Large volume sample stacking of cationic tetracycline antibiotics toward 10 ppb level analysis by capillary electrophoresis with UV detection

This paper aimed to build up a sensitive CE method for the analysis of tetracyclines (TCs) antibiotics (including tetracycline, chlorotetracycline, oxytetracycline, and doxycycline) with conventional UV detection. Here, the large volume sample stacking was applied to achieve in capillary preconcentration of the targets. To achieve large volume sample stacking, the essential step was a large volume of sample (around 83.3% of total capillary length from inlet to detection window) hydrodynamically loaded. Then, the reserved voltage was added in order to push the sample matrix out of the capillary. Due to different pH between sample solution (pH 4.6) and BGE (pH 11.0), the cationic TCs would turn into negatively charged while the sample matrix was removing from the capillary. Finally, the anionic TCs were stacked at the inlet for the subsequent separation. Although the loss of sample existed during their charge transformation, the LODs could be improved around 40 times than that obtained by normal hydrodynamic injection CE method. Here, the LODs were in the range of 8.1–14.5 μg/L, around 10 ppb that close to the level by electrochemiluminescence or laser‐induced fluorescence detection of TCs by CE. The precision was characterized by RSDs of migration times and peak areas, which were in the range of 0.19–0.24% and 0.97–2.54%, respectively. The recoveries of the developed method were in the range of 95–112% by spiking TCs in the tap water. The proposed inline preconcentration CE method could be a simple, speed, and sensitive method for the quantitative analysis of TCs.     

毛细管电泳用于水产品中五种抗生素的同时测定

用毛细管电泳-紫外检测法同时测定水产品中的四环素(TC)、金霉素(CTC)、土霉素(OTC)、多西环素(DC)及氯霉素(CAP)的含量．研究了缓冲体系的酸度、浓度、添加剂、分离电压、进样时间以及温度等条件对分离的影响,得到了电泳的最优条件．在278nm波长处,分离电压为22kV,20mmol／L磷酸氢二钠-10mmol／L柠檬酸(pH值2．8,含0．25mmol／L Na2EDTA和体积分数为4．0％的吐温-80)运行缓冲液下,上述5种组份在25min内得到完全分离．5种抗生素的质量浓度和电泳峰面积在2．5～300．0mg／L和10．0～300．0mg／L范围内呈现良好的线性,TC、CTC、OTC、DC和CAP的相关系数(r)分别为0．9996、0．9992、0．9993、0．9934、0．9987,检测下限为0．5～1．5μg／mL。该方法灵敏度高,重现性好,操作简便,并已成功用于水产品鲫鱼中的5种抗生素残留的检测。     

Simultaneous determination of tetracyclines and their degradation products in environmental waters by liquid chromatography–electrospray tandem mass spectrometry

A sensitive method was developed for the trace determination of six tetracyclines and ten of their degradation products in influent, effluent, and river waters using liquid chromatography–electrospray tandem mass spectrometry detection, combined with Oasis hydrophilic–lipophilic balance (HLB) cartridge extraction and Oasis mixed-mode strong anion exchange (MAX) cartridge cleanup. Tetracyclines and their products were separated by liquid chromatography in 9.5 min, and the instrument detection limits were generally between 0.03 and 0.1 μg/L except for minocycline (0.5 μg/L). The chromatograms were improved through the MAX cleanup and no apparent matrix effect was found. The recoveries of all the target compounds except for 4-epianhydrochlortetracycline and anhydrochlortetracycline (34–52%) were 75–120% for influent, 61–103% for effluent, and 64–113% for river waters. The method detection limits (MDLs) of the analytes varied in the range of 0.8–17.5 ng/L in all studied matrices. The method was applied for the determination of tetracyclines and their products in a sewage treatment plant (STP) and surface waters in Beijing, China. Oxytetracycline (3.8–72.5 ng/L), tetracycline (1.9–16.5 ng/L), and five products including 4-epitetracycline, 4-epioxytetracycline, isochlortetracycline, anhydrotetracycline, and 4-epianhydrochlortetracycline (5.7–25.3 ng/L) were detected in wastewater, while only oxytetracycline and tetracycline (2.2 and 2.1 ng/L) were detected in surface water samples.     

Fluorescence quantification of tetracycline in the presence of quenching matrix effect by means of a four-way model

In this work, a four-way tensor is used to model the quenching effect in fluorescent measurements. By means of the analysis of excitation-emission matrices obtained in the determination of tetracycline in tea, which acts as quencher, it is shown as the impossibility to use a calibration, or an addition standard based on a three-way model. It is analysed the quencher multiplicative effect made on the tetracycline signal by means of an ANOVA. However, by arranging the experimental data in a four-way tensor, it is viable to perform a calibration based on the parallel factor analysis, PARAFAC, decomposition and a four-way partial least squares, 4-PLS, regression to quantify the tetracycline in the presence of the matrix quencher effect. 4-PLS calibration provides better results. In the range from 40 to 220 μg L⁻¹ gives an average of relative errors in absolute value equal to 8.02% in prediction (3.40% in calibration). The repeatability as standard deviation in this range is 5.08 μg L⁻¹ and the method is accurate, slope and intercept being statistically equal to 1 and 0, respectively when a regression calculated versus true concentration is performed. Moreover, it has a decision limit (CCα) of 13.87 μg L⁻¹ for a probability of false positive, α, equal to 0.05 and a capability of detection (CCβ) of 26.63 μg L⁻¹ (for probabilities of false positive, α, false negative, β, equals to 0.05).     

