Waste toner-derived micro-materials as low-cost magnetic solid-phase extraction adsorbent for the analysis of trace Pb in environmental and biological samples.

Lead (Pb) is a toxic heavy metal and is commonly used in industrial applications. Thus, Pb poisoning is a concerning public health issue worldwide. The amounts of lead in natural water, urine, and blood can serve as significant indicators for monitoring the exposure of Pb poisoning. Waste toner has the characteristics of both "waste" and "resource," as it is a "resource in the wrong place." Here, a low-cost carboxylate-functionalized magnetic adsorbent was first synthesized from waste toner by a simple thermal treatment and served as a novel adsorbent with a flexible multidentate O-donor for pre-concentration of trace Pb. The characterization, adsorption behavior, and various factors of adsorption and desorption were adequately optimized, and prior to graphite furnace atomic absorption spectrometry (GFAAS) detection, a new magnetic solid-phase extraction method was proposed for the analysis of Pb in real environmental water and biological samples. The developed method exhibited a low detection limit (0.003 µg L-1), high enrichment factor (88.6-fold), good linearity (0.01-0.3 µg L-1), satisfactory precision with relative standard deviations of 7.9% (n = 7, CPb = 0.02 µg L-1), fast adsorption kinetics (5 min), and strong ability to overcome matrix interference. Validation was also performed by analyzing a certified standard reference material, and the method was successfully applied to real tap water, lake water, human urine, and human blood serum with satisfactory recoveries of 92.6-109%.

New Strategies for the Simple and Sensitive Voltammetric Direct Quantification of Se(IV) in Environmental Waters Employing Bismuth Film Modified Glassy Carbon Electrode and Amberlite Resin.

An analytical procedure regarding the determination of selenium(IV) by anodic stripping voltammetry exploiting the in situ plated bismuth film electrode is described. Since organics are commonly present in untreated natural water samples, the use of Amberlite XAD-7 resin turns out to be quite important to avoid problems such as the adsorption of these compounds on the working electrode. The optimum circumstances for the detection of selenium in water using differential pulse voltammetry techniques were found to be as follows: 0.1 mol L-1 acetic acid, 1.9 × 10-5 mol L-1 Bi(III), 0.1 g Amberlite XAD-7 resin, and successive potentials of -1.6 V for 5 s and -0.4 V for 60 s, during which the in situ formation of the bismuth film on glassy carbon and the accumulation of selenium took place. The current of the anodic peak varies linearly with the selenium concentration ranging from 3 × 10-9 mol L-1 to 3 × 10-6 mol L-1 (r = 0.9995), with a detection limit of 8 × 10-10 mol L-1. The proposed procedure was used for Se(IV) determination in certified reference materials and natural water samples, and acceptable results and recoveries were obtained.

Sorption behavior of selected chlorophenols onto polyurethane foam treated with iron(III): kinetics and thermodynamic study.

An efficient, selective, and inexpensive method for complete elimination of chlorophenols (CPs) from water has been established. The proposed procedure was based upon the use of n-tributyl phosphate (TBP)-plasticized iron(III) physically immobilized polyurethane foam (PUF) solid sorbent for complete removal of CPs from aqueous media at pH close to 0. The interaction of the complex ion [Fe(C6H5O)6]3- with protonated ether oxygen of the PUF sorbent forms ternary ion associate on/in the PUFs. The retention of 4-chlorophenol (4-C) and 2,4,6-trichlorophenol (TCP) by the TBP-treated iron(III)-immobilized PUF fitted well with the pseudo-second-order kinetic model with a rate constant (k) of 0.04 and 0.15 g (mg min)-1, respectively. The sorption of 4-CP was endothermic whereas the uptake of TCP was favorable at low temperature approving the exothermic and non-spontaneous characteristics of its uptake. The ΔS value for 4-CP reveals good affinity of the ion [Fe(C6H5O)6]3- towards the PUF sorbent.

Online preconcentration by electrokinetic supercharging for separation of endocrine disrupting chemical and phenolic pollutants in water samples.

