Analytica Chimica Acta (v.975, #C)

A hybrid and compact flow system for automatic assessment of trace level concentrations of bioaccessible mercury in different phases of environmental solid samples with high organic load is described for the first time. It integrates dynamic sequential extraction with on-line digestion of the extracts and atomic fluorescence spectrometric detection of their total bioaccessible mercury concentration. Four extractants (i.e. deionized water, HNO3 solution, KOH solution and solution containing both Na2S and KOH) are applied sequentially to a solid sample packed in a column to release four bioaccessible Hg fractions (i.e. water soluble, exchangeable, organic matter associated, and sulphide bound Hg). Important advantages of the newly developed on-line method compared to its batch-wise counterpart include significant reduction in the time for acquisition of the dynamic extraction data (e.g. duration of 14 h versus 120 h for the batch-wise method), evaluation of the kinetics of release of the bioaccessible mercury fractions, and minimization of matrix interferences and potential re-adsorption of the extracted mercury species. The trueness of the method was assessed by applying it to two reference materials with relatively high organic matter content (river sediment AGAL-10 and biosoil AGAL-12). The sums of the Hg concentrations in the four bioaccessible fractions and the residual fraction of the two reference materials were found to differ from the corresponding certified values by only 1.8% and 3.8%, respectively.Display Omitted
Keywords: Mercury; Sequential injection analysis; Dynamic fractionation; Sediment; Biosoil;

Cotton and silica are easily available and plentiful natural materials, with significant sorptive properties, which can be provided easily at low prices. In this research, a novel and effective sorbent was synthesized by covalent attachment of amino-silica/graphene oxide nanocomposite to the cotton (Cot/GO/Si) and packed into a stainless steel needle for preparation a needle trap device (NTD). The nanocomposite sorbent was characterized by SEM and FT-IR. The Cot/GO/Si packed NTD was used for direct extraction of PAHs from polluted soil samples, followed by GC-FID measurement. Different affecting experimental variables, including extraction temperature, flow rate, desorption time and temperature were studied and optimized. Under the optimal conditions, good linearity of the calibration curves (R 2 > 0.99) was obtained over the concentration range of 0.01–1.0 μg g−1. The limits of detection, limits of quantification and relative standard deviations were found to be in the ranges of 0.05–0.17 ng g−1, 0.2–0.6 ng g−1 and 9.7–15.4% (n = 6), respectively. Finally, the proposed NTD-GC-FID method was successfully applied for the extraction and determination of PAHs in contaminated soil samples.Display Omitted
Keywords: Cotton/graphene oxide/amino-silica nanocomposite; Needle trap device; PAHs; Soil; GC-FID;

In-situ ionic liquid dispersive liquid-liquid microextraction using a new anion-exchange reagent combined Fe3O4 magnetic nanoparticles for determination of pyrethroid pesticides in water samples by Chen Fan; You Liang; Hongqiang Dong; Guanglong Ding; Wenbing Zhang; Gang Tang; Jiale Yang; Dandan Kong; Deng Wang; Yongsong Cao (20-29).
In this work, in-situ ionic liquid dispersive liquid-liquid microextraction combined ultrasmall Fe3O4 magnetic nanoparticles was developed as a kind of pretreatment method to detect pyrethroid pesticides in water samples. New anion-exchange reagents including Na[DDTC] and Na[N(CN)2] were optimized for in-situ extraction pyrethroids, which showed enhanced microextraction performance. Pyrethroids were enriched by hydrophilic ionic liquid [P4448][Br] (aqueous solution, 200 μL, 0.2 mmol mL−1) reaction in-situ with anion-exchange reagent Na[N(CN)2] (aqueous solution, 300 μL, 0.2 mmol mL−1) forming hydrophobic ionic liquid as extraction agent in water sample (10 mL). Ultrasmall superparamagnetic iron oxide nanoparticles (30 mg) were used to collect the mixture of ionic liquid and pyrethroids followed by elution with acetonitrile. The extraction of ionic liquid strategies was unique and efficiently fulfilled with high enrichment factors (176–213) and good recoveries (80.20–117.31%). The method was successively applied to the determination of pyrethroid pesticides in different kinds of water samples with the limits of detection ranged from 0.16 to 0.21 μg L−1. The proposed method is actually nanometer-level microextraction (average size 80 nm) with the advantages of simplicity, rapidity, and sensitivity.Display Omitted
Keywords: In-situ; Ionic liquids; Pretreatment; Magnetic nanoparticles; Pyrethroid pesticides;

