Showing papers on "Detection limit published in 1981"
TL;DR: In this article, a technique for the determination of "inorganic" arsenic(III), "methylarsenic" and "dimethylarsenic", species is described which is based on the trapping of arsines and selective volatilisation into a heated quartz atomiser tube situated in the optical path of an atomic-absorption spectrometer.
Abstract: A technique for the determination of “inorganic” arsenic(III) and arsenic(V), “methylarsenic” and “dimethylarsenic” species is described which is based on the trapping of arsines and selective volatilisation into a heated quartz atomiser tube situated in the optical path of an atomic-absorption spectrometer. Improved reproducibility is obtained by the use of a continuous flow reduction stage and detection limits are approximately 0.25 ng (based on twice the standard deviation of 10 blank measurements). For a typical sample volume of 10 ml this corresponds to a detection limit of 0.025 ng ml–1 of arsenic. Interferences were investigated and depression of results was observed in the presence of silver(I), gold(III), chromium(VI), iron(II), iron(III), germanium(IV), molybdenum(VI), antimony(III), antimony(V), tin(II), manganese(VII) and nitrite. Various approaches to overcoming such interferences were investigated, and for general use masking with EDTA is advocated. The choice of extraction procedures for speciation analysis is discussed.
112 citations
TL;DR: Norepinephrine and dopamine in human urine were determined by the use of the new high-performance liquid chromatography detection system with the coefficient of variation of less than 4.0%.
108 citations
TL;DR: In this paper, a trace speciation of a broad range of organotins, representing current industrial or environmental interests, was performed by combination of an tin-specific graphite furnace atomic detector with HPLC employing reverse bonded-phase strong cations exchange columns.
Abstract: : Based on their behavior as stable cations in saline solutions, direct trace speciation of a broad range of organotins, representing current industrial or environmental interests, was performed by combination of an tin-specific graphite furnace atomic detector with HPLC employing reverse bonded-phase strong cations exchange columns. Column and system performance and detection limits (5-30 ng as tin) vary predictably with individual substituents on organotins, but are easily optimized, for example, for identifying marine antifoulant leachates. (Author)
98 citations
TL;DR: A very sensitive and specific method of 2-ketoacid determination in various biological fluids using gas chromatography chemical ionization mass spectrometry of O-trimethylsilyl-quinoxalinol derivatives is described, which has been applied successfully to various metabolic disorders characterized by an accumulation of aliphatic 2- ketoacids.
Abstract: A very sensitive and specific method of 2-ketoacid determination in various biological fluids using gas chromatography chemical ionization mass spectrometry of O-trimethylsilyl-quinoxalinol derivatives is described. After derivatization with o-phenylenediamine in acidic medium and extraction, the 2-ketoacids, and the 2-ketovaleric acid used as internal standard, are silylated and resolved on a capillary column and their concentrations automatically determined by monitoring the m/z values corresponding to their respective protonated molecular ions, using ammonia as reactant gas. The detection limit is below 50 ng ml-1 of each 2-ketoacid. The recoveries of 2-ketoacids from urine and plasma were between 97 and 104%. Problems encountered with interfering substances were tested for and discussed. This method has been applied successfully to various metabolic disorders characterized by an accumulation of aliphatic 2-ketoacids. The metabolic interrelationship of branched chain 2-ketoacids and other compounds, especially pyruvate, is discussed.
90 citations
TL;DR: A sensitive, reliable, and economical method for the determination of 6 mycotoxins in mixed feeds is described and has been applied to a wide range of mixed feeds, including laboratory animal diets, and raw materials.
Abstract: A sensitive, reliable, and economical method for the determination of 6 mycotoxins in mixed feeds is described. The feed is extracted with chloroform-water and the extract is cleaned up by using a disposable Sep-Pak silica cartridge. The procedure requires less time (15 min from sample extraction to extract preparation) and less solvent (approximately one-tenth) compared with conventional methods and is suitable for a fast, economical screen. Additional cleanup procedures, involving dialysis or extraction into base, are described for samples containing high levels of interfering compounds. Thin layer chromatography (TLC) and high performance liquid chromatography (HPLC) with fluorescence detection are described for identification and estimation of mycotoxins. The method has been applied to a wide range of mixed feeds, including laboratory animal diets, and raw materials. The limit of detection is 1 microgram/kg for all mycotoxins measured by HPLC.
89 citations
TL;DR: In the plasma of patients treated with fentanyl two metabolites could be detected and identified using GC-AFID and GC-MS, and the concentration of fentanyl in patients ranged from 40 to 3 ng/ml of plasma in the first hour after administration.
