Determination of Carotenoids in the Chinese Medical Herb Jiao-Gu-Lan (Gynostemma Pentaphyllum MAKINO) by Liquid Chromatography

A QSTAR Pulsar quadrupole time-of-flight mass spectrometer was used for the determination of chlorophenols in surface water samples. The investigated compounds were: 2-chlorophenol; 4-chloro-3-methylphenol; 2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol. Each analyte is listed by the US-EPA as a priority pollutant. Sample enrichment of water samples was achieved by a solid-phase extraction procedure, using a Waters Oasis HLB cartridges followed by LC-Tandem-MS. A narrow-bore 2.1-mm-i.d. reversed phase LC C-18 column operating with a mobile phase flow rate of 0.2 mL min^–1. was used to separate the analytes. The whole column effluent was diverted to the ion spray interface source. For the determination of the analytes the hybrid quadrupole time-of-flight spectrometer operated in product ion scan acquisition mode. Average recoveries from 2 L samples varied from 91 to 110% and relative standard deviations (RSD) were less than 10% for all samples. The limit of detection (signal-to-noise ratio=3) of the method for the phenols in drinking water samples is less than 10 ng L^–1. In real environmental samples, levels of the selected analytes varied from non-detected up to 0.5 g L^–1 for pentachlorophenol.     

Development,validation and application of an HPLC method for phenol electrooxidation products in the presence of chloride

A high-performance liquid chromatography (HPLC) method was developed and validated to determine phenol and potential intermediates from hydroxylation (hydroquinone, benzoquinone, catechol) and hypochlorination (2-chlorophenol, 3-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol, 2,6-dichlorophenol, 2,3,6-trichlorophenol, 2,4,5-trichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol) pathways during electrooxidation in the presence of chloride. A Hypersil ODS column (150 mm L × 4.6 mm I.D.) was used for the separation. The best separation was achieved when using a time variant gradient between a water mobile phase (with 0.1% formic acid adjusted to pH 3.0 with 0.1 mM sulfuric acid) and an organic phase (90:5:5 by volume mixture of acetonitrile:methanol:acetic acid). The flow rate was 0.8 mL min^?1 and UV absorbance was monitored at 270, 280, 290 and 300 nm, choosing the wavelength of strongest response for each compound. The intra- and inter-day accuracy and precision were tested using five replicates each day on three consecutive days.     

Modelling and prediction of retention in high-performance liquid chromatography by using neural networks

Summary Two analytical methods have been developed for the determination in water of 18 priority phenolics listed in US EPA method 604 and on EEC list 76/464. A solidphase extraction system using eight different sorbents packed in a precolumn was coupled on-line with a liquid chromatograph with UV detection. The ensuing method uses 50–100 mL of ground water; its performance was compared with that of an off-line method using Empore extraction disks and 1 L water samples. Phenol recoveries varied from <20 to 100% for concentrations in the range 0.1–10 g/L at an acid pH. The presence of the phenols in water was confirmed by using thermospray LC-mass spectrometry in the negative ion mode. The stability of the phenols in water was studied at a 10 g/l level in ground and estuarine water at acid pH (2.5–3) and at 4°C for 1 month. The system was validated by various interlaboratory exercises with samples containing 2,4,6-trichlorophenol and pentachlorophenol at concentrations from 0.1 to 0.5 g/L.     

Group-specific enzyme-linked immunosorbent assay for fenitrooxon and 3-methyl-4-nitrophenol in water samples based on a polyclonal antibody

