A combination of statistical and analytical evaluation methods as a new optimization strategy for the quantification of pharmaceutical residues in sewage effluent

In this study, a new solid-phase microextraction (SPME) method for simultaneous extraction of pharmaceutical compounds with acidic and basic characteristics (ibuprofen, fenoprofen, diclofenac, diazepam and loratadine) from residual water samples is proposed. In this procedure, the extraction is processed using two distinct sample pH values. The extraction is begun at pH 2.5 to promote the sorption of acidic pharmaceuticals and after 35 min the sample pH is changed to 7.0 by adding 0.4 mol L⁻¹ disodium hydrogenphosphate, so that the basic compounds can be sorbed by the fiber (20 min). The pH change is performed without interruption of the extraction process. A comparison between the proposed method and the SPME method applied to each group of the target compounds was performed. Gas chromatography coupled to mass spectrometry was used for separation and detection of analytes. The extraction conditions for the three methods were optimized using full factorial experimental design, response surface through a Doehlert matrix and central composite design. Limits of detection (0.02-0.43 μg L⁻¹) and correlation coefficients (0.9970-0.9998) were determined for the three methods. The proposed extraction procedure was applied to samples of sewage treatment plant effluent and untreated wastewater. Recovery and relative standard deviation values ranged from 67 to 116% and 4.6 to 14.5%, respectively, for all compounds studied. Modification of sample pH during the extraction procedure was shown to be an excellent option for all of the compounds and may be extended to the simultaneous extraction of other compounds with different acid-base characteristics.     

Determination of organic priority pollutants in sewage treatment plant effluents by gas chromatography high-resolution mass spectrometry

In this work, we report the development and validation of an analytical method for the trace level determination of 14 selected (EU-directive) priority organic pollutants (namely, 1,2,3-trichlorobenzene (1,2,3-TCB), 1,2,4-trichlorobenzene, 1,3,5-trichlorobenzene, hexachloro-1,3-butadiene, pentachlorobenzene, hexachlorobenzene, alachlor, α-hexachloro-cyclohexane (α-HCH), β-HCH, γ-HCH (lindane), δ-HCH, tetra-brominated diphenyl ether (tetra-BDE), penta-brominated diphenyl ether and hepta-brominated diphenyl ether) in wastewater samples from 5 different sewage treatment plants (STPs) located in Spain. The proposed methodology is based on liquid-liquid extraction with n-hexane followed by identification and confirmation of the selected pollutants by gas chromatography high-resolution mass spectrometry in selected ion recording acquisition mode. Recovery studies performed with spiked wastewater samples at two different concentration levels (0.1 and 1 μg L⁻¹) gave mean recoveries in the range 80-120% (except for trichlorobenzenes, ca. with 50%) with RSD values below 10% in most cases, thus confirming the usefulness of the proposed methodology for the analyses of this kind of complex samples. The obtained detection limits in effluent wastewater matrices were in the low nanogram per liter range, with values as low as 0.09 ng L⁻¹ for tetra-BDE and 0.3 ng L⁻¹ for hexachlorobenzene. Finally, the proposed methodology was successfully applied to a monitoring study intended to characterize wastewater effluents of 5 different sewage treatment plants with different major activities (Industrial, Coastal, Urban). Most of the compounds targeted were detected in the ng L⁻¹ range at concentrations ranging from 0.19 ng L⁻¹ to 135 ng L⁻¹ (hexachlorobenzene).     

Solid-phase microextraction—Gas chromatography to determine volatile organic sulfur compounds in the air at sewage treatment plants

Solid-phase microextraction (SPME) was applied to the determination of 7 volatile organic sulfur compounds (VOSCs), which were analysed by gas chromatography-mass spectrometry. The compounds studied were ethyl mercaptan (CH₃CH₂SH), dimethyl sulfide ((CH₃)₂S), carbon disulfide (CS₂), propyl mercaptan (C₃H₈S), butyl mercaptan (C₄H₁₀S), dimethyl disulfide ((CH₃)₂S₂) and 1-pentanethiol (C₅H₁₂S). Temperature and time conditions of SPME extraction were optimised and the method was validated, with good linearity in a calibration range between 0.1 and 1000 μg m⁻³. Method detection limits ranged between 0.01 and 0.08 μg m⁻³ and method quantification limits were between 0.10 and 0.25 μg m⁻³, allowing real samples taken from several different areas of a sewage treatment plant to be analysed. Repeatability of the method between samples went from 5.6% for pentanethiol up to 14.2% for carbon disulfide, and concentrations of total target compounds were found between 18 and 529 μg m⁻³, depending on the sampling site.     

