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.     

A direct solid sampling electrothermal atomic absorption spectrometry method for the determination of silicon in biological materials

A solid sampling electrothermal atomic absorption spectrometry method for direct determination of trace silicon in biological materials was developed and applied to analysis of pork liver, bovine liver SRM 1577b and pure cellulose. The organic matrix was destroyed and expelled from the furnace in the pyrolysis stage involving a step-wise increasing the temperature from 160 °C to 1200 °C. The mixed Pd/Mg(NO₃)₂ modifier has proved to be the optimum one with respect to the achievement of maximum sensitivity, elimination of the effect of the remaining inorganic substances and the possibility of using calibration curves measured with aqueous standard solutions for quantification. For the maximum applicable sample amount of 6 mg, the limit of detection was found to be 30 ng g^− 1. The results were compared with those obtained by different spectrometric methods involving sample digestion, by electrothermal atomic absorption spectrometry using slurry sampling, by wavelength dispersive X-ray fluorescence spectrometry and by radiochemical neutron activation analysis. The method seems to be a promising one for analysis of biological materials containing no significant fraction of silicon in form of not naturally occurring volatile organosilicon compounds. The still incessant serious limitations and uncertainties in the determination of trace silicon in solid biological materials are discussed.     

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.     

Indirect atomic absorption spectrometric method for the determination of silicon

Summary An indirect atomic absorption Spectrometric method for the determination of silicon is proposed which is based on the precipitation of an equivalent amount of lead molybdate from solutions treated with a known excess of lead ion and subsequent measurement of the lead ion remaining in solution. A typical calibration graph is linear for samples containing 0.5–7g silicon.

---

Zusammenfassung Eine indirekte Siliciumbestimmungsmethode durch Atomarabsorption wurde vorgeschlagen. Sie beruht auf der Fällung einer äquivalenten Menge Bleimolybdat aus Lösungen mit einem bekannten Überschuß von Bleiionen und nachfolgender Messung des Bleis im Filtrat. Die Eichkurve für Proben mit 0,5 bis 7g Silicium ist linear.

     

A sequential injection cold-vapor atomic absorption method for the determination of total mercury

A sequential injection (SI) method for the determination of mercury via cold vapor atomic absorption spectrophotometry is presented. The method differs from flow injection (FI) cold vapor methods for the determination of mercury because of the simplicity of the system required for the method: one pump, one valve, a gas-liquid separator, and an atomic absorption spectrophotometer equipped with a quartz cell. Under optimal conditions, the method has the following figures of merit: a linear ¶calibration range of 1.0 to 20 μg L^–1; a detection limit of 0.46 μg L^–1; and a precision of 0.90% RSD (8 μg L^–1). The procedure allows for a sampling rate of one injection per 80 s (excluding sample pretreatment). Results from the determination of mercury in water and fish specimens are also presented. The figures of merit of the method are compared to two other SI methods for the determination of mercury.     

A sequential injection cold-vapor atomic absorption method for the determination of total mercury

A sequential injection (SI) method for the determination of mercury via cold vapor atomic absorption spectrophotometry is presented. The method differs from flow injection (FI) cold vapor methods for the determination of mercury because of the simplicity of the system required for the method: one pump, one valve, a gas-liquid separator, and an atomic absorption spectrophotometer equipped with a quartz cell. Under optimal conditions, the method has the following figures of merit: a linear calibration range of 1.0 to 20 microg L(-1); a detection limit of 0.46 microg L(-1); and a precision of 0.90% RSD (8 microg L(-1)). The procedure allows for a sampling rate of one injection per 80 s (excluding sample pretreatment). Results from the determination of mercury in water and fish specimens are also presented. The figures of merit of the method are compared to two other SI methods for the determination of mercury.     

A comparison of gas-liquid separators for the determination of mercury by cold-vapour sequential injection atomic absorption spectrometry

Four different designs of gas-liquid separators were compared for the determination of mercury by cold-vapour generation atomic absorption spectrometry using the sequential injection technique for mixing the reacting solutions. Two atom cells were also compared, one with windows and one without. The results indicate that the use of a “detuned” nebulizer gave the poorest results. Similar results were obtained with a home-made separator based on a frit and a Perkin-Elmer FIAS Chemifold system with a small dead volume. The use of an atom cell with windows provided the best signals for the determination of mercury.     

A comparative study of the determination of phosphorus by electrothermal atomic absorption spectrometry and solution spectrophotometry

Graphite-furnace atomic absorption spectrometry (a.a.s.) and a spectrophotometric AutoAnalyzer method for phosphorus based on molybdovanadophosphate formation are compared. Only slight improvements in accuracy and reproducibility were obtained when SiC- or ZrC-coated graphite tubes replaced uncoated tubes. Perchloric acid enhanced the phosphorus signal in a.a.s. The digestion system was found to be critical for the AutoAnalyzer method. Digetion with nitric/perchloric acids gave higher recoveries than a micro-Kjeldahl digestion for most of the biological samples studied. Better accuracy was obtained by the a.a.s. method, whereas the AutoAnalyzer method was more reproducible. The methods were applied to NBS Oyster Tissue and Spinach, and fish samples.     

