Thiodiglycolic acid (TdGA) is the major metabolite of vinyl chloride monomer (VCM) detected in human urine. Although urinary TdGA has been reported to be associated with ambient VCM exposure, the relationship between urinary TdGA and a low level of air VCM is not clear. Questionnaires were administered to 16 polyvinyl chloride manufacturing workers to obtain a detailed history of occupation and lifestyle. For each worker, personal air monitoring for VCM was performed and a time-weighted average for VCM exposure was calculated. The urinary TdGA levels at the end of a work shift, and at the commencement of the next shift, were also assessed for each worker. Urine analysis revealed that TdGA levels at the beginning of the next shift were higher than those at the end of that shift. Workers experiencing a VCM exposure greater than 5 ppm in air revealed a urinary TdGA level significantly greater than those experiencing a VCM exposure of less than 5 ppm (P < 0.05). The best fit of regression for urinary TdGA on air VCM was Y = 1.06 + 0.57X for urine collected at the commencement of the following work shift, where X is the air VCM concentration and Y is the urinary TdGA concentration (r2 = 0.65, P < 0.01). We conclude that the urinary TdGA level is best detected at the commencement of the next shift and that it can be used as an exposure marker for polyvinyl chloride workers when the air VCM level to which they are exposed is greater than 5 ppm.

A mathematical and computational model is introduced for optimization of background electrolyte systems for capillary zone electrophoresis of anions. The model takes into account mono- or di- or trivalent ions and allows also for modeling of highly acidic or alkaline electrolytes, where a presence of hydrogen and hydroxide ions is significant. At maximum, the electrolyte can contain two co-anions and two counter-cations. The mathematical relations of the model are formulated to enable an easy algorithmization and programming in a computer language. The model assesses the composition of the background electrolyte in the analyte zone, which enables prediction of the parameters of the system that are experimentally available, like the transfer ratio, which is a measure of the sensitivity in the indirect photometric detection or the molar conductivity detection response, which expresses the sensitivity of the conductivity detection. Furthermore, the model also enables the evaluation of a tendency of the analyte to undergo electromigration dispersion and allows the optimization of the composition of the background electrolyte to reach a good sensitivity of detection while still having the dispersion properties in the acceptable range. Although the model presented is aimed towards the separation of anions, it can be straightforwardly rearranged to serve for simulation of electromigration of cationic analytes. The suitability of the model is checked by inspecting the behavior of a phosphate buffer for analysis of anions. It is shown that parameters of the phosphate buffer when used at neutral and alkaline pH values possess singularities that indicate a possible occurrence of system peaks. Moreover, if the mobility of any analyte of the sample is close to the mobilities of the system peaks, the indirect detector signals following the background electrolyte properties will be heavily amplified and distorted. When a specific detector sensitive on presence of the analyte were used, the signal would be almost lost due to the excessive dispersion of the peak.

A simple and general method suitable for the determination of cyclodextrin content in various matrices is described. The proposed method involves selective cleavage of C-C bonds with vicinal hydroxyl groups by means of periodate (Malaprade's reaction). The amount of produced iodate is monitored by capillary electrophoresis. Optimized electrophoretic conditions (20 mM disodium tetraborate with 1 mM tetradecyltrimethylammonium bromide, direct UV detection lambda = 200 nm) ensure complete separation of periodate and iodate ions and sufficient sensitivity towards iodate. Under optimized reaction conditions (2-fold excess of periodate, temperature 70 degrees C) reproducible quantitative results were obtained for alpha-, beta- and gamma-cyclodextrins as model samples. The proposed method was tested on a real sample of acrylamide--2'-O-allyl-beta-CD copolymer. The values of beta-cyclodextrin content were compared with those obtained by reference NMR measurement and were found to be identical.

COMPASS tokamak shots at low magnetic field feature overdense plasmas during the extended current flat-top phase. The first harmonic of the electron cyclotron emission is completely cutoff for O and X modes and so the emission caused by electron Bernstein waves (EBWs) propagating obliquely with respect to the magnetic field and undergoing so called EBW-X-O conversion process can be observed. We perform an angular scan of the EBW emission during a set of comparable shots in order to determine the optimum antenna direction. A weak dependence of the radiative temperature on the antenna angles indicates an influence of multiple reflections from the vessel wall. The low temperature at the mode conversion region is responsible for the collisional damping of EBW, which can explain several times lower measured radiative temperature than the electron temperature measured by the Thomson scattering system.

