Sensitive monitoring of penicillin antibiotics in milk and honey treated by stir bar sorptive extraction based on monolith and LC-electrospray MS detection.

In the present study, a convenient and sensitive method for determination of six penicillin antibiotics (amoxicillin, ampicillin, penicillin G, oxacillin, cloxacillin, and dicloxacillin) in milk and honey samples was developed. Milk and honey samples were diluted with water, then directly treated by stir bar sorptive extraction based on poly (vinylimidazole-divinylbenzene) monolithic material as coating. The analytes were analyzed by LC/ESI- MS/MS. Several extraction parameters including extraction and desorption time, pH value, and ionic strength in sample matrix were investigated in detail. Under the optimized extraction conditions, the calculated detection limits for the target compounds were as low as 0.23-2.66 ng/kg in milk and 0.18-1.42 ng/kg in honey, respectively. Good linearity was obtained for analytes with the correlation coefficients (R(2)) above 0.997. Excellent method reproducibility was achieved in terms of intraday and interday precisions, indicated by the RSDs of <5.0 and <10.0%, respectively. Finally, the proposed method was successfully applied to the determination of penicillin antibiotics residues in different milk and honey samples.

Sensitive determination of organic acid preservatives in juices and soft drinks treated by monolith-based stir cake sorptive extraction and liquid chromatography analysis.

A simple, efficient, and sensitive method for simultaneous determination of sorbic acid (SA), benzoic acid (BA), and cinnamic acid (CA) in juices and soft drinks was developed by stir cake sorptive extraction (SCSE) coupling to high-performance liquid chromatography with diode array detection. The SCSE based on polymeric ionic liquid-based monolith (PILM) as extractive medium was used to concentrate these three organic acid preservatives. Because hydrophobic and ion-exchange interactions co-contributed to the extraction, the PILM-SCSE exhibited a high extractive capability towards analytes. To obtain optimum extraction performance, several SCSE parameters were investigated and discussed, including desorption solvent, pH value, ionic strength in the sample matrix, and the extraction and desorption time. Under the optimized extraction conditions, limits of detection of 0.16, 1.08, and 0.18 µg/L (S/N=3) and quantification limits of 0.52, 3.42, and 0.61 (S/N=10) were obtained for SA, BA, and CA, respectively. The method also showed good linearity and reproducibility, as well as advantages such as simplicity, low cost, and high feasibility. Finally, the proposed method was successfully applied to the determination of SA, BA, and CA in real juices and soft drinks, and the recoveries ranged from 63.0 to 107 %.

New monolithic stir-cake-sorptive extraction for the determination of polar phenols by HPLC.

A novel porous monolith has been prepared and used as a sorbent in stir-cake-sorptive extraction (SCSE). The monolithic material was prepared by in-situ copolymerization of allyl thiourea (AT) and divinylbenzene (DB) in the presence of dimethylformamide as a porogen solvent. To optimize the polymerization conditions, different monoliths with different ratios of functional monomer to porogenic solvent were prepared, and their extraction efficiency was investigated in detail. The monolith was characterized by elemental analysis, scanning electron microscopy, mercury intrusion porosimetry, and infrared spectroscopy. Analysis of polar phenols in environmental water samples by a combination of ATDB-SCSE and HPLC with diode-array detection was selected as a model for the practical application of the new sorbent. Several extraction conditions, including extraction and desorption time, pH, and ionic strength of the sample matrix were optimized. The results showed that the new monolith had high affinity for polar phenols and could be used to extract them effectively. Under the optimum conditions, low detection (S/N = 3) and quantification (S/N = 10) limits were achieved for the phenols, within the ranges 0.18-0.90 and 0.59-2.97 µg L(-1), respectively. The linearity of the method was good, and the method enabled simple, practical, and low-cost extraction of these analytes. The distribution coefficients between ATDB and water (K(ATDB/W)) were calculated for the phenolic compounds and compared with K(O/W). Finally, the proposed method was successfully applied to the determination of the compounds in three environmental water samples, with acceptable recovery and satisfactory repeatability.

Preparation of a stir bar sorptive extraction coating based on molecularly imprinted polymer and its application in the extraction of dienestrol and hexestrol in complicated samples.

A new stir bar sorptive extraction (SBSE) coating based on molecularly imprinted polymer (MIP) with diethylstilbestrol as replaced template molecule was prepared. The influences of the contents of template molecule and monomer in the polymerization mixture on the extraction performance of MIP-SBSE were investigated thoroughly. The MIP was characterized by elemental analysis, scanning electron microscopy and infrared spectroscopy. In order to evaluate the usability of the new coating, the MIP-SBSE was combined with high performance liquid chromatography (HPLC) and diode array detector (DAD) with dienestrol (DS) and hexestrol (HS) as detected solutes. To achieve optimally selective extraction performance for DS and HS, several parameters, including extraction and desorption times, desorption solvent, ionic strength and pH value in sample matrix were investigated. The results showed that under the optimized experimental conditions, the present method has high selectivity and sensitivity. When drying-redissolving procedure was taken during sample preparation, the limits of detection for DS and HS were as low as 0.04 microg/L and 0.14 micorg/L, respectively. Good linearities were obtained for analytes with the correlation coefficients (R2) above 0.99. Finally, the proposed method was successfully applied to the determination of DS and HS in wastewater, honey and cow urine samples. The recoveries of spiked target compounds in real samples ranged from 61.3% to 120%. The developed method is simple, selective, sensitive and applicable for the analysis of trace DS and HS in complicated samples.