Antimicrobials in Eisenia fetida earthworms: A comprehensive study from method development to the assessment of uptake and degradation.

In this work, an accurate analytical method was developed for the simultaneous analysis of twenty-seven antimicrobials (AMs) in earthworms using liquid chromatography coupled to a triple quadrupole mass spectrometry detector (UHPLC-MS/MS). Adequate apparent recoveries (80-120 %) and limits of quantification (LOQ) (1 µg·kg-1 - 10 µg·kg-1) were obtained, with the exception of norfloxacin (34 µg·kg-1). The method was applied to evaluate the accumulation of sulfamethazine (SMZ) and tetracycline (TC) in earthworms after performing OECD-207 toxicity test, in which Eisenia fetida (E. fetida) organisms were exposed to soils spiked with 10 mg·kg-1, 100 mg·kg-1 or 1000 mg·kg-1 of SMZ and TC, individually. The results confirmed the bioaccumulation of both AMs in the organisms, showing a greater tendency to accumulate SMZ since higher bioconcentration factor values were obtained for this compound at the exposure concentrations tested. In addition, the degradation of both AMs in both matrices, soils and earthworms was studied using liquid chromatography coupled to a q-Orbitrap high resolution mass spectrometry detector. Thirteen transformation products (TPs) were successfully identified, eight of them being identified for the first time in soil/earthworm (such as 4-Amino-3-chloro-n-(4,6-dimethylpyrimidin-2-yl)benzenesulfonamide or 4-(dimethylamino)-1,11,12a-trihydroxy-6,6-dimethyl-3,7,10,12-tetraoxo-3,4,4a,5,5a,6,7,10,12,12a-decahydrotetracene-2-carboxamide, among others) and their formation/degradation trend over time was also studied. Regarding the biological effects, only SMZ caused changes in earthworm growth, evidenced by weight loss in earthworms exposed to concentrations of 100 mg·kg-1 and 1000 mg·kg-1. Riboflavin decreased at all concentrations of SMZ, as well as at the highest concentration of TC. This indicates that these antibiotics can potentially alter the immune system of E. fetida. This research represents a significant advance in improving our knowledge about the contamination of soil by AM over time. It investigates the various ways in which earthworms are exposed to AMs, either by skin contact or ingestion. Furthermore, it explores how these substances accumulate in earthworms, the processes by which earthworms break them down or metabolise them, as well as the resulting TPs. Finally, it examines the potential effects of these substances on the environment.

Development and validation of method for the simultaneous determination of sulfamethazine, trimethoprim and doxycycline in veterinary formulation using high performance liquid chromatography.

Sulfamethazine (SMZ), trimethoprim (TMP) and doxycycline (DOXY) are drugs of choice used in the treatment of intestinal and respiratory infections that affect poultry and swine. The aim of this study was develop and validate a simple, sensitive and fast method for the simultaneous determination of SMZ, TMP and DOXY in veterinary formulations by high-performance liquid chromatography. The separation was performed on a Macherey-Nagel C8 analytical column (4 × 125 mm, 5 µm), with a flow rate of 0.5 ml min-1 and detection at 268, 270 and 350 nm, for SMZ, TMP and DOXY, respectively. All measurements were performed in acetonitrile-water (45:55 v/v; pH 3.0). The analytical curves were linear (r > 0.9997) in the concentration range of 5.0-35.0 µg ml-1 for SMZ, 1.0-7.0 µg ml-1 for TMP and 7.0-13.0 µg ml-1 for DOXY. The method proved to be precise, robust, accurate and selective. In accelerated stability, the sample was analyzed for 6 months, with no major variations observed in organoleptic analysis and pH. Therefore, the developed method was proved to be suitable for routine quality control analyses for the simultaneous determination of SMZ, TMP and DOXY in pharmaceutical formulations.

Detection of Multiple Antibiotic Residues in Turkish Pine and Blossom Honeys Using LC-MS/MS Method.