液相色谱-串联质谱法测定污水处理厂水样中双酚A、四溴双酚A及烷基酚类化合物

近年来,双酚A、四溴双酚A及烷基酚类化合物由于其对水生生物的内分泌干扰作用受到越来越广泛的关注。污水处理厂是处理这类化合物的重要途径,研究目标物在其中的浓度分布对于探明此类物质在环境中的暴露水平具有重要意义,而建立相应的分析测定方法则是开展上述研究的基础。本研究建立了同时测定污水处理厂水样中双酚A、四溴双酚A及6种烷基酚类化合物的反相液相色谱-电喷雾串联质谱分析方法。结果发现,以ZORBAX Eclipse Plus C18色谱柱（150 mm×2.1 mm,3.5 μm）为分离柱,乙腈和0.02%（v/v）氨水溶液为梯度洗脱的流动相,电喷雾质谱负离子模式下目标化合物在11 min内分离;在1~100 μg/L范围内,双酚A、四溴双酚A及6种烷基酚类化合物的峰面积与质量浓度的线性关系良好（R²≥0.998）,方法定量限为2.0~20 ng/L;添加水平分别为0.2、2、20 μg/L时,目标化合物的平均回收率分别为64.3%~118.0%、65.9%~100.5%、70.3%~102.7%,相对标准偏差均小于7.1%。基于上述方法,对江苏省某工业园区污水处理厂水样中相关物质进行检测,出水中检出5种目标化合物,质量浓度范围为11.9~3015.3 ng/L。结果表明,该方法准确可靠、灵敏度高,适用于污水处理厂水样中相关烷基酚类化合物的检测。     

A method for the analysis of sucralose with electrospray LC/MS in recipient waters and in sewage effluent subjected to tertiary treatment technologies

A method for the analysis of the artificial sweetener sucralose in sewage water and recipient water was developed. Extraction and clean up was performed with solid-phase extraction utilising Oasis HLB columns. Detection was made by liquid chromatography electrospray mass spectrometry (LC/MS). The triple-quadrupole mass spectrometer was operated in multiple reaction monitoring (MRM) mode. However, ‘pseudo MRM’ was used, a technique where the two quadrupoles monitor the same m/z. The sodium adduct of sucralose was used for quantification, since lower detection limits were obtained as compared to the sucralose quasi-molecular ion in negative ion mode. The two ions with highest intensity in the chlorine isotope pattern were monitored. The reduction of matrix effects with this approach is discussed. The method limit of quantification (MLOQ) for sewage water was 0.2?µg?L^?1, whereas for recipient water MLOQ was 0.02?µg?L^?1. The method was used to analyse effluent samples from an experimental sewage treatment plant (STP) to assess the efficiency of tertiary treatment techniques for removal of sucralose. Filtration through activated carbon was shown to be efficient, while ozonation, advanced oxidation techniques and membrane bioreactors were less efficient. Analyses of receiving waters showed low dilution of sucralose emitted from the STPs.     

Analysis of nitrosamines in water by automated SPE and isotope dilution GC/HRMS Occurrence in the different steps of a drinking water treatment plant, and in chlorinated samples from a reservoir and a sewage treatment plant effluent

