A safe method to acid digest small samples of biological tissues for graphite furnace atomic absorption analysis of aluminum

A method was developed to prepare small biological tissue samples (approximately 100 mg) for flameless atomic absorption analysis of aluminum (Al). Screw cap Teflon containers were used in which the samples were dried, acid digested, acid evaporated, and diluted for analysis, minimizing contamination and sample loss. A heatable, semiclosed system was developed in which the nitric and perchloric acids used in tissue digestion could be safely evaporated from the sample containers and collected. Several spectrophotometer operating conditions for Al determination were compared, and a suitable condition was adopted. Analyses for aluminum levels in acid digested samples were conducted at two absorption wavelengths (309.3 and 396.2 nm) and by two analytical procedures (comparison of sample absorbance to standard absorbance and the method of standard additions). The developed method is suitable for analysis of the low levels of aluminum found in biological tissues and probably other elements as well. The method incorporates procedures designed to minimize contamination and the hazards of acid tissue digestion.     

微波消解- 火焰原子吸收光谱法测定蜂胶中金属元素含量

目的:测定一种原产地为加拿大的蜂胶中金属元素的含量,为进一步研究蜂胶营养价值提供数据,同时改进测量方法。方法:用微波消解法处理样品,用硝酸和过氧化氢的混合物作为消解剂进行微波消解,并优化消解条件,然后用火焰原子吸收光谱法测定蜂胶制品中钙、铁、镁、锌、钠、钾、铜的含量。结果:七种元素相对标准偏差为0.85%~2.33%(n=7),回收率在96.5%~104.7%之间。试验结果表明该蜂胶中含有丰富的金属元素,且与河南产蜂胶相比,加拿大产蜂胶中多种金属元素含量远低于河南产蜂胶。结论:使用本文方法测定蜂胶中的金属元素含量,结果准确,方法可靠。为进一步探讨蜂胶制品金属元素与其保健功能的关系提供了有用数据。     

微波消解－火焰原子吸收光谱法测定蜂胶中金属元素含量

目的：测定一种原产地为加拿大的蜂胶中金属元素的含量,为进一步研究蜂胶营养价值提供数据,同时改进测量方法。方法：用微波消解法处理样品,用硝酸和过氧化氢的混合物作为消解剂进行微波消解,并优化消解条件,然后用火焰原子吸收光谱法测定蜂胶制品中钙、铁、镁、锌、钠、钾、铜的含量。结果：七种元素相对标准偏差为O．85％～2．33％（n=7）,回收率在96．5％～104．7％之间。试验结果表明该蜂胶中含有丰富的金属元素,且与河南产蜂胶相比,加拿大产蜂胶中多种金属元素含量远低于河南产蜂胶。结论：使用本文方法测定蜂胶中的金属元素含量,结果准确,方法可靠。为进一步探讨蜂胶制品金属元素与其保健功能的关系提供了有用数据。     

The accumulation and distribution of trace metals in some localized marine species

Trace elements, such as As, Co, Cr, Hg, Sb, and Zn, were determined by neutron activation analysis (NAA), whereas Cd, Cu, and Pb were determined by graphite furnace atomic absorption spectroscopy (GFAAS) in clam, crab, prawn, swamp cerith, and mussel samples after digestion by microwave heating under controlled conditions before eluting the solutions through a column of a chelating resin, Chelex-100. The standard used in the determination of percentage volatile elements retained by microwave digestion and also in the activation process wasLobster Hepatopancreas TORT-1, whereas known mixed standards were prepared from nitrate salts to determine the efficiency of the separation procedure at a controlled pH. Mercury and lead detected in crabs exceeded the maximum permissible level. Some species also showed a high affinity toward certain elements, and their levels of accumulation in the tissues of these species corresponded with the concentration of these elements in sediments, especially at sites in the vicinity of an industrial zone.     

A study on the digestion of human muscle biopsies for trace metal analysis using an organic tissue solubilizer.

