Inductive coupled plasma with mass spectrometry

Sensing methods capable of quantifying these trace elements at low levels include atomic absorption spectroscopy (AAS), inductively coupled plasma (ICP) combined with atomic emission spectrometry (ICP-AES) or inductively coupled plasma with mass spectrometry (ICP-MS). The latter technique represents a powerful... 

Samples to be examined by inductively coupled plasma and mass spectrometry (ICP/MS) are commonly in the form of a solution that is transported into the plasma flame. The thermal mass of the flame is small, and ingress of excessive quantities of extraneous matter, such as solvent, would cool the flame and might even extinguish it. Even cooling the flame reduces its ionization efficiency, with concomitant effects on the accuracy and detection limits of the ICP/MS method. Consequently, it is necessary to remove as much solvent as possible which can be done by evaporation off-line or done on-line by spraying the solution as an aerosol into the plasma flame. 

With the advent of multiple-collector inductively coupled plasma-source mass spectrometry (MC-ICPMS) it is now possible to measure Mg/ Mg and Mg/ Mg of Mg in solution with a reproducibility of 30 to 60 ppm or better (Galy et al. 2001). What is more, ultraviolet (UV) laser ablation combined with MC-ICPMS permits in situ analysis of Mg-bearing mineral samples with reproducibility of 100 to 200 ppm (Yoimg et al. 2002a). These new analytical capabilities allow mass-dependent fractionations of the isotopes of Mg to be used as tracers in natural systems. 

The observed range of natural variations of 5 Ca is about 4 to 5%o in terrestrial materials and up to 50%o in high temperature condensate minerals in carbonaceous chondrites. The typical reproducibility of measurements is about +0.15%o. Broader application of Ca isotope measurements in geochemistry may be possible, particularly if the reproducibility can be improved to 0.05%o to 0.03%o. There is hope that this can be achieved either with inductively coupled plasma source mass spectrometry (Halicz et al. 1999) or with a new generation of multi-collector thermal ionization mass spectrometers (Heuser et al. 2002). 

AAS = atomic absorption spectrometry GC/FID = gas chromatography/f1ame ignition detector GC/FPD = gas chromatography/f1ame photometric detector ICP/AES = inductively coupled plasma atomic emission spectroscopy ICP/MS = inductively coupled plasma with mass spectrometric detection... 

M. Muller, K. G. Heumann, Isotope dilution inductively coupled plasma quadrupole mass spectrometry in connection with a chromatographic separation for ultra-trace determinations of platinum group elements (Pt, Pd, Ru, Ir) in environmental samples, Fresenius J. Anal. Chem., 368 (2000), 109D115. 

Analysis of Al can be routinely performed by inductively coupled plasma (ICP) mass spectrometry (ICP-MS). Alternatively, atomic absorption spectrometry with electrothermal atomization may be employed, but considerable attention must be paid to matrix interferences. 

More recently for ultratrace determination and speciation of antimony compounds the so-called hyphenated instrumental techniques have been applied which combine adequate separation devices with suitable element-specific detectors. They include high-performance liquid chromatography (HPLC) connected on-line with heated graphite furnace (HGF) AAS (HPLC-HGF-AAS), hydride-generation atomic fluorescence spectrometry (HPLC-HG-AFS) or inductively coupled plasma (ICP) mass spectrometry (MS) (HPLC-ICP-MS) capillary electrophoresis (CE) connected to inductively coupled plasma mass spectrometry (CE-ICP-MS) and gas chromatography (GC) coupled with the same detectors as with HPLC. Reliable speciation of antimony compounds is still hampered by such problems as extractability of the element, preservation of its species information, and availability of Sb standard compounds (Nash et al. 2000, Krachler etal. 2001). Variants of anodic stripping voltammetry for speciation of antimony have also been applied (Quentel and Eilella 2002). 

Muller M, Heumann KG (2000) Isotope dilution inductively coupled plasma quadmpole mass spectrometry in connection with a chromatographic separation for ultra trace determinations... 

Delville and co-workers selected 20 nm Si02 and 13 nm AI2O3 from commercial sources as particulate substrates for the attachment of aminopropyltrimethoxysilyl (APS) GdDTPA. The derivatized particles were prepared either by amination followed by reaction with DTPA bis(anhydride), or by peptide coupling of the particle surface amines with DTPA. The grafting of APS on sUica, as monitored by DRIFTS, resulted in the disappearance of Si-OH bands, and the appearance of the expected CH2 and carbonyl peaks of DTPA. XPS data established that Gd constituted about 4 atom % of silica, and 2 atom % of AI2O3. In this system there arc approximately 4 Gd complexes per silica particle as determined by inductively coupled plasma (ICP) mass spectrometry, with an average relaxivity. 

