Trace analysis of a VX simulant in blood and tissue samples by solid phase extraction and gas chromatographic analysis with phosphorous-specific detection

An analytical method for phosphonoacetate, LT-8 in biological samples was developed. It is based on solid phase extraction and analysis by means of gas chromatography and detection with a detector specific for phosphorus (GC/NPD). Selection of column for separation and the condition of the detector were found to be crucial parameters. The method is linear within the field 0.1-1 microgram/ml serum. The detection limit for LT-8 is 0.002 microgram/ml serum. The reproducibility of the method is about 10 % relative standard deviation within the interval 0.01-1 microgram/ml serum. The recovery of the extraction procedure is about 75 %, when LT-8 is extracted from whole blood. The losses are probably obtained mainly during the separation of blood corpuscles from serum by centrifugation in order to ease the subsequent steps of the sample preparation procedure. The recovery after extraction of 0.5 microgram/ml LT-8 added to serum/buffer mixture was 90 %. Recovery of LT-8, 0.2 microgram LT-8/g wet tissue, added to other pig tissue samples (skin and muscle tissues) before the extraction procedure varied from 20-60 %. The explanation of this variation is at present not clear and has to be examined further in order to improve the recovery. When standard solutions of LT-8 were analysed by means of GC/NPD, a relative standard deviation of 1.5 % was obtained. When standard solution of LT-8 in ethylacetate together with the internal standard tributylphosphate (TBP) in the amounts 1-100 pg were analysed, the linear regression of the data had a correlation coefficient of 0.99997. The corresponding correlation coefficient of data from serum samples with LT-8 added was 0.9978. The developed method to analyse LT-8 in blood and other tissues is a necessary tool for future experimental studies in animals to evaluate the potential contamination risk and need for decontamination of trauma casualties also contaminated by a chemical simulant for the persistent and highly toxic nerve agent VX. In addition, our analytical method will probably be of great value in realistic decontamination exercises in volunteers, where LT-8 will simulate exposure to VX.