Simultaneous determination of salsolinol enantiomers and dopamine in human plasma and cerebrospinal fluid by chemical derivatization coupled to chiral liquid chromatography/electrospray ionization-tandem mass spectrometry

A sensitive, specific, and robust method to simultaneously determine enantiomeric salsolinol (1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline, SAL), a potential biomarker implicated in alcohol-related neurotoxicity in a stereoselective manner, and its precursor dopamine (DA) has been developed using simple chemical derivatization and chiral separation coupled with electrospray ionization-tandem mass spectrometry (ESI-MS/MS). SAL enantiomers and DA were converted to stable pentafluorobenzyl (PFB) derivatives directly from aqueous media. Bulky PFB groups introduced into the SAL structure enabled baseline separation of SAL stereoisomers on a chiral column without cumbersome chiral derivatization to unstable SAL diastereomers. Subsequent analysis by ESI-MS/MS with multiple reaction monitoring (MRM) in the presence of deuterium-labeled internal standards allowed specific detection of both derivatives with a wide dynamic range (SAL, 0.5-5000 pg; DA, 0.02-20 ng). The limit of quantitation assayed in the plasma matrix was below 10 pg for each SAL enantiomer and 100 pg for DA. Both coefficient of variance and error for inter- and intraday measurements in the blank plasma were less than 10% for SAL and DA in the concentration range of 10-4000 pg/mL and 0.1-8 ng/mL, respectively. This strategy enabled routine and specific determination of both SAL enantiomers and DA from 0.5 mL of human plasma and cerebrospinal fluid, which has not been possible using existing methodologies.     

Enantiomeric Separation and Detection of 2-Arylpropionic Acids Derivatized with [(N,N-Dimethylamino)sulfonyl]benzofurazan Reagents on a Modified Cellulose Stationary Phase by High-Performance Liquid Chromatography

(RS)-2-Arylpropionic acids (2-APAs) were derivatized with the fluorogenic reagents, 4-[(N,N-dimethylamino)sulfonyl]-7-piperazino-2,1,3-benzoxadiazole (DBD-PZ) and 4-[[(N-hydrazinoformyl)methyl]-N-methyl]amino-7-[N,N-(dimethylamino)sulfonyl]-2,1,3-benzoxadiazole (DBD-COHz), and their enantiomeric separation by a chiral stationary phase high-performance liquid chromatography was investigated in the reversed-phase mode with H(2)O/CH(3)CN or H(2)O/MeOH as the mobile phase on a column of cellulose tris(3,5-dimethylphenyl carbamate) coated on a silica gel support (Chiralcel OD-R). The derivatives with DBD-PZ were enantiomerically separated well under the elution condition of H(2)O/MeOH, based on the π-π interaction between the derivatives and the stationary phase. The rigid and bulky structure of DBD-PZ was demonstrated to be more effective as compared to the less rigid ones. The derivatives with DBD-COHz were more efficiently separated into each enantiomer with H(2)O/CH(3)CN as the eluent. The effective separation was based on hydrogen-bonding interaction between the acid hydrazide of the derivatives and the carbamoyl moiety of the stationary phase. There was a reversal in the elution order of the enantiomers between the two fluorescent derivatives. The detection limits obtained for each enantiomer were approximately 10-30 fmol on column. The derivatization with the reagent and the concomitant use of the reversed-phase and chiral stationary-phase HPLC were demonstrated to be useful for the enantiomeric quantification in rat plasma after intravenous administration of flurbiprofen racemate, a representative of 2-APAs.     

Mathematical modelling of 4-chlorophenol inhibition on COD and 4-chlorophenol removals in an activated sludge unit

A mathematical model was developed for an activated sludge unit treating 4-chlorophenol (4-CP) containing synthetic wastewater composed of diluted molasses, urea, KH(2)PO(4) and MgSO(4) with COD and 4-CP contents of 2500 and 500 mg l(-1), respectively. The model included 4-CP inhibition on COD and 4-CP removals. Experimental data obtained at different hydraulic residence times (HRT=5-30h) and sludge ages (SRT, 3-30 days) were used to estimate the kinetic and inhibition constants for COD and 4-CP removal rates. 4-CP inhibition on COD removal was negligible while the inhibition on 4-CP removal was significant. The specific rate constant (k), saturation constant (K(s)) for COD oxidation were found to be 2.64 day(-1) and 559 mg l(-1), respectively. A similar model was used for 4-CP oxidation in the activated sludge unit and the constants were found to be k'=1.44 day(-1), K'(s)=25.7 mgl(-1), K"(CP)=559 mg l(-1),and K(I,CP)=17 mg l(-1). Increases in death rate constant because of 4-CP inhibition was also quantified and the inhibition constants were determined for both COD and 4-CP removals. Model predictions with the estimated kinetic constants were in good agreement with the experimental data. Developed model can be used to estimate the performance of an activated sludge unit treating 4-CP containing wastewater under the specified experimental conditions.     

