bluuebunny/crossref_metadata_2025 huggingface dataset:
An automated enantioselective isolation system for the study of estrogenic potencies: Study of the estrogenic activity of α‐hexachlorocyclohexane
Authors: Hashimoto Shinya , Yoshimoto Takeshi , Nakao Masumi , Omura Hiroshi , Yamashita Nobuyoshi , Kannan Kurunthachalam , Giesy John P.
Published: July 2003

Herein we describe an automated enantioselective isolation system that uses a gas chromatograph‐flame ionization detector (FID)‐preparative fraction collector to separate the enantiomers of chiral compounds. In this system, a switching device was coupled with six glass tubes containing an organic solvent for the separate collection of six compounds, thus eliminating the need for a manual collection procedure after separation by gas chromatography. To evaluate the usefulness of this system, we applied it to the separation and collection of the enantiomers of α‐hexachlorocyclohexane (α‐HCH), and we measured the estrogenic potency of each enantiomer by means of an MVLN cell (Michigan Cancer Foundation‐7 (MCF‐7) cell stably transfected with a pVit‐tk‐LUC reporter plasmid) bioassay and an estrogen receptor binding assay. The variability in the retention time of each enantiomer (relative standard deviation, n = 16) was typically < 0.05%. The recoveries of the dextrorotatory (+) and levorotatory (–) enantiomers of α‐HCH were about 68.8% and 73.4%, respectively. The overall quantity of each enantiomer of α‐HCH collected was about 300 μg. Both enantiomers of α‐HCH showed similar estrogenic activity. On the basis of the results obtained for α‐HCH, we concluded that this analytical method is suitable for the determination of the estrogenic activity of other chiral compounds. Such determinations are essential because enantiomers differ considerably in how they accumulate in organisms and decompose in the environment.
Separation and determination of small amounts of sulfur in technical thiophanate‐methyl by reversed‐phase high‐performance liquid chromatography
Authors: Rao R. Nageswara , Venkateswarlu N. , Rao B. Vittal , Raju P. V. K. , Krishnaiah A.
Published: July 2003

A simple and rapid reversed phase high‐performance liquid chromatographic method for separation and determination of elemental sulfur in technical thiophanate‐methyl using a reversed‐phase C18 column and methanol‐water‐tetrahydrofuran (90 : 8 : 2 v/v/v) as eluent with UV detection at 254 nm has been developed and validated with respect to accuracy, precision, specificity, linearity range, and limits of detection and quantification. The method was found to be suitable not only for detection but also determination of elemental sulfur at levels of 5×10–9 g.
Polyethylene powder microcolumn for protein separation prior to HPLC plasma analysis. Application to the determination of copper and zinc
Authors: Mendonça Jean Karlo Acosta , Cícero do Nascimento Paulo , Bohrer Denise
Published: July 2003

Three different types of polyethylene powder (PE) were investigated with regard to their ability to adsorb proteins, with the goal of accomplishing plasma deproteinization for further HPLC analysis. Best results were obtained with ultrahigh molecular mass polyethylene The proteins retained by the PE powder were washed out of the column with methanol followed by water. A chromatographic system with the PE column as pre‐column was set up for the determination of copper and zinc in plasma. The plasma sample was injected into the chromatograph, and, on passage through the pre‐column, the proteins were adsorbed onto the PE. While a protein‐free eluate was being sent to the analytical column, by switching the pump channels the pre‐column was being flushed with methanol and water to elute the adsorbed proteins. After washing, the pre‐column was conditioned with the eluent to receive the next sample. Copper and zinc determination was performed by HPLC with photometric detection after post‐column derivatization with 4‐(2‐pyridylazo)resorcinol (PAR). The results, compared with those from flame atomic absorption spectrometry, showed that zinc can be determined by direct injection of the sample, but copper only after dilution. As the copper recovery from undiluted samples was about 65%, it was probably retained together with the proteins. However, on previous dilution of the sample with the eluent (acidic solution of lactic acid) the copper recovery reached 100%. The proposed method is suitable for the HPLC determination of copper and zinc in plasma samples without further sample treatment, in about 30 min.
Separation and microcolumn preconcentration of traces of rare earth elements on nanoscale TiO2 and their determination in geological samples by ICP‐AES
Authors: Hang Yiping , Qin Yongchao , Shen Jing
Published: July 2003

A simple, rapid microcolumn preconcentration and separation technique is described for the determination of the trace rare earth elements Sm, Tm, Ho, and Nd in geological samples by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP‐AES). The technique was based on adsorption of analytes on Nanometer‐Size Titanium Dioxide (NSTD) packed in a microcolumn and separation from the matrix at pH = 7.0. Quantitative adsorption of more than 94% of analytes was obtained in this work. The dynamic adsorption capacities of NSTD were found to be 14.59, 12.86, 14.38, and 15.58 mg g–1 for Tm, Sm, Ho, and Nd, respectively. The analytes were recovered quantitatively from NSTD with 2.0 mol L–1 HCl. The analytical procedure was optimized in terms of sample acidity, elution, flow rate of sampling, and sample volume. At a flow rate of 1.0 mL min–1, the detection limits (3σ) of the technique for Tm, Sm, Ho, and Nd with an enrichment factor of 50 were 0.06, 0.18, 0.08, and 0.1 ng mL–1, and the RSD were 1.8%, 4.7%, 2.0%, and 1.6%, respectively.
Analysis of aristolochic acids in herbal medicines by LC/UV and LC/MS
Authors: Lee Ming‐Chung , Tsao Chi‐Hsiang , Iou Song‐Chou , Chuang Wu‐Chang , Sheu Shuenn‐Jyi
Published: July 2003

