Chromatographic analysis of dithiocarbamate residues and their metabolites in foods employed in dietary exposure studies-a review.

Dithiocarbamates (DTCs) belong to a group of compounds used as fungicides in food production and can be divided into three major groups. Since DTCs easily oxidise and hydrolyse in alkaline and acidic medium respectively, precautions have to be implemented during preparation/homogenisation and extraction of samples. As such, test samples are commonly prepared individually by cutting into small pieces just before the digestion of DTCs with a hot acid to give carbon disulphide (CS2) and the results are expressed as CS2 without any differentiation of individual DTCs. However, individual DTCs have different toxicological potencies whilst their metabolites are more toxic than the parent compound. Apart from the hot digestion method, chromatographic separation of three major groups of DTCs has been developed by a number of different researchers. This review provides a comprehensive examination of sample preparation, extraction, clean-up and chromatographic methods for the determination of individual DTCs and their more toxic metabolites in foodstuffs. Moreover, this review also studies on how dietary exposure of DTCs can be efficiently and effectively estimated using different methods of analysis.

Distribution of organochlorine, organophosphates, carbamate, thiocarbamate, pyrethroids, and strobilurins in surface sediments of the Rio de Ondas watershed by GC-MS.

The determination of some pesticides in surface sediments can provide important information about their distribution in the water column. This work aimed to determine the distribution of the classes of pesticides along the Ondas River's hydrographic basin (ORHB), in eighteen different points, during the dry and rainy periods. The pesticides were extracted from the sediment samples by solid-liquid extraction and then analyzed using a gas chromatograph coupled to mass spectrometry. After the development and validation of the method, nineteen pesticides from the group of organochlorine, organophosphates, carbamate and thiocarbamate, pyrethroids, and strobilurins were quantified in at least one point in the two collection periods, with accuracy varying between 86 and 126%. The average concentrations were 0.020 ng g-1 (carbofuran) to 249.123 ng g-1 (dimethoate) and 0.029 ng g-1 (carbofuran and sulfotep) to 533.522 ng g-1 in the dry and rainy periods, respectively. The results showed a wide distribution of pesticide residues in the ORHB, with higher levels for dimethoate, phenitrothion, and malathion, which may be related to their agricultural use in the region. In Brazil, it does not have specific legislation for maximum permitted values of pesticides in sediment, allowing for inappropriate or prohibited use and, consequently, affecting water quality.

Catechol Dyes-Tyrosinase System for Colorimetric Determination and Discrimination of Dithiocarbamate Pesticides.

A convenient and straightforward method, which is based on catechol dyes and tyrosinase, for colorimetric determination and discrimination of dithiocarbamate pesticides (DTCs) has been fabricated. Three catechol dyes, including pyrocatechol violet (PV), pyrogallol red (PR), and bromopyrogallol red (BPR), were chosen as both substrates and indicators in this method. Tyrosinase can facilitate oxidation of the catechol dyes, altering color and absorbance spectra of the dyes. DTCs can alter the absorbance spectra of the catechol dyes-tyrosinase system due to their inhibitory effects on tyrosinase. As a result, the detection limit of the PV-tyrosinase system on ziram was determined to be 4.5 µg L-1. By implementing PV-tyrosinase, PR-tyrosinase, and BPR-tyrosinase, the colorimetric array successfully distinguished six DTCs (thiram, ziram, diram, ferbam, metiram, and mancozeb) at 5.0 µM using principal component analysis (PCA). The system can also determine ziram and distinguish DTCs in real samples. Furthermore, a smartphone can be used as a detector in this system to improve its real-world applications.

Determination of Carbamates and Thiocarbamates in Water, Soil and Sediment of the Formoso River, TO, Brazil.

Considering the increase in agricultural production in Brazil, the use of pesticides for this production, and that there are no studies on pesticides in the region, the presence of carbamates and thiocarbamates was investigated in different environmental compartments of the Formoso River, TO, Brazil, by UHPLC/MS/MS. The collections were made on the banks of this river, in the area of influence of the agricultural project. The active principles were not found in the soil and sediment samples, only the propoxur principle was found in the water, reaching values of up to 0.025 µg L-1 . It was found that the biodiversity of the Tocantinense savannah is under threat, because even though only one of the substances surveyed, propoxur and its derivatives, has been detected, they are substances of high toxicity and tendency to contaminate surface and groundwater to varying degrees and irreversible damage to different species.