Due to the high demand for honey, beekeepers often feed the bees with antibiotics to protect honeybees against illnesses; the determination of veterinary drugs and their residues in bee products especially in honey is gaining importance. In this study, commercially available 15 different brands, a total of 22 honey (14 blossoms and 8 pines) samples obtained from 5 chain supermarkets in the city of Bingöl and Diyarbakir, Turkey were analysed for 29 antibiotic residues. These antibiotics belong to 10 different categories, including tetracyclines, aminoglycosides, macrolides, sulfonamides, fluoroquinolones, benzimidazoles, anthelmintic, amphenicols, quinolines, and oxazolidines. For the qualitative and quantitative determination of the antibiotics, a triple quadrupole liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used. A total of 10 out of 22 honey (8 blossom, 57.14 % and 2 pine, 25 %) samples were found to be positive for antibiotics. Among the tested antibiotics, tetracycline, dihydrostreptomycin, streptomycin, erythromycin, and sulfadimidine were detected in the honey samples. Dihydrostreptomycin and sulfadimidine were detected in 6 samples, erythromycin was determined in 4 samples, streptomycin was found in 2 samples, and lastly, tetracycline was detected only in one sample. The highest and the lowest concentrations of antibiotics detected in the samples were dihydrostreptomycin and erythromycin found at the amount of 992.58 µg/kg and 0.77 µg/kg respectively. The proposed method was validated with a limit of quantification (LOQ) and limit of detection (LOD) ranging between 0.42 and 3.22 µg /kg and 0.13-0.97 µg /kg respectively. Good linearities were also achieved ranging between R2 =0.987 and 0.999.

Identification of sulfamethazine degraders in swine farm-impacted river and farmland: A comparative study of aerobic and anaerobic environments.

Sulfonamides (SAs) are extensively used antibiotics in the prevention and treatment of animal diseases, leading to significant SAs pollution in surrounding environments. Microbial degradation has been proposed as a crucial mechanism for removing SAs, but the taxonomic identification of microbial functional guilds responsible for SAs degradation in nature remain largely unexplored. Here, we employed 13C-sulfamethazine (SMZ)-based DNA-stable isotope probing (SIP) and metagenomic sequencing to investigate SMZ degraders in three distinct swine farm wastewater-receiving environments within an agricultural ecosystem. These environments include the aerobic riparian wetland soil, agricultural soil, and anaerobic river sediment. SMZ mineralization activities exhibited significant variation, with the highest rate observed in aerobic riparian wetland soil. SMZ had a substantial impact on the microbial community compositions across all samples. DNA-SIP analysis demonstrated that Thiobacillus, Auicella, Sphingomonas, and Rhodobacter were dominant active SMZ degraders in the wetland soil, whereas Ellin6067, Ilumatobacter, Dongia, and Steroidobacter predominated in the agricultural soil. The genus MND1 and family Vicinamibacteraceae were identified as SMZ degrader in both soils. In contrast, anaerobic SMZ degradation in the river sediment was mainly performed by genera Microvirga, Flavobacterium, Dechlorobacter, Atopostipes, and families Nocardioidaceae, Micrococcaceae, Anaerolineaceae. Metagenomic analysis of 13C-DNA identified key SAs degradation genes (sadA and sadC), and various of dioxygenases, and aromatic hydrocarbon degradation-related functional genes, indicating their involvement in degradation of SMZ and its intermediate products. These findings highlight the variations of indigenous SAs oxidizers in complex natural habitats and emphasize the consideration of applying these naturally active degraders in future antibiotic bioremediation.

A microbial inhibition assay in microplates using Bacillus licheniformis for detection of enrofloxacin and sulfamethazine in chicken spiked kidney, liver and muscle tissues.

