Development of single-step liquid chromatography methods with ultraviolet detection for the measurement of inorganic anions in marine waters

Although a number of techniques exist to measure the major and minor inorganic anions Cl‐, NO2‐, Br‐, NO3‐, or SO42‐ in marine waters and sediment porewaters, a single method that can quantify all five anions in a single step with a sufficiently low detection limit has yet to be developed. In this work, a novel ion‐chromatographic separation procedure was developed that exploits the UV‐absorbing properties of Br‐, NO3‐, and NO2‐, as well as the suppression of eluent absorbance by high concentrations of Cl‐ and SO42‐ to quantify all these anions simultaneously in marine waters. If additional sensitivity for the minor anions Br‐, NO3‐, and NO2‐ is needed, NaCl can be used as eluent in a matrix elimination method that no longer allows for Cl‐ and SO42‐ determination. These methods are isocratic, require no chemical or electronic suppression, are not subject to interferences, and can resolve the anions in less than 18 min. The decrease in analysis time and the number of analyses required compared with conventional methods lowers the costs associated with laboratory analysis of marine samples. Last, the simplicity and good limits of detection make this separation method suitable for in situ analyses of marine waters and porewaters, and an in situ liquid chromatograph is currently under development for these applications.