Fenitrooxon [O,O-dimethyl-O-(4-nitro-m-tolyl)phosphate] is the major metabolite of the organophosphorus insecticide fenitrothion, and 3-methyl-4-nitrophenol is its major degradation product. In the present study, we describe the development of an indirect competitive enzyme-linked immunosorbent assay (ELISA) for the detection of these compounds in water samples based on a group-specific polyclonal antiserum generated with a “bifunctional hapten”, which has two functions: the conventional function of producing an antibody against an antigen and a unique function of promoting the production of the antibodies in rabbit. For application to water samples, the influence of several factors such as organic solvent, pH, and detergent was studied. Under optimized conditions, the quantitative working range of the fenitrooxon ELISA was 0.71-27 ng ml⁻¹ with a limit of detection (LOD) of 0.32 ng ml⁻¹, and the fenitrooxon concentration giving 50% reduction of the maximum signal (IC₅₀) was 4.2 ng ml⁻¹. The quantitative working range of the 3-methyl-4-nitrophenol ELISA was 0.67-27 ng ml⁻¹ with a LOD of 0.38 ng ml⁻¹ and an IC₅₀ of 3.7 ng ml⁻¹. No significant matrix effect originating from the water sample (river water, tap water, purified water, and bottled water) was shown by addition of Tween 20 to the assay buffer. Water samples spiked with each of these compounds at 1, 5, 10, and 20 ng ml⁻¹ were directly analyzed without extraction and clean-up by the proposed ELISA. The mean recovery was 100.9%, and the mean coefficient of variation (CV) was 7.7% for the fenitrooxon ELISA and for the 3-methyl-4-nitrophenol ELISA, the mean recovery was 97.6%, and the mean CV was 7.2%. The proposed ELISA allows precise and accurate determination of these compounds in water at such low levels.     

A comparison between positive and negative ion modes in thermospray liquid chromatography-mass spectrometry for the determination of chlorophenols and herbicides

Summary Positive and negative ion modes (Pl and NI, respectively) have been employed for the characterization of 2,4-dichlorophenol, 2,4,5-trichlorophenol, pentachlorophenol, Linuron and Cyanazine in thermospray (TSP) liquid chromatography-mass spectrometry (LC-MS). The PI mode showed no response when 200 ng of the different chlorophenols were injected, while for Linuron and Cyanazine high signals were obtained with [M+NH₄]⁺ and [M+acetic acid]⁺ ions as base peaks, respectively. With the NI mode, the base peak usually corresponds to the [M−H]⁻ ion, with better sensitivities for the chlorophenols than for the herbicides. The chloride adduct [M+Cl]⁻ ion was also obtained for 2,4,5-trichlorophenol and for Linuron. Although the PI mode is more sensitive than the NI mode for the two herbicides, the combination of both ionization modes offers complementary structural information for characterizing such compounds in TSP LC-MS.     

纺织品中残留氯酚的毛细管气相色谱测定法

采用稀硫酸浸湿样品,正己烷提取,乙酸酐衍生后以毛细管气相色谱分离测定的方法对纺织品中五氯酚、三氯酚残留量进行了同时测定,探讨了提取、净化及色谱分析条件。方法回收率范围三氯酚84.8％～98.1％,五氯酚88.0％～100.2％。相对标准偏差三氯酚1.54％～2.33％,五氯酚3.48％。方法的检出限（质量分数）分别为2,4,6-三氯酚1.0×10     

Approach to Optimization of FRAP Methodology for Studies Based on Selected Monoterpenes

Terpenes, wide-spread secondary plant metabolites, constitute important parts of many natural compounds that hold various biological activities, including antioxidant, calming, antiviral, and analgesic activities. Due to their high volatility and low solubility in water, studies of compounds based on terpenes are difficult, and methodologies must be adjusted to their specific characteristics. Considering the significant influence of iron ions on dementia development, the activity of terpenes in reducing Fe³⁺ represents an important area to be determined. Previously obtained results were unreliable because ferric-reducing antioxidant power (FRAP) methodology was not adjusted regarding studying terpenes. Taking this fact into account, the aim of this study was to optimize the method for monoterpene assessment. The study included three modifications, namely, (1) slightly adjusting the entire FRAP procedure, (2) replacing methanol with other solvents (heptane, butanone, or ethyl acetate), and (3) adding Tween 20. Additionally, a thin layer chromatography (TLC) -FRAP assay was performed. The obtained results revealed significant improvement in the reduction activity of selected terpenes (linalool, α-phellandrene, and α-terpinene) in studies with Tween 20, whereas replacing methanol with other solvents did not show the expected effects.     

