A simple laser ablation ICPMS method for the determination of trace metals in a resin gel

Trace metal analysis of DGT gels using laser ablation inductively coupled plasma (LA-ICP-MS) has traditionally been carried out by ablating single spots along a line to provide high resolution data on trace metal distributions on a resin gel. This work compares the performance of two different LA-ICPMS systems, one at Lancaster University, UK and another at VUB, Belgium, in terms of instrument sensitivity and limit of detection in the analysis of trace metals (Co, Ni, Cu, Zn, Cd, and Pb) bound by a DGT resin gel using SPR-IDA resin. No defocusing of the laser beam was necessary to prevent burning through the resin gel and the internal standardization became very simple by using ¹³C, naturally present in the resin-gel, instead of impregnating a back-up layer with ¹¹⁵In. Furthermore, this work also explores the option of analysing the spatial distribution of resin bound trace metals by means of ablating a continuous line between two points and considers the advantages of using this approach. The work found that the LODs assessed on blank samples for Cu and Pb are similar for both LA-ICPMS systems, while for Co, Ni and Zn they are lower for the one at VUB and for Cd for the other one at Lancaster. The work found that the laser ablation systems at the two laboratories allowed more precise control over laser power and spot size than previously reported. For the line scan, the optimum scan parameters were determined as: scan speed of 50 μm s⁻¹, output energy of 40% and repetition rate of 30 Hz. An acquisition time of 25 ms, resulted in a much lower resolution (10 μm) compared to the spot ablation (a crater size of 100 μm and also some space between craters) and a better sensitivity. The LODs using the line scan were found to be lower than those obtained by the spot ablation. However, for some of the metals the difference is rather small. This work suggests that the time and gas consumption achieved by using the line scan is about 30% lower than for the traditional spot scan