A. Zafra

Gas chromatographic–mass spectrometric method for the determination of bisphenol A and its chlorinated derivatives in urban wastewater

The simultaneous determination of trace amounts of endocrine disruptors such as bisphenol A (BPA) and its monochloro, dichloro, trichloro and tetrachloro derivatives in wastewater has been developed using gas chromatography-mass spectrometry (GC-MS). Compounds were previously extracted from the aqueous samples using a liquid-liquid extraction procedure with a mixture of dichloromethane:carbon tetrachloride (25/75). After extraction, solvent was removed and a silylation step was carried out with N,O-bis(trimethylsilyl) trifluoroacetamide (BSTFA). The silylated compounds were identified and quantified by GC-MS using an HP1-MS column. The retention times were 6.64 min for BPA silylated, 7.26 min for Cl-BPA silylated, 7.99 min for Cl(2)-BPA silylated, 8.85 min for Cl(3)-BPA silylated and 9.95 min for Cl(4)-BPA silylated. A clean-up is not necessary using SIM mode. Deuterated anthracene (2H(10)-anthracene) was used as an internal standard. The detection limits obtained were 0.3, 0.6, 2.0, 4.5 and 13.0 ng L(-1) for silylated BPA, Cl-BPA, Cl(2)-BPA, Cl(3)-BPA and Cl(4)-BPA, respectively. The proposed method was applied satisfactory to the determination of these chemicals, in different types of wastewater previously spiked with different amounts of these chemicals at concentration levels ranging from 0.01 to 2.50 microg L(-1) for BPA, 0.05-2.50 micro L(-1) for Cl-BPA and 0.05-5.00 microg L(-1) for Cl(2)-BPA, Cl(3)-BPA and Cl(4)-BPA, respectively. The method was validated following standard addition methodology.

Determination of trace amounts of bisphenol F, bisphenol A and their diglycidyl ethers in wastewater by gas chromatography–mass spectrometry

A simple and sensitive method for the determination of trace amounts of bisphenol F, bisphenol A and their diglycidyl ethers in wastewater is proposed. The method involves a liquid‐liquid extraction (LLE) procedure using trichloromethane followed by a silylation step. Identification and quantification was performed by gas chromatography‐mass spectrometry (GC‐MS) using an HP1-MS column. The retention times were 6.59 and 7.02 min for BPF and BPA silylated, respectively, 8.30, 9.10 and 10.13 min for the three isomers of BFDGE and 11.12 min for BADGE. A clean-up is not necessary using SIM mode. Deuterated anthracene ( 2 H10-anthracene) was used as an internal standard. The detection limits obtained were 0.02, 0.006, 0.13 and 0.09m gl 1 for BPF, BPA, BFDGE and BADGE, respectively. The method was applied to the determination of these chemicals, as indicators of contamination by epoxy resins, in different types of spiked urban wastewater from Granada and Melilla (Spain) at concentration levels ranging from 0.06 to 2.50 m gl 1 for bisphenol F, 0.02 to 0.50m gl 1 for bisphenol A, 0.45 to 50.00m gl 1 for BFDGE and 0.30 to 50.00m gl 1 for BADGE.

Determination of polyphenolic compounds in wastewater olive oil by gas chromatography-mass spectrometry

A simple and sensitive method for the determination of 21 polyphenolic compounds in wastewater from olive oil production plants is proposed. The method involves a liquid-liquid microextraction (LLME) procedure with ethyl acetate followed by a silylation step. Identification and quantification have been performed by gas chromatography-mass spectrometry (GC-MS). MS measurements were carried out using selected ion monitoring mode (SIM). alpha-Naftol was used as internal standard. The proposed method was applied to the determination of these compounds in wastewater from an olive oil production factory in Jaén (Spain) at concentration levels ranging from 1.0 to 75.0mugml(-1) for each compound. The autodegradation process by own microbiota in samples collected in three different points of the factory was also studied. The method was validated by a recovery assay with spiked samples.

Determination of bisphenol A (BPA) in the presence of phenol by first-derivative fluorescence following micro liquid-liquid extraction (MLLE).

Bisphenol A (BPA) in the presence of phenol is determined using a method based on first-derivative spectrofluorimetry. The proposed method involves a micro liquid-liquid extraction of sodium chloride saturated water samples with diethyl ether followed by direct fluorimetric analysis of extracts. The excitation spectra of both compounds in diethyl ether are recorded between 200 and 290 nm, with the emission wavelength at 306 nm. The first-derivative spectra were calculated, measuring the analytical signal for BPA at 239 nm. The concentration range over which the method was applied was 0.5-10.0 microg.l(-1) of BPA with relative standard deviations of 2.9% for a concentration of 4.0 microg.l(-1) of BPA. The detection limit was 0.07 microg.l(-1). The proposed method was applied satisfactorily to the determination of BPA in synthetic mixtures and water samples from different sources previously spiked with different amounts of these chemicals. Recovery values ranging from 93% to 112% were obtained for water samples.

