Ultrasensitive determination of sulfathiazole using a molecularly imprinted electrochemical sensor with CuS microflowers as an electron transfer probe and Au@COF for signal amplification.

In this work, a molecularly imprinted sensor employing copper sulfide (CuS) as a novel signal probe was successfully developed for ultrasensitive and selective determination of sulfathiazole (STZ). The reduction signals of Cu2+ produced in the process of electron transfer of CuS containing large amounts of Cu2+ are easy to be captured, which provide high electrochemical signals. Moreover, gold nanoparticles@covalent organic framework with excellent conductivity was introduced on the electrode surface for signal amplification and facilitating electron transfer processes of CuS. Under optimized testing conditions, the proposed sensor offered a linear DPV response to STZ over a very wide concentration range (1.0 × 10-4 to 1.0 × 10-11 mol L-1), with a limit of detection of 4.3 × 10-12 mol L-1. Fodder and mutton samples spiked with STZ were analyzed using this sensor, and the satisfactory recoveries ranging from 83.0% to 107.2% were obtained. In addition, the proposed sensor was used to determine the concentration of STZ in chicken liver and pork liver, with quantification results being near identical to those determined by high-performance liquid chromatography.

Redox-mediator-free degradation of sulfathiazole and tetracycline using Phanerochaete chrysosporium.

The removal of two of the most commonly used antibiotics, tetracycline (TC) and sulfathiazole (STZ), using laccase-producing Phanerochaete chrysosporium was studied in liquid-phase batch experiments in the absence of any synthetic redox mediator. The removal of STZ and TC from single antibiotic spikes varied from 97.8% to 15.4% and 98.8% to 31%, respectively, with increasing initial doses of 10-250 mg L-1 within 14 days of incubation. The enzyme activity of P. chrysosporium was only minimally influenced by the concentrations of these antibiotics. The degradation of antibiotics initiated before an appreciable extracellular enzyme activity was noted in the fungal culture. The appearance of low-molecular weight molecular fragments from parent antibiotics in liquid chromatography-mass spectrometry confirmed the biodegradation process.

Dual-cloud point extraction coupled to high performance liquid chromatography for simultaneous determination of trace sulfonamide antimicrobials in urine and water samples.

Dual-cloud point extraction (dCPE) was successfully developed for simultaneous extraction of trace sulfonamides (SAs) including sulfamerazine (SMZ), sulfadoxin (SDX), sulfathiazole (STZ) in urine and water samples. Several parameters affecting the extraction were optimized, such as sample pH, concentration of Triton X-114, extraction temperature and time, centrifugation rate and time, back-extraction solution pH, back-extraction temperature and time, back-extraction centrifugation rate and time. High performance liquid chromatography (HPLC) was applied for the SAs analysis. Under the optimum extraction and detection conditions, successful separation of the SAs was achieved within 9min, and excellent analytical performances were attained. Good linear relationships (R2≥0.9990) between peak area and concentration for SMZ and STZ were optimized from 0.02 to 10µg/mL, for SDX from 0.01 to 10µg/mL. Detection limits of 3.0-6.2ng/mL were achieved. Satisfactory recoveries ranging from 85 to 108% were determined with urine, lake and tap water spiked at 0.2, 0.5 and 1µg/mL, respectively, with relative standard deviations (RSDs, n=6) of 1.5-7.7%. This method was demonstrated to be convenient, rapid, cost-effective and environmentally benign, and could be used as an alternative tool to existing methods for analysing trace residues of SAs in urine and water samples.

Short communication: Drug residues in goat milk after prophylactic use of antibiotics in intravaginal sponges for estrus synchronization.

