Measurement and Results - Matrix matching for heavy metal ICP analyses of hard water

Matrix matching standards with samples is one of the most significant factors affecting data quality for ICP methods (whether OES or MS), and we’d recommend it if possible. However, it can be time consuming and difficult for routine analyses if the matrix varies widely between samples, so perhaps the more important question is how accurate and precise do you need your data to be? If you dilute your samples to have roughly the same total-dissolved-solids (TDS) as your calibration standards, and the corresponding detection limits are acceptable, then typical ICP measurements should generate results within ~2-10% for accuracy and precision. If, however, you require very high quality data then these are best obtained when the samples and  standards are not only matrix matched but a standard bracketing approach is used. In other words, matrix matching can account for nebulization and plasma related effects, but won’t account for other things such as instrument drift (interference effects also add a layer of complexity). For an initial suggestion, we’d recommend diluting your samples so that the TDS matches your standards, consider using internal standards to account for both matrix and drift effects, and avoid chloride if possible, as Mg-chloride species can particularly affect ICP-MS results for Co, Ni, and Cu. We also offer a number of resources on our website, and the ICP Operations Guide in particular discusses many of the topics mentioned here (https://www.inorganicventures.com/icp-operations-guide).