72 citations
TL;DR: One advantage of the present method is that interfering compounds occurring in previously employed chromatographic methods are eliminated and the number of transfers is reduced thereby reducing errors associated with losses or contamination.
72 citations
TL;DR: Preliminary results of a pharmacokinetic study show that the sensitivity and selectivity of the assay are adequate for drug monitoring in clinical practice and the results obtained from multiwavelength detection suggest the existence of metabolites.
62 citations
TL;DR: In this article, the chemiluminescence effect was found during oxidation of disulfitomercurate complex in aqueous solutions with KMnO4 under acid conditions.
Abstract: A chemiluminescence effect was found during oxidation of disulfitomercurate complex in aqueous solutions with KMnO4 under acid conditions. By employing a filter technique for air sampling the chemiluminescence method is applied to the detection of atmospheric sulfur dioxide. The quality of the complete procedure is demonstrated by comparative calibrations from the liquid and gas phase and comparative measurements with several other SO2 sensitive methods. The detection limit is shown to be (10±1) pptv SO2. Some measurements of atmospheric SO2 background concentrations are shown in order to demonstrate the potential of the whole procedure in its application to atmospheric SO2 measurements.
62 citations
TL;DR: A method is described for the determination of aluminium in serum by atomic absorption spectroscopy with a graphite furnace and a good correlation between the two methods was found.
60 citations
TL;DR: The sensitivity and detection limit for measurements of the concentration of cadmium in the kidney cortex of man in vivo have been investigated using the technique of X-ray fluorescence.
Abstract: The sensitivity and detection limit for measurements of the concentration of cadmium in the kidney cortex of man in vivo have been investigated using the technique of X-ray fluorescence. An 11 GB1 241Am source was used to generate the characteristic K alpha X-rays of cadmium. The variation in the sensitivity for the detection of cadmium at various locations in a kidney has been studied. Because of the pronounced variation in sensitivity with depth in tissue, a measurement could be made selectively in the kidney cortex. The minimum detectable Cd concentration varies between 20 and 40 micrograms g-1 for distances between the skin and the kidney surface of 30 to 40 mm; this distance has a measured uncertainty of +/- 3 mm which gives rise to an uncertainty of +/- 30% in the estimated Cd concentration. The mean absorbed dose to the kidney during such a measurement is about 0.6 mGy. The X-ray fluorescence method is more advantageous than the alternative neutron capture gamma ray analysis technique as far as the total irradiation of the patient is concerned. The cadmium concentrations in the kidneys of five exposed persons were found to lie between 30 and 143 micrograms g-1.
TL;DR: A high-performance liquid chromatographic method based on separation on a cation-exchange resin followed by an amperometric detection of the SH group of D-penicillamine oxidized on a gold electrode has been developed.
TL;DR: Good linearity is observed over a two- to three-order concentration range and the method has been applied to the determination of ethylene thiourea in e.g. wash-water of apples and tomatoes, and to the detection of penicillamine in spiked serum and urine.
TL;DR: From experiments with a computer-controlled polychromator with background measurement facilities, it is concluded that the accuracy is improved if background measurements are made at wavelengths near the analytical lines, for each sample independently.
TL;DR: In this paper, the first-order reaction rate constants for VFA were determined by anaerobically incubating samples at in-situ temperatures with tracer levels of 14 C-labeled VFAs.
TL;DR: In this article, a detection limit of 1 ng ml-1 for lead is obtained by the reported method, where samples are prepared in 0.5 M hydrochloric acid, 0.8 M hydrogen peroxide, and 5% sodium tetrahydroborate.
TL;DR: Two sensitive and selective quantitative methods for 6-oxo-PGF1 alpha, the stable hydrolysis product of prostacyclin are described and compared and both offer sensitivity, selectivity and reproducibility.
Abstract: Two sensitive and selective quantitative methods for 6-oxo-PGF1 alpha, the stable hydrolysis product of prostacyclin are described and compared. Prostaglandins were extracted from biological fluids with organic solvents. Samples for gas chromatographic mass spectrometric analysis required additional thin-layer chromatographic separation prior to conversion to the O-methyloxime, methyl ester, tri-trimethylsilyl ether. Ion fragments at m/z 418 and 508 (protium) and m/z 422 and 512 (deuterium) were monitored to prepare 6-oxo-PGF1 alpha standard curves. The gas chromatographic mass spectrometric detection limit was 500 pg injected on column with a method coefficient of variation of 11.6% at this level. At 590 pg ml-1 the coefficient of variation for reproducibility of measurement was 1.77%. Antisera raised against a 6-oxo-PGF1 alpha-bovine serum albumin conjugate in sheep had a higher titre and greater selectivity than those raised in rabbits. Cross-reaction of sheep antisera with all prostaglandins and fatty acids tested was less than 0.5%. The radioimmunoassay limit of detection was 60 pg ml-1 (6 pg per tube) with a coefficient of variation of 10.4% (intra-assay) and 10.75% (inter-assay). The double blind comparison of gas chromatographic mass spectrometric and radioimmunoassay quantitation of the same samples gave a correlation coefficient of 0.97. Both methods offer sensitivity, selectivity and reproducibility. Gas chromatography mass spectrometry is necessary to validate the radioimmunoassay method which offers advantages of time, sample capacity and volume, expenditure and sensitivity.
