Digestion dry ashing

Dissolution of sample Extent of dissolution to fit calibration range, or limit of detection Complex formation, extraction, wet digestion, dry ashing, fusion, combustion... 

Dabeka RW and Lacroix GMA (1987) Total arsenic in foods after sequential wet digestion, dry ashing, coprecipitation with ammonium pyrrolidene dithio-carbamate, and graphite-furnace atomic absorption spectrometry. J Assoc Off Anal Chem 70 866-870. 

The objective of the sample preparation stage is usually to bring all available means into play in order to determine as readily as possible the elements of interest. First, these means have to ensure the transformation and simplification of the matrix (mineralization wet digestion, dry ashing). Second, they should convert the sample to a form compatible with the measurement technique utilized (generally a dissolution). 

The apphed pretreatment techniques were digestion with a combination of acids in the pressurized or atmospheric mode, programmed dry ashing, microwave digestion and irradiation with thermal neutrons. The analytical methods of final determination, at least four different for each element, covered all modern plasma techniques, various AAS modes, voltammetry, instrumental and radiochemical neutron activation analysis and isotope dilution MS. Each participating laboratory was requested to make a minimum of five independent rephcate determinations of each element on at least two different bottles on different days. Moreover, a series of different steps was undertaken in order to ensure that no substantial systematic errors were left undetected. 

Dabeka, R. W. and McKenzie, A. D. (1991). Graphite furnace atomic absorption spectromet-ric determination of selenium in foods after sequential wet digestion with nitric acid, dry ashing and coprecipitation with palladium. Can. J. Appl. Spectrosc. 36,123-126. 

Soil Dry ash, digest in HNO3/HCI, anion exchange, Ca-oxalate and Fe (OH)2 coprecipitation, anion exchange, electrodeposition a -Spectroscopy 27 pCi/g 75-92% Sanchez and Singleton 1996... 

Applications A limited number of papers refer to the use of AAS in relation to polymer/additive deformulation. Elemental analysis of polymers and rubbers by AAS may be carried out after dissolution in an organic solvent (Table 8.21), after oxidative wet digestion (Table 8.12), after dry ashing (Table 8.22) or directly in the solid state (Table 8.23). 

Table 8.22 shows some rubber analyses by FAAS after dry ashing. The concentration of Rh in polymers was measured by FAAS [128], The accuracy of 10-20% was in agreement with a dissolution procedure the precision obtained for direct solid analysis was between 10 and 20 %. Due to the relatively high analyte content of lead in paint, the determination is mostly performed by FAAS. Typical digestion procedures include dry ashing, wet and microwave digestion. 

Soil Drying of sample, dry ashing, digestion with acid, and dilution with water AAS 2 pg/g 79-103 Beyer and Cromartie 1987... 

Grains, milk mussel, fish Bomb digestion of sample with acid and heat or digestion with acid and dry ashing dissolution in acid dilution with water GFAAS 20 pg/g (bomb) 5 pg/g (dry ash) No data 85-107 75-107 Ellen and Van Loon 1990... 

Feldman and co-workers117) described a procedure for determining as little as 10 ppb of chromium in serum. The normal level is 30 ppb. At least 2 ml of serum are digested or dry ashed and treated with not permanganate to oxidize chromium to chromium(VI). The chromium(VI) is extracted from 3M HC1 into 5 ml MIBK in the cold. This method has been used to measure chromium levels in studies relating this element to diabetes. Thousands of analyses have been performed. Devoto (198) dry ashed 10 ml of blood and extracted the chromium with 5 ml of 10 % tributyl phosphate in MIBK. Recently, Feldman 119) has determined... 

One litre of unfiltered water was rolled with a carbon sachet and 10g NaCI for 7 days. The carbon was then dried, ashed, digested in aqua regia and analysed by ICP-MS, for Ag, Au, Pd, and Pt. Field and analytical blanks, as well as duplicates were used in all analyses to ensure accuracy (Gray etal. 2001). 

Olsen et al. [71] have reviewed the determination of inorganic, organic and total phosphorus in soil and sediments. Determination of total phosphorus in aqueous samples commonly involves a hot acid oxidation type digestion procedure, although various other dry-ashing, fusion and UV... 

Usually, samples are presented for analysis as liquids. Thus, solid samples must be dissolved. Analytical or ultra-high-purity grade reagents must be used for dissolution to prevent contamination at trace levels. Certain volatile metals (e.g. cadmium, lead and zinc) may be lost when dry ashing, and volatile chlorides (e.g. arsenic and chromium) lost upon wet digestion. It is particularly easy to lose mercury during sample preparation. Appropriate steps must be taken in the choice of method of dissolution, acids and conditions (e.g. whether to use reflux conditions) to prevent such losses. 

The laboratory sample is usually dissolved for analysis. It is important to dissolve the entire sample, or else we cannot be sure that all of the analyte was dissolved. If the sample does not dissolve under mild conditions, acid digestion or fusion may be used. Organic material may be destroyed by combustion (also called dry ashing) or wet ashing (oxidation with liquid reagents) to place inorganic elements in suitable form for analysis. 

Digestion of organic material is classified as either dry ashing, when the procedure does not include liquid, or wet ashing, when liquid is used. Occasionally, fusion with Na202 (called Parr oxidation) or alkali metals may be carried out in a sealed bomb. Section 27-4 discussed combustion analysis, in which C, H, N, S, and halogens are measured. 

The effects of soil sample preparation procedures for the determination of chromium in soils have been reported [38]. The optimum conditions included the use of an homogeneous sample with a mass of less than 4 kg, a grain diameter of less than 0.25 mm, digestion with a solution of nitric acid plus perchloric acid (3 2) and hydrochloric acid after dry ashing, with the addition of 1% lanthanum or 1% ammonium chloride to eliminate interferences. 

Type of sample Determinand Dry ash acid digestion reagent Analytical finish Reference... 

In an official method [83] for determining zinc in plant material, the sample is digested with perchloric acid 60% nitric acid 70%, m/v 1 4, followed by 2 M hydrochloric acid. Alternatively, the plant material is dry ashed and the residue dissolved in 6 M hydrochloric acid. The extract is evaluated by AAS at the 213.9 nm emission line. See also Sect. 7.34.1,7.34.4 and 7.34.7. 

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