原子捕集-导数火焰原子吸收光谱法测定中草药中的微量锌

提出了原子捕集－导数火焰原子吸收光谱法，考察了捕集管位置，火焰状态、冷却水流量、捕集时间、导数测量系统灵敏度档等实验条件对灵敏度的影响。在测量系统20mV/min灵敏度档下，捕集5min，特征浓度为0．037ng/mL，较常规火焰原子吸收光谱法提高了1243倍。     

Direct determination of cadmium in natural waters by electrothermal atomic absorption spectrometry without matrix modification

A procedure for the determination of cadmium in fresh, coastal and estuarine waters by polarized Zeeman-effect graphite-furnace atomic absorption spectrometry is validated by using lake waters and seawater. The limit of detection for freshwaters is <2 ng l^?1 cadmium. Undiluted seawater can be analyzed directly without the addition of matrix modifiers with the aid of a stabilized temperature platform. The instrument is calibrated with diluted NBS SRM 1643a (Trace Elements in Water). Analytical performance was tested extensively with fresh and brackish water samples and procedures were worked out to ensure that a high degree of accurately is achieved consistently.     

Determination of lead traces in water and liqueurs by derivative atom trapping flame atomic absorption spectrometry

 A new method for the direct determination of lead traces using derivative atom trapping flame atomic absorption spectrometry (DAT-FAAS) with an improved water-cooled stainless steel trapping equipment in an air-acetylene flame was investigated. The optimum conditions concerning the sensitivity were studied. For a 1 min collection, the characteristic concentration (given as derivative absorbance of 0.0044) and the detection limit (3s) were 1.4 ng/mL and 0.27 ng/mL, respectively. This is 361 and 74-fold better than those of the conventional flame atomic absorption spectrometry (FAAS) and comparable to those of graphite furnace atomic absorption spectrometry (GFAAS). The detection limit and sensitivity of DAT-FAAS for a 3 min collection time were 2 and 3 orders of magnitude higher than those of conventional FAAS. The present method was applied to the determination of lead in water and liqueur samples with a recovery range of 94–108% and a relative standard deviation of 3.5–5.6%. Received: 10 January 1996/Revised: 9 December 1996/Accepted: 20 December 1996     

Direct determination of molybdenum in mineral waters by atomic absorption spectrometry with electrothermal atomization

A new method for the direct determination of molybdenum by ETA-AAS in mineral waters without prior separation or concentration is proposed. With careful control of the graphite furnace conditions selective volatilization of the salt matrix is successfully attained. The possible spectroscopic interference due to common metals as well as the reproducibility, precision and repeatability of the method has been studied and the molybdenum content of 21 mineral waters measured.     

Direct determination of cadmium in urine by electrothermal atomic absorption spectrometry after in situ electrodeposition

Determination of cadmium in urine by ETAAS suffers from severe interferences deteriorating the precision and accuracy of the analysis. Electrodeposition step prior to ETAAS allows to avoid interferences and makes cadmium determination possible even at ultratrace levels. The proposed procedures involve electrolytic deposition of cadmium from acidified urine on previously electrolytically deposited palladium film on a graphite atomizer tube, followed by removal of residual solution, pyrolysis and atomization. Both electrodeposition processes take place in a drop of the respective solution (palladium nitrate modifier and acidified urine, respectively), when Pt/Ir dosing capillary serves as an anode and the graphite tube represents a cathode. The voltage is held at −3.0 V. Matrix removal is then accomplished by withdrawal of the depleted sample solution from the tube (procedure A) or the same but followed by rinsing of the deposit with 0.2 mol l⁻¹ HNO₃ (procedure B). The accuracy of both procedures was verified by recovery test. Detection limits 0.025 and 0.030 μg Cd/l of urine were achieved for A and B procedures, respectively. Both procedures are time consuming. The measurement cycle represents 5 and 7 min for A and B procedures, respectively.     

Direct determination of cadmium in urine using graphite furnace atomic absorption spectrometry with Zeeman-effect background correction

A procedure is described for the direct determination of cadmium in human urine using graphite furnace atomic absorption spectrometry with Zeeman-effect background correction. Except for a straightforward 1 + 1 V/V dilution of samples with 1.5% nitric acid, no matrix modifier or sample pre-treatment was necessary, thus reducing the risk of contamination. The concentration of cadmium in urine was evaluated directly from a calibration graph prepared using a metal-spiked human urine pool. In this way the time-consuming method of standard additions was avoided, permitting an increased sample throughput (120-150 samples per day; 90 s per analysis) with minimal attention of the analyst. In routine use, the precision (both within day and day to day) and limit of detection were of the order of less than 10% and 0.05 micrograms l-1 of Cd, respectively. The method is suitable for the biological monitoring of cadmium in the general population or in occupationally exposed persons.     

