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ABSTRACT: A rapid on-site air sampling technique was developed with a miniaturized needle-type sample preparation device for a systematic evaluation of the indoor air environments in school facilities. With the in-needle extraction device packed with a polymer particle of divinylbenzene and activated carbon particles, various types of volatile organic compounds (VOCs) were successfully extracted. For evaluating the indoor air qualities in school facilities, air samples in renovated rooms using organic solvent as a thinner of the paint were analyzed along with measurements of several VOCs in indoor air samples taken in newly built primary schools mainly using low-VOCs materials. After periodical renovation/maintenance, the time-variation profile of typical VOCs found in the school facilities has also been monitored. From the results, it could be observed that the VOCs in most of the rooms in these primary schools were at a quite low level; however, a relatively higher concentration of VOCs was found in some specially designed rooms, such as music rooms. In addition, some non-regulated compounds, including benzyl alcohol and branched alkanes, were detected in these primary schools. The results showed a good applicability of the needle device to indoor air analysis in schools, suggesting a wide range of future employment of the needle device, especially for indoor air analysis in other types of facilities and rooms including hospitals and hotels.
Analytical Sciences 01/2013; 29(5):519-25. · 1.25 Impact Factor
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ABSTRACT: A novel needle-type sample preparation device was developed for the effective preconcentration of volatile organic compounds (VOCs) in indoor air before gas chromatography-mass spectrometry (GC-MS) analysis. To develop a device for extracting a wide range of VOCs typically found in indoor air, several types of particulate sorbents were tested as the extraction medium in the needle-type extraction device. To determine the content of these VOCs, air samples were collected for 30min with the packed sorbent(s) in the extraction needle, and the extracted VOCs were thermally desorbed in a GC injection port by the direct insertion of the needle. A double-bed sorbent consisting of a needle packed with divinylbenzene and activated carbon particles exhibited excellent extraction and desorption performance and adequate extraction capacity for all the investigated VOCs. The results also clearly demonstrated that the proposed sample preparation method is a more rapid, simpler extraction/desorption technique than traditional sample preparation methods.
Analytica chimica acta 10/2012; 746:77-83. · 4.31 Impact Factor
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ABSTRACT: Retention prediction models for a group of pyrazines chromatographed under reversed-phase mode were developed using multiple
linear regression (MLR) and artificial neural networks (ANNs). Using MLR, the retention of the analytes were satisfactorily
described by a two-predictor model based on the logarithm of the partition coefficient of the analytes (log P) and the percentage of the organic modifier in the mobile phase (ACN or MeOH). ANN prediction models were also derived using
the predictors derived from MLR as inputs and log k as outputs. The best network architecture was found to be 2-2-1 for both ACN and MeOH data sets. The optimized ANNs showed
better predictive properties than the MLR models especially for the ACN data set. In the case of the MeOH data set, the MLR
and ANN models have comparable predictive performance.
Chromatographia 04/2012; 70(5):677-684. · 1.20 Impact Factor
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ABSTRACT: A fiber-packed needle extraction device was used as a novel method for the extraction of bisphenol A from water samples. A
bundle of filaments having a coating of polydimethylsiloxane was packed longitudinally into the needle. Good extraction efficiency
was obtained even for an extraction time of 10min, when the water sample was pumped through the needle with a syringe pump.
The needle could be used repeatedly. The preparation procedure, included a derivatization process. Under optimum conditions,
use of the fiber-packed needle showed a higher extraction efficiency than conventional sample preparation methods such as
liquid–liquid extraction and solid-phase extraction.
Chromatographia 04/2012; 69(7):685-690. · 1.20 Impact Factor
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ABSTRACT: By introducing sequentially connected two packed-capillary columns, a wide range of volatile compounds were successfully separated in gas chromatography. The hyphenation of two packed-capillary columns of 1.0 mm i.d. was accomplished using a conventional 6-port valve, where the temperature of each column was individually controlled in the respective column ovens. These columns were prepared with two different types of sorbents, each having a different selectivity, in order to separate a wide range of compounds, including permanent gases, volatile alcohols and other typical volatile organic compounds. With a simple valve switching operation, the complex sample mixtures were rapidly separated and detected.