芳香酮不对称催化氢化反应过程的手性毛细管气相色谱分析

提出了一种跟踪监测芳香酮手性催化氢化反应过程的气相色谱分析新方法。它可以快速准确地测定反应过程芳香酮的转化率、产物芳香醇对映体的过量百分数(e.e.值)及其构型。该法用于一系列芳香酮不对称催化氢化反应催化剂的性能评价,对筛选催化剂和优化反应条件,取得了到良好的效果。     

Modeling the kinetics of UV/hydrogen peroxide oxidation of some mono-, di-, and trichlorophenols

The decomposition of a number of chlorophenols (CPs), namely 2-CP, 2, 4-dichlorophenol and 2,4,6-trichlorophenol, has been studied in aqueous solution by UV-catalyzed oxidation with H(2)O(2) under UV radiation emitted by a 125-W medium pressure Hg lamp in an immersion well-type quartz photoreactor, and the organic-bound chlorine has been converted into the environmentally harmless inorganic chloride. For oxidant/CP mole ratios between 1:1 and 16:1, the reaction kinetics were modeled and the corresponding rate constants found by periodically measuring the remaining CP, hydrogen peroxide and converted chloride in solution. A theoretical model for the degradation pathway is proposed expressing the rate as a linear function of the concentrations of CP and oxidant. The rate constants for the pseudo-first order approximation of the CP degradation were compared. H(2)O(2), when combined with UV, is an effective photoactivated oxidant. The photodegradation order in terms of the initial rate of CPs destruction was: Cl(3).Ph>/=Cl(2).Ph>Cl.Ph.     

Colorimetric chiral recognition of enantiomers using the nucleotide-capped silver nanoparticles

Chiral recognition is among the important and special modes of molecular recognition. It is highly desirable to develop a simple, rapid, sensitive, and high-throughput routine assay for chiral recognition. In this study, we demonstrate that nucleotide-capped Ag nanoparticles (AgNPs) can be used as an ultrahigh efficiency enantioseparation and detection platform for d- and l-cysteine. The aggregation of AgNPs is selectively induced by an enantiomer of cysteine, which allowed the rapid colorimetric enantiodiscrimination of cysteine without any prior derivatization and specific instruments and left an excess of the other enantiomer in the solution, thus resulting in enantioseparation. This is the first application of a nucleotide-capped AgNP-based biosensing platform for chiral recognition and opens new opportunities for design of more novel enantiosensing strategies and enantiospecific adsorbents and expansion of its application in different fields.     

Catalytic wet air oxidation of chlorophenols over supported ruthenium catalysts

A series of noble metal (Pt, Pd, Ru) loaded zirconia catalysts were evaluated in the catalytic wet air oxidation (CWAO) of mono-chlorophenols (2-CP, 3-CP, 4-CP) under relatively mild reaction conditions. Among the investigated noble metals, Ru appeared to be the best to promote the CWAO of CPs as far as incipient-wetness impregnation was used to prepare all the catalysts. The position of the chlorine substitution on the aromatic ring was also shown to have a significant effect on the CP reactivity in the CWAO over 3wt.% Ru/ZrO(2). 2-CP was relatively easier to degradate compared to 3-CP and 4-CP. One reason could be the higher adsorption of 2-CP on the catalyst surface. Further investigations suggested that 3wt.% Ru/ZrO(2) is a very efficient catalyst in the CWAO of 2-CP as far as high 2-CP conversion and TOC abatement could still be reached at even lower temperature (393K) and lower total pressure (3MPa). Additionally, the conversion of 2-CP was demonstrated to increase with the initial pH of the 2-CP solution. The dechlorination reaction is promoted at higher pH. In all cases, the adsorption of the reactants and the reaction intermediates was shown to play a major role. All parameters that would control the molecule speciation in solution or the catalyst surface properties would have a key effect.     

