MULTIELEMENT OPTIMIZATION OF THE OPERATING PARAMETERS FOR INDUCTIVELY-COUPLED PLASMA-ATOMIC EMISSION-SPECTROMETRY WITH A CHARGE-TRANSFER DEVICE DETECTION SYSTEM - A STUDY OF THE EFFECTS OF DIFFERENT RESPONSE FUNCTIONS

A new response function for ICP-AES is proposed in which the resultant compromise plasma conditions are independent of the concentration of the analytes in the test solution, The response function is designed t o be used in situations where the concentrations of the analytes in th e sample are unknown, or, when many samples, of varying composition, a re to be analysed, In addition, the use of the signal-to-root backgrou nd ratio (SRBR) as the measurement of the analytical performance of an element for multi-element analysis by ICP-AES, with a charge-coupled device detector, is described, The use of the SRBR was found to give b etter detection limits than those obtained with the more commonly used signal-to-background ratio (SBR), For instance, the detection Limit f or Mn II at 257.610 nm is improved from 13 ng ml(-1) when using the SB R and the proposed response function, to 2.8 ng ml(-1) when using the SRBR. The compromise operating parameters, and hence detection limits for the analytes, were shown to be independent of the composition of t he test solution for the new function, In comparison, the detection li mit of Mn II varied between 2.9 and 40 ng ml(-1), depending on the tes t solution composition when optimizing with a previously reported resp onse function, Furthermore, biasing the proposed function for a partic ular analyte by increasing a weighting parameter is demonstrated, For instance, the detection limit of Pb I at 280.199 nm improved from 54 t o 41 ng ml(-1), by increasing the weighting parameter for Pb from 1 to 10.