Dissipation pattern and safety evaluation of cartap and its metabolites during tea planting, tea manufacturing and brewing.

There are few studies for risk assessment of cartap and its metabolites, although cartap is easily transformed into metabolites which could induce higher toxicity. This study aimed to investigate the dissipation pattern of cartap and its metabolites during tea planting, manufacturing and brewing for evaluating the safety of cartap pesticide. Cartap metabolites were identified using Q-Exactive Orbitrap mass spectrometry. Half-lives of cartap in fresh tea leaves ranged from 0.49 to 0.59 days. Cartap decreased rapidly with time, and it was degraded into nereistoxin and cartap monothiol during tea production chain. Cartap monothiol residues dissipated rapidly by 98% in three days during tea planting. Nereistoxin had a longer residual period than cartap and it dominated the total residue in made tea after tea manufacturing. Transfer rates of nereistoxin during tea brewing ranged from 78.24% to 121.56%. Therefore, we suggested sum of cartap and nereistoxin residues as maximum residual limits in tea.

Advances in the Detection of Dithiocarbamate Fungicides: Opportunities for Biosensors.

Dithiocarbamate fungicides (DTFs) are widely used to control various fungal diseases in crops and ornamental plants. Maximum residual limits in the order of ppb-ppm are currently imposed by legislation to prevent toxicity problems associated with excessive use of DTFs. The specific analytical determination of DTFs is complicated by their low solubility in water and organic solvents. This review summarizes the current analytical procedures used for the analysis of DTF, including chromatography, spectroscopy, and sensor-based methods and discusses the challenges related to selectivity, sensitivity, and sample preparation. Biosensors based on enzymatic inhibition demonstrated potential as analytical tools for DTFs and warrant further research, considering novel enzymes from extremophilic sources. Meanwhile, Raman spectroscopy and various sensors appear very promising, provided the selectivity issues are solved.

Simultaneous determination of cartap and its metabolite in tea using hydrophilic interaction chromatography tandem mass spectrometry and the combination of dispersive solid phase extraction and solid phase extraction.

Risk assessment of cartap residue in tea should include the exposure of cartap and its metabolite due to rapid degradation of cartap into nereistoxin. Herein, a reliable method for determination of cartap and nereistoxin in tea was developed by hydrophilic interaction chromatography tandem mass spectrometry. Target compounds were extracted with water containing 1% formic acid and 5 mM ammonium formate. The use of dichloromethane effectively removed caffeine. Tea extracts were cleaned up by dispersive adsorbents of octadecylsilane and strong anion exchanger, then further purified using hydrophilic lipophilic balanced solid phase extraction cartridge. Isotopic internal standard was employed to calibrate the loss of analytes during sample preparation and compensate matrix effects. Method validation illustrated excellent linearity, with correlation coefficients (R2) higher than 0.999. Satisfactory recoveries of target compounds spiked in green tea, black tea and oolong tea ranged from 87.6% to 119.9% with intra- and inter-day precisions below 20%. Limits of quantification of cartap and nereistoxin were 10.0 µg kg-1, and limits of detection were 2.0 µg kg-1 for cartap and 4.0 µg kg-1 for nereistoxin. The developed method was applied to determine cartap and nereistoxin in thirty tea samples.

Efficient natural pyrrhotite activating persulfate for the degradation of O-isopropyl-N-ethyl thionocarbamate: Iron recycle mechanism and degradation pathway.

Natural pyrrhotite (NP) shows promising future in activating persulfate (PS) due to its easy availability at a low cost and easy separation. This study discussed the degradation of O-isopropyl-N-ethyl thionocarbamate (IPETC) in NP/PS system. NP-PS system showed the best IPETC mineralization at the initial pH of 6.0 (62.84%). The kinetics study suggested that the IPETC degradation followed the pseudo-first-order equation in the NP-PS system. NP-PS system worked better in bottled water (96.46%) and tap water (85.14%) than river water (31.28%). Combined with Fourier transform-infrared spectroscopy, gas chromatography-mass spectrometry and computational calculation, the degradation products, including acetone, formic acid isopropyl ester and ethylamine, were identified and the degradation pathway of IPETC in NP-PS system was proposed. The S, O and N atoms in IPETC are easier to be attacked by. SO4-Ethylamine and reduced S ions coordinately worked to recycle Fe2+ in NP/PS/IPETC system.