High efficiency removal of 2-chlorophenol from drinking water by a hydrogen-based polyvinyl chloride membrane biofilm reactor

A continuously stirred hydrogen-based membrane biofilm reactor (MBfR) with polyvinyl chloride (PVC) hollow fiber membrane was investigated for removing 2-chlorophenol (2-CP) from contaminated drinking water. The bioreactor startup was achieved by acclimating the microorganisms from a denitrifying and sulfate-reducing MBfR to the drinking water contaminated by 2-CP. The effects of some major factors, including 2-CP loading, H(2) pressure, nitrate loading, and sulfate loading, on the removal of 2-CP by the MBfR were systematically investigated. Although the effluent 2-CP concentration increased with its increasing influent loading, the removing efficiency of 2-CP by the MBfR could be up to 94.7% under a high influent loading (25.71 mg/L d). The removing efficiency of 2-CP by the MBfR could be improved by higher H(2) pressure, and lower influent nitrate concentration and sulfate concentration. A high H(2) pressure can assure enough available H(2) as the electron donor for 2-CP degradation. The competition in the electron donor made nitrate and sulfate inhibit the degradation of 2-CP in the MBfR. The electron flux analyses indicated that the degradation of 2-CP only accounted for a small part of electron flux, and the autohydrogenotrophic bacteria in the MBfR were highly efficient for the 2-CP removal.     

Separation of chiral biodegradation intermediates of linear alkylbenzenesulfonates by capillary electrophoresis

High-performance capillary electrophoresis (HPCE) with α-cyclodextrin as the chiral selector was applied to separate the enantiomers of p-sulfophenyl-2-butyrate (SP2B) and p-sulfophenyl-3-butyrate (SP3B), which occur as biodegradation intermediates of linear alkylbenzenesulfonates (LAS), the widely used anionic surfactants. With this analytical method, we studied the transformation of both SP3B enantiomers in a laboratory batch incubation with activated sewage sludge of a municipal wastewater treatment plant. (S)-(+)-SP3B and (R)-(-)-SP3B could be detected in mechanically treated sewage effluent. After enrichment on graphitized carbon black (Carbopack B), the extracts were analyzed by HPLC with UV diode array and fluorescence detection as well as by HPCE with UV diode array detection. Quantification of SP3B in a 24-h composite sample of primary sewage effluent yielded 34 μg/L (limit of detection, 0.1 μg/L) of the racemic mixture determined by HPLC and 18 μg/L of each enantiomer measured by HPCE (limit of detection, 1 μg/L).     

Biological treatment of para-chlorophenol containing synthetic wastewater using rotating brush biofilm reactor

A novel rotating brush biofilm reactor (RBBR) was used for para-chlorophenol (4-chlorophenol, 4-CP), COD and toxicity removal from synthetic wastewater containing different concentrations of 4-CP. Effects of major operating variables such as the feed 4-CP and COD concentrations and A/Q (biofilm surface area/feed flow rate) ratio on the performance of the biofilm reactor were investigated. A Box-Wilson statistical experiment design method was used by considering the feed 4-CP (0-1000 mg l(-1)), COD (2000-6000 mg l(-1)) and A/Q ratio (73-293 m(2) day m(-3)) as the independent variables while the 4-CP, COD and toxicity removals were the objective functions. The results were correlated by a response function and the coefficients were determined by regression analysis. Percent 4-CP, COD and toxicity removals determined from the response functions were in good agreement with the experimental results. 4-CP, COD and toxicity removals increased with decreasing feed 4-CP and increasing A/Q ratio. Optimum conditions resulting in maximum COD, 4-CP and toxicity removals were found to be A/Q ratio of nearly 180 m(2) day m(-3), feed COD of nearly 4000 mg l(-1) and feed 4-CP of less than 205 mg l(-1).     

Supramolecular method for the determination of absolute configuration of chiral compounds: theoretical derivatization and a demonstration for a phenolic crown ether-2-amino-1-ethanol system

A combination of anisotropic shielding effect and temperature dependence of NMR chemical shifts makes it possible to develop a supramolecular method for determination of absolute configuration of chiral compounds. The concept, theoretical derivatization, and first demonstration of this daedal noncovalent method using a host-guest system is described. This noncovalent method requires only three substrate solutions and can in principle be applied to any host-guest systems that follow the van't Hoff relation and have a clear anisotropic shielding effect based on a well-defined complex structure regardless of the extent of enantiomer selectivity.     

