BCO-DMO BlogInstrument: Mass Spectrometer
General term for instruments used to measure the mass-to-charge ratio of ions; generally used to find the composition of a sample by generating a mass spectrum representing the masses of sample components.
"A membrane inlet mass spectrometer was modified to perform rapid, high-precision measurements of dissolved 02, and Ar in water. The instrument pumps water at < 1 mL per min through semipermeable microbore silicone; tubing positioned inside an inlet vacuum line of a quadrupole mass spectrometer. Precise pumping and temperature control of the water sample contribute to high signal stability and reproducibility. Dissolved gas concentrations are determined from intensities of the mass spectrometer signals in the multiple ion detection mode.
Precision (coefficient of variation) is <0.5% for N2, 02, and Ar concentrations and <0.05% for N2/Ar and O/Ar ratio data. Deviation from expected values was between 0.5 and 1.5% for air-equilibrated water of widely ranging temperature and salinity. Advantages of the instrument over existing methods include rapid throughput (-20- 30 samples h-l), lack of sample water preparation (e.g., no degassing step), small sample size (<10 mL), and high- precision measurement of both concentration and gas ratio data. A limitation of the present instrument is the difficulty in measuring water with significantly supersaturated gas concentrations."
from Kana et al., 1994.
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