On-line continuous-flow extraction system in liqud chromatography with ultraviolet and mass spectrometric detection for the determination of selected organic pollutants

An on-line extraction system with completely continuous-flow analysis prior to the liquid chromatographic (LC) column was used for the determination of the organophosphorus pesticides tetrachlorvinphos and parathion-methyl and their degradation products 2,4,5-trichlorophenol and 4-nitrophenol, respectively, and the chlorinated phenoxy acids 2,4-D, 2,4,5-T and silvex in water samples. The extent of extraction varied from 100% for chlorinated phenoxy acids to 60% for organophosphorus pesticides and 2,4,5-trichlorophenol. The extraction of 4-nitrophenol was less than 10% under these conditions. By employing positive-ion mode thermospray LC-mass spectrometry, the characterization of tetrachlorvinphos was feasible, indicating [M + NH₄]⁺ as the base peak and a second peak with 20% relative intensity corresponding to [M + H]⁺. When the negative-ion mode was used, the chlorinated phenoxy acids and 2,4,5-trichlorophenol exhibited [M + HCOO]^? as the base peak and a second peak with 30% relative intensity corresponding to [M ? H]^?. The determination of 1 mg l^?1 of tetrachlorvinphos spiked in a surface water sample is reported.     

Structure Sensitivity in the Hydrodechlorination of Chlorophenols

The gas phase hydrodechlorination of methanolic and mixed methanol/water solutions of 2-chlorophenol, 2,6-dichlorophenol, 2,4,5-trichlorophenol and pentachlorophenol has been studied at 573 K over nickel/silica catalysts of varying (1.5–20.3 wt.% Ni) nickel loading. Each catalyst was 100% selective in promoting hydrodechlorination: the variation of catalytic activity and selectivity with time-on-stream is illustrated and catalyst deactivation is addressed. Dechlorination is quantified in terms of specific rate constants, phenol selectivity/yield and chlorine removal efficiencies. Increasing the nickel loading resulted in a marked increase in dechlorination efficiency while the introduction of water into the feed lowered the activity.     

Generation of antiserum to Irgarol 1051 and development of a sensitive enzyme immunoassay using a new heterologous hapten derivative

A polyclonal antiserum to Irgarol 1051 was developed in sheep and used to construct an enzyme immunoassay method for the measurement of the antifouling compound in river and seawater samples. The antiserum was generated by a hapten derivative, 2-(tert-butylamino)-4-(cyclopropylamino)-6-(thiopropionic acid)-1,3,5-triazine, coupled to a mixture of keyhole limpet hemocyanin and bovine serum albumin, and the competitive enzyme immunoassay was constructed using a plate-coating antigen made of a heterologous new hapten derivative, 2-(tert-butylamino)-4-(cyclopropylamino)-6-(phenoxybenzoic acid)-1,3,5-triazine, linked to gelatine. The assay showed a sensitivity of about 5 ng L^–1 in river and seawater matrices with reasonable specificity with respect to commonly used triazines such as atrazine (3%), simazine (>0.1%) and desethylatrazine (>0.01%). However, high cross-reactivity levels were found with ametryn (56%) and prometryn (60%). Tests on the effects of organic solvents on assay performance indicated a high tolerance to methanol but much less so to acetonitrile. The assay was found to be highly reproducible and robust owing to the stability of the sheep antibody and the highly optimised competitive assay reagents which included the use of the new triazine-O-phenoxybenzoic acid derivative.     

