Digestion of fish samples for mercury determination by flameless atomic absorption spectrophotometry.

Methods of digestion of fish samples for mercury determination by flameless atomic absorption spectrophotometry have been investigated. Digestion in Teflon bombs, Kjeldahl flasks, or borosilicate test tubes gives comparable precisions and mercury recoveries. Because of their cost and effect in limiting productivity, Teflon bombs were considered unnecessary for analysis of fish samples. Experiments with cooked and uncooked fish samples have confirmed that no appreciable loss of mercury occurs during baking 30 min at 170 degrees C.     

Use of background correction to improve the accuracy of the selective reduction method for determining methyl mercury in fish

Background correction is used with a previously published flameless atomic absorption method for the concurrent determination of inorganic and methyl mercury. The use of background correction simplifies the procedure, but, more importantly, eliminates errors in mercury readings due to broad band absorption by other volatile compounds produced during the determination.     

Simple automated wet digestion of animal tissues for determination of seven elements by atomic absorption spectroscopy

A simple, automated wet digestion procedure was developed for the quantitative determination by atomic absorption spectroscopy (AAS) of arsenic, cadmium, copper, mercury, lead, selenium, and zinc in animal tissue. A commercial digestion block system with automated temperature programming was used. Recoveries of all elements from spiked bovine liver and kidney samples exceed 95%. The analytical results obtained for samples of NBS Bovine Liver (No. 1577a) agree well with certified values. The procedure is safe and requires minimum analyst time.     

Atomic absorption spectrophotometric determination of cobalt in foods

A method is described for the determination of cobalt in foods. After wet digestion, iron in the sample is removed by liquid-liquid extraction, and cobalt is isolated and extracted. Final determination is done by flame atomic absorption spectrophotometry. Analysis of NBS reference materials by this procedure gives results in close agreement with certified values. The limit of quantitation is 4.3 ng/mL. Recovery studies and analysis of standard materials show that this method is reliable.     

Sample oxidation procedures for the determination of chromium and nickel in biological material

Abstract

Sample preparation methods for atomic absorption spectrophotometric analysis of chromium and nickel in biological materials were examined. Radiotracer recovery, precision of analysis and analysis of NBS reference samples were the criteria used. Chromium and nickel in biological materials can be successfully prepared for atomic absorption spectrophotometry by dry ashing with nitric acid treatment of the partially oxidized sample. It was necessary to use at least 5% nitric acid to extract the chromium and nickel from the ash. Vet digestion with nitric acid alone was satisfactory for nickel but not for chromium. Wet digestion gave greater variance and required considerably more time. We found no evidence of loss of chromium by either volatilization or insolubility. Since this method is satisfactory for nickel determination it may be implied that it is also satisfactory for other nonvolatile first transition series elements.     

Accumulation of Glucosamine in the Methanolic Extract Of Corn Shoots Grown without Zinc Supply

Cadmium levels were determined in rice grains of Japonica, Indica, Javanica, and Indica-Japonica hybrid-bred varieties that were produced in the same plot of a non-polluted field in 1983 and 1985, using nameless atomic absorption spectrophotometry.

Cadmium levels in the brown rice grains harvested in 1983 and 1985 ranged from 2.1 to 27 0 ppb Cd for 28 Japonica varieties, 4.1 to 55.5 for 23 Indica varieties, 4.4 to 16.5 for 5 Javanica varieties, and 24.5 to 73.6 for 4 hybrid varieties.

The significant correlation of the cadmium levels between the 1983 and 1985 products may indicate the possible occurrence of varietal differences in the natural abundance of cadmium in rice grains. There was no correlation between the cadmium levels and the duration of ripening in each variety, suggesting that these differences could be partly attributed to some physiological characteristics of the rice varieties.     

