Capillary electrophoresis in forensic soil analysis

Abstract

Background: Forensic examination of soil is not only concerned with the analysis of naturally occurring rocks, minerals, vegetation and animal matter. It also encompasses the detection of such manufactured materials like ions from synthetic fertilizers and environmental artifacts, so that soil samples always appear as important criminal evidences. Also, there are various techniques which are currently used in this area: capillary electrophoresis (CE) has become one of the powerful application of the electroanalytical chemistry which obeys rules both for the screening and legal analyses in forensic sciences. CE is now a widely used tool for separation and quantification of ionic substances. Separation speed and direct injection of samples to the capillary without labor-intensive sample preparation are the major advantages of the method for the wide variety of real samples. Method: Soil samples were dried and sieved for excluding the rocky particles which are bigger than 2 mw diameter. An aliquot of dry-sieved soil samples was mixed with folded volume of HPLC-grade deionized water. After shaking and centrifugation, supernatants were transferred into Eppendorf tube and centrifuged for 5 minutes at 12000 rpm. The supernatants were transferred carefully into the autosampler vials of the CE instrument which was programmed to apply triplicate runs for each set: of samples and the standards. Results: The evaluation of CE data of soil samples have shown that the range of chloride contents was from minimum 26 ppb up to maximum 2,635 ppb. The range of nitrate contents was in between 125 ppb and 3,368 ppb, These were 0 and 8,536 ppb for sulphate and 0 and 12,324 ppb for phosphate, respectively. Conclusion: There was no significant correlation between any of two samples in total ion contents, so that one could compare easily the soil samples at least from the CE screening of these major anions chloride, nitrate, sulphate and phosphate of the soil sample. In conclusion, if a forensic study needs the differentiation or comparison of soil samples or unification of a particular place or area, CE may easily play the most important role just by obtaining the anion electrophoregrams and therefore, the ionic composition of the sample.