Optimization and validation of arsenic determination in foods by hydride generation flame atomic absorption spectrometry

A hydride generation flame atomic absorption spectrometric method was developed and optimized to quantitate arsenic (As) in foods. A wet digestion of the samples with HNO3 + H2O2 was performed and excess oxidants were eliminated by addition of hydrochloric acid and urea. As5+ in As3+ was then reduced by potassium iodide. The As3+ solution was analyzed by generation of arsine with sodium tetrahydroborate. As determination ranged from 2.5 to 20 microg/L, with a determination coefficient of 0.997. The limits of detection (LOD) and quantitation (LOQ) were 0.6 and 2.1 microg/L, respectively. The method was validated and good results were obtained for recovery, precision, accuracy, LOD, and LOQ. This method is now used to analyze foods from Rwanda.     

High performance flow flame atomic absorption spectrometry for interference-free trace determination

In High Performance Flow Atomic Spectrometry (HPF-AS), the aerosol is generated by injecting the sample solution into the gas mixing chamber with the aid of an HPLC pump (Hydraulic High Pressure Nebulization, HHPN, working pressure about 200 bar). Using an additional analytical HPLC column, between sample injection valve and nebulization nozzle, the elements under investigation can be separated from interfering elemental traces or major components (High Performance/Pressure Flow System, HPF). The elements to be determined and the interfering substances reach the flame at different times. This means, for example, that traces of Mg in solutions containing aluminum can be determined without interference. Compared to pneumatic nebulization, there is a 20 fold increase in the detection power when determining calcium in a saturated NaCl solution. HPF-AS is a rapid and sensitive method which allows separation of the calcium from the matrix with subsequent determination in less than 90 s.Dedicated to Professor Dr. Dieter Klockow on the occasion of his 60th birthday     

Organic solvents as interferents in arsenic determination by hydride generation atomic absorption spectrometry with flame atomization

Interference effects of various organic solvents miscible with water on arsenic determination by hydride generation atomic absorption spectrometry have been studied. Arsine was chemically generated in continuous flow hydride generation system and atomized by using a flame atomizer able to operate in two modes: miniature diffusion flame and flame-in-flame. The effects of experimental variables and atomization mode were investigated: tetrahydroborate and hydrochloric acid concentrations, argon, hydrogen and oxygen supply rates for the microflame, and the distance from the atomization region to the observation zone. The nature of the species formed in the flame due to the pyrolysis of organic solvent vapors entering the flame volume together with arsine is discussed. The observed signal depression in the presence of organic solvents has been mainly attributed to the atomization interference due to heterogeneous gas–solid reaction between the free arsenic atoms and finely dispersed carbon particles formed by carbon radicals recombination. The best tolerance to interferences was obtained by using flame-in-flame atomization (5–10 ml min^− 1 of oxygen flow rate), together with higher argon and hydrogen supply rates and elevated observation heights.     

Simple mode of zeeman splitting of absorption lines in atomic absorption spectrometry

Simple equipment is described for exploiting the normal Zeeman splitting of atomic absorption lines in external alternating magnetic fields of various geometry which is suitable for flameless and flame techniques. High-level continuous or background absorption can be eliminated in this way. This is demonstrated for the determination of traces of copper and molybdenum with a carbon rod (Varian CRA 90).     

On-line hyphenation of hydride generation with in situ trapping flame atomic absorption spectrometry for arsenic and selenium determination.

The analytical performances of coupled hydride generation, integrated atom trap (HG-IAT) atomizer flame atomic absorption spectrometry (FAAS) systems were evaluated for determination of As and Se in biological and environmental reference materials. Arsenic and Se hydrides are atomized in air-acetylene flame-heated IAT. A new design of HG-IAT-FAAS hyphenated technique that would exceed the operational capabilities of existing arrangements (a water-cooled single silica tube, double-slotted quartz tube or an "integrated trap") was investigated. A dramatic improvement in detection limit was achieved compared with that obtained using anyone of the above atom trapping techniques separately. The concentration detection limits were 4 and 3 ng ml(-1) for As and Se, respectively. For a 2 min in situ preconcentration time, sensitivity enhancement, compared to FAAS, were 875 and 833 folds for As and Se, respectively, using hydride generation, atom trapping technique. The sensitivity can be further improved by increasing the collection time. The relative standard deviations (RSDs) are of the order of 5 - 9% for this hyphenated technique. The designs studied include slotted tube, water-cooled single silica tube and integrated atom trap. The accuracy was assessed by analyses of NRCC DOLT-2 (Dogfish Liver) and NIST SRM 1648 (Urban Particulate Matter) reference materials. The measured As and Se contents in two reference materials were in satisfactory agreement with the certified values.     