BACKGROUND: The presence of antimicrobial drugs residues in animal products at levels higher than the maximum residue level (MRL) may have adverse effects on consumer health such as allergic reactions and resistance development. Therefore, it is necessary to monitor animal products for the presence of antimicrobial residues. OBJECTIVES: The aim of this study was to evaluate the detection limit of microbial inhibition assay (MIA) in microplate by using of Bacillus licheniformis as indicator microorganism for two antibiotics, enrofloxacin (ENR) and sulfamethazine (SMT), in broiler chicken's kidney, liver and muscle tissue samples. METHODS: Spiked tissues samples for the two antibiotics were analysed separately by this method. The results of the assay were evaluated by the determination of the absorbance after mean 3.47 h of incubation at 45°C. RESULTS: Results showed that the detection limits of MIA for ENR and SMT in kidney (124.03 and 23.21 µg/kg, respectively) and liver (90.02 and 62.03 µg/kg, respectively) as well as SMT in muscle (46.95 µg/kg) were lower than EU (European Union) - MRL, whereas the detection limit for ENR in muscle was slightly higher than MRL (136.3 µg/kg compared to 100 µg/kg MRL). Furthermore, the MIA in the current study was found to be more sensitive to SMT than ENR (92% and 88% sensitivity rate, respectively). No false-positive was observed in the assay. CONCLUSIONS: Based on the results, the MIA investigated in this study had the potential to detect ENR and SMT residues in broiler chicken kidney, liver and muscle tissues at levels below or close to EU - MRL but offered lower capability for the detection of ENR compared with SMT in kidney and muscle tissue samples.

A multiple lateral flow immunoassay based on AuNP for the detection of 5 chemical contaminants in milk.

Melamine (MEL), enrofloxacin (ENR), sulfamethazine (SMZ), tetracycline (TC), and aflatoxin M1 (AFM1) are the main chemical contaminants in milk. It is necessary to detect these miscellaneous chemical contaminants in milk synchronously to ensure the safety of the milk. In this study, a multiple lateral flow immunoassay (LFIA) was developed for the detection of MEL, ENR, SMZ, TC, and AFM1 in milk. Under optimal experimental conditions, the cutoff values were 25 ng/mL for MEL, 1 ng/mL for ENR, 2.5 ng/mL for SMZ, 2.5 ng/mL for TC, and 0.25 ng/mL for AFM1 in milk samples. The limits of detection of LFIA were 0.173 ng/mL for MEL, 0.078 ng/mL for ENR, 0.059 ng/mL for SMZ, 0.082 ng/mL for TC, and 0.0064 ng/mL for AFM1. The recovery rates of LFIA in milk were 83.2-104.4% for MEL, 76.5-127.3% for ENR, 96.8-113.5% for SMZ, 107.1-166.6% for TC, and 93.5-130.3% for AFM1. The coefficients of variation were all less than 15%. As a whole, the developed multiple lateral flow immunoassay showed potential as a highly reliable and excellent tool for the rapid and sensitive screening of MEL, ENR, SMZ, TC, and AFM1 in milk.

Occurrence and distribution of antibiotics in coastal water of the Taizhou Bay, China: impacts of industrial activities and marine aquaculture.

The occurrence, spatial distribution, and source analysis of antibiotics in global coastal waters and estuaries are not well documented or understood. Therefore, the distribution of 14 antibiotics in inflowing river and bay water of Taizhou Bay, East China Sea, was studied. Thirteen antibiotics, excluding roxithromycin (ROM), were all detected in inflowing river and bay water. The total antibiotic concentrations in bay water ranged from 3126.62 to 26,531.48 ng/L, which were significantly higher than those in the inflowing river (17.20-25,090.25 ng/L). Macrolides (MAs) and sulfonamides (SAs) were dominant in inflowing river (accounting for 24.40% and 74.9% of the total antibiotic concentrations, respectively), while SAs in bay water (93.6% of the total concentrations). Among them, clindamycin (CLI) (concentration range: ND-8414 ng/L, mean 1437.59 ng/L) and sulfadimidine (SMX) (ND-25,184.00 ng/L, mean concentrations: 9107.88 ng/L) were the highest in those surface water samples. Source analysis showed that MAs and SAs in the inflowing river mainly came from the wastewater discharge of the surrounding residents and pharmaceutical companies, while SAs in the bay water mainly came from surrounding industrial activities and mariculture. However, the contribution of the inflowing river to the bay water cannot be ignored. The risk assessment showed that SMX and ofloxacin (OFX) have potential ecological risks. These data will support the various sectors of the environment in developing management strategies and to prevent antibiotic pollution.

Quantum Dot Nanobeads Based Fluorescence Immunoassay for the Quantitative Detection of Sulfamethazine in Chicken and Milk.