Two high‐performance liquid chromatographic methods, one combined with a photodiode array detector (LC/UV) and another with mass spectrometry (LC/MS), were developed for the analysis of aristolochic acid I and II in herbal medicines. The LC/UV method was carried out using a Cosmosil 5C18‐MS column with a gradient solvent system composed of phosphate buffer‐acetonitrile and a UV detector (390 nm). The LC/MS method was performed using an acetate buffer‐acetonitrile solvent system and positive‐ion electrospray ionization MS. The characteristic fragment ions for aristolochic acid I were selected at m/z 359, m/z 324, m/z 298, and m/z 296, and for aristolochic acid II at m/z 329, m/z 294, and m/z 268. In order to attain better resolution, solid phase extraction was used to prepare the test solution in this study.
A new selective SPME fiber for some n‐alkanes and its use for headspace sampling of aqueous samples
Authors: Farajzadeh Mir Ali , Hatami Mehdi
Published: July 2003

This contribution presents a new porous solid phase microextraction (SPME) fiber based on cellulose acetate and polyvinyl chloride (PVC) coated on a metallic base. The proposed fiber is selective for n‐alkanes higher than C10, especially for C12–C15. PVC acts as a binder and surface modifier of the fiber. Fiber preparation can be completed in less than 15 min. High capacity, chemical, thermal, and mechanical durability, low cost, and no occurrence of additional peaks in chromatograms are further advantages of the proposed fiber. The relative standard deviations obtained from a single fiber are less than 9% for all analytes. The fiber‐to‐fiber reproducibility is better than 18%. After optimizing experimental conditions such as fiber composition, extraction time, desorption temperature, solution volume, salting out effect, etc. the fiber can be used for sampling from the headspace of aqueous solutions containing n‐alkanes (C10–C20) in the μg/L concentration range. Detection limits of 50–150 μg/L are obtained on use of capillary gas chromatographic separation and flame ionization detection. The microextraction procedure is rapid and equilibration takes less than 20 min.
Quantitative structure‐retention relationships in reversed‐phase liquid chromatography using several stationary and mobile phases
Authors: Vonk Erik C. , Lewandowska Katarzyna , Claessens Henk A. , Kaliszan Roman , Cramers Carel A.
Published: July 2003

Quantitative Structure‐Retention Relationships (QSRRs) have been employed to study retention mechanism of Reversed‐Phase Liquid Chromatography (RPLC). Two C18 and two C8 columns were used with mobile phases containing methanol, acetonitrile, and tetrahydrofuran in concentrations ranging from 40 to 90 (v/v)% in water. QSRR equations derived are generally characterized by a satisfactory quality of fit, although missing data or a low average retention can decrease the goodness‐of‐fit. In agreement with literature the most important retention descriptors appeared to be the analyte's molecular volume and its hydrogen‐bond accepting basicity, but also the polarity/polarizability, hydrogen‐bond donating acidity, and excess molar refraction showed statistical significance in several cases. Relatively small, but significant differences between the two C18 stationary phases were observed. The differences between C8 and C18 column types were more pronounced. The influence of the mobile phase on regression coefficients is more difficult to interpret, because of adsorption of mobile phase constituents by the stationary phase. However, the importance of this partitioning of water and modifier is illustrated by the practically identical trends in b values for the three modifiers studied, while the trends in v values are significantly different. Principal component analysis of the QSRR regression coefficients demonstrated the prevailing role of the mobile phase for chromatographic properties of the RPLC systems studied as compared to the stationary phase.
Investigation of factors influencing the performance of open‐tubular stationary phases in capillary electrochromatography
Authors: Freitag Ruth , Constantin Stéphane
Published: July 2003

Silica‐based, open‐tubular capillary columns bearing C8‐moieties were produced by the sol gel approach. The influence of experimental conditions adjusted during the preparation of the stationary phase on the performance of the resulting capillary column were investigated in terms of the plate height, the resolution, and the capacity factors, taking the separation of three non‐charged polyaromatic hydrocarbons (naphthalene, phenanthrene, pyrene) as example. Acetone served as EOF marker. The optimal synthesis protocol was then used to prepare columns for an analogous investigation of the chromatographic parameters, namely the mobile phase composition, the applied voltage and temperature, as well as the column length, thickness, and inner diameter on the performance of the capillary columns.
Fast comprehensive two‐dimensional gas chromatography (GC×GC) using 50‐μm ID second‐dimension columns
Authors: Adahchour Mohamed , Tas̨öz Ayla , Beens Jan , Vreuls René J. J. , Batenburg A. Max , Brinkman Udo A. Th.
Published: July 2003

Up till now, comprehensive two‐dimensional gas chromatography has suffered from the serious disadvantage that the first‐dimension separation has to be operated both at sub‐optimum flow and at slow temperature programming rates to enable the required number of modulations across a first‐dimension peak. Consequently, the separation efficiency of the first‐dimension is (far) below optimum and the overall analysis times become longer than necessary. This problem can be solved by selecting a short 50‐μm ID second‐dimension column, and combining it with a standard long 250‐μm ID first‐dimension column. Compared with conventional GC×GC set‐ups, an over 3‐fold reduction of the analysis time was reached in the present study without sacrificing resolution; to the contrary, a substantial increase of the peak capacity was obtained.
Determination of drugs used in advanced breast cancer by capillary gas chromatography of pharmaceutical formulations
Authors: Berzas Juan J. , Rodríguez Juana , Contento Ana M. , Cabello Maria P.
Published: July 2003