A commercially available tissue solubilizer, based on tetraalkyl-ammonium hydroxide in toluene, has been compared with conventional digestion producers in order to determine the minimum amount of tissue needed for the determination of trace elements such as Al, Cd, Cu, and Mn in human biopsy material using flameless atomic absorption spectrophotometry. The solubilizer can be recommended for digestion of biopsy samples in order to determine Cu, Cd, and Mn, but not Al.     

Microwave-assisted acid extraction methodology for trace elements determination in mastic gum of Pistacia lentiscus using inductively coupled plasma atomic emission spectrometry

Introduction – To ensure food safety, accurate knowledge of the levels of several trace elements is necessary. This is also true for natural products of plants and resins used for human consumption or therapeutic treatment, like the mastic gum of Pistacia lentiscus. The rapid analysis of gum and resin matrices is a challenge because there are problems with the decomposition of such complicated matrices. Objective – To develop an efficient multielemental analytical method for the determination of trace elements and to compare different procedures for analyte extraction when microwave‐assisted digestion is applied. Methodology – The inductively coupled plasma atomic emission spectrometric (ICP‐AES) technique was applied and the optimum ICP conditions like radiofrequency power, argon flow rate and nebuliser sample uptake flowrate were found. The microwave‐assisted procedure was compared with that with conventional heating. Since mastic and resinous materials are difficult for dissolution and extraction of trace element, influential acid mixtures containing hydrofluoric acid proved to be capable of quantitative extraction of the analytes. Results – The digestion of mastic resin or similar matrices is significantly facilitated by using microwave radiation instead of conventional heating since the obtained recovery for several analytes is much higher. It was proved that the acid mixture of HCl–HNO₃–HF was the most efficient for complete sample digestion and recovery of the analytes. Conclusions The performance characteristics of the developed method were evaluated against certified reference material and the method was proved reliable and applicable to the analysis of mastic gum and possibly to similar resinous matrices. Copyright © 2010 John Wiley & Sons, Ltd.     

Evaluation of Dog Bones in the Indirect Assessment of Environmental Contamination with Trace Elements

The aim of this paper was to determine the level of five elements, two essential for life [zinc (Zn) and copper (Cu)] and three distinctly toxic [lead (Pb), cadmium (Cd), and mercury (Hg)], in four types of biological material in bones of the dog Canis lupus familiaris. The experiment was carried out on bones from the hip joints of dogs. The samples of cartilage, compact bone, spongy bone, and cartilage with adjacent compact bone came from 26 domestic dogs from northwestern Poland. Concentrations of Cu, Zn, Pb, and Cd were determined by ICP-AES (atomic absorption spectrophotometry) in inductively coupled argon plasma, using a Perkin-Elmer Optima 2000 DV. Determination of Hg concentration was performed by atomic absorption spectroscopy. In the examined bone material from the dog, the greatest concentrations (median) were observed for Zn and the lowest for Hg (98 mg Zn/kg and 0.0015 mg Hg/kg dw, respectively). In cartilage and spongy bone, metal concentrations could be arranged in the following descending order: Zn > Pb > Cu > Cd > Hg. In compact bone, the order was slightly different: Zn > Pb > Cd > Cu > Hg (from median 70 mg/kg dw to 0.002 mg/kg dw). The comparisons of metal concentrations between the examined bone materials showed distinct differences only in relation to Hg: between concentrations in spongy bone, compact bone, and in cartilage, being greater in cartilage than in compact bone, and lower again in spongy bone.     

