Induced coupled plasma analyzers

Minerals are usually analyzed by the traditional method of atomic absorption spectroscopy or with the newer induced coupled plasma analyzers. Most vitamins are analyzed by HPLC systems or colorimetric assays. Many laboratories still quantify folic acid with the use of a microbiological assay. The analysis of dietary and detergent (neutral and acid) fibers are critically important for foods and feeds, respectively. Raw materials and feeds should be examined for rodent contamination, pathogenic bacteria, molds and mycotoxins, and undesirable toxicants such as PCB, insecticides, herbicides, and heavy metals. The proper selection of ingredients will ensure the production of high-quality foods that satisfy sensory properties required for humans, and feeds that are palatable and can meet sensory properties required for domestic animals (Chapter 18). 

Until now, little attention has been given to the analysis of ancient copper alloys with LA-ICP-MS. This type of material is usually analyzed with fast or instrumental neutron activation analysis (FNAA or INAA), particle induced X-ray emission (PIXE), X-ray fluorescence (XRF), inductively coupled plasma-atomic emission spectrometry or inductively coupled plasma-atomic absorption spectrometry (ICP-AES or ICP-AAS). Some of these techniques are destructive and involve extensive sample preparation, some measure only surface compositions, and some require access to a cyclotron or a reactor. LA-ICP-MS is riot affected by any of these inconveniences. We propose here an analytical protocol for copper alloys using LA-ICP-MS and present its application to the study of Matisse bronze sculptures. 

DCIM-MS has been coupled to liquid chromatography (LC) for analyzing complex peptide samples [36], Peptides eluting from the LC column were analyzed on an IMS-Q-TOF mass spectrometer. The ions generated from the source were accumulated in an ion trap and injected periodically into the drift tube. After mass analysis by the quadrupole, ions were subjected to collision-induced dissociation (CID) within an octopole collision cell and the product ions were analyzed by a TOF analyzer. Using this instrumental configuration, the urinary proteome [37], the Drosophila melano-gaster head proteome [38], and the human plasma proteome [39] have been analyzed. While many additional measurements, compared to standard mass spectrometry-based proteomics experiments, were obtained (for example, collision cross-sections), these were not used to improve upon protein identification results. 

Online applications are by far the most important utilization of diode array spectrometry. High-performance liquid chromatography, supercritical fluid chromatography, capillary electrophoresis, and flow-injection techniques produce enhanced sensitivity and structure-related information due to coupling with diode-array-based detectors. Emission of the microwave-induced plasma generated in atomic emission detectors for capillary gas chromatography is also analyzed by means of UV-Vis diode array instruments. 

The photoabsorption spectrum a(co) of a cluster measures the cross-section for electronic excitations induced by an external electromagnetic field oscillating at frequency co. Experimental measurements of a(co) of free clusters in a beam have been reported, most notably for size-selected alkali-metal clusters [4]. Data for size-selected silver aggregates are also available, both for free clusters and for clusters in a frozen argon matrix [94]. The experimental results for the very small species (dimers and trimers) display the variety of excitations that are characteristic of molecular spectra. Beyond these sizes, the spectra are dominated by collective modes, precursors of plasma excitations in the metal. This distinction provides a clear indication of which theoretical method is best suited to analyze the experimental data for the very small systems, standard chemical approaches are required (Cl, coupled clusters), whereas for larger aggregates the many-body perturbation methods developed by the solid-state community provide a computationally more appealing alternative. We briefly sketch two of these approaches, which can be adapted to a DFT framework (1) the random phase approximation (RPA) of Bohm and Pines [95] and the closely related time-dependent density functional theory (TD-DFT) [96], and (2) the GW method of Hedin and Lundqvist [97]. 

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