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A novel ablation cell for laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was developed. The ''high efficiency aerosol dispersion'' (HEAD) ablation cell is based on the use of a directed gas flow expansion of the laser generated aerosol at the ablation site and a venturi effect created by two nozzles to extract the aerosol into the main make up gas stream, which finally transports the particles into the ICP. The figures of merit were evaluated based on the ablation of glass SRM NIST 610 using two different cell gases (Ar and He). The investigation of the capabilities of this type of aerosol extraction (using a Nd:YAG laser, l ¼ 266 nm) demonstrates that a laser generated aerosol can be modified (HEAD effect) by shifting the original particle size distribution towards smaller particle sizes. This effect was obtained for both gases (Ar and He) for increasing cell gas flows and showed an optimum at a flow rate of 100 ml min À1 . In comparison with standard cell results, elemental ratios (e.g. U/Th) showed reduced elemental fractionation effects attributed to reduced agglomeration and, therefore, an improved vaporization of the aerosol within the ICP. Most importantly, stability and reproducibility of the ion-signals were significantly improved without compromising sensitivity. In addition to the glass analysis, the HEAD ablation cell was also used for the ablation of brass samples, as this matrix is known to show pronounced elemental fractionation effects due to the thermal volatility difference of Cu and Zn. The temporal stability of element ratios (e.g. Cu/Zn) achievable using such an extraction approach (5%) was significantly improved in comparison with previously reported Cu/Zn ratios (30%) measured using standard cell configurations.

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The capabilities of a millisecond pulsed glow discharge time-of-flight mass spectrometer for the quantitative analysis of organic molecules were investigated. Mixtures of analytes were separated by gas chromatography, and mass spectra were collected at three different time regimes during the pulse cycle-the prepeak, plateau, and afterpeak time regimes. Elemental information was collected in the prepeak, structural information in the plateau, and molecular ion information in the afterpeak. A sample mixture containing toluene, o-xylene, o-dichlorobenzene, and a binary mixture of methanol and sec-butanol were considered. Calibration curves were constructed for each time regime based on the intensities of the elemental, fragment, and molecular ions. Optimum linearity (r2 = 0.999) was achieved during the plateau time regime, although calibration in the prepeak was also demonstrated, albeit with slightly poorer correlation coefficients (r2 > 0.959). The minimum limits of detection (MDL) were 392, 422, and 557 ng, for toluene, o-xylene, and o-dichlorobenzene, respectively, using a 3-microL injection and a split ratio of 68:1. For the binary alcohol mixture, MDLs of 1.87 and 2.44 microg were determined for methanol and sec-butanol, respectively, based on the intensity of the 16O+ ion during the prepeak and using a split ratio of 58:1.

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