Screening and determination of sulphonamide residues in bovine milk samples using a flow injection system

R. Rocha C, Teixeira JA, Pereira JAM. Green Extraction Techniques as Advanced Sample Preparation Approaches in Biological, Food, and Environmental Matrices: A Review

Green extraction techniques (GreETs) emerged in the last decade as greener and sustainable alternatives to classical sample preparation procedures aiming to improve the selectivity and sensitivity of analytical methods, simultaneously reducing the deleterious side effects of classical extraction techniques (CETs) for both the operator and the environment. The implementation of improved processes that overcome the main constraints of classical methods in terms of efficiency and ability to minimize or eliminate the use and generation of harmful substances will promote more efficient use of energy and resources in close association with the principles supporting the concept of green chemistry. The current review aims to update the state of the art of some cutting-edge GreETs developed and implemented in recent years focusing on the improvement of the main analytical features, practical aspects, and relevant applications in the biological, food, and environmental fields. Approaches to improve and accelerate the extraction efficiency and to lower solvent consumption, including sorbent-based techniques, such as solid-phase microextraction (SPME) and fabric-phase sorbent extraction (FPSE), and solvent-based techniques (μQuEChERS; micro quick, easy, cheap, effective, rugged, and safe), ultrasound-assisted extraction (UAE), and microwave-assisted extraction (MAE), in addition to supercritical fluid extraction (SFE) and pressurized solvent extraction (PSE), are highlighted.

Preconcentration of sulphonamides in bovine milk by the cloud point extraction method using smartphone-based digital images

Sulphonamides are a group of synthetic antibiotics used specially in veterinary medicine. Among the procedures employed in the sample preparation for sulphonamide determination are liquid-liquid extraction (LLE) and solid-phase extraction (SPE) that use large volumes of organic solvents. Hence, a clean procedure was developed based on preconcentration and cloud point extraction (CPE) without using organic solvents to quantify total sulphonamides in bovine milk. The procedure was optimized as follows: 2 mL of pre-cleaned milk sample, 2 mL of reagent solution and 1 mL of Triton X-114 7% (m/v) were added to a tube, heated in a water bath at 40 °C for 10 minutes and centrifuged at 2950 rcf for 20 minutes. Digital image acquisition was employed directly at the tube without removing the supernatant/aqueous phase. The linear response was observed between 10 and 400 μg L^-1 of total sulphonamides and described by the following equation: S = 2.50 + 0.0514C (μg L^-1) and R = 0.999. The LOD and the CV (n = 11) were estimated to be 10 μg L^-1 and 1.3%, respectively. The main interferents present at their usual concentrations in the sample did not interfere with the results. Spike and recovery tests of total sulphonamides were carried out in UHT and pasteurized milk with recovery values between 73 and 106% and the results obtained for this kind of sample were in agreement with those achieved by a high performance liquid chromatography (HPLC) procedure at the 95% confidence level. The analytical procedure presents an adequate sensitivity to determine total sulphonamides in bovine milk and does not require organic solvents, being aligned to the principles of green chemistry.

Development of a QuEChERS method for simultaneous analysis of antibiotics in carcasses for supplementary feeding of endangered vultures

Antibiotics have been beneficial for human and animal health. However, an excessive use in livestock and a deficient management of the carcasses can lead to adverse effects in the scavengers that ingest them, especially in "supplementary feeding sites" (SFS). The aim of this study was to assess the potential risk of exposure to antibiotics for an endangered population of Cinereous vultures (Aegypius monachus) from southeastern Portugal. Hence, a multi-residue method based on QuEChERs was adapted and validated to analyse, in small volumes of tissues, the most frequent antibiotics used in livestock. The method was applied to 87 samples of liver, muscle and kidney from 7 goats and 25 sheep disposed in SFS. According to questionnaires to farmers, the animals had not been treated with antibiotics, but analyses showed residues in 29% of the samples. Antibiotics were more frequent in goats (42.9%) than in sheep (24.2%), and oxytetracycline and trimethoprim were the most common (both 13.8%). Oxytetracycline, the most common antibiotic for livestock in Portugal, showed the highest concentration (1452.68 ng g^-1). To our knowledge, this is the first study of presence of antibiotics in carrion from SFS. The concentrations of antibiotics in carrion do not seem to pose a risk of acute intoxication for adult Cinereous vultures. However, subtle and likely chronic exposure with unknown health consequences may occur, which requires more research. Moreover, the results of this first study can be used in future studies to assess the risk for avian scavengers.

Rapid Determination of Trace Multiresidues of 18 Sulfonamides in Chicken Eggs Using a Modified QuEChERS Method Coupled with Ultrahigh Performance Liquid Chromatography

A modified QuEChERS method was used and an ultrahigh performance liquid chromatography (UHPLC) method was developed for the rapid determination of 18 kinds of sulfonamide residues in chicken eggs. Sample preparation and cleanup conditions were carefully evaluated, and factors such as the adsorbent type and adsorption condition were key parameters in improving the cleanup. The modified QuEChERS method removed matrix interferences, and the sensitivity of the method increased about 5% for recovery and efficiency of the method. Under the optimized UHPLC method with UV detection, all 18 sulfonamide residues were simultaneously separated and rapidly identified within 15 min. The qualitative and quantitative method limits of the 18 sulfonamide residues were 2.06 to 4.12 and 6.86 to 13.7 μg·kg^-1, respectively. A close linear relationship (R² = 0.990 to 0.999) was observed within the concentration range of 0.10 to 2.25 μg·ml^-1. Recovery was satisfactory (71 to 102%) for all the sulfonamides in three standard spiked levels, with relative standard deviations of <9.7%. After the modified sample pretreatment, the speed of sample pretreatment, purification, and analysis efficiency were all significantly increased. This method is suitable for the rapid detection of multisulfonamide residues in chicken eggs and other animal-derived foods.

A rapid and specific method for the detection of indole in complex biological samples

Indole, a bacterial product of tryptophan degradation, has a variety of important applications in the pharmaceutical industry and is a biomarker in biological and clinical specimens. Yet, specific assays to quantitate indole are complex and require expensive equipment and a high level of training. Thus, indole in biological samples is often estimated using the simple and rapid Kovács assay, which nonspecifically detects a variety of commonly occurring indole analogs. We demonstrate here a sensitive, specific, and rapid method for measuring indole in complex biological samples using a specific reaction between unsubstituted indole and hydroxylamine. We compared the hydroxylamine-based indole assay (HIA) to the Kovács assay and confirmed that the two assays are capable of detecting microgram amounts of indole. However, the HIA is specific to indole and does not detect other naturally occurring indole analogs. We further demonstrated the utility of the HIA in measuring indole levels in clinically relevant biological materials, such as fecal samples and bacterial cultures. Mean and median fecal indole concentrations from 53 healthy adults were 2.59 mM and 2.73 mM, respectively, but varied widely (0.30 mM to 6.64 mM) among individuals. We also determined that enterotoxigenic Escherichia coli strain H10407 produces 3.3 ± 0.22 mM indole during a 24-h period in the presence of 5 mM tryptophan. The sensitive and specific HIA should be of value in a variety of settings, such as the evaluation of various clinical samples and the study of indole-producing bacterial species in the gut microbiota.