard, or multiplying by 9.6 and quantifying 

 against the area of the p,p 'DDT standard. The 

 subtractive corrections for the DDT series were 

 confirmed in part for a few samples by calculating 

 values both before and after dehydrochlorination 

 with alcoholic KOH. 



In a few samples taken far from the sewer out- 

 fall and in the earlier years, Aroclor 1254 was high 

 enough to mask out the DDT residues except for 

 slight increases in some peak areas (Figure 3). In 

 such cases the pesticides were present in such 

 small quantities that it made no appreciable dif- 

 ference in the overall results what small values 

 were assigned to them. The illustrated example is 

 an extreme case of masking. 



In most of the samples the DDT residues domi- 

 nated the PCB peaks and over the range of the six 

 pesticide standards (Figure 3), only peaks no. 6 

 and 7 of Aroclor 1254 were evident. If DDT re- 

 sidues were high, peak no. 6 was evident as a 

 widening of the base of thep.p'DDE peak (Figure 

 3). 



RESULTS AND DISCUSSION 



The pattern of CalCOFI stations from which the 

 samples were obtained extends across the north 

 flowing coastal countercurrent out into the south 

 flowing California Current cutting across the 

 counterclockwise eddy or eddies that develop be- 

 tween the two currents. At a depth of 200 m the 



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