A capillary gas chromatographic method with flame ionisation detection (FID) has been developed for the analysis of Tamoxifen, Anastrozole, and Letrozole in their pharmaceutical preparations, using Clomipramine as the internal standard in order to achieve quantification. Optimal conditions were investigated: column head pressure (110 kPa), injector and detector (FID) temperatures (both 325°C), time and temperature for the splitless step (0.75 min and 70°C), volume injected (2 μL), and an oven temperature program providing analysis times shorter than 8 minutes. The principal aspects of the validation method are examined and discussed. A test of the ruggedness of this method was carried out using the Plackett‐Burman fractional factorial model with a matrix of fifteen experiments. Detection limits of 17.0, 9.6, and 30.6 μg L–1 were obtained for Tamoxifen, Anastrozole, and Letrozole, respectively. This method is simple, rapid, and sensitive; it was tested on the analysis of pharmaceutical preparations, achieving recoveries between 98.8% and 100.3%.
Highly efficient separation of dsDNA fragments on glass chips by using an ultralow viscosity sieving matrix
Authors: Wang Hui , Qin Jianhua , Dai Zhongpeng , Wang Li , Bai Jiling , Lin Bingcheng
Published: July 2003

A novel protocol has been established to separate dsDNA fragments with high efficiency on glass chips by using an ultralow viscosity sieving matrix with added glucose. Low‐molecular‐weight hydroxypropylmethylcellulose (HPMC), with a viscosity nearly equivalent to that of water, was used to electrophoretically separate fluorescent intercalator‐labeled double‐stranded DNA (dsDNA) fragments on microfluidic glass chips. In comparison with conventional sieving protocols, low‐molecular‐weight HPMC as sieving matrix could result in reduced running cost and analysis time, in addition to a comparable separation efficiency of dsDNA fragments. In this paper, the addition of glucose was investigated to enhance the separation of DNA in the lowest viscosity polymer evaluated. The effect of staining dye and field strength were also evaluated. At an applied electric field strength of 200 V/cm, satisfactory resolution of the PBR322/HaeIII DNA marker could be achieved within 4 min by using 2% HPMC‐5 with 6% glucose added. Coelectrophoresing PCR product along with ϕX174/HaeIII DNA sizing marker was also demonstrated by using the ultralow viscosity HPMC‐5 solution on a glass chip.
LC method for the simultaneous determination of R‐timolol and other closely related impurities in S‐timolol maleate: Optimization by use of an experimental design
Authors: Djang'eing'a Marini Roland , Chiap Patrice , Boulanger Bruno , Dewe Walthère , Hubert Philippe , Crommen Jacques
Published: July 2003

A liquid chromatography (LC) method using cellulose tris(3,5‐dimethylphenylcarbamate) (5 μm) as chiral stationary phase (CSP) and a mixture of hexane, 2‐propanol, and diethylamine as mobile phase was developed for the simultaneous determination of R‐timolol and other potential related substances in S‐timolol maleate samples. An experimental design was elaborated in order to test the effects of the different selected factors. Three factors were studied simultaneously, namely the concentrations of 2‐propanol and diethylamine as well as the column temperature. The effects of these factors were evaluated statistically. Optimal LC conditions were then deduced by applying a multicriteria decision making approach, namely Derringer's desirability function, for the responses of interest. The developed LC method was compared to the European Pharmacopoeia method and was applied to the determination of R‐timolol and other related substances in several samples of S‐timolol maleate from different sources.
High performance centrifugal partition chromatographic separation of alkaline earth metal ions with bis‐2‐ethylhexylphosphinic acid
Authors: Nagaosa Yukio , Wang Tao
Published: July 2003

The mutual separation of Ca(II), Mg(II), Sr(II), and Ba(II) was studied by high performance centrifugal partition chromatography using 0.16 M bis‐2‐ethylhexylphosphinic acid in heptane as a stationary phase. Two‐step elution of the four metal ions loaded was accomplished with aqueous chloroacetic acid mobile phases (pH 6.50 and 5.30). Ethanol (5%) was added to the pH 6.50 mobile phase for the separation of Sr(II) and Ba(II). The chromatographic conditions were 2,136 partition channels, 800 rpm rotational speed, and 1.5 cm3/min flow rate. The elution curve was obtained by monitoring the absorbance of each metal complex post‐labeled with a chromogenetic agent.
Cyclodextrin derivatives in GC separation of racemates with different volatilities. Part XIX: Thermodynamic aspects of enantioselective GC separation of some volatiles with γ‐cyclodextrins 2,3‐substituted with methyl and acetyl groups
Authors: Bicchi Carlo , Brunelli Claudio , Cravotto Giancarlo , Rubiolo Patrizia , Galli Mario , Mendicuti Francisco
Published: July 2003

The thermodynamic parameters involved in the enantiomer separation of two homologous series of γ‐lactones (C6–C8 and C10–C12) and a group of structurally related monoterpenoids with a p‐menthane skeleton (menthol, i‐menthol, neo‐menthol, neo‐i‐menthol, menthone, i‐menthone, and 3‐oxo‐1,8‐cineole) are determined to investigate how inverted substitution in positions 2 and 3 of the cyclodextrin ring with methyl and acetyl groups influences the enantioselectivity of 2‐O‐methyl‐3‐O‐acetyl‐6‐O‐t‐hexyldimethylsilyl‐γ‐cyclodextrin and 2‐O‐acetyl‐3‐O‐methyl‐6‐O‐t‐hexyl‐dimethylsilyl‐γ‐cyclodextrin. The thermodynamic results show that the methyl and acyl groups, in positions 2 and 3 respectively, act complementarily to increase enantioselectivity and that the relative configuration of the stereogenic centres in the selectands influences enantiomer separation.
Extraction of polycyclic aromatic hydrocarbons and organochlorine compounds from water: A comparison between solid‐phase microextraction and stir bar sorptive extraction
Authors: Popp Peter , Bauer Coretta , Hauser Barbara , Keil Petra , Wennrich Luise
Published: July 2003

