High enrichment and measurement of heterocyclic aromatic hydrocarbons from environmental waters with magnetic resorcinol-formaldehyde nanocomposites coupled with high performance liquid chromatography.

Heterocyclic aromatic hydrocarbons are concerned pollutants with carcinogenic toxicity, which exist universally in various environmental matrices and have great harm to environmental and human health. In present work, magnetic resorcinol-formaldehyde composites (Fe3O4@SiO2@R-F) were fabricated via aldol condensation reaction under alkaline condition. The prepared magnetic materials were examined and analyzed with Fourier transform infrared spectroscopy and other related instruments. The Fe3O4@SiO2@R-F composites were utilized to develop an efficient magnetic solid phase extraction (MSPE) method for extracting six heteropolyclic aromatic hydrocarbons from environmental water samples including carbazole (CB), 7-methylquinoline (7-MQL), 9-methylcarbazole (9-MCB), dibenzothiophene (DBT), 4-methyldibenzothiophene (4-MDBT), and 4,6-dimethyldibenzothiophene (4,6-DMDBT). The analytes were analyzed by high performance liquid chromatography-ultraviolet variable wavelength detector (HPLC-VWD). The main factors affecting MSPE were optimized. With the optimal parameters, 9-MCB and 4-MDBT have good linearity over the concentration range of 0.1-300 µg L-1, and 7-MQL, CB, DBT and 4,6-DMDBT have good linearity over the concentration range of 0.5-300 µg L-1. The limits of detection were over the concentration range of 0.012-0.031 µg L-1. This method was successfully employed to measure real waters, and the spiked recoveries ranged from 89.4% to 99.9%. The results confirmed that the developed method was reliable, robust and could be employed as a usefully alternate way for analyzing such pollutants in waters.

A functionalized glass fiber as the adsorbent for efficient analysis of endocrine disruptors in aqueous environments.

Estrogens and bisphenols are typical endocrine disruptors (EDs) that pose a potential hazard to the human body due to their widespread presence in aqueous environments. In this study, a ß-cyclodextrin porous crosslinked polymer (ß-CD-PCP) was prepared in-situ on a glass fiber surface by a nucleophilic substitution reaction. An effective and sensitive solid phase microextraction method using functionalized glass fiber with ß-CD-PCP coating as the adsorbent was established for the detection of 11 EDs in a water environment. The ß-CD-PCP was in-situ prepared on a glass fiber surface by a nucleophilic substitution reaction. The ß-CD-PCP successfully separated five estrogens (ESTs) and six bisphenols (BPs) through hydrophobic and π-π interactions. The conditions affecting extraction were optimized. Under the optimized conditions, the ESTs obtained a high enrichment effect (1795-2328), low limits of detection (0.047 µg L-1) and a good linearity range (0.2-15.0 µg L-1). Furthermore, the spiked recoveries of analyte ESTs in aqueous environments were between 82.9-115.7 %. The results indicated that the prepared functionalized glass fibers exhibited good adsorption properties, and the established analytical method was reliable for monitoring trace ESTs and BPs in aqueous environments.

ß-Cyclodextrin functionalized magnetic polyamine-amine dendrimers for high enrichment and effective analysis of trace bisphenolic pollutants in beverages.

