Determination of oxygen in bismuthate single crystals

An improved procedure for determining oxygen in single crystals was developed. The procedure was tested on samples prepared from stoichiometric BaBiO₃ by thermal treatment in a controlled medium. The error of the procedure is about 0.5 mol%.     

A solid phase extraction procedure for the simultaneous determination of total inorganic arsenic and trace metals in seawater: Sample preparation for total-reflection X-ray fluorescence

In this paper we present a procedure allowing total-reflection X-ray fluorescence spectrometry (TXRF) determinations of arsenic in water samples, especially in seawater samples. The procedure consists of an arsenate reduction step (performed by using a l-cysteine solution) followed by a complexation of As⁺³ with sodium dibenzyldithiocarbamate and solid phase extraction. The new procedure is a modification of a method developed by Prange and allows a simultaneous determination of As together with V, Fe, Ni, Cu, Zn, Pb, and U in seawater by TXRF. The procedure was tested using the Certified Reference Material CASS-4 and was later applied to regular seawater samples collected from the North Sea. The detection limit for arsenic is 10 ng L^− 1.     

Determination of Chloroacetic Acids in Drinking Water by Reaction Gas Chromatography

A procedure was developed for determining chloroacetic acids in drinking water. The procedure is based on solid-phase extraction followed by the conversion of chloroacetic acids to trifluoroacetic esters and their separation and determination by gas–liquid chromatography with an electron capture detector. Esterification conditions were optimized. The procedure was used for analyzing samples of drinking water.     

Supramolecular microextraction of cobalt from water samples before its microsampling flame atomic absorption spectrometric detection

The supramolecular solvent system consists of tetrahydrofuran (THF) and 1-decanol, that was used as an extraction solvent for a microextraction procedure for the preconcentration and separation of Co(II). The proposed supramolecular-based procedure was combined with microsampling flame atomic absorption spectrometry for the determination of cobalt at trace levels in water samples. N-Benzoyl-N,N-diisobutylthiourea was used to chelate Co(II) in an aqueous solution. Quantitative extraction efficiency was obtained at pH 6.5. The effects of analytical parameters including pH, amount of ligand, type, ratio and volume of supramolecular solvent, sample volume and interfering ions were investigated for optimisation of the procedure. The proposed supramolecular solvent-based microextraction procedure (Ss-ME) exhibits a limit of detection (LOD) of 1.29 µg L^?1 and a limit of quantification (LOQ) of 3.88 µg L^?1. The procedure was validated by addition/recovery tests and by applying TMDA 64.2 and TMDA 53.3 water certified reference materials. The microextraction method was successfully applied for the preconcentration and determination of cobalt in water samples.     

Modification of catalytic adsorptive stripping voltammetric method of hexavalent chromium determination in the presence of DTPA and nitrate

The voltammetric procedure for determination of traces of Cr(VI) [Anal. Chim. Acta (1992) 262:103] was modified by changing the temperature of the measurements. It was found that at the temperature of 40 °C the time of decrease of the Cr(III) signal was shortened from 30 to 5 min. As a result the total analysis time was drastically shortened. The modified procedure does not show any disadvantage as compared to the original method. The results of Cr(VI) determination by the modified procedure are less affected by Cr(III) as compared to the original method. The detection limit of the method was 2.5 × 10^-11 mol L^-1 (1.2 ng L^-1). The validation of the modified procedure was performed by comparison of the results of analyses of tap and river water samples with those obtained using original procedure.     

Simultaneous Voltammetric Determination of Nitrites and Nitrates in Waters

A rapid procedure was developed for the simultaneous voltammetric determination of nitrites and nitrates from a single sample of potable, mineral, or underground water. Nitrites were first determined upon the anodic polarization of a graphite electrode in a sodium sulfate supporting electrolyte. Next, ascorbic acid and a copper salt were added, and the solution was acidified to an optimum pH value. A copper electrode was formedin situ, and the nitrate signal was recorded as the first derivative using cathodic sweep. The procedure does not require sample preparation or oxygen removal from the solution with a nitrogen flow. The copper–graphite electrode was regenerated electrochemically in the same solution. The analytical range for nitrite ions was 0.2–10.0 mg/L in the presence of any amount of nitrates. Nitrates were quantitatively determined in the range 0.5–5 mg/L. Common cations and anions in waters did not interfere with the determination. The procedure is suitable for the analysis of potable, mineral, underground, and surface waters. The procedure was verified by the added–found method and by the photometric procedure GOST (State Standard) 18826-73.     

