Acid digestions, procedure for

Acid digestion procedure for subsequent atomic spectrometric analysi s... 

Alvarado, J., Leon, L.E., Lopez, F., Lima, C. Comparison of conventional and microwave wet acid digestion procedures for the determination of iron, nickel and vanadium in coal by electrothermal atomization atomic absorption spectrometry. J. Anal. At. Spectrom. 3, 135-138 (1988)... 

F. Sanchez Rojas, C. Bosch Ojeda and J. M. Cano Pavon, Experimental design in the optimisation of a microwave acid digestion procedure for the determination of metals in biomorphic ceramic samples by inductively coupled plasma mass spectrometry and atomic absorption spectrometry, Microchem. J., 2010, 94(1), 7-13. 

Y. Malaxechevarria and E. Millan, Application of experimental design to the optimisation of a wet acid digestion procedure for Cd determination in plastic materials by atomic absorption spectrometry, Spectrosc. Lett., 2009, 42(1), 12-19. 

Selenium (IV) adsorbed as selenotrisulfate was then eluted from the column with either 0.1 M penicillamine or 0.1M cysteine. The eluate was then subjected to an acid digestion procedure to reduce selenium to the tetravalent state with diaminonaphthalene for fluorometric determination. Approximate agreement with the tellurium coprecipitation method was obtained. The application of both methods to the analysis of estuarine waters permitted the separate determination of both selenium (IV) and selenium (VI), since the tellurium coprecipitation methods did not differentiate between the two species. 

Thallium has been determined in 10 ml of ashed serum or in urine by extracting with sodium diethyldithiocarbamate into MIBK n°). More recently, Savory and co-workers 1131 described a wet digestion procedure for 50 ml of urine or 5 ml of serum in which the thallium is separated by extracting the bromide into ether, evaporating the ether and then taking up in dilute acid for aspiration. As little as 0.1 ppm is determined in urine. Curry et al.114) determined less than 1 ng of thallium in 200 /d of urine by using the tantalum sample boat technique. The sample in the boat is dried by holding the boat 1 cm from the flame and then it is inserted into the flame where it is vaporized. A similar procedure is used for >3 ng of thallium in 50-100/al of blood, except that the blood is preashed with 3 drops of nitric acid. Since the tantalum boat method is susceptible to interelement interferences, the method of standard additions is used for calibration. 

Nelson and Sommers [44] have described a Kjeldahl digestion procedure for the determination of total nitrogen in soils in which the sample is digested with sulphuric acid using a selenium catalyst. The digest is steam distilled with sodium hydroxide and ammonia titrated with 3.5mM sulphuric acid. Various other workers have discussed the application of Kjeldahl digestion to the determination of total nitrogen in soils [45-47]. 

Dobolyi and Bidlo [76] have described methods for the determination of phosphorus in lake sediments. Shulka et al. [75] investigated the interference by arsenic in the perchloric acid digestion procedure of Murphy and Riley [85] for the determination of phosphorus in sediments. Arsenite concentrations up to 20pg did not interfere but arsenate interfered. Between 1 and 45 pg arsenic g"1 was extracted from a lake sediment and in all cases the error in the determination of phosphorus due to the presence of arsenic was less than 1%. 

The acid digestion procedure described above for biological tissues. Crock and Lichte [135] recently described a similar procedure, involving hydrofluoric as well as nitric, perchloric and sulphuric acids, for dissolution of geological materials prior to arsenic and antimony determination by atomic absorption spectrometry. 

Floyd and Sommers [142] evaluated a simple one-step digestion procedure for extracting total mercury from soils. The sample was digested with concentrated nitric acid and 4N potassium dichromate for four hours at 55 °C and the mercury in the extract determined by flameless atomic absorption spectrometry. The method can be applied to soils containing up to 20% organic matter. 