Bisphenols (BPs) are typical endocrine disruptors, which can cause great effects on environmental, organisms and human health. In this study, ß-Cyclodextrin (ß-CD) functionalized polyamidoamine dendrimers-modified Fe3O4 nanomaterials (MNPs@PAMAM (G3.0)@ß-CD) were facilely synthesized. It exhibited good adsorption capacities for BPs, which was utilized to construct a sensitive tool in combination with high performance liquid chromatography for monitoring BPs such as bisphenol A (BPA), tetrabromobisphenol A (TBBPA), bisphenol S (BPS), bisphenol AF (BPAF) and bisphenol AP (BPAP) in beverage samples. The factors affecting the enrichment were examined such as generation of adsorbent, dosage of adsorbent, type and volume of eluting solvent, elution time and pH value of sample solution. The optimal parameters for enrichment was as follows: dosage of adsorbent, 60 mg; adsorption time, 50min; sample pH, pH7; elutent, 9 mL mixture of methanol and acetone(1:1); elution time, 6min; sample volume, 60 mL. The experimental results demonstrated that the adsorption conformed to pseudo-second-order kinetic model and Langmuir adsorption isotherm model. The results showed the maximum adsorption capacities of BPS, TBBPA, BPA, BPAF and BPAP were 131.80 µgg-1, 139.84 µgg-1, 157.08 µgg-1, 142.11 µgg-1 and 134.23 µgg-1, respectively. Under optimal conditions, BPS had good linear relationship over range from of 0.5-300 µgL-1, and the linear ranges of BPA, TBBPA, BPAF and BPAP ranged from 0.1 to 300 µgL-1. The limits of detection (S/N = 3) for BPs were good in range of 0.016-0.039 µgL-1. The spiked recoveries of target bisphenols (BPs) in beverages were approving over range from 92.3% to 99.2%. The established method possessed merits of easy to operate, good sensitivity, rapidness as well as environmental friendliness, and which earned great application potential for the enrichment and detection of trace BPs in practical samples.

Highly efficient and simultaneous magnetic solid phase extraction of heavy metal ions from water samples with l-Cysteine modified magnetic polyamidoamine dendrimers prior to high performance liquid chromatography.

Due to the strong metal-sulfur interaction between mercapto groups and metal ions, which can be used to functionalize polyamidoamine dendrimer decorated Fe3O4 nanoparticles for high enrichment of trace heavy metal ions from waters. Based on this concept, polyamidoamine dendrimer modified Fe3O4 nanomaterials were functionalized with l-Cysteine and a new magnetic solid phase extraction for rapid adsorption and separation of Hg2+, Pb2+, Co2+ and Cd2+ from waters was established. The factors affecting extraction efficiency have been optimized. Upon the optimal parameters, the established method provided good linear ranges of 0.1-200 µg L-1 for Hg2+ and 0.05-200 µg L-1 for Pb2+, Co2+ and Cd2+, and high sensitivity with limits of detection (LOD) of 0.018 µg L-1, 0.014 µg L-1, 0.013 µg L-1 and 0.025 µg L-1 for Cd2+, Pb2+, Co2+ and Hg2+, respectively. Real water samples were utilized to validate the proposed method, and achieved results revealed that the proposed method was sensitive, effective, stable and suitable for monitoring Pb2+, Cd2+, Co2+and Hg2+ in environmental waters. This work provided a novel strategy for the simultaneous analysis of target cations in waters, and a new direction for developing decoration method of nanomaterials according to specific purpose.

Magnetic solid phase extraction and determination of polychlorinated biphenyls in beverages utilizing C60 modified magnetic polyamido-amine dendrimers in combination with gas chromatography-tandem mass spectrometry.

Polychlorinated biphenyls (PCBs) are persistent organic pollutants which are widely present in environment and harmful to human health. In this study, an efficient and convenient magnetic solid phase extraction method with C60 modified magnetic polyamido-amine (PAMAM) dendrimers as sorbents was established for enriching trace amounts of PCBs in beverage samples. Gas chromatography-tandem mass spectrometry (GC-MS/MS) was utilized for analysis of PCBs. Parameters affecting extraction efficiency were optimized. Under optimal parameters, good linearity can be achieved in concentration range of 0.001-20 µg L-1 and 0.002-20 µg L-1 for nine selected PCBs. The limits of detection for PCBs were in the range of 0.1-0.2 ng L-1. The spiked recoveries were in the range of 87.0 %-115.1 % (n = 3). The results proved that this established method was reliable for monitoring trace PCBs in beverage samples.

