Proteome coverage and peptide identification rates have historically advanced in line with improvements to the detection limits and acquisition rate of the mass spectrometer. For a linear ion trap/Orbitrap hybrid, the acquisition rate has been limited primarily by the duration of the ion accumulation and analysis steps. It is shown here that the spectral acquisition rate can be significantly improved through extensive parallelization of the acquisition process using a novel mass spectrometer incorporating quadrupole, Orbitrap, and linear trap analyzers. Further, these improvements to the acquisition rate continue to enhance proteome coverage and general experimental throughput.

A simple flow injection manifold is described to perform the addition of isotopic spikes to aqueous samples online with ICPMS. The analysis involves one multielement spike injection in the sample carrier and another injection of the spike solution in a standard carrier. This standard must contain one element which is not present in the spike solution, to allow the determination of the dispersion coefficient. The same standard also allows a reverse isotope dilution (ID) analysis, in addition to corrections for mass discrimination and any spectroscopic interference on one of the two isotopes used for the ID analysis. This flow injection approach, therefore, requires only one isotope free of spectroscopic interference for elements whose isotopic distribution does not vary in nature (two isotopes are still needed for other elements since the "natural" ratio must then also be determined). No preliminary analysis of the sample is required prior to the actual ID analysis. Furthermore, the concentration profile resulting from the flow injection allows the selection of the best isotopic ratio in terms of error propagation. This approach, therefore, makes ID analysis as simple as an external calibration but with added accuracy and precision. It was successfully applied to the analysis of a river water certified reference material and to saline water.

An automated flow injection (FI) manifold is described to perform the addition of isotopic spikes to aqueous samples on-line with ICP-MS for isotope dilution (ID) analysis. The manifold uses the sandwich technique (with the nested loop approach) to perform an injection of the isotopic spike solution within a sample (or standard) plug, the resulting sample-spike-sample sequence being pushed toward the nebulizer by a 1% HNO(3) carrier. A standard, which must contain one element not present in the spike solution to allow the determination of the dispersion coefficient, must also be used to allow a reverse isotope dilution analysis, as well as corrections for mass discrimination and/or spectroscopic interferences. Indeed, because the signals from the individual isotopes are monitored continuously, only one isotope free of spectroscopic interference is required for elements whose isotopic distribution does not vary in nature (two isotopes are still needed for the other elements), as a correction for the interference can be made by comparison with the signals from the standard. Furthermore, this automated approach makes ID-ICP-MS a faster method and does not require any preliminary analysis of the sample because the concentration profile resulting from FI allows the selection of the best isotopic ratio. It was successfully applied to the determination of Mo in saline water.

The development and characterization of a new instrument for solid sampling which couples IR laser desorption followed by UV laser photo-ionization and analysis using an ion trap mass spectrometer has been investigated. For calibration, a new type of solid sample preparation involving activated charcoal as the solid substrate was used. This solid sample provided a steady signal for several thousand laser shots, which allowed optimization of the experimental procedure. It was found that both the IR and UV intensity and the delay between them play an important role in both the magnitude and type of signals observed. A method of gas phase accumulation with multiple laser shots was examined. Finally, this technique was demonstrated to be effective in providing direct qualitative information for N.I.S.T. SRM 1944 river sediment sample with no sample pre-treatment.

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