Analytical Sciences

High Sensitive Elemental Analysis of Single Yeast Cells (Saccharomyces cerevisiae) by Time-Resolved Inductively-Coupled Plasma Mass Spectrometry Using a High Efficiency Cell Introduction System

Alexander S. GROOMBRIDGE,* Shin-ichi MIYASHITA,* Shin-ichiro FUJII,* Keisuke NAGASAWA,* Tetsuya OKAHASHI,* Masaki OHATA,* Tomonari UMEMURA,** Akiko TAKATSU,* Kazumi INAGAKI,* and Koichi CHIBA*

*Environmental Standards Section, National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology, Tsukuba Central 3-10, Umezono1-1-1, Tsukuba, Ibaraki 305-8563, Japan
**Division of Nano-materials Science, EcoTopia Science Institute, Nagoya University, Furo-cho, Chikusa, Nagoya 464-8603, Japan

Trace elemental analysis of single yeast cells with time-resolved inductively coupled plasma mass spectrometry (ICP-MS) was successfully carried out, where a high efficiency cell introduction system (HECIS) consisting of the high performance concentric nebulizer (HPCN) and a low-volume (15 mL) on-axis spray chamber utilizing a sheath gas flow were used. Cell adsorption to the flow injector and sample tubing was reduced with the addition of a simple 4.3 mmol L⁻¹ of NaCl solution to the cell suspension and cell flowing liquid, allowing consecutive measurements without fear of significant contamination from previous measurements. Initially using a quadrupole mass analyzer ICP-MS (ICP-QMS) at its lowest integration time (10 ms), current spikes corresponding to separate cell events were detected for several elements (Mg, P, Ca, Mn, Fe, Cu, and Zn) on the introduction of the cell suspension. On comparing the number of peaks in the spectrum for phosphorous with the cell count using a haemocytometer, a reproducible cell transport efficiency of 75.0 ± 4.7% was achieved. Preliminary experiments into using time of flight ICP-MS (ICP-TOFMS) for single-cell analysis were carried out, allowing quasi-simultaneous multielement detection. The spectra of Mg, P, Ca, Mn, Fe, Cu, and Zn, with a time resolution of 1 ms were simultaneously obtained in one measurement. A relatively strong correlation was observed for the spectra between P and Zn (correlation factor 0.69), P and Mg (0.63), and Mg and Zn (0.63). These results indicate that the time resolved quasi-simultaneous multielement measurement may be useful for the correlation analysis of multielements in cells.

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