[Determination of ten aminoglycoside residues in eggs by mixed-mode ion exchange liquid chromatography-tandem mass spectrometry].

Aminoglycosides (AGs) are a class of broad spectrum antibiotics that have bactericidal activity against some aerobic gram-positive and gram-negative organisms. AGs have been extensively employed in animal husbandry for the treatment of bacterial infections or growth promotion. Many countries have issued strict maximum residue levels (MRLs) for AGs in many animal-origin foods. Analysis of AGs is quite challenging due to their physicochemical properties. The lack of any notable chromophores or fluorophores makes direct detection using ultraviolet (UV) or fluorescence (FLR) spectroscopy unfeasible. Therefore, AGs must be derivatized before they can be analyzed by UV or FLR detection techniques. However, the sensitivity of such derivatization methods is relatively low. Methods based on chromatographic analysis coupled with tandem mass spectrometric detection are emerging as the most common way of identification and quantification. The retention of AGs on reversed-phase column is poor due to the presence of various amino and hydroxyl groups in their structures. Therefore, ion-pair chromatography has reportedly been used to improve the retention of AGs. However, electrospray ionization-mass spectrometric detection was hampered by using an ion pairing reagent due to the suppression of ionization. In this study, a method based on mixed-mode ion exchange liquid chromatography-tandem mass spectrometry was developed for the determination of ten AGs residues (streptomycin, dihydrostreptomycin, hygromycin B, kanamycin, amikacin, tobramycin, apramycin, spectinomycin, neomycin, and gentamycin) in eggs. The main factors governing the method, such as the type of chromatographic column used, the type and proportion of the mobile phase used, mass spectroscopy parameters, type and volume of the extraction solvent used, pH, and the type of solid phase extraction (SPE) column, were investigated during sample pretreatment and instrument analysis. The residues of AGs in the test samples were extracted by ultrasonication with 10 mmol/L ammonium acetate buffer solution (comprising 0.4 mmol/L EDTA and 50 g/L trichloroacetic acid). After adjusting the pH, the AG residues in the sample were purified and enriched using a PRiME HLB SPE column. The target analytes were separated on a SIELC Obelisc R column (150 mm×2.1mm, 5 µm), the column temperature being 40 ℃, the flow rate being 0.3 mL/min, and the injection volume being 5 µL. Gradient elution was carried out with acetonitrile and 1.0%(v/v) formic acid aqueous solution (including 1 mmol/L ammonium formate) as the mobile phases. The detection was performed by electrospray ionization-tandem mass spectrometry (ESI-MS/MS) in multiple reaction monitoring (MRM) mode. The retention times and ionic ratios were used for qualitative analysis, and the peak areas were used for quantitative analysis by the external standard method. Good correlation coefficients exceeding 0.99 were observed for all the AGs in the concentration range of 5-200 µg/L under the optimum conditions. The limits of detection (LODs, S/N ≥ 3) and limits of quantification (LOQs, S/N≥10) for the ten AGs were 2-5 µg/kg and 5-10 µg/kg, respectively. The recoveries ranged from 68.1% to 111.3% (n=6) at three levels (LODs, 20 µg/kg, and 100 µg/kg) in spiked blank egg samples, and the relative standard deviations were 1.2%-12.3%. The matrix effects of the analytes were between 0.3% and 94.3% after purification on the PRiME HLB column. The applicability of the method was validated by analyzing egg samples purchased from local markets. Overall, the method of mixed-mode ion exchange liquid chromatography-tandem mass spectrometry has proven to be a reliable and powerful technique for the simultaneous quantification and confirmation of ten AGs without using an ion pair reagent. Moreover, the clean-up step only required a kind of PRiME HLB sorbent cartridge. The relative parameter data of established method were consistent with GB/T 27404-2008. With simple pretreatment, rapid determination and high sensitivity, the method can be used in the determination of AGs in eggs.

Recent Advances in Three-Dimensional Multicellular Spheroid Culture and Future Development.

Three-dimensional multicellular spheroids (MCSs) have received extensive attention in the field of biomedicine due to their ability to simulate the structure and function of tissues in vivo more accurately than traditional in vitro two-dimensional models and to simulate cell-cell and cell extracellular matrix (ECM) interactions. It has become an important in vitro three-dimensional model for tumor research, high-throughput drug screening, tissue engineering, and basic biology research. In the review, we first summarize methods for MCSs generation and their respective advantages and disadvantages and highlight the advances of hydrogel and microfluidic systems in the generation of spheroids. Then, we look at the application of MCSs in cancer research and other aspects. Finally, we discuss the development direction and prospects of MCSs.

Zirconium (IV)-based metal organic framework (UIO-67) as efficient sorbent in dispersive solid phase extraction of plant growth regulator from fruits coupled with HPLC fluorescence detection.

A stable zirconium (Ⅳ)-based metal organic frameworks (UIO-67) material possessing good chemical, thermal and water stability was synthesized and applied as a sorbent for the dispersive solid phase extraction (DSPE) of 8 plant growth regulators (PGRs) in fruit samples. Fluorescence labeling combined with high performance liquid chromatography fluorescence detection (HPLC-FLD), was used to quantify the target analytes. Characterization of the UIO-67 material was performed by X-ray diffraction(XRD) and scanning electron microscopy (SEM). The experimental parameters, such as amount of UIO-67, type and volume of eluting solvent, adsorption and desorption time, were optimized. Under the optimized conditions, good linearity was observed in the range of 10-1000 pmol/mL with R(2)>0.9989. The limits of detection and limits of quantification were in the range of 0.21-0.57ng/mL and 0.81-1.91ng/mL, respectively. The intra-day and inter-day precisions (based on the relative standard deviation, n=3) of the PGR derivatives were under 3.1% and 5.3% respectively and the accuracies of the method for the PGRs were in the range from 89.3% to 102.3%. The developed method was successfully applied to analyze PGRs residues in fruit samples. The proposed method is proved to be simple, environment-friendly and inexpensive and it is feasible to directly use UIO-67 as sorbent to extract targets by varying conditions.

Determination of thiophenols with a novel fluorescence labelling reagent: analysis of industrial wastewater samples with SPE extraction coupled with HPLC.

A simple, sensitive, and selective high-performance liquid chromatography (HPLC) method using 9-(2-iodoethyl)acridone (IEA) as a novel fluorescence derivatizing agent for the simultaneous determination of six thiophenols has been developed. An efficient Pb(2+)-modified OASIS-MCX cartridge was used and could get good recoveries. IEA was successfully used to label thiophenols with high sensitivity and excellent selectivity. The effects of different solvents, pH, and surfactants on fluorescence properties of derivatives were investigated. To obtain the best labeling efficiency, derivatizing parameters including pH value, temperature, and concentration of IEA, as well as types of catalysts were also evaluated in detail. Under the optimal conditions, the separation could be achieved within 12 min with limits of detection (LODs) in the range of 0.6-5.8 µg L(-1) and relative standard deviations (RSDs) < 3.9%. This is the first time that IEA was applied to the analysis of thiophenols, and the established method has been successfully applied to the trace level detection of thiophenols in industrial wastewater samples.