Online preconcentration using electrokinetic supercharging (EKS) was proposed to enhance the sensitivity of separation for endocrine disrupting chemical (methylparaben (MP)) and phenolic pollutants (2-nitrophenol (NP) and 4-chlorophenol (CP)) in water sample. Important EKS and separation conditions such as the concentration of BGE; the choice of terminating electrolyte (TE); and the injection time of leading electrolyte (LE), sample, and TE were optimized. The optimum EKS-CE conditions were as follows: BGE comprising of 12 mM sodium tetraborate pH 10.1, 100 mM sodium chloride as LE hydrodynamically injected at 50 mbar for 30 s, electrokinetic injection (EKI) of sample at -3 kV for 200 s, and 100 mM CHES as TE hydrodynamically injected at 50 mbar for 40 s. The separation was conducted at negative polarity mode and UV detection at 214 nm. Under these conditions, the sensitivity of analytes was enhanced from 100- to 737-fold as compared to normal CZE with hydrodynamic injection, giving LOD of 4.89, 5.29, and 53 µg/L for MP, NP and CP, respectively. The LODs were adequate for the analysis of NP and CP in environmental water sample having concentration at or lower than their maximum admissible concentration limit (240 and 2000 µg/L for NP and CP). The LOD of MP can be suitable for the analysis of MP exists at mid-microgram per liter level, even though the LOD was slightly higher than the concentration usually found in water samples (from ng/L to 1 µg/L). The method repeatabilities (%RSD) were in the range of 1.07-2.39% (migration time) and 8.28-14.0% (peak area).

Rapid and on-site detection of bisulfite via a NIR fluorescent probe: A case study on the emission wavelength of probes with different quinolinium as electron-withdrawing groups.

The emission of venenous sulfur dioxide (SO2) and its derivatives from industrial applications such as coking, transportation and food processing has caused great concern about public health and environmental quality. Probes that enable sensitivity and specificity to detect SO2 derivatives play a crucial role in its regulations and finally mitigating its environmental and health impacts, but fluorescent probes that can accurately, rapidly and on-site detect SO2 derivatives in foodstuffs and environmental systems rarely reported. Herein, a near-infrared (NIR) fluorescent probe (ZTX) for the ratiometric response of bisulfite (HSO3-) was designed and synthesized by regulating the structure of high-performance HSO3- fluorescent probe SL previously reported by us based on structural analyses, theoretical calculations and related literature reports. The Michael addition reaction between the electronic-deficient C=C bond and HSO3- destroys ZTX's π-conjugation system and blocks its intramolecular charge transfer (ICT) process, resulting in a significant fading of the fuchsia solution and the bluish-purple fluorescence turned light blue fluorescence. Fluorescent imaging of HSO3- in live animals utilizing ZTX has been demonstrated. The quantitative analysis of HSO3- in food samples using ZTXvia a smartphone has been also successfully implemented. Simultaneously, the ZTX-based test strips were utilized to quantificationally determine HSO3- in environmental water samples by a smartphone. Consequently, probe ZTX could provide a new method to understand the physiopathological roles of HSO3-, evaluate food safety and monitor environment, and is promising for broad applications.

[Determination of nine aromatic amines in water by cloud point extraction-gas chromatography-mass spectrometry].

