Comparison of HILIC columns for residue analysis of dithiocarbamate fungicides

Sample Preparation Methods for Metal Containing Pesticides in Food and Environmental Samples

Metal-containing pesticides are used in many areas for purposes such as harvest efficiency and keeping pests away from the vegetable environment. Metal-containing pesticides are in the form of dithiocarbamate complexes and are named differently according to the type of metal they contain and are used for different purposes. Since the presence of these pesticides even at residue level threatens human and environmental health, their determination at trace level is important. In this review, studies on the determination of metal-containing dithiocarbamate pesticides in different matrices are discussed. This review on the analysis of dithiocarbamate pesticides with different techniques will shed light on the studies to be carried out for the determination of these pesticides one by one in different matrices.

Development and validation of a GC-MS method for analysis of Dithiocarbamate Fungicide residues in the Spices Cardamom (Elettaria cardamomom) and black pepper (Piper nigrum)

Dithiocarbamates constitute an important class of broad-spectrum antifungal compounds used extensively in agriculture, including in the cultivation of spices. Maximum residue limits for these compounds have been enforced by several importing countries in international food trade. Validation of analytical methods for dithiocarbamates in spices have not been reported previously. A quick and sensitive method for estimation of total dithiocarbamates as carbon disulphide (CS2) using GC-MS in two major spices, viz. small cardamom (Elettaria cardamomom) and black pepper (Piper nigrum) was optimized and validated. Dithiocarbamate residues in these spice matrices were extracted and subjected to acid hydrolysis followed by reduction to CS2, which was then quantitatively absorbed into isooctane and analysed using GC-MS, employing selected ion monitoring and post-run mid-column backflush technique. For fortification levels from 0.1 to 1.0 mg kg- 1, recoveries obtained ranged from 75 to 98% in cardamom and 76-98% in black pepper, with intra-day precision (RSDr) < 12% and inter-day precision (RSDR) < 15% in all cases. Limit of Quantification of 0.05 mg kg- 1 was achieved in both spices. It was found that there was negligible interference in quantitative accuracy due to essential oils present in the two spices studied. Matrix effect was seen to be suppressive in the two spices studied, and sufficiently low to exclude the use of matrix-matched calibration in routine quantitative analysis. The optimized analytical method was found to be suitable for evaluation of compliance of real samples against the Codex maximum residue limits for cardamom and black pepper. Safety evaluation for human consumption, based on the incidence of Dithiocarbamate residues, was performed in real samples of cardamom and black pepper. This method offers the possibility of extending applicability to other spices also.

Supplementary information

The online version contains supplementary material available at 10.1007/s13197-022-05462-9.

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.

A novel validated simple derivatization liquid chromatographic method with diode array detection for the simultaneous determination of mancozeb, azoxystrobin and difenoconazole in pesticide dosage form

A novel, rapid and simple reverse-phase high performance liquid chromatography (RP-HPLC) method for the simultaneous determination of three pesticides - mancozeb, azoxystrobin and difenoconazole by derivatization with ethyl iodide is presented. Analysis was performed on a C18 column (Agilent Eclipse plus, 150 mm × 4.6 mm; 5 μ) with the mobile phase consisting of acetonitrile + methanol (90 + 10 v/v) - water (0.1% v/v trifluoroacetic acid) (60 : 40, v/v) pumped isocratically at a flow rate of 1.0 mL min^-1 and detection wavelength of 205 nm and 272 nm. The factors affecting the derivatization reaction and separation conditions were carefully evaluated and optimized. The method was linear over the concentration range of 3.50 mg L^-1 to 31.48 mg L^-1 for mancozeb, 0.32 mg L^-1 to 2.85 mg L^-1 for azoxystrobin and 0.32 mg L^-1 to 2.89 mg L^-1 for difenoconazole. The new method was successfully applied for the analysis of mancozeb, azoxystrobin and difenoconazole in the pesticide formulation with range recoveries of 99.46% to 100.76%, 99.07% to 101.09% and 98.59% to 101.59%, respectively. The present method is suitable and favorable for the simultaneous separation and analysis of tertiary mixture analytes on account of its sensitivity, rapidity and cost-effectiveness. In addition, it could have excellent application prospects for the simultaneous determination of all three pesticides in other formulated products.

A simple derivatization RP-HPLC method for the simultaneous determination of zineb and hexaconazole in pesticide formulation using a PDA detector

A simple derivatization reverse-phase high performance liquid chromatographic method for the simultaneous analysis (separation and quantification) of zineb and hexaconazole has been optimized and validated. The method was carried out on an Agilent Eclipse plus C18 column (150 × 4.6 mm; 5 μm), with a mobile phase comprising acetonitrile + methanol (80 + 20 v/v): water (0.1% v/v trifluoroacetic acid) (60 : 40 v/v) at a flow rate of 1.0 mL minute^-1, and the quantification was achieved at 272 nm and 205 nm. The retention times of zineb and hexaconazole were found to be 6.4 min and 7.6 min, respectively. The performance of the method was validated according to the SANCO, CIPAC and ICH guidelines for specificity, selectivity, linearity, precision, accuracy, limit of detection, limit of quantification and robustness. The developed method was successfully applied for the estimation of zineb and hexaconazole in a pesticide dosage form.

Determination of Mancozeb, a Pesticide Used Worldwide in Agriculture: Comparison among GC, LC, and CE

Background:

The determination of mancozeb, a fungicide extensively used in agriculture, is a challenge, due to the nature of the compound, a manganese and zinc complex of ethylenebis dithiocarbamate and because of the general instability of the dithiocarbamates.

Methods:

Mancozeb was analyzed in a GC-EI-MS system after derivatization by CE-UV with detection at 280 nm and in LC-ESI-MS-MS in MRM mode.

Results:

A comparative study of the performance of three different techniques for the detection of mancozeb was explored, highlighting the advantages and drawbacks of them. The limits of detection and quantification of the techniques were determined; the repeatability was assessed, showing values of relative standard deviation. Gas chromatography, although very sensitive, was not reproducible enough due to fast degradation of the derivatization product, whereas capillary electrophoresis-UV showed problems in run-to-run reproducibility which had the worst limit of detection. LC coupled with tandem mass spectrometry was the most reliable and precise technique and was able to determine the main degradation product of Mancozeb, at the same time. The proposed LC procedure was verified by applying it to a commercial formulation, a fungicide of known concentration, and to Italian white grapes treated with the formulation sprayed during cultivation.

Conclusion:

Thanks to the simplified sample handling, the proposed method resulted to be simple, fast, green, economic, and suitable for residue analysis in grapes and other fruits. Finally, the method was compared with other similar investigations.

Lead ethyl dithiocarbamates: efficient single-source precursors to PbS nanocubes

Lead ethyl dithiocarbamates have been successfully used as single-source precursors for the deposition of PbS using spin coating followed by annealing at moderate temperatures. The thin films were characterized using a powder X-ray diffractometer and were found to be face-centred cubic with the (200) plane being the most preferred orientation. Scanning electron microscopy images showed the formation of well-defined cubes. Optical band gaps of PbS thin films were estimated using Tauc plots as 0.72, 0.73 and 0.77 eV at annealing temperatures of 250, 300 and 400°C. These band gaps were all blue shifted from the bulk value of 0.41 eV. Energy-dispersive X-ray analysis was used to determine the composition of the thin films which showed an approximately 1 : 1 Pb to S ratio.