A hydrogen-peroxide digestion system for tissue trace-metal analysis

Tissue digestion prior to analysis for trace metals is usually carried out with strong acids. Nitric acid, alone or in combination with perchloric acid, is most commonly used. In addition to the laborious acid washing of all glassware prior to use, the digestion necessitates exposure to potential environmental contamination. Use of perchloric acid mandates a specially constructed hood with facilities for washing to remove acid deposits. A simple digestion procedure using 30% hydrogen peroxide in polyethylene vials in an oven at approximately 75°C has been previously described for the measurement of zinc in tissues using flame or flameless atomic absorption spectrophotometry and of selenium in liver by flameless atomic absorption. Readings for reagent blanks were insignificant. The technique has been further developed with a reduction in digestion time using 50% H₂O₂. Analysis of liver has been extended to include copper, manganese, and arsenic. Although the level of arsenic present was too low to be detected, 50 and 100 ng of this element added to the liver powder was completely recovered. The digest obtained when dissolved in appropriate solvent is suitable for analysis for multiple trace metals. Author to whom all correspondence and reprint requests should be addressed.     

Determination of selenium in Teucrium species by hydride generation atomic absorption spectrometry

Hydride generation atomic absorption spectrometry (HGAAS) was applied for determination of selenium content in dried aerial parts of wild and cultivated Teucrium species (Lamiaceae) growing in Croatia: T. arduini L., T. chamaedrys L., T. flavum L., T. montanum L., T. polium L., and T. scordium L. subsp. scordioides Schreb. Special attention was paid to the wet oxidation procedure for the sample dissolution. The proposed procedure involved microwave-assisted sample digestion using a mixture of HNO3/H2O2. Wild specimens generally had a higher content of selenium, with concentrations of 0.030-0.095 mg/kg of the dry drug. Cultivated plants contained 0.020-0.055 mg Se/kg.     

Diet and status at Chalcatzingo: some empirical and technical aspects of strontium analysis.

Determination of the levels of particular trace elements preserved in bone provides a potential pathway for reconstructing the diet of extinct primate species and archaic human groups. Strontium is one of the most useful trace elements for dietary reconstruction but several empirical properties of strontium must be considered during the interpretation of results. (1) Strontium is distributed unevenly throughout the physical environment. (2) Plants, in general, do not discriminate against strontium. (3) During ionic transfer across biological membranes, strontium is discriminated against by terrestrial vertebrates. (4) It is unlikely that strontium would be selectively removed from bone mineral during diagenesis. A particular difficulty in trace element analysis is caused by interaction between analytical technique and sample matrix. To assess this problem the skeletal population from Chalcatzingo was analyzed by two techniques: atomic absorption spectrometry and neutron activation analysis. The results from the two techniques compared favorably indicating that the pattern of bone strontium levels could be accepted as an accurate reflection of the distribution of bone strontium within the population. After demonstrating the internal accuracy of the results, the bone strontium level and position of social rank within Chalcatzingo were compared. Ethnographic and archaeological evidence on chiefdoms and states indicate that dietary differences in the amount of meat consumed occur between social ranks. The relative social ranks were reconstructed by using a "pattern analysis" of the burial goods accompanying each individual. The individuals accompanied by jade had the lowest mean bone strontium level (X = 532). Those individuals buried with a shallow dish had a slightly higher level (X = 635). A third group, which had no grave goods, had the highest mean bone strontium level (X = 700) which suggests that their diet contained less meat than was available to the rest of the community.     

The content of manganese and iron in hip joint tissue

Manganese and iron are elements that constitute components of bone tissue. The aim of this study was to determine presence of manganese and iron in hip joint tissue and interdependencies between these elements. The objects of the research were hip joint elements from people residing in cities on the territory of the Upper Silesian Industrial District. The number of people in the study group was 91 samples, including 66 samples from women and 25 from a man. The examined tissues were obtained intraoperatively during hip replacement procedures. The content of manganese and iron was determined using the atomic absorption spectrophotometry (AAS) method. The lowest content of manganese and iron was found in the cortical bone, and the largest, in the case of manganese, in the articular cartilage, whereas in the case of iron in a fragment of the cancellous bone from the intertrochanteric area. The content of iron in selected elements of the hip joint decreased with age. Higher content of manganese in hip joint tissue of women compared to men was confirmed. What is more, higher content of iron in hip joint tissue of men was confirmed as well.     