Aromatic amines are a class of compounds bearing amino groups on their benzene rings; these compounds are important raw materials for the industrial production of rubber chemicals, pesticides, dyes, pharmaceuticals, photosensitive chemicals, and agricultural chemicals. Research has revealed that some aromatic amines teratogenetic, carcinogenic, and mutagenic properties. Given the high toxicity and potential harm caused by aromatic amines, monitoring their levels in water sources is critical. Aromatic amines are among the 14 strategic environmental pollutants blacklisted in China, and assessing their exposure levels is essential for protecting human health and the environment. At present, the standard method for detecting aromatic amines in water is liquid-liquid extraction-gas chromatography-mass spectrometry (LLE-GC-MS). However, this method has the disadvantages of large sample size requirement, complex operation, long analysis time, and high reagent consumption. In this study, instead of traditional LLE technology, cloud point extraction (CPE) technology was used in combination with GC-MS to establish an efficient, sensitive, and environment-friendly method for the detection of nine aromatic amines, namely, 2-chloramine, 3-chloramine, 4-chloramine, 2-nitroaniline, 3-nitroaniline, 4-nitroaniline, 1-naphthylamine, 2-naphthylamine, and 4-aminobenzene, in water. Triton X-114 was used as the extraction agent. The main experimental parameters were optimized using a single-factor optimization method. The aromatic amines in various water samples were quantitatively analyzed using GC-MS. The nine aromatic amines were separated on a DB-35 MS capillary column (30 m×0.25 mm×0.25 µm). The mass spectrometer was operated in selected ion monitoring (SIM) mode, and quantitative analysis was performed using the internal standard method. The results demonstrated that all nine aromatic amines could be completely separated within 16 min and had good linearities within accurate mass concentration ranges, with correlation coefficients (R2) greater than 0.998. The limits of detection (LODs) and quantification (LOQs) of these aromatic amines in water were 0.12-0.48 and 0.40-1.60 µg/L, respectively. The accuracy and precision of the method were assessed via the determination of aromatic amines in surface water of drinking water sources, offshore seawater, wastewater of the typical printing and dyeing industry at levels of 2.0 and 10.0 µg/L. The recoveries of the aromatic amines in surface water of drinking water sources were 81.1%-109.8%, with intra-day and inter-day relative standard deviations (RSDs) of 0.7%-5.2% (n=6) and 1.6%-6.2% (n=3), respectively. The recoveries of the aromatic amines in offshore seawater were 83.0%-115.8%, with intra-day RSDs (n=6) of 1.5%-8.6% and inter-day RSDs (n=3) of 2.4%-12.2%. The recoveries of the nine aromatic amines in wastewater of the typical printing and dyeing industry were 91.0%-120.0%, with intra-day RSDs (n=6) of 2.9%-12.9% and inter-day RSDs (n=3) of 2.5%-13.1%. The established method was used to detect nine aromatic amines in actual water samples. No aromatic amines were detected in the surface water of drinking water sources or offshore seawater samples. However, 2-chloramine, 4-chloramine, and 4-aminobenzene, which are frequently used in the printing and dyeing industry, were detected in the wastewater of the typical printing and dyeing industry samples. The proposed method offers the advantages of simple operation, high sensitivity, low cost, low organic reagent requirement, and good repeatability. Thus, this method provides reliable technical support for studying the residual status and environmental behavior of aromatic amines in water.

[Determination of trace perfluorinated compounds in environmental water samples by dispersive solid- phase extraction-high performance liquid chromatography-tandem mass spectrometry using carbon nanotube composite materials].