Water clusters are known to undergo an autoprotonation reaction upon ionization by photons or electron impact, resulting in the formation of (H(2)O)(n)H(3)O(+). Ejection of OH cannot be quenched by near-threshold ionization; it is only partly quenched when clusters are complexed with inert gas atoms. Mass spectra recorded by electron ionization of water-doped helium droplets show that the helium matrix also fails to quench OH loss. The situation changes drastically when helium droplets are codoped with C(60). Charged C(60)-water complexes are predominantly unprotonated; C(60)(H(2)O)(4)(+) and (C(60))(2)(H(2)O)(4)(+) appear with enhanced abundance. Another intense ion series is due to C(60)(H(2)O)(n)OH(+); dehydrogenation is proposed to be initiated by charge transfer between the primary He(+) ion and C(60). The resulting electronically excited C(60)(+*) leads to the formation of a doubly charged C(60)-water complex either via emission of an Auger electron from C(60)(+*), or internal Penning ionization of the attached water complex, followed by charge separation within {C(60)(H(2)O)(n)}(2+). This mechanism would also explain previous observations of dehydrogenation reactions in doped helium droplets. Mass-analyzed ion kinetic energy scans reveal spontaneous (unimolecular) dissociation of C(60)(H(2)O)(n)(+). In addition to the loss of single water molecules, a prominent reaction channel yields bare C(60)(+) for sizes n=3, 4, or 6. Ab initio Hartree-Fock calculations for C(60)-water complexes reveal negligible charge transfer within neutral complexes. Cationic complexes are well described as water clusters weakly bound to C(60)(+). For n=3, 4, or 6, fissionlike desorption of the entire water complex from C(60)(H(2)O)(n)(+) energetically competes with the evaporation of a single water molecule.

Electron impact ionization of the gas phase 3-furanol, tetrahydro (3-hydroxytetrahydrofuran, 3HTHF) and 2-furanmethanol, tetrahydro (alpha-tetrahydrofurfuryl alcohol, THFA) molecules has been studied both experimentally and theoretically. The electron induced positive ion formation has been investigated experimentally using a crossed electron/neutral beams technique in combination with a quadrupole mass spectrometry. The mass spectra of both molecules have been determined at the incident electron energy of 70 eV. The ionization efficiency curves for each parent cation and a number of fragment cations have been measured near the threshold, and the corresponding appearance energies have been derived using an iterative fitting procedure based on the Wannier threshold law, taking into account the incident electron energy resolution. The appearance energies of the parent cations were experimentally determined to be (9.620+/-0.058) eV for (C(4)H(8)O(2)(+)/3HTHF) and (9.43+/-0.12) eV for (C(5)H(10)O(2)(+)/THFA), which are in a good agreement with G3MP2 calculated results: 9.480 and 9.419 eV, respectively. The most abundant cations in the mass spectra were determined to be 57 amu for 3HTHF and 71 amu for THFA, with the corresponding experimentally determined appearance energies of (10.22+/-0.10) eV and (9.574+/-0.062) eV, respectively. With the help of the energies calculated at B3LYP and G3MP2 levels of theory, the possible fragmentation patterns were discussed.

The design is described of a thin-layer contactless conductivity detector suitable for liquid chromatography and flow-injection analysis. Its principal analytical parameters have been determined using a potassium chloride solution: the linear dynamic range extends from 7.5x10(-6) to 1.5x10(-2)Sm(-1), corresponding to the KCl concentration range from 0.5 to 1000muM, the limit of detection equals 3.5x10(-6)Sm(-1)(0.2muM KCl), the detection repeatability, expressed in terms of the relative standard deviation, amounts to 1.13% and the detection volume is 0.6muL. The detector was applied to detection of ionic compounds, benzoic, lactic and octanesulfonic acids, and sodium capronate, after their separation by liquid chromatography in a Biospher PSI 100C 18 columns using a 60% aqueous acetonitrile mobile phase. The frequency characteristics of the detector are reasonably theoretically described on the basis of a simple model which is commonly used in the field of contactless impedance detectors.

