Determination of Gold in Biological Materials by Atomic Absorption Spectroscopy

Abstract

A method for the determination of gold in biological materials such as serum, urine, synovial fluid and tissues was investigated. After the dry ashing of the samples, gold was extracted from 6 M HCL into MIBK. The amount of gold was determined directly in the organic phase by the atomic absorption spectrometry. The range of the working curve was from 0.1 to 5.0 μg and the accuracy and recovery of the present method were satisfactory for practical purposes.     

Extraction and Flameless AAS Determination of Germanium in Lignite Fly Ash

Abstract

The use of dicyclohexyl-18-crown-6 methyl isobutyl ketone solution in extraction and flamelessatomic absorption spectrophotometry (AAS) determination of germanium in lignite fly ashes have been studied.

Germanium is usually determined in lignites after the carbonaceous part of the sample has been burnt by a dry or wet ashing method. However, methods are described for direct determination of germanium.

In the present paper a wet ashing method is reported for the determination of germanium in lignite fly ashes by flameless AAS after extraction into dicyclohexyl-18-crown-6 methyl isobutyl ketone (MIBK) solution. Solvent extraction is a known hydrometallurgical method that could be applied in germanium recovery.     

Determination of Arsenic in Beverages and Foods by Hydride Generation Atomic Absorption Spectroscopy

Abstract

The determination of the arsenic content of foods and beverages by a technique involving a magnesium nitrate aided dry ashing step followed by an arsine generation atomic absorption finish is described. Recoveries of various arsenic species added prior to ashing was excellent. Total arsenic concentrations found in samples of beverages ranged from less than 10 to 265 ppb and in foods from 20 to 9290 ppb. The sensitivity of the technique is approximately ten-fold better than obtainable with commercially available hydride generation atomic absorption units.     

Determination of Total Sulfur in Soils and Plants by an Automated Dry Combustion Method

Abstract

Determination of total sulfur in environmental samples can be accomplished using automated dry combustion techniques. The analytical performance of an elemental analyzer (CE Instruments) was compared with a method involving dry ashing followed by ion chromatographic detection of sulfate (IC). Samples included certified reference materials, confirmation materials with a known content of sulfur, and several soils and plants. There was a close agreement between both methods. Superior accuracy, precision and detection limits were obtained using the dry combustion method. Current results suggest that the automated dry combustion technique has developed into an adequate method for the determination of the relatively low total sulfur contents commonly encountered in soils and plants.     

High-Performance Liquid Chromatographic Assay for Chlorquine and its Two Major Metabolites,Desethylchloroquine and Bidesethylchloroquine in Biological Fluids

Abstract

A high-performance liquid chromatography (HPLC) method for the determination of chloroquine and its two major metabolites in biological fluids is described. Hydroxychloroquine is used as an internal standard (I.S.). Drug, metabolites and I.S. were extracted as bases with diethyl ether by a single step procedure. After drying and evaporation of the organic phase, the residue was dissolved into the mobile phase and injected into the chromatographic system. Separation was performed using a normal phase column (Inertsil sill with mixture of acetonitrile, methanol and ammonia as mobile phase. The detection was carried out by fluorescence measurement : excitation wavelength was set at 325 nm and emission at 380 nm. The limit of detection was near 3.7 ng ml^?1 for chloroquine and metabolites. No chromatographic interference could be detected by endogenous compounds or other antimalarial drugs. Because of the good accuracy of the method, concentrations were determinated with a relative standard deviation lower than 7% at the 25 ng ml^?l level for all substances.

An excellent precision was obtained over the range of concentrations tested, 25–1000ng ml^?l. This method can be applied to therapeutic, pharmacokinetic and epidemial studies.     

Coprecipitative Preconcentration and Differential Pulse Cathodic Stripping Voltammetric Determination of Selenium (IV)

Abstract

A DPCSV procedure for the determination of selenium (IV) with a prior preconcentrative coprecipitation on iron (III) hydroxide has been developed. The experimental conditions for coprecipitation of selenium (IV) onto iron (III) hydroxide, viz. pH, iron (III) concentration, volume of aqueous phase and selenium concentration, were optimized. The coprecipitated selenium (IV) is dissolved in 10 ml of 0.1 M HCl and analysed using DPCSV in the presence of copper (II). Selenium concentrations as low as 10–100 ng present in 500 ml of the aqueous phase could be determined. The method is precise and has been applied to the analysis of sea water and reference material samples.     

Analysis of Biological Tissues for Selenium by Thin Layer Chromatography

Abstract

Selenium is oxidized by the method of Poole¹ as modified by Stahr, et al⁴ to free it from matrix encumbrances. It is reduced by HC1 dissolution and complexed with DAN (Diaminonapthalene) then extracted into cyclohexane and analyzed by TLC (reverse phase Whatman high performance plates) thin layer chromatography densitometry. TLC allows observation of 0.1 ng of the selenium (piazselenole) complex. Separation of the Se containing complex allows elimination of other potentially interfering fluorescent compounds. 100% recoveries of Se⁷⁵ (radiolabelled) are achieved through the digest step and 85–90% are achieved through the complete test. Radioautography shows only the gold piazselenole spot contains selenium. Agreement with Bureau of Standards results on freeze dried liver is 100% ± 2%.     

