The simultaneous degradation of prochloraz and tebuconazole in water with monitoring their degradation products using liquid chromatography-tandem mass spectrometry.

Prochloraz and tebuconazole are well-known fungicides for broad applications, including medical, industrial, and agricultural. They are frequently used simultaneously which increases the probability of their co-existing in various water sources. In this study, the analysis of PCZ or TBZ in water was performed by a direct analysis using the liquid chromatography-tandem mass spectrometry technique (LC-MS/MS). The optimized method was fully validated according to the European guidelines, SANTE/11312/2021. The complete degradation of these fungicides (each of 2 mg/L) in their single presence in the water was accomplished just after 15 min using 4.2 mM persulfate at 50 °C, while a lower concentration of persulfate (1.4 mM) leads to a degradation of prochloraz and tebuconazole, in their single existence in water, at percentages of 97 % and 98 %, respectively, after 30 min at 50 °C. On the other hand, it takes a complete hour to degrade a mixture of prochloraz and tebuconazole at percentages of 99 % and 94 %, respectively, using 1.4 mM persulfate at 50 °C. Degradation products (DPds) of prochloraz and tebuconazole, either in their single or simultaneous existing in water, were also identified and monitored during the whole degradation process by LC-MS/MS using at least two mass transitions for each DPd at both positive and negative ionization modes. It was elucidated that the persulfate degradation of prochloraz was conducted by the cleavage of the imidazole ring and the subsequent formation of a trichlorophenol, while persulfate degradation of tebuconazole was mainly accomplished by the formation of a hydroxyl structure, cleavage of the tert-butyl chain, and the subsequent formation of a ketone structure. Furthermore, a new DPd of tebuconazole (m/z = 263 Da) with a diketone structure was identified and confirmed.

Improved analysis of folpet and captan in foods using liquid chromatography-triple quadrupole linear ion trap mass spectrometry: applying mass filtering, collision, and trapping conditions.

Accurate and highly sensitive analysis of folpet and captan was accomplished using liquid chromatography-triple quadrupole linear ion trap mass spectrometry (LC-QqQIT) with selective ion mode; mass filtering, collision, and trapping condition. Dimensional mass spectrometry (MS3) parameters were optimized for the residue detection of folpet and captan in six food commodities (apples, tomatoes, sweet pepper, wheat flour, sesame seeds, and fennel seeds). The sample preparation method was based on the known QuEChERS protocol, except a mixture of acetonitrile/acetone was used for the sample extraction from the sesame seeds. The robustness and reliability of the developed MS3 method were demonstrated by performing a full validation, according to SANTE/11312/2021, at 0.01-0.25 mg/kg. Recovery ranged from 83 to 118% with a relative standard deviation below 19% in all the tested commodities, and limits of quantifications (LOQs) were 0.01 mg/kg in apples and tomatoes; 0.03 mg/kg in sweet pepper; and 0.05 mg/kg in wheat flour, sesame seeds, and fennel seeds. Monitoring results showed that about 90% of apples contained captan residue, and in sweet pepper, concentrations of captan and folpet as high as 1.57 and 0.97 mg/kg were found, respectively. The novel developed MS3 method enabled more reliable identification of these commonly problematic fungicides at lower LOQs than previously reported methods.

Supercritical fluid chromatography coupled to tandem mass spectrometry for the analysis of pesticide residues in dried spices. Benefits and drawbacks.

This study describes the high sensitivity and the reduced ion suppression and matrix effect that can be achieved by supercritical fluid chromatography (SFC) in the analysis of dried spices as complex matrices. Samples selected for the evaluation were cayenne and black pepper, which are representative of complex dried spices. To carry out the evaluation of this technique, blank samples were fortified with a solution containing 162 pesticides at two concentration levels (50 and 200 µg kg-1). During the modified QuEChERS method, EMR sorbent was used as dispersive SPE in the clean-up step. The samples were analysed by supercritical fluid chromatography coupled to tandem mass spectrometry. The validation parameters studied were recovery, inter and intraday precision, linearity and matrix effect. Recoveries for the majority of compounds were in the 70-120% range recommended by DG-SANTE guidelines and showed a precision lower than 20% in terms of RSD. Matrix effect was low (0-20% signal suppression) for 132 pesticides in cayenne and 91 in black pepper. The method was used to analyse 47 real samples of spices from different countries. A high number of these samples presented one or more pesticides (81%). Some of these detected pesticides are not approved in the European Union and, in many cases, the positive findings exposed concentrations that exceed the EU MRLs.

Development of an efficient method for multi residue analysis of 160 pesticides in herbal plant by ethyl acetate hexane mixture with direct injection to GC-MS/MS.

A simple and efficient multi residue method was developed, for the analysis of 160 pesticides by GC-MS/MS in herbal plants. The developed method employs pesticide residue extraction by EtAC/ n. hexane (6:4) with a cleanup step using florisil/ PSA mixture. The optimized conditions have resulted in lower co-extracted matrix components than those extracted using EtAC or MeCN (QuEChERS method), according to FTIR and full scan GC/MS analyses. In addition, the developed method (EtAC/ Hexane) eliminates the evaporation step that is usually performed when using MeCN as an extraction solvent prior to the GC-MS/MS injection. The developed method was fully validated on chamomile, based on SANTE/11945/2015 guidelines. Where, intraday recoveries were estimated at three concentration levels of 10, 50 and 250µgkg-1. However, interday recoveries have also been carried out, at 250µgkg-1. In addition, intraday recoveries were estimated for two other herbal plants (thyme and marjoram), at 250µgkg-1. Three point calibration mixtures were prepared in ethyl acetate solvent and in the blank extracts of chamomile, thyme, and marjoram, in order to check the linearity and matrix effect. The average recoveries for most of the studied pesticides ranged from 70% to 100% at 50 and 250µgkg-1 with relative standard deviations below 20%. The validated method was successfully applied for determination of pesticide residues in 20 herb samples, collected from the Egyptian market.