Indirect flow-injection determination of ascorbic acid by flame atomic absorption spectrometry

A continuous-flow procedure is proposed for the indirect determination of ascorbic acid, based on its reducing properties because of the oxidation of its 1,2-enediol group. Iron(III) was injected into a 1,10-phenanthroline stream, which was mixed with a sample carrier and then with a sodium picrate solution stream. In these conditions the iron(III) was reduced to iron(II) by the ascorbic acid. Thus, the iron(II) formed reacts with 1,10-phenanthroline to form a charged red complex, which with picrate ion forms a stable red-orange uncharged ion-association complex that is adsorbed on-line on a non-ionic polymeric adsorbent (Amberlite XAD-4), proportionally to the ascorbic acid in the sample. The unadsorbed iron was determined by flame atomic absorption spectrometry. The proposed method allows the determination of ascorbic acid in the range 0.5–25 g ml^–1 with a relative standard deviation of 2.9% at a rate of ca. 90 samples h^–1. This method has been applied to the determination of ascorbic acid in pharmaceutical preparations, fruit juices and sweets. The results obtained in the analysis are compared with those provided by the 2,6-dichloroindophenol method.     

火焰原子吸收光谱法间接测定药剂中的核黄素

本文利用高碘酸钠对相邻羟基氧化作用的专属性,在一定介质中,高碘酸钠与核黄素完全反应后,过量的高碘酸的钠与硝酸铅或者硝酸铜生成沉淀,通过测定Pb<'2+>或者Cu<'2+>,建立了间接测定核黄素含量的方法.铅体系和铜体系测定的相对标准偏差(RSD)分别为4.8%和5.2%,检出限分别为0.6μg.mL<'-1>和0.5μ...     

The indirect determination of organic compounds by atomic absorption spectrometry

The feasibility of determining indirectly certain organic compounds by precipitation of insoluble silver compounds and determining the excess silver(I) by atomic absorption spectrometry (AAS) has been demonstrated. The determination of other compounds, such as alkylated barbiturates and mercaptans by similar methodology should be possible. Although direct AAS methods are preferable to indirect methods, the insolubility of many silver salts, the inherent sensitivity of the AAS method for silver, and the speed and convenience of AAS methodology suggests that under certain conditions, an indirect AAS method may be appropriate and the method of choice.     

On-line determination of trace levels of palladium by flame atomic absorption spectrometry

A preconcentration method is developed for the on-line determination of palladium in complex matrices with flame atomic absorption spectrometry (FAAS). The flow system comprised of a minicolumn filled with polyamine Metalfix-Chelamine resin which is highly selective for Pt(IV), Au(III) and Pd(II). Best preconcentration conditions are established by testing different resin quantities, sample and eluent solution volumes, and adsorption and elution steps flow rates. Sample volumes of 4.7 ml of palladium solutions resulted in an enrichment factor of twenty at the optimum hydrodynamic conditions. This value can be increased by injecting larger volumes of sample solution. The method is sensitive, easy to operate and permitted the determination of sub-mg l⁻¹ levels of palladium with a detection limit of 0.009 mg l⁻¹. The resin was used up to 60 times in consecutive retention-elution cycles without any appreciable deterioration in its performance. The applicability of this method was tested by determining the palladium content in synthetic geological samples as well as in the pellet-type used car catalyst reference material.     

A method for the quantitative decomposition of cluster compounds and the determination of rhodium and ruthenium by flame atomic absorption spectrometry

Summary Single crystals of cluster compounds were decomposed with two different methods. The hydrogen peroxide method is easy to use and no special equipments are needed. The autoclave method has proved to be more effective and led to the complete decomposition of all tested cluster compounds. Buffering with lanthanum sulphate or KHSO₄ was used to eliminate interferences caused by foreign metal ions and phosphorus. Results of measurements after decomposition of the cluster compounds with the two methods are shown.

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Quantitative Aufspaltung von Clusterverbindungen und Bestimmung von Rhodium und Ruthenium durch Flammen-AAS

     

Direct determination of arsenic in blood serum by electrothermal atomic absorption spectrometry

A method for the direct determination of arsenic in human blood serum is described. To suppress loss of arsenic by volatilization anal to remove chemical interferences in graphite-furnace atomic absorption spectrometry, the formation of involatile compounds with graphite, or with a matrix modifier is tested. With aqueous solutions, two sorts of interactions between graphite and arsenic are shown. But, in presence of serum, these interactions do not occur, Among 18 matrix modifiers tested, nickel gives the best sensitivity when used at high concentrations in the presence of Triton X-100. The proposed method allows direct arsenic determination, based on calibration with aqueous solutions. The method is applied to the serum of 20 normal subjects. The limit of detection is 0.4 μg l^?1 arsenic.     

