A sensitive analysis of sulfadimethoxine using an AuNPs/Ag-GO-Nf-based electrochemical immunosensor

Journal of Solid State Electrochemistry - Herein, a strategy was put forward for high-sensitive detection of sulfadimethoxine (SDM) using a label-free electrochemical immunosensor....     

Organic solvents-free technique for determining sulfadimethoxine and its metabolites in chicken meat

A quick and cost-effective technique of sample preparation followed by a reversed-phase high performance liquid chromatography under "organic solvent-free" (=100% aqueous) conditions for the simultaneous quantifying of sulfadimethoxine (SDM) and its metabolites, 6-hydroxy SDM (6-OH) and N(4)-acetyl SDM (N(4)-Ac), in chicken muscle is presented. Analysis by HPLC with photo-diode array detector was performed using a short C1 column with an isocratic 0.04 mol/l citric acid mobile phase. The method was validated by the analyses of spiked chicken muscle samples, resulting recoveries (> or =84%; relative standard deviations < or =6%), analytical total time (<1/2 h/sample, where a batch of 12 samples in 4 h), and limits of quantitation (< or =0.1 microg/g). The decision limits and detection capability were 0.019-0.106 and 0.054-0.112 microg/g, respectively. No organic solvents were used at all.     

SERS detection of ceftriaxone and sulfadimethoxine using copper nanoparticles temporally protected by porous calcium carbonate

The authors describe a new composite based on SERS-active copper nanoparticles (CuNPs; 10?±?2 nm) incorporated into calcium carbonate microspheres (CaCO₃-CuNPs; 3.4?±?0.3 μm). The CaCO₃ coating acts as a temporal protector of CuNPs against oxidation. Incorporated CuNPs have significantly improved stability during storage and a month-long shelf lifetime. The composite was used for SERS detection of rhodamine 6G and two antibacterial drugs (ceftriaxone and sulfadimethoxine). Two analytical formats, one with and one without solid phase extraction, are introduced to demonstrate the flexibility of the method. Both formats imply the dissolution of CaCO₃ matrix before SERS analysis to release CuNP used as SERS substrate. The study of the influence of pH value and acid nature on the SERS signal demonstrated that HCl is the most efficient candidate to release the CuNPs. Sensitivity (expressed as LOD) is shown to be improved by more than one order when solid phase extraction is used. The average SERS enhancement factor is 10^7 which makes the material efficiency comparable to the one of silver nanoparticles. The LOD (<5 μM), precision (RSDs between 20 and 24% at LOD levels), and trueness (apparent recoveries 84–113%) for the two antibiotics (ceftriaxone and sulfadimethoxine) make the method quite useful for quantitative analysis and therapeutic drug monitoring at physiologically relevant concentrations.

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Graphical abstract A composite with temporally stable copper nanoparticles was synthesized, studied, and used for SERS detection of two antibacterial drugs. The analytical efficiency of the composite was found appropriate for quantitative analysis due to Raman enhancement comparable with silver nanostructures.

     

Simulation of chemical metabolism for fate and hazard assessment. I. Approach for simulating metabolism

Information regarding the metabolism of xenobiotic chemicals plays a central role in regulatory risk assessments. In regulatory programmes where metabolism studies are required, the studies of metabolic pathways are often incomplete and the identification of activated metabolites and important degradation products are limited by analytical methods. Because so many more new chemicals are being produced than can be assessed for potential hazards, setting assessment priorities among the thousands of untested chemicals requires methods for predictive hazard identification which can be derived directly from chemical structure and their likely metabolites. In a series of papers we are sharing our experience in the computerized management of metabolic data and the development of simulators of metabolism for predicting the environmental fate and (eco)toxicity of chemicals. The first paper of the series presents a knowledge-based formalism for the computer simulation of non-intermediary metabolism for untested chemicals, with an emphasis on qualitative and quantitative aspects of modelling metabolism.     