Sulfamethazine (SMZ) as a broad antibiotic is widely used in livestock and poultry. However, the abuse of SMZ in livestock feed can lead to SMZ residues in food and the resistance of bacteria to drugs. Thus, a method for the detection of SMZ in food is urgently needed. In this study, quantum dot (QD) nanobeads (QBs) were synthesized by encapsulating CdSe/ZnS QDs using a microemulsion technique. The prepared QBs as signal probes were applied in lateral flow immunoassay (LFIA) for the detection of SMZ in chicken and milk. Our proposed method had limits of detection of 0.1138-0.0955 ng/mL and corresponding linear ranges of 0.2-12.5, 0.1-15 ng/mL in chicken and milk samples, respectively. The recovery of LFIA for the detection of SMZ was 80.9-109.4% and 84-101.6% in chicken and milk samples, respectively. Overall, the developed QBs-LFIA had high reliability and excellent potential for rapid and sensitive screening of SMZ in food.

Photoresponsive molecularly imprinted polymers based on 4-[(4-methacryloyloxy)phenylazo] benzenesulfonic acid for the determination of sulfamethazine.

Core-shell structured photoresponsive molecularly imprinted polymers were developed for the determination of sulfamethazine in milk samples. The photoresponsive imprinted polymers were prepared with polymethyl methacrylate containing a mass of ester groups as core, sulfamethazine as template molecules, self-synthesized water-soluble 4-[(4-methacryloyloxy)phenylazo] benzenesulfonic acid as a photoresponsive monomer, and ethylene dimethacrylate as cross-linker. Interestingly, the imprinted polymer can specifically adsorb sulfamethazine under dark and 440 nm irradiation, and release it at 365 nm. A series of adsorption experiments showed that the maximum adsorption capacity reached 12.5 mg⋅g-1 , and the adsorption equilibrium was achieved within 80 min. Moreover, the imprinted polymers display excellent reusability, with almost no performance loss after four times photo-controlled adsorption-release cycles, and the imprinted polymers have excellent selectively for sulfamethazine (imprinting factor  = 3.01). In the end, the imprinted polymers realized effective separation and enrichment of sulfamethazine in milk, with a recovery rate of over 97.5%. The material can be used as a solid-phase extractant in the process of enrichment and separation for the quantitative detection of sulfamethazine in milk samples.

An Ultrasensitive Label-Free Fluorescent Aptasensor Platform for Detection of Sulfamethazine.

PURPOSE: Sulfamethazine (SMZ) exposed in the environment can enter the human body through the food chain and pose a serious threat to human health. Therefore, it is important to develop a rapid and sensitive method for detecting SMZ in environmental samples. In order to fastly and quantitatively detect SMZ in environmental samples, we developed a label-free fluorescent aptasensor based on specific aptamer (SMZ1S) and fluorescence resonance energy transfer (FRET) between gold nanoparticles (AuNPs) and rhodamine B (RhoB). METHODS: In the absence of SMZ, SMZ1S was adsorbed on the surface of AuNPs, which led to dispersion of the AuNPs in high concentration saline solution, thus effectively quenching the fluorescence of RhoB. With the increase of the SMZ concentration, the specific binding of SMZ1S and SMZ led to the aggregation of AuNPs in the presence of NaCl, which reduced the quenching of RhoB fluorescence and increased the fluorescence intensity. The sensitivity and linearity curve of the label-free fluorescent aptasensor were determined with different concentrations of sulfamethazine standard solutions. The specificity of this fluorescent aptasensor was determined by replacing sulfamethazine with different antibiotics. In addition, the actual water and soil samples were spiked and recovered. RESULTS: Under optimized conditions, the proposed fluorescent aptasensor demonstrated a good linear detection of SMZ in binding buffer from 1.25 ng mL-1 to 40 ng mL-1 and the limit of detection was 0.82 ng mL-1. The spiked recoveries for SMZ were 94.4% to 108.8% with a relative standard deviation of 1.8-10.3% in water and soil samples, respectively. CONCLUSION: The label-free fluorescent aptasensor investigated in the current study is a promising tool to detect and quantify SMZ in water and soil samples.