Direct determination of parts-per-billion levels of germanium in botanical samples and coal fly ash by graphite furnace atomic absorption spectrometry

 Parts-per-billion levels of germanium can be determined directly by graphite furnace atomic absorption spectrometry (GFAAS) using palladium plus strontium as a mixed modifier resulting in pyrolysis temperatures up to 1400 °C without loss of germanium. At this temperature the matrix effect including the most troublesome sulfate interference can be eliminated. Palladium plus strontium nitrate is advantageous compared to palladium alone or palladium plus magnesium nitrate; an amount of 15 μg of sulfate does not show any interference on the determination of 1 ng of germanium. The method was successfully applied to the determination of ng/g levels of germanium in botanical samples and coal fly ash after thermal decomposition of the samples in a mixture of acids using a pressure bomb. The results were consistent with the reference values given for botanical samples and coal fly ash with a recovery range of 96.4∼103.4% Received: 16 September 1996/Revised: 10 December 1996/Accepted: 14 January 1997     

Hydride generation for the direct determination of trace and ultra-trace level of arsenic and antimony in waters using derivative atomic absorption spectrometry

A new method is developed for the direct determination of trace and ultra-trace level of arsenic and antimony in waters by hydride generation derivative atomic absorption spectrometry (DHGAAS). The signal model and fundamentals of DHGAAS are described. The effects of atomization temperature, argon flow rate, acidity and concentration of KBH(4)and KI were investigated and analytical conditions were optimized. The sensitivities for arsenic and antimony were increased 36.4 and 27.6 times better than those of conventional hydride generation atomic absorption spectrometry (HGAAS). For a 2 mV min(-1) sensitivity range setting, the characteristic concentration was 0.003 microg L(-1) for arsenic and 0.004 microg L(-1)for antimony, and the detection limits (3sigma) were 0.015 micro g L(-1) for arsenic and 0.020 microg L(-1) for antimony. The proposed method was applied to the determination of arsenic and antimony in several water samples with satisfactory results.     

Selenium determination using ethylation and on-line trapping/detection by graphite furnace atomic absorption spectrometry

An on-line system for the continuous ethylation of selenium (IV) in combination with trapping and detection of the produced diethylselenide in the coated AAS graphite furnace was developed. Due to the slow kinetics of the ethylation the volume of the reaction coil and the reaction time had to be increased to 5.5 mL and 80 s, respectively. The sensitivity of the method was comparable with that of the hydride generation in the same system and the relative standard deviation was 6–10%. The determination of Se(IV) in real samples after the most widely used digestion with nitric acid could not be accomplished, because of the drastic signal depression caused by this acid.     

Selenium determination using ethylation and on-line trapping/detection by graphite furnace atomic absorption spectrometry

An on-line system for the continuous ethylation of selenium (IV) in combination with trapping and detection of the produced diethylselenide in the coated AAS graphite furnace was developed. Due to the slow kinetics of the ethylation the volume of the reaction coil and the reaction time had to be increased to 5.5 mL and 80 s, respectively. The sensitivity of the method was comparable with that of the hydride generation in the same system and the relative standard deviation was 6–10%. The determination of Se(IV) in real samples after the most widely used digestion with nitric acid could not be accomplished, because of the drastic signal depression caused by this acid. Received: 10 June 1997 / Revised: 27 October 1997 / Accepted: 1 November 1997     

Ultratrace determination of tin by hydride generation in-atomizer trapping atomic absorption spectrometry

A quartz multiatomizer with its inlet arm modified to serve as a trap (trap-and-atomizer device) was employed to trap tin hydride and subsequently to volatilize collected analyte species with atomic absorption spectrometric detection. Generation, atomization and preconcentration conditions were optimized and analytical figures of merit of both on-line atomization as well as preconcentration modes were quantified. Preconcentration efficiency of 95 ± 5% was found. The detection limits reached were 0.029 and 0.14 ng mL⁻¹ Sn, respectively, for 120 s preconcentration period and on-line atomization mode without any preconcentration. The interference extent of other hydride forming elements (As, Se, Sb and Bi) on tin determination was found negligible in both modes of operation. The applicability of the developed preconcentration method was verified by Sn determination in a certified reference material as well as by analysis of real samples.     

Rapid determination of cadmium in biological tissues by microsampling-cup atomic absorption spectrometry

A microsampling-cup method of atomic absorption spectrometry has been applied to the determination of cadmium in biological tissues. Sample preparation involves homogenizing a known weight of the tissue with a known volume of water, pipetting a suitable dilution of the homogenate into a microsampling cup and drying. Aqueous calibration standards are used. Sensitivity, linear range and reproducibility are adequate for this application. Simplicity and speed make this method preferable to any other reported to date.     

