Standard addition method, application

This experiment demonstrates the application of the generalized standard additions method for the analysis of mixtures of K2Cr207 and KMn04. 

The trade-offs between direct calibration and standard addition are treated in Ref 103. The same recovery as is found for the native analyte has to be obtained for the spiked analyte (see Section 3.2). The application of spiking to potentiometry is reviewed in Refs. 104 and 105. A worked example for the application of standard addition methodology to FIA/AAS is found in Ref 106. Reference 70 discusses the optimization of the standard addition method. 

There are a few requirements for the application of the standard addition method. The analytical results have to be corrected for blank. Otherwise we would add the blank value to our sample content. Since we are using linear regression we need a linear relationship between signal and concentration. As stated above the homogeneity of variances is also a prerequisite for linear regression. We want to divide our sample into several sub-samples and spike them with known amounts of analyte. This means that we need to divide the sample homogeneously and to precisely add the analyte. 

Q. What are the advantages and disadvantages of the standard addition method for the above applications ... 

Table 41 Application of the H-point standard addition method to a mixture of a commercial madder pigment (Kremer, 0.03325 g) plus silica (0.25836 g) and moiin (0.02486 g), this last acting as an auxiliary reference compound... 

Data in Table 4.2 corresponds to the application of the H-point standard addition method to a mixture of a commercial madder pigment diluted with silica, using morin as a reference compound. Calculations were performed by taking m/niR = 10.246, using square-wave voltammetric currents measured for sample-modified PIGEs in contact with an acetate buffer of pH 4.90. Linear plots of ii/ip(R) (squares) and i2/ip(R) (solid squares) vs. mA/mp for additions of purpurin are shown in Fig. 4.17. 

Bosch F, Campins P (1988) H-pomint standard additions method. Part 1. Fundamentals and application to analytical spectroscopy. Analyst 113 1011-1016. 

Domenech A, Domenech-Carbo MT, Gimeno JV, Bosch F (2006) H-point standard addition method apphed to solid state stripping voltammetry. Application to the determination of lead and tin in archaeological glazes. Anal Bioanal Chem 385 1552-1561. 

The method of complete electrolysis is also important in elucidating the mechanism of an electrode reaction. Usually, the substance under study is completely electrolyzed at a controlled potential and the products are identified and determined by appropriate methods, such as gas chromatography (GC), high-performance liquid chromatography (HPLC), and capillary electrophoresis. In the GC method, the products are often identified and determined by the standard addition method. If the standard addition method is not applicable, however, other identification/determination techniques such as GC-MS should be used. The HPLC method is convenient when the product is thermally unstable or difficult to vaporize. HPLC instruments equipped with a high-sensitivity UV detector are the most popular, but a more sophisticated system like LC-MS may also be employed. In some cases, the products are separated from the solvent-supporting electrolyte system by such processes as vaporization, extraction and precipitation. If the products need to be collected separately, a preparative chromatographic method is use-... 

S. Euan, H. Pang and R. S. Houk, Application of generalized standard additions method to inductively coupled plasma atomic emission spectroscopy with an echelle spectrometer and segmented-array charge-coupled detectors, Spectrochim. Acta, Part B, 50(8), 1995, 791-801. 

Ag, At, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sb, Se, Tl, V, and Zn ETAAS Metals are measured by ETAAS using the manufacturer s recommended conditions and an injection volume of 20 pL Applicable to surface, ground, tap, and waste water. A high CE concentration interferes. To minimize the matrix effect, the chemical modification, standard addition method, and background correction systems may be used. 105... 

In the standard addition method, the sample is analyzed first. A small, known amount of a known compound, thought to be in the sample, is then added to the sample, and the mixture is reanalyzed. If a quantitative increase is obtained in the peak of the compound corresponding to the standard, the compound representing the peak is tentatively identified. The technique of spiking is applicable provided that the sample is known to contain certain components appropriate standards can then be added to enable each peak to be identified. If the identities of the components in the sample are totally unknown, the spiking technique is inappropriate, and additional analytical or comparative techniques will be required. 

A standard addition method has been studied for use with second-order data [87], The specific application investigated was analysis of trichloroethylene in samples that have matrix effects caused by an interaction with chloroform. 

Booksh, K., Henshaw, J.M., Burgess, L.W., and Kowalski, B.R., A second-order standard addition method with application to calibration of a kinetics-spectroscopic sensor for quantitation of trichloroethylene, J. Chemom., 9, 263-282, 1995. 

L. F. Almeida, V. Lacerda Martins, E. C. Silva, P. N. Teles Moreira, M. C. Ugolino Araujo, Implementation of an automatic standard addition method in a flow-batch system application to copper determination in an alcoholic beverage by atomic absorption spectrometry, Anal. Chim. Acta, 486 (2003), 143-148. 