An Improved Method for the Determination of Molybdenum in Plants,Soils, and Rocks

Abstract

Improvements to the thiocyanate colorimetric procedure for analysis of ppm levels of molybdenum have been made. The complete procedure was studied and revisions made to the solvent extraction system to increase sensitivity. The solvent itself was stabilized by elution through an adsorption column. Revisions to the fusion procedure were made to eliminate hand fusion of samples. The use of desiceants for solvent drying was replaced by filtration before absorbance readings to eliminate turbidity. Total solution of rock samples requires a special digestion procedure with atomic absorption finish.     

Rapid Non-Enzymatic DNA Deproteinization in Agarose Miniplugs

Abstract

Mini agarose plugs, containing immobilized cells, were lysed and deproteinized in 3–6 h by a non-enzymatic procedure, using 4 M urea and detergents. The performance of Saccharomyces cerevisiae miniCHEF DNA pattern was not affected by the treatment. DNA contained in the miniplugs was completely digested by restriction endonucleases in 1–2 h. This procedure saves time in comparison to the 40 h of incubation with urea used in the original procedure. It also saves reagents and permits a rapid DNA digestion without using PMSF.     

Isolation of radioactive strontium from natural samples: A semi-automatic procedure

A procedure for semi-automatic isolation and determination of radioactive strontium from natural samples was developed. The method was tested by the determination of⁹⁰Sr in soil samples and the results obtained were compared to those obtained by the standard procedure. The procedure consists of leaching of strontium (and other cations as well) from soil samples with a water suspension of the cation exchanger Amberlite IR-20, the separation of strontium from other cations, e.g., potassium, calcium, sodium, barium by the anion exchangers Amberlite CG-400 or Dowex Ag 1×8 with 0.25M HNO₃ in ethanol-methanol mixture as eluent in the apparatus specially constructed for this purpose. Determination of⁹⁰Sr was done on the low-level gas-flow β-counter and by Cherenkow counting on the liquid-scintillation counter few hours after the separation. It was shown that this procedure might be successfully applied for rapid determination of⁹⁰Sr in soil samples and other natural samples in a timesaving manner.     

Quantitation of R-836, a New Oral Bronchodilator,by High Performance Liquid Chromatography using Manual or Robotic Sample Preparation

Abstract

A simple and selective high performance liquid chromatography (HPLC) method has been developed for the quantitation of R-836 (an investigational oral bronchodilator) in human plasma and urine, dog plasma and urine, and rat plasma. The method consists of reversed-phase HPLC with ultraviolet detection. Sample preparation involved a one-step protein precipitation procedure and was performed both manually and by a Zymate robotic system. Precision and accuracy results showed excellent reproducibility; results using the robotic procedure were slightly better than the manual procedure. The robotic procedure was capable of preparing the samples with minimal operator handling.     

Determination of selenium in soil by hydride generation AAS

Hydride generation AAS was applied for the determination of total selenium in soil. The influence of various anions and cations present in the sample solution on the generation of selenium hydride was investigated. Special attention was paid to the wet oxidation procedure for the sample dissolution. The proposed procedure involves microwave sample preparation by using a mixture of H₂O₂/HNO₃/H₂SO₄. The accuracy of the procedure was checked by the analysis of the standard reference material Buffalo River Sediment (SRM-2704, NIST). Satisfactory agreement of the results obtained with the values reported was achieved. The detection limit of the procedure was 25 ng Se/g of soil. The relative standard deviation of the measurements varied from 5.5% for SRM-2704 up to 10% for the real soil samples. Received: 20 January 1997 / Revised: 24 February 1997 / Accepted: 1 March 1997     

