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Query: CAS:25150-61-2 (pyrrolidine)
 5,499 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A procedure for the determination of gallium by differential pulse adsorptive stripping voltammetry (DPADSV), using different complexing agents (ammonium pyrrolidine dithiocarbamate (APDC), pyrocatechol violet (PCV) and diethyldithiocarbamate (DDTC)), has been optimized. The selection of the experimental conditions was made using experimental design methodology. Under these conditions, the calibration was made and the detection limit was determined for each gallium-ligand complex. A robust regression method was applied which allowed the elimination of anomalous points. The detection limit, with alpha=beta=0.05, for gallium-APDC complex was 5.0x10(-8)moldm(-3), for gallium-PCV complex was 9.9x10(-9)moldm(-3), and the lowest detection limit (1.3x10(-9)moldm(-3)) was obtained with DDTC. For this reason, DDTC was selected for the determination of the gallium concentration in a certificate sample and in a spiked tap water sample. The linear dynamic range for gallium-APDC complex was from 5.0x10(-8) to 2.7x10(-7)moldm(-3), for gallium-PCV complex was from 5.0x10(-9) to 4.8x10(-7)moldm(-3), and for gallium-DDTC complex was from 1.0x10(-9) to 2.1x10(-7)moldm(-3).
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PMID:Determination of gallium by adsorptive stripping voltammetry. 1896 18

A precise and accurate indirect analytical method for the assessment of O(2) solubility in molten (Li(0.62)K(0.38))(2)CO(3) and (Li(0.52)Na(0.48))(2)CO(3) is described. The method is based on the oxidation of Cr(2)(SO(4))(3) (added in excess to the melt) by the oxygenate species, which are formed inside the melt when it is in contact with oxygen gas, and subsequent determination of trace amount of Cr(VI) in withdrawn frozen melts by flame atomic absorption spectrometry (FAAS). The samples (1.0-2.0g) are dissolved in dilute hydrochloric acid at room temperature. The speciation of Cr(VI) is carried out by complexation with ammonium pyrrolidine dithiocarbamate (APDC), followed by extraction into methyl isobutyl ketone (MIBK), which is introduced directly into the flame. Optimisation of the flame composition provided maximum Cr signal in organic phase under lean acetylene-air flame. The separation and preconcentration parameters such as sample volume/extractant volume ratio, pH sample solution, chelating concentration and extraction time are evaluated. Under the optimised conditions Cr(VI) is efficiently separated from Cr(III), which exceeded 200-folds. The results of the analysis of synthetic samples using standards in MIBK medium give rise to recoveries of 98-99%. The Cr(VI) detection limit of 4x10(-6)gL(-1) using 12.5-fold preconcentration and relative standard deviation of 1% at the 0.10mgL(-1) level are obtained. The sampling-to-sampling reproducibility was typically 3-5% relative standard deviation. By changing the preconcentration factor and the dilution of the sample melt, it is possible to analyse oxygen concentrations in molten alkali metal carbonates as low as 1.5x10(-9)mol O(2) per gram melt.
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PMID:Sensitive assay for oxygen solubility in molten alkali metal carbonates by indirect flame atomic absorption spectrometric Cr(VI) determination. 1896 74

A continuous flow system for the determination of lead in home made spirituous beverages was developed. The determination was based on the formation of a neutral chelate of the element with ammonium pyrrolidine dithiocarbamate, its adsorption onto a minicolumn packed with sodium faujasite type Y synthetic zeolite, followed by elution with methyl isobutyl ketone and determination by flame atomic absorption spectrometry. Ethanol and copper interfere strongly in the determination and therefore, must be separated prior to the analysis. Copper is removed by precipitation with rubeanic acid, while ethanol is eliminated by rotaevaporation. Sample solutions containing Pb(2+) in the concentration range from 5 to 120mugl(-1) at pH 2.5 could be analyzed, by using a preconcentration time of 3min. Preconcentration factors from 80 to 140 were achieved for a sample volume of 6ml and the detection limit varied from 1.4 to 3.5mugl(-1), depending on the matrix composition. The relative standard deviations for 60mugl(-1) Pb was 3.2% (n = 10) and the recovery of spikes (20, 40, 60 and 80mugl(-1)) added to the samples was estimated within 92-105% range, suggesting that lead can be quantitatively determined in such samples. Determining lead in several samples by an alternative technique further checked the accuracy. Finally, the concentrations of Pb(2+) determined in 28 samples of Venezuelan spirituous beverages were in 12.6-370.0mugl(-1) range, depending on the fermenting material based on different mixtures of agave, raw sugar cane and white sugar.
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PMID:Continuous flow system for lead determination by faas in spirituous beverages with solid phase extraction and on-line copper removal. 1896 53