pH-Sensitivity and pH-dependent structural change in polymeric nanoparticles of poly(vinyl sulfadimethoxine)-deoxycholic acid conjugate

pH-Sensitive nanoparticles of poly(vinyl sulfadimethoxine) (PSDM)-deoxycholic acid (DOCA) conjugates were prepared by dialysis at pH 9.0. The average size and the critical aggregation concentration (CAC) of the nanoparticles were 340 nm and 2.5 × 10⁻¹ g/l, respectively. The CAC decreased with decreasing pH as a result of the increase in the hydrophobic nature of the PSDM. Nanoparticle aggregation was observed at pHs ranging from 6.6 to 7.2. The photophysical characteristics of the nanoparticles were examined using a fluorescence probe technique. The microviscosity in the nanoparticle core was measured by 1,6-diphenyl-1,3,5-hexatriene (DPH). The microviscosity changed significantly with decreasing pH from 8.0 to 6.8, indicating a decrease in the rigidity of the inner cores. One interesting feature was that the microviscosity increased sharply at pHs below 6.8. This suggests that in this pH range most of the PSDM became deionized, which caused the reconstitution of new hydrophobic domains inside the nanoparticles.     

Microbial metabolism. Part 5. Dihydrokawain

Preparative scale fermentation of (6S)-dihydrokawain (1) with Rhizopus arrhizus (ATCC 11145) gave 3'-hydroxydihydrokawain (2) and (8S)-hydroxydihydrokawain (3). Structure elucidation of the metabolites was based on spectroscopic data. The C-8 absolute configuration of (3) was assessed via its Mosher's esters.     

High-performance liquid chromatographic analysis of Romet-30 in Chinook salmon (Oncorhynchus tshawytscha): wash-out time, tissue distribution in muscle, liver and skin, and metabolism of sulfadimethoxine

A high-performance liquid chromatographic (HPLC) assay was developed for the determination of Romet-30 residue levels in Chinook salmon muscle and liver tissues. The extraction recoveries averaged 66, 78 and 83% for ormetoprim (OMP), sulfadimethoxine (SDM) and N⁴-acetyl-SDM (N⁴-Ac-SDM), respectively, in muscle tissue; 61 and 72% for SDM and N⁴-Ac-SDM, respectively, in liver tissue. The HPLC assay had a lower detection limit of 0.05 μg/g for OMP, SDM and N⁴-Ac-SDM in muscle tissue, and a lower detection limit of 0.20 μg/g for SDM and N⁴-Ac-SDM in liver tissue. OMP could not be quantified in liver due to the presence of substantial amounts of co-extracted endogenous substances. The HPLC assay was applied to the analysis of Romet-30 residues in Chinook salmon after gastric intubation with Romet-30 at water temperatures between 8.0 and 9.0°C. Different disposition characteristics were found in muscle and liver tissues. The presence of N⁴-Ac-SDM in liver tissue was confirmed by MS and MS-MS analyses. An estimation of SDM and N⁴- Ac-SDM residue levels in skin tissue was obtained and the disposition of these two compounds was similar to the disposition in muscle tissue.     

Rapid high-performance liquid chromatographic determining technique of sulfamonomethoxine, sulfadimethoxine, and sulfaquinoxaline in eggs without use of organic solvents

A determining technique of sulfonamides (SAs) (sulfamonomethoxine (SMM), sulfadimethoxine (SDM), and sulfaquinoxaline (SQ)) in eggs, without use of organic solvents, is developed utilizing a high-performance liquid chromatography (HPLC) interfaced with a photo-diode array detector. The sample preparation was performed by homogenizing with perchloric acid solution using a handy ultrasonic-homogenizer followed by a centrifugal ultra-filtration unit. An analytical column and an isocratic mobile phase for HPLC are a reversed-phase C₄ column ( mm i.d.) and 0.18 mol l⁻¹ citric acid solution, respectively. The proposed technique was shown to be linear (r>0.998) over the concentration range 0.1-2.0 μg g⁻¹. Average recoveries of three SAs (spiked 0.05, 0.1, 0.15, and 0.2 μg g⁻¹) ranged from 80.3 to 88.4%, with relative standard deviations (R.S.D.s) between 3.4 and 5.8%. The practical detection limits and total time required for the analysis of one sample were < 0.05 μg g⁻¹ and <30 min, respectively. In all the processes, no organic solvents were used at all.