In this work, carbon nanotubes (CNTs) on silica rod (SiO2) composite materials were prepared to extract six perfluorinated compounds (PFCs) in real environmental water samples by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The as-synthesized sorbents, hereafter referred to as CNT@SiO2, were employed for dispersive solid-phase extraction (d-SPE). Perfluoroheptanoic acid (PFHpA), perfluorohexane sulfonate (PFHxS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorooctane sulfonate (PFOS), and perfluorodecanoic acid (PFDA) were selected as target analytes. The main extraction parameters were systematically optimized using the single-factor optimization method. The optimum adsorption parameters were as follows: adsorption time of 30 min, sorbent amount of 10 mg, pH 6 and NaCl concentration of 1.7 mol/L for sample solution, and 4 mL acetone as desorption solvent, desorption for 4 min. LC-triple quadrupole MS was conducted to quantify the selected PFCs in water samples. The mobile phase was 5 mmol/L ammonium acetate and methanol, the flow rate was set to 0.4 mL/min, the column temperature was set to 40 ℃, and the injection volume was 5.0 µL. The chromatographic separation system was equipped with a Kinetex C18 column (100 mm×2.1 mm, 1.7 µm). The mass spectrometer was operated with negative electrospray ionization in multi-reaction monitoring mode. CNT@SiO2 was prepared in five batches and used as the d-SPE sorbent, and the relative standard deviations (RSDs) of the PFC recoveries among these five batches ranged from 4.9% to 9.3%. The reusability of the CNT@SiO2 sorbent was assessed. After eight d-SPE cycles using the same sorbent, the RSDs of the PFC recoveries were 3.7%-8.2%. These results indicated that the sorbent had good stability and reusability for d-SPE. Excellent results were achieved under optimal extraction conditions. The method validation results indicated that the linear ranges were 0.4-1000 ng/L for PFNA, PFOS, and PFDA, 0.9-1000 ng/L for PFHpA, 0.7-1000 ng/L for PFHxS, and 0.6-1000 ng/L for PFOA. The correlation coefficients were 0.973-0.997. The limit of detection (LOD) and limit of quantification of the method were 0.10-0.26 ng/L and 0.33-0.87 ng/L, respectively. At 20 ng/L, the RSDs of the intra- and inter-day precisions were 2.73%-7.75% and 3.38%-8.21%, respectively. At 100 ng/L, the RSDs of the intra- and inter-day precisions were 2.95%-8.46% and 4.16%-9.14%, respectively. Finally, at 500 ng/L, the RSDs of the intra- and inter-day precisions were 2.51%-7.48% and 3.59%-9.63%, respectively. The developed method was applied to analyze six PFCs in tap water, barreled drinking water, and river water samples. PFOA and PFOS were determined in tap water at mass concentrations of 5.6 and 8.7 ng/L, respectively. No PFCs were found in barreled drinking water and river water. Satisfactory recoveries of 72.1%-109.6% at low, middle, and high spiking levels were also obtained. In conclusion, the d-SPE-LC-MS/MS method based on CNT@SiO2 composite sorbents is accurate and sensitive. The results of this study demonstrate that CNT@SiO2 is a good choice for the rapid and effective determination of PFCs from water samples. Further exploration of the use of CNT@SiO2 sorbents for the extraction and determination of trace organic pollutions in environmental samples is in progress.

An anion exchange pretreatment method for the determination of low-level uranium in the environmental water samples.

Uranium in environmental water is usually at trace or ultra-trace levels with high concentrations of background ions so that the detection of uranium often couples with pretreatment processes to lower the detection limit, and improve the selectivity and accuracy of instruments. A simple, green, effective and efficient anion exchange pretreatment method was proposed to favor the determination of low-level uranium in natural environmental water samples. To determine the applicability and obtain the optimum operating parameters, the effects of coprecipitation, pH, contact time, uranium concentration, background ions, eluent and the flow speed on the uranium recovery were investigated. The experimental results showed that the proper addition of saturated Na2CO3 solution for pH adjustment did not lead to uranium loss in natural water samples, and the optimum pH value for adsorption was determined from 6 to 8. The adsorption speed was improved a lot with the employment of a novel silica-supported anion exchange resin, which also showed good linear dependence in the concentration range from <0.5 µg/L to 1000 µg/L with high tolerance limits towards common background ions. The optimum eluent was determined as 1 M HNO3, and the optimum flow speeds for adsorption and desorption were about 4.0 and 1.0 mL/min, respectively. Based on these results, a pretreatment process was finally established, which realized the quantitative recovery of uranium from six different natural water samples with the chemical yields exceeding 95% and the enrichment factors about 100 times.

Organophosphorus pesticides extraction with polyvinyl alcohol coated magnetic graphene oxide particles and analysis by gas chromatography-mass spectrometry: Application to apple juice and environmental water.