Automotive accidents are investigated by analyzing glass and paints. One way to match the glass from a broken windshield found at a hit-and-run accident scene is to compare elemental profiles. Inductively coupled plasma (ICP) mass spectrometry is an ideal method for this purpose [67]. Acid digestion is used for sample preparation. The use of laser ablation, coupled with ICP-MS, obviates the need for the laborious and time-consuming acid-digestion step [68]. 

Pin,C.,Telouk,P.,and Imbert,]. L. (1995). Direct determination of the samarium Neodymium ratio in geological materials by inductively coupled plasma quadrupole mass spectrometry with cryogenic desolvation. Comparison with isotope dilution thermal ionization mass spectrometry.J. Anal. At. Spectrom. 10(2), 93. 

Method abbreviations D-AT-FAAS (derivative flame AAS with atom trapping), ETAAS (electrothermal AAS), GC (gas chromatography), HGAAS (hydride generation AAS), HR-ICP-MS (high resolution inductively coupled plasma mass spectrometry), ICP-AES (inductively coupled plasma atomic emission spectrometry), ICP-MS (inductively coupled plasma mass spectrometry), TXRF (total reflection X-ray fluorescence spectrometry), Q-ICP-MS (quadrapole inductively coupled plasma mass spectrometry)... 

Measurement techniques that can be employed for the determination of trace metals include atomic absorption spectrometry, anodic stripping voltammetry, differential pulse cathodic stripping voltammetry, inductively coupled plasma atomic emission spectrometry, liquid chromatography of the metal chelates with ultraviolet-visible absorption and, more recently, inductively coupled plasma mass spectrometry. 

Soil samples were wet sieved into (a) 2-4 mm, (b) 1-2 mm, (c) 0.5-1 mm, (d) 250-500 i m, (e) 125-250 am, (f) 63-125 j,m and (g) <63 j.m fractions. A ferruginous/magnetic fraction (m) was also prepared from the 2-4 mm fraction. Soil fractions were crushed, digested with HNO3/HCI/HF/HCIO4 and then analysed by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) for Al, Ca, Cu, Fe, K, Mn, Na, P, S and Zn. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was used to determine Ag, As, Cd, Pb and Sb because of the lower detection limits by this method. The mineralogy of selected samples was determined by qualitative X-ray diffractometry. 

Ag, Cl, and N to six-figure accuracy.1 This Nobel Prize-winning research allowed the accurate determination of atomic masses of many elements. In combustion analysis, a sample is burned in excess oxygen and products are measured. Combustion is typically used to measure C, H, N, S, and halogens in organic compounds. To measure other elements in food, organic matter is burned in a closed system, the products and ash (unburned material) are dissolved in acid or base, and measured by inductively coupled plasma with atomic emission or mass spectrometry. 

Kimbrough and Wakakuwa [276,330] reported on an interlaboratory comparison study involving 160 accredited hazardous materials laboratories. Each laboratory performed a mineral acid digestion on five soils spiked with arsenic, cadmium, molybdenum, selenium and thallium. The instrumental detection methods used were inductively coupled plasma atomic emission spectrometry, inductively coupled plasma mass spectrometry, flame atomic absorption spectrometry, electrothermal atomic absorption spectrometry and hydride generation atomic absorption spectrometry. At most concentrations, the results obtained with inductively coupled plasma atomic emission spectrometry... 

The instrumental LoDs set forth in Table 3.1 shows that inductively coupled plasma-mass spectrometry (ICP-MS) is the technique that yields the best values. It should be considered that these limits are based on pure solutions analyzed under optimal conditions. Dealing with real foodstuffs will dramatically change the picture, owing to the complexity of the matrices and contamination phenomena in the laboratory. This means that in food laboratories without clean-room facilities (which is the vast majority) the practical difference in LoDs for ET-AAS and ICP-MS will be of minor importance. The relatively poor LoDs for inductively coupled plasma-atomic emission spectrometry (ICP-AES) when compared to those of ET-AAS implies that this technique is not fit for low-level determination of many elements, for example, Cd and Pb. 

It has been shown that the major part of Ca and Mg are found in the soluble fraction (whey) of human milk, whereas only small amounts are present in insoluble caseins or in fat [11-13]. Calcium and Mg speciation studies in milk whey using size exclusion chromatography (SEC) combined with inductively coupled plasma atomic emission spectrometry (ICP-AES) [14] indicated that they were preferably associated with the milk nonprotein fraction. A further work [15] showed similar chromatographic profiles by SEC hyphenated with inductively coupled plasma mass spectrometry (ICP-MS), with Ca and Mg eluting in the lowmolecular-weight region (LMW) (<1.4 kDa). Thus, there seem to be weak associations, if any, of Ca2+ or Mg2+ with higher molecular mass biocompounds of milk. 

This multiauthored book aims at highlighting the role played by atomic and mass spectrometry (with particular reference to atomic absorption spectrometry, inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry) in supporting and promoting research and control of foodstuffs and food commodities as regards both essential and potentially toxic chemical elements. The progress made so far in this field is overviewed and emphasis is put on the open problems that require further investment and development in the public and private sectors. 

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