Immunochromatographic assay based on time-resolved fluorescent nanobeads for the rapid detection of sulfamethazine in egg, honey, and pork.

BACKGROUND: Sulfamethazine (SMZ), a veterinary drug widely used in animal husbandry, is harmful to human health when excess residues are present in food. In this study, a fast, reliable, and sensitive immunochromatographic assay (ICA) was developed on the basis of the competitive format by using time-resolved fluorescent nanobeads (TRFN) as label for the detection of SMZ in egg, honey, and pork samples. RESULTS: Under optimized working conditions, this method had limits of detection of 0.016, 0.049, and 0.029 ng mL-1 and corresponding linear ranges of 0.05 to 1.00, 0.05 to 5.00, and 0.05 to 1.00 ng mL-1 in egg, honey, and pork samples, respectively. The recovery experiments showed that the average recoveries ranged from 90.5% to 113.9%, 82.4% to 112.0%, and 79.8% to 93.4% with corresponding coefficients of variation of 4.1% to 11.7%, 7.5% to 11.5%, and 4.8% to 8.7% for egg, honey, and pork samples, respectively. The developed TRFN-ICA was also systematically compared with high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) by analyzing 45 actual samples from egg, honey, and pork. CONCLUSION: Overall, the developed TRFN-ICA had high reliability and excellent potential for the ultrasensitive detection of SMZ for food safety monitoring, also providing a universal platform for the on-site detection of other targets. © 2020 Society of Chemical Industry.

Selection and truncation of aptamers for ultrasensitive detection of sulfamethazine using a fluorescent biosensor based on graphene oxide.

We developed a fluorescent aptamer/graphene oxide (GO)-based biosensor to detect sulfamethazine (SMZ) residues in animal-derived foods. The SMZ-bound aptamers were identified and screened with an improved GO-SELEX technique using non-immobilizing ssDNA library. After seven rounds of selection, six SMZ aptamers were sequenced and analyzed for secondary structure, and their affinity and specificity were assessed by binding assays. The truncated aptamer (SMZ1S: 5'-CGTTAGACG-3') with a unique stem-loop structure showed the highest affinity (Kd = 24.6 nM) to SMZ and was used to develop a GO-based fluorescent aptasensor. The binding mechanism between SMZ1S and SMZ was further analyzed by molecular docking. Under optimal conditions, the fluorescent aptasensor showed low detection limits (0.35 ng/mL) and a wide dynamic linear range (from 2 to 100 ng/mL). The aptasensor was also validated against real samples spiked with SMZ, which showed a fluorescence recovery from 93.9 to 108.8% and a coefficient of variation of < 12.7%. Taken together, these results suggest that this novel aptasensor can be used to sensitively, selectively, and accurately detect SMZ residues in foods. Schematic illustration of fluorescent aptasensor based on aptamer/graphene oxide complex detection of of SMZ.

Salinity-independent dissipation of antibiotics from flooded tropical soil: a microcosm study.

River deltas are frequently facing salinity intrusion, thus challenging agricultural production in these areas. One adaption strategy to increasing salinity is shrimp production, which however, heavily relies on antibiotic usage. This study was performed to evaluate the effect of increasing salinity on the dissipation rates of antibiotics in tropical flooded soil systems. For this purpose, paddy top soil from a coastal Vietnamese delta was spiked with selected frequently used antibiotics (sulfadiazine, sulfamethazine, sulfamethoxazole, trimethoprim) and incubated with flood water of different salt concentrations (0, 10, 20 g L-1). Antibiotic concentrations were monitored in water and soil phases over a period of 112 days using liquid chromatography and tandem mass spectrometry. We found that sulfamethazine was the most persistent antibiotic in the flooded soil system (DT50 = 77 days), followed by sulfadiazine (DT50 = 53 days), trimethoprim (DT50 = 3 days) and sulfamethoxazole (DT50 = 1 days). With the exception of sulfamethoxazole, the apparent distribution coefficient increased significantly (p < 0.05) for all antibiotics in course of the incubation, which indicates an accumulation of antibiotics in soil. On a whole system basis, including soil and water into the assessment, there was no overall salinity effect on the dissipation rates of antibiotics, suggesting that common e-fate models remain valid under varying salinity.

