Critical comparison of wet and dry digestion procedures for trace metal analysis of meat and fish tissues

The efficiency of four methods of digestion was evaluated for trace metal analysis of pork meat and carp fish tissues. Two methods of dry and two methods of wet ashing were compared in terms of calculated variances. Mixtures of HCl+HNO₃ were applied for wet ashing of the samples at 100 °C, while dry ashing with or without H₂SO₄ at 450 °C were the alternative methods. The digests were subsequently analysed for Pb, Cd, Cu and Zn by graphite furnace atomic absorption spectrometry. Analysis of variance and Student's t-test were performed separately for meat and fish analytical results. Wet digestion with a (1+1) mixture of HCl+HNO₃ has given better recovery and repeatability for almost all metals than a (9+1) mixture of HCl+HNO₃. Also between the dry ashing methods, the use of H₂SO₄ has given better results than ashing of the tissues without H₂SO₄.     

A decomposition procedure for the determination of arsenic in marine samples

The use of wet and dry ashing procedures to decompose marine biological tissues and to degrade organoarsenic compounds to inorganic arsenic for analysis by zinc-column arsine generation and atomic-absorption spectrophotometry was investigated. Wet ashing with nitric, sulphuric and perchloric acids (10:2:3 v/v) released the largest percentage of arsenic from fish tissue and quantitatively degraded methylated and other organoarsenic compounds to inorganic arsenic. The arsenic concentrations found when standard reference materials were ashed with this acid mixture were in agreement with the certified values.     

Arsenic determination in certifiable color additives by dry ashing followed by hydride generation atomic absorption spectrometry

The preparations of digested samples of certifiable color additives by dry ashing and wet digestion for arsenic analysis by hydride generation atomic absorption spectrometry (AAS) were compared. The dry ashing technique was based on the preparation used in ASTM D4606-86 for determination of As and Se in coal. The acid digestion method used nitric and sulfuric acids heated by microwaves in sealed vessels. The digested color additives were analyzed for As by using hydride generated from sodium borohydride mixed with the acidified solution on a flow injection system leading to an atomic absorption spectrometer. Dry ashing was preferable to wet digestion because wet digestion yielded poor recoveries of added As. Dry ashing followed by hydride generation AAS gave determination limits of 0.5 ppm As in the color additives. At a specification level of 3 ppm As, the precision of the method using dry ashing was +/- 0.4 ppm (95% confidence interval).     

Cadmium losses on wet and dry ashing of plant materials

Cadmium losses on wet and dry ashing were studied using tomato leaves with metabolized¹⁰⁹Cd radiotracer. The most appreciable Cd losses (up to 35%) occured when sulphuric acid was used on wet ashing due to Cd retention in the CaSO₄ precipitate formed. Only trace amounts of Cd were retained in a silicaceous precipitate resulting from wet ashing in the absence of sulphuric and hydrofluoric acids in the decomposition mixtures employed. Small Cd losses (up to 7%) were observed on dry ashing in the air in open systems at temperatures not exceeding 500°C. Cd losses increased, however, to 30% when the final ashing temperature was raised to 900°C. Incorporation of the¹⁰⁹Cd radiotracer into various parts of tomato plants and its distribution between soil and the plants are also briefly reported.     

Neutron activation analysis of noble metals in vegetation

Detection limits are presented for the platinum metals in vegetation for different neutron activation analysis conditions, namely, short irradiation, cyclic and long irradiations both thermally and epithermally. These detection limits for instrumental neutron activation analysis are compared with those using preconcentration technique—dry ashing and fire assay and post irradiation separation of the platinum metals using Srafion NMRR in exchange resin. The results are evaluated for plant material and it is concluded that dry ashing followed by cyclic, epithermal irradiation for rhodium and palladium and long, thermal irradiations for osmium, platinum, iridium and ruthenium enable these elements to be detected in plants at background levels.     

