Development of a new detection method for cadmium in marine phytoplankton based on single cell inductively coupled plasma mass spectrometry

Abstract

In recent years, with the development of single cell ICP-MS, we have now been able to perform analysis on a single cell to determine its metal content. In this study, we used single-cell ICP-MS to analyze cadmium content in marine phytoplankton cells. Previously, phytoplankton in seawater media could not be directly analyzed because of the high concentrations of interfering elements (Na+, K+) in seawater. To solve this, we removed the supernatant through centrifugal separation and replaced the culture media of three marine phytoplankton species, P. parvum, O. viridis, and E. gynnastica, with non-metallic salt solutions, (NH4)2SO4 and NH4Cl. To check for ruptured cells as a result of changes in osmotic pressure after solution replacement, we studied the images of the cells at different concentrations of replacement solutions. We observed that a large number of cells ruptured at low concentrations of (NH4)2SO4 and NH4Cl but maintained their integrity between 0.6 and 0.8 M solutions. The cells maintained in 0.6–0.8 M non-metallic salt solution were successfully determined using single-cell ICP-MS, which showed increases in the percentages of high cadmium-containing cells when the phytoplankton were cultured in medium containing high cadmium concentration. Based on our results, we suggest that both, (NH4)2SO4 and NH4Cl are suitable replacement solutions for the determination of marine phytoplankton using single-cell ICP-MS. However, the compatibility of (NH4)2SO4 and NH4Cl may differ for different species of marine phytoplankton. SynopsisA novel method to analyze cadmium in marine phytoplankton cells was made possible using replacement solutions and single cell ICP-MS.