Determination of chlorophenols in landfill leachate using headspace sampling with ionic liquid-coated solid-phase microextraction fibers combined with gas chromatography–mass spectrometry

A new microextraction technique based on ionic liquid solid-phase microextraction (IL-SPME) was developed for determination of trace chlorophenols (CPs) in landfill leachate. The synthesized ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([C₄MIM][PF₆]), was coated onto the spent fiber of SPME for extraction of trace CPs. After extraction, the absorbed analytes were desorbed and quantified using gas chromatography–mass spectrometry (GC/MS). The term of the proposed method is as ionic liquid-coated of solid-phase microextraction combined with gas chromatography–mass spectrometry (IL-SPME-GC/MS). No carryover effect was found, and every laboratory-made ionic liquids-coated-fiber could be used for extraction at least eighty times without degradation of efficiency. The chlorophenols studied were 2,4-dichlorophenol (2,4-DP), 2,4,6-trichlorophenol (2,4,6-TCP), 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP), and pentachlorophenol (PCP). The best results of chlorophenols analysis were obtained with landfill leachate at pH 2, headspace extraction for 4 min, and thermal desorption with the gas chromatograph injector at 240 °C for 4 min. Linearity was observed from 0.1 to 1000 μg L⁻¹ with relative standard deviations (RSD) less than 7% and recoveries were over 87%. The limit of detection (LOD) for pentachlorophenol was 0.008 μg L⁻¹. The proposed method was tested by analyzing landfill leachate from a sewage farm. The concentrations of chlorophenols were detected to range from 1.1 to 1.4 μg L⁻¹. The results demonstrate that the IL-SPME-GC/MS method is highly effective in analyzing trace chlorophenols in landfill leachate.     

Liquid chromatography/electrospray ionization/ion mobility spectrometry of chlorophenols with full flow from large bore LC columns

Chlorophenols (CPs) as a mixture of fourteen congeners from mono- to pentachlorophenol were determined using liquid chromatography/electrospray ionization/ion mobility spectrometry (LC/ESI/IMS) to describe the response and analytical performance of a mobility spectrometer as a detector for liquid chromatography. The mobility spectrometer was equipped with an interface so that flows from a large bore column could be electrosprayed directly into the drift tube at flow rates up to 500 μL/min without splitting of flow. A linear gradient of the mobile phase from 40% to 90% methanol and 60% to 10% acetic acid (AcOH)–ammonium acetate buffer solution over 40 min with a C18 column provided baseline separations though mobility spectra for CPs were influenced by mobile phase composition. Product ions formed from CPs with ESI included phenoxide anions CPO^?, AcOH·CPO^?, CPOH·CPO^?, and Na⁺·(CPO^?)₂ and were found to be governed by the drift gas temperature. Ions were identified using LC/ESI/mass spectrometry (MS) and supported by results from computational modeling. Quantitative response was affected by congener structure through the acidities of the OH moiety and by the composition of the mobile phase. Limits of detection ranged from 0.135 mg/L for 2,3,5-trichlorophenol and pentachlorophenol to 2.23 mg/L for 2-chlorophenol; corresponding linear ranges were 20 and 70.     

Stir bar sorptive extraction with in situ derivatization and thermal desorption-gas chromatography-mass spectrometry for determination of chlorophenols in water and body fluid samples

A new method, stir bar sorptive extraction (SBSE) with in situ derivatization and thermal desorption (TD)-gas chromatography-mass spectrometry (GC-MS), which is used for the determination of trace amounts of chlorophenols, such as 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TrCP), 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP) and pentachlorophenol (PCP), in tap water, river water and human urine samples, is described. The derivatization conditions with acetic acid anhydride and the SBSE conditions such as extraction time are investigated. Then, the stir bar is subjected to TD followed by GC-MS. The detection limits of the chlorophenols in tap water, river water and human urine samples are 1-2, 1-2, and 10-20 pg ml⁻¹ (ppt), respectively. The calibration curves for the chlorophenols are linear and have correlation coefficients higher than 0.99. The average recoveries of the chlorophenols in all the samples are higher than 95% (R.S.D. < 10%) with correction using added surrogate standards, 2,4-dichlorophenol-d₅, 2,4,6-trichlorophenol-¹³C₆, 2,3,4,6-tetrachlorophenol-¹³C₆ and pentachlorophenol-¹³C₆. This simple, accurate, sensitive and selective analytical method may be applicable to the determination of trace amounts of chlorophenols in liquid samples.     

