COPING WITH EFFECTS OF HIGH DISSOLVED SALT SAMPLES ON THE INDUCTIVELY COUPLED PLASMA SPECTROMETER.

Research on acidic forest soils typically uses unbuffered salt solutions as extractants for exchangeable cations. Our lab uses 1 M NH[SUB4]C1 extractant for exchangeable cations (Ca, K, Mg, and Na) and 1 M KCl for exchangeable aluminum. The resulting high dissolved salt solutions presented chronic analytical problems on flame atomic absorption spectrophotometer (AAS) and direct current plasma spectrometer (DCP). More recently, the analyses completed on a simultaneous, axial inductively coupled plasmaatomic emission spectrometer (ICP-AES) have continued to be problematic. Although ICP manufacturers provide application notes that list some precautions to help minimize the salt effect, such issues are seldom mentioned in published articles and can be misleading when interpreting results. This paper describes various modifications that have been tried to eliminate the effects of high dissolved salts when using ICP. Adjustable parameters such as gas flow rates, sample introduction rates, dilution rates, and accessories were tested. Results of each modification were evaluated by comparing method detection limits, recovery rates, and carry-over values to determine the most effective operating ICP system. For example, a 15 second increase of sample uptake and rinse times for the KC1 method decreased the method detection limit (MDL) by 12%, recovery rate by 12%, and carry-over by 25%. [ABSTRACT FROM AUTHOR]