The first experimental verification of electron Bernstein wave (EBW) collisional damping, and its mitigation by evaporated Li conditioning, in an overdense spherical-tokamak plasma has been observed in the National Spherical Torus Experiment (NSTX). Initial measurements of EBW emission, coupled from NSTX plasmas via double-mode conversion to O-mode waves, exhibited <10% transmission efficiencies. Simulations show 80% of the EBW energy is dissipated by collisions in the edge plasma. Li conditioning reduced the edge collision frequency by a factor of 3 and increased the fundamental EBW transmission to 60%.

National Spherical Torus Experiment (NSTX) is a spherical tokamak (ST) that operates with n(e) up to 10(20) m(-3) and B(T) less than 0.6 T, cutting off low harmonic electron cyclotron (EC) emission widely used for T(e) measurements on conventional aspect ratio tokamaks. The electron Bernstein wave (EBW) can propagate in ST plasmas and is emitted at EC harmonics. These properties suggest thermal EBW emission (EBE) may be used for local T(e) measurements in the ST. Practically, a robust T(e)(R,t) EBE diagnostic requires EBW transmission efficiencies of >90% for a wide range of plasma conditions. EBW emission and coupling physics were studied on NSTX with an obliquely viewing EBW to O-mode (B-X-O) diagnostic with two remotely steered antennas, coupled to absolutely calibrated radiometers. While T(e)(R,t) measurements with EBW emission on NSTX were possible, they were challenged by several issues. Rapid fluctuations in edge n(e) scale length resulted in >20% changes in the low harmonic B-X-O transmission efficiency. Also, B-X-O transmission efficiency during H modes was observed to decay by a factor of 5-10 to less than a few percent. The B-X-O transmission behavior during H modes was reproduced by EBE simulations that predict that EBW collisional damping can significantly reduce emission when T(e)<30 eV inside the B-X-O mode conversion (MC) layer. Initial edge lithium conditioning experiments during H modes have shown that evaporated lithium can increase T(e) inside the B-X-O MC layer, significantly increasing B-X-O transmission.

A novel, highly-accurate sample injection system for capillary electrophoresis (CE) was developed based on ink-jet microchip capable of reproducing exact introduction volumes at the picoliter level. The difficulty in analyte discrimination using electrokinetic injection was also overcome using this injection method. The injection system consisted of an XY stage, an ink-jet droplet ejection microchip, and a reservoir with a plug-in septum. To evaluate the precision of the system, a mixture of NBD-labeled amino acids consisting of Gly, L-Phe, L-Asp, and L-Ser were separated, and the performance was compared with that of traditional hydrodynamic and electrokinetic injection methods. The results demonstrated the introduced volume was highly relied on the number of droplets with low relative standard derivation (RSD) and good linear correction coefficient in the proposed injection method. In addition, a urine sample was analyzed via CE coupled with the ink-jet injection system for the detection of the amino acid taurine. The concentration of urinary taurine was determined to be 2.42 ± 0.08 μM (confidence level, 95%; RSD, 1.05%; n = 4) with a recovery of 98.92-109.54%(n = 3). These results demonstrate the ink-jet injection system we developed has the potential to revolutionize capillary electrophoretic separation in practical and commercial applications that require an automated accurate injection system.

A novel electrophoretic method for sensitive determination of nine aldehydes, including formaldehyde (C1), acetaldehyde (C2), propanal (C3), butanal (C4), pentanal (C5), hexanal (C6), glutaradehyde (Gla), 2,3-butanedione (Bud) and methylgloxal (MGo) in food samples, has been developed based on CE with amperometric detection (CE-AD). After being derivatized with an electroactive compound, 2-thiobarbituric acid (TBA), these nine non-electroactive aldehydes were converted to electroactive adducts, and therefore detectable by CE-AD approach. Experimental conditions of derivatization and CE-AD detection were optimized. The proposed method was validated according to International Conference on Harmonization (ICH) requirements, with recovery results ranging from 82.8 to 123.8%. Calibration plots of aliphatic aldehydes were linear (r² ≥ 0.9901) in the concentration range from 0.083 to 15.0 mg/L. The LODs were between 0.008 and 0.074 mg/L. The proposed CE-AD method provides a reliable and sensitive quantitative evaluation for non-electroactive low-molecular-mass monoaldehydes and dialdehydes in real sample matrices by employing relatively simple and inexpensive instrument.