Faster and simpler determination of chlorophenols in water by fiber introduction mass spectrometry

Solid phase microextraction (SPME) of chlorophenols [2-chlorophenol (2CP), 2,4-dichlorophenol (24CP), 4-chloro-3-methylphenol (43CP), 2,4,6-tri-chlorophenol (246CP) and pentachlorophenol (PCP)] followed by direct mass spectrometric analysis has been performed by fiber introduction mass spectrometry (FIMS). Two SPME fibers (65 μm PDMS/DVB and 85 μm PA fibers) were tested, and FIMS was performed via selective ion monitoring (SIM). The extractions were evaluated at 10% ionic strength and pH 1. Best extraction times were determined for both fibers. Limits of detection (LOD) and limits of quantification (LOQ) for both fibers were in the low μg L⁻¹ range. Coefficients of correlation for the analytical curves showed linear responses and mineral water and river water samples spiked with 50 μg L⁻¹ presented high recoveries. FIMS, as compared to current EPA methods, is demonstrated to allow faster and simpler (elimination of pre-separation or derivatization steps) analysis of chlorophenols in water with the required sensitivity.     

A confirmatory method for the determination of phenolic endocrine disruptors in honey using restricted-access material–liquid chromatography–tandem mass spectrometry

The present work describes the development and validation of an analytical method based on liquid chromatography (LC), coupled with tandem mass spectrometry (MS/MS) that allows the determination and confirmation of several endocrine-disrupting chemicals (EDCs) in honey. The EDCs studied were nine phenols of different nature: chlorophenols (2,4-dichlorophenol, 2,4,5-trichlorophenol, and pentachlorophenol), alkylphenols (4-tert-butylphenol, 4-tert-octylphenol, and 4-n-octylphenol) bisphenols (bisphenol-A and bisphenol-F), and 4-tert-butylbenzoic acid. The method incorporates a restricted-access material (RAM), coupled on-line to the LC-MS/MS system, which allows direct injection of the matrix into the RAM-LC-MS/MS system. The optimized method developed, RAM-LC-MS/MS, was applied to fortified honey samples, affording detection limits in the 0.6–7.2 ng g⁻¹ range, calculated for a signal-to-noise ratio of 3. In addition, the method was validated as a quantitative confirmatory method according to European Union Decision 2002/657/EC. The validation criteria evaluated were linearity, repeatability, reproducibility, recovery, decision limits, detection capabilities, specificity, and ruggedness. Repeatability and within-laboratory reproducibility were evaluated at two concentration levels, being ±11% or below at 20 ng g⁻¹. The decision limits (CC_α) and detection capabilities (CC_β) were in the 1.7–12.6 and 2.8–21.6 ng g⁻¹ range, respectively.     

Photodegradation of Cinnamic Acid in Different Media

The photodegradation of cinnamic acid under UVB irradiation was evaluated in different vehicles, such as water solutions at different pH values, Tween‐20 micelles, liposomes, and O/W emulsions prepared with Xalifin 15 or Montanov 68 as emulsifiers. The increase of pH decreases the photodegradation of cinnamic acid in all the vehicles studied. Micellar solutions showed a protective effect against cinnamic acid photodegradation; this property increases according to the surfactant percentage. Emulsions appeared to be the most efficient protective systems while liposomes had lower ability to protect cinnamic acid against UVB photodegradation.     

Radiolytic transformations of chlorinated phenols and chlorinated phenoxyacetic acids

Hydroxyl radical reactions of selected chlorinated aromatic phenols (2,4-dichlorophenol, 2,4,6-trichlorophenol, and pentachlorophenol) and chlorinated phenoxyacetic acids [2,4-dichlorophenoxyacetic acid (2,4-D), 2,4-D methyl ester, 2-(2,4-dichlorophenoxy)propionic acid (2,4-DP)] were studied using the radiolysis techniques of pulse radiolysis and gamma radiolysis. Hydroxyl radical addition was the prominent reaction pathway for the chlorinated phenoxyacetic acids and also for the chlorinated phenols at pH values below the pK(a) of the compounds. A very prominent change in (*)OH reactivity was observed with the chlorinated phenoxide ions in high pH solutions. Two different reaction pathways were clearly present between the hydroxyl radical and the chlorinated phenoxide ions. One of the reaction pathways was suppressed when the concentration of chlorinated phenoxide ions was increased 10-fold. Amid a greater electron-withdrawing presence on the aromatic ring (higher chlorinated phenoxide ions), the hydroxyl radical reacted preferably by way of addition to the aromatic ring. Steady-state experiments utilizing gamma radiolysis also showed a substantial decrease in oxidation with an increase in pH of substrate.     

