Abstract
With the prevalent use of various medicines, effluents containing antibiotics have attracted wide attention owing to their potential to cause adverse effects on humans, animals and the ecosystem. Among the many classes of antibiotics, cephalosporins are important broad-spectrum human and veterinary drugs that are extensively used to effectively treat various diseases caused by Gram-positive and -negative bacteria. Overuse of cephalosporin antibiotics can result in their accumulation in environmental water matrices, thus increasing the risks of antibiotic resistance developments when humans consume water that is contaminated by these drugs. Therefore, to reduce the risk of antibiotic resistance caused by cephalosporins, continuous monitoring of water bodies is essential. However, the development of methodologies for the analysis of trace cephalosporin residues in environmental samples is still challenging. Given the above-mentioned reasons, there is a need to develop fast, simple, effective, cost-effective, and sensitive analytical methods for monitoring and determining cephalosporins in various complex water matrices.
Therefore, this study aimed to develop reliable and robust analytical methods based on ultrasound-assisted dispersive solid phase extraction (DSPE) combined with high performance liquid chromatography coupled with a diode array detector (HPLC-DAD) for simultaneous preconcentration and determination of seven cephalosporin antibiotics in various water samples. Mesoporous silica nanoparticles (MCM-41) and waste PET-derived UIO-66 were synthesised, and their surface, morphological, and structural features were characterised using various analytical characterisation techniques. These include X-ray diffraction (XRD), transmission electron microscope (TEM), Fourier-transform infrared spectroscopy (FTIR), high-resolution scanning electron microscopy (HR-SEM), nitrogen adsorption/desorption isotherm and Zeta potential. The XRD patterns proved that the prepared materials were crystalline. The surface area of the MCM-41 was 943 m²/g, which aligns with the mesoporous structure of the adsorbent. The hydrodynamic diameter and zeta potential of the particles were measured as 1250 ± 65 nm and -15 ± 4 mV, respectively, with a polydispersity index of 0.58 ± 0.09. The BET surface area of the waste PET-derived UIO-66 was 732 m2/g, and the particle size proved that the prepared material was microporous. The MCM-41 and waste PET-derived UIO-66 were used as adsorbents for the development of ultrasound-assisted dispersive (micro) solid-phase extraction (UA-D-μ-SPE/UA-DSPE) of cephalosporin antibiotics in water samples.
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Firstly, a UA-D-μ-SPE coupled with the HPLC-DAD method was used for the determination of cefadroxil (CFDX) and cephalexin (CPLX) residues in surface water and wastewater samples. The experimental parameters affecting the UA-D-μ-SPE were investigated using the design of experiments (DOE) approach. The UA-D-μ-SPE/HPLC-DAD method was validated by investigating analytical parameters such as linearity, accuracy, precision, matrix effect, specificity, limits of detection (LODs) and detection (LOQs). The linear range for both analytes ranged from 0.1-600 μg/L, with the correlation of determination between 0.9923 and 0.9993. LODs and LODs were 0.02-0.16 μg/L and 0.067-0.53 μg/L. The intraday accuracy (expressed as %recovery) ranged from 73.5-98.1%, with precision (in terms of relative standard deviation %RSD) being less than 6%. The method was applied to real water samples, and the results revealed that the concentrations of the analytes ranged from 0-1.69 μg/L, 0.78-5.45 μg/L and 1.54-7.33 μg/L in surface water, influent wastewater, effluent wastewater, respectively.
The second objective of this study was to investigate the effectiveness of waste PET-derived UIO-66 adsorbent for UA-DSPE of five cephalosporin antibiotics (cefoperazone, ceftriaxone, cephalothin, cefaclor and cefoxitin) in water samples before HPLC-DAD determination. Under optimised conditions, the effective and rapid detection method showed good linearity (0.1-700 μg/L with correlation coefficient >0.99), low LODs ( 0.026-0.096 μg/L) and LOQs (and 0.09-0.32 μg/L) for cephalosporin antibiotics. Furthermore, acceptable recoveries of five cephalosporin antibiotics in surface water and wastewater samples ranged from 71.4-99.3%, with %RSD< 10%. The investigated cephalosporin antibiotics were not detected in real samples, but the waste PET-derived UIO-66 proved to be a promising adsorbent in UA-DSPE for enrichment of the target analytes.
Ultimately, the developed methods demonstrated to be rapid, simple, robust, eco-friendly (since thy use small amounts of organic solvents (1.0 mL) and adsorbent <100 mg), and reliable for the determination of cephalosporin antibiotics. Therefore, they signify excellent alternatives to the widely used traditional SPE, which is time-consuming and laborious.