| Sub-nanogram per gram levels of molybdenum (Mo) from human blood plasma are isolated by the use of anion exchange alumina microcolumns. Million-fold more concentrated spectral and matrix interferences such as sodium, chloride, sulfate, phosphate, etc. in the blood constituents are removed from the analyte. The recovery of Mo from the alumina column is 82 ± 5% (n = 5). Isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS) is utilized for the quantitative ultra-trace concentration determination of Mo in bovine and human blood samples. The average Mo concentration in reference bovine serum determined by our method is 10.2 ± 0.4 ng/g, while the certified value is 11.5 ± 1.1 ng/g (95% confidence interval). The Mo concentration of one pool of human blood plasma from two healthy male donors is 0.5 ± 0.1 ng/g.; The inductively coupled plasma twin quadrupole mass spectrometer (ICP-TQMS) is used to measure the carbon isotope ratio from non-volatile organic compounds and bio-organic molecules to assess the ability as an alternative analytical method to gas chromatography combustion isotope ratio mass spectrometry (GC-combustion-IRMS). Trytophan, myoglobin, and β-cyclodextrin are chosen for the study, initial observation of spectral interference of 13C+ with 12C1H+ comes from the incomplete dissociation of myoglobin and/or β-cyclodextrin. The interference species is most sensitive to the aerosol gas flow rate. Carefully decreasing this parameter can eliminate 12C1H+ interference. 13C/12C ratios in myoglobin and β-cyclodextrin can be determined precisely and quantitatively. The best relative standard deviation (RSD%) obtained in the 13C/12C study is 0.91%, which is close to the limiting precision predicted by counting statistics (1.16%).; Many improvements have been made to the current ICP-TQMS device. A new skimmer interface together with the new ion optics arrangement improves the ion collection efficiency 19-fold. A second-generation ion beam splitter has been designed to reduce the background count rate and improve the ion transmission. A modified ion beam splitter transmits 5 times more ions while maintaining the performance characteristics of the ICP-TQMS system. The precision is further improved by measuring each data point for a longer dwell time (9s instead of 1.5s) and keeping the total ion collection time low (50s instead of 150s). |
