Nitric-perchloric Acid Mixture Research Articles

Comparative evaluation of trace elements in the scalp hair of arthritis patients and healthy donors

This study was aimed to evaluate the comparative distribution, correlation and apportionment of selected elements (Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Pb and Zn) in the scalp hair of arthritis patients and healthy subjects. The hair samples collected from the patients (rheumatoid and osteoarthritis) and healthy donors were digested in nitric acid and perchloric acid mixture, followed by the quantification of trace elements using atomic absorption spectrometry. In the case of healthy donors, highest mean concentration was shown by Ca (3240 µg g−1), followed by Mg (340 µg g−1), Zn (192 µg g−1), Fe (184 µg g−1) and Pb (27 µg g−1), whereas, the estimated average metal levels in rheumatoid arthritis and osteoarthritis patients were 3160, 290, 197, 61 and 23 µg g−1, and 3090, 300, 182, 50 and 21 µg g−1, respectively. Most of the elements revealed diverse and random distribution in the scalp hair of the donor groups. The correlation study pointed out significant disparities in the mutual relationships among the trace elements in the patients and controls. Principal component analysis and cluster analysis of the element data manifested diverse apportionment of the selected elements in the scalp hair of the patients compared with the healthy counterparts.

Determination of Hg and diet identification in otter ( Lontra longicaudis) feces

An analytical procedure for the determination of Hg in otter ( Lontra longicaudis) feces was developed, to separate fish scales for the identification of the animal diet. Samples were washed with ultra-pure water and the suspension was sampled and transferred for digestion. The solubilization was performed with nitric–perchloric acid mixture, and detection carried out by the atomic fluorescence spectrometry (AFS). The quality of the analytical procedure was assessed by analyzing in-house standard solutions and certified reference materials. Total Hg concentrations were in the range of 7.6–156 ng g −1 (July 2004), 25.6–277 ng g −1 (January 2005) and 14.6–744 ng g −1 (May 2005) that is approximately the same order of magnitude for all samples collected in two reservoirs at the Tiete River, Brazil. Although Hg concentrations varied with sampling periods and diet, high levels were correlated to the percentage of carnivorous fish scales present in the otter feces.

Determination of Rubidium in Infant Formulas by Flame Photometry

The rubidium content of infant formulas was determined by flame photometry using the atomic absorption spectrophotometer (AAS) with air-acetylene flame. In this work, the optimum instrumental conditions for rubidium analysis were determined: the burner height of AAS, the acetylene pressure, the hydrochloric acid concentration as a measuring solution and so on. The effects of coexisting ions expected from matrix components of infant formulas were tested; the results showed no interferences of Na+, Ca2+, Mg2+, PO43− (∼250 μg/ml) and K+ (∼25 μg/ml). In addition, a variation of the sample amount (0.1∼1 g) for the analysis did not interfere with the determination of the rubidium content of the sample. Rubidium was determined as follows: A sample (0.3 g) in a beaker (50 ml volume) was decomposed by heating with a nitric-perchloric acid mixture on a hot-plate; the solution was then diluted to 100 ml with water after the addition of 2 ml of 6 mol/l hydrochloric acid. Standard rubidium was recovered to be 100 ± 0.9 (n = 20) from an infant formula sample. This method was applied to 24 infant formula samples, resulting in the fact that there was a significant difference in the rubidium content between 10.7 ± 2.9 μg/g (n = 14) in follow-up formulas and 5.35 ± 1.71 μg/g (n = 10) in young infant formulas (p<0.05).

Determination of dysprosium and europium in sheep faeces by graphite furnace and tungsten coil electrothermal atomic absorption spectrometry

Tungsten coil atomizer atomic absorption spectrometry (TCAAS) was used to determine Dy and Eu in acid-digested faeces of sheep. These elements were used as markers in animal nutrition studies. Samples were dried, ground and decomposed using a nitric–perchloric acid mixture. The accuracy of the developed method was evaluated by graphite furnace atomic absorption spectrometry (GFAAS). The results obtained for Eu were validated at a 95% confidence level using a paired t-test. The results for Dy were not validated owing to memory effects caused by carbide formation into the graphite tube. This effect did not occur for Eu. The detection limits for Dy and Eu were 6.9 and 2.1 μg l −1 by TCAAS, and 2.2 and 5.2 μg l −1 by GFAAS, respectively. Relative standard deviations (R.S.D.; n=5) were 0.7–3.8 and 0.8–5.6% for Dy and Eu by TCAAS and 0.8–5.4 and 0.3–3.8% for Dy and Eu by GFAAS, respectively. The lifetime of the tungsten coil was around 200 heating cycles, which is three-fold higher than graphite tube lifetime. The proposed method can be used to determine the passage rate of feed through animal digestive tract.