A method based on automated solid-phase extraction (SPE) and isotope dilution gas chromatography/high resolution mass spectrometry (GC/HRMS) has been developed for the analysis of nine nitrosamines in water samples. The combination of automated SPE and GC/HRMS for the analysis of nitrosamines has not been reported previously. The method shows as advantages the selectivity and sensitivity of GC/HRMS analysis and the high efficiency of automated SPE with coconut charcoal EPA 521 cartridges. Low method detection limits (MDLs) were achieved, along with a greater facility of the procedure and less dependance on the operator with regard to the methods based on manual SPE. Quality requirements for isotope dilution-based methods were accomplished for most analysed nitrosamines, regarding to trueness (80–120%), method precision (<15%) and MDLs (0.08–1.7 ng/L).Nineteen water samples (16 samples from a drinking water treatment plant {DWTP}, 2 chlorinated samples from a sewage treatment plant {STP} effluent, and 1 chlorinated sample from a reservoir) were analysed. Concentrations of nitrosamines in the STP effluent were 309.4 and 730.2 ng/L, being higher when higher doses of chlorine were applied. N-Nitrosodimethylamine (NDMA) and N-nitrosodiethylamine (NDEA) were the main compounds identified in the STP effluent, and NDEA was detected above 200 ng/L, regulatory level for NDMA in effluents stated in Ontario (Canada). Lower concentrations of nitrosamines were found in the reservoir (20.3 ng/L) and in the DWTP samples (n.d. −28.6 ng/L). NDMA and NDEA were respectively found in the reservoir and in treated and highly chlorinated DWTP samples at concentrations above 10 ng/L (guide value established in different countries). The highest concentrations of nitrosamines were found after chlorination and ozonation processes (ozonated, treated and highly chlorinated water) in DWTP samples.     

Polycyclic aromatic hydrocarbons in the centralized wastewater treatment plant of a chemical industry zone: Removal, mass balance and source analysis

Increased attention has been given to the fate of pollutants such as polycyclic aromatic hydrocarbons (PAHs) introduced to the wastewater treatment plants.Dissolved and adsorbed PAHs were detected in the centralized wastewater treatment plant of a chemical industry zone in Zhejiang Province,China.The most abundant PAHs were the low molecular weight PAHs (e.g.,Acy,Ace,Flu and Phe),accounting for more than 80% of the total 16 PAHs in each treatment stage.Phase partitioning suggested that the removal of PAHs in every treatment stage was influenced greater by the sorption of particles or microorganisms.The removal efficiencies of individual PAHs ranged between 4% and 87% in the primary sedimentation stage,between 1% and 42% in anaerobic hydrolysis stage,between <1% and 70% in aerobic bio-process stage,between 1.5% and 80% in high-density clarifier stage,and between 44% and 97% in the whole treatment process.Mass balance calculations in primary stage showed significant losses for low molecular weight PAHs and relatively good agreements for high molecular weight PAHs as well as in anaerobic hydrolysis,high-density clarifier stage and sludge stream for most PAHs.Great gains of 60%-150% were obtained for high molecular weight PAHs in aerobic bio-process stage due to biosorption and bioaccumulation.Our investigations found that PAHs entering the wastewater treatment plant (WWTP) could be derived from the dyeing chemical processes as the byproducts,and the contribution supported by the largest dyeing chemical group was up to 48%.     

Investigation into the surface selective oxidation of dual‐phase steels by XPS,SAM and SIMS

Surface selective oxides created during continuous annealing (MnO, SiO₂, etc.) can have a deleterious effect on coating adhesion after hot‐dip galvanizing. Earlier research works have made it clear that increasing the annealing atmosphere oxidizing potential can alleviate the problem by reducing external surface selective oxidation. In the present study, increasing the water vapour content of the nitrogen–hydrogen protective gas mixture was used to raise its oxidizing potential. The technique was applied to a classical dual‐phase steel (0.15% C, 1.5% Mn, 0.45% Si, 0.05% Al…) that was annealed for 60 s at 800–810°C in protective atmospheres of nitrogen and 5% hydrogen with water vapour contents ranging from 10 to 6000 ppm. Post‐annealing surfaces were characterized by x‐ray photoelectron spectroscopy (XPS), secondary ion mass spectroscopy (SIMS) and scanning Auger microscopy (SAM). In situ XPS analyses were carried out right after simulation annealing in the preparation chamber connected to the spectrometer, never returning the specimens to air. This made it possible to identify in a reliable way the elements that segregated to the surface during the treatment, and to determine their corresponding oxidation states. On the other hand, the high sensitivity of SIMS was taken advantage of to assess oxide in‐depth concentration profiles (SiO₂, Al₂O₃, FeO) as a function of the annealing conditions, and SAM was used to characterize the corresponding oxide particle morphology. External selective oxidation was thus shown to decrease with increasing water vapour contents in the atmosphere (from 80 to 6000 ppm), whereas internal oxidation increases drastically to ～4 μm below the free surface. At 10 ppm of H₂O the oxygen partial pressure is very low and the external selective oxidation results in a thin, but almost complete, coverage of the steel surface. Consequently, metallic iron cannot be observed at the surface, thus hampering hot‐dip galvanizability, unless the water vapour content is raised to 6000 ppm. Various surface morphologies were observed and discussed. In the authors' opinion, basic investigations of this type are an indispensable first step to improving the response of highly alloyed steels (dual‐phase, TRIP) to hot‐dip galvanizing. Copyright © 2003 John Wiley & Sons, Ltd.     