Our previous study showed that insulin restored impaired function and expression of P-glycoprotein in diabetic blood-brain barrier, and further study showed that insulin up-regulated P-glycoprotein expression and function in normal blood-brain barrier, so insulin might be one of the factors that regulated the function and expression of P-glycoprotein in blood-brain barrier of diabetes. In this study, the intracellular pathways that insulin regulated the P-glycoprotein were investigated using primarily cultured rat brain microvessel endothelial cells model. The rat brain microvessel endothelial cells were incubated in normal culture medium containing 50 mU/l insulin and different concentrations of inhibitors for 72 h. The P-glycoprotein function and expression in the rat brain microvessel endothelial cells were assessed using the uptake of P-glycoprotein substrate rhodamine 123 and western blot assay, respectively. It was found that treatment of 50 mU/l insulin significantly increased P-glycoprotein function and expression in rat brain microvessel endothelial cells. This induced effect was blocked by insulin receptor antibody, insulin receptor tyrosine kinase inhibitor I-OMe-AG538, PKC inhibitor chelerythrine and NF-kappaB inhibitor pyrrolidine dithiocarbamate ammonium (PDTC). But this induced effect was not inhibited by phosphatidylinositol 3-kinase (PI3K)/Akt inhibitor LY294002. These results indicated that insulin regulated P-glycoprotein function and expression through signal transduction pathways involving activation of PKC/NF-kappaB but not PI3K/Akt pathway.
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PMID:Insulin regulates P-glycoprotein in rat brain microvessel endothelial cells via an insulin receptor-mediated PKC/NF-kappaB pathway but not a PI3K/Akt pathway. 1904 3

A simple solid phase extraction procedure for speciation of selenium(IV) and selenium(VI) in environmental samples has been proposed prior to graphite furnace atomic absorption spectrometry. The method is based on the solid phase extraction of the selenium(IV)-ammonium pyrrolidine dithiocarbamate (APDC) chelate on the Diaion HP-2MG. After reduction of Se(VI) by heating the samples in the microwave oven with 4moll(-1) HCl, the system was applied to the total selenium. Se(VI) was calculated as the difference between the total selenium content and Se(IV) content. The experimental parameters, pH, amounts of reagents, eluent type and sample volume were optimized. The recoveries of analytes were found greater than 95%. No appreciable matrix effects were observed. The adsorption capacity of sorbent was 5.20mgg(-1) Se (IV). The detection limit of Se (IV) (3sigma, n=11) is 0.010mugl(-1). The preconcentration factor for the presented system was 100. The proposed method was applied to the speciation of selenium(IV), selenium(VI) and determination of total selenium in natural waters and microwave digested soil, garlic, onion, rice, wheat and hazelnut samples harvested various locations in Turkey with satisfactory results. In order to verify the accuracy of the method, certified reference materials (NIST SRM 2711 Montana Soil, NIST SRM 1568a Rice Flour and NIST SRM 8418 Wheat Gluten) were analyzed and the results obtained were in good agreement with the certified values. The relative errors and relative standard deviations were below 6 and 10%, respectively.
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PMID:Speciation of selenium(IV) and selenium(VI) in environmental samples by the combination of graphite furnace atomic absorption spectrometric determination and solid phase extraction on Diaion HP-2MG. 1907 60

A novel method for preconcentration of methylmercury and inorganic mercury from water samples was developed involving the determination of ngl(-1) levels of analytes retained on the silica C(18) solid sorbent, previous complexation with ammonium pyrrolidine dithiocarbamate (APDC), by slurry sampling cold vapor atomic absorption spectrometry (SS-CVAAS) in a flow injection (FI) system. Several variables were optimized affecting either the retention of both mercury species, such as APDC concentration, silica C(18) amount, agitation times, or their determination, including hydrochloric acid concentration in the suspension medium, peristaltic pump speed and argon flow-rate. A Plackett-Burman saturated factorial design permitted to differentiate the influential parameters on the preconcentration efficiency, which were after optimized by the sequential simplex method. The contact time between mercury containing solution and APDC, required to reach an efficient sorption, was decreased from 26 to 3min by the use of sonication stirring instead of magnetic stirring. The use of 1moldm(-3) hydrochloric acid suspension medium and 0.75% (m/v) sodium borohydride reducing agent permitted the selective determination of methylmercury. The combination of 5moldm(-3) hydrochloric acid and 10(-4)% (m/v) sodium borohydride was used for the selective determination of inorganic mercury. The detection limits achieved for methylmercury and inorganic mercury determination under optimum conditions were 0.96 and 0.25ngl(-1), respectively. The reliability of the proposed method for the determination of both mercury species in waters was checked by the analysis of samples spiked with known concentrations of methylmercury and inorganic mercury; quantitative recoveries were obtained.
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PMID:Determination of methylmercury and inorganic mercury in water samples by slurry sampling cold vapor atomic absorption spectrometry in a flow injection system after preconcentration on silica C(18) modified. 1907 11