Modular, cost-effective, and portable capillary gradient liquid chromatography system for on-site analysis.

This work demonstrates the development of a compact, modular, cost-effective separation system configured to address a specific separation problem. The principles of the separation are based on gradient capillary liquid chromatography where the system consists of precision stepper motor-driven portable syringe pumps with interchangeable glass syringes (100 µL to 1000 µL). Excellent flow-rate precision of < 1% RSD was achieved with typical flow-rates ranging from 1 µL/min to 100 µL/min, which was ideal for capillary columns. A variable external loop volume and electrically actuated miniature injection valve was used for sample introduction. Detection was based upon a commercial Z-type UV absorbance flow-cell housed within a custom-built cooling enclosure (40 mm x 40 mm) which also contained a UV-LED light-source and a photodiode. System and chromatographic performance was evaluated using linear gradient elution, with day to day repeatability of <1.5% RSD (n = 6) for peak area, and < 0.4% RSD (n = 6) for retention time, for the separation of a 5 component mixture using a 50 mm X 530 µm ID C18 3 µm particle capillary column. The system can run any commercial or in-house packed columns from 50 mm to 100 mm length with IDs ranging from 200 to 700 µm. The developed portable system was operated using custom-built windows-based chromatography software, complete with data acquisition and system control.

FADB-China: A molecular-level food adulteration database in China based on molecular fingerprints and similarity algorithms prediction expansion.

Food adulteration is a growing concern worldwide. The collation and analysis of food adulteration cases is of immense significance for food safety regulation and research. We collected 961 cases of food adulteration between 1998 and 2019 from the literature reports and announcements released by the Chinese government. Critical molecules were manually annotated in food adulteration substances as determined by food chemists, to build the first food adulteration database in China (http://www.rxnfinder.org/FADB-China/). This database is also the first molecular-level food adulteration database worldwide. Additionally, we herein propose an in silico method for predicting potentially illegal food additives on the basis of molecular fingerprints and similarity algorithms. Using this algorithm, we predict 1919 chemicals that may be illegally added to food; these predictions can effectively assist in the discovery and prevention of emerging food adulteration.

Dose and time-dependent response of single and combined artificial contamination of sulfamethazine and copper on soil enzymatic activities.

The widespread contamination of antibiotics and heavy metals results in imbalance in the ecosystem. However, the effect of the interaction between sulfamethazine (SM2) and copper (Cu) on soil enzymatic activities is unclear. Therefore, this study investigated the effect of single and combined artificial contamination of SM2 and Cu (0, 1.6 mmol kg-1 Cu and 0, 0.05, 0.2, 0.8 mmol kg-1 SM2) on soil enzymatic activities (urease, sucrose, phosphatase, and RubisCO). A single application of Cu at a concentration of 1.6 mmol kg-1 inhibited the urease, phosphatase and sucrase activities, while a stimulating effect on RubisCO activity was observed on day 7, 21, and 28 of incubation. The individual application of SM2 at higher concentration exhibited significant inhibition of sucrase, phosphatase, and urease activities while a stimulatory effect on RubisCO activity was observed on day 14 and 21 of incubation. The combined contamination of SM2 and Cu significantly inhibited the activities of urease, sucrase, and phosphatase. The effect of combined contamination of SM2 and Cu on the activity of RubisCO was different. The analysis results of interaction types show that there are synergistic or antagonistic effects between Cu and SM2, and these effects can amplify or reduce the effect of Cu or SM2 on soil enzyme activities. Integrated biological responses version 2 (IBRv2) analysis showed that the combined contamination of Cu and SM2 had a greater inhibitory or stimulatory effect on soil enzyme activities than the single contamination of Cu and SM2, depending upon dose and time.

An exploratory study on the simultaneous screening for residues of chloramphenicol, ciprofloxacin and sulphadimidine using recombinant antibodies.

