A new method for the determination of clomazone, fipronil, tebuconazole, propiconazole, and azoxystrobin in samples of rice paddy soil is presented. The extraction of the pesticides from soil samples was performed by using a modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) method. Some extraction conditions such as salt addition, sample acidification, use of buffer, and cleanup step were evaluated. The optimized method dealt with a single extraction of the compounds under study with acidified acetonitrile, followed by the addition of MgSO(4) and NaCl prior to the final determination by liquid chromatography-atmospheric chemical pressure ionization-tandem mass spectrometry. Validation studies were carried out in soil samples. Recoveries of the spiked samples ranged between 70.3 and 120% with relative standard deviation lower than 18.2%. The limits of quantification were between 10 and 50 μg kg(-1). The method was applied to the analysis of real samples of soils where rice is cultivated.

In this work, two analytical liquid chromatography methods were developed and compared for the characterization of aqueous phases from pyrolysis of lignocellulosic biomasses. NanoLC electron ionization-mass spectrometry (EI-MS) represents a novel and useful tool for both separation and identification of semi/nonvolatile and thermolabile molecules. The use of nanoscale flow rates, the highly reproducibility, and high detailed information on EI spectra are the principal advantages of this technique. On the other hand, comprehensive 2D-LC, providing a two-dimensional separation, increases the overall peak capacity lowering the occurrence of peak coelutions. Despite the use of reversed phase modes in both dimensions, a satisfactory degree of orthogonality was achieved by the employment of a smart design of gradient elution strategies in the second dimension in combination with photodiode array detection (PDA) and atmospheric pressure chemical ionization-mass spectrometry (APCI-MS). Because of the absence of the preliminary extraction procedure, the fingerprint obtained for these samples results is independent of the extraction yield or contamination contrary to the gas chromatography-mass spectrometry (GC-MS) approach where a liquid-liquid extraction of the water phase is necessary. The main classes of identified compounds were phenols, ketones, furans, and alcohols. The synergistic information on the two powerful analytical approaches, e.g., NanoLC EI-MS and LC × LC, in the identification of such complex samples has never been investigated and fully benefit on the one hand from the superior degree of mass spectral information from EI-MS and on the other hand from enhanced LC × LC compound separation.

Nowadays, bee products are being produced in an environment polluted by different sources of contamination, such as pesticides, which can be transported by honey bees to the hive and incorporated into honey. In addition, the increasing consumption of honey has demanded efficient quality control for this product. In this study, the determination of the pesticides fipronil, imidacloprid, thiamethoxam, dimethoate, carbendazin, tebuconazole, amitraz, τ-fluvalinate and 5-hydroxymethylfurfural (HMF) which are used as indicators of honey quality, was carried out simultaneously. For the sample preparation, the optimized QuEChERS method was used and the determinations were done by LC-APCI-MS/MS. The LOQs of the method ranged between 0.005 and 1.0 mg kg(-1). For the recovery calculations and method evaluation a working curve was drawn. All the analytical curves showed r values higher than 0.99. The recoveries ranged between 70% and 112%, with RSD lower than 20% for all compounds. The matrix effect was evaluated, and most of the compounds showed signal enrichment. The applicability of the method for honey from different flowers was verified, and the method showed robustness and recoveries in the range 70-120% established for all compounds in samples belonging to different blossoms. HMF was detected in all samples, with concentrations ranging between 4.6 and 51.7 mg kg(-1); it was below the maximum concentration allowed by the legislation.

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