Analytical Sciences 01/2012; 28(10):953-7. · 1.25 Impact Factor
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ABSTRACT: Retention behaviors of pyrazine and alkylpyrazines on various stationary phases in reversed-phase liquid chromatography were examined. An abnormal temperature effect on the retention of alkylpyrazines with a mobile phase consisting of acetonitrile and water was observed when changing the column temperature. On the other hand, no similar trend was found with a methanol-water mobile phase. For all the columns investigated in this work, the above tendency to the temperature-dependence was consistently observed, suggesting that the abnormal temperature effect on the retention of alkylpyrazines could be mainly induced by an acetonitrile-based mobile phase.
Analytical Sciences 01/2011; 27(12):1257-60. · 1.25 Impact Factor
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ABSTRACT: Novel polymer-coated fiber-packed microcolumns in liquid chromatography (LC) have been developed. Typical polymeric materials, such as polydimethylsiloxane and polyethyleneglycol, which are conventional stationary phases of capillary columns in gas chromatography (GC), have been employed as coating materials onto the surface of fine filaments. Packed longitudinally with a bundle of polymer-coated filaments into a stainless-steel capillary of 0.8 mm i.d., 150 mm length, several types of polymer-coated fiber-packed columns were prepared, and the retention behavior of aromatic compounds on these columns has been studied. A good linear relationship was obtained for van't Hoff plots over the temperature range between 0 and 200 °C, clearly indicating an excellent heat-resistant property of these polymer-coated fibrous stationary phases. Taking advantage of the heat-resistant feature of the fibrous stationary phases, the separation of several test mixtures with temperature-programmed elution was studied, where a solvent gradient program was additionally introduced if needed. Separation was also carried out with pure water as the mobile phase using an appropriate temperature program.
Analytical Sciences 01/2011; 27(8):811-6. · 1.25 Impact Factor
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ABSTRACT: Surface derivatization of Kevlar, poly(p-phenylene terephthalamide), fiber has been studied along with the evaluation of the surface characteristics of the chemically-modified fiber as the stationary phase in packed-capillary gas chromatography (GC). Several experimental parameters in the derivatization reaction have been optimized, and the retention behavior of the surface-derivatized fibrous stationary phase has been investigated using various standard solutes, such as alkanes, alcohols and alkylbenzenes. By introducing aminoethyl functional groups onto the surface of the fibrous material, a specific selectivity for polar solutes has been observed.
Analytical Sciences 01/2010; 26(9):1011-4. · 1.25 Impact Factor
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ABSTRACT: Third-hand smoking was quantitatively evaluated with a polymer-packed sample preparation needle and subsequent gas chromatography-mass spectroscopy analysis. The extraction needle was prepared with polymeric particles as the extraction medium, and successful extraction of typical gaseous volatile organic compounds (VOCs) was accomplished with the extraction needle. For an evaluation of this new cigarette hazard, several types of clothing fabrics were exposed to sidestream smoke, and the smoking-related VOCs evaporated from the fabrics to the environmental air were preconcentrated with the extraction needle. Smoking-related VOCs in smokers' breath were also measured using the extraction needle, and the effect of the breath VOCs on third-hand smoking pollution was evaluated. The results demonstrated that a trace amount of smoking-related VOCs was successfully determined by the proposed method. The adsorption and desorption behaviors of smoking-related VOCs were clearly different for each fabric material, and the time variations of these VOCs concentrations were quantitatively evaluated. The VOCs in the smokers' breath were clearly higher than that of nonsmokers'; however, the results suggested that no significant effect of the smokers' breath on the potential pollution occurred in the typical life space. The method was further applied to the determination of the actual third-hand smoking pollution in an automobile, and a future possibility of the proposed method to the analysis of trace amounts of VOCs in environmental air samples was suggested.