In this study, we synthesized, characterized the magnetic graphene oxide coated with polyvinyl alcohol (PVA@MGO), and used it as an adsorbent for the magnetic solid-phase extraction (MSPE) of organophosphorus pesticides (OPPs) residue in the apple juice and environmental water samples followed by gas chromatography-mass spectrometry (GC-MS) analysis. Effective factors on the extraction efficiency, including the adsorbent dosage, desorption conditions, sample pH, extraction and desorption time, and ionic strength were optimized. The dynamic range of the MSPE-GC-MS method was obtained in the concentration range of 0.07-500 ng mL-1 OPPs with the limits of detection (LODs) in the range of 20-80 pg mL-1. Also, the intra- and inter-day precisions were determined to be in the range of 3.3-5.7% and 5.9-8.2%. The relative recoveries of pesticides for spiked real water samples and apple juice were in the range of 94.5 and 107.1%, with relative standard deviations between 2.6 and 6.5%. These results propose that the PVA@MGO is appropriate for simultaneous determination and high throughput analysis of OPPs residues.

Potential of Carboxymethylated Polyallylamine as a Functional Group on Chelating Resin for Solid-Phase Extraction of Trace Elements.

New chelating resins immobilizing carboxymethylated polyallylamine (CM-PAA) were prepared by immobilizing PAAs with some molecular weights on methacrylate resins and then carboxymethylating a part of amino groups in the PAAs using various amounts of sodium monochloroacetate. The molecular weight of PAA barely affected both the amount of PAA immobilized on the resin and the relationship between the carboxymethylation (CM) rate and the ratio of the amount of monochloroacetate used in the CM step. The selectivity of CM-PAA resin for solid-phase extraction of trace elements was almost the same as that of a resin immobilizing carboxylymethylated polyethyleneimine; 10 elements, namely Cd, Co, Cu, Fe, Mo, Ni, Pb, Ti, V, and Zn, could be quantitatively recovered over a wide pH range and alkali and alkaline earth elements were scarcely extracted under acidic and neutral conditions. The CM-PAA resin was applicable to the separation and preconcentration of the elements in a certified reference material (Waste Water, EU-L-1) and a real environmental water sample (ground water).

Molecular characteristics and genotypic diversity of enterohaemorrhagic Escherichia coli O157:H7 isolates in Gauteng region, South Africa.

Enterohaemorrhagic Escherichia coli (EHEC) O157:H7 is one of the major foodborne and waterborne pathogens causing severe diseases and outbreaks worldwide. There is scarcity of EHEC O157:H7 data in South Africa. This study was carried out to determine the molecular characteristics and genotypic diversity of EHEC O157:H7 isolates in the Gauteng region, South Africa. Samples were cultured on selective chromogenic media. Antibiotic susceptibility profile of isolates was determined using the VITEK®-2 automated system. Isolates were characterised using multiplex PCR assays and the genetic diversity was determined using pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). A total of 520 samples of which 270 environmental water samples and 250 stool specimens were collected and analysed. Overall, EHEC O157:H7 was recovered from 2.3% (12/520) of samples collected. Environmental water samples and clinical stool specimens showed a prevalence of 4.07% (11/270) and 0.4% (1/250) respectively. Antibiotic susceptibility profile varied from isolates with full susceptibility to isolates with resistance to multiple antibiotics. Most resistance was detected to the penicillins, specifically ampicillin (7/12), amoxicillin (3/12) and piperacillin/Tazobactam (3/12) followed by one of the folate inhibitors, trimethoprim (3/12) and the carbapenems, imipenem and meropenem (2/12) each. Three isolates harboured a combination of Shiga-toxins (Stx)-2, intimin (eae) and enterohaemolysin (hlyA) genes, while two isolates harboured the Stx-1, Stx-2 and hlyA genes. The PFGE performed showed that EHEC O157:H7 isolates were genetically diverse, with two minor pulsotypes and eight singletons. The MLST analysis identified three sequence types (STs) (ST10, ST11 and ST1204) that have been previously reported associated with outbreaks. The STs identified in this study pose a potential public health risk to consumers of untreated environmental water and closed human contacts. There is necessity to enhance surveillance in reducing the propagation of this bacterium which is a public health problem.

Relationship between the Structure of Ionic Liquid and Its Enrichment Ability To Trace Fungicides from an Environmental Water Sample.

