Matrix interference diagnostics for the automation of inductively coupled plasma mass spectrometry (ICP-MS)

Matrix interferences in inductively coupled plasma mass spectrometry (ICP-MS) were examined to extend the total interference level (TIL) concept from ICP-AES. The TIL model is based on measurements with different interferents to determine a set of interference coefficients. Interference is assumed to be linear with interferent concentration, since that assumption allows determination of the model parameters with the fewest experiments. The TIL model was designed to indicate when a simple external standards calibration method is inadequate for a desired level of analytical accuracy and was also tested on a simple form of internal standards. The TIL concept was tested in both an initial calibration and a daily calibration mode on the interferents Na, K, Al, Ba and Cs and works well for situations where external standards are used, recommending an inaccurate method for only 3% of cases where 10% accuracy was desired. The TIL model also works well with the very different calibration technique of internal standards, recommending an inaccurate method for 9% of cases where 10% accuracy was desired.