The aim of this study was to determine whether the prophylactic use of antibiotics in intravaginal sponges used for estrus synchronization in goats may result in the presence of inhibitors in milk and, therefore, of positive results by microbial screening tests. Ninety-eight Murciano-Granadina goats were used, divided into 7 groups of 14 animals. Intravaginal sponges were placed in 6 groups using 2 concentrations of 3 different antibiotics: doxycycline, oxytetracycline, and sulfathiazole-framycetin. The sponges of the control group were placed without antibiotics. Milk samples were collected daily until 7 d posttreatment and analyzed using 3 microbial tests. Positive samples were retested by specific receptor-binding assays to confirm the positive results. Vaginal status was evaluated by visual assessment of the external aspect of the sponges after removal. The microbial test response was not affected by either day posttreatment or dose of antibiotic used, except for oxytetracycline at the higher concentration. Moreover, no positive results were obtained using receptor-binding assays, suggesting that residues, if present in milk, did not exceed the regulatory (safety) levels established for these drugs. The occurrence of soiled sponges was higher in the control group. With respect to the dose of antibiotics used, no significant differences were found for the lower dose administered. However, a significant increase in the percentage of clean sponges was observed for the higher dose of doxycycline. We conclude that the prophylactic use of low doses of doxycycline, oxytetracycline, or sulfathiazole in intravaginal sponges used for synchronization of estrus helps to reduce clinical vaginitis in dairy goats and does not seem to be the cause of positive results in microbial inhibitor tests used to detect antibiotics in goat milk.

Sulfathiazole: analytical methods for quantification in seawater and macroalgae.

The awareness of the interconnection between pharmaceutical residues, human health, and aquaculture has highlighted the concern with the potential harmful effects it can induce. Furthermore, to better understand the consequences more research is needed and to achieve that new methodologies on the detection and quantification of pharmaceuticals are necessary. Antibiotics are a major class of drugs included in the designation of emerging contaminants, representing a high risk to natural ecosystems. Among the most prescribed are sulfonamides, with sulfathiazole being the selected compound to be investigated in this study. In the environment, macroalgae are an important group of producers, continuously exposed to contaminants, with a significant role in the trophic web. Due to these characteristics are already under scope for the possibility of being used as bioindicators. The present study describes two new methodologies based on liquid chromatography for the determination of sulfathiazole in seawater and in the green macroalgae Ulva lactuca. Results show both methods were validated according to international standards, with MS/MS detection showing more sensitivity as expected with LODs of 2.79ng/g and 1.40ng/mL for algae and seawater, respectively. As for UV detection the values presented were respectively 2.83µg/g and 2.88µg/mL, making it more suitable for samples originated in more contaminated sites. The methods were also applied to experimental data with success with results showing macroalgae have potential use as indicators of contamination.

Fluorescence interaction and determination of sulfathiazole with trypsin.

The mechanism of interaction of trypsin with the sulfathiazole was studied through using fluorescence quenching and UV-visible absorption spectra at pH 7.4. The Stern-Volmer quenching constants, binding constants, number of binding sites and the corresponding thermodynamic parameters ΔH(o), ΔS(o) and ΔG(o) were calculated at different temperatures. The effect of common metal ions on the constants was also discussed. The results suggest that sulfathiazole can interact strongly trypsin and that there is the formation of trypsin-sulfathiazole complex and the interaction can be explained on the basis of hydrogen bonds and van der Waals forces. The binding distance (r) between the donor (trypsin) and acceptor (sulfathiazole) was 3.52 nm based on the Förster's non-radiative energy transfer theory. The detection and quantification limits of sulfathiazole were calculated as 2.52 and 8.40 µM in the presence of trypsin, respectively. The relative standard deviation (RSD) was 4.086% for determinations (n = 7) of a sulfathiazole solution with the concentration of 7.54 µM.

Effects of copper and aluminum on the adsorption of sulfathiazole and tylosin on peat and soil.

Effects of copper (Cu) and aluminum (Al) on the adsorption of sulfathiazole (STZ) and tylosin (T) to peat and soil were investigated using a batch equilibration method. Results show that Cu suppressed STZ adsorption onto peat and soil at pH < 5.0 because of the electrostatic competition, while increased STZ adsorption at pH > 5.0 due to the formation of STZ-Cu complexes and/or Cu bridge. In contrast, Al only decreased STZ adsorption at pH < 6.0, and exerted slight effect on STZ adsorption at >6.0. As for T, both Cu and Al suppressed its adsorption over the entire pH range owing to three reasons: 1) electrostatic competition between Cu/Al and T(+); 2) Cu/Al adsorption made the soil and peat surface less negatively charged, which was unfavorable for T(+) adsorption; 3) the shrunken pore size of peat and soil retarded the diffusion of large-sized T into these pores.