Room temperature solvent extraction for simple and fast determination of total concentration of Ca,Cu, Fe,Mg, Mn,and Zn in bee pollen by FAAS along with assessment of the bioaccessible fraction of these elements using in vitro gastrointestinal digestion

Background and aimBee pollen is recognized to be a source of different nutrients, including minerals. As a food supplement, its quality and safety due to concentrations of essential macro- and microelements, and harmful trace elements has to be verified. Fast and simple element analysis of bee-collected pollen can be regarded as an important part of its quality assurance and control. The present study aimed at developping a new method for determination of selected elements (Ca, Cu, Fe, Mg, Mn, Zn) of bee pollen based on solvent extraction and completely avoiding a high temperature treatment with concentrated reagents. In addition, in vitro gastrointestinal digestion was used to assess bioavailability of elements from this food supplement.MethodsBee pollen samples were dried and pulverized. Total concentrations of Ca, Cu, Fe, Mg, Mn, and Zn were determined by flame atomic absorption spectrometry (FAAS) in sample solutions obtained by wet digestion (WD) in concentrated HNO₃ or alternatively by solvent extraction (SE) with diluted solutions of HNO₃. Gastrointestinal digestion was mimicked using simulated solutions of gastric and intestinal juices followed by determination of Ca, Cu, Fe, Mg, Mn and Zn concentrations in the bioaccessible fraction by FAAS.ResultsA new simple and fast method for determination of total concentrations of Ca, Cu, Fe, Mg, Mn, and Zn in bee pollen was developed and validated. The method combined room temperature, two-hour SE with 0.5 mol L⁻¹ HNO₃ with FAAS measurements versus simple standard solutions. It provided precision within 1–5 % and trueness better than 8%, and was shown to be suitable for fast analysis of different polyfloral bee pollens. In vitro gastrointestinal digestion revealed that elements were well (70–85 % for Ca, Mg) and fairly (27–43 % for Cu, Fe, Mn, and Zn) bioaccessible from bee pollen. By pouring with water and swelling overnight, bioaccessibility of studied elements from such prepared bee pollen was increased on average by less than 15 % (Mn), 20 % (Ca, Cu, Fe, Zn) or 30 % (Mn).ConclusionsAvoiding long-lasting, high-temperature wet digestion with concentrated reagents, the proposed sample treatment along with FAAS provided precise and true results of total concentrations of Ca, Cu, Fe, Mg, Mn, and Zn in bee pollen. The method was simple and fast, and enabled to analyze a higher number of samples. Simulated gastrointestinal digestion of bee pollen have shown for the first time that Ca and Mg are the most bioaccessible from this bee product. Bioaccessibility of Cu, Fe, Mg, and Zn from bee pollen are close to or lower than 40 %.     

微波消解-FAAS法测定普通甘薯和紫甘薯中的金属元素

采用微波消解法处理普通甘薯和紫甘薯样品,运用火焰原子吸收光谱法测定其中的K、Ca、Mg、Fe、Mn、Zn、Cu 7种对人体有益的金属元素含量。结果表明,普通甘薯和紫甘薯中K、Ca、Fe、Mg元素含量较高,Mn、Zn、Cu元素含量较低,且7种金属元素含量在两者之间存在一定的差异,各元素在紫甘薯中的含量均比普通甘薯中含量高。方法的加标回收率介于98.5%～103.2%,相对标准偏差(RSD)不大于3.14%。可为普通甘薯与紫甘薯的品质评价提供理论参考。     

Determination of zinc, copper, lead and cadmium in some medicinally important leaves by differential pulse anodic stripping analysis

Levels of zinc, copper, lead and cadmium have been determined in some medicinally important leaves by differential pulse anodic stripping voltammetry (DPASV). High pressure digestion with nitric acid (HPA) was used for sample digestion. The accuracy of the method was verified by the parallel analysis of leaves with inductively coupled plasma atomic emission spectroscopy (ICP-AES) and recovery studies by the analysis of standard reference materials. Based on elemental levels the utility of these leaves in medicine are discussed. Statistical treatment has been used in order to understand the correlation between elements in these leaves.     