The dissociation constants of epiboxidine 2 and a series of bases active at neuronal nicotinic acetylcholine receptors were determined by means of potentiometric and electrophoretic methods, which gave values in good agreement. Although showing different features, the two techniques are complementary for dissociation constant determinations. The choice of the most suitable method is guided by the available amount of sample, its purity, and the time needed for the analysis. The experimental values were compared with the predictions obtained with ACD/pK(a) DB software.

We have developed a gas chromatography-mass spectrometry method to measure five phthalates (dibutyl phthalate, butylbenzyl phthalate, di-2-ethylhexyl phthalate, diisooctyl phthalate, and diisononyl phthalate) in diets and beddings for experimental animals. The recoveries from diets and beddings spiked with five phthalates were 98.8%-148% with coefficients of variation of 0.4%-7.8% for diets and 94.7%-146% with coefficients of variation of 1.0%-5.0% for beddings. We analyzed commercial animal diets and beddings, and found that the levels of phthalates varied from sample to sample; the concentrations of five phthalates were 141-1,410 ng/g for diets and 20.5-7,560 ng/g for beddings.

A thermal desorption (TD)-GC/MS method was applied for the determination of phthalates in plastic children's toys. The method, which does not need any cumbersome sample pretreatment such as solvent extraction, filtration and derivatization, has been proved to be useful not only as a sensitive analytical method to evaluate phthalate concentration in the toys, but also as a rapid and practical screening method to check whether the concentration exceeds the regulatory limit.

In this study, diisodecyl phthalate (DIDP) was efficiently degraded by Bacillus sp. SB-007. The optimal conditions for DIDP (100 mg l(-1)) degradation by Bacillus sp. SB-007 in a mineral salts medium were found to be pH 7.0 at 30 degrees C, stirring at 200 rpm. The specific rate of DIDP degradation was found to be concentration dependent with a maximum of 4.87 mg DIDP l(-1) h(-1). DIDP was transformed rapidly by Bacillus sp. SB-007 with the formation of monoisodecyl phthalate and phthalic acid, which subsequently degraded further. These results highlight the potential of this bacterium for removing DIDP contaminated waste in the environment.

A pH-responsive Pickering emulsion has been designed on the basis of commercially available alumina-coated silica nanoparticles (Ludox CL silica particles) and potassium hydrogen phthalate (KHP). KHP was found to bind to cationic particle surfaces at pH values between 3.5 and 5.5, enabling the resulting surface-active particles to stabilize emulsions of xylenes in water. Above and below this pH range, the system demulsifies, resulting in a reversible Pickering emulsifier having two pH-controlled, reversible transitions.

A simple and sensitive capillary electrophoretic method was developed for the separation and determination of Ziram and Zineb in boric acid buffer by direct UV absorbance detection at lambda=254 nm. The separation is dependent on pH and nature of the buffer. The detection limits (S/N=3) are 1.88x10(-6) mol/l (0.57 mug/ml) and 2.48x10(-6) mol/l (0.68 mug/ml) for Ziram and Zineb, respectively. The method was successfully applied to the analysis of wheat samples spiked with Ziram and Zineb.

A wet chemical method for the estimation of carbon in uranium carbides has been developed, based on oxidation with a saturated solution of sodium dichromate in 9M sulphuric acid, absorption of the evolved carbon dioxide in a known excess of barium hydroxide solution, and titration of the excess of barium hydroxide with standard potassium hydrogen phthalate solution. The carbon content obtained is in good agreement with that obtained by combustion and titration.

A vitreous carbon anode has been used as working electrode in the coulometric titration of potassium hydrogen phthalate in glacial acetic acid-acetic anhydride medium with protous generated electrochemical oxidation of quinol.