Liquid chromatographic-atomic absorption spectrophotometric method for determination of methyl mercury in seafood: collaborative study

A previously developed method that uses a simplified sample preparation procedure and atomic absorption detection of liquid chromatographic eluates for the determination of methyl mercury in seafood has been collaboratively studied. The unique feature of the method involves the use of a specially designed interface for the generation of mercury vapor. Methyl mercury is isolated from the blended sample by chloroform elution from a diatomaceous earth-hydrochloric acid column. The organomercury compound is then extracted into a small volume of 0.01M sodium thiosulfate solution. An aliquot of this solution is injected onto a Zorbax ODS column and eluted with methanol-ammonium acetate solution (3 + 2), pH 5.7, containing 0.01% mercaptoethanol. Mercury is detected by flameless atomic absorption spectrophotometry using the interface. The samples analyzed in the study were unspiked swordfish, unspiked and spiked lobster, and unspiked and spiked tuna. The spiked samples contained methyl mercury both above and below the U.S. Food and Drug Administration guideline level of 1 microgram Hg/g. Reproducibility relative standard deviations ranged from 10.5% at 1 microgram Hg/g to 18.2% at about 0.1 microgram Hg/g. Accuracy, measured by comparison to reference values obtained by the Associate Referee, ranged from 94.4 to 99.6%. The method has been adopted official first action.     

A simplified procedure for the determination of total mercury in soils

Abstract

A saraimplified procedure for the measurement of total mercury in soils and some preliminary results for Saskatchewan are presented. Soil samoles were digested in aqua regia at low temperatures, followed by determination of Hg with a simplified flameless atomic absorption technique. Hg levels in soils analyzed ranged from 0.003 to 0.071 ug/g.     

Rapid preparation of plant samples for cation analysis

Abstract

In the dry ashing of plant material for chemical analysis, the hot digestion on the steam bath of the ashed sample was replaced by the quantitative addition of dilute HCl and stirring very briefly to dissolve the ash. By waiting a few minutes for the particles to settle, there was no need to filter the solution prior to dilution with an automatic diluter and the determination of K, Na, Ca and Mg by atomic absorption spectrophotometry. The new procedure permits the handling of large batches of samples conveniently, eliminates the use of pipettes and volumetric flasks and decreases the risk of inadvertent contamination by sodium and therefore enhances accuracy. Precision was at least as good as with the standard procedure and the method is expected to be more suitable for use in conjunction with automated analytical techniques.     

Sources of error in the determination of Cd and Pb in plant material by atomic absorption

Abstract

Some difficulties were met when low levels of Cd and Pb were estimated in plant samples in this laboratory by atomic absorption spectrophotometry (AAS).

A modified procedure, based on methyl isobutyl ketone (MIBK) extraction of the metal complexes with ammonium pyrollidine dithio carbamate (APDC), has been developed for use on samples digested with HNO₃/HCIO₄. The procedure was compared with X‐ray fluorescence and with other AAS methods including those based on dry ashing. Dry ashing gave generally lower values for Cd and Pb. Improvement in conditions of digestion and analysis are described. Of these, the presence of small amounts of Fe in standards and unknown samples increases the stability and reproducibility of absorbance values, especially for cadmium.     

Screening method for determination of high levels of cadmium, lead, and copper in foods by polarized Zeeman atomic absorption spectrometry using discrete nebulization technique

A screening method for determination of cadmium, lead, and copper in foods was developed. The sample (1-3 g) is digested with HNO3-H2SO4-HClO4 in a centrifuge tube attached to a straight glass tube that prevents loss of HNO3 by volatilization. After digestion, potassium iodide, H2SO4, and MIBK (4-methyl 2-pentanone) are added, and the metals are extracted with MIBK as metal iodides. The MIBK solution is injected and the metals are determined by flame polarized Zeeman atomic absorption spectrometry using a discrete nebulization technique. Recoveries of metals from fortified milk powder, unpolished rice, fish, beef, peanut butter, apple, and cabbage were satisfactory. The analytical results for NBS Oyster Tissue and NIES Pepperbush, Chlorella, and Mussel agreed with certified or reference values except lead in Pepperbush. The limits of quantitation for cadmium, lead, and copper were 0.01, 0.09, and 0.02 ppm, respectively. This method is simple and safe for routine analysis of high levels of cadmium, lead, and copper in foods.     