The Determination of Methenamine and its Salts in Tablet Dosage Forms Using Ion-Pair Extraction

Abstract

This paper reports a simple, accurate, reproducible, stability-indicating procedure which may be used to quantitatively determine methenamine base, methenamine mandelate or methenamine hippurate in tablet dosage forms. The procedure initially involves the separation of methenamine from the dosage form and from formaldehyde, the decomposition product, by a cartridge ion-pair extraction process. The methenamine may then be assayed by a number of methods. In this paper the methenamine was hydrolyzed to formaldehyde and the formaldehyde determined by the Nash procedure. The method compares favorably with the USP XXI procedure for methenamine tablets. Advantages of the procedure include the ability to use a single method for the base and salt forms of the drug and the potential application to stability and quality control studies of methenamine dosage forms.     

Determination of Iridium at Sub ng·g−1 Levels in Geological Materials by RNAA

Radiochemical neutron activation method is presented for the determination of iridium in geological materials. The procedure consisted of thermal neutron irradiation of an 500 mg sample followed by sinterization with sodium peroxide, precipitation with tellurium and high resolution gamma-spectrometry with a hyper-pure Ge-detector. The procedure was evaluated by the analysis of the certified reference materials SARM-7 and W-1. The detection limit for the analytical conditions employed was 0.004 ng·g^–1 Ir. The procedure was applied to the reference materials TDB-1 and WGB-1, which present provisional values for Ir concentration, and GXR-3, GXR-5 and GXR-6, which do not present any reported data for Ir contents.     

Radiochemical procedure for the determination of plutonium isotopes in powdered milk

Summary A radiochemical procedure for the determination of alpha-emitting isotopes of plutonium in powdered milk is proposed. The procedure involves sample dissolution (by HNO₃ and HClO₄), separation by ionic-exchange resin, electrodeposition and alpha-spectroscopy. In order to determine the chemical recovery, ²⁴²Pu was employed as a tracer. A reference material (Marine Sediment IAEA 135) was analyzed to validate such procedure, and to show its reliability. Afterwards, some powdered milk, produced for international trade, was analyzed and chemical recovery was found to be around 95%.     

Supramolecular Solvent-Based Microextraction of Selected Anticonvulsant and Nonsteroidal Anti-Inflammatory Drugs from Sediment Samples

The increase in the production and consumption of pharmaceuticals increases their presence in the global environment, which may result in direct threats to living organisms. For this reason, there is a need for new methods to analyze drugs in environmental samples. Here, a new procedure for separating and determining selected drugs (diclofenac, ibuprofen, and carbamazepine) from bottom sediment and water samples was developed. Drugs were determined by ultra-high performance liquid chromatography coupled with an ultraviolet detector (UHPLC-UV). In this work, a universal and single-step sample treatment, based on supramolecular solvents (SUPRAS), was proposed to isolate selected anticonvulsants and nonsteroidal anti-inflammatory drugs (NSAIDs) from sediment samples. The following parameters were experimentally selected: composition of the supramolecular solvent (composition THF:H₂O (v/v), amount of decanoic acid), volume of extractant, sample mass, extraction time, centrifugation time, and centrifugation speed. Finally, the developed procedure was validated. A Speedisk procedure was also developed to extract selected drugs from water samples. The recovery of analytes using the SUPRAS procedure was in the range of 88.8–115%, while the recoveries of the Speedisk solid-phase extraction procedure ranged from 81.0–106%. The effectiveness of the sorption of the tested drugs by sediment was also examined.     

High Performance Liquid Chromatographic Assay of Hydromorphone Hydrochloride Injection

Abstract

A stability indicating high performance liquid chromatographic (HPLC) method for determining hydromorphone hydrochloride in dosage forms is described. The drug was chromatographed on a C₁₈ reverse phase column, using a mobile phase consisting of sodium lauryl sulfate, acetic acid, acetonitrile and water, and detected at 280 nm. Linearity of detector response to the concentration was confirmed. The procedure showed excellent reproducibility and gave quantitative recoveries of the drug from spiked placebos. Photodegraded samples of the dosage form, were assayed by the HPLC procedure and the current USP spectrophotometric procedure. Comparison of the results showed that the USP procedure is only partially stability indicating.     

