Interference with Analysis of Amphetamine in Blood by N-Ethylbenzenamine from Rubber Septums

When blood stored In glass vials sealed with natural rubber �9 eptums was screened for amphetamine, a contaminant was seen. The contamination origin�9 from the rubber ssptums and was Identified by GC/MS as N-ethylbenzenamlne. Like amphetamine, N-ethylbenzenamlne was extracted from strongly alkalin�9 solutions. N-Ethylb�9149 and amphetamine chromatographed with the same retention time on �9 packed Aplezon/KOH column and on nonpolar capillary columns. Separation w�9149 achieved on s medium polar capillary column. Trlfluoroac�9 derivatives of amphetamine and N-ethylb�9149149 had the same retention time on �9 packed SP-2250 column, but separated on nonpolar capillary columns. The amounts of N-ethylbenzenamlne found were high enough to give rise to significant false positive results if N-ethylbenzenamln�9 was erroneously read as amphetamine. N-Ethylbenzensmlne Is believed to be formed by thermal decomposition of the vulcanizing agent zinc ethylphenyldlthiocarbamate used In rubber production.