Showing papers on "Detection limit published in 1986"
TL;DR: In this paper, a fluorescent dimer is formed via the reaction of peroxides with p-hydroxyphenylacetic acid and horseradish peroxidase, which is stable for a minimum of 5 days.
Abstract: A derivatization technique has been developed for the combined determination of hydrogen peroxide and some organic hydroperoxides in precipitation samples. A fluorescent dimer is formed via the reaction of peroxides with p-hydroxyphenylacetic acid and horseradish peroxidase. The resulting dimer is stable for a minimum of 5 days, eliminating difficulties caused by the decomposition of peroxides in stored samples. The detection limit is 3 x 10/sup -8/ M, based on 3 times the standard deviation of the blank. 6 references, 1 figure, 3 tables.
113 citations
TL;DR: Application of the method to analysis of a milk sample was tested with aliquots spiked with known amounts of nitrite, with the detection limit approximately 0.5 ng ml in the test sample (1% relative fluorescence intensity).
94 citations
TL;DR: In this paper, an inductively coupled plasma (ICP) emission spectrometer was used as a high-performance liquid chromatographic detector for the determination of mercury compounds.
Abstract: An inductively coupled plasma (ICP) emission spectrometer was used as a high-performance liquid chromatographic detector for the determination of mercury compounds. Post-column cold vapour generation was used to obtain improved detection limits. The replacement of the conventional polypropylene spray chamber of the ICP by an all glass chamber is described. A comparison of band broadening indicates that the glass chamber is useful when a severe memory effect is observed with the polypropylene spray chamber. Detection limits ranged from 32 to 62 p.p.b. of mercury for four mercury compounds, based on a signal to noise ratio of 2:1. This represents a three to four order of magnitude enhancement over detection limits obtained without cold vapour generation. The approach is linear over three orders of magnitude. A blind, spiked distilled water study illustrates the reproducibility and accuracy of the method.
72 citations
TL;DR: The HPLC-AAS method for quantitating metallothioneins offers the advantage of determining the concentrations of both proteins in tissues and should be useful for studying the regulation of MT-I and MT-II.
62 citations
TL;DR: In this paper, a simple and rapid flow-injection method is described for determining buprenorphine hydrochloride (10−8−10−4 M) based on its chemiluminescent oxidation with potassium permanganate in polyphosphoric acid.
61 citations
TL;DR: In this paper, the determination of total Se in marine tissues and sediments and Se(IV) in seawater based on the generation of SeH/sub 2/ using NaBH/Sub 4/ with its subsequent trapping in a graphite furnace at 600/sup 0/C was described.
Abstract: Methods are described for the determination of total Se in marine tissues and sediments and Se(IV) in seawater based on the generation of SeH/sub 2/ using NaBH/sub 4/ with its subsequent trapping in a graphite furnace at 600/sup 0/C. Calibration is achieved with a simple aqueous working curve. The absolute detection limit is 70 pg with a concentration detection limit (3sigma) of 1.4 pg/g. Corresponding precision of 5-10% is typical for analyses of these samples. Results are reported for the determination of Se in a suite of marine reference materials. 25 references, 1 figure, 4 tables.
60 citations
TL;DR: In this paper, a manifold incorporation of activated alumina minicolumn is used to preconcentrate chromium(III), which is then eluted with 2 M nitric acid for detection.
59 citations
TL;DR: In this article, the authors used pulsed amperometric detection (PAD) at Pt and Au electrodes for the anodic detection of sulfur compounds, organic and inorganic, which adsorb on the electrode surface.
54 citations
TL;DR: The accuracy of the method is demonstrated by the excellent agreement with the results of micro-sampling flame atomic absorption spectrometry and with group mean values in external quality assessment programmes.
Abstract: A method is described for the routine determination of lead in whole blood by electrothermal atomisation from a L'vov platform and atomic absorption spectrometry. The sample preparation is a simple 1 + 19 dilution with a diluent containing a mixture of NH3 solution, NH4H2PO4 and (NH4)2H2EDTA. Further chemical modification is achieved using in situ oxygen ashing during electrothermal sample decomposition at 550 °C. Desorption of oxygen at 950 °C without losses of lead gives tube lifetimes of 200–250 firings. The calibration graph, established with matrix-matched standards and using integrated absorbance measurements, is linear for concentrations up to 5 µmol l–1. The detection limit is 8.3 × 10–12 g or 0.08 µmol l–1 of lead in blood. The within- and between-run precisions are 6.9% and 7.3%, respectively, at 0.5 µmol l–1 of lead, and the accuracy of the method is demonstrated by the excellent agreement with the results of micro-sampling flame atomic absorption spectrometry and with group mean values in external quality assessment programmes.