Total Selenium Concentration in Various Waters of Turkey

The total selenium levels of 335 water samples of Turkey were determined by a spectrofluorometric method. The samples were digested in nitric-perchloric acid mixture, potential interferences were masked with disodium EDTA-HONH2.HCl and selenium was complexed with freshly prepared 2,3-diaminonaphthalene solution and estimated spectrofluorometrically after extraction in cyclohexane. The selenium content of various waters (rain, tap, mineral, sea, lake, river, bottled drinking waters and collected drinking waters from 42 cities in Turkey) were determined. The selenium levels were compared with the literature data from different countries.

Hydride generation atomic absorption spectrometric (HGAAS) determination of selenium in term and preterm infant formulae available in the United Kingdom

A simple and sensitive hydride generation atomic absorption spectrometry method is described for the determination of total selenium in infant formulae. Decomposition of the composite sample matrix involved overnight digestion with a nitric-perchloric acid mixture (10:2 ml) then heating at 150 °C (30 min) and 220 °C (60 min). No apparent matrix interferences were encountered. The selenium levels in infant formulae, reported for the first time, ranged from 0.034 to 0.093 μ/g (dry wt) for bovine casein and whey-based term powdered infant products, 0.023–0.093 μg/g (dry wt) for preterm powdered formulae and 0.027–0.049 μ/g (wet wt) for hospital administered low birth weight ready-to-feed formulae. These values are dependent on geographic origin of bovine milk and exhibit variation between batches. Routine QC analysis and fortification by manufacturers is recommended.

Determination of selenium in foodstuffs using spectrofluorometry and hydride generation atomic absorption spectrometry

Two analytical methods, namely, spectrolluorometry and hydride generation atomic absorption spectrometry (HG-AAS), were used for determining the levels of selenium in food materials. The results of the two methods were compared. The efficiencies of acid mixtures used for decomposition of biological materials were also investigated. Nitric-perchloric acid mixture was found to be the most efficient method for spectrolluorometry. Nitric-perchloric acid mixture or nitric-perchloric-sulfuric acid mixture was found to be the most efficient method for HG-AAS. No apparent matrix interferences were encountered for either method of analysis. A wide range of levels of selenium was found in selected foods analyzed. High levels of selenium were found in cereals, meat, fish, and wheat products and relatively low levels in milk and milk products. Fruits and vegetables contained very little selenium and negligible amounts were found inmost drinks.

Determination of phosphorus-32 in wet-digested plant leaves by Cerenkov counting

A method of determination of 32P activity in leaf samples by Cerenkov counting technique is described. The method involves wet digestion of oven-dried leaves with 1:1 nitric-perchloric acid mixture followed by transferring the digest into a scintillation counting vial with distilled water upto a final volume of 20 mL, and determining the activity in a liquid scintillation system. Reproducible count rates can be obtained if the vials are counted after 4 h allowing the silica in the digest to settle.

Atomic absorption spectrometric determination of trace elements in coal by using an acid digestion in sealed polytetrafluoroethylene vessel.

As a wet digestion method of coal, digestion with nitricperchloric acid mixture was studied by using a sealed polytetrafluoroethylene(PTFE) digestion vessel. A PTFE inner vessel modified to this purpose was of 50 ml capacity, put in an outer stainless steel vessel, and sealed tightly with a PTFE O-ring inserted between the vessel and a cover plate. Coal containing up to 86 % fixed carbon was sufficiently decomposed with the nitric-perchloric acid mixture (1:1) by heating at 150-160 °C for 7-14 h. The sample preparation consisted of further digestion with hydrofluoric acid, followed by addition of boric acid, aqueous dilution and filtration. Nine elements in NBS 1632a coal were determined. Matrix elements of a calibration standard require no precise matching to the sample solution.