Preconcentration and atomic absorption determination of iron by sequential injection analysis

A sequential injection analysis (SIA) assembly for the atomic absorption determination of Fe(III) in natural waters is proposed. Iron is preconcentrated on a microcolumn packed with a chelating resin (Chelex 100) that is inserted in the manifold. The sample is passed through the column and the iron retained by the resin is subsequently eluted with 2 M HNO(3). The proposed SIA system affords automatic preconcentration, elution, detection of Fe(III), data acquisition and treatment. When 9 ml of iron solution containing 0.4 or 1 mg l(-1) was passed through the resin, the retention efficiency was 93.1 +/- 0.6 and 7.4 +/- 3.0% respectively, and when 27 ml of iron solution of 0.2 mg l(-1) was preconcentrated, the retention was 8.4 +/- 2.9%. The detection limits thus achieved is 12 mug l(-1) when 9 ml of sample are preconcentrated and 6 mug l(-1) for 27 ml.     

A rapid method for the determination of mercury in air by flameless atomic absorption spectrometry.

A rapid method for the determination of total gaseous mercury in the atmosphere is described. A simple, inexpensive sampling device is used; the collection time for mercury levels above 5 ng m^?3 is less than 25 min; less than 10 min is then needed to determine the mercury by flameless atomic absorption. For subnanogram levels longer sampling periods are used, but air polluted with mercury can be monitored in a few minutes. Data obtained for different samples are presented.     

A low consumption air-segmented sequential injection vapor generation system for the determination of mercury by atomic absorption spectrometry

A sequential injection system for the determination of mercury by vapor generation atomic absorption spectrometry (VGAAS) using tetrahydoborate reductant was developed, characterized by prevention of sample and reagent mixing in the holding coil using small air segments and initiation of the vapor generation in a flow-through gas-liquid separator. Extremely small volumes of reductant of 15-30 mul (0.2-1.0% NaBH(4)) and sample acidity as low as 0.05 mol l(-1) HCl were sufficient for achieving performance similar to flow injection (FI) VGAAS systems. A sample throughput of 90 h(-1) was achieved with 400 mul samples with a precision of 2.0% RSD at 10 mug l(-1)Hg, and a detection limit of 0.1 mug l(-1) (3sigma). Reagent consumption was reduced by a factor of 25 in comparison to the FI-VGAAS system. Good agreement with the certified value was obtained for the determination of mercury in seawater in a standard reference sample.     

Automatic flow system for the sequential determination of copper in serum and urine by flame atomic absorption spectrometry

In this work, a fully automated flow system exploiting the advantages of the association of multi-pumping, multicommutation, binary sampling and merging zones, to accomplish the sequential determination of copper in serum and urine by flame atomic absorption spectrometry, is described. The developed flow system allowed multiple tasks, such as serum samples preparation (samples and standard solutions viscosity adjustment), serum copper (SCu) measurement, urine copper (UCu) pre-concentration and its subsequent elution and measurement, to be carried out sequentially. The implemented flow manifold presented a modular configuration consisting on two quasi-independent modules, each one accountable for a specific sample manipulation and whose combined operation under computer control enabled the determination of copper in a wide concentrations range.Once optimised and with a sample consumption of about 0.250 mL of serum and 7 mL of urine, the developed flow system allowed linear calibration plots up to 5 mg L⁻¹ with a detection limit of 0.035 mg L⁻¹ for SCu and linear calibration plots up to 300 μg L⁻¹ with a detection limit of 0.67 μg L⁻¹ for UCu. The sampling rate varied according to the module employed and was about 360 determinations h⁻¹ (SCu module), 12 determinations h⁻¹ (UCu module) or 24 determinations h⁻¹ (12 urine and 12 serum samples; UCu and SCu modules simultaneously). Repeatability studies (R.S.D.%, n = 10) showed good precision for UCu at concentrations of 25 μg L⁻¹ (2.54%), 50 μg L⁻¹ (0.90%) and 100 μg L⁻¹ (1.62%) as well as for SCu at concentrations of 0.25 mg L⁻¹ (8.11%), 1 mg L⁻¹ (3.11%) and 5 mg L⁻¹ (0.90%). A comparative evaluation showed a good agreement between the results obtained in the analysis of UCu and SCu (n = 18) by both the developed methodology and the reference procedures. Accuracy was further evaluated by means of the analysis of reference samples (Seronorm™ Trace Elements Urine and Seronorm™ Trace Elements Serum) and the obtained results complied with the certified values.     

A rapid and simple method for the determination of trace metals in hair samples by atomic absorption spectrometry

Acid digestion procedures are described for the dissolution of human head hair in routine determinations of cadmium, chromium, mercury, lead and zinc in the same sample solution by means of atomic absorption spectrometry. The techniques employed are atomization in a Massman graphite furnace or in an air—acetylene flame; the cold-vapor cell is used for mercury. The entire analytical procedure is tested with powdered homogenized head hair samples, previously analyzed by other analytical techniques. Comparison of the results demonstrates that the proposed technique is at least as precise and accurate as the other procedures used.     