To elucidate the relationship between the structure of ionic liquid (IL) and its enrichment ability to trace pesticides from an environmental water sample, a series of imidazole-based ILs were synthesized to extract four fungicides (boscalid, cyprodinil, fluazinam, and pyrimethanil) through an in situ ionic liquid dispersive liquid-liquid microextraction method. The results showed that aromatic heterocyclic monocation ionic liquids (MILs) had better extraction ability to fungicides than other three alicyclic heterocyclic MILs. Dication ionic liquids (DILs) with the four carbons at the side chain had better ability to extract fungicides than MILs, and DILs with a long bridge carbon chain had better recoveries of fungicides with low Kow values. The proposed method showed high mean enrichment factors and high recoveries of the fungicides from real water samples. The rules of the relationship between the structure of IL and enrichment ability are instructive to the application of ILs in pretreatment of complex substances.

Estimation of Human Norovirus Infectivity from Environmental Water Samples by In Situ Capture RT-qPCR Method.

Human noroviruses (HuNoVs) are highly infectious viruses for which water is an important medium of transmission. In this study, we explored a new in situ capture RT-qPCR (ISC-RT-qPCR) methodology to estimate the infectivity of HuNoV in environmental water samples. This assay was based on capturing encapsidated HuNoV by viral receptors, followed by in situ amplification of the captured viral genomes by RT-qPCR. We demonstrated that the ISC-RT-qPCR did not capture and enable signal amplification of heat-denatured Tulane Virus (TV) and HuNoVs. We further demonstrated that the sensitivity of ISC-RT-qPCR was equal or better than that of conventional RT-qPCR procedures for the detection of HuNoV GI and GII. We then utilized the ISC-RT-qPCR to detect HuNoV in environmental water samples for comparison against that from a conventional RT-qPCR procedure. TV was used as a process control virus. While complete inhibition of TV genomic signal was observed in 27% of samples tested by RT-qPCR, no inhibition of TV genomic signal was observed by ISC-RT-qPCR. From 72 samples tested positive for HuNoV GI signal by RT-qPCR, only 20 (27.8%) of these samples tested positive by ISC-RT-qPCR, suggesting that 72.2% of RT-qPCR-positive samples were unlikely to be infectious. From 16 samples tested positive for HuNoV GII signal by RT-qPCR, only one of these samples tested positive by ISC-RT-qPCR. Five samples that had initially tested negative for HuNoV GII signal by RT-qPCR, was tested as positive by ISC-RT-qPCR. Overall, ISC-RT-qPCR method provided an alternative assay to estimate infectivity of HuNoV in environmental samples.

[Dispersive liquid-liquid microextraction based on molecular complexation followed by high performance liquid chromatography for the determination of two phenoxy carboxylic acid herbicides in environmental water samples].

A dispersive liquid-liquid microextraction (DLLME) method based on molecular complexation was developed for the determination of 2,5-dichloro-6-methoxybenzoic acid (dicamba) and 2,4-dichlorophenoxyacetic acid (2,4-D) in environmental water samples by high performance liquid chromatography-ultraviolet detection (HPLC-UV). Tri-n-butylphosphate (TBP) and methanol were selected as the extraction solvent and dispersive solvent, respectively. Parameters affecting the extraction efficiency, including the type and volume of the extraction and dispersive solvents, pH of the sample solutions, pH of the backward extraction solution, and salt addition, were optimized. Under the optimized conditions, the linear range was 0.50-1000 µg/L for the two target herbicides. The limits of detection (LODs, S/N=3) were 0.44 µg/L and 0.49 µg/L for dicamba and 2,4-D, respectively. The enrichment factors (EFs) of dicamba and 2,4-D were 85 and 90, respectively. The recoveries were in the range 75.7%-104.0%. The proposed microextraction involved molecular complexation, and the Lewis acid-base interactions between TBP and the acidic herbicides gave satisfactory extraction results. Thus, the method is expected to be a powerful tool for the determination of acidic herbicides in environmental water samples.

