Wang-Hsien Ding

Analysis of nonylphenol polyethoxylates and their degradation products in river water and sewage effluent by gas chromatography-ion trap (tandem) mass spectrometry with electron impact and chemical ionization

A method is presented for the analysis of nonylphenol polyethoxylate (NPEO) residues and their degradation products, nonylphenol polyethoxy carboxylates and carboxyalkylphenol ethoxy carboxylates, in the samples of river water and sewage effluent. The method involves extraction of the samples by graphitized carbon black (GCB) cartridge, propylation by a propanol/acetyl chloride derivatization procedure, and separation, identification and quantitation by ion-trap GC-MS with electron impact ionization (EI), liquid-chemical ionization (CI) and CI-MS-MS modes. The large-volume injection technique provides high precision and sensitivity for both NPEO residues and their degradation products, to quantitation at > or = 0.01 microgram/l in 100 ml of water samples. Dicarboxylic acids of NPEO residues were identified by the CI-MS-MS technique with relatively high concentrations in the samples of river water and sewage effluent. Recovery of nonylphenol and octylphenoxyacetic acid in spiked water samples ranged from 81 to 107%. Relative standard deviations of replicate analyses ranged from 2 to 12%.

Occurrence and concentrations of aromatic surfactants and their degradation products in river waters of Taiwan

The preliminary results of a study on the concentrations of aromatic surfactants (nonylphenol polyethoxylates (NPEO) and linear alkylbenzene sulfonates (LAS)) and their degradation products in river waters of Taiwan were undertaken to establish environmental concentrations and to support surface water protection programs. The analytes were determined by ion-trap GC/MS in EI and CI modes after concentration onto graphitized carbon black (GCB) solid phase extraction columns. The highest concentrations of NPEO and their degradation products (total 1,100 μg/L) were recorded in the river downstream of the effluent discharge from the industrial parks. However, the highest concentrations of LAS (135 μg/L) were determined in the samples from downtown where the municipal wastewaters were discharged directly into the river.

Analysis of chlorophenoxy acid herbicides in water by large-volume on-line derivatization and gas chromatography-mass spectrometry

This work presents a modified method to analyze chlorophenoxy acid herbicides in water samples. The herbicides 2,4-D (2,4-dichlorophenoxyacetic acid). Silvex (2,4,5-trichlorophenoxypropionic acid) and 2,4,5-T (2,4,5-trichlorophenoxyacetic acid) were used to evaluate the method. The method involves extraction of samples by a graphitized carbon black cartridge, and on-line derivatization in the GC injection port using a large-volume (10-20 microl) direct sample introduction (DSI) device with tetraalkylammonium salts. The analytes were then identified and quantitated by ion-trap gas chromatography-mass spectrometry. The large-volume DSI injection-port derivatization technique provides sensitivity, fast and reproducible results for chlorophenoxy acid herbicides residues, to quantitation at 0.1 to 0.2 microg/l in 500-ml water samples. An enhanced characteristic mass chromatogram of molecular ions of butylated chlorophenoxy acid herbicides with a significant chlorine isotope pattern by electron impact ionization MS allows us to determine herbicides residues at trace levels in aqueous samples. Recovery of the herbicide residues in spiked various water samples ranged from 70 to 99% while RSDs ranged from 1 to 13%.

Application of pressurized liquid extraction followed by gas chromatography-mass spectrometry to determine 4-nonylphenols in sediments.

A time- and solvent-saving method, pressurized liquid extraction (PLE), to extract 4-nonylphenol (4-NP) in sediment was developed. The effects of various operational parameters (i.e., temperature, pressure, etc.) for the quantitative extraction of 4-NP by PLE were investigated. The analytes were then identified and quantitated by a large-volume injection GC-MS technique. The 4-NP can be completely extracted by methanol at 100 degrees C and 100 atm combined with 15 min static and then 10 min dynamic extraction steps (1 atm = 101,325 Pa). Recovery of 4-NP in spiked blank kaolin samples was 98% with 5% RSD. The degrees of recovery of 4-NP in the spiked sediment samples from a reservoir and a polluted river were 111% with 4% RSD and 106% with 5% RSD, respectively. The perfect applicability of PLE for 4-NP was determined after testing it with spiked and aged samples. The extraction efficiency of the PLE was compared with conventional Soxhlet and bath ultrasonication extraction methods using the spiked sediment samples.