200 years of practical electroanalytical chemistry: past, present and future directions illustrated by reference to the on-line, on-stream and off-line determination of trace metals in zinc plant electrolyte by voltammetric and potentiometric techniques

The millennium being celebrated this year coincides with the 200th anniversary of the birth of practical electrochemistry made possible via Volta’s publication of the battery in the year 1800. The analytical chemists at the beginning of the 19th century were very quick to take advantage of this newly reported device and the first qualitative electrochemical determination of copper rapidly followed this pioneering discovery. In the last 200 years, electrochemical analysis, in its various forms, has been undertaken routinely in countless laboratories all over the world. However, in view of the long and distinguished history of the discipline, and some limitations that have been identified at the time of the celebration of the millennium, electrochemical analysis is regarded in some quarters as being a mature and conservative discipline whose importance in the future, when faced with severe competition from newly emerging alternative analytical techniques, is somewhat unclear. In this paper, an overview of past and present developments in electroanalytical chemistry and the possible future status of the technique is presented. In particular, emphasis is given to describing applications relevant to the also very mature field of electrowinning of zinc from plant electrolyte. This overview encompasses the author’s 25 years’ experience in developing polarographic, stripping voltammetric, adsorptive stripping voltammetric and ion-selective electrode (ISE) methods of analysis in on-line, on-stream and off-line modes for the determination of elements such as Cd, Pb, Ge, Sb (oxidation states (III) and (V)), Co, Ni, Zn, Fe, (oxidation states (II) and (III)), Tl, As (total) and Cu in zinc plant electrolyte. Developments that may contribute to an important future for analytical voltammetry are also considered as are limitations that could inhibit the extent of practical use of these electroanalytical techniques in the 21st century.     

Palladium‐Catalyzed Aerobic Intermolecular Cyclization of Acrylic Acid with 1‐Octene to Afford α‐Methylene‐γ‐butyrolactones: The Remarkable Effect of Continuous Water Removal from the Reaction Mixture and Analysis of the Reaction by Kinetic,ESI‐MS,and XAFS Measurements

Further study of our aerobic intermolecular cyclization of acrylic acid with 1‐octene to afford α‐methylene‐γ‐butyrolactones, catalyzed by the Pd(OCOCF₃)₂/Cu(OAc)₂ ? H₂O system, has clarified that the accumulation of water generated from oxygen during the reaction causes deactivation of the Cu cocatalyst. This prevents regeneration of the active Pd catalyst and, thus, has a harmful influence on the progress of the cyclization. As a result, both the substrate conversion and product yield are efficiently improved by continuous removal of water from the reaction mixture. Detailed analysis of the kinetic and spectroscopic measurements performed under the condition of continuous water removal demonstrates that the cyclization proceeds in four steps: 1) equilibrium coordination of 1‐octene to the Pd acrylate species, 2) Markovnikov‐type acryloxy palladation of 1‐octene (1,2‐addition), 3) intramolecular carbopalladation, and 4) β‐hydride elimination. Byproduct 2‐acryloxy‐1‐octene is formed by β‐hydride elimination after step 2). These cyclization steps fit the Michaelis–Menten equation well and β‐hydride elimination is considered to be a rate‐limiting step in the formation of the products. Spectroscopic data agree sufficiently with the existence of the intermediates bearing acrylate (Pd? O bond), η³‐C₈H₁₅ (Pd? C bond), or C₁₁H₁₉O₂ (Pd? C bond) moieties on the Pd center as the resting‐state compounds. Furthermore, not only Cu^II, but also Cu^I, species are observed during the reaction time of 2–8 h when the reaction proceeds efficiently. This result suggests that the Cu^II species is partially reduced to the Cu^I species when the active Pd catalytic species are regenerated.     