Risk assessment of exposure to chemicals from food and other sources rely on quantitative information of the occurrence of these chemicals. As screening analysis is increasingly used, a strategy to semi-quantify unknown or untargeted analytes is required. A proof of concept strategy to semi-quantifying unknown substances in LC-MS was investigated by studying the responses of a chemically diverse marker set of 17 analytes using an experimental design study. Optimal conditions were established using two optimization parameters related to weak-responding compounds and to the overall response. All the 17 selected analytes were semi-quantified using a different analyte to assess the quantification performance under various conditions. It was found that source conditions had strong effects on the responses, with the range of low-response signals varying from −80% to over +300% compared to centerpoints. Positive electrospray (ESI+) was found to have more complex source interactions than negative electrospray (ESI-). Choice of quantification marker resulted in better quantification if the retention time difference was minimized (12 out of 12 cases error factor < 4.0) rather than if the accurate mass difference was minimized (7 out of 12 cases error factor < 4.0). Using optimal conditions and retention time selection, semi-quantification in ESI+ (70% quantified, average prediction error factor 2.08) and ESI- (100% quantified, average prediction error factor 1.74) yielded acceptable results for untargeted screening. The method was successfully applied to an extract of food contact material containing over 300 unknown substances. Without identification and authentic standards, the method was able to estimate the concentration of a virtually unlimited number of compounds thereby providing valuable data to prioritize compounds in risk assessment studies.Display Omitted
Keywords: Semi-quantification; Untargeted analysis; Liquid chromatography-mass spectrometry; Electrospray ionization; Method optimization; Screening;

Segmental hair analysis offers a longer period for retrospective drug detection than blood or urine. Hair is a keratinous fiber and is strongly hydrophobic. The embedding of drugs in hydrophobic hair at low concentrations makes it difficult for extraction and detection with matrix-assisted laser desorption/ionization (MALDI) coupled with mass spectrometric imaging (MSI). In this study, a single scalp hair was longitudinally cut with a cryostat section to a length of 4 mm and fixed onto a stainless steel MALDI plate. Umbelliferone was used as a new hydrophobic matrix to enrich and assist the ionization efficiency of methamphetamine in the hair sample. MALDI-Fourier transform ion cyclotron resonance (FTICR)-MS profiling and imaging were performed for direct detection and mapping of methamphetamine on the longitudinal sections of the single hair sample in positive ion mode. Using MALDI-MSI, the distribution of methamphetamine was observed throughout five longitudinally sectioned hair samples from a drug abuser. The changes of methamphetamine were also semi-quantified by comparing the ratios of methamphetamine/internal standard (I.S). This method improves the detection sensitivity of target drugs embedded in a hair matrix for imaging with mass spectrometry. The method could provide a detection level of methamphetamine down to a nanogram per milligram incorporated into hair. The results were also compared with the conventional high performance liquid chromatography -tandem mass spectrometry (HPLC-MS/MS) method. Changes in the imaging results over time by the MSI method showed good semi-quantitative correlation to the results from the HPLC-MS/MS method. This study provides a powerful tool for drug abuse control and forensic medicine analysis in a narrow time frame, and a reduction in the sample amount required.Display Omitted
Keywords: Matrix-assisted laser desorption/ionization; Mass spectrometric imaging; Umbelliferone matrix; Methamphetamine abuse; Segmental hair analysis;

