Quantification procedures

Quantification of analytical data (ion intensities of analytes) is a fundamental aspect of acquiring the best possible results from mass spectrometric measurements in order to obtain reliable 

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INTEGRATION WITH HARDWARE ANALYSIS. The error probabilities obtained from the quantification procedure are incorporated in the overall system fault trees and event trees. 

QUANTIFICATION PROCEDURE. In order to illustrate the SLIM quantification method, the case study developed in the earlier part of the chapter based on the chlorine tanker filling example will be used. The following operations from Figure 5.6 will be used to illustrate the method. 

EELS interfaced to the TEM column. Elements with an atomic number Z < 4 cannot be detected, and quantification of the signal from elements with Z < 8 is difficult. The accuracy of the quantification procedure in the TEM is about 5%, compared with EPMA (about 1-2%), although the actual mass analysed can be very small ( 10-22g). 

The phenomenon of discrimination induced by matrix effects is quite disadvantageous in qualitative analysis, but in the quantification procedure its influence is devastating. Several techniques applying MS or MS-MS, however, can help to overcome this crucial influence. The most common way out of this dilemma is the application of column separation to minimise or even exclude matrix effects entailed with the disadvantage of long-lasting separations. In parallel, the difference between the time needed for the performance of LC examinations and the time needed for FIA becomes obvious and will be pointed out later on. 

The majority of the more than 100 odorants (reviewed in [1]) synthesised for use as internal standards are labelled with deuterium. However, during the quantification procedure some deuterated odorants might undergo deuterium-protium exchange, which would falsify the results. Examples are 4-hydroxy-2,5-dimethyl-3(2H)-furanone (furaneol) [68, 69] and 3-hydroxy-4,5-dimethyl-2(5H)-furanone (sotolon) [70], which are consequently labelled with... 

Trends in mass spectrometry focus on the improvement of instrumentation, of several techniques in order to minimize sample volume, to improve sensitivity and to reduce detection limits. This is combined with increasing the speed of several analyses, with automation of analytical procedures and subsequently reducing the price of analysis. A minimizing of sample volumes means a reduction of waste volume with the aim of developing green chemistry . Furthermore, new analytical techniques involve a development of quantification procedures to improve the accuracy and precision of analytical data. Special attention in future will be given to the development of hyphenated mass spectrometric techniques for speciation analysis and of surface analytical techniques with improved lateral resolution in the nm scale range. 

Calibration and quantification procedures are easier in LA-ICP-MS compared to other solid-state mass spectrometric techniques because the laser ablation and the ICP ion source operate at normal pressure and the laser ablation of solid samples and ionization of analytes are separated in space and time. Therefore the advantage of solution calibration in ICP-MS can be applied in this solid-state analytical technique. The introduction of solution based calibration, which is only possible in LA-ICP-MS, was an innovative step in the development of this sensitive mass spectrometric technique. A number of different calibration approaches using aqueous standard solutions in the dual gas flow technique have been discussed by various authors.74 75 In the dual gas flow injection technique , the nebulized standard solution and the laser ablated sample material are mixed in the -piece and the two gas flows from the nebulizer (e.g. ultrasonic nebulizer) and laser ablation chamber are added. Using solution based calibration with the addition of a standard solution, Leach et alP determined minor elements in steel reference materials with a relative accuracy of a few %. In comparison to the so-called dual gas flow technique proposed in the literature, where the argon flow rates through the nebulizer and ablation cell add up to 11 min-1 (e.g. 0.451 min-1 and... 

Bings77 quantified 11 trace metals in lubricating oil with the aid of solution based calibration in LA-ICP-MS using a ToF mass spectrometer. It has been shown that good analytical performance in terms of precision (6 % on average) and low detection limits in the ng g-1 range can be obtained with this easy and fast quantification procedure in LA-ICP-MS.77... 

Trace impurities in noble metal nanoclusters, used for the fabrication of highly oriented arrays on crystalline bacterial surface layers on a substrate for future nanoelectronic applications, can influence the material properties.25 Reliable and sensitive analytical methods are required for fast multi-element determination of trace contaminants in small amounts of high purity platinum or palladium nanoclusters, because the physical, electrical and chemical properties of nanoelectronic arrays (thin layered systems or bulk) can be influenced by impurities due to contamination during device production25 The results of impurities in platinum or palladium nanoclusters measured directly by LA-ICP-MS are compared in Figure 9.5. As a quantification procedure, the isotope dilution technique in solution based calibration was developed as discussed in Chapter 6. 

Time consuming step sample preparation quantification procedure... 

The geological MPI-DING references glasses prepared and characterized by Jochum et al. employing several analytical techniques as described in Chapter 6 are recommended to improve possible quantification procedures for in situ microlocal analysis.4,12... 

QUANTIFICATION. The addition of the internal standard (10 yg) to the urine before extraction is necessary for the quantification procedures. Known amounts of amphetamine and diphenylamine in the range 0-5 yg are chromatographed and calibration curves are plotted for peak area (y axis) versus concentration (x axis). 

Street (34) developed an "on column" derivative formation technique using N,0-bis (trimethylsilyl) acetamide (BSA). A few microliters of BSA are drawn into a 10-yl syringe followed by several microliters of extract to be chromatographed. The whole is injected onto the column with the resultant formation of and separation of the derivatives. This procedure is recommended for the formation of methyl and trimethylsilyl derivatives in qualitative determinations, and the separation of nonderivatized barbiturates for quantification procedures. 

Several different quantification procedures for vitamin A have been described in the literature, some using retinol directly as a standard and some using retinyl acetate, which is converted to retinol by saponification. The latter approach is generally preferred, because crystalline all-trans-retinyl acetate is commercially available in high purity and is free from cis isomers. Commercial sources of retinol are oily preparations and are at best only about 70% pure. There are two ways of preparing a retinol standard from retinyl acetate. 

Many research experiments have been conducted to determine the presence and quantity of SPA in foods. As literature reviews show, a particular emphasis has developed in the recovery procedures for antioxidants and in quantification procedures, including colorimetric methods, spec-trophotometric methods in the UV region, paper and thin-layer chromatographic methods, gas... 

Three spectrophotometric procedures are given in the AOAC compendium of methods (960.22, 962.13 and 967.11) for the analysis of caffeine, all of which have an extraction stage followed by a quantification procedure. There is also an HPLC method, discussed earlier, which was designed to measure saccharin, benzoic acid and caffeine at the same time (AOAC, 978.08). Again, the HPLC method, EN 12856 1999 (Anon, 1999a), can be used for the analysis of caffeine, but this analyte was not included in the collaborative study. 

ICP-MS allows different quantification procedures to be used depending on the accuracy and precision required. The suitability of the semiquantitative mode of analysis of an ICP-MS instrument for multi-element characterization of fortified and table wines was evaluated by Almeida and Vasconcelos [83]. As compared to... 

To summarize this section, we present HREELS as a new spectroscopy, with attributes similar to the IR ones, but with a very high surface sensitivity, and a different quantification procedure. 

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