Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0040822 (tremor)
 18,428 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A simple and rapid method based on microwave-assisted extraction (MAE) coupled to gas chromatographic analysis was developed for the analysis of triazine (atrazine, cyanazine, metribuzine, simazine and deethylatrazine, and deisopropylatrazine) and chloroacetanilide (acetochlor, alachlor, and metolachlor) herbicide residues in soils. Soil samples are processed by MAE for 5 min at 80 degrees C in the presence of acetonitrile (20 mL/sample). Mean recovery values of most solutes are >80% in the 10 to 500 microg/kg fortification range with respective RSDs (relative standard deviations) < 20%. The limits of quantification (LOQ) and limits of detection (LOD) are 10 and 1 to 5 microg/kg, respectively. The method was validated with two types of soils containing 1.5 and 3.0% organic matter content, respectively; no statistically significant differences were found between solute recovery values from the two types of soils. The solute mean recovery values from freshly spiked (24 h aging) and spiked samples stored refrigerated for one week before processed were also not statistically different. Residue levels determined in field weathered soils were higher when soils were processed by MAE than with a comparison method based on flask-shaking of soil suspensions overnight. Extracts were analyzed by a gas chromatographic system equipped either with a thermionic (GC-NPD) or a mass spectrometric detector (GC-MS).
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PMID:Determination of triazine and chloroacetanilide herbicides in soils by microwave-assisted extraction (MAE) coupled to gas chromatographic analysis with either GC-NPD or GC-MS. 1218 2

A method for determination of riboflavin in animal feeds using liquid chromatography (LC) was developed for feed samples fortified with riboflavin at 1 mg/lb or greater (up to 10,000 mg/lb). Feed samples were extracted in 0.1 N HCl with heating on a steam bath for 30 min, followed immediately by mechanical shaking for 30 min. Sample extracts were diluted to target volume with 2% acetic acid and filtered; riboflavin was determined by LC on a reversed-phase C18 column with 2% acetic acid-acetonitrile (85 + 15) mobile phase for separation and fluorescence detection with excitation at 460 nm and emission at 530 nm. The extraction was compared with that of the AOAC Official Method for riboflavin in food and feed premixes. The 2 method extractions were not significantly different from each other at the 95% confidence level. The developed method also had good linearity over 4 orders of magnitude, recovery of 95-99% from spiked feed samples, a limit of detection of riboflavin at 0.00034 microg/mL in solution, a limit of quantitation of 0.023 mg/lb in feed, and good ruggedness.
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PMID:Reversed-phase liquid chromatographic determination of riboflavin in feeds. 1272 5

A convenient method was developed for determination of sulfathiazole (STZ) in Type C medicated swine feed by reversed-phase liquid chromatography (LC) with post-column derivatization. Addition of extractant solution (0.2N HCl and 1.5% diethylamine in 25% methanol) and an internal standard (IS), sulfamethylthiazole (SMZ), to 5 g sample was followed by mechanical shaking for 1 h. The extract was clarified by chilling, centrifugation, and filtering before injection onto a C18 reversed-phase column. The mobile phase components were 2% acetic acid and 1:1 acetonitrile-methanol (83 + 17%, v/v). Run time was about 20 min. Determination and, largely, the method's selectivity were based on detection at 450 nm of the derivative formed by the post-column reaction of dimethylaminobenzaldehyde with the primary amine of the analyte and IS. The IS, SMZ, differs from STZ by a single substituent methyl group, is stable, and is readily resolved from STZ. Although SMZ is not commercially available, it can be synthesized with relative ease from purchased reagents and will be supplied by the authors to interested laboratories. In single-laboratory validation, linearity was demonstrated over the range of 0.055-550 microg/mL, well beyond the target concentration of 5.5 microg/mL. The estimated limit of detection was 0.04 microg/mL; the calculated limit of quantitation was 0.13 microg/mL (feed concentration of 2.4 g/T or 2.7 mg/kg). Wet-spiking trials with a variety of swine feed matrixes showed recovery to be 100-102% for the intended concentration range, 50-200 g/T, with coefficient of variation (CV) < 2%. The method ruggedness was verified with an overall CV of 2.9%.
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PMID:Determination of sulfathiazole in type C medicated swine feed by reversed-phase liquid chromatography with post-column derivatization. 1450 17

Liquid chromatography (LC) with diode array ultraviolet absorbance (DAD UV) detection is used for the simultaneous determination of the fungicide maneb and its main metabolites (ethylenethiourea--ETU, ethylenebis (isothiocyanate) sulfide--EBIS, and ethyleneurea--EU) in tomatoes. The identity of EBIS, one of the main UV degradation products of maneb, was verified by both DAD UV detection and mass spectrometry. The analytes were extracted three times with 3 mL of 1:1:1 acetonitrile-dichloromethane-chloroform by 2 min of mechanical shaking and separated on a C-18 column by gradient elution with an acetonitrile-methanol-aqueous 100mM sodium dodecylsulfate (SDS) mixture. The quantification limits of 0.45, 0.04, and 0.35 mg kg(-1) obtained for maneb, ETU, and EU, respectively, show that the proposed method is suitable for their determination in tomatoes.
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PMID:Simultaneous determination of maneb and its main metabolites in tomatoes by liquid chromatography using diode array ultraviolet absorbance detection. 1533 96