A new time-based flow injection on-line solid phase extraction method for chromium(VI) and lead determination using flame atomic absorption spectrometry was developed. The use of hydrophobic poly-chlorotrifluoroethylene (PCTFE)-beads as absorbent in on-line preconcentration system was evaluated. Effective formation of ammonium pyrrolidine dithiocarbamate complexes and subsequently retention in PCTFE packed column, was achieved in pH range 1.0-1.6 and 1.5-3.2 for Cr(VI) and Pb(II) ions, respectively. The sorbed analyte was efficiently eluted with isobutyl-methyl-ketone for on-line FAAS determination. The proposed packing material exhibited excellent chemical and mechanical resistance, fast kinetics for adsorption of Cr(VI) and Pb(II) permitting the use of high sample flow rates at least up to 15mLmin(-1) without loss of retention efficiency. For a preconcentration time of 90s, the sample frequency was 30h(-1), the enhancement factor was 94 and 220, the detection limit was 0.4 and 1.2mugL(-1), while the precision (R.S.D.) was 1.8% (at 5mugL(-1)) and 2.1% (at 30mugL(-1)) for chromium(VI) and lead, respectively. The applicability and the accuracy of the developed method were estimated by the analysis spiked water samples and certified reference material NIST-CRM 1643d (Trace elements in water) and NIST-SRM 2109 (chromium(VI) speciation in water).
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PMID:Determination of chromium(VI) and lead in water samples by on-line sorption preconcentration coupled with flame atomic absorption spectrometry using a PCTFE-beads packed column. 1907 15

An additional dimension has been added to our long-standing studies in high silica zeolite synthesis via a guest/host synergism. We have created and studied the impact of making symmetric diquaternary ammonium compounds, by varying the chain length between nitrogen charge centers, and the heterocycle size and geometry containing the nitrogen. This allows the introduction of a second spatial parameter in the use of the charged organo-cation guest in the zeolite synthesis. The series of 15 diquaternary ammonium compounds (5 heterocycles synthesized onto chain lengths of C4-C6) were tested in a total of 135 zeolite syntheses reactions. Nine screening reactions were employed for each guest molecule, and the conditions built upon past successes in finding novel high silica zeolites via introduction of boron, aluminum, or germanium as substituting tetrahedral framework atoms for silicon. Eighteen different zeolite structures emerged from the studies. The use of specific chain lengths for derivatives of the pyrrolidine ring system produced novel zeolite materials SSZ-74 and 75.
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PMID:Diquaternary ammonium compounds in zeolite synthesis: cyclic and polycyclic N-heterocycles connected by methylene chains. 1912 3

In this study, a challenging preconcentration/separation method based on the sorption of manganese on ethylene glycol dimethacrylatemethacrylic acid copolymer (EGDMA-MA) treated with ammonium pyrrolidine dithiocarbamate (APDC) and its slurry analysis by electrothermal atomic absorption spectrometry was described. Optimum conditions for quantitative sorption, as well as for preparing a homogeneous and stable slurry were investigated. A 100-fold enrichment factor could be reached. The analyte element in certified sea-water and bovine-liver samples were determined in the range of 95% confidence level. The proposed technique is fast, simple, and the risk of contamination is low. The limit of detection of the method for manganese in the slurry of the blank subjected to the proposed procedure was 0.07 microg L(-1) (3delta, N:10) corresponding to 0.56 microg kg(-1) slurry.
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PMID:Solid-phase extraction of Mn(II) and slurry analysis of the sorbent by electrothermal atomic absorption spectrometry. 1913 Feb 76

A new method of hollow fiber liquid phase microextraction (HF-LPME) using ammonium pyrrolidine dithiocarbamate (APDC) as extractant combined with electrothermal atomic absorption spectrometry (ETAAS) using Pd as permanent modifier has been described for the speciation of As(III) and As(V). In a pH range of 3.0-4.0, the complex of As(III)-APDC complex can be extracted using toluene as the extraction solvent leaving As(V) in the aqueous layer. The post extraction organic phase was directly injected into ETAAS for the determination of As(III). To determine total arsenic in the samples, first As(V) was reduced to As(III) by l-cysteine, and then a microextraction method was performed prior to the determination of total arsenic. As(V) assay was based on subtracting As(III) form the total arsenic. All parameters, such as pH of solution, type of organic solvent, the amount of APDC, stirring rate and extraction time, affecting the separation of As(III) from As(V) and the extraction efficiency of As(III) were investigated, and the optimized extraction conditions were established. Under optimized conditions, a detection limit of 0.12ngmL(-1) with enrichment factor of 78 was achieved. The relative standard deviation (R.S.D.) of the method for five replicate determinations of 5ngmL(-1) As(III) was 8%. The developed method was applied to the speciation of As(III) and As(V) in fresh water and human hair extracts, and the recoveries for the spiked samples are 86-109%. In order to validate the developed method, three certified reference materials such as GBW07601 human hair, BW3209 and BW3210 environmental water were analyzed, and the results obtained were in good agreement with the certified values provided.
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PMID:Hollow fiber liquid phase microextraction combined with electrothermal atomic absorption spectrometry for the speciation of arsenic (III) and arsenic (V) in fresh waters and human hair extracts. 1915 4


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