The enrichment of semi‐volatile compounds from water using solid‐phase microextraction (SPME) and stir bar sorptive extraction (SBSE) was compared. The investigations (analysis of PAHs and organochlorine compounds) were performed to compare SPME‐GC/MS and SBSE‐thermodesorption‐GC/MS. Additionally, SPME fibres and stir bars were desorbed in a small volume of solvent and analysed by HPLC with fluorescence detection. This method was applied to PAHs. SBSE is more robust and under the given conditions (extraction from a 10 mL sample, 1 h exposure time of fibres and stir bars) enables higher recoveries (20.1–97.2%) for the compounds investigated than SPME (recoveries of 6.3–51.6%). Detection limits between 0.1 and 4.5 ng/L were calculated for the SPME‐GC/MS combination, whereas the SBSE‐GC/MS combination enabled detection limits between 0.05 and 1.0 ng/L. Coupled to HPLC, the detection limits of the PAHs investigated were found to range between 1.0 and 10.0 ng/L (SPME) or between 0.3 and 2.0 ng/L (SBSE). The advantage of SPME is that the procedure can be completely automated, which is not possible when combining SBSE with GC or LC.
Capillary zone electrophoresis of phenol and methylphenols at high pH in methanol
Authors: Porras Simo P. , Kuldvee Ruth , Jussila Matti , Palonen Sami , Riekkola Marja‐Liisa
Published: July 2003

Capillary zone electrophoresis of phenol and its three methyl‐substituted derivatives (cresols) was investigated in water and methanol as solvents for the electrolyte. In water the acid strengths of o‐cresol and p‐cresol are too similar to allow their capillary zone electrophoretic separation. In pure methanol the differences in acid strength are amplified and all three cresols and phenol were clearly separated with use of pH 13–14 buffers prepared from maleic acid. The dependence of electrophoretic mobilities on pH in MeOH was investigated, and a slight difference was observed between theoretically calculated mobilities and measured mobilities. Maleate background electrolytes provided highly repeatable separations of the analytes. High pH medium in methanol appears to be a good choice for capillary zone electrophoretic separation of weak acids with similar acidity in water. The effective separation of 2,4‐xylenol and 2,6‐xylenol was also demonstrated.
High performance liquid chromatography determination of 4‐nonylphenol, 4‐tert‐octylphenol, and their short ethoxyl chain polyethoxylates in water samples using a microporous membrane liquid‐liquid extraction sample pretreatment technique
Authors: Liu Jing‐fu , Liang Xia , Jiang Gui‐bin , Cai Ya‐qi , Zhou Qing‐xiang , Liu Guo‐guang
Published: July 2003

Microporous membrane liquid‐liquid extraction (MMLLE) sample pretreatment, coupled with reversed‐phase high performance liquid chromatography with fluorescence detection (HPLC‐FLD) was proposed for the determination of alkylphenols (APs), including 4‐nonylphenol (4‐NP) and 4‐tert‐octylphenol (4‐t‐OP), and their short ethoxyl chain polyethoxylates (SEC‐APEOs) in environmental aqueous samples. After MMLLE, 4‐NP, 4‐t‐OP, and SEC‐APEOs were trapped in hexane used as acceptor. The hexane with enriched analytes was purged to dryness with nitrogen gas. Methanol (0.6 mL) and then water (1.4 mL) were added to dissolve the residue and the analytes were subsequently focused onto a C18 precolumn prior to injection onto the analytical column for separation and detection by reversed‐phase HPLC‐FLD. The proposed procedure permits convenient determination of APs and SEC‐APEOs, which have similar endocrine activity and appear as a single peak in reversed‐phase HPLC. The detection limits for 4‐NP and 4‐t‐OP were 0.1 and 0.05 μg/L, respectively. Four samples including tap water, river water, and effluent from a sewage treatment works water were analyzed by the proposed method and the recoveries at 0.5 μg/L spiked level were in the range of 74–110%.
Separation of diastereomers of flavanone‐7‐O‐glycosides by capillary electrophoresis using sulfobutyl ether‐β‐cyclodextrin as the selector
Authors: Aturki Zeineb , Sinibaldi Massimo
Published: July 2003

A method was developed for the separation of diastereomers of flavanone‐7‐O‐glycosides by capillary electrophoresis using sulfobutyl ether‐β‐cyclodextrin (SBE‐β‐CD) in the background electrolyte. The effect of the concentration of the CD additive, buffer pH, and organic modifier on the migration times and resolution for five flavanone glycosides (naringin, hesperidin, neohesperidin, narirutin, and eriocitrin) was studied. Baseline separations of these compounds as pairs of diastereoisomers were achieved with 20 mM tetraborate buffer at pH 7 containing 5 mg/mL of SBE‐β‐CD and 10% (v/v) of methanol. The developed method was used for the qualitative analysis of the diastereomeric composition of the major flavanone glycosides in different citrus juices. The ability of SBE‐β‐CD to discriminate flavanone enantiomers was also investigated.
Factors affecting microporous membrane liquid‐liquid extraction
Authors: Kuosmanen Kati , Lehmusjärvi Marja , Hyötyläinen Tuulia , Jussila Matti , Riekkola Marja‐Liisa
Published: July 2003