Trace metals and micronutrients in bone tissues of the red fox <Emphasis Type="Italic">Vulpes vulpes</Emphasis> (L., 1758)

In this study we determined the levels of trace elements (zinc, copper, lead, cadmium and mercury) in three layers of bones of the hip joint (cartilage, compact bone and spongy bone) of 30 red foxes (Vulpes vulpes) from north-western Poland. Concentrations of Cu, Zn, Pb and Cd were determined by atomic absorption spectrophotometry (ICP-AES) in inductively coupled argon plasma using a Perkin-Elmer Optima 2000 DV. Determination of Hg concentration was performed by atomic absorption spectroscopy. In cartilage, compact bone and spongy bone samples from the red fox, median concentrations of the metals studied could be arranged in the following descending series: Zn > Cu > Pb > Cd > Hg, the values ranging from 142 to 0.002 mg/kg dw. There was a significant difference in Cu concentrations, among all the materials analyzed, with much more Cu found in spongy bone than in compact bone. Significant differences were also noted in the case of Hg concentrations in cartilage with compact bone and the spongy bone, and between concentrations of this metal in compact bone and spongy bone. In males, the concentration of Hg in spongy bone was greater than in females. Younger foxes had a higher concentration of this metal in cartilage than adults. The strongest synergistic relationships were observed in spongy bone between the Zn and Cu, Zn and Cd, as well as between Cu and Cd. Statistically significant antagonistic relationships were detected between zinc and lead in compact bone. In addition to monitoring studies conducted on the abiotic environment, an urgent need exists for long-term monitoring of concentrations of heavy metals with long-term effects on living organisms. An important addition is provided by biomonitoring studies on domesticated and free-living mammals, including Canidae.     

Tissue digestion for aluminum determination in experimental animal studies

Four different procedures for the determination of aluminum in tissues by atomic absorption spectrometry (AAS) were investigated. They consisted of conventional acid digestion carried out before and after sample drying, associated or not with fat extraction. Drying was carried out in a conventional oven at 65 °C for 24 h. For fat extraction, different solvents and solvent mixtures were investigated considering both extraction yield and sample adequacy for further AAS measurement. Acid digestion was carried out with pure HNO₃ or with its mixture with HClO₄. After digestion, aluminum was measured by graphite furnace atomic absorption spectrometry. Tissues were collected from Al-exposed and nonexposed mice. The results indicated that drying the sample prior to digestion is advantageous as the amount of acid necessary can be significantly reduced. This procedure does not contribute to increase the aluminum level in the samples providing that careful measures to avoid contamination are taken, as the same procedures carried out without taking any precautions to avoid contamination produced imprecise results. Finally, aluminum was not found in the fatty fraction of any sample, even in exposed mice, demonstrating that aluminum does not accumulate in this part of the tissues.     

Evaluation of methods for total selenium determination in yeast

The selenium determination in biological materials by the classical fluorometric method (FM) is time-consuming and also hazardous, as it requires the destruction of the organic matrix samples with hot HNO₃/HClO₄ mixtures prior to analysis. Accordingly, commercial analytical laboratories are increasingly using faster instrumental methods; for sample digestion, avoid using HClO₄. Because of these procedural changes, the results obtained by commercial laboratories may be unreliable, especially for samples containing Se in organic forms. One such “difficult” substrate is Se yeast, which contains most of its Se as selenomethionine. To establish which methods for Se analysis and sample digestion are applicable, samples of Se yeast and of selenomethionine standards were sent to laboratories employing either flame atomic absorption spectrometry (FAAS), inductively coupled plasma-mass spectrometry (ICP-MS), or hydride generation atomic absorption spectrometry (HGAAS). The result were compared with those obtained by FM and non-destructive instrumental neutron activation analysis (INAA). ICP-MS, after microwave digestion of sample with HNO₃/H₂O₂, produced results within 5% of the expected values, as did those obtained by FM and INAA. With FAAS, acceptable results were obtained after digestion with HNO₃/HCl. With HGAAS, sample digestion with HNO₃/H₂O₂ produced values that were systematically elevated by about 10% and exhibited standard deviations of ≥10%. Thus, current methods of sample digestion are applicable for Se yeast analysis by ICP-MS and FAAS, but not by HGAAS.     