A single pH fluorescent probe for biosensing and imaging of extreme acidity and extreme alkalinity by Jian-Bin Chao; Hui-Juan Wang; Yong-Bin Zhang; Zhi-Qing Li; Yu-Hong Liu; Fang-Jun Huo; Cai-Xia Yin; Ya-Wei Shi; Juan-Juan Wang (52-60).
A simple tailor-made pH fluorescent probe 2-benzothiazole (N-ethylcarbazole-3-yl) hydrazone (Probe) is facilely synthesized by the condensation reaction of 2-hydrazinobenzothiazole with N-ethylcarbazole-3-formaldehyde, which is a useful fluorescent probe for monitoring extremely acidic and alkaline pH, quantitatively. The pH titrations indicate that Probe displays a remarkable emission enhancement with a pK a of 2.73 and responds linearly to minor pH fluctuations within the extremely acidic range of 2.21–3.30. Interestingly, Probe also exhibits strong pH-dependent characteristics with pK a 11.28 and linear response to extreme-alkalinity range of 10.41–12.43. In addition, Probe shows a large Stokes shift of 84 nm under extremely acidic and alkaline conditions, high selectivity, excellent sensitivity, good water-solubility and fine stability, all of which are favorable for intracellular pH imaging. The probe is further successfully applied to image extremely acidic and alkaline pH values fluctuations in E. coli cells.Display Omitted
Keywords: pH fluorescent probe; Extreme acidity and alkalinity; E. coli cells; Bioimaging;

Magnetic MoS2 on multiwalled carbon nanotubes for sulfide sensing by Chunxiang Li; Dan Zhang; Jiankang Wang; Pingan Hu; Zhaohua Jiang (61-69).
A novel hybrid metallic cobalt insided in multiwalled carbon nanotubles/molybdenum disulfide (Co@CNT/MoS2) modified glass carbon electrode (GCE) was fabricated with a adhesive of Nafion suspension and used as chemical sensors for sulfide detection. Single-layered MoS2 was coated on CNTs through magnetic traction force between paramagnetic monolayer MoS2 and Co particles in CNTs. Co particles faciliated the collection of paramagnetic monolayer MoS2 exfoliated from bulk MoS2 in solution. Amperometric analysis, cycle voltammetry, cathodic stripping analysis and linear sweep voltammetry results showed the Co@CNT/MoS2 modified GCE exhibited excellent electrochemical activity to sulfide in buffer solutions, but amperometric analysis was found to be more sensitive than the other methods. The amperometric response result indicated the Co@CNT/MoS2-modified GCE electrode was an excellent electrochemical sensor for detecting S2- with a detection limit of 7.6 nM and sensitivity of 0.23 mA/μM. The proposed electrode was used for the determination of sulfide levels in hydrogen sulfide-pretreated fruits, and the method was also verified with recovery studies.A paramagnetic property single layer MoS2 with carbon nanotube/Co-supported obtained from bulk MoS2 shows a low detection limit and a rapid response time for sulfide detection.Display Omitted
Keywords: Single layered MoS2; Paramagnetic; Chemical sensor; Sulfide detection;

Tributyltin (TBT) and pentachlorophenol (PCP) are listed as priority substances that warrant monitoring in the European Water Framework Directive (WFD 2000/60/CE), since TBT and PCP were identified as environmental endocrine disruptors and exhibit considerable toxicity toward both aquatic organisms and mammals even at very low levels.This paper shows a novel approach to analyze underivatized tributyltin (TBT) and pentachlorophenol (PCP) in seawater based on capillary gas chromatography-triple quadrupole mass spectrometry. The optimized extraction method for TBT an PCP in water involved liquid-liquid microextraction with toluene. The reduced extract was added with a solvent mix, composed of methanol and trimethylsilyl derivatives of methanol (MeOTMS), that allowed good chromatographic resolution of underivatized TBT and PCP, interacting as a lubricant along the glass liner during the injection phase.The proposed method showed good linearity and repeatability (RSD%<20% at 0.05 ng L−1 for TBT and 0.2 μg L−1 for PCP). The overall recoveries were 74% and 106% for TBT and PCP, respectively. Very low quantification limits that met the strict statutory and regulatory demands were achieved: 0.002 ng L−1 for TBT and 0.050 μg L−1 for PCP.Display Omitted
Keywords: Tributyltin; Pentachlorophenol; Capillary gas chromatography-triple quadrupole mass spectrometry; Liquid-liquid microextraction; Underivatized; Seawater;

