The origin of peristaltic pump interference noise harmonics in inductively coupled plasma mass spectrometry

Abstract

Peristaltic pump interference noise and corresponding harmonics were investigated for inductively coupled plasma mass spectrometry, ICP-MS, by means of noise power spectra, NPS, and analytical precision data for ¹¹⁵In⁺ and ³⁸Ar⁺ measurements. A direct injection high efficiency nebuliser, DIHEN, and a micro concentric nebuliser, MCN, combined with a double pass or cyclone spray chamber were used for sample introduction. It was found that for the DIHEN the harmonics of the fundamental pump frequency originated from the liquid flow pattern of the pump and the non-linear relation between analyte signal intensity and liquid flow rate. For the spray chamber systems it was found that, under the experimental conditions used here, the harmonics mainly originated from the pulsations in the draining of the spray chamber. The operating frequency of the draining pump also had an influence on analytical precision such that a low frequency (1/3 Hz) of the draining pump was favourable for high measurement frequencies and a higher draining pump frequency (4 Hz) was favourable for low measurement frequencies.