Distribution of sulfathiazole in honey, beeswax, and honeybees and the persistence of residues in treated hives.

This study was performed to evaluate the distribution and depletion of sulfathiazole in different beehive matrices: honey, honeybees, "pre-existing" honeycomb, "new" honeycomb, and capping wax. Sulfathiazole was dissolved in sugar syrup or directly powdered on the combs, the matrices were sampled at different time points, and sulfathiazole residues were quantified by high-performance liquid chromatography with fluorescence detection. In honey, the higher concentration of sulfathiazole (180 mg kg(-1)) occurred 2 weeks after the last treatment in syrup. In beeswax, drug concentration was higher than in honey, particularly with powder administration, with a maximum level (340 mg kg(-1)) 3 days following the last treatment. The strongest contamination in honeybees (28 mg kg(-1)) was achieved with sulfathiazole administered in powder 3 days after the second treatment. The high persistence of sulfathiazole in the different beehive matrices suggests that it could be a reliable marker of previous treatments performed by beekeepers.

Determination of sulphonamide residues in cattle meats by the Charm-II system and validation with high performance liquid chromatography with fluorescence detection.

The purpose of this study was determination of sulphonamide residues (sulphanilamide, sulphadiazine, sulphathiazole, sulphamerazine, sulphamethazine, sulphamethoxazole, and sulphadimethoxine) in cattle meat by the Charm II technique and the validation of sulphonamide levels by high performance liquid chromatography with fluorescence detector (HPLC-FLD). Of 157 meat samples, 9 samples (5.73%) were found positive by the Charm II method. To make quantitative confirmation of sulphonamide content of positive samples, HPLC-FLD was used and four samples were confirmed as positive. In HPLC analysis, the limit of detection (LOD) was in the range 8-15 µg/kg and the limit of quantification (LOQ) was 13-25 µg/kg. Average recoveries of sulphonamides ranged from 44.6% to 81% with relative standard deviations below 6% (n=6). In conclusion, we consider that the results obtained in field screening by only using the Charm II system, as is common practice in Turkey and worldwide, are inadequate and thus the results should be confirmed by sensitive systems like HPLC.

D-optimal designs and N-way techniques to determine sulfathiazole in milk by molecular fluorescence spectroscopy.

The present work proposes an analytical procedure to determine sulfathiazole in milk by using molecular fluorescence spectroscopy. For this sulfonamide the European Union in Regulation 37/2010 has established a maximum residue limit in milk of 100 µg kg(-1). The study includes the effect of six factors on the recovery of sulfathiazole. The factors are: (i) The one related to the matrix depending on the heat treatment of the milk (UHT, pasteurized); (ii) Those related to the protein precipitation step, namely the ratio between the volume of trichloroacetic acid (TCA) and milk, centrifugation speed and temperature; (iii) Those affecting the derivatization reaction: derivatization time and volume of fluorescamine. To do this, two chemometric tools are used together: a D-optimal design for studying the effect of the factors on the recovery of sulfathiazole, considerably reducing the number of needed experiments; and the second-order property of the PARAFAC (Parallel Factor Analysis) decomposition that avoids the need of fitting a new calibration model each time that the experimental conditions change. It has been found that the type of milk, the TCA:milk ratio and the volume of fluorescamine have significant effect on the response. The rest of factors and interactions are not significant. The best recovery is obtained with UHT milk, 4:6 rate for TCA:milk volumes and 40 µL of fluorescamine. In UHT milk, the mean recovery (n=5) in the optimal conditions is 88.7% (RSD=12.4%). As some non-linear behaviour may occur when using fluorescence spectroscopy, the calibration model that relates the fluorescence spectra with the concentration is computed by a partial least squares regression and a multi-layer feed-forward neural network. In both cases, the proposed procedures have been validated according to Decision 2002/657/EC, concluding that the two are accurate although the calibration model built with the neural network has better figures of merit, the decision limit (CCα) for x(0)=100 µg L(-1) is 103.3 µg L(-1) and the detection capability (CCß) is 106.5 µg L(-1), with the probabilities of false noncompliance (α) and false compliance (ß) equal to 5%.