Synthesis of 1‐Substituted Tetrahydroisoquinolines by Lithiation and Electrophilic Quenching Guided by In Situ IR and NMR Spectroscopy and Application to the Synthesis of Salsolidine,Carnegine and Laudanosine

The lithiation of N‐tert‐butoxycarbonyl (N‐Boc)‐1,2,3,4‐tetrahydroisoquinoline was optimized by in situ IR (ReactIR) spectroscopy. Optimum conditions were found by using n‐butyllithium in THF at ?50 °C for less than 5 min. The intermediate organolithium was quenched with electrophiles to give 1‐substituted 1,2,3,4‐tetrahydroisoquinolines. Monitoring the lithiation by IR or NMR spectroscopy showed that one rotamer reacts quickly and the barrier to rotation of the Boc group was determined by variable‐temperature NMR spectroscopy and found to be about 60.8 kJ mol^?1, equating to a half‐life for rotation of approximately 30 s at ?50 °C. The use of (?)‐sparteine as a ligand led to low levels of enantioselectivity after electrophilic quenching and the “poor man’s Hoffmann test” indicated that the organolithium was configurationally unstable. The chemistry was applied to N‐Boc‐6,7‐dimethoxy‐1,2,3,4‐tetrahydroisoquinoline and led to the efficient synthesis of the racemic alkaloids salsolidine, carnegine, norlaudanosine and laudanosine.     

Application of Ultrasonic Attenuation Measurements in the Studies on Macromolecular Conformational Behaviors

——Phase Behavior of the Aqueous Solution of Poly(vinyl methyl ether) Sensitive to Temperature and the Modification of the Behavior by Using Poly(acrylic acid) The phase behavior of the aqueous solution of poly(vinyl methyl ether) (PVME) sensitive to temperature and the modification of the behavior by using poly(acrylic acid) (PAA) have been studied by ultrasonic attenuation measurements and fluorescence probe techniques. It has been observed that PVME solution is transparent at room temperature and becomes turbid upon heating. The solution turns clear again as soon as the temperature is decreased to room temperature. The heating and cooling process can be repeated for many times. The phase behavior of the solution sensitive to temperature is attributed to the conformational changes of the polymer. PVME may adopt an open coil conformation at room temperature. With this conformation, the polymer is well miscible with the solvent, water, and thereby the system is a real solution. The polymer may adopt a compact coil conformation when the temperature is higher than a specific value, which is called the LCST (the lower critical solution temperature) of PVME. In this case, the polymer tangles to each other and forms various aggregates, which can scatter incident light and ultrasonic waves greatly, resulting in the phase separation. Introduction of PAA decreases the temperature sensitivity of the phase behavior of the polymer. The nature of the inhibition is attributed to the complexation of PAA with PVME and the strong hydrophilicity of PAA. Results from fluorescence probe studies are in accordance with those from ultrasonic attenuation measurements, indicating again that the ultrasonic attenuation method can be successfully used for the qualitative studies of polymer conformations and complexation between polymers.     

Simultaneous determination of metoprolol and its metabolites, α‐hydroxymetoprolol and O‐desmethylmetoprolol,in human plasma by liquid chromatography with tandem mass spectrometry: Application to the pharmacokinetics of metoprolol associated with CYP2D6 genotypes

A rapid and simple LC with MS/MS method for the simultaneous determination of metoprolol and its two CYP2D6‐derived metabolites, α‐hydroxy‐ and O‐desmethylmetoprolol, in human plasma was established. Metoprolol (MET), its two metabolites, and the internal standard chlorpropamide were extracted from plasma (50 μL) using ethyl acetate. Chromatographic separation was performed on a Luna CN column with an isocratic mobile phase consisting of distilled water and methanol containing 0.1% formic acid (60:40, v/v) at a flow rate of 0.3 mL/min. The total run time was 3.0 min per sample. Mass spectrometric detection was conducted by ESI in positive ion selected‐reaction monitoring mode. The linear ranges of concentration for MET, α‐hydroxymetoprolol, and O‐desmethylmetoprolol were 2–1000, 2–500, and 2–500 ng/mL, respectively, with a lower limit of quantification of 2 ng/mL for all analytes. The coefficient of variation for the assay's precision was ≤ 13.2%, and the accuracy was 89.1–110%. All analytes were stable under various storage and handling conditions and no relevant cross‐talk and matrix effect were observed. Finally, this method was successfully applied to assess the influence of CYP2D6 genotypes on the pharmacokinetics of MET after oral administration of 100 mg to healthy Korean volunteers.