Novel electrochemical sensor from magnetic carbon dots and cetyltrimethylammonium bromide for sensitive measurement of tetrabromobisphenol A in beverages.

Present work depicted a novel electrochemical sensor fabricated with magnetic carbon dots (M-CDs) and cetyltrimethylammonium bromide (CTAB) modified glassy carbon electrode (GCE) for selective measurement of 3,3',5,5'-tetrabromobisphenol A (TBBPA) in beverages. The M-CDs composite material revealed good electrocatalytic activity, and CTAB has strong hydrophobic interaction which enable it have good enrichment capacity of hydrophobic compounds, and combination of them further enhances the electrochemical signal. Hence CTAB decoration can markedly improve the detection performance of TBBPA. Electrochemical properties of the fabricated sensor was investigated through performing cyclic voltammetry (CV). The morphology and functional groups of the modified materials were examined with transmission electron microscope (TEM) and Fourier transform infrared spectroscopy (FTIR). The results indicated that the synthesized material had a spherical-like structure, good dispersion properties and plenty of functional groups on the surface. The effects of incubation potential, incubation time, pH of electrolyte, and scanning rate on oxidation peak current were investigated. Under optimal conditions, the designed sensor had good linear range of 1 nM-1000 nM, and the detection of limit of the constructed sensor was 0.75 nM. The constructed sensor was utilized to detect TBBPA in vitamin water, scream drink and genki forest, and satisfactory detection performance had been achieved.

Sensitive determination of polychlorinated biphenyls from beverages based on switchable solvent microextraction: A robust methodology.

Polychlorinated biphenyls (PCBs) are a kind of hazardous persistent organic contaminants and widely present in nature due to large consumption in the past. Although PCBs have been banned in many countries of the world, they are still present at trace level in food and water samples. It is of significant value to establish reliable enrichment and detection method. Based on the conversion of the hydrophilicity and hydrophobicity from heptanoic acid under alkali and acid, increasing the contact area between heptanoic acid and PCBs, a new switchable solvent micro-extraction method for PCBs from beverages was developed with good extraction efficiency using heptanoic acid as the extractant prior to gas chromatography-tandem mass spectrometry (GC-MS/MS). The key parameters that had impact on enrichment of PCBs were investigated in detail. Under the optimal conditions, a good linearity can be achieved in a concentration range of 0.01-20 µg L-1 with the correlation coefficients of 0.9978-0.9994. Limits of detection for PCB28, PCB53, PCB206 were 3 ng L-1 and PCB118 was 5 ng L-1 while other target PCBs were 2 ng L-1. Intra-day and inter-day precisions were in the range of 1.9-4.2% and 2.1-4.2％(relative standard deviation, RSD, n = 6), respectively. The real sample spiked recoveries of the targets were in the range of 93.2-114.3％ (n = 3). The enrichment factors were in the range of 16.2-17.9. The results proved that this method was reliable for monitoring trace PCBs in beverage samples and will help for future assessments of impacts on human and animal health.

Graphene oxide modified magnetic polyamidoamide dendrimers based magnetic solid phase extraction for sensitive measurement of polycyclic aromatic hydrocarbons.

In this study, graphene oxide modified magnetic polyamidoamine dendrimers (MNPs@PAMAM-G2.0@GO) nanoparticles were successfully prepared by amidation method. The obtained MNPs@PAMAM-G2.0@GO nanocomposites were examined by fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), scanning electron microscope (SEM) and transmission electron microscopy (TEM), etc. MNPs@PAMAM-G2.0@GO exhibited excellent adsorption property and was investigated for magnetic solid phase extraction (MSPE) of polycyclic aromatic hydrocarbons (PAHs) from water. The detection of extracted PAHs was accomplished by high performance liquid chromatography (HPLC) and gas chromatography tandem mass spectrometry (GC-MS/MS). The target PAHs included anthracene (ANT), pyrene (PYR), fluoranthene (FLT), carbazole (CB), 7-methylquinoline (7-MQL), 9-methylcarbazole (9-MCB), dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DBT). Important operation parameters for MSPE that could affect the extraction efficiencies of PAHs were investigated in detail. Under optimal parameters, the constructed method demonstrated excellent linear range with 0.001-10 µg L-1 for analytes and low limits of detection within the range of 0.11-0.9 ng L-1. The spiked average recoveries of PAHs in natural water samples ranged from 92.5% to 105.2%. The promising results indicated that MNPs@PAMAM-G2.0@GO could be employed to efficiently extract PAHs from aqueous samples.