[Preparation of MIL-53(Fe)@polydopamine@Fe3O4 magnetic composite for magnetic solid-phase extraction of sulfonylurea herbicides in environmental water].

Polydopamine (PDA) and MIL-53(Fe) modified Fe3O4 particles (MIL-53(Fe)@PDA@Fe3O4 magnetic composite) were prepared by simple one-pot solvothermal method. The obtained composite was introduced to rapidly extract four kinds of sulfonylurea herbicides (SUHs) from environmental water samples by magnetic solid-phase extraction (MSPE). Then the herbicides were analyzed by a high performance liquid chromatographic system equipped with a photodiode array detector. The mobile phase was a mixture of acetonitrile and water containing 0.01% (v/v) trifluoroacetic acid, and the detection wavelength was 233 nm. Significant extraction parameters were optimized to improve the extraction efficiency. Under the optimum conditions (5 mL desorption solvent of acetone, 4.5 min extraction time, 60 mg adsorbent dosage, 0.5 g NaCl and the pH 3 of the solution), the developed method showed good linearities with correlation coefficients (r) no less than 0.9980. The limits of detection (LODs, S/N=3) of the four SUHs were 0.28-0.77 µg/L. The method was successfully used to determine four SUHs in three kinds of environmental water samples with satisfactory recoveries ranging from 78.8% to 109.7%. Therefore, the MIL-53(Fe)@PDA@Fe3O4 magnetic composite is efficient and has good potential for the extraction of SUHs.

Antimicrobial resistance and genetic diversity of the SXT element in Vibrio cholerae from clinical and environmental water samples in northeastern Thailand.

Multidrug resistance in V. cholerae has been increasing around the world including northeastern Thailand. The aquatic environment is a reservoir of V. cholerae and might be an important source of resistant strains. The aims of this study were to investigate the phylogenetic relationships of intSXT gene sequences from 31 clinical and 14 environmental V. cholerae O1 and non-O1/non-O139 isolates and 11 sequences amplified directly from environmental water samples. We also amplified class 1 integrons, the SXT elements (targeting the intSXT gene) and antimicrobial resistance genes directly from water samples. Phylogenetic analysis displayed two major distinct clusters (clusters 1 and 2). Most V. cholerae O1 (19/20, 95%) and non-O1/non-O139 isolates (8/11, 72.7%) from clinical sources, and all sequences obtained directly from water samples, belonged to cluster 1. Cluster 2 mostly comprised environmental non-O1/non-O139 isolates (10/12, 83.3%). We successfully amplified the SXT elements directly from17.5% of water samples. Associated resistance genes were also amplified as follows: sul2 (41.3% of water samples), dfrA1 (60%), dfr18 (33.8%), strB (70%) and tetA (2.5%). Class 1 integrons were not found in water samples, indicating that the SXT element was the major contributor of multidrug resistance determinants in this region. The SXT element and antimicrobial resistance genes could be transferred from clinical V. cholerae O1 to environmental V. cholerae non-O1/non-O139 was demonstrated by conjugation experiment. These findings indicate that there may have been cross dissemination and horizontal gene transfer (HGT) of the SXT element harbored by V. cholerae O1 and non-O1/non-O139 strains isolated from clinical and environmental water sources. Environmental water might be an important source of antimicrobial resistance genes in V. cholerae in this region. Direct detection of antimicrobial resistance genes in water samples can be used for monitoring the spread of such genes in the ecosystem.

Detection of emerging and re-emerging pathogens in surface waters close to an urban area.

