Determination of molybdenum in plant tissue by graphite furnace atomic absorption spectrophotometry (GFAAS)

Abstract

The analysis of molybdenum in plant tissue using graphite furnace atomic absorption spectrophotometry (GFAAS) is described. The method involved wet digestion using a mixture of sulphuric, nitric and perchloric acids followed by a solvent extraction procedure. Molybdenum was extracted into di‐iso butyl ketone (DIBK) as the iron‐thiocyanate complex. The extract was then analysed for molybdenum by GFAAS.

The results of analyses of the reference plant materials (orchard leaves and citrus leaves) of the National Bureau of Standards (NBS) compared very well with the certified values. Other types of plant tissue were also analysed and the results correlated well with those obtained by an alternative method.     

Determination of vitamin B12 in dry feeds by atomic absorption spectrophotometry.

Vitamin B12 was determined in dry feeds by atomic absorption spectrophotometry (AAS). Samples containing B12 were extracted with an assay solution, 5 g EDTA was added to the filtrate, the pH was adjusted to 7 with NH4OH, and 5 g charcoal was added. The charcoal was removed by filtering through ashless paper which was then placed in a beaker and ashed at 600 degrees C. After dissolving the cobalt oxide from the ash in 5N HNO3, cobalt content was determined by using AAS. To determine mg B12/lb feed, ppm cobalt in the feed is multiplied by 10.43. The sensitivity of the proposed procedure is 1 mg vitamin B12/lb. The procedure is rapid and precise, and results compare favorably with AOAC method 43.109.     

火焰原子吸收分光光度法测定污染土壤中5种重金属

采用微波消解法预处理待测土壤,火焰原子吸收分光光度法测定污染土壤消解液中的锌、铜、铅、镉、铬5种重金属.方法简便、灵敏、准确,土壤中锌的相对标准偏差为1.2%;铜的相对标准偏差为1.9%;铅的相对标准偏差为1.2%;镉的相对标准偏差为5.2%;铬的相对标准偏差为1.8%.方法的加标回收率锌为76.8%～104%;铜为86.9%～95.3%;铅为83.0%～94.4%;镉为83.2%～91.9%;铬为90.9%～96.1%,适用于污染土壤中重金属含量的测定.     

Determination of arsenic and selenium in whole fish by continuous-flow hydride generation atomic absorption spectrophotometry

A combined wet chemical and dry ash digestion and use of a continuous-flow hydride generator coupled with a flame-heated quartz cell enabled the simple, precise, and highly automated atomic absorption determination of arsenic and selenium in tissues of whole fish. Percent relative standard deviation averaged 4% for each element; method detection limits (micrograms/g dry wt) were about 0.06 for arsenic and 0.04 for selenium. Digestion of samples proceeded with little operator attention and without perchloric acid. Analysis for arsenic as As(V) simplified sample preparation but care had to be exercised to avoid interferences from high concentrations of selenium.     

Determination of trace elements in foods by HCl-HNO3 leaching and flame atomic absorption spectroscopy

Aluminum, iron, tin, zinc, calcium, magnesium, nickel, copper, chromium, cadmium, and potassium in foods can be extracted by HCl-HNO3 leaching and determined quantitatively using flame atomic absorption spectroscopy (AAS), with recoveries ranging from 90 to 110%. Thirty to 40 samples of almost any type of food sample can be analyzed routinely for 2 elements in 4-5 h. In contrast, one or 2 days are required when a wet-ash or dry-ash technique is used. Extraction consists of weighing 2-10 g samples into 125 mL Erlenmeyer flasks, adding 20 mL concentrated HCl-HNO3 (9 + 1), then heating in a 82- 93 degrees C water bath for 30 min. After cooling, samples are diluted to volume in 50 mL Nessler tubes and then filtered through No. 541 or 540 Whatman paper. The filtrate is analyzed directly by AAS.     

The determination of total lead in soil by atomic absorption spectrophotometry

A method is described for the determination of total lead in soil by atomic absorption spectrophotometry. The sample is digested with hot nitric acid. The dry residue is taken up in hydrochloric acid and excess iron is removed by extraction with acetylacetone‐chloroform. Lead is then extracted using the system DDC‐MIBK. The organic phase can be sprayed directly into the flame.

The method is not affected by elements occurring in contaminated soils. Iron is removed because a slow‐forming precipitate of the Fe‐DDC‐complex blocks the nebuliser system. The method is an improvement on other methods because no sulfuric acid is used for digestion, and therefore losses of lead by precipitation or occlusion are avoided. Tests confirm that the recommended method gives complete recovery of lead.

Lead can be determined in the range from 4 to 240 ppm in the soil. A standard soil sample has been analyzed, yielding a mean value of 125 μg Pb/g soil with a relative standard deviation of 2.4%.     