Highly selective fluorescence sensor sensing benzo[a]pyrene in water utilizing carbon dots derived from 4-carboxyphenylboronic acid.

4-Carboxyphenylboronic acid was used as the single precursor to facilely prepare fluorescent carbon quantum dots by one-step solvothermal method. The as-obtained carbon dots (CDs) exhibited highly selective and sensitive for benzo[a]pyrene (BaP), and may be a splendid sensor for sensing BaP. The principle was that the as-prepared CDs could form a complex with BaP through hydrophobic interaction which causes the decrease of fluorescence intensity of CDs by static quenching principle. The constructed fluorescent sensor exhibited excellent linearity ranged from 0.002 to 0.06 µg mL-1 and provided a low limit of detection of 0.16 ng mL-1. The experimental results showed that this fluorescent sensor resulted in simplicity, rapidness, low cost, short analytical time, and high sensitivity and stability. Validation with real water samples endowed the sensor high reliability and feasibility for BaP determination in practical application in various samples.

Magnetic and thermal dual-sensitive core-shell nanoparticles for highly preconcentration and measurement of Sudan red pollutants.

Recently, thermal-sensitive polymers absorbed much more concerns, and the goal of present work was to modify magnetic nanoparticles with N-isopropylacrylamide (NIPAM) and methyl 3,3-dimethylacrylate (DMMA) for obtaining thermal and magnetic dual-sensitive nanoparticles based on silica coated nanoscale zero valent iron and thermal-sensitive polymers (Fe@p(NIPAM-co-DMMA)). Fe@p(NIPAM-co-DMMA) nanoparticles were fabricated and possessed excellent adsorption ability for Sudan pollutants in aqueous samples. A rapid extraction and separation approach utilizing synthesized dual-sensitive nanomaterials was designed and developed before analysis by liquid chromatography (HPLC). Upon the enrichment factors as their optimal values, the established method gained wonderful linearity over the range of 0.05-500 µg L-1. The precisions of proposed method were all lower than 3.87%. The validating experiments ensured that this developed method provided with satisfied recoveries in the range of 97.4-102.6% from spiked real water samples, which affirmed that this method was a reliable monitoring tool for Sudan pollutants in water and food samples, etc.

Magnetic polyamidoamine dendrimers for magnetic separation and sensitive determination of organochlorine pesticides from water samples by high-performance liquid chromatography.

Organochlorine pesticides (OCPs) have received much attention due to their toxicity. Reliable methods to monitor their residues in the environment are needed. Here, magnetic polyamidoamine dendrimers were prepared by co-precipitation, Michael addition, and amidation. The magnetic polyamidoamine dendrimers demonstrated good adsorption ability for OCPs-this feature was utilized to construct a sensitive tool for monitoring OCPs in water samples. The proposed method provided remarkable linearity from 0.1 to 500 µg/L and satisfactory limits of detection from 0.012 to 0.029 µg/L. The spiked recoveries of the four target analytes were 91.8%-103.5% with relative standard deviations less than 4.5%. The magnetic materials had good reusability. The results indicated that the resulting method was an efficient, easy, rapid, economical, and eco-friendly tool for monitoring OCPs in aqueous samples.