Investigation of the riddle of sulfathiazole polymorphism.

Since the discovery of sulfathiazole as an antimicrobial agent in 1939, numerous works in the screening for its different polymorphic forms, which is an essential part of drug development, have been conducted and published. These works consequently result in the availability of various methods for generating a particular polymorph. By following these methods, however, one cannot be guaranteed to obtain the intended pure polymorph because most of the methods do not clearly and adequately describe the crystallisation conditions, such as cooling rates and initial solute concentrations. In this paper, the available methods for generating all the known polymorphs of sulfathiazole are reviewed and selected methods for generating certain polymorphs, performed with their processes monitored using process analytical technology tools, i.e. focussed beam reflectance measurement and attenuated total reflectance ultraviolet spectroscopy, are presented. The properties of the obtained crystals, examined using various characterisation methods, are also presented and whenever possible, are compared with those of other workers.

Mobility of veterinary drugs in soil with application of manure compost.

Sulfonamides and tetracyclines are pharmaceuticals widely used to treat human and animal diseases. They are of considerable concern in Korea because of the potential risk of residues in aquatic and terrestrial environments. This study investigated the mobility of veterinary drugs in the soil column with the application of manure compost to assess the risk of groundwater contamination by leaching in the Korean agricultural environment. The degree of sulfonamides and tetracyclines mobility, measured by the concentration of leachates from silty loam soil for 9 days, was observed being on the first day of this study, in the order sulfathiazole, sulfamethazine > sulfamethoxazole > chlortetracycline > oxytetracycline, and the sulfonamides concentrations were about ten times higher than the tetracyclines concentrations with continuous leaching. The results indicate that sulfonamides pose a high risk of ground and surface water contamination and tetracyclines have the potential to persist in soils with bioactive epimers.

[Synthesis and identification of artificial antigens for sulfaguanidine and sulfathiazole].

OBJECTIVE: To prepare artificial antigens of sulfaguanidine and sulfathiazole for detecting sulfaguanidine and sulfathiazole in foods of animal origin. METHODS: The artificial antigens were synthesized by the diazotization methods of coupling sulfaguanidine and sulfathiazole with bovine serum albumin (BSA), and the coupling ratio was 10 : 1 and 9 : 1 respectively. The anti-serum of Balb/c mice was obtained after 5 injections of artificial antigens and the antibody titles were detected by iELISA method. RESULTS: The artificial antigens were identified by infrared spectra, ultraviolet spectra and immunized experimental animals. CONCLUSION: The antigens for sulfaguanidine and sulfathiazole were acquired successfully. The results have laid basis for the specific immunoassay of sulfaguanidine and sulfathiazole.

Quantitative analysis of sulfathiazole polymorphs in ternary mixtures by attenuated total reflectance infrared, near-infrared and Raman spectroscopy.

The simultaneous quantitative analysis of sulfathiazole polymorphs (forms I, III and V) in ternary mixtures by attenuated total reflectance-infrared (ATR-IR), near-infrared (NIR) and Raman spectroscopy combined with multivariate analysis is reported. To reduce the effect of systematic variations, four different data pre-processing methods; multiplicative scatter correction (MSC), standard normal variate (SNV), first and second derivatives, were applied and their performance was evaluated using their prediction errors. It was possible to derive a reliable calibration model for the three polymorphic forms, in powder ternary mixtures, using a partial least squares (PLS) algorithm with SNV pre-processing, which predicted the concentration of polymorphs I, III and V. Root mean square errors of prediction (RMSEP) for ATR-IR spectra were 5.0%, 5.1% and 4.5% for polymorphs I, III and V, respectively, while NIR spectra had a RMSEP of 2.0%, 2.9%, and 2.8% and Raman spectra had a RMSEP of 3.5%, 4.1%, and 3.6% for polymorphs I, III and V, respectively. NIR spectroscopy exhibits the smallest analytical error, higher accuracy and robustness. When these advantages are combined with the greater convenience of NIR's "in glass bottle" sampling method both ATR-IR and Raman methods appear less attractive.

