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

A solid sorbent personal dynamic air sampling method for aldehydes using chemisorption with 20 percent (w/w) O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride (PFBHA) on Tenax TA has been optimized for several aldehydes. The method for formaldehyde was developed after optimization for valeraldehyde and acrolein. The effects of temperature, intermittent exposure, and flow rate on sampling efficiency were investigated. Vapors of known concentrations were generated in Tedlar gas bags by syringe injection. Aldehyde chemisorption by reaction with 200-mg coated solid sorbent in a Pyrex Tube (7-cm length, 7-mm OD, and 5-mm ID) occurred during dynamic collection with a personal sampling pump operated at 10, 50, or 100 mL/min. The oxime derivatives were 81-87 percent desorbed by shaking with hexane for two minutes or more, resulting in coefficients of variation ranging between 4-7 percent. Aliquots were then injected for gas chromatographic analysis on a nonpolar capillary column with mass spectrometric or 63Ni electron capture detection. Formaldehyde at 8 ppm-hours equivalent to the permissible exposure limit (PEL) concentration was sampled with a recovery of 94 +/- 4 percent at 50.0 +/- 0.5 mL/min. Valeraldehyde and acrolein at their PELs showed no significant differences (P < 0.05) in recoveries at different relative humidities (1 and 90%), temperatures (1, 25, and 40 degrees C), or intermittent sampling protocol. The sampler capacity at 75 percent recovery was at a PFBHA:aldehyde molar ratio of 12:1 at 10.0 +/- 0.1 mL/min, 17:1 at 50.0 +/- 0.5 mL/min, and 26:1 at 100 +/- 1 mL/min.
 ...
PMID:Optimization of a solid sorbent dynamic personal air sampling method for aldehydes. 1067 81

An efficient method was developed for the analysis of selected PCBs and PAHs in dry peat samples. The method includes a shaking extraction using acetone and hexane followed by the purification of the crude extract by gel permeation chromatography (GPC) which turned out to be the key clean-up step. The method was used to determine seven indicator PCBs and 16 EPA-PAHs in individual sections of an ombrotrophic peat core in south-west Switzerland. The maximum concentrations of PCBs (19 microg sigma PCBs/kg dm) were found at a peat depth of 10-15 cm which is estimated to correspond to a time period of 1976-1960 whereas the PAH profile showed a maximum (2853 microg sigma PAHs/kg dm) at a depth of 20-25 cm which represents circa 1951-1930. Compared to these maxima, the concentrations of PAHs in the top layer (1990-1986) are six times lower, but the decline in PCBs is only 38%. The concentration profiles are generally consistent with known changes in contaminant emissions, and suggest that more detailed studies of ombrogenic peat bog profiles could be used for detailed reconstructions of the changing atmospheric fluxes of these and other organic contaminants.
 ...
PMID:Concentrations and distribution of some polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) in an ombrotrophic peat bog profile of Switzerland. 1128 17

Different liquid-solid extraction techniques, including room-temperature leaching with mechanical shaking, ultrasonic, and microwave-assisted extractions, have been evaluated for the quantitative speciation of tin for mono-, di-, and tributyltin (MBT, DBT, and TBT, respectively) in PACS-2 and BCR-646 certified reference materials. A methanol-acetic acid mixture was used as the extractant reagent in all cases. For this purpose, a mixed spike containing 119Sn-enriched MBT (79.7 At%), 118Sn-enriched DBT (86.7 At%), and 119Sn-enriched TBT (83.1 At%), was synthesized, characterized, and used for isotope dilution analysis. The isotopic composition of the mixed spike was determined by gas chromatography/ICPMS after aqueous ethylation using sodium tetraethylborate, and the determination of the concentration of the different species in the spike was performed by means of reverse isotope-dilution analysis using natural MBT, DBT, and TBT standards. In the analysis of the certified sediments, the sample was spiked with the mixed spike, extracted under different conditions, derivatized with sodium tetraethylborate, and extracted into hexane, and the isotope ratios 120/118 and 120/119 were measured as peak area ratios for all butyltin species after GC/ICPMS. Mass bias was corrected using a derivatized natural standard every three sample injections. Sequential degradation reactions during extraction (from TBT to DBT, from DBT to MBT, and from MBT to inorganic tin) were assumed, and mathematical equations were developed that allowed the determination of the correct species concentration and the decomposition factor for each of the transformation reactions. For ultrasonic extraction and mechanical shaking, negligible degradation reactions were observed. However, for microwave assisted extractions, degradation factors up to 7% (TBT to DBT) and 16% (DBT to MBT) were obtained for both reference materials when high-MW energy was applied in the extraction step. For the three extraction techniques tested, the DBT and TBT concentration values obtained for PACS-2 closely matched the certified values. However, for MBT the concentrations found by microwave and ultrasonic extraction were much higher than the certified value. This was not the case for mechanical shaking. The results obtained for BCR-646 using microwave assisted extraction were in good agreement with the certified values for all tin species.
 ...
PMID:Evaluation of extraction techniques for the determination of butyltin compounds in sediments using isotope dilution-GC/ICPMS with 118Sn and 119Sn-enriched species. 1179 50