54 citations
TL;DR: In this article, a sensitive modification of the lumogallion fluorescence assay for aluminium is presented that exploits the 5-6fold increase in the fluorescence intensity of the luminogram-aluminium complex in the presence of the nonionic detergent Triton X-100.
Abstract: A sensitive modification of the lumogallion fluorescence assay for aluminium is presented that exploits the 5–6-fold increase in the fluorescence intensity of the lumogallion-aluminium complex in the presence of the non-ionic detergent Triton X-100. The sensitised procedure has a detection limit of 0.02 µg l–1 of Al (3σ) and a relative standard deviation of 5% at the 0.1 µg l–1 of Al level. The sensitivity of the method is independent of salinity and it can be used for the determination of aluminium in both fresh and saline waters. The interference from iron experienced in the conventional lumogallion procedure is also present in the modified method, but can be masked by the addition of 1,10-phenanthroline.
50 citations
TL;DR: A chemiluminescent tag for precolumn derivatization of amino acids has been developed in this paper, which couples with 17 amino acids tested, including proline and hydroxyproline, in less than ten minutes.
Abstract: A chemiluminescent tag for precolumn derivatization of amino acids has been developed. The tag, 4-isocyanatophthalhydrazide, couples with 17 amino acids tested, including proline and hydroxyproline, in less than ten minutes. Twelve derivatized amino acids have been separated and detected with an average detection limit of 10 femptomoles per 20 μL injection.
TL;DR: The utility of the method was demonstrated by analysing glibenclamide in samples from diabetic subjects on therapeutic doses of the drug.
TL;DR: In this paper, the optimum conditions for the adaptation of the spectrophotometric pyrocatechol violet method for aluminium to a flow-injection system are described, and the detection limit is 3 μg Al l−1 and calibration graphs are linear up to 3 or 10 mg l− 1 (with 200-μl or 10-μL injection loops, respectively).
TL;DR: In this paper, the determination of total As in sea water and in marine tissues and sediments based on the generation of AsH3 using NaBH4 with its subsequent trapping in a graphite furnace at 600 °C is described.
Abstract: Methods are described for the determination of total As in sea water and in marine tissues and sediments based on the generation of AsH3 using NaBH4 with its subsequent trapping in a graphite furnace at 600 °C. Calibration is achieved with a simple aqueous calibration graph having a sensitivity of 0.18 ± 0.03 A ng–1 and yields an absolute detection limit of 40 pg. Sample volumes of 10–500 µl produce total method concentration detection limits (3σ blank) of 60 pg g–1 in sea water, 0.2 µg g–1 in sediments and 0.15 µg g–1 in tissues. Corresponding precisions of 2–3% are typical for analyses of these samples. Results are reported for the determination of As in a suite of marine reference materials.
TL;DR: In this article, the metal chelate with erichrome black T is adsorbed on a hanging mercury drop electrode, and the subsequent reduction current of the accumulated chelate is measured by voltammetry.
TL;DR: An extremely sensitive voltammetric method is presented for trace measurement of the cancer chemotherapy drug methotrexate, based on controlled adsorptive preconcentration on the hanging mercury-drop electrode, followed by voltametric determination of the surface species.
TL;DR: In this paper, a highly sensitive and selective laser-based detector for high-performance liquid chromatography is presented, which combines the selectivity of fluorescence and the selectivities of optical activity to provide specificity.
TL;DR: In this article, a sensitive stripping voltammetric procedure for determining titanium is described, where the chelates of titanium with various dihydroxyazo dyes are adsorbed on the hanging mercury drop electrode, and the reduction current of the accumulated chelate is measured by voltammetry.
TL;DR: In this article, the authors used amperometric detection after separation in a diffusion cell with a teflon membrane to detect sulphur dioxide in wines. But the results showed that at 25°C, the calibration graph showed two linear ranges, between 0.06 and 6 mg l −1 and 12 and 110 ml l − 1, with a detection limit of 0.03 mg l−1.
TL;DR: This procedure can be readily adapted for the stereospecific assay of other beta-adrenoceptor blocking agents as demonstrated by the base-line separation of atenolol and acebutolol.
TL;DR: Cobalt phthalocyanine-containing carbon paste electrodes are used as electrocatalytic amperometric sensors for 6-mercaptopurine, 6-thioguanine, and several related thiopurines in blood plasma after separation by liquid chromatography as mentioned in this paper.
TL;DR: A high-performance liquid chromatographic method is developed that is selective with respect to the 5'-hydroxy metabolite, which is present in plasma after multiple administration of tenoxicam; this metabolite may also be determined using this procedure.