虾粉中总砷测定方法的探讨

用氢化物原子荧光光度法测定虾粉中总砷含量时,对干法灰化、湿法消解、微波消解3种样品处理方法对虾粉中砷元素测定结果的影响进行了比较。通过试验确定了最佳消解条件。砷元素浓度在0~10μg/L的范围内与荧光强度呈线性关系,线性相关系数r=0.999 6,检出限为0.2μg/L。比对结果表明,干法灰化适合于测定虾粉中总砷的含量,湿法消解测定总砷的含量偏低,微波消解不适合测定虾粉中总砷的含量。采用干法灰化-氢化物原子荧光光度法测定虾粉中总砷含量,加标回收率为76.2%~106.0%。     

火焰原子吸收法测定油画颜料中铅含量

采用干灰化法、湿氧化A法和B法分别对油画颜料进行消解后用原子吸收火焰法测定其中的铅含量.通过分析比较3种消解方法测定的结果,发现采用湿氧化法优于干灰化法,湿氧化A法优于B法.采用湿氧化A法对油画颜料进行加标处理后,加标回收率在90%-105%范围,表明采用该方法测定油画颜料中的铅含量是可信的.     

Welche Platinmengen gelangen bei der Vorbereitung biologischer Substanzen zur Spurenelementbestimmung nach deren Veraschung in Platinschalen in die L?sung?

Zusammenfassung Es wird berichtet, welche Platinmengen beim Veraschen biologischer Substanzen im Muffelofen bei verschiedenen Temperaturen und anschließendem Aufnehmen und Erhitzen mit verschiedenen Säuren aus Platinschalen gelöst werden. Ferner wird aufgezeigt, wie die Veraschung und das In-Lösung-Bringen der Aschen durchgeführt werden sollte und welche Platinmengen eine Störung bei einigen Methoden zur Bestimmung von Spurenelementen verursachen können.

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Which amounts of platinum are dissolved in the preparation of biological substances for the determination of trace elements after ashing in platinum dishes?

It is shown, which amounts of platinum are dissolved from platinum dishes when ashing biological materials in a muffle furnace at different temperatures and dissolving the ashes with different acids. Furthermore it is shown, how these procedures must be carried out and which platinum amounts cause errors in the determination of trace elements.

     

Preparation of conducting electrodes from biological samples for multi-element trace analysis by spark-source mass spectrometry or emission spectrometry

Four decomposition procedures frequently used for biological material (dry ashing, open wet digestion, wet digestion in a teflon bomb and low-temperature ashing) are optimized for the conversion of biological samples to conducting electrodes suitable for multi-element trace determinations by spark-source mass spectrometry or emission spectrometry. The optimized procedures are evaluated with respect to contamination, retention and preconcentration of the trace elements, homogeneity of the electrodes and precision of the final results. Both dry-ashing methods are prone to losses by volatilization; simple dry ashing suffers from contamination problems during electrode preparation. Wet digestion gives better precision; digestion with nitric/sulfuric acids in an open flask is the method of choice for most elements being simpler and giving lower blanks than the bomb method.     

Graphite furnace atomic absorption spectrometry for the analysis of biological materials

Graphite furnace atomic absorption spectrometry (GFAAS) is used to analyze a variety of biological materials. Conventional single element determinations as well as multielement determinations made on the SIMAAC are discussed. Four sample preparation methods were used to prepare samples for GFAAS including: direct analysis of liquids, wet ashing, dry ashing, and slurry preparation. Results from analyses of a wide variety of materials are presented.     

An apparatus for the wet ashing of organic matter

An apparatus for the wet ashing of organic material is described. It makes possible the ashing of large quantities of organic matter with pure, ash-free reagents and the determination of various constituents in the samples. This procedure is most useful for the determination of trace elements. It has mainly been used so far for the determination of small amounts of sulfur.     

矿区植物重金属元素测定的两种前处理方法比较

分别采用酸消解法和干灰化法处理16种矿区植物,并用原子吸收分光光度法测定其中的Mn、Cd、Cr和Zn的含量。结果表明:除Cd外,两种处理方法对Mn、Cr、Zn的测定结果有明显影响。测定植物组织Cd时,两种处理方法都可采用;测定Mn、Cr元素,采用酸消解法较为合适;测定Zn则宜采用干灰化法,并可适当延长木质部分(根、茎)的灰化时间。     

Determination of traces of molybdenum in foods by electrothermal atomic absorption spectrometry

Low levels of molybdenum in different food samples were determined by atomic absorption spectrometry with electrothermal atomization after destruction of organic matter using four different methods, involving dry ashing at 600°C, wet digestion with heating with nitric/sulphuric and nitric/sulphuric/perchloric acid mixtures or direct extraction with dilute hydrochloric acid. In all cases the working conditions, reproducibility, precision and accuracy were investigated. The dry ashing method was generally the optimum destruction method.     