The Submicrodetermination of Oxygen in Organic Compounds by a Gas-Chromatographic Method

Abstract

Preliminary studies of a method for the determination of oxygen in 30–80 μ;g samples of organic compounds are described. Organic oxygen is converted to carbon monoxide by pyrolysis through platinized graphite wool and the monoxide is measured by thermal conductivity.     

Determination of total selenium in water by atomic-absorption spectrometry after hydride generation and preconcentration in a cold trap system

A cold trap system for the determination of selenium by hydride generation-atomic absorption spectrometry (HG-AAS) is described. For a 30-ml sample the limit of detection is <2 ng/l. and the precision is better than 4% at the 30 ng/l. level. A number of digestion procedures for the destruction of organic matter prior to the determination of total dissolved selenium in water has been tested and compared. Concordant results were obtained except for oxidation by peroxodisulphate in strongly acidic solutions with a high content of organic material. The selenium concentrations found were in agreement with those obtained by HG-AAS after preconcentration by evaporation and dry ashing with the magnesium nitrate-nitric acid-hydrochloric acid method.     

Spektrochemische Bestimmung von Gallium -, Indium-Und Thalliumspuren unter Benutzung der Extraktionssysteme mit Drei Flussicen Phasen

Abstract

A new method for concentrating of microgram amounts of elements before their spectral determination is described. The method is based on the diantipyrilethanes property to divide the organic solvent into two phases, i. e., during the extraction of elements the three liquid phase system is formed. In one of the phases (the “third phase”) 93–98% of the extractable elements are concentrated. Owing to the small volume the third phase may be dropped onto electrodes avoiding evaporating, ashing of extracts and filling of electrodes before spectral determination. This twice of three times reduces the duration of analysis and increases the accuracy and sensibility of determinations. Based on the three liquid phase system the spectrochemical method of the microgram amounts determination Ga, In and Tl(II1) in Mg, Be, Al, Sc, Y, La, Ce, Zn, Cd, Pb has been developed. The use of such systems in analytical chemistry would be perspective.     

Determination of Trace Amounts of Organic Pollutants in the Yellow River by Capillary Column Gas Chromatography-Mass Spectrometry

Abstract

The trace organic pollutants in the Yellow River enriched by a solvent extraction method were pre-separated into four different fractions of fatty hydrocarbons, polycyclic aromatic hydrocarbons, polar compounds and organic acids and were analyzed by the use of combined capillary column gas chromatography-mass spectrometry. Using the combined techniques of relative retention value, mass spectra and mass chromatogram, more than 60 organic pollutants were identified, among which 16 fatty hydrocarbons and 6 polycyclic aromatic hydrocarbons which were quantitatively analyzed. The concentration range of fatty hydrocarbon was 5–800 ng/l, and that of polycyclic aromatic hydrocarbon was 0-90ng/l.     

Sample Preparation Techniques—An Important Part in Trace Element Analysis for Environmental Research and Monitoring

Abstract

For the determination of minute amounts of elements in environmental samples combined analytical procedures are frequently employed. The combination of suitable sample preparation techniques with adequate detection methods lead to powerful analytical procedures. Decomposition methods are an important part of combined procedures for the determination of trace elements in solid samples. After a short summary of the potential sources for systematic errors two new decomposition methods are described that are suitable for the ashing of organic environmental samples. In one method the organic sample is ashed in a high-frequency excited oxygen plasma. The second method is a high pressure decomposition that permits mineralization of the sample in sealed quartz vessels with nitric acid at temperatures up to 320°C.

For both methods the ratio of sample weight to decomposition reagents is comparatively high. This makes these methods in combination with adequate detection methods suitable for the determination of elements at very low concentrations.

X-ray fluorescence spectrometry combined with adequate preconcentration methods is very well suited for the simultaneous determination of trace elements. Following a critical evaluation of various preconcentration techniques the analytical characteristics of filter paper with immobilized complexing agents are described. Particular emphasis is given to filter papers with dithiocarbamates as chelating group.     

Pervaporation as a Separation Technique for Direct Determination of Volatile Selenium Species by Atomic Fluorescence Spectrometry

Abstract

This paper reports for the first time a suitable way to determine methylated selenium compounds using the new approach of pervaporation coupled to atomic fluorescence spectrcmetry (PV-AFS).

The method developed allows direct extraction, separation, preconcentration and determination of dimethylselenium (DMSe) and dimethyldiselenium (DMDSe) from slurry samples. Under the optimum conditions, the detection limits (LODs) were found to be 0.66 ng and 0.39 ng for DMSe and DMDSe, respectively, the precision being about 6–9 % for 10 ng mL as selenium concentration. The linearity ranges were from the LOD to 0.7 μg mL^?1 for DMSe and from the LOD to 0.4 μg mL^?1 for DMDSe (as Se). The pervaporation efficiencies were 55 ± 1 % and 85 ± 5 % for DMSe and DMDSe, respectively. The proposed method was successfully applied to determine methylated selenium species in sewage sludge, garlic and oyster samples. The concentrations found were from 0.07 to 1.42 μg g^?1.