Fast determination of synthetic polycyclic musks in sewage sludge and sediments by microwave-assisted headspace solid-phase microextraction and gas chromatography-mass spectrometry

One-step in situ microwave-assisted headspace solid-phase microextraction (MA-HS-SPME) followed by gas chromatography-mass spectrometry (GC-MS) analysis is presented as a fast and solvent-free technique to determine synthetic polycyclic musks in sewage sludge and sediment samples. Six synthetic polycyclic musks (galaxolide (HHCB), tonalide (AHTN), celestolide (ADBI), traseolide (ATII), cashmeran (DPMI) and phantolide (AHMI)) were selected in the method development and validation. The effects of extraction parameters for the quantitative extraction of these analytes by one-step MA-HS-SPME were systematically investigated. The dewatered solid sample mixed with 20-mL deionized water (containing 3 g of NaCl in a 40-mL sample-vial) was efficiently extracted by a polydimethylsiloxane-divinylbenzene (PDMS-DVB) fiber placed in the headspace when the extraction slurry was microwave irradiated at 80 W for 5 min. The limits of detection (LODs) ranged from 0.04 to 0.1 ng/g, and the limits of quantification (LOQs) ranged from 0.1 to 0.3 ng/g (fresh weight). A preliminary analysis of sludge and sediment samples revealed that HHCB and AHTN were the two most commonly detected synthetic polycyclic musks; using a standard addition method, their total concentrations were determined to range from 0.3 to 10.9 ng/g (fresh weight) with relative standard deviation (RSD) ranging from 4% to 10%.

Using liquid chromatography-ion trap mass spectrometry to determine pharmaceutical residues in Taiwanese rivers and wastewaters.

To establish their environmental concentrations and to support surface water protection programs, we have undertaken a preliminary study of the concentrations of selected acidic and neutral pharmaceutical residues (clofibric acid, ketoprofen, ibuprofen, diclofenac and carbamazepine) in Taiwanese river and wastewater samples. These pharmaceutical residues were extracted from the water samples through the Oasis HLB solid-phase extraction (SPE). The analytes were then identified and quantified using liquid chromatography-ion trap mass spectrometry with dual-polarity electrospray ionization in the product ion scan mode. The limits of quantification (LOQs) ranged between 0.5 and 20 ngl(-1) for 250 ml samples of water. We investigated the intra- and interbatch precision and accuracy at two levels of concentration. The selected analytes were detected at concentrations ranging from <0.5 to 960 ngl(-1) in wastewater treatment plant effluents and river water samples.

Determination of melamine and cyanuric acid in powdered milk using injection-port derivatization and gas chromatography-tandem mass spectrometry with furan chemical ionization

A reliable, sensitive and eco-friendly injection-port trimethylsilylated (TMS) derivatization and gas chromatography-tandem mass spectrometry (GC-MS/MS) with furan chemical ionization (furan-CI) method was developed to determine melamine and cyanuric acid in powdered milk samples. The effects of several parameters related to the TMS-derivatization process (i.e., injection-port temperature, residence time and volume of silylating agent) and of various CI agents were investigated. Addition of a solution (3 μL) of bis(trimethyl)silyltrifluoroacetamide (BSTFA) containing 1% trimethylchlorosilane (TMCS) reagent to a 20-μL extract from the powdered milk sample gave an excellent yield of the tris-TMS-derivatives of melamine and cyanuric acid at an injection-port temperature of 90°C. Furthermore, using furan as the CI agent in conjunction with tandem mass spectrometry provided the greatest sensitivity and selectivity of detection. The limits of quantitation (LOQs) for melamine and cyanuric acid were 0.5 and 1.0 ng/g in 0.5-g of powdered milk samples, respectively. The recoveries from spiked samples--after simple ultra-sonication with 5% dimethyl sulfoxide in acetonitrile coupled with n-hexane liquid-liquid extraction--ranged from 72% to 93% with relative standard deviations of lower than or equal to 18%. In three of four real powdered milk samples, melamine was detected at concentrations ranging from 36 to 1460 ng/g; and cyanuric acid was detected in two of these samples at concentrations of 17 and 180 ng/g.

