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MORA i . AIR, WATER & HAZARDOUS i4ASTE LABDkATORY CERTIFIED by CALIFORNIA DEFT of HEALTH SERVICES chromatography and direct column-to-mass spectrometer source interfacing are Incorporated into the basic EPA protocols, the required 1 ppb sensitivities can be reached easily. Since the mass spectrometer is the most selective detector available, interferences and misassigi-ments are reduced dromotically. CCAS has applied GC/MS successfully to all of the six compounds listed in EPA Method 8015. - Detection limits of 0.1 ppb have been obtained without using selective Ion monitoring. These results are on file with the California Department of F:ealth Services (Hazardous Waste Certification and Drinking Woter Certification Branches). At the time at which EPA methods were being developed, economical, automated GC/MS instrumentation was not widely available. For this reason. GC/MS was considered to be too costly to serve as a practical -_lternotive to EPA Method 8015 and such selective detector methods as EPA 8010 and 8020. Recently. 1 instrument costs hove fallen to the point that a GC/MS system can be purchased {, for little more than double that of a comparable gas chromotograph. Moreover. positive results obtained using selective detection gas chrometography are subject to confirmation using another column (rerunning the test again) or by using GC/MS. Practical improvements in automation hove further improved the cost-effectiveness of GC/MS so that some fobs can now be done more e,,onomically ! by GC/MS than by GC, particularly when confirmatioh is necessary. ' For example, the analysis of soils adjacent to a leaking gasoline tank should include a fuel fingerprint to determine the fuel type and the total petroleum hydrocarbons (TPH) and EPA Method 8020 to quantify the benzene, toluene, and xylene (BTX) levels. Furthermore, if leaded fuel is suspected, ethylene dibromide (EDB) and ethylene dichloride (EDC) should be determined as these compounds are often added to gasoline to promote the removal of lead from the engine following combustion. EDB is a priority pollutant which is analyzed by EPA Method 8080.1. CCAS has selected those ions which are charocterisic of the oformentioned `components from among the ions available in the full scan EPA Methods 524.) and 624/8240: In tnis way we are able to determine simultaneously the most commonly requested information concerning volatile hydrocarbons in the environment. Furthermore, the cost for this analysis at - � t $135 in water and $155 in soil is substantially below the sum of the three separate analyses which would otherwise be required, namely, EPA 8015 0 $75/100, EPA 8020 0 $90/120 and EPA 8080.1 0 $75)100. Moreover, confirmation testing is not required when using GC/MS since it is the method recommended by EPA for confirmation. Furthermore, the use of internal standards is possible i and thereby provides a significant quality assurance advantage to the method. Additional compounds such as TCA. TCE and PCE which are often used at service { stations and sometimes discharged to faulty waste oil tanks con be oddsd to the program by special request, The adCitionol cost for this addition is not large and allows all cspects of the investigation to be handled with a single analysis. Thus it can be seen that GC/MS provides better information at a !I lower overall price. ' The GC/MS fuel fingerprint method has been shown to provide even more detailed information in cases in which depth and/or area profiles ore involved. Typically, one sees a distribution of fuel components with depth which dramatically changes itself once groundwater is reached. EDB, for example, may be found only at the groundwater interface due to its preferential solubility in water. Heavier, biorefroctory components ore retained by the soil neorar Page 7 -2553 CENTRAL COAST ANALYTICAL SERVICES San Luis Obispo, California (805) 543