Investigation of internal standard use for short-term drift correction in ICP-MS/MS

Abstract

Noise in the signal of mass spectrometers is often corrected by an internal standard. This study investigates the effectiveness of internal standard application to environmental samples, namely, inductively coupled plasma-mass spectrometry analysis of particulate matter samples from the UK Heavy Metals Air Quality Monitoring Network at NPL. This Practitioner’s Report describes an investigation that has demonstrated potential drawbacks of internal standardisation using the set-up described, including bias in measured composition, which was found to contribute between 1.3–2.6%. Retrospective estimation of internal analyte content in particulate matter sample was carried out and found to be in good agreement with the literature (Y: 1 pg/m³, Sc: 5 pg/m³, In: 10 pg/m³, Bi: 50 pg/m³). Improvement of the signal to noise ratio is assessed and found to be minimal in the set-up investigated. It is concluded that for this application, introduction of an internal standard for high frequency noise correction gives minimal benefit and can even introduce measurement bias. These findings should be considered the next time the EN 14902 standard is revised.