Haoyan Xu

Analysis of sulfonamides in environmental water samples based on magnetic mixed hemimicelles solid-phase extraction coupled with HPLC-UV detection.

The magnetic mixed hemimicelles solid-phase extraction (MMHSPE), based on the adsorption of cation surfactant octadecyltrimethylammonium bromide (OTMABr) onto magnetite nanoparticles (Fe(3)O(4) NPs) to form mixed hemimicelles, was proposed for the preconcentration of several sulfonamides (SAs) compounds including sulfamethoxazole (SMX), sulfamethoxydiazine (SMD), sulfadimethoxine (SDM) and sulfaquinoxaline (SQX) from environmental water samples. This method avoided the time-consuming column-passing process of loading large volume samples in traditional SPE through the rapid isolation of OTMABr-coated Fe(3)O(4) NPs with an adscititious magnet. Mixed hemimicelles formed on the surface of Fe(3)O(4) NPs by OTMABr showed great adsorptive tendency towards analytes. The OTMABr-coated Fe(3)O(4) NPs adsorbents were easy to be prepared, low cost and environmentally friendly. A comprehensive study on the adsorption conditions such as the amount of the surfactant, the solution pH, the desorption condition and the maximum extraction sample volume were optimized. A concentration factor of 1000 was achieved by the extraction of 500 mL of environmental water samples using MMHSPE. Detection limits obtained for SMX, SMD, SDM and SQX were 0.026, 0.024, 0.033 and 0.030 microg L(-1), respectively. Good recoveries (70-102%) with low relative standard deviations (1-6%) were achieved in analyzing spiked water samples. Low concentration of SQX was found in hospital primary and final sewage effluent sample.

Preparation of alumina-coated magnetite nanoparticle for extraction of trimethoprim from environmental water samples based on mixed hemimicelles solid-phase extraction

In this study, a new type of alumina-coated magnetite nanoparticles (Fe(3)O(4)/Al(2)O(3) NPs) modified by the surfactant sodium dodecyl sulfate (SDS) has been successfully synthesized and applied for extraction of trimethoprim (TMP) from environmental water samples based on mixed hemimicelles solid-phase extraction (MHSPE). The coating of alumina on Fe(3)O(4) NPs not only avoids the dissolving of Fe(3)O(4) NPs in acidic solution, but also extends their application without sacrificing their unique magnetization characteristics. Due to the high surface area of these new sorbents and the excellent adsorption capacity after surface modification by SDS, satisfactory concentration factor and extraction recoveries can be produced with only 0.1g Fe(3)O(4)/Al(2)O(3) NPs. Main factors affecting the adsolubilization of TMP such as the amount of SDS, pH value, standing time, desorption solvent and maximal extraction volume were optimized. Under the selected conditions, TMP could be quantitatively extracted. The recoveries of TMP by analyzing the four spiked water samples were between 67 and 86%, and the relative standard deviation (RSD) ranged from 2 to 6%. Detection and quantification limits of the proposed method were 0.09 and 0.24 microg L(-1), respectively. Concentration factor of 1000 was achieved using this method to extract 500 mL of different environmental water samples. Compared with conventional SPE methods, the advantages of this new Fe(3)O(4)/Al(2)O(3) NPs MHSPE method still include easy preparation and regeneration of sorbents, short times of sample pretreatment, high extraction yields, and high breakthrough volumes. It shows great analytical potential in preconcentration of organic compounds from large volume water samples.

Fast and Selective Extraction of Sulfonamides from Honey Based on Magnetic Molecularly Imprinted Polymer

A fast and selective method was developed for the determination of sulfonamides (SAs) in honey based on magnetic molecularly imprinted polymer. The extraction was carried out by blending and stirring the sample, extraction solvent and polymers. When the extraction was complete, the polymers, along with the captured analytes, were easily separated from the sample matrix by an adscititious magnet. The analytes eluted from the polymers were determined by liquid chromatography-tandem mass spectrometry. Under the optimal conditions, the detection limits of SAs are in the range of 1.5-4.3 ng g(-1). The relative standard deviations of intra- and interday ranging from 3.7% to 7.9% and from 4.3% to 9.9% are obtained, respectively. The proposed method was successfully applied to determine SAs including sulfadiazine, sulfamerazine, sulfamethoxydiazine, sulfamonomethoxine, sulfadimethoxine, sulfamethoxazole and sulfaquinoxaline in different honey samples. The recoveries of SAs in these samples from 67.1% to 93.6% were obtained.

Dynamic ultrasound-assisted extraction coupled on-line with solid support derivatization and high-performance liquid chromatography for the determination of formaldehyde in textiles.

An on-line method was developed for the extraction, derivatization and determination of formaldehyde in textile samples. Formaldehyde was first extracted with water by ultrasound assisted, and directly introduced into a derivatization column which was packed with a moderately sulfonated cation-exchange resin. The resin used as solid support for the derivatization was charged with 2,4-dinitrophenylhydrazine (DNPH) previously. The formaldehyde DNPH derivative was eluted with the chromatographic mobile phase into an analytical column for the separation, and then monitored by UV detector. The maximum extraction yield was achieved when the extraction vessel was located at 10mm from the ultrasonic source and 10mg textile sample was extracted with 5mL pure water at a flow rate of 1.0mLmin(-1) at 50 degrees C. The detection limit of the proposed method was 0.06mgkg(-1). This method was applied to the determination of formaldehyde in different textile samples, and compared with the state standard method (off-line spectrophotometry) used in China. The similar contents of formaldehyde were obtained for most samples by the two methods, but little higher for some samples obtained by the proposed method. The average relative standard deviation (RSD) obtained by the on-line method was 3.2% which is lower than 29.5% obtained by the standard method.