Magnetic solid phase extraction of heterocyclic aromatic hydrocarbons from environmental water samples with multiwalled carbon nanotube modified magnetic polyamido-amine dendrimers prior to gas chromatography-triple quadrupole mass spectrometer.

Present study described a sensitive and efficient method for determination of heterocyclic aromatic hydrocarbons using multiwalled carbon nanotubes modified magnetic polyamido-amine dendrimers (MNPs@PAMAM-Gn@MWCNTs) as adsorbent for magnetic solid-phase extraction (MSPE) coupled with gas chromatography-triple quadrupole mass spectrometer (GC-MS/MS). Some pivotal parameters including PAMAM generation, adsorbent dosage, adsorption time, elution time and volume, pH and humic acid concentration were investigated to achieve the best adsorption efficiencies. Under the optimal conditions, 7-methylquinoline, dibenzothiophene and carbazole had good linearity in the concentration range of 0.005-20 µg L - 1, 9-methylcarbazole, 4-methyldibenzothiophene and 4,6-dimethyl dibenzothiophene had good linearity in the concentration range of 0.001-20 µg L - 1. All the correlation coefficients were higher than 0.996. The detection limits of the targets were in the range of 2.2 × 10-4-1.8 × 10-3 µg L - 1 with precisions less than 8.28% (n = 6). The enrichment factors were in the range of 141-147. The spiked recoveries were in the range of 87.0%-115.1% (n = 3). These results indicated that the method could be a reliable alternative tool for monitoring trace heterocyclic aromatic hydrocarbons in environmental water samples.

Magnetic polyamidoamine dendrimer grafted with 4-mercaptobenzoic acid as an adsorbent for preconcentration and sensitive determination of polycyclic aromatic hydrocarbons from environmental water samples.

Polyamidoamine dendrimer decorated Fe3O4 magnetic nanoparticles was synthesized and grafted with 4-mercaptobenzoic acid (4-MBA). The resulting material was utilized to develop an effective magnetic solid phase extraction method in combination with high performance liquid chromatography for trace determination of polycyclic aromatic hydrocarbons including phenanthrene (PHE), anthracene (ANT), fluoranthene (FLT), pyrene (PYR) and benzo(a)pyrene (BaP). The MNPs@G3.0@4-MBA exhibited to be an efficient extracting medium due to the existence of terminal benzene ring groups, the internal pores, and strong hydrophobic interactions and π-π interactions. The experiments demonstrated that the proposed method possessed excellent linearity in the concentration range of 0.1-300 µg L-1 with correlation coefficients (R) larger than 0.997, and the limits of detection (LODs, S/N = 3) according to the ratio of signal to noise equal to three of PHE, ANT, FLT, PYR and BaP were 0.014 µg L-1, 0.032 µg L-1, 0.055 µg L-1, 0.027 µg L-1 and 0.039 µg L-1, respectively. The proposed method was applied to real water samples and the spiked recoveries were over the range of 92-99%. The results showed that the method earned good repeatability and high sensitivity, and the as-prepared materials were stable and reusable, which displayed that the proposed method would have a wonderful application prospect.

Magnetic solid phase extraction of bisphenol A, phenol and hydroquinone from water samples by magnetic and thermo dual-responsive core-shell nanomaterial.

Present study prepared a new magnetic and thermo dual-responsive core-shell nanomaterial (Fe@SiO2@poly(N-isopropylacrymide-co-methacrylic acid, Fe@SiO2@PNIPAM-co-MAA), which was characterized by transmission electron microscopy and X-ray diffraction techniques. The new nanomaterials integrated with the magnetism of nanoscale zero valent iron material and thermo-response of the copolymers, and were utilized to investigate the adsorption capacity for typical phenols such as bisphenol A, phenol and hydroquinone from water samples, and the results showed that the magnetic and thermo dual-responsive core-shell nanomaterial exhibited good adsorption ability to typical phenols. Based on these, a sensitive method was developed for the determination of bisphenol A, phenol and hydroquinone using as-prepared magnetic nanoparticles as the magnetic solid phase extraction sorbent prior to high performance liquid chromatography coupled with variable wavelength detection. Under the optimal conditions, linear linearity was obtained over the range of 0.1-500 µg L-1 with the correlation coefficients (r2) above 0.996. The detection limits of three analytes were in the range of 0.019-0.031 µg L-1, and the precisions were all less than 4.8% (n = 6). The developed method was evaluated with real water samples and excellent spiked recoveries in the range of 94.0-105.4% were achieved. These results indicated that the proposed method was a robust analytical tool and a useful alternative for routine analysis of such pollutants.