Intact photosensitive cyclometalated RuII derivatives of 2-phenylpyridine or N,N-dimethylbenzylamine cis-[Ru-(C approximately N)(LL)X2]PF6 [C approximately N = o-C6H4-py or o-C6H4CH2NMe2; LL = 1,10-phenanththroline (phen), 2,2'-bipyridine (bpy), or 4,4'-Me2-2,2'-bipyridine (Me2bpy); X = MeCN or pyridine (py)] are efficient mediators of glucose oxidase (GO) from Aspergillus niger and horseradish peroxidase (HRP). Their redox potentials in an aqueous buffer are in the range 0.15-0.35 V versus SCE, and the rate constants for the oxidation GO(red) (where red indicates reduced) by the electrochemically generated RuIII species equal (1.7-2.5) x 10(6) M(-1) s(-1) at pH 7 and 25 degrees C. The redox potentials of all complexes decrease cathodically by 0.4-0.6 V upon irradiation by visible light because of the photoinduced solvolysis of acetonitrile or py ligands. These in situ generated species display an even better mediating performance with HRP, although their behavior toward GO is different. The loading of a ruthenium unit into the protein interior brings about large catalytic currents in a self-assembled system GO-Ru-D-glucose. The estimated rate constant for intramolecular electron transfer from FADH2 of the active site at RuIII, k(intra), equals 4.4 x 10(3) s(-1). This suggests that the distance between the redox partners is around 19 A. The value of 21 A was obtained through the docking analysis of a possible closest-to-FAD localization of a Ru-containing fragment derived from the irradiated complex cis-[Ru(o-C6H4-py)-(phen)(MeCN)2]PF6. The operational stability of the GO-Ru assemblies depends on the nature of complex used, the highest being observed for cis-[Ru(o-C6H4-py)(Me2-bpy)(MeCN)2]PF6 (2). UV-vis studies of interaction of 2 with GO revealed photomechanical oscillations in the system GO-Ru-D-glucose. When irradiated complex 2 is mixed with GO and D-glucose, the absorbance at 510 nm increases because of the enzymatic reduction of RuIII to RuII. The absorbance drops rapidly and then increases as in the first cycle after shaking the reaction solution. Many cycles are possible, and the rate of absorbance increase does not depend on a cycle number. A plausible mechanism of the oscillations is presented.
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PMID:Redox mediation and photomechanical oscillations involving photosensitive cyclometalated Ru(II) complexes, glucose oxidase, and peroxidase. 1585 96

Validation experiments were conducted of a simple, fast, and inexpensive method for the determination of 229 pesticides fortified at 10-100 ng/g in lettuce and orange matrixes. The method is known as the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method for pesticide residues in foods. The procedure involved the extraction of a 15 g sample with 15 mL acetonitrile, followed by a liquid-liquid partitioning step performed by adding 6 g anhydrous MgSO4 plus 1.5 g NaCl. After centrifugation, the extract was decanted into a tube containing 300 mg primary secondary amine (PSA) sorbent plus 1.8 g anhydrous MgSO4, which constituted a cleanup procedure called dispersive solid-phase extraction (dispersive SPE). After a second shaking and centrifugation step, the acetonitrile extract was transferred to autosampler vials for concurrent analysis by gas chromatography/mass spectrometry with an ion trap instrument and liquid chromatography/tandem mass spectrometry with a triple quadrupole instrument using electrospray ionization. Each analytical method was designed to analyze 144 pesticides, with 59 targeted by both instruments. Recoveries for all but 11 of the analytes in at least one of the matrixes were between 70-120% (90-110% for 206 pesticides), and repeatabilities typically <10% were achieved for a wide range of fortified pesticides, including methamidophos, spinosad, imidacloprid, and imazalil. Dispersive SPE with PSA retained carboxylic acids (e.g., daminozide), and <50% recoveries were obtained for asulam, pyridate, dicofol, thiram, and chlorothalonil. Many actual samples and proficiency test samples were analyzed by the method, and the results compared favorably with those from traditional methods.
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PMID:Validation of a fast and easy method for the determination of residues from 229 pesticides in fruits and vegetables using gas and liquid chromatography and mass spectrometric detection. 1585 89