凝乳方式对奶油干酪品质的影响

凝乳是干酪加工的关键环节,对奶油干酪的品质具有重要影响。通过对奶油干酪理化成分、产率、涂抹性的测定,比较了酶凝、酸凝、酸-酶互作凝乳3种方式对奶油干酪涂抹性的影响。结果表明,随着酸化程度的加深,奶油干酪的脂肪含量和蛋白质含量逐渐减少,含水率显著增加,校正产率、脂肪回收率和酪蛋白回收率降低。有酶高酸组(RHA)涂抹性最佳,其剪切功、屈服应力都分别为最小(19.23N·s、195.67Pa),与传统酸凝型奶油干酪(NR)相比,RHA的剪切功和屈服应力分别降低了17.04%和27.88%,干酪涂抹性得到明显改善。这为涂抹型奶油干酪的研发提供了技术基础。     

A convenient wet digestion procedure for multielement analysis of plant materials

Abstract

For the determination of total element contents in plant material by atomic spectrometry after wet digestion, both dissolution and oxidation of the matrix are necessary. This was achieved by a sequential digestion procedure using first hydrogen fluoride (HF) for dissolution of silicate, followed by oxidation with nitric acid (HNO₃) and hydrogen peroxide (H₂O₂). The final solution is 0.2M HNO₃, and contains only traces of HF. Application of the method for the determination of aluminium (Al), boron (B), calcium (Ca), cadmium (Cd), copper (Cu), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), sodium (Na), phosphorus (P), lead (Pb), sulfur (S), and zinc (Zn) in various materials showed good agreement with certified reference materials.     

A chemometric approach to the comparison of different sample treatments for metals determination by atomic absorption spectroscopy in aceto Balsamico tradizionale di Modena

A comparison of different digestion procedures has been carried out for the analysis of metal concentration in samples of vinegars and Aceto Balsamico Tradizionale of Modena (ABTM) coming from an unique barrel set. In particular, classical wet, dry ashing, and closed vessel microwave digestion procedure have been utilized and compared for each investigated species. In a few cases, direct metal determination on ABTM (without treatment procedure) is proposed as possible alternative to sample manipulation. Flame atomic absorption spectrometry was used for the quantification of iron and zinc, while graphite furnace atomic absorption spectrometry was used for all the other elements (i.e., chromium, manganese, cobalt, nickel, copper, cadmium, and lead). The comparison among the different sample treatments was carried out by the use of statistical and chemometric tools. In particular, principal component analysis and ANOVA approaches were used to discriminate between the diverse analytical methods. Furthermore, for all the dissolving techniques, the analytical metal recovery was always evaluated by the application of the recovery function on the same sample matrix. In general, the recoveries were fairly good, ranging from 90 to 103%, except for Cd and Pb with dry ashing, which showed recovery values close to 55% and 67%, respectively. As regards the metals concentration of the investigated samples, the experimental data reveal for some species the presence of concentration slightly over the legal limit fixed for wine and wine vinegar.     

Rapid,Wet Oxidation Procedure for the Estimation of Silicon in Plant Tissue

Abstract

The quantification of silicon (Si) in plant samples is being requested more frequently, especially in agricultural laboratories associated with the determination of nutritional requirements of sugarcane (Saccharum officinarum L.) and rice (Oryza sativa L.). The analysis of plant material for Si can be protracted, especially if laboratories do not have access to X‐ray flourescence (XRF) instrumentation and large numbers of samples are involved. A simplified procedure using equipment considered standard in most agricultural laboratories is reported. Dry, ground plant material is subjected to nitric acid/peroxide oxidation in a low‐pressure laboratory microwave digestion system. The hydrated silica liberated from the organic matrix is dissolved in a small volume of sodium hydroxide solution also using the microwave digestion system. Silicon is measured by inductively coupled plasma atomic emission spectrometry (ICP‐AES). This method gives results that are linearly correlated with the much slower conventional techniques and avoids using hazardous chemicals (hydrofluoric acid) sometimes employed in other microwave methods.     

The determination of cadmium in soils,plants and fertilizers by dithizone extraction and atomic absorption spectroscopy

Abstract

Methods are proposed for the determination of cadmium in soils, plants and fertilizers.

Soil is first dissolved by treatment with hydrofluoric and hydrochloric acids and plant material is digested with nitric‐perchloric‐sulphuric acids. The cadmium is then extracted from the resulting solutions as the dithizone complex. After destruction of the dithizone the cadmium is dissolved in dilute hydrochloric acid and determined by atomic absorption spectroscopy. Cadmium in phosphatic fertilizers is determined directly by atomic absorption measurement on hydrochloric acid digests of the fertilizer.