Analytical Sciences 01/2010; 26(5):569-74. · 1.25 Impact Factor
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ABSTRACT: Novel packed-capillary columns for gas chromatography were developed with a thin-wall stainless-steel capillary of 1.0 mm i.d.; and rapid temperature-programmed separations have been carried out after a basic evaluation concerning the compatibility of these columns to the temperature program. With a numerical integration method, the retention of several test analytes during temperature-programmed elution was successfully estimated. In order to confirm the suitability of the packed-capillary columns to relatively fast temperature programming up to 40 degrees C/min, theoretically predicted retention data were compared with that actually measured. The results suggested a good separation performance of the newly developed packed-capillary columns as a particle-packed column conventionally used. Also, the compatibility to a rapid temperature-programmed operation was quite satisfactory for almost all of the separations currently done in typical analytical laboratories.
Analytical Sciences 01/2010; 26(6):687-91. · 1.25 Impact Factor
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ABSTRACT: A novel fire investigation technique using a needle extraction device was studied. Using a polymer particle-packed needle device, air samples containing volatile organic compounds (VOCs) generated from fire accelerants, gasoline and kerosene were extracted effectively, and subsequent gas chromatographic (GC) analyses were successfully carried out. Carpet and wood samples were spiked with gasoline and kerosene, followed by monitoring of the time-variation profiles of emitted VOCs up to 48 h. The fire accelerants were also measured for combusted carpet and wood samples, and the applicability of the proposed method to fire investigations was confirmed. Even at 48 h after spiking, groups of characteristic compounds were clearly observed in the air environments near the combusted sample. This method was further applied to the determination of VOCs in simulated fires, strongly suggesting the applicability of the developed method to real fire investigations.
Analytical Sciences 01/2010; 26(11):1127-32. · 1.25 Impact Factor
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ABSTRACT: A new approach to the determination of human breath acetone with particle-packed sample preparation needle was developed. The extraction needle was packed with a copolymer of methacrylic acid and ethylene glycol dimethacrylate as the extraction medium. For the analysis of breath sample, exhaled breath was collected in a sampling bag, and 50 mL of the breath sample was extracted with the needle-type sample preparation device followed by analysis using gas chromatography-mass spectrometry (GC-MS). After the optimization of several basic extraction conditions for standard acetone samples, breath acetone concentration taken from controlled type-2 diabetic patients was determined. Furthermore, time variations of breath and urine acetone of four healthy individuals under fasting conditions were measured. Urine sample was collected in glass vial, and urine acetone concentration was also determined with the extraction needle by analyzing the corresponding headspace gas. The results demonstrated that the particle-packed extraction needle showed an excellent extraction performance for acetone in both breath and urine headspace samples, and that there is a clear correlation between the concentration of breath acetone and HbA1c level of controlled type-2 diabetic patients. The breath acetone level in controlled diabetic patients was in the range between 0.19 and 0.66 ppmv, where its concentration in medically untreated type-2 patient was 0.92 and 1.20 ppmv. The breath acetone concentration in healthy male was increased to 5.66 ppmv under the 24 h of fasting test, and a high correlation between the breath and urine acetone concentration was also observed. On the basis of the above results, the potential applications of the proposed method to the diagnosis of diabetes and/or ketoacidosis were suggested.