Current knowledge about the spread of pathogens in aquatic environments is scarce probably because bacteria, viruses, algae and their toxins tend to occur at low concentrations in water, making them very difficult to measure directly. The purpose of this study was the development and validation of tools to detect pathogens in freshwater systems close to an urban area. In order to evaluate anthropogenic impacts on water microbiological quality, a phylogenetic microarray was developed in the context of the EU project µAQUA to detect simultaneously numerous pathogens and applied to samples from two different locations close to an urban area located upstream and downstream of Rome in the Tiber River. Furthermore, human enteric viruses were also detected. Fifty liters of water were collected and concentrated using a hollow-fiber ultrafiltration approach. The resultant concentrate was further size-fractionated through a series of decreasing pore size filters. RNA was extracted from pooled filters and hybridized to the newly designed microarray to detect pathogenic bacteria, protozoa and toxic cyanobacteria. Diatoms as indicators of the water quality status, were also included in the microarray to evaluate water quality. The microarray results gave positive signals for bacteria, diatoms, cyanobacteria and protozoa. Cross validation of the microarray was performed using standard microbiological methods for the bacteria. The presence of oral-fecal transmitted human enteric-viruses were detected using q-PCR. Significant concentrations of Salmonella, Clostridium, Campylobacter and Staphylococcus as well as Hepatitis E Virus (HEV), noroviruses GI (NoGGI) and GII (NoGII) and human adenovirus 41 (ADV 41) were found in the Mezzocammino site, whereas lower concentrations of other bacteria and only the ADV41 virus was recovered at the Castel Giubileo site. This study revealed that the pollution level in the Tiber River was considerably higher downstream rather than upstream of Rome and the downstream location was contaminated by emerging and re-emerging pathogens.

Highly sensitive determination of dialkyl phosphinate acids in environmental samples by ion chromatography tandem mass spectrometry.

Dialkyl phosphinate acids (DPAs) are the hydrolysates of aluminum dialkyl phosphinates (ADPs), one class of emerging phosphorus flame retardants since brominated flame retardants have been gradually phased out in recent years. It has been found that once dissolved in water, ADPs are completely hydrolyzed and exist as DPAs. However, there is no report on the determination of DPAs in environmental water samples. For the first time, we developed a method for the analysis of trace DPAs and ADPs in different environmental samples, including waters, soils and sediments. In this proposed method, MAX cartridges were employed for the purification, and ion chromatography (IC) tandem mass spectrometry (MS) method with large volume injection (200µL) and postcolumn addition of methanol and NH3·H2O were employed for the determination of DPAs and ADPs. The matrix effects were <16% for water samples and <25% for soil/sediment samples, which were greatly improved in comparison to the liquid chromatography (LC) tandem MS determination. Determined at three fortified levels of 0.02µg/L, 0.2µg/L and 1.0µg/L, the mean recoveries were from 75.8% to 110.2%, with an acceptable coefficient of variation (3.3-20%, n=6) for water samples. The limits of the method were 3.5-9.3ng/L for DPAs in environmental water samples, and 0.06-0.09µg/kg for DPAs and ADPs in soil and sediment samples. For soil and sediment samples, results determined by the present IC-MS method were in good agreement with that determined by LC-MS in our previous study.

Vortex-assisted low density solvent based demulsified dispersive liquid-liquid microextraction and high-performance liquid chromatography for the determination of organophosphorus pesticides in water samples.

A simple, rapid, effective and eco-friendly preconcentration method, vortex-assisted low density solvent based solvent demulsified dispersive liquid-liquid microextraction (VLDS-SD-DLLME), followed by high performance liquid chromatography-diode array detector (HPLC-DAD) analysis, has been developed for the first time for the determination of four organophosphorus pesticides (OPPs) (e.g., azinphos-methyl, parathion-methyl, fenitrothion and diazinon) in environmental water samples. In this preconcentration procedure, an emulsion was obtained after the mixture of extraction solvent (1-dodecanol) and dispersive solvent (acetonitrile, ACN) was injected rapidly into 10 mL of the sample solution. The vortex agitator aided the dispersion of the extraction solvent into the sample solution. After the formation of an emulsion, the demulsifier (ACN) was added, resulting in the rapid separation of the mixture into two phases without centrifugation. Under optimal conditions, the proposed method provided high extraction efficiency (90-99%), good linearity range (0.5-500 ng mL(-1)), low limits of detection (0.25-1 ng mL(-1)) and good repeatability and recoveries were obtained.