Comparison of dry and wet ashing procedures for cadmium and iron determination in biological material by atomic-absorption spectrophotometry

A possible loss of cadmium and iron from the sample during dry ashing of the kidney, liver or carcase was examined by the radioactive isotope labelling technique. Cadmium-115 m or iron-59 was administered to rats 4-7 days before the rats were killed and samples collected. Dry ashing in different types of dishes and wet digestion with nitric acid were compared. There was no loss of cadmium or iron by volatilization during dry ashing at 600 degrees or 450 degrees respectively, but a significant amount of iron was bound on glass or porcelain crucibles. Storage of ashed and dissolved samples (in 10 nitric acid) did not show any change of cadmium or iron concentration up to 9 days.     

Rapid determination of lead in biological tissues by microsampling-cup atomic absorption spectrometry

Lead can be determined in kidney, liver, and lung tissues by a rapid technique which does not require ashing or acid digestion of the sample. The tissue is homogenized with water, an aliquot of the homogenate is pipetted into a microsampling cup, and lead is determined directly by atomic absorption spectrometry. Calibration is by lead standards in a whole blood matrix. Results correlate well with those obtained by a wet-ashing procedure. The sensitivity (0.01 μg Pb g^-1 wet tissue) permits the analysis of typical tissues with good precision. The procedure is rapid, and its simplicity minimizes the risk of contamination by extraneous lead during sample preparation.     

Determination of Zn, B, Fe, Mg, Ca, Na and Si in anisette samples by inductively coupled plasma atomic emission spectrometry

A comparative study of several digestion methods of anisette samples has been carried out. Two dry ashing (DA) treatments as well as four wet ashing (WA) procedures using different mixtures of acids were applied for the sample mineralisation before analysis. Once the anisette samples were mineralised, the contents of Zn, B, Fe, Mg, Ca, Na and Si were determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES). Each method has been studied statistically and also attending to their feasibility. After performing the optimisation of the different treatments tested, it was concluded that one wet ashing method employing a HNO₃:H₂O₂ (10:1) mixture was the most suitable. This method was applied to the analysis of anisette samples. Na, Ca, Mg and Si were present in concentrations up to 215 mg l⁻¹ for Na, 11.6 for Mg, 6.2 for Ca and 5.1 for Si. Fe and B concentrations were not higher than 0.12 mg l⁻¹ and lower for Zn.     

Spectrochemical cobalt,molybdenum and copper determinations in plants

This paper deals with the spectrochemical determination of some trace elements (Cu, Mo and Co), especially in plant samples. Data are given about the choice of light source and spectral apparatus, as well as detailed remarks concerning the optical arrangement.In the concentrating pretreatment with precipitating chemicals a wet ashing has been proved to give better results than a dry ashing.     

Extraction and Flameless AAS Determination of Germanium in Lignite Fly Ash

Abstract

The use of dicyclohexyl-18-crown-6 methyl isobutyl ketone solution in extraction and flamelessatomic absorption spectrophotometry (AAS) determination of germanium in lignite fly ashes have been studied.

Germanium is usually determined in lignites after the carbonaceous part of the sample has been burnt by a dry or wet ashing method. However, methods are described for direct determination of germanium.

In the present paper a wet ashing method is reported for the determination of germanium in lignite fly ashes by flameless AAS after extraction into dicyclohexyl-18-crown-6 methyl isobutyl ketone (MIBK) solution. Solvent extraction is a known hydrometallurgical method that could be applied in germanium recovery.     

Speciation of the inorganic components in brown coal

Brown coal samples from different deposits have been analyzed for the bonding forms of their inorganic components. Besides the analysis of the dried coals, ashing techniques (high and low temperature ashing) and extraction procedures with different solvents (acids, bases, complexation agents, organic solvents with different polarity) have also been investigated. ESCA, PIXE, INAA, ICP-Atomic Emission Spectroscopy, NMR and Ionchromatography have been applied to the analysis of coals, ashes, wet ashing and extraction products. The bonding behavior of more than 40 elements could be characterized. Conclusions about geological and geochemical processes during and after coalification could be drawn.