Use of direct current plasma as an element selective detector for simultaneous ion chromatographic determination of arsenic(III) and arsenic(V) in the presence of other common anions

Abstract

Direct current plasma atomic emission spectrometry (DCPAES) was evaluated as an element selective method of detection (ESD) for ion chromatography (IC). By use of DCPAES, different species of a given element can be determined with identical measurement sensitivity. Those species that are separated in the chromatographic analytical column but are not detectable by conductivity detection, such as As(III), are easily detected by monitoring the atomic emission of a targeted element (in this case arsenic) in the chromatographic effluent. With the use of DCPAES, interference and other matrix effects are eliminated. Thus, a wide range of eluent composition can be employed without experiencing detector limitations. Reduction in detection capability as a result of dilution of the analyte during the chromatographic process can be offset by employing large (up to 1000..mu..L) sample injection loops or by using a concentrator column. With a concentrator column, the measurable concentration of arsenic was found to be 10 ppb with a detection limit of 2.5 ppb. These values are 3 orders of magnitude smaller than those determined when dc plasma is used in the uninterfaced mode. With the use of element selective detectors, element speciation can be facilitated considerably.