Preparation of magnetic strong cation exchange resin for the extraction of melamine from egg samples followed by liquid chromatography–tandem mass spectrometry

In the work, magnetic strong cation exchange (MSCX) resins were prepared using hydrophobic Fe(3)O(4) magnetite as the magnetically susceptible component, styrene and divinylbenzene as polymeric matrix components, acetyl sulfonate as the sulfonation agent. The resins were successfully applied to the extraction of melamine (MEL) from egg samples. The extraction procedure was carried out in a single step by blending and stirring the sample, extraction solvent and the magnetic resins. The MEL was extracted from the sample matrix then adsorbed onto the resins directly through ion-exchange interaction. When the extraction was completed, the resins with adsorbed analyte were easily separated from the sample matrix by applying an appropriate magnetic field. Main factors affecting the extraction of MEL such as the amount of MSCX resins, extraction time, washing and eluting conditions were optimized. The MEL eluted from the resins was determined by liquid chromatography-tandem mass spectrometry. The linearity of quantification obtained by analyzing matrix-matched standards is in the range of 10-1000 ng g(-1). The limit of detection and quantification obtained are 2.6 and 8.8 ng g(-1), respectively. The relative standard deviations of intra- and inter-day ranging from 1.6% to 6.5% and from 2.1% to 7.2% are obtained. The recoveries of MEL are in the range of 77.2-99.3%. The proposed method was successfully applied to determine MEL in eggs obtained from different local markets. MEL was detectable with the contents of 43.5 and 234.1 ng g(-1) in two samples.

A green method using micellar system for determination of sulfonamides in soil

A green and simple method was developed for determination of sulfonamides (SAs) in soil samples. The procedure was based on the microwave-assisted extraction (MAE) of SAs from soil using non-ionic surfactant Triton X-114 as the extraction medium. Then sodium chloride was added into the MAE extract and the mixture was equilibrated for some time at high temperature. The analytes in the surfactant-rich phase were concentrated with the help of centrifugation and directly analyzed by high performance liquid chromatography with UV detection. None of potentially hazardous organic solvents was used in the whole sample preparation procedure. The significant variables for the performance of extraction and concentration were studied. The limits of detection of SAs obtained are in the range of 3.2-5.7 ng g(-1). The relative standard deviations of intra- and inter-day tests ranging from 3.5% to 7.7% and from 4.6% to 9.5% are obtained, respectively. This method was applied to the determination of SAs in some soil samples with different characteristics. The SAs recoveries obtained at fortified level of 100 ng g(-1) for these samples are in the range of 81.2-93.7%. The effect of ageing time of spiked soil samples on the SAs recoveries was examined by the proposed method and a method reported in the literature. The recoveries of SAs decreased when the ageing time changed from 1 day to 4 weeks.

Microwave-assisted extraction and in situ clean-up for the determination of fluoroquinolone antibiotics in chicken breast muscle by LC-MS/MS.

A new method was developed for the determination of six fluoroquinolone antibiotics including fleroxacin, levofloxacin, ciprofloxacin, lomfloxacin, enrofloxacin, and sparfloxacin in chicken breast muscle, in which the extraction and clean-up were performed in one step by microwave irradiation. The mixture of ACN containing 0.3% v/v phosphoric acid/water pH 3 (70:30, v/v) was used as the extraction solution and hexane was used as the clean-up solution. The extract was analyzed by liquid chromatography-tandem mass spectrometry system. The RSDs of intra- and inter-day obtained are in the range of 1.0-10.4 and 3.8-13.6%, respectively. In the three fortified levels of chicken breast muscle (20, 100, and 500 ng/g), the recoveries of fluoroquinolone antibiotics ranging from 66.0 to 97.2% are obtained. The LODs are in the range of 2.7-6.7 ng/g. This method simplifies the process of the sample preparation and reduces the operation errors.

Microwave-assisted extraction coupled online with derivatization, restricted access material cleanup, and high-performance liquid chromatography for determination of formaldehyde in aquatic products.

A rapid technique based on microwave-assisted extraction (MAE) coupled online with derivatization, restricted access material cleanup, and high-performance liquid chromatography (HPLC) was developed for the determination of formaldehyde in aquatic products. Formaldehyde was first extracted with water under the action of microwaves and then directly introduced into a derivatization reservoir containing 2,4-dinitrophenylhydrazine (DNPH). The formaldehyde-DNPH derivative (100 μL) was loaded into a restricted access material (RAM) precolumn for online cleanup. Subsequently, the analyte was transferred from the precolumn to an analytical column and determined by UV absorption spectrum at 352 nm. The limit of detection (LOD) was 0.27 mg kg(-1). The intraday and interday precisions expressed as RSDs were 3.5% and 5.0%, respectively. This method was applied to determine the presence of formaldehyde in various aquatic products. The results were in agreement with those obtained by the state standard method (steam-distillation and offline HPLC analysis) used in China and higher than those obtained by the online ultrasound-assisted extraction (UAE) method. The recoveries obtained by analyzing 11 spiked aquatic products were in the range of 70.0%-105.0%. The online technique was demonstrated to be rapid with little consumption of samples and reagents.