Stability of nitrofuran residues during honey processing and nitrofuran removal by macroporous adsorption resins

The Influence of Chemical Contaminants on the Physicochemical Properties of Unifloral and Multifloral Honey

The aim of this study was to evaluate and compare the effect of antibiotic and pesticide residues on the physicochemical properties of unifloral and multifloral honey. The mineral elements content of honey was analyzed and correlated with antibiotic and pesticide residues, and a positive correlation was found between manganese and neonicotinoids. Potassium was found to be the most abundant mineral compound. Correlations were found between mineral content, color, and the content of antibiotic and pesticide residues of honey. In meadow honey, residues of antibiotics and pesticides were undetectable. In some of the other types of honey, the maximum residue limits regulated by European legislation were exceeded. Endosulfan residue was found in mint and rapeseed, honey with 0.42 and 5.14 ng/g, respectively. Neonicotinoids were found in 27% of the analyzed honey samples. Chloramphenicol was identified only in rapeseed honey, with concentrations ranging from 0.2 ng/g to 0.8 ng/g. Nitrofurans were found in 14%, and nitroimidazoles were found in 6% of the analyzed samples. According to EU legislation that is in force, the use of antibiotics in beekeeping is not allowed. The MRLs for neonicotinoids are 50 ng/g, and for coumaphos, the maximum limit is 100 ng/g. For the other pesticide residues, the maximum limit is 10 ng/g. The results of statistical analysis obtained using principal component analysis (PCA) showed a major difference in the levels of contamination of raspberry and meadow honey and the other types of honey.

Evaluation of ELISA kits for the screening of four nitrofuran metabolites in aquaculture products according to the European guideline for the validation of screening methods

The administration of nitrofurans to livestock to treat or prevent animal diseases has been banned in the EU for the production of food of animal origin. The corresponding marker residues are tissue-related metabolites AMOZ, AHD, SEM, and AOZ. The MRPL (minimum required performance limit)/RPA (Reference point for action) was set at 1 µg kg^-1 in the EU. Thus, all the laboratories involved in the control of nitrofuran metabolites must detect at least at this analytical limit of performance. The objectives of the work reported here were to evaluate the performance of ELISA kits from two different manufacturers (R-Biopharm, Germany; Europroxima, the Netherlands) for the individual screening of the four nitrofuran metabolites (AOZ, AMOZ; AHD; and SEM) in aquaculture products (fish, shrimps), and then to validate the kits according to the European Decision EC/2002/657 and to the European guideline for the validation of screening methods. The false positive rates were below 9 % for the kits from both manufacturers. The detection capabilities CCβ determined were all below the current RPA (1 µg/kg). However, regarding the updated RPA at 0.5 µg/kg that shall apply in 2022, the AMOZ and SEM kits from R-Biopharm and the SEM kit from Europroxima will not be able to reach it.

Experimental conditions of differential reactor method for resin–phenolic compound system

For the design of a fixed-bed reactor, intraparticle diffusivity of adsorbents is one of the most important parameters. However, determining this diffusivity is difficult as measuring the effects of fluid film resistance of adsorbents. Shallow-bed (differential reactor) technique is commonly used to determine intraparticle diffusivity. The conventional shallow-bed technique is based on the assumption that fluid film resistance is negligible because of high fluid velocity; hence, the fluid film mass transfer is not calculated. For an activated carbon–phenolic compound system, both intraparticle diffusivity and fluid film mass transfer coefficient were determined using a shallow-bed reactor. However, no one has confirmed the accuracy of the conventional assumption for a synthetic resin adsorbent–phenolic compound system. In general, synthetic resin adsorbents have a larger fluid film resistance than activated carbon. Therefore, this study focused on the effect of fluid film resistance based on the conventional assumption. The conventional analysis method (intraparticle diffusion controlling model) and the new analysis method (both intraparticle diffusion and fluid film mass transfer controlling model) were compared, and the results indicated that the conventional assumption, which neglects the elimination of fluid film resistance, had no effect on intraparticle diffusivity. Therefore, the conventional analysis method is useful for determining intraparticle diffusivity for a resin adsorbent–phenolic compound system.

Preparation of a novel chloromethylated polystyrene-2-mercapto-1,3,4-thiadiazole chelating resin and its adsorption properties and mechanism for separation and recovery of Hg(II) from aqueous solutions

With an efficient methodology, a novel chloromethylated polystyrene-g-2-mercapto-1,3,4-thiadiazole chelating resin (MTR resin) was prepared via a one-step reaction. The structure of MTR resin was characterized by elements analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy. Meanwhile, the adsorption properties of the resin for Hg(II) were investigated by batch and column experiments. The results showed that the resin possessed much better adsorption capability for Hg(II) than for other metal ions. The statically and the dynamic saturated adsorption capacities were 343.8 mg/g and 475.1 mg/g. The adsorption kinetic and equilibrium data were well fitted to the second-order model and the Langmuir isotherm model, respectively. Desorption of mercury from the resin can be achieved using 30 mL of 2 mol/L HCl-5% thiourea solution with a desorption ratio of 92.3%. Compared with other absorbents, MTR resin was greatly conserve natural resources and reduce the cost.

Light-sensitive drugs in topical formulations: stability indicating methods and photostabilization strategies

Photostability tests applied on commercial specialties for topical use have demonstrated a greater vulnerability of several drugs, due to greater exposure to light than other pharmaceutical forms. Photodegradation of a drug can considerably modify its pharmacokinetic behavior by varying the therapeutic index. The evaluation of the degradation profile of a drug, according to the ICH rules, is of primary importance in developing an appropriate topical formulation. Advanced strategies have been proposed to increase the protection from the light of the photolabile drugs. Supramolecular systems have been investigated to improve both pharmacokinetic profile and photostability. In this review, the more recent stability-monitoring methods for the analysis of drugs in topical formulations are collected and the main approaches for the drug photostabilization are discussed.

Synthesis and characterization of a novel chloromethylated polystyrene-g-2-adenine chelating resin and its application to preconcentrate and detect the concentration of mercury ions in edible mushroom samples

Edible mushrooms are widely usedtoday but the heavy metal pollution of edible mushrooms is not conducive to its industrialization. A novel chloromethylated polystyrene-g-2-adenine chelating resin (AR resin) with simple technology, high adsorption capacity, significant selectivity, and good regenerability was synthesized. Combined with the UV-Vis method, it was applied to mercury preconcentration and determination. The results indicated that the AR resin is essentially free from interferences, which can contribute to accurate determination in waters and foods. Optimization of the resin synthesis was carried out by using response surface methodology. The adsorption properties of the resin for Hg(II) were investigated by batch and column experiments. The statically and dynamic saturated adsorption capacities were 383.4 and 417.0 mg/g. The adsorption kinetic and equilibrium data were well fitted to the second-order model and the Langmuir isotherm model, respectively. Furthermore, the resin and its metal complexes were studied by Fourier transform infrared spectroscopy and thermogravimetric analysis.