Determination of antimony and tin in tin dioxide whiskers by inductively coupled plasma mass spectrometry

A procedure for the determination of antimony and tin in tin dioxide whiskers, which were grown from a gas phase by the vapor-liquid-solid mechanism, was developed. The problem was difficult because the single whiskers are irregularly small in size and have a small weight (about 10^?5 g). The procedure is based on the decomposition of a solid sample by cementation on zinc followed by the determination of analytes with the use of inductively coupled plasma mass spectrometry. The procedure developed is characterized by the detection limits of antimony of 0.01–0.03 μg/L and an RSD of 10%. An approach was proposed to estimate the antimony content of single whiskers.     

Multivariate optimization of a microwave-assisted leaching procedure using dilute acid solutions,for FAAS determination of Cu,Fe, Mn,and Zn in multivitamin/multimineral supplements

This paper reports the development of a microwave-assisted procedure for leaching of copper, iron, manganese, and zinc from multivitamin/multimineral supplements by use of dilute acid before determination by flame atomic absorption spectrometry (FAAS). A Doehlert design was used to find optimum conditions for the procedure by use of response-surface methodology. Three variables (acid concentration in the leaching solution, irradiation time, and irradiation power) were used as factors in the optimization study for two acids, HCl and HNO₃. Final working conditions were established as a compromise between the optimum values for each analyte, taking into consideration the robustness of the procedure. The best leaching results were obtained with HNO₃ and the acid concentration, irradiation time, and irradiation power used were 0.70 mol L⁻¹, 15 min and 360 W, respectively. The accuracy of the optimized procedure was evaluated by comparison with a well-established closed-vessel microwave dissolution technique.     

Extraction Preconcentration of Uranium and Thorium Traces in the Analysis of Bottom Sediments by Inductively Coupled Plasma Mass Spectrometry

A procedure was developed for determining trace amounts of uranium and thorium isotopes in bottom sediments from Lake Baikal. This procedure involves sample decomposition, the coextraction of uranium and thorium with trioctylphosphine oxide, the quantitative back extraction after diluting the extract with caprylic acid, and the ICP MS analysis of the back extract. The procedure was verified by analyzing a BIL-1 Lake Baikal bottom silt standard reference material using the developed procedure and independent methods. The detection limits of abundant uranium and thorium isotopes are restricted by blank measures and equal to 1 × 10^–7 mass %. The detection limits for²³⁴U and ²³⁰Th are 4 × 10^–10 and 6 × 10^–10 mass %, respectively.     

A rapid and simple microwave-assisted digestion procedure for spectrophotometric determination of titanium dioxide photocatalyst on activated carbon

Deposition of titanium dioxide (TiO₂) on activated carbon (AC) surface has been widely utilized for the production of TiO₂/AC photocatalyst, which can be used in photo-degradation of pollutants. In this work, a fast and simple digestion procedure has been developed for the spectrophotometric quantitative analysis of TiO₂ in TiO₂/AC photocatalyst. Microwave-assisted digestion was used in the procedure. The microwave-digestion procedure was optimized using the single-variable method. Variables optimized included time of ashing, effective digestion time, volume and concentration of sulfuric acid, effect of adding a digestion catalyst, effect of sample pulverizing and on–off time cycle of the microwave. The analysis was completed spectrophotometrically after addition of hydrogen peroxide to the digested solution. Procedure precision and accuracy was tested by application to photocatalyst samples containing known amounts of TiO₂, and compared with previously published spectrophotometric procedures. The proposed microwave procedure was capable of recovering 98.4–101.1% of TiO₂ in the catalyst in less than 10 min, without the need for sample ashing. Analytical precision is 1.42–2.39% relative standard deviation (R.S.D.). In terms of accuracy and precision, the proposed microwave procedure was comparable with other procedures, but the proposed microwave procedure was superior in terms of shorter procedure duration.