A recombinant gene CCS consisting of three single genes (CAP-ScFv, CPFX-ScFv and SM2-ScFv) were constructed by PCR with three pairs of primers. The length of CCS gene fragment was 2,260 bp. A recombinant plasmid (pGEX-CCS) was obtained in pGEX-6p-1. pGEX-CCS was induced in E.coli BL21(DE3), and the molecular weight of recombinant fusion protein (GST-CCS) was 108.87 kDa. GST-CCS was successfully applied to analysis of CAP-OVA (CAP-ovalbumin conjugate), CPFX-OVA and SM2-OVA simultaneously. The sensitivity of GST-CCS against three veterinary drugs was tested by indirect ELISA at dilution ratio 1:8000. These findings provide a foundation for the construction of fusion genes with linkers and for the potential development of a rapid screening method for the simultaneous detection of veterinary drug residues.

Nitrogen-doped flower-like porous carbon nanostructures for fast removal of sulfamethazine from water.

The increasing concern for the toxicity of sulfamethazine (SMT) in water requires the establishment of effective water treatment processes to remove it. In this study, a novel adsorbent of nitrogen-doped flower-like porous carbon nanostructures (N-doped FPC) was proposed for the adsorption removal of SMT. The N-doped FPC possessed high surface area, good water dispersibility, and alkaline surface, endowing it with great adsorption efficiency towards SMT. The adsorption equilibrium data can be well fitted by both the Langmuir and Temkin models, and the maximum monolayer adsorption capacity of N-doped FPC was 610 mg g-1 for SMT at 298 K. The N-doped FPC exhibited fast adsorption rate for SMT and adsorption equilibrium reached within only 5 min. The pseudo-first-order model described adsorption kinetics data well and the external mass transport was the rate-limiting step. The thermodynamic parameters (ΔG, ΔH, and ΔS) showed that the adsorption of SMT onto N-doped FPC was a feasible, spontaneous, and endothermic physisorption process. After five consecutive sorption/desorption cycles, the N-doped FPC retained more than 85% adsorption capacity. This study confirmed the promising potential of N-doped FPC as high-performance adsorbents for water purification.

Adsorption/desorption and transport of sulfadiazine, sulfachloropyridazine, and sulfamethazine, in acid agricultural soils.

Batch-type experiments were used to study adsorption-desorption of three sulfonamides: sulfadiazine (SDZ) sulfachloropyridazine (SCP), and sulfamethazine (SMT), in five crop soils, whereas laboratory soil column experiments were employed to obtain data on transport processes. Adsorption results were satisfactorily adjusted to Linear and Feundlich equations, with R2 values above 0.95. Adsorption followed the sequence SDZ < SMT < SCP, showing higher values for soils with higher levels of organic carbon (OC) content. Conversely, desorption was higher in soils with less OC, and lower in soils with higher OC contents. The temporal moment analysis method gave values for the transport parameters τ and R which were significantly correlated with soil parameters related to organic matter, specifically OC and N concentrations. The higher retention of the three sulfonamides in soils with high organic matter content is a relevant fact, with value when programming management practices in agricultural soils, and specifically in relation to the spreading of animal manures, slurries, or waste containing these emerging pollutants.

A novel fluorescence immunoassay based on AgNCs and ALP for ultrasensitive detection of sulfamethazine (SMZ) in environmental and biological samples.

A novel indirect competitive fluorescence immunoassay based on the quenching of I- to silver clusters (AgNCs) was developed for the highly selective and ultrasensitive detection of sulfamethazine (SMZ). In this system, alkaline phosphatase (ALP) was labeled on the secondary antibody (Ab2). And after a competition step, magnesium ascorbyl phosphate could be catalyzed to produce ascorbic acid under the catalysis of ALP. Subsequently, I2 was introduced and further reduced to I- in the presence of ascorbic acid, triggering the fluorescence quenching of AgNCs dispersed in isopropanol (IPA) buffer. More importantly, trace I- could lead to an obvious reduction in fluorescence signal, indicating the sensitivity of this method would be greatly improved. Under the optimal condition, this improved method for the SMZ detection has a lower detection of limit (LOD, 0.05000 µg/L) with a wider range (0.1400-71.71 µg/L). After an evaluation, the fluorescence ELISA proposed in this work has satisfactory accuracy and reliability (recoveries, 84.18-118.6%; CV, 2.03-7.64%), illustrating good performance and great potential for the detection of trace SMZ in environmental and biological samples.