The development and application of preconcentration/preelution ion chromatography methods for the detection of trace perchlorate in difficult matrices

Perchlorate originates as a contaminant in the environment from the use of solid salts in the manufacture of solid rocket fuels and munitions. As a result of perchlorate occurrence and persistence, there has been much debate over what level of perchlorate is safe for daily consumption and USEPA recently set a reference dose for perchlorate. Ion chromatography (IC) is one of the most widely used methods for perchlorate determination because of its availability. However, analysis of biological samples by IC is often difficult because matrix components often interfere with low level detection. A preconcentration/ preelution ion chromatography method (PC/PE) was developed in our laboratory to address such interferences in high salinity samples and was proposed to have potential application for other matrices. In this study, the ability of the method to remove interferences and lower sample background was determined for gastrointestinal tract, kidney, liver, zebrafish, quail egg, lettuce, milk, urine, citrus, and soil matrices.
The PC/PE method was applicable to the analysis of kidney, liver, zebrafish, quail egg, lettuce, and urine samples. Operating conditions were optimized for each matrix and there appeared to be no significant effect of prewash solution concentration on background. The range of optimal wash volumes, regardless of matrix, was shorter with a 15 mM NaOH prewash solution than a 10 mM solution. Optimal injection durations varied with matrix type, but recoveries were excellent for most matrices at injection periods greater than 60s. The method was capable of reducing background when compared to EPA Method 314.0 which resulted in detection limits, with the exception of zebrafish and urine, that were 2-fold lower those achieved by common IC.
PC/PE was applicable to the remaining matrices, but poor recovery in the cleanup process hindered further investigation of the gastrointestinal tract and citrus matrices. Previously published methods for milk were determined to be better than the methodology developed here. Finally, there was no difference in soil background when analyzed by PC/PE compared to EPA Method 314.0. Therefore, an extraction method for perchlorate from soil with analysis by EPA Method 314.0 is presented here.