A procedure of clean-up with H2SO4 after extraction with a shaking machine using n-hexane, and fast determination of some organochlorine residues in eggs by GC-ECD with PCB2 and PCB209 as internal standards was established. The test results showed that with this method satisfactory recoveries(84.31%-116.77%), relative standard deviation (6%-18%) and detection limits (0.07 ng/g-0.35 ng/g) could be obtained. In comparing with the Soxhlet method, this method is simpler in pre-treatment, lower in cost and less in sample amount. It can determine organochlorine pesticides and some PCBs in the same extract, simultaneously with enough accuracy, sensitivity and permissible RSD. It is a suitable procedure for determining micro-amounts of organochlorine pollutants in foods. The results showed that p, p'-DDE was detected in maximum; p, p'-DDT next; and PCBs very little, that were usually less than 10 ng/g in the eggs from some Chinese markets. It was found that most of PCBs in eggs were the congeners with 3-5 chlorine atoms.
 ...
PMID:[Determination of organochlorine pesticides and polychlorinated biphenyl congeners residues in eggs by gas chromatography with electron capture detection (GC-ECD)]. 1254 78

Two typical cleanup methods, sulfuric acid treatment and multi-layer silica gel column chromatography, for the determination of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (dioxin-like PCBs) in seventeen food samples were examined and compared. Vegetables, fruits, cereals, fish, meat and dairy foods were extracted by conventional methods (shaking with acetone/n-hexane or with n-hexane after alkaline treatment). The extracts were cleaned up by sulfuric acid treatment or multi-layer silica gel column chromatography, followed by several column chromatographic steps. Of the samples treated, the vegetable, fruit and cereal samples could be directly applied to the multi-layer silica gel column after extraction. However, the samples containing fats and oils such as fish, meat and dairy foods needed to be treated several times with concentrated sulfuric acid before multi-layer column chromatography, because these samples plugged the column with oily residues. Both cleanup methods gave similar values of isomeric concentrations and showed similar efficiency of purification, and the recoveries ranged from 40 to 120%. These results are considered to provide useful data for the efficient analysis of dioxins in foods which have wide-ranging compositions.
 ...
PMID:Comparison of sulfuric acid treatment and multi-layer silica gel column chromatography in cleanup methods for determination of PCDDs, PCDFs and dioxin-like PCBs in foods. 1260 31

The cleanup procedure for the determination of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (PCBs) in food samples using a disposable pre-packed multi-layer silica gel column (multi-layer dioxin tube; D-tube) was evaluated. The blank test showed the need for conditioning of the column with n-hexane. To compare the method with the D-tube and the conventional method for the analyses of actual food samples, seven food samples (spinach, komatsuna, rice, salmon, beef, egg and butter) were extracted by shaking with acetone-n-hexane or n-hexane after alkaline treatment, and then the extracts were cleaned up by use of the D-tube or the prepared conventional column, followed by several column chromatographic steps. Both cleanup procedures gave similar values at each isomeric concentration level and showed similar efficiency with favorable recoveries. The results suggest that the D-tube is applicable to cleanup for the analysis of PCDD/Fs and dioxin-like PCBs in foods.
 ...
PMID:Cleanup of food samples with pre-packed multi-layer silica gel column for the analysis of PCDDs, PCDFs and dioxin-like PCBs. 1284 60