Environmental fate and impact assessment of thiobencarb application in California rice fields using RICEWQ.

Thiobencarb is a commonly used herbicide in Northern California rice fields. Released paddy water containing thiobencarb may pose ecological risks to non-targeted organisms. In this research, the Rice Water Quality Model (RICEWQ) is equilibrium tested and then calibrated using monitoring data at field level. Then it is employed to assess the environmental fate and impacts of thiobencarb in the Colusa Basin, and the effects of different management practices on water use and thiobencarb exposures. The model predicted thiobencarb concentrations from rice fields for multiple years throughout the Basin, using input from California Pesticide Use Reporting (PUR) database, and assessed both the temporal/spatial distribution of thiobencarb exposure and potential acute toxicity on non-target organisms. Our study indicated that RICEWQ can accurately reflect the initial partitioning of thiobencarb in both paddy water and soil phases and capture the dynamics of thiobencarb at field level after calibration. Mandatory water holding is critical for reducing thiobencarb exposure in released paddy water. A thirty-day holding time reduces thiobencarb concentrations by 64% relative to a 6-day holding practice. The geo-spatial pattern of exposure in the study domain indicates the differing extents of pollutant levels and their distribution over space. "Risk zones" for different species were identified based on the geospatial patterns of thiobencarb exposure and the species-specific susceptibilities of various non-target species to thiobencarb.

Pesticide residues in Tunisian table grapes and associated risk for consumer's health.

Sixty-four table grape samples from different regions of Tunisia were collected during three consecutive years (2015-2017). The presence of 96 pesticides, including dithiocarbamates, was assessed. Pesticides identification and quantification were performed by liquid or gas chromatography, coupled to tandem mass spectrometry. All samples contained multiple residues (4 to 24 residues), with an average of 11.6 residues per sample. Individual concentrations of pesticides in grapes ranged from 0.01 to 5.86 mg kg-1. For at least one chemical compound, exceedances of the European Maximum Residue Limits were found in 94% of the samples. To assess the potential risk of pesticides through consumption of grapes, the acute exposure was estimated by the determination of predicted short term intake which is expressed as a percentage of Acute Reference Dose (ARfD), for non-compliances of pesticides. The exceedance of ARfD was associated with carbofuran, carbendazim, chlorpyrifos, deltamethrin, dimethoate and omethoate. Consequently, these pesticides could present a risk for consumer's health.

The false positive effect of residue of sulphur sources on dithiocarbamate analysis based on CS2 measurement.

Turkey plays an important role in the international trade of apricots as it has the largest production rate in the world. Since the sulphurisation process is allowed to be used for different products, the effect of residual sulphur and its compounds (which can be found in products as pesticide residues or additive residues) on the positive detection of carbon disulphide (CS2) still creates a big challenge in international trade. Therefore, the main objective of the present study was to investigate the effects of residues of sulphur or sulphur compounds on dithiocarbamate analysis methods based on CS2 measurement. In this study, apricots were chosen since they contain sulphur residues as a result of the sulphurisation process. Sulphur dioxide and dithiocarbamate analyses were conducted on dried apricots prepared with the sulphurisation process (SA) and without the sulphurisation process (NSA); analysis was by two different accredited laboratories. No of pesticide was applied to either SA or NSA samples. Although some of the NSA samples had

Rapid Colorimetric Detection of Cartap Residues by AgNP Sensor with Magnetic Molecularly Imprinted Microspheres as Recognition Elements.