The effect of different factors on the extraction yield in microporous membrane liquid‐liquid extraction (MMLLE) was studied in this work. The factors were the extraction temperature, mixing of the donor and acceptor solvents, state of the acceptor (stagnant or flowing), solvent set‐up in the membrane unit (organic phase on top or bottom), adsorption of the analytes into the membrane material, and the membrane pore size. The effect of temperature, as it was mediated through the other factors, was of particular interest. Increase in the extraction temperature improved the extraction yields substantially: for naphthalene the extraction yield increased from 14.3% to 17.7% and for benz[a]anthracene from 0.4% to 11.1% when the temperature was raised from 20°C to 80°C. The diffusion coefficients, which were determined with a chromatographic band broadening method, were also clearly increased with temperature: the average diffusion coefficient obtained for naphthalene in water at ambient temperature was 7.92×10–10 m2/s, while at 70°C it was 2.19×10–9 m2/s. The most vigorous mixing of the solvents was obtained with counter‐currently flowing acceptor phase and water on top in the membrane block. The adsorption to the membrane material compared with theoretical 100% extraction yield ranged from 0.5 to 5.4% at 80°C when no acceptor phase was present.
Determination of organophosphate ester plasticisers in blood donor plasma using a new stir‐bar assisted microporous membrane liquid‐liquid extractor
Authors: Jonsson Ove B. , Nilsson Ulrika L.
Published: July 2003

A new stir‐bar assisted microporous membrane liquid‐liquid extractor (MMLLE) was used for clean‐up of organophosphate esters in blood plasma. The plasma sample was stirred on one side of a planar membrane while the receiving organic phase was continuously pumped on the other side. Recoveries for eight different organophosphate esters were between 30 and 89% and relative standard deviations between 1.2 and 15%. The method limits of detection, when extracting 5 g plasma and analysing the extract with gas chromatography and nitrogen phosphorus detector, were between 0.2 and 0.9 ng g–1 plasma at S/N = 3. The extraction efficiency in terms of analyte mass transfer per time unit through the membrane was shown to be much higher for stir‐bar assisted MMLLE compared to the more commonly used flow‐cell type of membrane extractor. Blood donor plasma collected with three different types of whole blood collection bag system was analysed with respect to organophosphate ester plasticisers. In plasma from one type of bag system, triphenyl phosphate (TPhP) and 2‐ethylhexyl diphenyl phosphate (EHDPP) were detected at concentrations of 0.053–0.13 μg g–1 and 0.73–1.2 μg g–1 plasma, respectively. The main source of the organophosphate esters was found to be the whole blood collection bag system, with some parts containing EHDPP at concentrations of approximately 60 μg g–1. In plasma collected with the other two types of bag systems, no detectable levels of organophosphate esters were found.
Capillary gas chromatographic determination of Tamoxifen in the presence of a number of antidepressants in urine
Authors: Rodríguez Juana , Berzas Juan J. , Contento Ana M. , Cabello Maria P.
Published: July 2003

A capillary gas chromatographic method with flame ionisation detection is described for the determination of Tamoxifen in association with the antidepressants Fluoxetine, Fluvoxamine, and Clomipramine, using Anastrozole as the internal standard. Optimal conditions were investigated: column head pressure (110 kPa), injector and detector temperature (230°C and 250°C, respectively), time and temperature of the splitless step (1.25 min and 80°C), injected volume (2 μL), and oven temperature programme. This provided analysis times of under 11 minutes. Good results were obtained for different aspects including stability of the solutions, linearity, accuracy, and precision. Detection limits between 2.4 and 12 μg L–1 were obtained for all the studied compounds. A ruggedness test of the method was carried out using the Plackett‐Burman fractional factorial model with a matrix of fifteen experiments. The method which has been developed is easy, rapid and sensitive and has been used to determine Tamoxifen, Fluoxetine, Fluvoxamine, and Clomipramine present at clinically relevant levels in urine. Before GC‐FID determination, it was necessary to apply a simple extraction preconcentration step to the urine using a C18 cartridge with methanol as eluent.
Determination of prednisolone, naphazoline, and phenylephrine in local pharmaceutical preparations by micellar electrokinetic chromatography
Authors: Gallego José María Lemus , Pérez Arroyo Julián
Published: July 2003

A new, rapid, and simple method is described and used to resolve and quantify mixtures of prednisolone, naphazoline, and phenylephrine. The determination was accomplished by micellar electrokinetic chromatography (MEKC) using a fused‐silica capillary (57 cm×75 μm ID). The separation was carried out at 25°C and 30 kV, using a 5 mM phosphate‐5 mM borate buffer adjusted to pH = 8.2, 40 mM sodium dodecylsulfate (SDS) as background electrolyte. Under these conditions, the run time was 6.6 min and the limits of quantification were about 0.4 mg/L for every component. Repeatability and reproducibility studies showed no significant differences at 95% confidence level. Application of multivariate calibration regression spectrophotometric methods (PLS‐1, PLS‐2, and PCR) clearly demonstrated, especially in the case of PLS‐1, the high resolving powder of these techniques if all possible interferences are suppressed. MEKC has been used for quantifying these compounds in different pharmaceutical products and the method gave good results compared with spectrophotometry. The pharmaceutical preparations do not require any separation steps when analysed by the two procedures described.
Chiral gas chromatography for the determination of 1,2‐O‐isopropylidene‐sn‐glycerol stereoisomers
Authors: Dröge Melloney J. , Bos Rein , Woerdenbag Herman J. , Quax Wim J.
Published: July 2003

A stereospecific gas chromatography (GC) method using a (6‐O‐t butyldimethylsilyl‐2,3‐di‐O‐methyl)‐β‐cyclodextrin as the chiral stationary phase has been developed and validated for the determination of the enantiomers of 1,2‐O‐isopropylidene‐sn‐glycerol (IPG), an important chiral synthon, in kinetic resolution experiments. After liquid‐liquid extraction with ethyl acetate, the enantiomers of R‐(–)‐IPG and S‐(+)‐IPG and their corresponding butyrate‐ and caprylate esters were baseline separated using this chiral GC method. The method was accurate, reproducible, specific, and precise and recoveries of at least 77% were accomplished. The detection limits for IPG and its esters were 0.6 ng and 0.1 ng, respectively. The application of this method was demonstrated by a kinetic resolution experiment using the lipase A of Bacillus subtilis.
Chemometrics in capillary electrophoresis. Part A: Methods for optimization
Authors: Sentellas Sònia , Saurina Javier
Published: July 2003