Journal of chromatography. B, Analytical technologies in the biomedical and life sciences 09/2009; 877(24):2551-6. · 2.78 Impact Factor
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Journal of Liquid Chromatography & Related Technologies 06/2009; 32(10):1407-1422. · 0.71 Impact Factor
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ABSTRACT: Fiber-packed sample preparation device was applied to the simultaneous derivatization/preconcentration of ethylene oxide (EO) in air samples. The polymer-coated filaments were packed longitudinally into the needle, and hydrogen bromide (HBr) was loaded onto the filaments in the preconditioning process. Simultaneous derivatization with HBr in the needle was made during the sampling process of the gaseous EO, and the corresponding derivatized analyte, 2-bromoethanol, was desorbed by passing a small amount of methanol through the extraction needle in the heated gas chromatograph (GC) injector. The basic extraction/desorption parameters for EO have been evaluated. The limit of detection (LOD), limit of quantification (LOQ) and the relative standard deviation (RSD) of run-to-run repeatability were 1.8 ng/L, 5.4 ng/L and less than 4%, respectively, with an extraction time of about 10 min. Satisfactory storage performance for three days at room temperature was also confirmed.
Journal of chromatography. A 12/2008; 1216(14):2848-53. · 4.19 Impact Factor
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ABSTRACT: Retention prediction models for reversed-phase liquid chromatography (RPLC) have been extensively studied owing to the fact that RPLC remains the most widely used chromatographic technique especially in the field of pharmaceutical and biomedical analyses. However, RPLC is not always the method of choice for the analysis of some compounds that have high polarity. Hydrophilic interaction chromatography (HILIC) has been gaining interest in the last few years as an alternative option to RPLC for the analysis of polar and hydrophilic analytes. HILIC is a variant of normal-phase liquid chromatography, but utilizes water in a water-miscible organic solvent as the eluent in conjunction with a hydrophilic stationary phase. The present review aims to summarize recent contributions on the development of retention prediction models for a group of basic analytes, namely, the adrenoreceptor agonists and antagonists, on different polar stationary phases. The use of multiple linear regression and artificial neural networks in model building is highlighted.
Analytical and Bioanalytical Chemistry 10/2008; 393(1):137-53. · 3.78 Impact Factor
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ABSTRACT: A miniaturized sample preparation technique that uses a fine-fiber-packed needle as the extraction medium is reviewed, especially in relation to its application to the analysis of volatile organic compounds by gas chromatography. When the needle was packed longitudinally with a bundle of fine filaments (12 microm o.d.) which were also surface-coated with polymeric materials, successful sample preconcentration was obtained. Improved sensitivity was also established by introducing simultaneous derivatization reactions into the extraction process in the fiber-packed needle. The storage performance of the needle clearly demonstrated the potential of the technique for typical on-site sampling during environmental analysis. In this short review, the fiber-packed extraction needle developed by the authors is summarized along with applications that use the fiber-packed needle as a miniaturized extraction device.
Analytical and Bioanalytical Chemistry 10/2008; 393(3):861-9. · 3.78 Impact Factor
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ABSTRACT: The effects of alcohol on the CE enantioseparation of selected basic drugs with gamma-CD as the chiral selector was investigated. The enantioseparation behavior of the analytes with gamma-CD in the absence and presence of different alcohols specifically methanol, ethanol, 2-propanol (IPA), and 2-methyl-2-propanol (TBA), the relationship of enantiomeric resolution (R(s)) values with either hydrophobicity or bulkiness of the alcohols, as well as the effect of these alcohols on interaction of the analytes with gamma-CD were studied. Results showed that hydrophobicity and/or bulkiness of alcohols have an influence on the enantioresolution of most of the analytes based on the relatively high correlation coefficients (R) obtained between R(s) versus log P and between R(s) versus ovality (i.e., parameter to indicate bulkiness of a molecule). Comparison of the values of the average binding constants obtained for each enantiomeric pair in the presence and absence of 5% IPA showed that alcohols can increase, decrease, or give a minimal effect on the analyte-gamma-CD interaction depending on the analyte. Furthermore, the significant enhancement in the enantioresolution of both propranolol and pindolol in the presence of either IPA or TBA led to the baseline enantioresolution of both drugs using 35 mM gamma-CD.
