Trace Perchlorate Quantification In Small-Volume, High-Chloride Solutions: A Method Supporting Experimental Investigation Of Perchlorate Generation On Mars

The discovery of abundant perchlorate (ClO4-) in Mars regolith has prompted experimental studies of the photo-oxidative production of ClO4- and other oxychlorines from chloride (Cl-) in processes involving illuminated semiconducting minerals. These experiments provide limited volumes of solution containing various concentrations of Cl- and ClO4- but usually with Cl- in substantial excess of ClO4-. A simple, one-dimensional isocratic ion chromatography (IC) method for ClO4- quantification was developed to mitigate the challenges of limited sample volume and complex sample pretreatment strategies encountered in other more expensive approaches. For the analysis, the ClO4- ions in a 0.5 mL sample containing up to (35 +/- 2) mg/L Cl- were concentrated inline on styrene/divinyl benzene resins of an ultratrace anion concentrator column, followed by suppressed conductivity detection. The result is a sensitive method for the determination of trace ClO4- concentrations in solutions containing up to 70,000 times more Cl- than ClO4-. The limit of quantitation established for this method was 0.5 mu g/L ClO4-, with an average recovery of 104%.