Calibration studies in laser ablation microprobe-inductively coupled plasma atomic emission spectrometry
The use of tandem techniques to separate the processes of mobilisation and excitation in atomic spectrometry is increasingly popular, both to aid the introduction of difficult test materials and to minimise the matrix effects associated with mobilisation. The use of the laser ablation microprobe for the introduction of material into the plasma for analysis by inductively coupled plasma atomic emission spectrometry (ICP-AES) has been demonstrated by a number of groups using solid standard calibration. However, the problems associated with the use of solid standards, including matrix effects, test material homogeneity and cost of preparation, are well known. This paper describes a study to determine whether matrix effects could be found by comparing element-relative sensitivities of test materials mobilised by laser ablation and aqueous nebulisation. On finding matrix effects, an attempt was made to characterise them as either associated with the laser ablation process or as spectrochemical effects in the ICP atomic emission spectrometer. A majority of the matrix effects are ascribed to the ablation process and it has been shown that a set of empirical matrix coefficients could be produced and used in conjunction with aqueous calibration.