Optimization of flow splitters for preparative SFC-MS

A is naturally abundant in the crust of the earth and introduced into the aquatic system through dissolution and weathering of minerals. Chronic ingestion of arsenic in water may cause various diseases, including cancer and keratosis. A guideline for arsenic in drinking water has been set at 10 ppb of total arsenic by the World Health Organization (WHO). However, inorganic forms of arsenic, such as arsenites [As (III)] and arsenates [As (V)], are much more toxic than the organic forms as the monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA). Hence the quantitation of specific arsenic species may be more meaningful than the total arsenic determination for the evaluation of the health risks from arsenic-contaminated drinking water. We report a highly sensitive way of arsenic speciation using a commercial Capillary Electrophoresis (CE) instrument equipped with a UV absorbance detector. We used a counter-flow electrokinetic supercharging technique to enhance the detection sensitivity. Electrokinetic supercharging is one of the most powerful sample stacking methods that combine field amplified sample injection and transient isotachophoresis. In counter flow electrokinetic supercharging, a constant counter pressure is applied during sample injection in order to counterbalance the movement of the injected sample zone, obtaining a pronounced increase in the amount of sample injected and the portion of the capillary available for electrophoresis.