Determination of estrogenic compounds in wastewater using liquid chromatography-tandem mass spectrometry with electrospray and atmospheric pressure photoionization following desalting extraction.

Two complementary LC-MS ionization methods, electrospray (ESI) and atmospheric pressure photoionization (APPI), have been optimized to determine three natural estrogenic compounds (estrone, 17beta-estradiol and estriol) and two synthetic estrogenic compounds (17alpha-ethynylestradiol and diethylstilbestrol) in the influent and effluent of wastewater treatment plants (WWTPs). The wastewater samples were first subjected to solid-phase extraction coupled with desalting extraction to remove matrix interference. The analytes were then detected using liquid chromatography-tandem mass spectrometry (LC-MS-MS) with ESI and dopant-assisted (DA) APPI to evaluate the ion suppression effect and to complement the detection and quantification of estrogenic compounds in complex wastewater samples. The average ion suppression factors for the extracts of the WWTP influent analyzed using ESI and APPI were 52+/-5% and 27+/-7%, respectively. The sensitivity and ionization efficiency of the LC-ESI-MS-MS system decreased dramatically when a complex matrix was present in the WWTP influent sample. Estrogenic compounds could be detected in the WWTP influent and effluent samples at concentrations below the parts-per-billion level. The lower detection limits obtained when using ESI and the higher matrix tolerance of the APPI method allowed the complete quantification of estrogenic compounds in very complex samples in a complementary manner.

Determination of volatile N-nitrosamines in meat products by microwave-assisted extraction coupled with dispersive micro solid-phase extraction and gas chromatography - Chemical ionisation mass spectrometry

A sensitive procedure, microwave-assisted extraction (MAE) coupled dispersive micro solid-phase extraction (D-μ-SPE), was developed to extract N-nitrosodimethylamine (NDMA) and other six volatile N-nitrosamines (NAms) from meat products. Parameters affecting the efficiency of MAE and D-μ-SPE were systematically investigated. For MAE, 5-g of a homogenised meat sample was extracted with 30 mL of a sodium hydroxide (0.025 M) solution at 100 °C for 10 min. The optimum D-μ-SPE conditions were immersing 100mg of Carboxen™ 1000 adsorbent in the MAE extract. After vigorously shaking for 30 min, the NAms were then desorbed by treatment with 200 μL of dichloromethane. A 10 μL aliquot was determined by gas chromatography with chemical ionisation mass spectrometry (GC-CI-MS) using the selected-ion-storage (SIS) mode. The limits of quantitation (LOQs) were 0.03-0.36 ng/g. Preliminary results revealed that NDMA was present in the highest concentration, ranging from 0.8 to 3.2 ng/g.

Determination of linear alkylbenzenesulfonates and their degradation products in water samples by gas chromatography with ion-trap mass spectrometry

A method was developed for the analysis of linear alkylbenzenesulfonates (LAS) and their degradation products, sulfophenylcarboxylic acids (SPC), in samples of sewage effluent and river water. This method involved extraction of the samples by graphitized carbon black cartridge, esterification by a two-step thionyl chloride-trifluoroethanol derivatization procedure, and separation, identification and quantitation by ion-trap GC-MS with EI and low pressure CI modes. High selectivity with few signals was observed in the low pressure CI mass spectra of LAS and SPC. Enhanced sensitivity with protonated molecular ion chromatograms of homologous C10-C13 LAS by CI-MS permit the determination of LAS and SPC at trace concentrations in environmental samples. Recovery rates of LAS and SPC in spiked water samples ranged from 75 to 112% with R.S.D. values from 3 to 26%. The limit of quantitation for both LAS and SPC was estimated to be 0.01 microgram/l in 100 ml of water sample.