Measurement of trace levels of total aluminum in foods by atomic absorption spectrophotometry

A graphite furnace atomic absorption spectrophotometry method was used to determine the total aluminum content of various foods found in an average American diet. The food products were ashed in platinum dishes, and the inorganic residue was fused using a sodium carbonate-sodium borate mixture. The fusion step allowed detection of all the various forms of aluminum found in food products. A L'vov platform was used in the graphite furnace to increase the sensitivity of the assay. Care was taken throughout the analysis to avoid various sources of aluminum contamination such as glass and porcelain dishes. All reagents were ultra-pure grade and were continuously monitored for aluminum content. Sodium borate used in the fusion flux mixture had previously been extracted with 8-hydroxyquinoline in chloroform to remove any aluminum present. Both raw and cooked foods were analyzed for aluminum with this method. Average recoveries of aluminum from food products ranged from 84 to 112%. The overall coefficient of variation of this method on the food products tested was 10%.     

Determination of cadmium, copper, and lead in sodium chloride food salts by flame atomic absorption spectroscopy

A method for determination of Cd, Cu, and Pb in sodium chloride food salt samples has been developed. It consists of extraction in 4-methyl-2-pentanone of the complexes formed with ammonium pyrrolidine dithiocarbamate and further analysis of the extracts by flame atomic absorption spectroscopy. Detection limits in ng/g salt were 0.2 for Cd, 0.7 for Cu, and 10.0 for Pb. The coefficients of variation of 12 independent analyses were 13% for Cd (at a level of 0.4 ppb), 18% for Cu (1.6 ppb), and 5% for Pb (40 ppb). The recoveries were 100 +/- 0% for Cd, 115 +/- 14% for Cu, and 100 +/- 13% for Pb.     

Determination of silver in soils by atomic absorption spectrometry

A method for the determination of Ag in soils using atomic absorption spectrometry is described. The method involves the extraction of Ag from soil by boiling with 6 M HC1 followed by separation of the extracted Ag into methylisobutylketone (MIBK) using sodium N, N-diethyldithiocarbamate (DDTC) as a complexing agent. Silver is determined in the MIBK by direct aspiration into a flame atomic absorption spectrophotometer. The detection limit (S/N=2) for this method is 0.0001 mg L^?1 for aqueous solution and 0.002 mg kg^?1 for soil. The Ag content of even unpolluted soils can be determined by this method. The determination of Ag using this method was shown to be unaffected by the presence of various ions in the soil. The method was able to recover nearly 100% of Ag added to soil and approximately the same amounts of soil Ag were determined using this method as with HF-H₂SO₄ decomposition. For 3 reference soils of the Canadian Certified Reference Materials Project (CCRMP), the Ag values obtained by this method were the same as the values determined by Ebarvia et al. (1988). The amounts of Ag in the soils sampled in the Ichi River basin and the Ichi River sediments were determined using this method. This area has been polluted by Cd, Cu, Pb, and Zn discharged from the Ikuno Mine and Smelter. The Ag values ranged from 0.27 to 6.89 mg kg^?1 which were much higher than the values of the unpolluted soils.     

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.     

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.     

Survey of total and bioavailable chromium in grain and cereal products by atomic absorption spectrophotometry

The chromium content of samples of cereals, legumes, oil seeds, and alimentary pastes (in the latter, bioavailable chromium as well) was determined by atomic absorption spectrophotometry. The chromium content in whole cereals differs substantially and is mostly concentrated in pericarps. Variations occur not only among different types of cereals, but also among cereals of the same type, depending on the areas of origin. Concentration varies substantially even in samples of legumes and oil seeds. The content of bioavailable chromium (ethanol-extractable) is, in most cases, more than 50% of the total chromium amount. This makes these products particularly interesting as dietary supplements.     

Effect of placement of coated urea fertilizer on root growth and rubidium uptake activity in soybean plant

Abstract

We reported in the previous paper (Takahashi et al. 1991) that the deep placement of slow release N fertilizer (coated urea) contributed to a stable increase of soybean (Glycine max L. Merr.) yield. In the previous study we observed that the deep placement of coated urea did not depress appreciably the nitrogen fixation by root nodules although fertilizer N was efficiently utilized. We assumed that the N absorbed from the roots in the deep layers did not cause nodule senescence, contributed to the maintenance of the leaf activity during the maturation stage, and that the increase in the availability of carbohydrate and N improved seed production. In the current report the effects of placement of coated urea fertilizer on the root growth and activity were studied by measuring the root dry weight and Rb absorption activity.     

Determination of iron in soils by flow injection atomic absorption spectrometry

Abstract

A single‐channel flow injection system was optimized for the determination of available iron (Fe) in soil extracts by atomic absorption spectrophotometry. This method of introducing the samples in the spectrophotometer worked particularly well in preventing blockage of the burner head which was observed in the conventional introduction of Fe for its determination by atomic absorption spectrophotometry. The appropriate selection of the manifold parameters, such as injection volume, tube length and flow rate, allowed introduction of any soil extract without requiring any pre‐treatment. This system allowed determinations at a detection limit of 0.36 mg L^‐1 to 5 mg L^‐1, with an output of 300 determinations per hour. The results obtained for analysis of 15 soil extracts were in good agreement with those provided by the colorimetric method, with average relative deviations of 1.6%. Relative standard deviations of 4.8, 2.5, and 2.3% were obtained for contents of 1.03, 1.85, and 3.99 mg Fe L^‐1, respectively.