Plasma sources overall

The weakness of MC-ICPMS lies in the inefficiency by which ions are transferred from the plasma source into the mass spectrometer. Therefore, despite very high ionization efficiencies for nearly all elements, the overall sensitivity (defined as ionization plus transmission efficiencies) of first generation MC-ICPMS instruments is of the order of one to a few permil for the U-series nuclides. For most, this is comparable to what can be attained using TIMS. 

As in the sources used in optical atomic spectrometry a considerable ionization takes place, they are also of use as ion sources for mass spectrometry. Although an overall treatment of instrumentation for mass spectrometry is given in other textbooks [68], the most common types of mass spectrometers will be briefly outlined here. In particular, the new types of elemental mass spectrometry sources have to be considered, namely the glow discharges and the inductively and eventually the microwave plasmas. In contrast with classical high voltage spark mass spectrometry (for a review see Ref. [69]) or thermionic mass spectrometry (see e.g. Ref. [70]), the plasma sources mentioned are operated at a pressure which is considerably... 

Recently we published data that even in countries with excellent food sources and availability, insufficient vitamin A supply will occur (Schulz et ah, 2007). The aim of this trial was to analyze vitamin A and p-carotene status and investigate the contribution of nutrition to vitamin A and p-carotene supply in mother-infant pairs of multiparous births or births within short birth rates. Twenty-nine volimteers aged between 21 and 36 years were evaluated for 48 hours after delivery. In order to establish overall supply, retinol and p-carotene were determined in maternal plasma, cord blood, and colostrum via HPLC analysis. A food frequency protocol was obtained from all participants. Regardless of the high-to-moderate socioeconomic background, 27.6% of participants showed plasma retinol levels below 1.4 pmol/liter, which can be taken as borderline deficiency. In addition, 46.4% showed retinol intake <66% of RDA and 50.0% did not consume liver at all, although liver contributes as a main source for preformed retinol. Despite a high total carotenoid intake of 6.9 3.9mg/day, 20.7% of mothers showed plasma levels <0.5 pmol/liter p-carotene. 

Pharmacokinetics (PK) can be a major source of variability in the dose response relationship. It manifests itself in interindividual differences in the plasma concentration-time profile of a drug. Factors which lead to variability in the ADME parameters are therefore of importance in understanding overall variability in PK. 

As shown in the discussion above, there are a multiplicity of desirable and undesirable features of OID s that impact their general application as detectors in analytical atomic emission spectrometry. It is therefore appropriate to compare, in a critical and objective sense, the experimental figures of merit of these devices vis-a-vis the classical polychromator photomultiplier approach. These comparisons should be performed virtually on a continuing basis because of advances in performances, not only of the array detectors themselves but also in the associated spectroscopic excitation sources. An evaluation of the overall performance figures of merit of OID s when they are employed in conjunction with induction-coupled plasma excitation is of particular current interest because of the popularity that this source is attaining for the simultaneous determination of the elements at all concentration levels. In this paper we present such an evaluation for self-scanned, photodiode array detectors... 

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