This paper reviews the application of chemometric techniques to optimise capillary electrophoresis separations. The optimization of the electrophoretic conditions should not be understood merely as an independent study of the influence of each variable on the resolution. In many cases, simultaneous optimization of several experimental variables may be required. Furthermore other important aspects such as analysis time, precision, and detection limits should also be considered as responses for a proper optimization. Other important chemometric tasks dealing with data analysis are reviewed in Part B (see S. Sentellas and J. Saurina, Chemometrics in capillary electrophoresis. Part B: Methods for data analysis).
On‐line conversion and determination of aspirin using a flow injection–capillary electrophoresis system
Authors: Chen Hong Li , Fan Liu Yin , Chen Xing Guo , Hu Zhi De , Zhao Zheng Feng , Hooper Martin
Published: July 2003

A novel, rapid, and simple capillary electrophoresis (CE) method has been developed for the determination of aspirin by on‐line treatment with alkali. Such on‐line reaction with 0.20 mol/L NaOH solution for 2.5 min at 45°C automatically and reproducibly converts aspirin into its hydrolysis product salicylic acid. Analysis is carried out in less than 12 min after conversion of aspirin in a flow injection (FI) system coupled to a CE instrument via a split‐flow interface cell, and a sampling frequency of 9 h–1 is achievable. The on‐line conversion method has been used to determine aspirin in four commercial pharmaceutical preparations, and the results are satisfactory.
Computational economy improvements in PRISM
Authors: Tonse Shaheen R. , Moriarty Nigel W. , Frenklach Michael , Brown Nancy J.
Published: July 2003

The Piecewise Reusable Implementation of Solution Mapping (PRISM) procedure is applied to reactive flow simulations of (9‐species) H2 + air combustion. PRISM takes the solution of the chemical kinetic ordinary differential equation system and parameterizes it with quadratic polynomials. To increase the accuracy, the parameterization is done piecewise, by dividing the multidimensional chemical composition space into hypercubes and constructing polynomials for each hypercube on demand. The polynomial coefficients are stored for subsequent repeated reuse. Initial cost of polynomial construction is expensive, but it recouped as the hypercube is reused, hence computational gain depends on the degree of hypercube reuse. We present two methods that help us to identify hypercubes that will ultimately have high reuse, this being accomplished before the expense of constructing polynomials has been incurred. One method utilizes the rate of movement of the chemical trajectory to estimate the number of steps the trajectory would make through the hypercube. The other method defers polynomial construction until a preset threshold of reuse has been met; an empirical method which, nevertheless, produces a substantial gain. The methods are tested on a 0‐D chemical mixture and reactive flow 1‐D and 2‐D simulations of selected laminar and turbulent H2 + air flames. The computational performance of PRISM is improved by a factor of about 2 for both methods. © 2003 Wiley Periodicals, Inc.*

This article is a US Government work and, as such, is in the public domain of the United States of America.

Int J Chem Kinet 35: 438–452, 2003
Kinetics and mechanism for the formation of o‐carboxy(N‐methyl)‐benzohydroxamic acid in the cleavage of ethyl N‐[o‐(N‐methyl‐N‐hydroxycarbamoyl)‐benzoyl]carbamate in N‐methylhydroxylamine, acetate, and phosphate buffers
Authors: Khan M. Niyaz
Published: July 2003

The rate of cleavage of ethyl N‐[o‐(N‐methyl‐N‐hydroxycarbamoyl)benzoyl]‐ carbamate (ENMBC) in the buffer solutions containing N‐methylhydroxylamine, acetate + N‐methylhydroxylamine, and phosphate + N‐methylhydroxylamine followed an irreversible consecutive reaction path: ENMBC where A and B represent N‐hydroxyl group cyclized product of ENMBC and o‐(N‐methyl‐N‐hydroxycarbamoyl)benzoic acid, respectively. Both rate constants k1 obs and k2 obs showed the presence of buffer catalysis, but buffer catalysis turned out to be weak in the presence N‐methylhydroxylamine buffer, while it was strong in the presence of acetate and phosphate ones. Buffer‐independent rate constants k10 and k20 increased linearly with the increase in aOH with definite intercepts. The values of molar absorption coefficient of A, obtained under varying total buffer concentrations at a constant pH, showed the presence of a fast equilibrium: A + CH3NHOH ⇆ C, where C represents N‐[o‐(N‐methyl‐N‐hydroxycarbamoyl)methyl]benzohydroxamic acid. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 427–437, 2003
Anharmonic thermochemistry of cyclopentadiene derivatives
Authors: Catoire Laurent , Swihart Mark T. , Gail Sandro , Dagaut Philippe
Published: July 2003

This paper focuses on the thermochemistry of some derivatives of cyclopenta‐1,3‐diene, namely, 5‐methylcyclopenta‐1,3‐diene, 5‐ethylcyclopenta‐1,3‐diene, 5‐formylcyclopenta‐1,3‐diene, 5‐methylcyclopenta‐1,3‐diene‐1‐yl radical, 5‐ethylcyclopenta‐1,3‐diene‐1‐yl radical, 5‐carbonylcyclopenta‐1,3‐diene radical, 1‐formylcyclopenta‐2,4‐diene‐1‐yl radical, 5‐methylenecyclopenta‐1,3‐diene radical, 5‐ethylidenecyclopenta‐1,3‐diene radical, and 3,6‐dimethylenecyclohexa‐1,4‐diene. Several different chemistries of these compounds are of interest in combustion modeling. Here, we present gas‐phase thermochemical properties for the above cited species, which are, except for 3,6‐dimethylenecyclohexa‐1,4‐diene, previously unknown. These were obtained from corrected (using bond additivity corrections) high‐level ab initio quantum chemistry calculations validated with well‐known compounds including cyclopentane, cyclopentene, cyclopenta‐1,3‐diene, and cyclopentadienyl radical. Heat capacities and entropies have been corrected for anharmonic molecular motions, in particular for internal rotations. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 453–463, 2003
The Interaction between Collagen and an Aluminum Tanning Agent
Authors: Li He , Chen Hua Lin , Luo Rong , Liu Bui Ling , Gao Li Zhen
Published: July 2003