A rapid and simple method was developed for simultaneous determination of methyl, ethyl, isopropyl, npropyl, isobuthyl and n-buthyl p-hydroxybenzoic acid esters (PHBA-Es) in laver by HPLC. Six PHBA-Es were extracted from laver with n-hexane-ethyl acetate (1:1) by shaking. The extract was evaporated. The residue was dissolved in methyl alcohol and determined by HPLC. Recoveries of six PHBA-Es spiked in laver were 93.6-101.2% at the level of 2 micrograms/g.
 ...
PMID:[Determination of six p-hydroxybenzoic acid esters in laver (nori) by HPLC]. 1474 Apr 5

Dioxins, including polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/Fs) and coplanar polychlorinated biphenyls (Co-PCBs), such as mono-ortho-PCBs and non-ortho-PCBs, are environmental pollutants that have deleterious effects on human health. Although screening of blood samples for dioxins is necessary, the current methods are time-, reagent- and labor-intensive. To optimize the extraction and cleanup of dioxins, we have designed a column chromatography method, coupled with a water washing step. We used a tandem simplified multilayer silica gel-activated carbon dispersed silica gel column (TS-ML-AC) rather than the conventional two columns. We compared three liquid-liquid extraction (LLE) methods and two pressurized liquid extraction (PLE) methods, when used with this column. For each of these extraction methods, we compared the quantity of lipid obtained when the water washing step was omitted and when it was performed by shaking 30 times by hand or 30 min by a machine. We found that TS-ML-AC was superior to the conventional pair of columns in that only about one third of the solvent and only one quarter of the time was necessary. Of the five extraction methods, the acetone/hexane PLE (AcP) method was superior, since it reduced the amount of organic solvent to half or less of the amount required for the LLE methods. The cleanup step using water was best accomplished by the hand-shaking method. Our results indicate that, for the analysis of dioxin in whole blood samples, the use of AcP together with TS-ML-AC and water washing by hand shaking should be used.
 ...
PMID:Optimization of a method for determining dioxin in whole blood samples based on solvent extraction and simplified cleanup. 1504 62

The effect of high pressure gradients with the help of the membrane under which a decreased pressure is created and centrifugal forces on a decrease of the content of the dispersion medium in the emulsion and foam and increase in the capillary pressure was studied. In a centrifugal field at low angular velocity of rotation (omega=52.3 s(-1)) the equilibrium capillary pressure is established in the emulsion and foam. At higher angular velocity the emulsion and foam were collapsed as a certain pressure is reached in Plateau borders of the emulsion and foam; this pressure was smaller than the pressure balancing the forces of the centrifugal field. The capillary pressure in the highly dispersed emulsion reached pressure drop applied to the membrane (P(sigma)=P(T)=70 kPa). Emulsions from sodium dodecylsulfate and 9-10 oxyethylated alkylphenol (OP-7) with 0.1 and 0.4 mol/dm(3) NaCl adding prepared by shaking with hexane and dodecane destructed at some capillary pressure which were less than the pressure drop supplied to the porous membrane.
 ...
PMID:Investigation of foam and emulsion destruction under the great pressure gradients. 1507 39

To clarify the neuromotor effects of long-term exposure to mixed organic solvents, postural sway and tremor were measured in 62 solvent workers of four Buddhist altar manufacturing factories who had worked for 1-46 (mean 12) yr. By using the passive gas sampler, 8-h time-weighted average concentrations in the workers were estimated to be 0.02-8.7 ppm for toluene, 0.02-7.7 ppm for xylene, 0.02-5.5 ppm for styrene and 0.02-40.5 ppm for n-hexane. Sagittal sway and sway area of the posturography with eyes closed were significantly larger in the solvent workers than in 35 age-matched controls (p<0.05), and there was a significant difference in Romberg quotient of sagittal sway between the two groups (p<0.05). Also, tremor intensities at 1.0-5.9 Hz, 6.0-9.9 Hz and 10.0-13.9 Hz with the right hand, and at 6.0-9.9 Hz with the left hand were significantly stronger in the solvent workers than in the controls. Among the solvent workers, transversal and sagittal sways with eyes open and tremor intensity at 10.0-13.9 Hz were significantly related to toluene exposure (p<0.05), which may have been due to the acute effects of such solvents. These findings suggest that long-term exposure to mixed organic solvents may impair neuromotor functions as measured by postural sway and tremor.
 ...
PMID:Effects of mixed organic solvents on neuromotor functions among workers in Buddhist altar manufacturing factories. 1582 79


<< Previous 1 2 3 4 5 Next >>