Price [67] has reviewed the application of atomic absorption to a variety of plating solutions. Iron, lead and zinc are reported as the main impurities in cyanide copper-plating baths which may contain up to 200gl 1 of copper sulphate a twenty-fold dilution of the sample for trace determination is recommended. Nickel baths may contain 60 gl 1 of nickel and it may be necessary to monitor copper, zinc, iron, lead, chromium, calcium and magnesium at the ppm level. The standard addition method is probably best for such an application. Zinc has been extracted with trioctylamine-hydrochloride when present in the range 0.03—10pgml-1 in a nickel plating solution [68]. The zinc was re-extracted back into 1M nitric acid for... 

The most important advantage of this calibration approach is that each calibration solution contains the analyte in the environment of all sample components, including potential interferents. Thus, if the calibration dependence is distorted as a result of interferents, there is still a chance to reconstruct it accurately by means of the calibration graph. From this point of view, the standard addition method is one way to eliminate (or rather compensate for) the interference effect. Furthermore, it gives a chance to compensate for the effects of all interferents, independently of their kind, number, and concentration in the sample. This feature supports application of the standard addition method to trace analysis. 

There is one more, very important and relatively simple method to use when an interference effect is difficult to explore but its occurrence is probable and poses a threat to the reliability of analytical results. This refers to the case when an analyzed series of samples have similar chemical composition (at least in terms of the composition of interferents) and the determined component is present in all samples in a similar quantity. In this situation, the standard addition method can be used for analysis of one selected sample and the constructed calibration graph employed for interpolative determination of analyte in the remaining samples. This combined procedure is depicted in Fig. 3.16. Thus obtained results are, as a mle, more accurate than those obtained after application of the set of standards method to all the samples. In addition, the analyses are conducted faster than when all the samples are analyzed using the standard addition method. 

The dilution methods of sample preparation of petroleum fractions for metal analysis are limited to the concentration of metals in each fraction. The dilution method is applicable for routine monitoring crude and lubricating oils, providing the concentration of metals is quantifiable using standard calibration curve, internal standard or standard addition method. The method is unsuitable for low concentration of metals especially as those can build up accumulatively, causing poisoning in all catalytic fractionation plants. The low concentration of toxic metals may be undetected by dilution methods and may escape monitoring if a more sensitive method is not used. 

Spreadsheet Summary In Chapter 12 ot Applications of Microsoft Excel in Analytical Chemistry, we investigate the multiple standard additions method for determining solution concentration. A least-squares analysis of the data leads to the determination of the concentration of the analyte as well as the uncertainty of the measured concentration. 

What is(are) advantage(s) of the standard addition method What minimum condition is needed for the successful application of this method ... 

When standard reference materials and different analytical methods are not applicable, the standard-addition method may prove useful. Here, in addition to being... 

Analysis of synthetic solutions using a diode array spectrophotometer. This application of SAM involved gradient exploitation. The sample was kept undiluted ("infinite volume situation") and the standard zone was added by stream confluence with two different standard zones, multi-parametric determinations involving the generalised standard addition method were achieved [354],... 

The standard-addition method, described in Section lD-3, is equally applicable to potentiometric determinations. In this method, the potential of the electrode system is measured before and after addition of a small volume (or volumes) of a standard to a known volume of the sample. We assume that this addition does not change the ionic strength and thus the activity coefficient yx nf fhe analyte. We further assume that the added standard does not significantly alter the junction potential. 

The standard-addition method has been applied to the determination of chloride and fluoride in samples of commercial phosphors. In this application, solid-state indicator electrtKies for chloride and fluoride were used in conjunction with a reference electrode the added standard contained known quantities of the two anions. I he relative standard deviation for the measurement of replicate standard samples was 0.7% for fluoride and 0.4% for chloride. In routine use with real samples, the standard-addition method yielded relative standard deviations of l.l k) for fluoride and 0.8% for chloride. When similar samples were ana-Ivred bv the usual electrode calibration methods, the... 

ETAAS. In ETAAS atomization takes place in an electrothermal atomizer which is heated to the appropriate temperature programme. The detection limits of the method are about two or three orders of magnitude better than FAAS. It is applicable to about 40 elements but generally for about 20 elements detection limits at the ng and pg level can be reached. Commensurable or better sensitivities have only INAA, ICP-MS and stripping voltammetry. Therefore ETAAS is widely used for environmental analysis. However the method suffers from serious interferences leading to systematic errors due to thermochemical processes in the atomizer. Background absorption is also a potential source for systematic errors. Spectral interferences are additive and cannot be corrected by the popular standard addition method. ETAAS is also not free of memory effects for refractory elements. 

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