Enrichment and sensitive determination of phthalate esters in environmental water samples: A novel approach of MSPE-HPLC based on PAMAM dendrimers-functionalized magnetic-nanoparticles.

Phthalate esters (PAEs) are an important kind of environmental endocrine disrupting chemicals, and have attracted great attention in environmental field. Present study described a new method for rapid and sensitive determination of PAEs including dibenzyl phthalate (DPhP), dibutyl phthalate (DnPP), and dicyclohexyl phthalate (DCHP) from aqueous matrices based on magnetic solid-phase extraction. Polyamidoamine (PAMAM) dendrimers-grafted magnetic-nanoparticles were synthesized and characterized, and the expected integration of more multifunctional sites of PAMAM dendrimers and rapid separation property was utilized for method development. To achieve the best extraction efficiency, several important parameters were optimized including the dosage of the adsorbent, sample pH, kind and volume of eluent, extraction time, desorption time, ionic strength. Under the optimal conditions, three phthalate esters were well enriched and simultaneously determined by high performance liquid chromatography with variable wavelength detector (VWD). Excellent linearities were observed in the range of 0.1-600 µg L-1 for DPhP and DnPP and 0.5-600 µg L-1 for DCHP, and all correlation coefficients (R2) were larger than 0.997. The limits of detection (LODs, S/N = 3) were ranged from 0.025 to 0.16 µg L-1. The spiked recoveries of PAEs in real water samples were in the range of 93.5-101.8% with satisfied relative standard deviations (RSDs) ranging from 0.9 to 4.1%. The prepared magnetic materials have shown good adsorption capability for PAEs and the developed method earned merits such as high sensitivity, simplicity, rapidness and environmental friendliness, which can be used as a robust alternative tool for monitoring PAEs in water samples.

Simultaneous enrichment and determination of cadmium and mercury ions using magnetic PAMAM dendrimers as the adsorbents for magnetic solid phase extraction coupled with high performance liquid chromatography.

In present study, a sensitive and efficient method based on magnetic PAMAM dendrimers as the sorbents for magnetic solid-phase extraction (MSPE) coupled with high performance liquid-phase chromatography and ultraviolet variable wavelength detector (HPLC-VWD) was developed for simultaneous determination of trace cadmium and mercury ions. Sodium diethyldithiocarbamate (DDTC-Na) was used as the chelating agent during the elution process. Parameters that would affect the extraction efficiency including PAMAM generation, adsorbent dosage, adsorption time, elution time and volume, pH and coexisting ions were investigated to achieve the best adsorption efficiency. Under the optimal conditions, good linear relationship was obtained in the range of 0.05-200 µg L-1 for Cd2+ and 0.1-200 µg L-1 for Hg2+, and the limits of detection were 0.016 and 0.040 µg L-1, respectively. The spiked recoveries of Cd2+ and Hg2+ were satisfied in the range of 91.5-105% (n = 3). The proposed method was proved to be an alternative and reliable method to determine trace Cd2+ and Hg2+ in water samples.

Improved photoelectrocatalytic degradation of tetrabromobisphenol A with silver and reduced graphene oxide-modified TiO2 nanotube arrays under simulated sunlight.