A modification that entails the use of buffering during extraction was made to further improve results for certain problematic pesticides (e.g., folpet, dichlofluanid, chlorothalonil, and pymetrozine) in a simple, fast, and inexpensive method for the determination of pesticides in produce. The method, known as the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method for pesticide residues in foods, now involves the extraction of the sample with acetonitrile (MeCN) containing 1% acetic acid (HAc) and simultaneous liquid-liquid partitioning formed by adding anhydrous MgSO4 plus sodium acetate (NaAc). The extraction method is carried out by shaking a centrifuge tube which contains 1 mL of 1% HAc in MeCN plus 0.4 g anhydrous MgSO4 and 0.1 g anhydrous NaAc per g sample. The tube is then centrifuged, and a portion of the extract is transferred to a tube containing 50 mg primary secondary amine sorbent plus 150 mg anhydrous MgSO4/mL of extract. After a mixing and centrifugation step, the extract is transferred to autosampler vials for concurrent analysis by gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/tandem mass spectrometry. Independent of the original sample pH, the use of buffering during the extraction yields pH <4 in the MeCN extract and >5 in the water phase, which increases recoveries of both acid- and base-sensitive pesticides. The method was evaluated for 32 diverse pesticides in different matrixes, and typical percent recoveries were 95 +/- 10, even for some problematic pesticides. Optional solvent exchange to toluene prior to GC/MS analysis was also evaluated, showing equally good results with the benefit of lower detection limits, but at the cost of more time, material, labor, and expense.
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PMID:Use of buffering and other means to improve results of problematic pesticides in a fast and easy method for residue analysis of fruits and vegetables. 1585 90

Tetracaine hydrochloride (TH) is nominated as the prohibited ingredients in cosmetics in Japanese Pharmaceutical Affairs Act. So the analytical method for TH was investigated by HPLC. After adding 5 ml of TH solution at 10 microg/ml and 2 ml of salicylic acid solution at 75 microg/ml as the internal standard to 0.5 g of the lotion, the mixture was made up to 10 ml with a mixture of water and methanol (1:1) as the testing solution. Milky lotion was procedured as follows: After adding 5 ml of TH solution at 10 microg/ml and 2 ml of internal standard solution to 0.5 g of the milky lotion, the mixture was made up to 10 ml with a mixture of water and methanol (1:1). Two milliliter of this mixture was placed into a centrifuging tube with a cap and 2 ml of hexane was added. After shaking vigorously and centrifuging, the lower layer was used as the testing solution. In the case of the cream, the other procedures were used: 0.5 g of cream was placed into a 10-ml volumetric flask and 1 ml of tetrahydrofuran was added. After dissolving, the mixture of methanol and water (1:1) was added to make up 10.0 ml. Two milliliter of this mixture was placed into a centrifuging tube with a cap and 2.0 ml of hexane was added. After shaking vigorously and centrifuging, the lower layer was used as the testing solution. The testing solution of 20 microl was analyzed by HPLC using the ODS column (CAPCELL PAK C18 column, 4.6 x 250 mm), the mixture of acetonitrile and 50 mmol/l phosphate buffer(pH 2.0)(7:3) and the detection wavelength of 303 nm. The working curves from 0.5 to 6.0 microg/ml showed a linear line between the concentrations of TH and the peak area ratio. There was no interference of peak of TH from the lotion, milky lotion and cream.
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PMID:[Studies for analyzing prohibited ingredients such as tetracaine hydrochloride in cosmetics]. 1594 Sep

Ginseng saponins (ginsenosides) were extracted from the root and leaves of locally cultivated American ginseng (Panax quinquefolium L.). For the isolation of compounds from plant samples three different extraction methods were utilized: accelerated solvent extraction, the ultrasound-assisted solvent extraction and mechanical shaking assisted solvent extraction. The separation of compounds was achieved with a water-acetonitrile gradient system using a C18 reversed-phase column. Target compounds were identified in MS(2) and MS(3) experiments. The relative distribution of these ginsenosides in each root and leaf extract was established. The limit of detection of the method was less than 30 ng/ml. Recovery of ginseng saponins in spiked samples exceeded 80%, while the relative standard deviation ranged from 7.1 to 9.1%. The total concentrations of ginsenosides were 41 and 13 mg/g in root and leaves.
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PMID:Isolation and determination of ginsenosides in American ginseng leaves and root extracts by LC-MS. 1628 69

A simple and accurate method for the determination of andrographolide and dehydroandrographolide in andrographis paniculata Nees materials and patent medicines with high performance liquid chromatography (HPLC) has been developed. The two components were extracted from powdered samples by shaking with methanol. The resultant extracts were separated within 15 min on a BECKMAN C18 column (4.6 mm i. d. x 250 mm, 5 microm) and with a gradient elution of acetonitrile-water at a flow rate of 0.5 mL/min. The detection wavelength was 225 nm and the injection volume was 20 microL. In gradient elution program the volume fraction of acetonitrile in mobile phase was as follows: 0 min - 1 min, 40%; 1 min - 5 min, 40% - 50%; 5 min - 15 min, 50% - 70%. Both andrographolide and dehydroandrographolide have good linearity in the range of 10 mg/L to 100 mg/L with the correlation coefficients of 0.997 6 and 0.998 6 respectively. This method has been successfully applied for the analysis of andrographis paniculata Nees materials and related patent medicines.
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PMID:[Determination of andrographolide and dehydroandrographolide in Andrographis paniculata nees materials and related patent medicines by reversed-phase high performance liquid chromatography]. 1635 99


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