TL;DR: A simple and fast method based on a fluorescence derivatization of the sulfhydryl group combined with a reversed-phase liquid chromatograhic separation and fluorescence detection permits a simple determination of D-penicillamine in serum at therapeutic levels.
TL;DR: It has been demonstrated that detection limits of between 40 and 100 pg can also be obtained for the photoproducts of the phenothiazines fenergan, largactil, levopromazine and nedaltran, and calibration graphs show good linearity and the analysis of spiked serum samples was successful.
TL;DR: The method was applied to human plasma samples in a comprehensive bioavailability study of levamisole in healthy volunteers, and to plasma and tissues in a residue trial in cattle, and pointed to decreased plasma concentrations when Vacutainer tubes were used.
TL;DR: The analytical figures of merit for fluorescence of sixty polynuclear aromatic hydrocarbons are presented in this article, where the limits of detection for most of the compounds are below 50 ng ml-1 and the average relative standard deviation at 1 μg ml 1 for each compound is 1.4%.
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TL;DR: A rapid and sensitive method was developed using high-pressure liquid chromatography, postcolumn, in-line hydrolysis of indomethacin to a fluorophore, and detection of the fluorophores wih a fluorometer, which resolved the nonconjugated metabolites of IndometHacin, aspirin, and salicylate.
TL;DR: In this article, the first attempt to apply alternating voltage polarography for detection in high-performance liquid chromatography is presented. And the performance of a flow-through polarographic detector in the a.v. mode is illustrated with the separation of a mixture of bile acids.
TL;DR: In this paper, the highly polar, nonvolatile N-nitrosamines, Nnitrosoproline, and N -nitrosodiethanolamine were determined by high-performance liquid Chromatographic separation with electrochemical detection using d.c. voltammetry, normal pulse voltametric, and differential pulse voltamermetry.
TL;DR: In this article, the detection limits for 36 prominent lines of the elements As, Au, B, Be, Bi, Ge, In, Mg, Mn, Ni, P, Pb, Se, Sn and Zn were computed on the basis of relationship (0) and measured signal-to-background ratios (SBR).
TL;DR: In this article, the fluorescamine reaction for primary amines has been used for the post-column derivatization of three chloroanilines at relatively low pH values, and separation was carried out on a CN-modified bonded phase with acetonitrile-water (pH 3) as the mobile phase.
TL;DR: In this paper, a flow injection analysis (FIA) method is described for the continuous, rapid determination of chemical oxygen demand (COD), which uses acidic potassium permanganate solution as both an oxidant and a spectrophotometric reagent, and glucose as a standard.
Abstract: A method is described for the continuous, rapid determination of chemical oxygen demand (COD). The method is based on flow injection analysis (FIA) and uses acidic potassium permanganate solution as both an oxidant and a spectrophotometric reagent, and glucose as a standard. COD values for aqueous environmental samples, such as industrial wastewaters, are compared with those obtained using the Japanese Industrial Standard (JIS) method and are found to be within an error range of ±30%. The method is comparable to other manual and automatic methods and has several advantages. A sampling rate of 20 samples per hour can be achieved, and the detection limit and precision are 5 mg l–1 as COD and 0.6%, respectively. Chloride ion up to levels of 6000 mg l–1 does not interfere, even in the absence of silver salts.
TL;DR: A method for the determination of D- and L-thyroxine in human serum using a reversed-phase, high-performance liquid chromatographic column by use of a chiral eluent containing L-proline and cupric sulfate is described.
TL;DR: In this paper, a closed-loop system was used for the determination of copper in human blood serum using a fixed-time, variable-signal kinetic determination with a limit of detection for copper(II) of 0.25 μg ml-1 and permits 325 determinations per hour with a relative standard deviation of 2%.
TL;DR: In this article, a reverse-phase ion-pair liquid chromatographic separation method has been established to analyse the content of 4(5)-methylimidazole in the extracts.