TL;DR: A reliable routine method is presented for the determination of piperazine down to the sub-ppm level in aqueous solutions and in urine following a two-phase derivatization procedure with ethyl- or isobutyl chloroformate as the reagent and a capillary gas chromatographic determination using nitrogen- or mass selective detection.
TL;DR: In this article, the integrative filter sampling method and the ion chromatographic analytical procedure gave a measurement precision of ±11.5 percent for particulate NO3 − on Teflon and ±15.6 percent for gaseous HNO3 on nylon; for both these constituents, the detection limit was about 0.1 μ m−3.
Abstract: Laboratory and field experiments were performed to evaluate integrative measurement methods for atmospheric nitrates, sulphate and sulphur dioxide. Denuder tubes and several filter media were tested under laboratory and field conditions. Effects of sampling variables such as temperature and relative humidity, flow rates, concentration, loading capacity and artifacts due to NO, NO2 and SO2 were also evaluated. The integrative filter sampling method and the ion chromatographic analytical procedure gave a measurement precision (relative standard deviation) of ±11.5 percent for particulate NO3 − on Teflon and ±15.6 percent for gaseous HNO3 on nylon; for both these constituents, the detection limit was about 0.1 μ m−3.
TL;DR: In this article, a high performance liquid chromatographic method for quantitating pentamidine in plasma was developed, which involved precipitating plasma with acetonitrile containing the internal standard, hexamidine.
Abstract: A high performance liquid chromatographic method for quantitating pentamidine in plasma has been developed. Sample clean-up involved precipitating plasma with acetonitrile containing the internal standard, hexamidine. The supernatant was passed through a C8 Bond Elut column and eluted with a methanolic solution of sodium 1-heptanesulfonate. The eluate was then analyzed on an Altex C8 column with a mobile phase consisting of 45% CH8CN, 0.02% detramethylammonium chloride and 0.1% H3PO4. Using fluorescence detection (EX: 275 nm and EM: 340 nm), the detection limit was 1.25 ng/ml for 0.5 ml of plasma. The coefficients of variation for interday and intraday were around 10%.
TL;DR: It was found that human neutrophils contain approximately 300 pg/10(6) cells which increased 2-3-fold during the 5-min period following challenge with 1.9 microM calcium ionophore, A23187.
TL;DR: In this paper, a new method has been developed for the routine determination of these toxic aromatic amines in urine at the ppb level, which is done using simple liquid-liquid extraction followed by a precolumn enrichment (PRP1material; Hamilton).
Abstract: For the title compounds 4,4′-DADPM, MOCA, 3,3′-DCB, 4-ADP and 4-ADPA listing on the EPA priority pollutant list, an analytical practicable, reliable, reproducible and sensitive procedure is required. Therefore a new method has been developed for the routine determination of these toxic aromatic amines in urine at the ppb level. The quantitative determination of amines is a suitable procedure of occupationally exposed persons. Urine sample preparation is done using simple liquid-liquid extraction followed by a precolumn enrichment (PRP1-material; Hamilton). Breakthrough measurements were done using an enrichment column packed with PRP1 material. The capacities of the studied amines ranged from 21.9mg/g to 96.6mg/g, while influent concentrations differed from 28.3mg/l to 332.0mg/l. The advantages of electrochemical detection regarding to selectivity and sensitivity are clearly indicated in this paper. Separation has been achieved applying reversed-phase-high-performance-liquid chromatography (LiChrosorb RP 18/5μm) followed by electrochemical or UV-detection. The detection limits employing an electrochemical detector at a potential of 1 V range from 2.2ng to 12.1ng. UV detection at 254 nm and 280 nm is about 10–100 times less sensitive. Recoveries from spiked water samples at the 5ppb levels were 75% to 96% respectively. The standard deviation of the developed procedure varies from 5.3% to 14%. Day-to-day repeatability is good.
TL;DR: In this article, a post-column chemiluminescence detection system was used for the first time in conjunction with high-performance liquid chromatography (HPLC) and compared with liquid-phase chemiluminine detection.
TL;DR: In this paper, the tranquilizers promethiazine, diethazine, trifluoperazine, fluphenazine and clozapin adsorb at the surface and extract into the wax-impregnated graphite electrode (WIGE) as shown by chronocoulometry.
TL;DR: A specific, sensitive and precise method for the determination of tramadol in human serum is described, which comprises a three-step extraction procedure and a specific determination by capillary gas chromatography with nitrogen-selective detection, using a homologue of Tramadol as an internal standard.