流动注射在线萃取色谱分离原子吸收光谱法测定痕量铂

研究了流动注射在线分离富集原子吸收光谱法测定痕量铂的方法。以自制的GDX501-TBP萃取树脂为微型分离柱，在优化后的分离富集条件下，进样时间为60s，洗脱时间为45s。在线分离测定时间为3min，方法检出限为0．25μg/L，线性范围10—600μg/L，加标回收率为97．8％-103．6％，相对标准偏差3．49％-4．25％。方法已用于矿物管理样中铂的测定。     

Precipitation-dissolution system for silver preconcentration and determination by flow injection flame atomic absorption spectrometry

In this paper, flame atomic absorption spectrometry was used for the determination of silver in various materials. The proposed preconcentration method is based on the continuous precipitation of silver as p-dimethylaminobenzilidene-rhodanine (PDBR) complex and dissolution of the precipitate with potassium cyanide. EDTA was added to the sample solution to mask large concentrations of Fe(III), Ni(II), Cu(II), Zn(II), Pb(II), Co(II) and Al(III). An enhancement factor of 20 was obtained for a preconcentration time of 3 min, resulting in a sampling frequency of 16 h(-1). The detection limit (3sigma) in the sample solution was 5 ngml(-1). The relative standard deviation at 30 ngml(-1) level was 4.7%. Analytical results obtained for alloy, biological reference material and ore samples analyzed were in good agreement with the certified values and comparable to those obtained with other techniques.     

An automated extraction system for flame atomic absorption spectrometry

A manifold is described which allows continuous liquid/liquid extraction of aqueous solutions of metal ions. A fraction of the organic stream is separated and led into the sample loop of an injector. The injector is situated in an aqueous carrier stream which is pumped into the nebulizer. The organic extract enters as an undispersed plug into the carrier when the valve is actuated. A preconcentration factor of 5.5 resulting in a correspondent sensitivity increase is readily obtained for aqueous samples.     

Indirect atomic absorption spectrophotometric determination of arsenic

Arsenic has been determined indirectly by atomic absorption spectroscopy by estimating molybdenum in a solution of arsenomolybdic acid in methyl isobutyl ketone. Interference from other ions has been eliminated by prior extraction of arsenic as the diethyldithiocarbamate in diethyl ether. Arsenic has been determined in the presence of phosphate, silicate and germanium (IV). The method has also been used for the determination of arsenic in organic material.     

Arsine generation and determination of trace amounts of arsenic by atomic absorption spectrometry

Arsenic can be determined by atomic absorption spectrometry after reduction to arsine with potassium iodide, tin(II) chloride and zinc powder tablet; the arsine generated is carried into an argon-hydrogen flame by means of argon. Accuracy, precision and speed are satisfactory. Serious interferences arise only from nitric acid, lead, chromium and selenium.     

On-line determination of manganese in solid seafood samples by flame atomic absorption spectrometry

Manganese is extracted on-line from solid seafood samples by a simple continuous ultrasound-assisted extraction system (CUES). This system is connected to an on-line manifold, which permits the flow-injection flame atomic absorption spectrometric determination of manganese. Optimisation of the continuous leaching procedure is performed by an experimental design. The proposed method allows the determination of manganese with a relative standard deviation of 0.9% for a sample containing 23.4 μg g⁻¹ manganese (dry mass). The detection limit is 0.4 μg g⁻¹ (dry mass) for 30 mg of sample and the sample throughput is ca. 60 samples per hour. Accurate results are obtained by measuring TORT-1 certified reference material. The procedure is finally applied to mussel, tuna, sardine and clams samples.     

Direct flame solid sampling for atomic absorption spectrometry: determination of copper in bovine liver

In this work a new device for the direct introduction of solid samples into flame atomizers is proposed. The determination of copper in bovine liver reference material by flame atomic absorption spectrometry (FAAS) using a conventional air–acetylene flame was chosen as an example. Between 0.05 and 0.50 mg of the test sample was weighed directly into a small polyethylene vial connected to a glass chamber. A flow of air carries the test sample as a dry aerosol to a T-shaped quartz cell positioned above the burner in the optical path. The atomic vapor generated produces a transient signal of less than 3-s duration; integrated absorbance is used for signal evaluation. Optimized conditions for air flow rate, flame stoichiometry, etc., were evaluated. There was no statistical difference between the results from the proposed system, compared with those obtained by prior sample digestion and determination by conventional FAAS. No excessive grinding of the samples was required and samples with particle size less than 80 μm were used throughout. Background signals were always low and a characteristic mass of 1.5 ng was found for Cu. The proposed system allows the determination of 60 test samples in 1 h and it can be easily adapted to conventional atomic absorption spectrometers.     

A low-cost flame atomic absorption spectrometry method for determination of trace metals in aqueous samples

A simple and fast method for the extraction into xylene of sub mug l(-1) concentrations of metals using ammonium diethyldithiophosphate (DDTP) as a complexing reagent and their subsequent determination by flame atomic absorption spectrometry is described. The method was tested in sea water spiked with Au at a concentration of 3.0 mug l(-1). The extraction was carried out until the aqueous to organic phase ratio achieved a 1000-fold preconcentration of metal. Optimisation of extraction parameters and the effect of Fe interference was investigated. Sea water samples spiked with Au produced an average recovery of 95% and the detection limit (3sigma) in deionized water was 2.9 ng l(-1). High enrichment factors could be obtained due to the small final volume (mul) of organic solvent.