Preparative enantiomer separation of dichlorprop with a cinchona-derived chiral selector employing centrifugal partition chromatography and high-performance liquid chromatography: a comparative study

A countercurrent chromatography protocol for support-free preparative enantiomer separation of the herbicidal agent 2-(2,4-dichlorphenoxy)propionic acid (dichlorprop) was developed utilizing a purposefully designed, highly enantioselective chiral stationary-phase additive (CSPA) derived from bis-1,4-(dihydroquinidinyl)phthalazine. Guided by liquid-liquid extraction experiments, a solvent system consisting of 10 mM CSPA in methyl tert-butyl ether and 100 mM sodium phosphate buffer (pH 8.0) was identified as a suitable stationary/mobile-phase combination. This solvent system provided an ideal compromise among stationary-phase retention, enantioselectivity, and well-balanced analyte distribution behavior. Using a commercial centrifugal partition chromatography instrument, complete enantiomer separations of up to 366 mg of racemic dichlorprop could be achieved, corresponding to a sample load being equivalent to the molar amount of CSPA employed. Comparison of the preparative performance characteristics of the CPC protocol with that of a HPLC separation using a silica-supported bis-1,4-(dihydroquinidinyl)phthalazine chiral stationary phase CSP revealed comparable loading capacities for both techniques but a significantly lower solvent consumption for CPC. With respect to productivity, HPLC was found to be superior, mainly due to inherent flow rate restrictions of the CPC instrument. Given that further progress in instrumental design and engineering of dedicated, highly enantioselective CSPAs can be achieved, CPC may offer a viable alternative to CSP-based HPLC for preparative-scale enantiomer separation.     

COD, para-chlorophenol and toxicity removal from para-chlorophenol containing synthetic wastewater in an activated sludge unit

Chlorinated phenolic compounds present in some chemical industry wastewaters cause severe toxic effects on the organisms and often are resistant to biological degradation. Synthetic wastewater containing different concentrations of para-chlorophenol (4-chlorophenol, 4-CP) was biologically treated in an activated sludge unit for COD, 4-CP and toxicity removal. Effects of feed 4-CP concentration on COD, 4-CP, toxicity removals and on sludge volume index were investigated at a constant sludge age of 20 days and hydraulic residence time (HRT) of 25 h. Resazurin method based on dehydrogenase activity was used for determination of the toxicity of the feed and effluent wastewater. COD and 4-CP removals were not affected by the presence of 4-CP in the wastewater up to feed 4-CP concentration of 925 mg l(-1) because of almost complete degradation of 4-CP yielding lower than 50 mg l(-1) 4-CP in the aeration tank. Percent COD, 4-CP and toxicity removals decreased and the effluent COD, 4-CP and toxicity levels increased with further increases in the feed 4-CP concentrations above 925 mg l(-1) because of inhibitory concentrations of 4-CP in the reactor. Biomass concentration in the aeration tank decreased and the sludge volume index (SVI) increased with feed 4-CP concentrations above 925 mg l(-1) resulting in lower COD and 4-CP removal rates. The rates of COD and 4-CP removals indicated substrate (4-CP) inhibition for the feed 4-CP concentrations above 925 mg l(-1) corresponding to the reactor 4-CP of above 200 mg l(-1). The system should be operated at the feed 4-CP concentrations of less than 900 mg l(-1) (4-CP(R) < 200 mg l(-1)) in order to obtain high rates and extents of COD, 4-CP and toxicity removals at a sludge age of 20 days and HRT of 25 h.     

Chiral polymeric reagents for off-line and on-line derivatizations of enantiomers in high-performance liquid chromatography with ultraviolet and fluorescence detection: an enantiomer recognition approach

Optically active and detector-sensitive polymeric reagents have been synthesized, loadings determined, derivatizations/separations/detection optimized, and applications to simple amines and amino alcohols described. Such reagents have been designed to contain different chiral centers, usually amino acids, leashed via an activated ester attachment to an insoluble, structurally rigid, organic polymer backbone. 9-Fluorenylmethyl (FMOC) moieties chemically bonded to the amino acids were used as ultraviolet (UV) and fluorescence (FL) sensitive detector probes to the final diastereomers of enantiomer substrates. Such diastereomers can be readily separated by isocratic or gradient elution normal-phase methods. The kinetics for diastereomer formation have been determined, and final UV/FL responses for known mixtures of enantiomers have been compared to demonstrate overall validity of the method. Minimum detection limits, linearity of calibration plots, dual detector responses, and linear diode array spectra and absorbance ratios have also been demonstrated. In some cases, authentic standards have been prepared to calculate absolute percent derivatizations for specific enantiomer pairs. The overall approach permits, for the very first time, off-line or on-line precolumn derivatization for the formation of diastereomers having unique detector properties. It has been proven that the rates and rate constants for such formations are identical for at least those pairs of enantiomers studied. Separations are base-line or near-base-line, permitting accurate and precise quantitative determinations, by both UV and FL, of enantiomer/optical purity and chemical purity.     