Interference from anions, originating from acid digestion procedures, is a significant factor in temperature-programmed GFAA analysis. To reduce this interference, nitric acid is preferred over any other acids for the digestion or solubilization steps. If the addition of another acid is necessary, a minimum amount is always used. This particularly applies to hydrochloric and, to a lesser extent, to sulfuric and phosphoric acids used in some digestion procedures. 

Similar inconsistencies have been encountered in the determination of other elements such as selenium [125,133], arsenic [118,130], copper [119,123] and zinc [120,122]. On the other hand, methods for the determination of mercury are slightly more consistent, with many workers using a closed-vessel nitric acid digestion procedure. Good results have thus been obtained with pig kidney [124,141], mussel tissue [138], cod muscle [137], citrus leaves [136], pine needles [136], albacore tuna [131] and fish tissue [124], among others. 

Heilman, U., Wernstedt, C., Gonez, J., and Heldin, C.-L, Improvement of an In-gel digestion procedure for the micropreparation of internal protein fragments for amino acid sequencing, AmZ. Biochem., 224, 451 55, 1994. 

Use of RAS procedures results in specific values using specific procedures. The user of the data must know the procedures used to be able to give the correct interpretation. An example of this is the digestion procedure for water used by the CLP (4). Five possible digestion procedures for waters are available or proposed (4, 11, 12). These are listed in Table IV as Dissolved, Acid Soluble, Total Recoverable, EPA Total, and CLP Total. 

Whenever the direct technique is applied to known compounds, the validity must be established. For example, the additive methylcyclopenta-dienyl manganese tricarbonyl may be too stable to be analyzed by direct HVAA without pre-atomization losses. Some work has suggested that losses of this compound occur even in acid digestion procedures (4). No studies were made on this compound as part of the Project. 

Kotz etal. (1972, Decomposition of biological materials for the determination of extremely low contents of trace elements in limited amounts with nitric acid under pressure in a Teflon tube) Hartstein et al. (1973, Novel wet-digestion procedure for trace-metal analysis of coal by atomic absorption) Jackson etal. (1978), Automated digestion and extraction apparatus for use in the determination of trace metals in foodstuffs) Campos etal. (1990, Combustion and volatilization of solid samples for direct atomic absorption spectrometry using silica or nickel tube furnace atomizers) Erber et al. (1994, The Wickbold combustion method for the determination of mercury under statistical aspects) and Woit-tiez and Sloof (1994, Sampling and sample preparation). 

Eriksen (1979) compared different wet digestion procedures for voltammetric stripping analysis of urine and preferred the use of a mixture of nitric, sulfuric, and perchloric acids. Satisfactory recovery (92-100%) of lead and cadmium from spiked samples was obtained. An effective procedure based on a rapid (20 min.) digestion of freeze-dried urine samples coupled with voltammetric analysis was reported (Golimowski et al., 1979). 

Atomic spectrometry generally requires prior dissolution of the sample, which can be carried out with either acids or organics solvents, but in some cases necessitates destroying the matrix by means of a wet acid treatment or a dry digestion. This can be a serious drawback, but the new strategies for sample preparation, based on the use of microwave-assisted digestion procedures for sample dissolution and... 

FAAS is a fast technique which is easy to automate, particularly when FI techniques are used, and is hence well suited for routine applications. However, FAAS is not directly applicable to trace element determination, particularly in tissue samples, which are often significantly diluted in the acid digestion procedure. Because of its simplicity, FAAS is nevertheless often the detector of choice for various preconcentration procedures. It is particularly attractive in combination with online preconcentration and separation using FI techniques (see Sec. 5.2 and 5.3). 

Another variation on the acid digestion procedure used a mixture of hydrofluoric acid, nitric acid, and perchloric add in a sealed Teflon bomb heated at 150°C for 4 h... 

Oxidizing mixtures comprised mainly of combinations of different acids and sometimes addition of oxidizers to mineral acids are most commonly used in wet digestion procedures for plastic samples. Such an approach is used to incorporate the individual actions of the constituting mixture components in order to achieve effective sample solubilization. A typical example in this respect is a HNO3/HP mixture used for digestion of a plastic... 

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