Determination of bismuth and lead in steel and cast iron by hydride generation and zeeman atomic absorption spectrometry

Procedures are described for the determination of lead and bismuth in steel and cast iron by atomic absorption spectrometry (a.a.s.). Two alternative decomposition procedures are applied, namely, sodium peroxide fusion in zirconium crucibles and digestion with a nitric—perchloric acid mixture in a Bethge digestion apparatus. The latter technique is preferred. Lead is measured by electrothermal a.a.s. with Zeeman background correction. Bismuth is determined after hydride generation with sodium tetrahydroborate. Calibration is done by standard addition. The sensitivities obtained are 1 μg g −1 for lead in steel and cast iron and 5 μg g −1 for bismuth in white and grey cast iron. The r.s.d, is generally better than 10% for > 10 μg g −1. The method is applied to standard reference steel samples and several specimen cast irons.

Fluorometry of selenium in human hair, urine and blood. A single-tube process for submicrogram determination of selenium.

This communication introduces a special lyophilization process for selenium determination by fluorometric methods. It permits a small sample volume, with several modifications including a single test tube process. Samples and standard are lyophilized first, then digested with nitric-perchloric acid mixture in a heated sand bath. Selenium is complexed with 2,3-diaminonaphthalene and extracted by n-hexane in the same test tube. The n-hexane layer is transferred to a cuvette and measured fluorometrically. Selenium concentration in healthy children from Long Island (aged 5-18 years) was: hair 0.765 +/- 0.114 microgram/g (n = 52), urine 28.65 +/- 8.27 micrograms/g creatinine (n = 66), and serum 95.4 +/- 14.4 ng/ml (n = 44). The current literature reflects an increase in the role of selenium in human nutrition. Thus, a simple but reliable method for determination of selenium in biological materials is needed in the clinical and research laboratory.

A Practical Voltammetric Method for the Analysis of Lead in Cereal and Feed Products using A Tubular Mercury Thin Film Electrode

Abstract An uncomplicated, anodic stripping voltammetric (ASV) method was developed using a mercury, thin film tubular electrode with a large surface area to detect lead at submicrogram levels in a variety of cereal and feed products. Samples were wet digested in a nitric-perchloric acid mixture for approximately two hours in their respective analysis cells, and then analyzed in a 2 M sodium ace-tate-0.4 M sodium chloride buffer (pH 6.5) system. Measurements were performed on a high speed electrochemical system using staircase voltammetry with a measurement time of approximately 3 minutes per sample. Relative standard deviation was less than 10%. Agree ment with standard reierciice material was within certified limits. When compared with fiame atomic absorption spectrometry (FMS) using a chelation solvent extraction, Lhe proposed ASV method was less time consuming, less costly to operate, and more precise.

Determination of radioactive and stable cobalt in marine biological materials (author's transl)

Studies were made to develop the method for rapid determination of radioactive and stable cobalt in a single specimen of marine biological materials. The sample was dried, ashed, and dissolved in acid. The cobalt was extracted with 1-nitroso-2-naphthol benzene and determined by absorptiometry on the benzene phase. Then, the organic solution was evaporated to dryness, and the residue was treated with nitric-perchloric acid mixture to decompose any organic matter, and taken up with hydrochloric acid. The cobolt was extracted from the solution with TIO A-toluene, and the radioactive cobalt was determined by liquid scintillation counting on the toluene phase. Examinations were made on the chemical yield and on the decontamination factor of the fission product nuclides. Analysis were made on the marine biological samples of Urazoko Bay, Fukui prefecture. Agreement of the radioactive cobalt data between that by the present method and that by Ge(Li) gamma ray spectometry was good. Also, the stable cobalt value by the present method agreed well with that by neutron activation analysis method.

A note on the elemental concentrations of New Zealand pasture seeds

Abstract Pasture seeds from commercial seed stores were dried overnight, digested with a nitric-perchloric acid mixture, and the digests were analysed for manganese, zinc, copper, iron, calcium, magnesium, sodium, potassium, phosphorus, boron, molybdenum, and nitrogen. Legumes were higher in nitrogen, phosphorus, magnesium, potassium, zinc, copper, iron, boron, and molybdenum, but lower in calcium and manganese, than grasses. Red clover cultivars contained more nitrogen, magnesium, zinc, and copper, but less sodium and molybdenum than other legumes. Browntop was lower in sodium and potassium, but higher in all the other elements (not boron) than the remainder of the grasses. The results indicate that, except for molybdenum, the concentrations of nutrient elements in pasture grass and legume seeds fall within a narrow range despite being grown under different management and fertiliser practices. Molybdenum concentration, however, can be increased by raising the molybdenum status of the soil.