As no certified reference materials are available for these analytes, validation was carried out by recovery studies in these matrices, and the results showed that the proposed method performed satisfactorily.     

Daily Variations in Composition of Extractable Organic Compounds in Fly-Ash from Municipal Waste Incineration

Abstract

The daily variations of organic compounds on fly ash from municipal waste incinerator are reported. Variations in composition over a one week sampling period were 1 to 8 μg/g for estimated total organic compounds, 57 to 220ng/g for total polychlorinated dibenzo-p-dioxins, and 56 to 490ng/g for total polycyclic aromatic hydrocarbons.     

Simultaneous Determination of Salicylic Acid and Salicyluric Acid in Plasma and Urine by High Pressure Liquid Chromatography

Abstract

A sensitive, rapid, and specific high pressure liquid chromatographic (HPLC) assay was developed for the determination of salicylic (SA) and salicyluric (SU) acids in plasma and urine. The compounds are extracted into ethyl ether at acid pH, evaporated, and reconstituted prior to instrumental separation. Overall recovery of both compounds is 90 ± 5%, and the sensitivity limits are 150 ng of SU and 300 ng SA per ml of biological fluid. The assay was used for the determination of both compounds in plasma and urine of man following oral doses of 40 mg/kg of sodium salicylate.     

Rapid Determination of Bupropion in Human Plasma by High Performance Liquid Chromatography

Abstract

A high performance liquid chromatographic (HPLC) technique has been developed for the determination of bupropion hydrocloride (Bup) in human plasma, using a reversed-phase method, with UV detection at 250 nm.

The internal standard 5-(P-methylphenyl)-5-phenylhydantoin (MPPH), was used as an aid to quantitation. The plasma was deprotemized with acetonitrile and the clear supernatant was directly injected in the chromatographic system. The lower limit of quantitation was 5.0 ng/ml using only 100 μl of plasma sample.

Linear regression analysis for the calibration plots obtained on five different days over a two-week period for the the two ranges used (10–250 ng/ml and 250–2000 ng/ml) in plasma indicated excellent linearity and reproducibility. The mean recovery of spiked Bup in plasma samples over the concentrations studied was found 96.5 ± 3.14%.

The method revealed that more than 30% of Bup was lost when the supernatant was stored at room temperature for 24 hrs.     

Bestimmung von Arsen in biologischem Material mittels Atomabsorptionsspektralphotometrie

A modified determination of arsenic by means of AAS is described. AsH₃ generation is carried out in a reaction vessel by addition of NaBH₄. The gas evolved is swept into a nitrogen entrained air flame. The detection limit amounts to 10 ng of arsenic.In the dry ashing step used for biological materials Mg(NO₃)₂ is used as an ashing aid. It was found, that an excess of four times of Mg(NO₃)₂ is necessary for finding all arsenic present. An ashing temperature of 500° C is suitable. 2 h of ashing time is enough if the samples are carefully preashed. Various foods have been analysed, mainly all higher burdened species. Arsenic contents in drinking water and some detergents have also been investigated.     

Molecular emission cavity analysis: Part 22. Determination of selenium and tellurium by direct injection into the cavity

Selenium (>50 ng) as selenite or selenate, and tellurium (1–15 μg) as tellurate may be determined by measuring the intensities of the Se₂ and Te₂, emissions, in a carbon cavity situated in a hydrogen—air flame. Certain organic compounds (e.g., citric acid, ascorbic acid and glucose) enhance the intensities, especially of tellurium.     

The determination of organic and inorganic lead compounds in urban air by atomic-absorption spectrometry with electrothermal atomization

A method for the simultaneous determination of inorganic and organic lead compounds in air is described, together with some results from its application at different sampling sites. Air-borne particulate lead is collected on a cellulose filter. Organic lead vapours are trapped in an iodine monochloride solution, placed behind the filter. A fraction of the cellulose filter is subjected to low-temperature ashing, after which the lead content in the residue is measured by electrothermal atomic-absorption spectrometry. The organolead material absorbed in the iodine monochloride solution, is determined by solvent extraction and electrothermal atomic-absorption spectrometry. For a 6-h sampling period, detection limits of the order of 10 ng m^-3 for inorganic and 8 ng m^-3 for organic lead materials may be obtained.     

Determination of Fluoxetine in Human Plasma by Liquid Chromatography–Mass Spectrometry and Its Application

Abstract

A rapid, simple, and specific liquid chromatography–electrospray ionization–mass spectrometric method has been developed and validated for the determination of fluoxetine in human plasma. The method was validated with a linear range of 0.5–100 ng mL^?1, and the lowest limits of quantification were 0.5 ng mL^?1 for fluoxetine. The extraction efficiencies were about 65% and recoveries of method were in the range of 94.0–97.5%. The intraday relative standard deviation (RSD) was less than 11% and interday RSD was within 12%. The method has been successfully applied to the evaluation of pharmacokinetics and bioequivalence of fluoxetine.