Antibiotic immunosensing: determination of sulfathiazole in water and honey.

The development of two sensitive and selective immunosensors for sulfathiazole, using immunoreagents - haptens, polyclonal antibodies, enzyme conjugates - previously obtained and characterized, is presented. One of them is based on the competitive immunocomplex capture format making use of an immobilized protein A/G sorbent, while the other employs a restricted access support in a novel homogeneous-heterogeneous (HH) assay mode. Maximum sensitivity, achieved with a total assay time of 18min for the capture sensor, is traduced in a dynamic range from 0.4 to 24microgL(-1), with a lower limit of detection of 0.11microgL(-1), increasing to 1.2microgL(-1) when employing an accelerated capture assay protocol that yields a sampling rate of 7 cycles per hour. The HH sensor shows the fastest response, performing each whole assay in only 2min, with a limit of detection of 0.85 and a measurement interval of 3.9-181.0microgL(-1), and with no need of support regeneration. Immunosensors are selective for sufathiazole, and only sulfamethoxypyridazine, sulfamethizole and sulfapyridine show non-negligible cross-reactivity, the same as in ELISA batch immunoassay. The application of the developed systems to the analysis of water, with no sample treatment, as well as honey samples after solid-phase extraction, demonstrate the reliability of the immunosensing for the monitoring of this type of pollutants.

Removal of sulfadiazine, sulfamethizole, sulfamethoxazole, and sulfathiazole from aqueous solution by ozonation.

The removal of sulfadiazine, sulfamethizole, sulfamethoxazole, and sulfathiazole from aqueous solution by ozonation was studied. The study was conducted experimentally in a semi-batch reactor under different experimental conditions, i.e., varying influent ozone gas concentration, bicarbonate ion concentration, and pH. The results of the study indicated that ozonation could be used to effectively remove the sulfonamides from water. The sulfonamides exhibited moderate reactivity towards aqueous ozone, k(O)(3) >2 x 10(4) M(-1)s(-1) at pH of 2 and 22 degrees C. The mol of ozone absorbed by the solution per mol of sulfonamides removed varied in the range of 5.5-12.0 with lower ranges representing ozone absorption by the solution at the beginning of the ozonation process whereas higher ratios correspond to >99.9% removal of the target sulfonamides. The removal rate of the sulfonamides improved with bicarbonate ion concentration up to 8mM but further increase in bicarbonate ion decreased removal efficiency. It was also observed that increasing the pH from 2.0 to 10.0 resulted in enhanced removal of the sulfonamides.

Cation binding of antimicrobial sulfathiazole to leonardite humic acid.

Sorption of sulfathiazole (STA) and three structural analogs to Leonardite humic acid (LHA) was investigated in single- and binary-solute systems to elucidate the sorption mechanism of sulfonamides to soil organic matter (SOM). Cation binding of STA+ to anionic sites A- in LHA governed sorption up to circumneutral pH, based on the following findings: (i) From pH 7.7 to 3.3, the increase in extent and nonlinearity (i.e., concentration dependence) of STA sorption paralleled the increase in STA+. (ii) From pH 3.3 to 1.7, sorption decreased and nonlinearity increased, consistent with strong competition of STA+ and H+ for A-. (iii) Replacement of the protonable aniline group in STA by an apolar methylbenzene group resulted in much weaker, linear, and pH-independent sorption. (iv) Only analogs with aniline moieties displaced STA from LHA in binary-solute systems. Displacement occurred up to pH 5.4, at which <1% of STA in solution was cationic. (v) STA sorption was well-described (R2 = 0.98) by the NICA-Donnan cation-binding model, yielding high median affinities for STA+ to carboxylic and phenolic A- (log K(STA+,1) = 3.25 +/- 0.08 log (L mol(-1)) and log K(STA+,2) = 8.76 +/- 0.11 log (L mol(-1)), respectively). High affinity cation binding explains sorption of polar sulfonamides in agricultural soils and the strong dependence of sorption on SOM content and pH.