The overuse of cartap in tea tree leads to hazardous residues threatening human health. A colorimetric determination was established to detect cartap residues in tea beverages by silver nanoparticles (AgNP) sensor with magnetic molecularly imprinted polymeric microspheres (Fe3O4@mSiO2@MIPs) as recognition elements. Using Fe3O4 as supporting core, mesoporous SiO2 as intermediate shell, methylacrylic acid as functional monomer, and cartap as template, Fe3O4@mSiO2@MIPs were prepared to selectively and magnetically separate cartap from tea solution before colorimetric determination by AgNP sensors. The core-shell Fe3O4@mSiO2@MIPs were also characterized by FT-IR, TEM, VSM, and experimental adsorption. The Fe3O4@mSiO2@MIPs could be rapidly separated by an external magnet in 10 s with good reusability (maintained 95.2% through 10 cycles). The adsorption process of cartap on Fe3O4@mSiO2@MIPs conformed to Langmuir adsorption isotherm with maximum adsorption capacity at 0.257 mmol/g and short equilibrium time of 30 min at 298 K. The AgNP colorimetric method semi-quantified cartap ≥5 mg/L by naked eye and quantified cartap 0.1⁻5 mg/L with LOD 0.01 mg/L by UV-vis spectroscopy. The AgNP colorimetric detection after pretreatment with Fe3O4@mSiO2@MIPs could be successfully utilized to recognize and detect cartap residues in tea beverages.

Allergic contact dermatitis caused by dimethylthiocarbamylbenzothiazole sulfide (DMTBS) in canvas shoes: in search of the culprit allergen.

BACKGROUND: During rubber vulcanization, new compounds can be formed. OBJECTIVES: To report a case of allergic shoe dermatitis in which the search for the allergen ultimately led to the identification of dimethylthiocarbamylbenzothiazole sulfide (DMTBS). METHODS: A female presented with eczema on her feet after wearing Sperry Top Sider® canvas sneakers. Patch testing was performed with the European baseline series, additional series, shoe materials, and extracts of shoe materials. Thin-layer chromatography (TLC) was performed for additional patch testing, and high-performance liquid chromatography and gas chromatography-mass spectometry were used for chemical analysis. RESULTS: Positive reactions were found to thiuram mix (+), tetramethylthiuram monosulfide (TMTM) (+), shoe material (+), and shoe extracts in eth. (++) and acetone (+). The extracts did not contain TMTM or other components of thiuram mix. TLC strips yielded a positive reaction (+) to one spot, whereas chemical analysis gave a negative result. Thereafter, a similar sneaker from another patient with shoe dermatitis was analysed, and DMBTS was identified. New extracts of the shoe of our first patient were then also shown to contain DMTBS. DMTBS as culprit allergen was confirmed by positive patch testing with a dilution series with DMTBS. CONCLUSION: DMBTS was identified as the culprit allergen in shoe dermatitis, giving rise to compound allergy. The positive reaction to TMTM was considered to represent cross-reactivity.

Ecotoxicity of 1,3-dichloropropene, metam sodium, and dazomet on the earthworm Eisenia fetida with modified artificial soil test and natural soil test.

1,3-Dichloropropene (1,3-D), metam sodium (MS), and dazomet (DZ) are widely used as preplant soil fumigants to solve soilborne problems. To provide a more scientific and accurate evaluation of 1,3-D, MS, and DZ toxicity to the earthworm Eisenia fetida, modified artificial soil test and natural soil test were studied. The suitable soil moisture to maintain over 90% survival of the earthworms after 4 weeks of treatment in an enclosed system for modified artificial soil test and natural soil test were 26.9 to 86.4% of water-holding capacity (WHC) and 66.2 to 84.3% of WHC, respectively. The optimal soil moisture levels for modified artificial soil test and natural soil test (75 and 55% of WHC, respectively) were finally used to evaluate the toxicity of 1,3-D, MS, and DZ on earthworms. Each desiccator with 10 earthworms and natural or artificial soil was stored at 20 ± 1 °C under constant light of 400 to 800 lx for 2 weeks. The modified artificial soil test showed LC50 values for 1,3-D, MS, and DZ of 3.60, 1.69, and 5.41 mg a.i. kg-1 soil, respectively. The modified natural soil test of the fumigants showed similar LC50 values of 2.77 and 0.65 mg a.i. kg-1 soil, except for DZ at 0.98 mg a.i. kg-1 soil. The present study confirms that both modified artificial soil test and modified natural soil test offer standard methods for acute toxicity test of 1,3-D, MS, and DZ on the earthworms and scientific evidences for assessing the effects of soil fumigants on non-target organisms in the soils. Graphical Abstract Two novel acute toxicity test methods for soil fumigants on the earthworm Eisenia fetida.