间接原子吸收法测定硫酸庆大霉素

建立了在镍离子存在下测定硫酸庆大霉素的间接原子吸收法。硫酸庆大霉素与二硫化碳反应,生成不溶于碱液的二烷基二硫代氨基甲酸镍沉淀,离心分离后以AAS法测定沉淀中镍的量来间接确定硫酸庆大霉素的含量,已用于实际样品测定。     

Validated method for the determination of carboplatin in biological fluids by Zeeman atomic absorption spectrometry

We have developed and validated a rapid, simple and sensitive analytical method, based on Zeeman atomic absorption spectrometry, for the quantitative analysis of carboplatin in human plasma, plasma-ultrafiltrate (UF), saliva and urine. The sample pretreatment is simple and only involves dilution of the samples with a solution containing 0.15 mol/L NaCl and 0.2 mol/L HCl in water (diluent). The caroplatin concentrations in the different biological matrices could be quantified using a standard curve constructed in plasma UF: diluent (1:10; v/v). The validated range of determination was 0.24 to 242 mol/L of carboplatin in plasma UF, 0.84 to 242 mol/L in plasma, 0.12 to 3.64 mol/L in saliva, and 2.02 mol/L to 12.1 mmol/L in urine. Matrix-effects were not observed. The stability of carboplatin (determined as Pt) in biological samples stored at –20°C was checked for a period of 8 months; no losses occurred during this period. The performance of the method, in terms of accuracy and precision, fitted well within the generally accepted criteria for validation of analytical methodologies. The proposed method was utilized in a pharmacokinetic study in one patient to demonstrate the usefulness of the assay.     

Pre-concentration procedure for determination of copper and zinc in food samples by sequential multi-element flame atomic absorption spectrometry

In this paper is proposed a simultaneous pre-concentration procedure using cloud point extraction for the determination of copper and zinc in food samples employing sequential multi-element flame atomic absorption spectrometry (FS-FAAS). The reagent used is 1-(2-pyridylazo)-2-naphthol (PAN) and the micellar phase is obtained using the non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114) and centrifugation. The optimization step was performed using Box-Behnken design for three factors: solution pH, reagent concentration and buffer concentration. A multiple response function was established in order to get an experimental condition for simultaneous extraction of copper and zinc. Under the optimized experimental conditions, the method allows the determination of copper with a limit of detection (3sigma(b)/S, LOD) of 0.1 microg L(-1), precision expressed as relative standard deviation (R.S.D.) of 2.1 and 1.3% (N=10), for copper concentrations of 10 and 50 microg L(-1), respectively. Zinc is determined with a LOD of 0.15 microg L(-1) and precision as R.S.D. of 2.7 and 1.7% for concentrations of 10 and 50 microg L(-1), respectively. The enhancement factors obtained were 36 and 32 for copper and zinc, respectively. The accuracy was assessed by analysis of certified reference materials, namely, SRM 1567a - Wheat Flour and SRM 8433 - Corn Bran from National Institute of Standards & Technology and BCR 189-wholemeal flour from Institute of Reference Materials and Measurements. The method was applied to the determination of copper and zinc in oats, powdered chocolate, corn flour and wheat flour samples. The copper content in the samples analyzed varied from 1.14 to 3.28 microg g(-1) and zinc from 8.7 to 22.9 microg g(-1).     

Determination of aluminium in silicon by electrothermal atomic absorption spectrometry

The sample is decomposed with hydrofluoric and nitric acids and the diluted solution is injected into the graphite furnace. For a 100-mg sample, the detection limit (3 σ) is 1.2 μg AI g^-1. The coefficient of variation is 3–13% for 9–7000 μg Al g^-1 in silicon.     

Indirect determination of perchlorate by atomic absorption spectrometry

A liquid-liquid extraction and determination of perchlorate by atomic absorption spectrometry is described. The method involves extraction of perchlorate with the Schiffs base complex [Co(BPTC)₂]⁺, where BPTC = 2-benzoyl pyridine thiosemicarbazone, in methyl isobutyl ketone in acidic medium and subsequent analysis of cobalt in flame AAS, hence indirectly for perchlorate. The extraction efficiency is 98%. The calibration graph was found to be linear for 1.0–11.4 g ClO ₄ ^– per ml of solvent, and the limit of detection is 30 ng ml^–1. The present method is free from interference of large number of foreign ions. The method has been applied for determination of perchlorate in human blood serum samples spiked with perchlorate, urine and commercial potassium chlorate sample.     

Fusion with boron trioxide for silicate analysis by atomic absorption spectrometry: determination of potassium

A boron trioxide-lithium carbonate (10 : 1) fusion is proposed for silicate analysis by atomic absorption spectrometry. The fusion melt is detached from the platinum crucible by the action of ultrasonic waves and dissolved in dilute hydrochloric acid containing hydrogen peroxide. The method was applied to the determination of potassium in standard silicate samples. No matrix effects were observed and the results obtained show very good accuracy and reproducibility.