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Arsenic, analytical calibration

The following procedure has been recommended by the Analytical Methods Committee of the Society for Analytical Chemistry for the determination of small amounts of arsenic in organic matter.20 Organic matter is destroyed by wet oxidation, and the arsenic, after extraction with diethylammonium diethyldithiocarbamate in chloroform, is converted into the arsenomolybdate complex the latter is reduced by means of hydrazinium sulphate to a molybdenum blue complex and determined spectrophotometrically at 840 nm and referred to a calibration graph in the usual manner. [Pg.683]

The set of possible dependent properties and independent predictor variables, i.e. the number of possible applications of predictive modelling, is virtually boundless. A major application is in analytical chemistry, specifically the development and application of quantitative predictive calibration models, e.g. for the simultaneous determination of the concentrations of various analytes in a multi-component mixture where one may choose from a large arsenal of spectroscopic methods (e.g. UV, IR, NIR, XRF, NMR). The emerging field of process analysis,... [Pg.349]

Figure S.4 shows a calibration graph of arsenic concentrations obtained by using a Perkin Elmer 2100 atomic-absorption system bnked to a P.S. Analytical hydride/vapour generator (PSA 10.003). An electrically heated tube has been used in this work and the spectral source was an electrodeless discharge lamp. Alternatively, a flame-heated tube can be used. Figure S.4 shows a calibration graph of arsenic concentrations obtained by using a Perkin Elmer 2100 atomic-absorption system bnked to a P.S. Analytical hydride/vapour generator (PSA 10.003). An electrically heated tube has been used in this work and the spectral source was an electrodeless discharge lamp. Alternatively, a flame-heated tube can be used.
Apart from the fact that some of the analyte elements were not detected at their normal concentration levels in urine, the main feature of the analytical results was their overall consistency. The results from the method of additions agreed well with those from the calibration approach and, in either case, the results obtained for the dilute, normal, and concentrated sample solutions also were in good agreement with each other. With the exception of arsenic and titanium, the results for the two methods and for the three urine concentrations were within one detection-limit concentration of each other for all of the elements. Although it has been noted (25) that detection-limit values are "inherently imprecise numbers and that detection-limit concentrations "can only be detected,. . . , and not measured quantitatively, the consistency of the analytical results indicates that the backgroimd correction scheme was effective for elimination of the eflFects of stray light and recombination radiation. As noted earlier, the ratios of net analyte line to net internal reference line intensities were used to decrease the eflFects of sample-to-sample variations in total dissolved solids content. [Pg.108]

The amount of arsenic in each sample was determined by using an instrument called a spectrophotometer, to measure the intensity of the red color formed in the cuvettes. As discussed in Chapter 26, a spectrophotometer provides a number called absorbance that is directly proportional to the color intensity, which is also proportional to the concentration of the species responsible for the color. To use absorbance for analytical purposes, a calibration curve must be generated by measuring the absorbance of several solutions that contain known concentrations of analyte. The upper part of Figure lF-2 shows that the color becomes more intense as the arsenic content of the standards increases from 0 to 25 parts per million (ppm). [Pg.14]

A very important part of all analytical procedures is the calibration and standardization process. Calibration determines the relationship between the analytical response and the analyte concentration. Usually this is accomplished by the use of chemical standards. In the deer kill case study of Feature 1-1, the arsenic concentration was found by calibrating the absorbance scale of a spectrophotometer with solutions of known arsenic concentration. Almost all analytical methods require some type of calibration with chemical standards. Gravimetric methods (see Chapter 12) and some coulometric methods (see Chapter 22) are among the few absolute methods that do not rely on calibration with chemical standards. Several types of calibration procedures are described in this section. [Pg.192]

An external standard is prepared separately from the sample. By contrast, an internal standard is added to the sample itself. The arsenic standards used to calibrate the absorbance scale of the spectrophotometer in Feature 1-1 were external standards used in the determination of arsenic. External standards are used to calibrate instruments and procedures when there are no interference effects from matrix components in the analyte solution. A series of such external standards containing the analyte in known concentrations is prepared. Ideally, three or more such solutions are used in the calibration process. In some routine analyses, however, two-point calibrations can be reliable. [Pg.194]

In the split/pool method of combinatorial synthesis, mixtures of compounds are made that are difficult to characterize. The LC/CLND of a nominally equimolar pool (based on nitrogen) should yield equal-sized chromatographic peaks of compounds. In the early stages of a lead development project, weighable quantities of authentic pure samples of a compound are not available, and yet quantitative measurements such as IC50, solubility, or plasma stability need to be made. LC/CLND can be used to calibrate solutions made from submilligram synthetic samples. LC/CLND is an important new technique to add to the arsenal of the organic analytical laboratory. [Pg.240]

Wiedemann, B., Alt, H.C., Meyer, J.D, Michelmann, R.W, Bethge, K. (1999) Spark source mass spectrometric calibration of the local vibrational mode absorption of carbon in gallium arsenide on arsenic sublattice sites. Fresenius Journal of Analytical Chemistry, 364,768-771. [Pg.931]


See other pages where Arsenic, analytical calibration is mentioned: [Pg.1828]    [Pg.354]    [Pg.390]    [Pg.463]    [Pg.1828]    [Pg.1609]    [Pg.102]    [Pg.29]    [Pg.144]    [Pg.280]    [Pg.293]    [Pg.472]    [Pg.647]    [Pg.52]    [Pg.351]    [Pg.57]    [Pg.264]   
See also in sourсe #XX -- [ Pg.89 , Pg.90 ]




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Analytical Calibration

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