Hydroxyapatite deposition study through polymeric process on commercially pure Ti surfaces modified by laser beam irradiation

Many techniques have been used to coat metallic substrate with bioceramics. The aim of this study was to study the physical-chemical characteristics of polyvinylidene fluoride (α-PVDF)/hydroxyapatite (HA) composite coating, obtained by casting method, on commercially pure titanium (α-CP Ti) substrate surface modified by laser beam irradiation. The preparation of coating was done for mixing α-PVDF pellets shape dissolved in dimethylacetamide (DMA) with HA/DMA emulsion. The mixture was poured onto the α-CP Ti sample and left to dry in an oven. CP Ti plates were coated with α-PVDF/HA composite film, in proportions of 100/00 and 60/40 in weight, and characterized by particle size analysis, scanning electron microscopy, energy dispersive spectroscopy (EDS), X-ray diffractometry, thickness measurement and contact angle. Uniform coating with a small thickness variation along the coated surface was successfully obtained.     

Injection port derivatization following ion-pair hollow fiber-protected liquid-phase microextraction for determining acidic herbicides by gas chromatography/mass spectrometry

Injection port derivatization following ion-pair hollow fiber-protected liquid-phase microextraction (LPME) for the trace determination of acidic herbicides (2,4-dichlorobenzoic acid, 2,4-dichlorophenoxyacetic acid, 2-(2,4-dichlorophenoxy)propionic acid, 3,5-dichlorobenzoic acid, 2-(2,4,5-trichlorophenoxy)propionic acid) in aqueous samples by gas chromatography/mass spectrometry (GC/MS) was developed. Prior to GC injection port derivatization, acidic herbicides were converted into their ion-pair complexes with tetrabutylammonium chloride in aqueous samples and then extracted by 1-octanol impregnated in the hollow fiber. Upon injection, ion pairs of acidic herbicides were quantitatively derivatized to their butyl esters in the GC injection port. Thus, several parameters related to the derivatization process (i.e., injection temperature, purge-off time) were evaluated, and main parameters affecting the hollow fiber-protected LPME procedure such as extraction organic solvent, ion-pair reagent type, pH of aqueous medium, concentration of ion-pair reagent, sodium chloride concentration added to the aqueous medium, stirring speed, and extraction time profile, optimized. At the selected extraction and derivatization conditions, no matrix effects were observed. This method proved good repeatability (RSDs <12.3%, n = 6) and good linearity (r2 > or = 0.9939) for spiked deionized water samples for five analytes. The limits of detection were in the range of 0.51-13.7 ng x L(-1) (S/N =3) under GC/MS selected ion monitoring mode. The results demonstrated that injection port derivatization following ion-pair hollow fiber-protected LPME was a simple, rapid, and accurate method for the determination of trace acidic herbicides from aqueous samples. In addition, this method proved to be environmentally friendly since it completely avoided open derivatization with potentially hazardous reagents.     

Exploring the interparticle electron transfer process in the photocatalytic oxidation of 4-chlorophenol

This work aimed to investigate the interparticle electron transfer (IPET) process within the coupled-photocatalyst systems on the basis of the degradation of 4-chlorophenol (4-CP). TiO(2), ZnO and SnO(2) are used as the model photocatalysts owing to their increasing energy levels which correspond to the IPET concept. In the single-photocatalyst tests, ZnO tests are associated with the highest degradation rate constants (0.347+/-0.083 h(-1) at pH 7 and 0.453+/-0.011 h(-1) at pH 11) and a better DOC reduction than in other single catalyst tests under given conditions. ZnO/SnO(2) coupled tests have constants of 0.612+/-0.068 and 0.948+/-0.069 h(-1) at pH 7 and 11, respectively. Additionally, the 4-CP prefers the breakdown of chloride group in TiO(2) system while proceeding hydroxylation reaction in ZnO systems. Meanwhile, a phenomenonlogical model coupled with the IPET effect was developed to explore the separation of photo-electrons and photo-holes within catalysts. Based on the model parameters, the recombination rate of photo-electrons and photo-holes in TiO(2)/SnO(2) and ZnO/SnO(2) systems is 20-45% lower than that obtained by a respective single catalyst. Thus, coupled-photocatalyst tests, TiO(2)/SnO(2) and ZnO/SnO(2) efficiently suppress the recombination, particularly for ZnO/SnO(2) tests at pH 11.     