The interaction between collagen and organometallic aluminum complexes was studied. From the analysis of the IR and UV spectra, the viscosity of collagen, and the treated collagen, a possible interaction model of the collagen with the aluminum tanning agent has been found. It indicates that such an aluminum tanning agent could be used as a cleaner tanning agent in leather tanning.

Viscosity curves of the untreated collagen solution (a) and the collagen solution treated with aluminum tanning agent (b).

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Viscosity curves of the untreated collagen solution (a) and the collagen solution treated with aluminum tanning agent (b).
The Shielding Effect of Nano TiO2 on Collagen under UV Radiation
Authors: Li He , Wang Diqiang , Chen Hualin , Liu Bailing , Gao Lizhen
Published: July 2003

The shielding effect of nano TiO2 on collagen under UV radiation was investigated using UV spectrophotometry. The results indicate that the shielding of collagen under UV radiation in the presence of nano TiO2 is significant. For 2.5 wt.‐% of TiO2, there is a greater shielding effect of UV radiation than that for 0.5 wt.‐% of TiO2. In addition, this study gives hints that a novel tanning agent with a UV shielding function can be formulated by using nano TiO2.

UV absorption of collagen under UV radiation after adding 2.5 wt.‐% TiO2.

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UV absorption of collagen under UV radiation after adding 2.5 wt.‐% TiO2.
Effect of the Molecular Weights of Poly‐L‐Arginine on Membrane Strength and Permeability of Poly‐L‐Arginine Group Microcapsules
Authors: Wang Shi‐bin , Liu Yuan‐gang , Weng Lian‐jin , Ma Xiao‐jun
Published: July 2003

A novel poly‐L‐arginine group microcapsule was produced to investigate its nutritional function and pharmacological efficacy. The molecular weight of poly‐L‐arginine is an important parameter for its membrane strength, but does not obviously affect its release property. Thus, poly‐L‐arginine can be used as a kind of new membrane material in microcapsules, and it is expected to be used as an therapeutic and biodegradable drug carrier.

Influence of the molecular weight of poly‐L‐arginine on membrane thickness.

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Influence of the molecular weight of poly‐L‐arginine on membrane thickness.
Large and mesoscale variability of the water masses and the deep chlorophyll maximum in the Azores Front
Authors: Pérez Fiz F. , Gilcoto M. , Ríos Aida F.
Published: July 2003

Coupling between the physical and biological fields in the upper ocean around the Azores Front (AF) was studied in summer 1998 during an oceanographic cruise to the southern Azores Islands (30°N–38°N and 20°W–33°W). On the basis of conductivity‐temperature‐depth (CTD), acoustic Doppler current profiler (ADCP), and fluorescence data, several large‐scale, mesoscale, and submesoscale physical features are described. The ADCP data and geostrophic field revealed an eastward transport associated with the Azores Current (AC) and weak countercurrents to the south and north of the AC. The water mass field shows a strong latitudinal variation in the AF with an eastward modification. From the surface to 300 dbar, the saline distribution strongly defined the AF as a very sharp vertical front. The horizontal thermohaline gradient increased to the east and reached a maximum at approximately 150 dbar. The 16.2°C isotherm and 36.2 isohaline at 150 dbar precisely located the AF along the whole area in agreement with the dynamic field. To the west of 26°W, the Azores Current was 140 km wide while the AF was only 15–25 km wide. To the east of 26°W the AC underwent a strong meandering. The water mass characteristics in the southern part of the AF show an eastward evolution between 18°C seawater and Madeira Mode Water. Data from a CTD‐fluorometer mounted on an Undulator system allowed the small‐scale structure of AF to be mapped, describing several eddies and meanders. The deep chlorophyll maximum (DCM) showed highest values (0.9 to 1.2 mg Chl m−3) toward the west (32°W) on the southern side of the AF. Chlorophyll concentrations at the DCM (0.4–0.6 mg Chl m−3) on the northern side of the study area were moderate and fairly constant whereas low values (<0.3 mg Chl m−3) were measured at the very deep DCM (120–140 m) in the southeast, associated with high saline waters. Examination of a cold eddy showed similar chlorophyll concentrations to those found on the northern side of the AF. The thermohaline structure of the eddy was similar to the AF, with northern water enclosed within saline and warm southern water.
Carbon isotopic fractionation during decomposition of plant materials of different quality
Authors: Fernandez I. , Mahieu N. , Cadisch G.
Published: July 2003

