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� r <br /> l <br /> Lawrence Livermore National Laboratory <br /> To: James G. Gianaopoulos <br /> State Wamr Resources Control Board <br /> From: Anne Haapei, Ph-D. <br /> Lawrence Liv=, ore Nadonal Laboratorf,L-530 <br /> Environmental Restoration Division <br /> 70G0 East Ave., P.O. Bax 808 <br /> Livermore, CA 94550 <br /> Date: August 6, 1996 <br /> SUBTFCT <br /> Comparison of EPA 8020 and EPA 8240 Analytical Results for Measure,mens of Methyl Tertiary <br /> Buryl Ether(MTBE) in Gmund Watei Samples ,am LUFT Sites, <br /> METHODS <br /> We have rcviewed MTBE ground water data submitted to us by seveml oil companies, including <br /> Shell, Texaco,ARCO, and Unocal. We have evaluamd data from gzound water samples <br /> concurrearly analyzed for-MTBE using EPA methods 8020 and 8240. In arder to compare the <br /> defecson arA quanarcation of MTBE by these two methods,we zr:c:cd our study to a total of <br /> 98 groundwater samples that reported MTBE values greater or equal to 20 ugfL by FPA <br /> method 8020 and/or a240- 'Ibis data was evaluated for the o==-.i= of false eves and for <br /> the level of a-p-t--meent berween values=portedby each of these analytical metizods_ The MIME <br /> values detected by EPA methods 8020 and 8240 were cam-cared without the assumprion of <br /> s=owldge of the hue value by calculating tie Relative P:-c=t DirTe== (RSD). In this report, <br /> RPD values greater than 40% indicate an unacceptable leve: of dispa iry be*ween the values <br /> obtained by these rwo analytical methods_ <br /> Occurrence of False Positives: There has been much discussion as to whether EPA method <br /> W20 is adequate for determining MTBE concentrations in LUFT ground warty samples_ <br /> Anecdotal information from analytical laboratories and remediation eggs report false <br /> positive detections of-MISE by EPA 8020. Fa—I-e positive cases occ=whem E_D.4 8020 arslysi�;, <br /> a gas chromatography/photo ioaizdon derec'.or(GC/PM) medwd, detects MTBE, whilc <br /> contnataauQn by EPA sz4o, a gas cbrornatographq/mass spectrome:.y (GClMS) medcd, <br /> do==mes MTBE to be non-de;ez-t (ND), '/`nese anis-identifftcadens of MTBE by EPA 8020 <br /> analysis ars a=iouted to the =se<sce of oche_-hyd:o=bons (gasoline components) thnc may ca- <br /> clute with-MTBE under.-standard GC/PID cor3didms used for B= analy52s. <br /> in this data ser, the overall occarrcncr of false positives by FSA 8020 was low. Among the total <br /> 98 MTBE positive samples only 2 false positives wc--=mpormd (2% of samples —ith MTBE <br /> conztntrations >20 ug/L). As exmecmd, false positives only occu=ed in samples that canrai.ned <br /> elevated ccnc mons of gasoli�c components (Table I)- False positives occurred in 4%. of <br /> the samples (2 out of 50 samples) that containied BTEX and/Gr B compounds at <br /> concentrations greater or equal to 150 ugfL. No :else negative sampies occuzr:�in tEz:s dam <br /> sot. <br /> An cqu9i Cpporsjnel cam.-urxversq,of Caibrrw•P.a sax see 4,ermaro.C-Oarw:;A r-TeAwbane(;%9 A2---r 100-r,rr 9 ra. �c.CL `-= <br />