Simultaneous determination and identity confirmation of thiodicarb and its degradation product methomyl in animal-derived foodstuffs using high-performance liquid chromatography with fluorescence detection and tandem mass spectrometry.

A high-performance liquid chromatography-fluorescence detection method was developed for the simultaneous determination of thiodicarb and its degradation product methomyl in animal-derived food products, including chicken muscle, beef, pork, table eggs, and milk. Thiodicarb is known to degrade during analysis; therefore, a thorough investigation was carried out, revealing that thiodicarb degrades to methomyl immediately after spiking into a matrix of animal-derived food products. Consequently, thiodicarb was determined as the sum of the parent compound and methomyl. Samples were extracted with acetonitrile and sodium salts, and purified using solid-phase extraction (SPE). The limits of detection (LODs) and quantification (LOQs) were 0.0013 and 0.004mg/kg, respectively, for both analytes in various matrices. Seven-point external calibration curves were obtained, and they showed excellent linearity with determination coefficients (R2)≥0.999 for all tested matrices. The method was validated at three fortification levels (LOQ, LOQ×2, and LOQ×10) in triplicate with average recoveries ranging from 84.24 to 112.8% (for methomyl) and relative standard deviations (RSDs)≤6.5% in all matrices. The converted recoveries of thiodicarb in various matrices ranged from 74.80 to 107.80% with RSDs≤4.5%. The identities of both compounds in standard solutions and for recovery were confirmed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The developed method was further validated by accurate reproduction at another laboratory. Finally, the method was applied to market samples collected from different areas (and, in the case of milk, different brands), and none of the samples tested positive for thiodicarb or methomyl. In conclusion, the developed method can be successfully applied for a single-run analysis of thiodicarb and methomyl in livestock products.

Inorganic selenium speciation analysis in Allium and Brassica vegetables by ionic liquid assisted liquid-liquid microextraction with multivariate optimization.

A highly sensitive vortex assisted liquid-liquid microextraction (VA-LLME) method was developed for inorganic Se [Se(IV) and Se(VI)] speciation analysis in Allium and Brassica vegetables. Trihexyl(tetradecyl)phosphonium decanoate phosphonium ionic liquid (IL) was applied for the extraction of Se(IV)-ammonium pyrrolidine dithiocarbamate (APDC) complex followed by Se determination with electrothermal atomic absorption spectrometry. A complete optimization of the graphite furnace temperature program was developed for accurate determination of Se in the IL-enriched extracts and multivariate statistical optimization was performed to define the conditions for the highest extraction efficiency. Significant factors of IL-VA-LLME method were sample volume, extraction pH, extraction time and APDC concentration. High extraction efficiency (90%), a 100-fold preconcentration factor and a detection limit of 5.0ng/L were achieved. The high sensitivity obtained with preconcentration and the non-chromatographic separation of inorganic Se species in complex matrix samples such as garlic, onion, leek, broccoli and cauliflower, are the main advantages of IL-VA-LLME.

Production of microparticles of molinate degrading biocatalysts using the spray drying technique.

Previous studies demonstrated the capability of mixed culture DC1 to mineralize the thiocarbamate herbicide molinate through the activity of molinate hydrolase (MolA). Because liquid suspensions are not compatible with long-term storage and are not easy to handle when bioremediation strategies are envisaged, in this study spray drying was evaluated as a cost-effective method to store and transport these molinate biocatalysts. Microparticles of mixed culture DC1 (DC1) and of cell free crude extracts containing MolA (MA) were obtained without any carrier polymer, and with calcium alginate (CA) or modified chitosan (MCt) as immobilizing agents. All the DC1 microparticles showed high molinate degrading activity upon storage for 6 months, or after 9 additions of ∼0.4 mM molinate over 1 month. The DC1-MCt microparticles were those with the highest survival rate and lowest heterogeneity. For MA microparticles, only MA-MCt degraded molinate. However, its Vmax was only 1.4% of that of the fresh cell free extract (non spray dried). The feasibility of using the DC1-MCt and MA-MCt microparticles in bioaugmentation processes was assessed in river water microcosms, using mass (g):volume (L) ratios of 1:13 and 1:0.25, respectively. Both type of microparticles removed ∼65-75% of the initial 1.5 mg L(-1) molinate, after 7 days of incubation. However, only DC1-MCt microparticles were able to degrade this environmental concentration of molinate without disturbing the native bacterial community. These results suggest that spray drying can be successfully used to produce DC1-MCt microparticles to remediate molinate polluted sites through a bioaugmentation strategy.