The determination of cadmium in geological materials by flameless atomic absorption spectrometry

The use of graphite-furnace atomic absorption spectrometry for the determination of cadmium in rocks and sediments by direct atomization from the solid state is described. At the 10–1000 p.p.b. level, the relative standard deviation is ± 10–20 %. Samples were ground to 100 mesh and, if necessary, 325 mesh before analysis. Two resonance lines were employed: 228.8 nm for less than 5 p.p.m. cadmium and 326.1 nm for levels above 5 p.p.m. Instrumental parameters were optimized to produce maximum peak heights. Results are given for a series of standard rocks and for stream sediment samples.     

Direct determination of cadmium in high-purity metals by flame atomic fluorescence spectrometry

Raschig rings used as a safety mechanism, to avoid critical reactions in solutions containing radioactive materials, are usually made of borosilicate glass. Since boron is the active neutron absorbing ingredient, it is important to determine the boron content in the Raschig rings at any given time. A method has been developed to determine rapidly the boron content of borosilicate glasses. Ion exchange and potentiometric measurement are used to determine boron as the tetrafluoroborate ion. The precision of the method is ±2.0 mV. The average difference between values of a wet chemical analysis and those of the potentiometric method is 7.7%.     

Determination of copper and zinc in serum by derivative atomic absorption spectrometry using the microsampling technique

A method has been developed for the determination of copper and zinc in the serum of rats by derivative microsampling flame atomic absorption spectrometry (D-MFAAS). The microsampling volume, solution uptake rate and other figures of merit of the proposed methodology were studied. For a 100 microl volume, the characteristic concentrations and detection limits (3s) of D-MFAAS were 0.023 and 0.013 microg ml(-1) for copper and 0.0066 and 0.0080 microg ml(-1) for zinc, which were 4.5-6.5-fold better than those of microsampling flame atomic absorption spectrometry (MFAAS). The detection limits and sensitivities of D-MFAAS were 6.4- and 16-fold for 300 microl volume for copper, 14- and 13-fold for 250 microl volume for zinc, better than those of MFAAS. The method demonstrates high tolerance to interferences, and the analytical results obtained for a certified reference material, GBW 08551 Pork Liver, were in good agreement with the certified values. The recovery with the standard additions method was good, in the range 97.6-101.5%, and precisions (relative standard deviations) obtained for a diluent sample containing 0.5 microg ml(-1) copper and 0.7 microg ml(-1) zinc were 4.0% and 3.5% (n = 15) for copper and zinc, respectively.     

Direct determination of vanadium in high saline produced waters from offshore petroleum exploration by electrothermal atomic absorption spectrometry

The present work reports the development of a methodology for the direct determination of vanadium in high saline waters derived from offshore petroleum exploration employing electrothermal atomic absorption spectrometry. Such waters, usually called produced waters, present complex composition containing various organic and inorganic substances. In order to attain best conditions (highest sensitivity besides lowest background) for the methodology, studies about the effects of several variables (evaluation of pyrolysis and atomization temperatures, type of chemical modifier, concentration of modifier and pyrolysis time) and the convenient calibration strategy were performed. Best conditions were reached with the addition of 10 μg of NH₄H₂PO₄ as chemical modifier employing pyrolysis (during 10 s) and atomization temperatures of 1500 and 2700 °C, respectively. Obtained results indicated that, in this kind of sample, vanadium can be determined by standard addition method or employing an external calibration approach with standard solutions prepared in 0.8 mol l⁻¹ NaCl medium. In order to evaluate possible matrix interferences, a recovery test was performed with five spiked samples of produced waters. The limit of detection, limit of quantification and relative standard deviation in 0.8 mol l⁻¹ NaCl medium were also calculated and the derived values were 1.9 μg l⁻¹, 6.3 μg l⁻¹ and 5.6% (at 10 μg l⁻¹ level), respectively.     

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.     

Direct determination of tin in tap waters by electrothermal atomization atomic absorption spectroscopy

Summary A method is described for the direct determination of tin in tap waters by electrothermal atomization atomic absorption spectroscopy (ETA-AAS), using magnesium-nitric acid and palladium-magnesium as chemical modifiers. The charring and atomization temperatures and times, and the amount of modifier were optimized. The calibration and addition graphs, detection limit, quantitation limit, precision, accuracy, interferences and characteristic mass were also investigated. The method was applied to the determination of tin in tap water samples.     

Direct determination of phosphorus in vegetable oils by electrothermal atomic absorption spectrometry

An approach to the practical implementation of the standard method of the direct determination of phosphorus in vegetable oils by electrothermal atomic absorption spectrometry with automated sample injection was proposed. Analytical advantages of the use of a graphite platform and a lanthanum modifier prepared on the basis of vegetable oil are shown. The developed procedure provides the monitoring of the concentration of phosphorus in vegetable oils of various types within the range from 10 to 790 mg/kg with a satisfactory accuracy and precision.