Zymographic approach to determine the intrinsic enzyme specific activity of diamine oxidase in presence of interfering enzymes by Samaneh Ahmadifar; Tien Canh Le; Lucia Marcocci; Paola Pietrangeli; Mircea Alexandru Mateescu (78-85).
The purpose of this investigation was to elaborate a fast zymographic assay of oxidase enzymes in the presence of interfering enzymes as catalase (which disturbs current dosages based on H2O2 detection). This method also allows the determination of intrinsic specific activity (ISA) of oxidases, such as diamine oxidase (DAO) or glucose oxidase (GOD). The SDS-PAGE gels with entrapped peroxidase have been obtained by polymerization of acrylamide and bis-acrylamide in the presence of horse-radish peroxidase. The entrapped peroxidase was uniformly distributed in the PolyacrylAmide (PAA) material and did not migrate during electrophoresis. The obtained PAA gels allow the electrophoretic separation of various oxidases from contaminating proteins. As an example, to reveal DAO, the resulting PAA-gel should be incubated after the electrophoretic run in the developing solution containing putrescine (a DAO substrate) and o-phenylenediamine (a HRP substrate) to give coloured bands on the gel in the presence of DAO-generated H2O2. The results showed that is possible to determine the DAO in the presence of interfering catalase because they migrate differently. Thus, the H2O2 released in situ by DAO is no more decomposed by catalase because of its different mobility. It was also found that the same electrophoretic gel, after zymography, can be restained by Coomassie Blue for quantitation of proteins corresponding to the zymographic bands. With the obtained enzyme units and protein concentration it is also possible to calculate the intrinsic specific activity of DAO directly from the intensities of enzyme bands in zymography and from those of protein bands (Coomassie Blue staining), quantified by densitometry.Display Omitted
Keywords: Diamine oxidase; Catalase; Zymography; Intrinsic specific activity; Histamine; Alginate/carboxymethylstarch microspheres;

Separate screening of brominated and chlorinated dioxins in field samples using in vitro reporter gene assays with rat and mouse hepatoma cell lines by Go Suzuki; Masafumi Nakamura; Chieko Michinaka; Nguyen Minh Tue; Hiroshi Handa; Hidetaka Takigami (86-95).
In 2011, a joint World Health Organization (WHO) and United Nations Environment Programme expert panel recommended the use of the WHO toxicity equivalency factor (TEF) scheme for assessment of the human health risks of brominated dioxins which have different sources from chlorinated dioxins. Therefore, WHO toxic equivalents (TEQs) should be determined for both chlorinated and brominated dioxins. As alternative to the conventional but time-consuming dioxin analysis using gas chromatography high-resolution mass spectrometry, we have developed a screening method involving cleanup and separation of brominated dioxins from chlorinated dioxins in field samples and subsequent analysis by CALUX (chemically activated luciferase expression) assays which are in vitro reporter gene assays detecting dioxin-like compounds. Cleanup and separation were accomplished with silica gel columns impregnated with 55% sulfuric acid and with 10% silver nitrate, respectively, and the average recoveries of the major contributors to the WHO-TEQs were approximately 90%. The CALUX 2,3,7,8-TCDD equivalents (CALUX-TEQs) derived from all the dioxin-like compounds in the cleanup fractions of the field samples (n = 24) were measured by means of the CALUX assays, indicating significant positive correlations between the WHO-TEQs and CALUX-TEQs (r ≥ 0.969, P < 0.001). We found that the ratios of the chlorinated dioxin–derived WHO-TEQs to the brominated dioxin–derived WHO-TEQs were strongly positively correlated with the ratios of the CALUX-TEQs derived from the chlorinated dioxin fractions to the CALUX-TEQs derived from the brominated dioxin fractions (r ≥ 0.833, P < 0.001). These results suggest that our method will be useful for estimating the contributions of chlorinated and brominated dioxins to WHO-TEQs.Display Omitted
Keywords: Brominated dioxins; Chlorinated dioxins; Separate screening; in vitro reporter gene assay;