The proposed methods have precision adequate for the study of cadmium in soil‐plant systems, the limits of detection being: plant material, 0.004 ppm Cd; soils, 0.02 ppm; and phosphatic fertilizers, 1 ppm.     

Temperature-programmable furnace for ashing of foods in trace metal analysis

The use of programmable furnace in preparing samples for determining cadmium, lead, copper, and zinc by differential pulse anodic stripping voltammetry or atomic absorption spectrophotometry is convenient and time-saving. Recovery data for these 4 metals in various foods (tuna, sardines, and milk) were 93-96% for 0.01-1 ppm cadmium, 96-114% for 0.05-5 ppm lead, 100-108% for 2-10 ppm copper, and 97% for 10 ppm zinc.     

Determination of trace cadmium in rice by flow injection on-line filterless precipitation-dissolution preconcentration coupled with flame atomic absorption spectrometry

A simple, environmentally friendly, cost-effective, and sensitive method was developed for the determination of trace cadmium in rice by flow injection (FI) on-line precipitation preconcentration coupled with flame atomic absorption spectrometry (FAAS). The precipitation preconcentration of trace cadmium was achieved by on-line merging of the sample and ammonia solutions. The resultant precipitates were on-line collected by a knotted reactor (KR) without filtration. A solution of 1 mol L(-1) HNO(3) was employed to dissolve the collected precipitates and to deliver the analyte into the FAAS system for on-line detection. Preconcentration at a sample loading flow rate of 3.8 mL min(-1) for 35 s gave an enhancement factor of 44 and a detection limit (3sigma) of 0.002 microg g(-1) for the solid sample with a sample throughput of 72 h(-1). The precision (RSD, n = 11) was 2.0% at the 4.0 microg L(-1) level. The concentration of cadmium in a certified reference material (GBW 08511, rice flour) by the developed method using simple aqueous standards for calibration was in good agreement with the certified value. The proposed method was also successfully applied to the determination of trace cadmium in locally collected rice samples.     

Leak in evaporated milk by anodic stripping voltammetry and atomic absorption spectrophotometry: cooperative interlaboratory study

The results of a cooperative study on the determination of lead in evaporated milk, using a double blind referee technique, are reported. This study was designed to determine the normal variability of methods currently used for lead analysis by canned food industry laboratories. Twenty-three laboratories participated in this study. Each laboratory was instructed to use atomic absorption spectrophotometry (AOAC 25.065), anodic stripping voltammetry, or carbon rod atomic absorption spectrophotometry. Overall, the results appear to be in close agreement with the spiking levels. The coefficient of variation for all laboratories was 36.0% at the 0.15 ppm lead level and 16.8% at the 0.40 ppm lead level.     

土壤微量节肢动物组织中镉测定方法的改进

Highly precise and reliable determination of heavy metals in soil micro-arthropod tissues remains a challenge because of the small size of the animals and their typical low abundance in metal-contaminated agricultural soils. The present study sought to develop a method for cadmium(Cd) determination in soil micro-arthropods by optimizing the sample digestion procedure, reducing sample weight, modifying sample pre-treatment and validating the methodology with field samples. The optimized digestion conditions comprised a sample mass of 50–150 μg, digestion reagent of nitric acid:hydrogen peroxide(3:1), digestion temperature of 105℃,digestion period of 3 h and digestion volume of 30 μL. Defecation of the standard Collembola Folsomia candida(92 h) and the indigenous Collembola Onychiurus yodai(42 h) and ultrasonic cleaning of F. candida increased the accuracy of Cd determination.The recovery of Cd using the refined procedure was 98.9% and the limits of detection and quantification were 0.002 and 0.008 μg L~(-1), respectively. The within-batch precision values were 3%. The Cd concentrations in the tissues of the Collembola Isotoma sp.collected from a range of metal-contaminated fields determined by the improved method were consistent with the Cd concentrations in the field soils. The results indicate that the optimized method can be used for more accurate or reliable determination of Cd concentrations in soil micro-arthropod tissues.