Changes in isotopic 13C composition of solid residues and CO2 evolved during decomposition of C3 and C4 plant materials were monitored over 10 months to determine carbon isotopic fractionation at successive stages of biodegradation. We selected plant materials of different chemical quality, e.g., Zea mays (leaves, stems, coarse roots, and fine roots), Lolium perenne (leaves and roots), Pinus pinaster (needles), and Cocos nucifera (coconut shell) and also characterized these by solid‐state 13C NMR. Roots were more lignified than aerial parts of the same species. Lignin was always depleted in 13C (up to 5.2‰) as compared with cellulose from the same sample. Proteins were enriched in 13C in C3 plants but depleted in maize. Cumulative CO2 evolved fitted a double‐exponential model with two C pools of different lability. During early stages of decomposition, the CO2‐C released was usually 13C depleted as compared with the initial substrate but enriched at posterior stages. Consequently, with ongoing decomposition, the solid residue became 13C depleted, which could only partly be explained by an accumulation of lignin‐C. The extension of the initial 13C depleted CO2‐C phase was significantly correlated with the labile substrate C content, acid‐detergent soluble fraction, and total N, pointing to a direct influence of plant quality on C isotopic dynamics during early stages of biodegradation. This isotopic fractionation can also lead to an underestimation of the contribution of plant residues to CO2‐C when incubated in soils. We discuss possible implications of these mechanisms of 13C fractionation in ecosystems.
Velocity variations in the uppermost mantle beneath the southern Sierra Nevada and Walker Lane
Authors: Savage Brian , Ji Chen , Helmberger Don V.
Published: July 2003

We modelPnwaveforms from two earthquakes in the southwestern United States (Mammoth Lakes, California, and western Nevada) to determine a velocity model of the crustal and mantle structure beneath the southern Sierra Nevada and Walker Lane. We derive a one‐dimensional velocity model that includes a smooth crust‐mantle transition east of Death Valley and extending south into the eastern Mojave desert. West of Death Valley and toward the Sierra Nevada a low‐velocity mantle (Vp= 7.6 km/s) directly below the crust indicates the lithosphere is absent. At the base of this low‐velocity structure (at 75–100 km depth) thePwave velocity jumps discontinuously toVp8.0 km/s. The area of low velocity is bounded by the Garlock Fault to the south and the Sierra Nevada to the west, but we cannot resolve its northern extent. However, on the basis of teleseismic travel times we postulate that the anomaly terminates at about 38°N. The presence of a low‐velocity, upper mantle anomaly in this area agrees with geochemical research on xenoliths from the southern Sierras and recent studies of receiver functions, refraction profiles, tomography, and gravity. However, the velocity discontinuity at 75–100 km is a new discovery and may represent the top of the once present, now unaccounted for and possibly sunken Sierra Nevada lithosphere.
Groundwater transport of tritium and krypton 85 from a nuclear detonation cavity
Authors: Guell Margaret A. , Hunt James R.
Published: July 2003

Underground nuclear detonations at the Nevada Test Site provide a unique opportunity to study the hydrologic transport of radionuclides in the field. At the Cambric experiment a pumped well 91 m from the detonation cavity was sampled regularly over 16 years and recovered 94% of the tritium but only 42% of the expected85Kr, both following decay correction. In addition, the elution curves were different for these two ideal tracers of groundwater movement. Modeling is used to determine the fate of the missing85Kr based on the phenomenology of underground nuclear detonations and the specific hydrogeology of the Cambric site. At Cambric, large amounts of carbon dioxide created by the detonation caused the upward migration of85Kr through the collapsing chimney and into the unsaturated zone. A numerical model simulated tritium and85Kr transport to the pumped well using tritium data to determine regional anisotropy in hydraulic conductivity and reduced hydraulic conductivity in the cavity region. The calibrated model reproduces the85Kr breakthrough data when emplacement of85Kr by the upward migration of carbon dioxide is included. Nuclear detonations provide long‐term tracer tests in the subsurface, but knowledge of the spatial distribution of sources at this specific site is essential in understanding the transport of these two radionuclide tracers.
Decoupling of fluids and fluid‐mobile elements during shallow subduction: Evidence from halogen‐rich andesite melt inclusions from the Izu arc volcanic front
Authors: Straub Susanne M. , Layne Graham D.
Published: July 2003

Very rare, halogen‐rich andesite melt inclusions (HRA) in bytownitic plagioclase phenocrysts (An89–90) from tephra fallout of the Izu arc volcanic front (Izu VF) provide new insights into the processes of fluid release from slab trenchward to the volcanic front in a cool subduction zone. These HRA are markedly enriched in Cl, F and Li ‐ by factors of up to 8 (Cl, F) and 1.5 (Li) ‐ but indistinguishable with respect to the fluid‐mobile large‐ion lithophile elements (LILE; K, Sr, Rb, Cs, Ba, Pb, U), rare earths (REE) or high field strength elements (HFSE) from the low‐K tholeiitic magmas of the Izu VF. We suggest that the chemical signature of the HRA reflects the presence of a fluid in the mantle source that originated from the serpentinized mantle peridotite above the metacrust. This “wedge serpentinite” presumably formed by fluid infiltration beneath the forearc and was subsequently down‐dragged with the slab to arc front depths. The combined evidence from the Izu VF (∼110 km above slab) and the outer forearc serpentinite seamounts (∼25 to 30 km above slab) suggests that the slab flux of B and Cl is highest beneath the forearc, and decreases with increasing slab depths. In contrast, the slab flux of Li is minor beneath the forearc, but increases with depth. Fluorine may behave similarly to Li, whereas the fluid‐mobile LILE appear to be largely retained in the slab trenchward from the Izu VF. Consequently, the chemical signatures of both Izu trench sediments and basaltic rocks appear preserved until arc front depths.
Earth's magnetic field in the early 19th century from French sources
Authors: Jackson Andrew , Jonkers Art R. T. , Mandea Mioara , Murray Anne
Published: July 2003

We present both a description of a new magnetic data set covering predominantly the 18th and 19th centuries and the results derived from it for the small window 1820–1850, from which the bulk of the data originate. The data set comprises measurements of declination taken overwhelmingly on French naval and hydrographic vessels. A list of the vessels is given for one of the data sets. When augmented by extant inclination measurements, the data are capable of resolving the magnetic field at the core‐mantle boundary to a high degree of fidelity and thus are a valuable addition to the data set of historical geomagnetic measurements.