Fluorogenic derivatization reagents suitable for isolation and identification of cysteine-containing proteins utilizing high-performance liquid chromatography-tandem mass spectrometry

The fluorogenic derivatization reagents with a positive charge, 4-(dimethylaminoethylaminosulfonyl)-7-chloro-2,1,3-benzoxadiazole (DAABD-Cl) and 7-chloro-2,1,3-benzoxadiazole-4-sulfonylaminoethyltrimethylammonium chloride (TAABD-Cl), are proposed for use in proteomics studies. Following derivatization of protein mixtures with these reagents, a series of standard processes of isolation, digestion, and identification of the proteins were performed utilizing high-performance liquid chromatography-fluorescence detection and tandem mass spectrometry with the probability-based protein identification algorithm. Both DAABD and TAABD derivatives were detected fluorometrically at the femtomole level and showed more than 100-fold improvement in sensitivity compared to the underivatized original compounds with an electrospray ionization ion trap mass spectrometer analysis. The modification of the MASCOT database search system memorized with the fragment information of a DAABD-attached Cys residue allowed the identification of the proteolytic peptide fragments of the derivatized bovine serum albumin (BSA) with an estimated 38% sequence coverage of BSA. Utilizing DAABD-Cl as a derivatization reagent, identification of several proteins was also possible in a soluble extract of Caenorhabditis elegans (10 microg of protein). Consequently, for identification of proteins in the complex matrixes of proteins, DAABD-Cl could be a more appropriate reagent than ammonium 7-fluoro-2,1,3-benzoxadiazole-4-sulfonate as reported previously.     

Chiral separations using polymeric surfactants and polyelectrolyte multilayers in open-tubular capillary electrochromatography

In this study, fused-silica capillaries are modified using a polyelectrolyte multilayer (PEM) coating procedure in open-tubular capillary electrochromatography. The PEM coating was constructed in situ with alternating rinses of positively and negatively charged polymers. The quaternary ammonium salt poly (diallyldimethylammonium chloride) was used as the cationic polymer, and the polymeric surfactant poly (sodium N-undecanoyl-l-leucylvalinate) was used as the anionic polymer. Previous studies have shown that the PEM-coated capillaries used for achiral separations have excellent reproducibilities and high stabilities against extreme pH values. In the current study, this PEM coating approach was applied to chiral separations of 1,1'-binaphthyl-2,2'-dihydrogenphosphate (BNP), 1,1'-bi-2-naphthol, secobarbital, pentobarbital, and temazepam. However, the PEM coating procedure used in the achiral studies needed to be significantly modified in order to achieve chiral separations. Optimal conditions were established by varying the additives (sodium chloride, 1-ethyl-3-methyl-1H-imidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium tetrafluoroborate) in the polymer deposition solutions, the salt concentration, the column temperature, and the bilayer number. Reproducibilities were evaluated by use of the relative standard deviation (RSD) values of the electroosmotic flow (EOF) and the first peak ((R)-(+)-BNP). In all cases, the run-to-run and capillary-to-capillary RSD values of EOF were less than 0.5%, and the run-to-run RSD values of the (R)-(+)-BNP peak were less than 1%. In addition, more than 230 runs were performed on a single PEM-coated capillary.     

Evaluation of the influences of solution path length and additives concentrations on the solar photo-Fenton degradation of 4-chlorophenol using multivariate analysis

This study reports the photodegradation of 4-chlorophenol (4-CP) in aqueous solution by the photo-Fenton process using solar irradiation. The influence of solution path length, and Fe(NO(3))(3) and H(2)O(2) concentrations on the degradation of 4-CP is evaluated by response surface methodology. The degradation process was monitored by the removal of total organic carbon (TOC) and the release of chloride ion. The results showed a very important role of iron concentration either for TOC removal or dechlorination. On the other hand, a negative effect of increasing solution path length on mineralization was observed, which can be compensated by increasing the iron concentration. This permits an adjustment of the iron concentration according to the irradiation exposure area and path length (depth of a tank reactor). Under optimum conditions of 1.5 mM Fe(NO(3))(3), 20.0 mM H(2)O(2) and 4.5 cm solution path length, 17 min irradiation under solar light were sufficient to reduce a 72 mg CL(-1) solution of 4-CP by 91%.