The Use of β-Cyclodextrin Inclusion Complexes for the Analysis of Bisphenol a Residues in Water by Spectrofluorimetry

Abstract The application of β-cyclodextrin inclusion complexes to determine trace levels of bisphenol A (BPA) in aqueous solution by spectrofluorimetry was investigated. A 1:1 stoichiometry of the host-guest complex between β-CD and BPA, as well as the association constant was determined by using the changes in the fluorescence of BPA that occur when it is included in the hydrophobic cyclodextrin cavity. A simple and sensitive spectrofluorimetric method for the determination of BPA residues is presented; the applicable concentration range was 10.0 to 200.0 μgL−1. The detection limit obtained was 0.5 μg.L−1. The accuracy of the proposed method, was checked in the analysis of water samples from different sources previously spiked with different amounts of BPA.

Simple Multiresidue Determination of Fluoroquinolones in Bovine Milk by Liquid Chromatography with Fluorescence Detection

Abstract A simple and sensitive method for the simultaneous determination of five fluoroquinolones (ciprofloxacin, enrofloxacin, danofloxacin, difloxacin, and sarafloxacin) in bovine milk was developed. Protein precipitation from milk samples was achieved by the addition of acetonitrile and o‐phosphoric acid. Acetonitrile was removed with dichloromethane, leaving the fluoroquinolones in the acid aqueous extract. The aqueous extract was analyzed by liquid chromatography with fluorescence detection (LC–FD). The mobile phase was composed of acetonitrile and 10 mM citrate buffer solution of pH 4.5, with an initial composition of acetonitrile‐water (12∶88, v/v) and using linear gradient elution. Norfloxacin was used as an internal standard. The limits of detection found ranged from 1 to 6 ng · mL−1 and were below the maximum residue limits (MRLs) established by the European Union. The proposed method was applied to the determination of these compounds in different bovine milk samples. Method validation was carried out by a recovery assay.

Trace determination of phenol, bisphenol A and bisphenol A diglycidyl ether in mixtures by excitation fluorescence following micro liquid–liquid extraction using partial least squares regression

The determination of phenol, bisphenol A and bisphenol A diglycidyl ether in mixtures was carried out by recording excitation fluorescence spectra between 245 and 290 nm with an emission wavelength of 306 nm. The proposed method involves a micro liquid–liquid extraction of sodium chloride saturated water samples with diethyl ether followed by direct fluorimetric analysis of the extracts in a 10 mm quartz cell with a 2 mm inside width and a volume of 400 µl. The excitation–emission spectra of these compounds overlap considerably, which does not permit their direct determination without previous separation by conventional methodologies. A method is proposed for the determination of these compounds by the use of a full-spectrum multivariate calibration method, partial least squares (PLS). A comparison between two PLS algorithms with different pre-processing methodologies was made. The experimental calibration matrix was designed with 19 samples. The concentrations were varied between 3.0 and 18.0 µg l–1 for phenol, 3.0 and 13.0 µg l–1 for bisphenol A and 5.0 and 30.0 µg l–1 for bisphenol A diglycidyl ether. The cross-validation method was used to select the number of factors. The proposed method, which applied the PLS-1 model with mean centred data, was used for the determination of these compounds in previously spiked water. The predicted concentrations were satisfactory in all cases.

Determination of bisphenol-a and related compounds in human saliva by gas chromatography—mass spectrometry

SummaryA simple and sensitive method for the determination of trace amounts of bisphenol-A (BPA), bisphenol-A diglycidyl dimethacrylate (bis-GMA), bisphenol-A dimethacrylate (bis-DMA) and triethyleneglycol dimethacrylate (TEGDMA) in human saliva is proposed. These materials are used in dental restorations, as composites and sealants, and are sometimes detected in human saliva after dental treatment. The proposed method involves protein precipitation using acetonitrile followed by acidification, evaporation of the solvent and dissolution with dichloromethane prior to injection into a GC-MS.Thermal derivatization in the injection system was used for the identification and quantification of bis-GMA. Clean-up is not necessary using SIM mode. Bisphenol-F (BPF) was used as internal standard. The linear range was 15 to 1000 μg·L−1 for BPA, 50 to 10 000 μg·L−1 for bis-GMA, 50 to 1000 μg·L−1 for bis-DMA and 1 to 100 μg·L−1 for TEGDMA.The detection limits were 3,15,10 and 0.3 μg·L−1 for BPA, bis-GMA, bis-DMA and TEGD-MA, respectively. Validation of the proposed method was carried out by using the standard addition methodology.Samples of 10 mL of human saliva collected 1 h after dental treatment were analysed in order to assess the applicability of the method to detect and quantify such compounds originated from methacrylic resins used in odontological treatment.

Determination of Sulfophenyl Carboxylic Acids in Agricultural Groundwater Samples by Liquid Chromatography with Fluorescence Detection

Abstract We have developed an analytical method to determine six sulfophenyl carboxylic acids (SPC) in agricultural groundwater samples. It involves a solid-phase extraction (SPE) procedure and subsequent separation and determination using liquid chromatography with fluorescence detection (LC–FD).The quantification limits ranged between 0.7 and 1.2 ng ml−1. The proposed method was proved satisfactorily for the detection and determination of these compounds in groundwater samples during a study into the biodegradation of linear alkylbenzene sulfonates (LAS) in an agricultural soil sampled from the irrigated plain to the west of Granada (Spain).