Use of polymeric sorbents for the off-line preconcentration of priority pollutant phenols from water for high-performance liquid chromatographic analysis

The use of porous polymeric minicolumns for the determination of phenols from the U.S. Environmental Priority Pollutant List was studied. For the off-line preconcentration of priority pollutant phenols from water by solid-phase extraction, minicolumns packed with 1,4-di(methacryloyloxymethyl)naphthalene-divinylbenzene copolymer and Amberlite XAD-4 were used. In order to compare the sorption properties of these polymeric sorbents, the recoveries and breakthrough volumes of phenol, p-nitrophenol, 2,4-dinitrophenol, o-chlorophenol, o-nitrophenol, 2,4-dimethylphenol, 4-chloro-m-cresol, 4,6-dinitro-o-cresol, 2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol were studied.     

Colon-specific devices based on methacrylic functionalized Tween monomer networks: Swelling studies and in vitro drug release

Colon-targeted delivery devices based on methacrylic functionalized Tween monomer networks, useful for 5-FU or Ferulic acid site-specific release, were synthesized. The basic design consists of methacrylic functionalized Tween monomer-based networks prepared with or without acrylic acid as co-monomer. The swelling behaviour and loaded drugs release from these gels was studied as a function of pH. The devices showed a strong pH-dependent swelling behaviour, allowing a maximum release at pH 7.4. The acrylic acid introduction increased the polymeric gels pores size, as evidenced by the loading efficiency increase, but also reduced the amount of released drug in basic media compared to analogous network not containing the co-monomer. This behaviour, already found in the matrix swelling, could be attributed to a slower hydrolysis kinetics of the ester bond in functionalized Tween monomers, which implies a reduced ability to absorb water from a basic medium, resulting in a lower capacity to release the loaded drug.Since our device possesses a maximum drug release in the media at pH 7.4, it could be used for colon-targeted drug delivery of both 5-FU and Ferulic acid.     

Determination of phenoxy herbicides in water samples using phase transfer microextraction with simultaneous derivatization followed by GC‐MS analysis

A sensitive and accurate method for the determination of two model phenoxy herbicides, 4‐chloro‐2‐methylphenoxy acetic acid and 4‐chloro‐2‐methylphenoxy propanoic acid, in water is explained. This method utilizes a simple phase transfer catalyst‐assisted microextraction with simultaneous derivatization. Factors affecting the performance of this method including pH of the aqueous matrix, temperature, extraction duration, type and amount of derivatization reagents, and type and amount of the phase transfer catalyst are examined. Derivatization and the use of phase transfer catalyst have proven to be especially vital for the resolution of the analytes and their sensitive determination, with an enrichment factor of 288‐fold for catalyzed over noncatalyzed procedure. Good linearity ranging from 0.1 to 80 μg L^?1 with correlation of determination (r²) between 0.9890 and 0.9945 were obtained. Previous reported detection limits are compared with our new current method. The low LOD for the two analytes (0.80 ng L^?1 for 4‐chloro‐2‐methylphenoxy propanoic acid and 3.04 ng L^?1 for 4‐chloro‐2‐methylphenoxy acetic acid) allow for the determination of low concentrations of these analytes in real samples. The absence of matrix effect was confirmed through relative recovery calculations. Application of the method to seawater and tap water samples was tested, but only 4‐chloro‐2‐methylphenoxy propanoic acid at concentrations between 0.27 ± 0.01 and 0.84 ± 0.06 μg L^?1 was detected in seawater samples.