Qinglei Zeng

Preparation of magnetic molecularly imprinted polymer for the separation of tetracycline antibiotics from egg and tissue samples

Magnetic molecularly imprinted polymers were prepared using hydrophobic Fe(3)O(4) magnetite as the magnetically susceptible component, oxytetracycline as template molecule, methacrylic acid as functional monomer, and styrene and divinylbenzene as polymeric matrix components. The polymers were applied to the separation of tetracycline antibiotics from egg and tissue samples. The extraction and clean-up procedures were carried out in a single step by blending and stirring the sample, extraction solvent and polymers. The analytes can be transferred from the sample matrix to the polymers directly or through the extraction solvent as medium. When the extraction was complete, the polymers adsorbing the 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. The recoveries ranging from 72.8% to 96.5% were obtained with relative standard deviations in the range of 2.9-12.3%. The limit of detection was less than 0.2 ng g(-1). The feasibility of this method was validated by analysis of incurred egg and tissue samples, and the results were compared with those obtained by the classical method in which solvent extraction, centrifugation, and subsequent clean-up and concentration by solid-phase extraction were applied. The proposed method reduced the complicacy of classical method and improved the reliability of method.

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.

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.

Determination of β-lactam antibiotics in milk based on magnetic molecularly imprinted polymer extraction coupled with liquid chromatography-tandem mass spectrometry

In this work, a rapid and selective method was successfully developed using the magnetic molecularly imprinted polymer (MMIP) as sorbent for the extraction of β-lactam antibiotics (BLAs) from milk samples. The MMIP has been prepared using penicillin V potassium (PENV) as template molecule, methacrylic acid as functional monomer, ethylene glycol dimethacrylate as crosslinking agent and Fe(3)O(4) magnetite as magnetic component. The experimental results showed that the MMIP had high affinity and selectivity toward PENV and other structurally related BLAs. The extraction process was carried out in a single step by mixing the extraction solvent, MMIPs and milk samples under ultrasonic action. When the extraction was completed, the MMIPs adsorbing the analytes were separated from the sample matrix by an external magnet. The analytes eluted from the MMIP were analyzed by liquid chromatography-tandem mass spectrometry. For achieving optimal preconcentration and reducing non-specific interactions, various parameters affecting the extraction efficiency such as extraction mode, extraction solvent, the amount of MMIPs, extraction time, washing solution and eluting solution were comprehensively evaluated. Under the optimal conditions, the detection limits of BLAs are in the range of 1.6-2.8 ng mL(-1). The relative standard deviations of intra- and inter-day ranging from 3.2% to 8.3% and from 3.6% to 9.8% are obtained, respectively. The method was applied to determine BLAs including PENV, amoxicillin and oxacillin in five milk samples from different provenances. The recoveries of BLAs in these samples from 71.6% to 90.7% are obtained.

On-line coupling of dynamic microwave-assisted extraction to solid-phase extraction for the determination of sulfonamide antibiotics in soil.

A rapid technique based on dynamic microwave-assisted extraction (DMAE) coupled on-line with solid-phase extraction (SPE) was developed for the determination of sulfonamides (SAs) including sulfadiazine, sulfameter, sulfamonomethoxine and sulfaquinoxaline in soil. The SAs were first extracted with acetonitrile under the action of microwave energy, and then directly introduced into the SPE column which was packed with neutral alumina for preconcentration of analytes and clean-up of sample matrix. Subsequently, the SAs trapped on the alumina were eluted with 0.3% acetic acid aqueous solution and determined by liquid chromatography-tandem mass spectrometry. The DMAE parameters were optimized by the Box-Behnken design. Maximum extraction efficiency was achieved using 320 W of microwave power; 12 mL of extraction solvent and 0.8 mL min(-1) of extraction solvent flow rate. The limits of detection and quantification obtained are in the range of 1.4-4.8 ng g(-1) and 4.6-16.0 ng g(-1) for the SAs, respectively. The mean values of relative standard deviation of intra- and inter-day ranging from 2.7% to 5.3% and from 5.6% to 6.7% are obtained, respectively. The recoveries of SAs obtained by analyzing four spiked soil samples at three fortified levels (20 ng g(-1), 100ngg(-1) and 500 ng g(-1)) were from 82.6+/-6.0% to 93.7+/-5.5%. The effect of standing time of spiked soil sample on the SAs recoveries was examined. The recoveries of SAs decreased from (86.3-101.9)% to (37.6-47.5)% when the standing time changed from one day to four weeks.

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.

High-throughput dynamic microwave-assisted extraction on-line coupled with solid-phase extraction for analysis of nicotine in mushroom

A simple and low-cost high-throughput dynamic microwave-assisted extraction (HTDMAE) device was firstly assembled and validated by the extraction of nicotine in mushroom samples. In this device, a household microwave oven was applied to provide the microwave energy; a vacuum pump was used to deliver the solvent. Compared with traditional dynamic microwave-assisted extraction method, the sample throughput and microwave energy utilization were improved by the HTDMAE, up to 20 samples could be treated simultaneously in 9 min. Taking extraction of nicotine in mushroom sample as an example, a method was established with extraction, separation and enrichment of nicotine in a single step by the device on-line coupled with solid-phase extraction (SPE). Nicotine was first extracted from the mushroom samples with water under the action of microwave energy, and then directly introduced into the SPE column which was packed with cation-exchange resins. Subsequently, the nicotine trapped on the resins was eluted with methanol-ammonia (95:5, v/v) and determined by high-performance liquid chromatography. The limit of detection of nicotine obtained is 5.6 μg kg(-1) in fresh mushroom sample. The recovery of nicotine in mushroom samples is in the range of 87.4-104.0%. The proposed method which significantly reduced the overall analysis time and increased sample throughput should be favored for routine analyse of complex solid sample.

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.

Automatic sample preparation of sulfonamide antibiotic residues in chicken breast muscle by using dynamic microwave-assisted extraction coupled with solid-phase extraction

In the work, a rapid, simple and high-throughput sample preparation method was developed for the determination of sulfonamide (SA) antibiotic residues in chicken breast muscle. The extraction and clean-up were online combined and up to 20 samples can be treated simultaneously in 6 min. The SAs were first extracted with acetonitrile under the action of microwave energy, and then the extract was directly introduced into the SPE column for on-line clean-up and concentration. Subsequently, the SAs eluted from the SPE column were determined by liquid chromatography-tandem mass spectrometry. The precisions of extraction results of 20 samples were in the range of 4.9-7.4%. The limits of detection and quantification obtained were in the range of 2.4-3.6 ng/g and 8.6-11.3 ng/g for SAs, respectively. The recoveries of SAs obtained by analyzing chicken muscles at three fortified levels (10, 50 and 500 ng/g) were in the range of 82.6-93.2%. The results of the validation process prove that the proposed method is suitable for treating numbers of complex samples simultaneously in a short time.