Simultaneous residue monitoring of four tetracycline antibiotics in fish muscle by in-tube solid-phase microextraction coupled with high-performance liquid chromatography

An on-line simple and rapid method for the simultaneous determination of tetracycline (TC), oxytetracycline (OTC), chlortetracycline (CTC) and doxycycline (DC) residues in fish muscle was developed by coupling in-tube solid-phase microextraction (SPME) to high-performance liquid chromatography (HPLC) with a photodiode array detector. Biocompatible poly (methacrylic acid-ethylene glycol dimethacrylate) monolithic capillary was selected as the extraction medium, and no precipitating protein and removing fat steps were required prior to extraction. In order to optimize the extraction of these compounds, several in-tube SPME parameters were investigated. Simply performed by extracting with 0.01 M EDTA-MacIlvaine buffer solution (pH 4.0) and centrifugation, the sample then could be directly injected into the device for extraction. The limits of detection of tetracycline, oxytetracycline, chlortetracycline and doxycycline were calculated to be 22, 16, 30 and 21 ng/g, respectively. The calibration curves showed linearity in the range of 100-10,000 ng/g with a linear coefficient R² value above 0.9980. Excellent method reproducibility was found by intra- and inter-day precisions, yielding the R.S.D.s less than 4.22% and 5.71%, respectively.     

Chemiluminescence Determination of Tetracyclines via Aluminum Sensitized Fluorescence

Tetracycline, oxytetracycline, doxycycline, and chlortetracycline have been determined by chemiexcitation of the corresponding Al(III) highly fluorescent complex from the permanganate or cerium(IV)-sulphite chemiluminogenic reactions. Limits of detection and ranges of linearity are equal to 0.024, 0.015, 0.014, and 0.050 µg mL^?1 and 0.067–3.20, 0.042–1.70, 0.042–3.00, and 0.103–2.80 µg mL^?1 for tetracycline, oxytetracycline, doxycycline, and chlortetracycline, respectively. Average recovery of tetracyclines from solutions of commercial formulations was equal to 99.8% and the procedure was successfully applied to the determination of tetracyclines in commercial products with mean relative error equal to 3.4% (range 1.4–5.0%).     

Feasibility of Fluorescence Detection of Tetracycline in Media Mixtures Employing A Fiber Optic Probe

Abstract

This work assesses the feasibility of fluorescence detection of tetracycline in very optically dense mixtures of highly fluorescent media ingredients used in tetracycline production by fermentation. The fluorescence measurements are accomplished with a fiber optic probe. Seven different mixtures were examined in this study. Each one contained a nonfluorescent base of nutrients and salts along with one of the following media ingredients at 5 g/100 mL: cottonseed flour, corn gluten meal, soybean flour, distiller 's grains and solubles, corn steep liquor, brewer's yeast, and molasses. The concentration of tetracycline was varied in each mixture and fluorescence measurements were made at every concentration step. Excitation light of 390 nm was used to probe the samples, and emission spectra were obtained over the wavelength range from 400 to 600 nm. In most of the samples studied, the fluorescence intensity in the wavelength range corresponding to background media fluorescence (420–480 nm) decreased as the tetracycline concentration increased. The decreases in the short wavelength range might be explained by the absorption by tetracycline of 390 nm excitation light (in competition with absorption by the media) and/or by absorption of background media fluorescence by tetracycline. Frequently, the maximum emission of the mixtures shifted to longer wavelengths. The maximum approached that of tetracycline (approximately 520 nm). Plots of integrated fluorescence intensity, in the emission wavelength regions of 420-480 nm and 500-560 nm, versus tetracycline hydrochloride concentration reflect these shifts. We have found that the changes in fluorescence intensity in these two wavelength regions during tetracycline addition depend on the identity of the media component in the mixture. For corn meal, soybean, brewer's, and molasses media, the fluorescence in the short emission wavelength range decreases while that in the long region increases. In the case of distiller's and corn steep media, the fluorescence changes very little during tetracycline addition. Finally, in cottonseed medium, the fluorescence increases in both wavelength ranges. The data show that fluorescence can be used to detect tetracycline, at least qualitatively, in the presence of the highly fluorescent media ingredients.     

铕-四环素-TOPO-十二烷基磺酸钠荧光体系及四环素测定的研究

广谱抗菌素四环素是一种亲癌化合物,近年来已成为诊断、治疗肿瘤的一种重要的荧光探针,并用于临床检查和治疗中。已报道的检测四环素的极谱、比色、色谱、紫外分光光度、荧光和微生物等法大多复杂且费时。而四环素能与Eu~(3+)形成稳定螯合物,且四环素-Eu~(3+)-TOPO-十二烷基磺酸钠多元络合物体系能发射很强的Eu~(3+)的特征荧光,所以我们提出了用上述多元络合物荧光体系来检测四环素的新的荧光方法,并将该法用于人体血清和尿中四环素的测定。结果表明,该法的检出限为1.2×10~(-8)mol/L,比Eu~(3+)-四环素二元荧光体系的灵敏度约提高两个数量级,且具有简便、快速等特点。