| Sample preparation has become a key part of the analytical process due to the diversity and complexity of the sample matrix and low amount of analytes in analysis of trace components. Over two-thirds of the analysis time is generally spent on sample preparation. Sample preparation is time consuming, and can directly affect accuracy and precision of the analysis result. Determination of sulfonamides antibiotic residues in animal-derived food belongs to the trace component analysis of in complex samples. Therefore it requires not only a detector with high sensitivity and low detection limit, but also simple, fast, and efficient sample preparation techniques.Because of high extraction capacity and low mass transfer resistance, in tube solid phase microextraction(IT-SPME) can achieve sample analysis of high-throughput.Hence, it is suitable for the sample pretreatment technique of sulfonamides antibiotic.In this study, we used a novel monolithic column with embedded graphene as extraction phase to extract and efficiently enrich sulfonamides antibiotic, and coupled to capillary electrophoresis(CE)- laser induced fluorescence detector(LIF) analysis system. We developed a simple, rapid, sensitive, and environmentally friendly analysis method for detection of sulfonamides antibiotic residues in milk. The main contents of this paper are as follows:Firstly, we designed and established a CE-LIF system, and used it for separation and detection of fluorescamine labeled sulfonamides antibiotic. We utilized a fused silica capillary with diameter of 75 μm as separation channel, and optimized the pH values and the concentration of running buffer as well as the separation electric field strength. The optimal separation parameters were determined as follows: the running buffer was 45.0 mmol/L phosphate buffer(pH 6.8) and the separation electric field strength was 300 V/cm. The sample was injected with a liquid-level difference of 8.0cm between the sample reservoir and waste reservoir for 10 s. Under the optimum experimental conditions, the baseline separation of three sulfonamides was achieved with the resolution of 4.785, 9.581 and 4.517 in 3 min. High column efficiency was obtained with the number of theoretical plates of three sulfonamides ranging from3.24×105/m to 6.66×105/m.Secondly, we used UV initiation methods to prepare methacrylic porous polymer monolithic columns with embedded graphene. We obtained the extraction columnwith high specific surface area and low mass transfer resistance through regulating pore diameter and particle diameter. The morphology of the monolithic columns was studied by scanning electron microscopy. The monolithic columns with embedded graphene were used as the absorbent to extract sample. After desorbting, the sample was derived with fluorescamine. The derivatives were separated and detected by the CE-LIF system. The results indicate that the columns we prepared possess good extraction efficiency on sulfonamides. Good linearitiy was achieved in the range of20.0-500.0 μg/L with correlation coefficient(R2) from 0.9983 to 0.9993. The lower limits of detection(S/N=3) were 2.5-4.7 μg/L. The analytical method of IT-SPME-CE-LIF can satisfy the requirements of low concentration samples detection,and it can realize the analysis of real milk samples with the spiked recoveries of91.1%-94.6%. Sulfamethazine was detected in a real milk sample, and the amount was calculated to be 3.7 μg/L, which was much lower than the maximum residue limit.In this study, an analysis method of IT-SPME-CE-LIF was successfully established for determination of sulfonamides residues in real milk sample. The method is a simple, fast and green approach with high extraction efficiency, high column efficiency, and high sensitivity, which can meet the requirements of the trace components in real food samples. |
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