Portable, fully autonomous, ion chromatography system for on-site analyses

•Fully computer controlled autosampling, chromatography and data acquisition system.•Completely autonomous operation over 4 week period or ∼1930 injections available.•An eluent reflux device (ERD) enabled 100 mL of eluent to be continuously reused.•Data reproducibility over 14 days had a relative standard deviation less than 0.6%.

The basic operating principles of a portable, fully autonomous, ion chromatography system are described. The system affords the user the ability to collect and analyze samples continuously for 27 days, or about 1930 injections before needing any user intervention. Within the 13 kg system, is a fully computer controlled autosampling, chromatography and data acquisition system. An eluent reflux device (ERD), which integrates eluent suppression and generation in a single multi-chambered device, is used to minimize eluent consumption. During operation, about 1 μL of water per minute is lost to waste while operating standard-bore chromatography at 0.5 mL min−1 due to eluent refluxing. Over the course of 27 days, about 100 mL of rinse water is consumed, effectively eliminating waste production. Data showing the reproducibility (below 1% relative standard deviation over 14 days) of the device is also presented. Chromatographic analyses of common anions (Cl−, NO3−, SO42−, PO43−), is accomplished in under 15 min using a low backpressure guard column with ∼25 mM KOH isocratic elution. For detection, a small capacitively-coupled contactless conductivity detector (C4D) is employed, able to report analytes in the sub to low micromolar range. Preconcentration of the injected samples gives a 50-fold decrease in detection limits, primarily utilized for in-situ detection of phosphate (LOQ 10 μg L−1). Field analyses are shown for multiple on-site analyses of stream water indifferent weather conditions.