Development of HPLC with UV‐VIS Detection for the Determination of the Level of Oxytetracycline in the Biological Matrix

High enrichment and sensitive measurement of oxytetracycline in tea drinks by thermosensitive magnetic molecular imprinting based magnetic solid phase extraction coupled with boron doped carbon dots

As a typical kind of new pollutants, there are still some challenges in the rapid detection of antibiotics. In this work, a sensitive fluorescent probe based on boron-doped carbon dots (B-CDs) in combination with thermo-responsive magnetic molecularly imprinted polymers (T-MMIPs) was constructed for the detection of oxytetracycline (OTC) in tea drinks. T-MMIPs were designed, fabricated and employed to enrich OTC at trace level from tea drinks, and B-CDs were utilized as the fluorescent probe to detect the concentration of OTC. The proposed method exhibited good linear relationship with OTC concentration from 0.2 to 60 μg L-1 and the limit of detection was 0.1 μg L-1. The established method has been successfully validated with tea beverages. Present work was the first attempt application of T-MMIPs in combination with CDs in detection of OTC, and demonstrated that the proposed method endowed the detection of OTC with high selectivity, sensitivity, reliability and wide application prospect, meanwhile offered a new strategy for the method establishment of rapid and sensitive detection of trace antibiotics in food and other matrices.

Sensitive fluorescent detection and micromechanism of Mn-doped CuS probe for oxytetracycline hydrochloride

The novel CuMnS nanoflower fluorescent probe based on Mn-doped CuS was developed to achieve the fluorescence detection of oxytetracycline hydrochloride (OTC), the fluorescent sensor has good selectivity and stability. The doping of Mn significantly increased the fluorescence intensity of CuS, which was above 10 times that of CuS. When the predominant species of OTC molecule was zwitterionic OTC^+/-at the solution pH of about 5.00, the fluorescence quenching efficiency of CuMnS by OTC reached the highest. Through fluorescence lifetime and UV absorption, the sensing mechanism between CuMnS and OTC was found to be static quenching. Moreover, Multiwfn wavefunction analysis program based on density function theory (DFT) calculation was applied to compare the interactions between different OTC species and CuMnS at different pH, to reveal the micromechanism of fluorescence quenching of CuMnS by OTC from the views of atoms. The molecular surface quantitative analysis and basin analysis of different OTC species demonstrated that the N atom and O atoms of tricarbonylamide moiety of zwitterionic OTC^+/- can provide lone pair electrons to form a non-fluorescent ground state complex with CuMnS. Meanwhile, the electrostatic attraction of OTC^+/- with negatively charged CuMnS was also beneficial to the interaction, resulting in the effective fluorescence quenching of CuMnS. This work offers a convenient method for sensitively detecting OTC and broadens the application of CuMnS in the field of fluorescence detection.

Simultaneous analysis of oxytetracycline hydrochloride, lidocaine, and bromhexine hydrochloride in the presence of many interfering excipients

A gradient elution high-performance liquid chromatographic method with a diode array detector is introduced for the first time for the simultaneous estimation of three drugs, namely, oxytetracycline hydrochloride (OXT), lidocaine (LDC), and bromhexine hydrochloride (BRH), in a veterinary formulation (OxyClear® solution) that contains many interfering additives. The method used a C-8 column. The chromatographic eluting solution included acidified water (0.1% trifluoroacetic acid in water) and acetonitrile at a 1-ml/min flow rate and 254 nm as a nominated detection wavelength. The chromatographic process was assessed in terms of linearity, precision, accuracy, LOD, and LOQ. OXT, LDC, and BRH were linear in the range of 1-60, 5-100, and 1-60 μg/ml, respectively. The three drugs were determined successfully without the interference of three excipients having UV absorbances. Furthermore, the purities of the peaks of the three drugs were confirmed by comparing the UV spectra of investigated peaks to the UV reference spectra in Clarke's Analysis of Drugs and Poisons. The greenness value of the method was 0.69 with a faint green-colored pictogram using the AGREE tool. These merits recommend the application of the planned method in QC laboratories for purity testing and concentration assays for the pure drugs and commercial formulations.

Development of a quantum dot-based immunochromatography test strip for rapid screening of oxytetracycline and 4-epi-oxytetracycline in edible animal tissues

A rapid and sensitive immunochromatographic test strip (ICTS) was developed in a competitive format with the quantum dot-conjugated monoclonal antibody specifically to determine the residues of oxytetracycline (OTC) and its metabolite 4-epi-oxytetracycline (4-epi-OTC). Using an ICTS reader, the 50% inhibition concentration (IC₅₀) was found to be 3.41 ± 0.29 ng ml^-1 of OTC in phosphate-buffered saline samples and the detection limit was 0.44 ± 0.05 ng ml^-1. The visual cut-off level of the ICTS is 25 ng ml^-1. The recoveries from tissue samples spiked with OTC of 50-600 μg kg^-1 were 74.2-107.2%, with coefficients of variation below 15%. The method was used to analyse incurred tissue samples, and there was good correlation (R² = 0.999) between the ICTS and high-performance liquid chromatography. These results indicate that ICTS is suitable for the rapid and quantitative detection of OTC and 4-epi-OTC residues in edible animal tissues.