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California <br /> Water Labs <br /> December 15, 1988 <br /> Jamie Favila <br /> San Joaquin Local Health District <br /> P.O. Box 2001 <br /> Stockton, CA 95201 <br /> Dea: Mr. Favila: <br /> The following California Water Labs I .D. 's are associated with these sample I .D. 's: <br /> P-69986 Tank 11 North <br /> P-69987 Tank N1 South <br /> P-69988 Tank A2 <br /> P-69989 Tank N3 <br /> This should correct the organic lead typing error. <br /> Sample P-69986 (Tank N1 North) contained heavier hydrocarbons than Method 8020 can <br /> qualitate. This was indicated on the report form by the elevation of detection <br /> limits. <br /> According to Method 5030, Section 7.3.3.2 (High-level Method), "All dilutions must <br /> keep the response of the major constituents in the upper half of the linear range of <br /> the curve." By following this procedure, detection limits were elevated and sample, <br /> although positive, was reported as none detected. <br /> The purging efficiency of heavier hydrocarbons such as diesel is relativel + efficient <br /> at light end (C9-C12) and inefficient to non-purgeable at the heavy end (C18-C20) . <br /> For this reason, an aged gasoline which has lost the lighter aromatic fraction and <br /> diesel give nearly identical chromatograms. On the other hand, headspace adequately <br /> volatilizes the heavy end of diesel and allows discrimination between aged gasoline <br /> and diesel . <br /> On numerous occasions we have discussed the limitations of purge and trap analysis <br /> (8010/5030), and the numerous advantages of headspace analysis. It is my hope this <br /> situation will enlighten your view point on headspace analysis. <br /> Sincerely, _ - - - <br /> (3� `^"V•--"� <br /> Paul Ehrmann <br /> VOA Lab Supervising Chemist <br /> PE/do <br /> P.O.Box 4249 • Modesto,California 95352 • (209)527-4050 <br />