The analytical potential of a radiofrequency glow discharge orthogonal time-of-flight mass spectrometer (RFGD-TOFMS) has been evaluated in both pulsed and non-pulsed modes. A certified reference steel was selected for this study. The operating conditions of the GD plasma (pressure and applied power) were optimized in terms of sensitivity. Additionally, duty cycle and pulse width parameters were investigated in the pulsed RF mode. In this case, high analyte ion signals and improved signal to background ratios were measured after the end of the pulse, in the so-called afterglow domain. The analyte ion signals were normalized to sputtering rates to compare different operating conditions. It was found that the sensitivity in the pulsed mode was improved in comparison to the non-pulsed mode; however, the factor of enhancement is element dependent. Moreover, improved analytical performance was obtained in terms of ion separation capabilities as well as in terms of accuracy and precision in the evaluation of the isotopic ratios, using the pulsed RFGD-TOFMS. Additionally, depth profile analyses of a Zn/Ni coating on steel were performed and the non-pulsed and pulsed RFGD-TOFMS analytical performances were compared.
The analytical potential of a nanosecond laser ablation inductively coupled plasma mass spectrometer system, equipped with an ultra-fast wash-out ablation chamber, is critically investigated for fast and highly spatially resolved (∼μm) qualitative elemental distribution within single cells.
The influence of controlled addition of either hydrogen, nitrogen or oxygen (in the interval from 0.5 to 10% v/v) to an argon radiofrequency glow discharge (rf-GD) with optical emission spectrometric detection has been investigated in terms of analyte emission intensities, sputtering rates and analyte emission yields. Considering that plasma characteristics may vary greatly between conductive samples and insulators, both sample types (austenitic stainless steels and a homogeneous glass, respectively) have been employed in this study. Analytes investigated were silicon, iron, nickel and aluminium in the steel, while silicon, sodium, calcium and magnesium were selected in the glass.It was observed that the addition of the assayed molecular gases gave rise to a decrease of the sputtering rates, when comparing with pure argon, at any percentage of the molecular gas investigated. For hydrogenargon or nitrogen-argon mixtures it was found that the percentage of sputtering rate reduction, with respect to pure argon, was highly similar when comparing the results from both types of samples (e.g., the sputtering rate decrease for 1% H 2 , as compared with pure argon, was 33% for stainless steel versus 28% for glass). However, when adding oxygen to the argon rf-GD, the sputtering rate decrease, as compared with argon, was much stronger in the conductive matrix than in the glass.Concerning the emission yields, selective enhancements were obtained with the addition of hydrogen (e.g., at the Si I 288.158 nm and the Mg I 383.829 nm lines) or nitrogen (e.g., at the Al I 396.152 nm and the Mg I 383.829 nm line). However, a rather systematic increase of emission yields was found in the presence of 0.5-2% of oxygen in an argon matrix as compared to pure argon.
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