Search results for "dilution"
showing 10 items of 242 documents
Determination of ruthenium in photographic emulsions - Development and comparison of different sample treatments and mass spectrometric methods
1999
Different sample treatment procedures were combined with inductively coupled plasma mass spectrometry (ICP-MS) and negative thermal ionisation mass spectrometry (NTI-MS) for the determination of ruthenium traces in photographic emulsions. Dissolution of the samples in concentrated ammonia solution was used in connection with ICP-MS by external calibration, which has the advantage of a simple sample preparation technique but introduces high amounts of the silver matrix into the mass spectrometer. On the other hand, isotope dilution mass spectrometry (IDMS) with an enriched 99Ru spike solution was applied for ICP-MS and NTI-MS measurements, respectively, in connection with a significant reduc…
Bromide/bromate speciation by NTI-IDMS and ICP-MS coupled with ion exchange chromatography
1997
Two different mass spectrometric methods, negative thermal ionization isotope dilution mass spectrometry (NTI-IDMS) and inductively coupled plasma mass spectrometry (ICP-MS), off-line and on-line coupled with anion exchange chromatography, have been developed for simultaneous bromide and bromate determinations in water samples. The detection limits of these methods are in the range of 0.03–0.09 μg/L using a 50 mL sample.The results are independent of the content of other anions, which could be demonstrated by the analyses of six mineral waters containing chloride and sulfate of up to 160 mg/L and 1500 mg/L, respectively. Bromide has been analyzed by the NTI-IDMS method in the range of 10–50…
Development of an ICP−IDMS Method for Dissolved Organic Carbon Determinations and Its Application to Chromatographic Fractions of Heavy Metal Complex…
1998
A sensitive and fast method for direct determinations of dissolved organic carbon (DOC) in bulk samples and in chromatographically separated fractions by inductively coupled plasma isotope dilution mass spectrometry (ICP−IDMS) is developed. A 13C-enriched spike solution of benzoic acid is used for the isotope dilution step. Equal ionization efficiencies are obtained for carbon, independent of the type and molecular weight of the dissolved organic substance, which is the most important precondition for DOC determinations by ICP−IDMS. The detection limits achieved are 0.3 mg L-1 for bulk analyses and 7 × 10-4 μg s-1 for transient signals of chromatographic peaks. The results for different wat…
Evaluation of a Real-Time PCR Assay for the Detection and Quantification of Group Spores in Food
2010
A procedure based on quantitative real-time PCR was evaluated for the detection and quantification of Bacillus cereus spores. Several methods for DNA isolation, such as various heat treatments and germination solutions, were evaluated on spore suspensions of representative strains of the B. cereus group. Overall, the commercially available DNeasy tissue kit yielded the maximum amount of DNA. The procedure also was used to construct calibration curves for different food matrices, with a wide spore quantification range of 5 log units using serial dilutions of spore suspensions of B. cereus CECT 148T. The detection limit for B. cereus in artificially contaminated liquid egg and reconstituted i…
Direct derivative spectrophotometric determination of carbaryl and carbofuran in water samples
1990
Abstract Derivative absorption spectrophotometry has been applied to the direct determination of carbaryl and carbofuran in water samples. The use of the third derivative for carbaryl and the fourth derivative for carbofuran reduces the matrix effect and the seventh derivative provides, in both cases, accurate results for the determination of these pesticides, even working at low dilution levels of the samples. A limit of detection of 4 ppb and a variation coefficient of 0.1% have been obtained for the determination of carbaryl. Carbofuran can be determined with a limit of detection of 5 ppb and a variation coefficient of 0.02%.
Determination of organophosphorus pesticides in honeybees after solid-phase microextraction.
2001
A method based on solid-phase microextraction (SPME) followed by gas chromatography with nitrogen-phosphorus detection was developed for the purpose of determining 18 organophosphorus pesticide residues in honeybee samples (Apis mellifera). The extraction capacities of polyacrylate and poly(dimethylsiloxane) fibers were compared. The main factors affecting the SPME process, such as the absorption time profile, salt, and temperature, were optimized. The method involved honeybee sample homogenization, elution with an acetone:water solution (1:1) and dilution in water prior to fiber extraction. Moreover, the matrix effect on the extraction was evaluated. In samples spiked at the 0.2 mg kg(-1) …
Development of an ICP-IDMS method for accurate routine analyses of toxic heavy metals in polyolefins and comparison with results by TI-IDMS
2000
An inductively coupled plasma isotope dilution mass spectrometric (ICP-IDMS) method was developed as a suitable method - with respect to its sensitivity, precision, accuracy, and time-consumption - for the analysis of toxic heavy metal traces (Pb, Cd, Cr, and Hg) in polyolefins. Results for Pb, Cd, and Cr were compared with those obtained by thermal ionization isotope dilution mass spectrometry (TI-IDMS), which was used as a reference method. Because of its high first ionization potential and its high volatility mercury could not be determined by TI-IDMS. A multi-element spike solution, containing isotopically enriched 206Pb, 116Cd, 53Cr, and 201Hg, was used for the isotope dilution step. D…
Multi-element trace determinations in pure alkaline earth fluoride powders by high-resolution ICP-MS using wet-chemical sample preparation and laser …
2003
Four alternative analytical procedures for the determination of ten important trace impurities (Mg, Cr, Fe, Cu, Zn, Sr, Zr, Cd, Ba, and Pb) in pure alkaline earth fluoride powders were applied using high-resolution inductively coupled plasma mass spectrometry (ICP-MS). Two procedures are based on a wet-chemical microwave digestion with boric acid and quantification by the standard addition technique and isotope dilution mass spectrometry (IDMS), respectively. In addition, analyses are also performed by laser ablation as a direct solid sampling technique applying matrix-matched external calibration as well as isotope dilution of the powdered sample. For most elements good agreement between t…
Development of an isotope dilution laser ablation ICP-MS method for multi-element determination in crude and fuel oil samples
2009
An inductively coupled plasma isotope dilution mass spectrometric (ICP-IDMS) method with direct introduction of the isotope-diluted sample into the plasma by laser ablation was developed for accurate, sensitive, fast, and simultaneous determination of trace metals in different oil samples. Metallo-organic solutions of isotope spikes (50V, 53Cr, 65Cu, 57Fe, 62Ni, 68Zn, 113Cd, 117Sn, and 206Pb) were prepared from corresponding aqueous stock solutions by using liquid–liquid extraction of complexed metal ions in isobutyl methyl ketone. The isotope-diluted sample was absorbed by a cellulose material, which was fixed in a special PTFE holder for ablation, using a laser system with high ablation r…
Determination of mercury in rice by cold vapor atomic fluorescence spectrometry after microwave-assisted digestion.
2010
Abstract A cold vapor atomic fluorescence spectrometry method (CV-AFS) has been developed for the determination of Hg in rice samples at a few ng g−1 concentration level. The method is based on the previous digestion of samples in a microwave oven with HNO3 and H2O2 followed by dilution with water containing KBr/KBrO3 and hydroxylamine and reduction with SnCl2 in HCl using external calibration. The matrix interferences and the effect of nitrogen oxide vapors have been evaluated and the method validated using a certified reference material. The limit of detection of the method was 0.9 ng g−1 with a recovery percentage of 95 ± 4% at an added concentration of 5 ng g−1. The concentration level …