Journal of Separation Science 08/2008; 31(14):2701-6. · 2.73 Impact Factor
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ABSTRACT: The development of retention prediction models for the seven ginsenosides Rf, Rg1, Rd, Re, Rc, Rb2, and Rb1 on a polyamine-bonded stationary phase in hydrophilic interaction chromatography (HILIC) is presented. The models were derived using multiple linear regression (MLR) and artificial neural network (ANN) using the logarithm of the retention factor (log k) as the dependent variable for four temperature conditions (0, 10, 25, and 40 degrees C). Using stepwise MLR, the retention of the analytes in all the temperature conditions was satisfactorily described by a two-predictor model wherein the predictors were the percentage of ACN (%ACN) in the mobile phase and local dipole index (LDI) of the compounds. These predictors account for the contribution of the solute-related variable (LDI) and the influence of the mobile phase composition (%ACN) on the retention behavior of the ginsenosides. A comparison of the models derived from both MLR and ANN revealed that the trained ANNs showed better predictive abilities than the MLR models in all temperature conditions as demonstrated by their higher R(2) values for both training and test sets and lower average percentage deviation of the predicted log k from the observed log k of the test compounds. The ANN models also showed excellent performance when applied to the prediction of the seven ginsenosides in different sample matrices.
Journal of Separation Science 06/2008; 31(9):1550-63. · 2.73 Impact Factor
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ABSTRACT: Retention prediction models based on multiple linear regression (MLR) and artificial neural network (ANN) for adrenoreceptor agonists and antagonists chromatographed on a polyvinyl alcohol-bonded stationary phase under hydrophilic interaction chromatography were described. The models showed the combined effects of solute structure and mobile phase composition on the retention behavior of the analytes. Using stepwise MLR, the retentions of the studied compounds were satisfactorily described by a five-predictor model; the predictors being the %ACN, the logarithm of the partition coefficient (log D), the number of hydrogen bond donors (HBD), the desolvation energy for octanol (FOct), and the total absolute atomic charge (TAAC). The inclusion of the solute-related descriptors suggested that hydrophilic interactions such as hydrogen bonding and also ionic interactions are possible mechanisms by which analytes are retained on the studied system. ANN prediction models were also derived using the predictors derived from MLR as inputs and log k as outputs. The best network architectures were found to be 5-3-1 for the datasets at pH 3.0 and 4.0, and 5-4-1 for the dataset at pH 5.0. The optimized ANNs showed better predictive properties than the MLR models for both training and test sets under all pH conditions.
Journal of Separation Science 06/2008; 31(9):1537-49. · 2.73 Impact Factor
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ABSTRACT: The retention behavior of uric acid (UA) and methyl uric acids (MUAs) on a diol column in hydrophilic interaction chromatography
(HILIC) is presented. The effects of chromatographic parameters such as organic solvent content and salt concentration in
the mobile phase, and column temperature were systematically investigated using a design of experiment (DOE). The results
of the DOE revealed that the content of organic solvent, acetonitrile (ACN), had the most influence on the retention of the
analytes. The effect of salt concentration indicated the possibility of electrostatic repulsion between the negatively charged
analytes and the deprotonized residual silanol groups on the surface of the stationary phase. Van’t Hoff plots were constructed
to further study the effects of column temperature on the retention of the compounds on the diol phase. Nonlinear van’t Hoff
plots were observed for all the analytes in the studied temperature range (0–50°C) signifying that the retention of UAs and
MUAs on the diol column is governed by mixed retention mechanisms. Retention prediction models derived by multiple linear
regression (MLR) showed that the retention of the analytes is dependent on the percentage of ACN in the mobile phase and two
solute-related descriptors namely ovality (Ov) and the lowest unoccupied molecular orbital (LUMO). The incorporation of Ov,
a shape parameter, in the MLR equation signified the importance of the shape/size of the compounds on the observed retention
on the diol phase.
Chromatographia 03/2008; 67(7):507-515. · 1.20 Impact Factor