Gas-Liquid Chromatographic Determination of Selenium in Biological Materials, Using 4-Bromo- and 4-Chloro-1,2-Diaminobenzene as Derivatizing Reagents

A method is described for the gas-liquid chromatographic determination of traces of selenium in marine biological materials. The method is based on the reaction of Se(IV) with bromo- and chloro-substituted 1,2-diaminobenzenes. The benzoselenadiazoles so formed are sensitive to electron capture detection. The sample is digested in a nitric-perchloric acid mixture and selenium is reduced to the IV oxidation state. Different aliquots of the digest solution are reacted with either 4-bromo- or 4-chloro-1,2-diaminobenzene to quantitatively form the corresponding 2,1,3-benzoselenadiazole. Recovery of added selenite to a fish meal sample was 95% for the bromo derivative and 101% for the chloro derivative. Different portions of a well mixed fish meal sample were analyzed in independent laboratories by the fluorometric method and by atomic absorption spectrophotometry (hydride generation). The following mean values (microgram/g) were found: present method 1.89, fluorometric method 1.91, atomic absorption method 2.1. The lower limit of detection for the method described was 13 ng, using the bromo derivative, and 27 ng, using the chloro derivative.

Rapid digestion procedure for use in metal analysis

Biological tissue is commonly prepared for heavy metal analysis by digestion in nitric acid or in a nitric-perchloric acid mixture. Nitric acid digestion at room temperature is time-consuming and even when perchloric acid is added to it, a small amount of tissue may resist digestion. The speed and thoroughness of digestion may be substantially improved by irradiating the samples with light between approximately 320 and 420 nm as reported by this paper.

Rapid Digestion and Flameless Atomic Absorption Spectroscopy of Mercury in Fish: Collaborative Study

A collaborative study of the determination of mercury in fish has been completed in which wet oxidation of fish tissue in nitric acid, using vanadium as a catalyst, is compared with the AOAC official final action digestion technique, 25.103-25.105, involving a nitric-perchloric acid mixture. The study used tuna fish samples of known mercury content and included spike recovery studies in which methyl mercury solutions of known composition were provided to each laboratory. The study was designed to provide recovery information that bracketed the regulatory level of mercury in fish. The results indicate that the proposed digestion method is at least as precise and accurate as the AOAC method. The proposed method is also more rapid and less hazardous. It has been adopted as official first action.

An automated submicrogram determination of selenium in vegetation by quartz-tube furnace atomic-absorption spectrophotometry

An automated method for the determination of submicrogram amounts of selenium in vegetation is described. A weighed sample of vegetation is digested with a 4:1 nitric-perchloric acid mixture, and made up to a known volume. The digested sample is placed in a Technicon sampler and reacted with sodium borohydride solution. The selenium converted into the gaseous hydride is swept by an argon stream into a gas-liquid separator. The mixed gas stream is passed through a heated quartz cell, positioned in the light-path of an atomic-absorption spectrophotometer. The absorption by the atomized selenium is recorded. The method is capable of analysing 50 samples a day by the use of a calibration curve or 25 a day by the standard addition technique. A relative standard deviation of better than 10% and a detection limit of 0.025 μg g were obtained.

Collaborative Study of Wet and Dry Ashing Techniques for the Elemental Analysis of Plant Tissue by Atomic Absorption Spectrophotometry

Abstract Seven laboratories participated in a collaborative study of wet ashing of plant material with a nitric-perchloric acid mixture and dry ashing at 500°C in order to determine the elements calcium, copper, iron, magnesium, manganese, potassium, and zinc by atomic absorption spectrophotometry. Five different homogeneous leaf tissue samples were analyzed and a synthetic standard solution containing all of the elements studied was included to evaluate sample preparation errors independent of instrument errors. The results indicated that plant tissue preparation by either wet or dry ashing gave similar elemental composition results for the tissues analyzed. The wet and dry ashing techniques have been adopted as official first action.

Rapid colorimetric determination of phosphorus in geochemical survey samples

A colorimetric method for the determination of phosphorus in batches of geochemical survey samples is described. The powdered material is digested with a nitric-perchloric acid mixture, excess of acid is evaporated off and the residue is leached with water. Aliquots of the leachate are treated with vanadomolybdate reagent and the yellow phosphorus complex is extracted into isobutyl methyl ketone. The colour in the organic phase, which is stable for many days, is matched against a series of similarly prepared standards. Iron, other coloured ions, and titanium do not interfere. Standard deviations of ±0.02% about a mean value of 0.20% P 2 O 5 and ±0.4% about a mean of 11.6% P 2 O 5 were obtained. At least 40 powdered samples may be analysed per working day per person.