Fenton degradation of Cartap hydrochloride: identification of the main intermediates and the degradation pathway.

The advanced oxidation of Cartap hydrochloride (Cartap) promoted by the Fenton system in an aqueous medium was investigated. Based on total organic carbon, chemical oxygen demand and high-performance liquid chromatography, the oxidation of Cartap is quite efficient by the Fenton system. Its long chain is easily destroyed, but the reaction does not proceed to complete mineralization. Ion chromatography detection indicated the formation of acetic acid, propionic acid, formic acid, nitrous acid and sulfuric acid in the reaction mixtures. Further evidence of nitrogen monoxide and sulfur dioxide formation was obtained by using a flue gas analyzer. Monitoring by gas chromatograph-mass spectrometer demonstrated the formation of oxalic acid, ethanol, carbon dioxide, and L-alanine ethylamide. Based on these experimental results, plausible degradation pathways for Cartap mineralization in an aqueous medium by the Fenton system are proposed.

Pesticide residues in stone fruits from the south-eastern region of Poland in 2012-2104.

BACKGROUND: Peaches, sour cherries, nectarines, apricots, plums and cherries are fruit commonly known as "stone fruit". Their nutritional properties namely, vitamins, minerals, fiber and numerous microelements, make them a very important component of human diet. As fruit trees can be attacked by numerous diseases and pests, chemical protection of these crops is used. Therefore, it is important that the relevant governmental agencies or institutions ensure correct application of pesticides. OBJECTIVE: The aim of the study was to evaluate the occurrence of pesticide residues in stone fruits south-eastern region of Poland in 2012-2014 in order to provide data to estimate health risk to consumers. MATERIAL AND METHODS: Validated analytical methods based on liquid / liquid extraction coupled with gas chromatography with electron capture and nitrogen phosphorus detection (GC-ECD/NPD) and spectrophotometry (dithiocarbamates residues) were used for the analysis. 92 samples of stone fruits were tested for the presence of pesticide residues. RESULTS: 13 of all samples (14%) contained pesticide residues. 7 active substances were detected, including 5 fungicides: boscalide, bupirimate, difenoconazole, dithiocarbamates and captan, and 2 insecticides: cypermethrin and pirimicarb. In the analysed samples, the use of not recommended plant protection products in orchard crops were found. However, neither maximum residue levels (MRLs) recommended by the Regulation (EC) No 396/2005 were exceeded nor pesticides being unapproved by the Regulation (EC) No 1107/2009 detected in the analysed samples. CONCLUSIONS: Lack of plant protection products for control specific diseases or pests in crops results in the use of formulations not recommended for use in certain orchard crops. On a basis of results reported in previous years it can be concluded that occurrence of pesticide residues in stone fruit samples dropped significantly.

Fate of thiodicarb and its metabolite methomyl in sandy loam soil under laboratory conditions.

Fate of thiodicarb and its major metabolite in sandy loam soil were studied by applying thiodicarb (Larvin 75 WP) at 500 and 1000 g a. i. ha(-1) under laboratory conditions. Samples drawn periodically were analysed on GC-FTD equipped with capillary column. The average initial deposits of total thiodicarb (thiodicarb and methomyl) were 0.025 and 0.035 mg kg(-1) at single and double dosages, respectively. Residues of thiodicarb reached below the determination level (BDL) of 0.005 mg kg(-1) after 15 days. Half-life periods for total thiodicarb were calculated to be 5.90 and 8.29 days at two doses, respectively, following first-order kinetics.