Studies on some trace and minor elements in blood

Blood is one of the widely used specimens for biological trace element research because of its biological significance and ease of sampling. We have conducted a study of the blood of the Kalpakkam township population for trace and minor elements. For this purpose, analytical methods have been developed and standardized in our laboratory for the elemental analysis of blood plasma and red cells. Inductively coupled plasma-mass spectrometry (ICP-MS), a relatively new technique, has been applied for the analysis of trace elements. Details regarding spectral interference and matrix interference encountered in the analysis of blood and the methods of correcting them have been discussed. Flame atomic absorption spectrometry (AAS)/atomic emission spectrometry (AES) has been applied for the determination of minor elements. Precision and accuracy of these methods have also been discussed.     

Mg content of healthy and chronically diseased human cancellous bone in relation to age and some physical and chemical factors

The magnesium (Mg) content of human cancellous bone was studied in relation to its elemental composition and mineral density. The material was collected from 138 cadavers consisting men and women of different ages. Duplicate specimens from anterior iliac crest (one macerated and one fixed with alcohol) were obtained from individuals who had died suddenly or whose deaths were due to chronic immobilizing diseases. The cation concentrations were analyzed with an atomic absorption spectrophotometer, fluoride with the ion specific electrode, from macerated samples. The samples fixed in alcohol were used for determination of the mineral density with gamma rat attenuation. The mean Mg concentration (+/- SD) was 2.84 +/- 0.29 mg/g in the samples obtained from individuals who had died suddenly with no correlation with age. In the group with chronic diseases the mean Mg levels decreased slightly with increasing age. There was a significant, positive correlation between the Mg and Ca concentrations. In the linear regression analysis 16.4% of the variance of Mg concentration was accounted for by Ca. This relationship was more evident in men than in women. Only the postmenopausal women suffering from chronic diseases and having bone loss showed correlation between the bone Mg and Ca contents. The Mg/Ca ratio in men was quite constant and did not change significantly with age. In women the Mg/Ca ratio versus age showed no statistically significant relationship. The correlation between Mg and other elements was weak. The weak relationships between F and Zn to Mg clearly have no significant effect on the contents of these elements in bone.     

Alterations of Serum Zinc, Copper, Manganese, Iron, Calcium, and Magnesium Concentrations and the Complexity of Interelement Relations in Patients with Obsessive–Compulsive Disorder

The purpose of the present study was to evaluate the status of serum trace elements: zinc, copper, manganese, iron, calcium, and magnesium concentrations in obsessive-compulsive disorder patients. Forty-eight obsessive-compulsive disorder patients and 48 healthy volunteers were included in this study. Patients were recruited from Bangabandhu Sheikh Mujib Medical University by random sampling. Serum trace element concentrations were determined using flame atomic absorption spectroscopy (for zinc, copper, iron, calcium, and magnesium) as well as graphite furnace atomic absorption spectroscopy (for manganese). Data were analyzed using independent t test, Pearson's correlation analysis, regression analysis, and ANOVA. Statistical analysis of these data showed a definite pattern of variation among certain elements in patients with obsessive-compulsive disorder compared to controls. In patients' serum, zinc, iron, and magnesium concentrations decreased significantly (p<0.05) compared to the controls. Serum manganese and calcium concentrations were significantly higher (p<0.05) in patients compared to the controls. These data showed a definite imbalance in the interelement relations in obsessive-compulsive disorder patients compared to controls and therefore suggest a disturbance in the element homeostasis.