In present study, reductive graphene oxide and silver nanoparticles co-comodified TiO2 nanotube arrays were prepared, and which was investigated to degrade tetrabromobisphenol A. The arrays co-modified with silver nanoparticles and reductive graphene oxide prepared by electrodeposition method exhibited good photoelectrocatalytic degradative activity for tetrabromobisphenol A, and the degradation efficiency reached 99.6% within 80 min. The synergistic effect of high photoresponse of Ag nanoparticles with their high capture ability for photogenerated electrons and the extended wavelength absorption range of reductive graphene oxide resulted in the highest degradation efficiencies. Degradation is postulated to follow a stepwise reductive debromination mechanism.

Structural Transformation Pathways of Alkaline Earth Family Coordination Polymers Containing 3,3',5,5'-Biphenyl Tetracarboxylic Acid.

The understanding of crystal stepwise transformation is very important to enclose the "black box" in the preparation of crystal materials. In this work, different structural intermediates were isolated prior to the formation of the final alkali earth coordination polymers (CPs) during the preparation of three pairs of alkali earth CPs through solvothermal method and convenient oil-bath reactions. Single crystal X-ray diffraction analysis demonstrated the structural transformation from a 0 D to 1 D inorganic connectivity for the Ca-CPs and Sr-CPs, but a 1 D to 0 D inorganic connectivity for Ba-CPs, involving the breakage/formation of chemical bonds in the reaction solutions. Further analyses indicated that these two different structural transformation pathways are determined by the deprotonation of organic acid, competitive balance between the inorganic and organic connectivity, and the twist of the linker. FT-IR spectra, thermogravimetric and luminescence behaviors agree with their structural characteristics.

Polyamidoamine dendrimer decorated nanoparticles as an adsorbent for magnetic solid-phase extraction of tetrabromobisphenol A and 4-nonylphenol from environmental water samples.

Polyamidoamine dendrimer decorated Fe3O4 magnetic nanoparticles were successfully synthesized by Michael addition with methyl acrylate and amidation with ethylenediamine. The decorated magnetic particles were utilized as an effective adsorbent for magnetic solid-phase extraction of tetrabromobisphenol A and 4-nonylphenol at trace levels from environmental water samples. A number of parameters such as generation number, ionic strength, adsorbent dosage, eluent, adsorption time, elution volume, elution time, pH, humic acid and sample volume were optimized. Under the optimal conditions, a wide linearity was achieved in the range of 0.1-500 µg L-1 of the analytes with the correlation coefficients (R2) of 0.9985-0.9995. The limits of detection were approximately 0.011 µg L-1 of tetrabromobisphenol A and 0.017 µg L-1 of 4-nonylphenol. Satisfactory average recoveries of the analytes ranged from 93.2% to 101.1%. The results indicated that the decorated magnetic nanoparticles can be suitable for extraction of phenols from environmental water samples. The proposed method was sensitive, effective, practical and robust for the determination of tetrabromobisphenol A and 4-nonylphenol in environmental water samples.

pH-Dependent reversible crystal transformation of 1-carboxymethyl-1-methyl-pyrrolidinium bromides and their spectroscopic fingerprint.

In this work, two 1-carboxymethyl-1-methyl-pyrrolidinium bromides (N-methylpyrrolidine betaine hydrobromides) with the stoichiometry of betaine:hydrobromic acid as 1:1 and 2:1, denoted as CMPRHBr-I and CMPRHBr-II, respectively, were prepared and crystallographically determined. The large difference in these two structures is the type of hydrogen bonds, resulting in the different thermal stability. A strong OH⋯Br hydrogen bond was observed in CMPRHBr-I, whereas O⋯H⋯O hydrogen bond in CMPRHBr-II. Both these two crystals can mutually transform by changing the pH value of the aqueous solution. Vibrational spectroscopic studies shows that these two structures can be easily distinguished by the characteristic bands such as νCO stretching vibration and the D-type bands. Our studies indicate that it should be cautious of the structural change as this type of organic salts was purified and recrystallized.