Pharmaceutical powders analysis using FT-Raman spectrometry: simultaneous determination of sulfathiazole and sulfanilamide.

A procedure for rapid quantitative analysis of pharmaceutical powders is described. Powdered samples were measured in a rotating cell in order to avoid sub-sampling problems by increasing the irradiated area. Quantitative determination of sulfathiazole and sulfanilamide, using a simple univariate calibration model is proposed. Even though both antibacterials are of the same chemical family (sulfonamides), the richness of structural information contained in the Raman spectra allowed their determination using the area of two selected bands (1255 and 1629 cm(-1) for sulfathiazole and sulfanilamide, respectively). Relative standard deviation (R.S.D.) values (n=10) of 3.35% and 3.46% for sulfathiazole and sulfanilamide, respectively, demonstrate the good reproducibility of the measurement technique with the rotating cell. The method was successfully applied to the analysis of synthetic mixtures and commercial pharmaceutical powders. The procedure is suitable to be applied to pharmacopoeial uniformity of content testing of batches.

[Simultaneous determination of nine sulfonamide residues in milk using solid phase extraction and high performance liquid chromatography].

A simple, rapid, sensitive and reliable high performance liquid chromatographic method for the simultaneous determination of nine sulfonamides (SAs) (sulfadiazine, sulfathiazole, sulfamethazine, sulfamethoxypyridazine, sufamonomethoxine, sulfachloropyridazine, sulfamethoxazole, sulfadimethoxine and sulfaquinoxaline) in milk was developed. The method includes the shaking of the milk with phosphate buffer, centrifugation, and cleaning up on a C18 solid-phase extraction cartridge. The C18 cartridge was washed with water, and the SAs were eluted with methanol. After the evaporation, the residue was dissolved in ethyl acetate, and cleaned up on an amino solid-phase extraction column. Analytical separation was performed on an Inertsil ODS-3 column with photodiode-array detection at 270 nm under the gradient condition. The mean recoveries of SAs at the spiked levels of 10, 20, 40 microg/L were between 72.1% and 88.3%. The relative standard deviations were between 2.3% and 5.0%. The detection limits were 1.7 - 2.8 microg/L, and the quantification limits wer 5.7 - 9.2 microg/L.

[Determination of 12 sulfonamides in cosmetics by ultra performance liquid chromatography].

A method for the determination of 12 sulfonamides (SAs) (sulfanilamide, sulfamonomethoxine, sulfacetamide, sulfamethoxazole, sulfadiazine, sulfisoxazole, sulfathiazole, sulfadi-methoxine, sulfamerazine, sulfaquinoxaline, sulfamethazine, sulfanitran) in cosmetics was developed by ultra performance liquid chromatography with photodiode array detector (UPLC-PDA). The chromatographic column used was Acquity UPLC BEHC C18 (50 mm x 2. 1 mm, 1. 7 microm) and the mobile phase was acetonitrile-0. 1% formic acid aqueous solution. A gradient elution program was utilized for the separation and determination. After liquid-liquid extraction, SAs were separated and detected by UPLC-PDA. The qualification analysis was done by using retention time and spectrum, and the quantification was based on the detection wavelength of 268 nm. The limits of qualification (S/N = 3) and quantification (S/N = 10) for 12 SAs were 1 microg/g and 2 -3 microg/g, respectively. The correlation coefficient of linear calibration curve was over 0. 999 7 within the SAs concentration range of 1 - 25 mg/L (except sulfanitran 0. 5 - 12. 5 mg/L). At the spiked levels of 40 and 8 microg (except sulfanitran 20 and 4 microg), the average recoveries for 12 SAs were 86. 8% - 98. 1% and 80. 1% - 96. 9%, respectively. Relative standard deviations were less than 10%. Routine tests show that the method is simple, fast, and has a good separation efficiency. It can be routinely used for the determination of these SAs in cosmetics.