Characterization of photoproducts and global ecotoxicity of chlorphenesin: A preservative used in skin care products.

Photolysis experiments of chlorphenesin, used as a preservative in cosmetic products, were performed in aqueous solution and on a cream used in cosmetics. Three by-products resulting from the direct UV-visible photodegradation of chlorphenesin were characterized by chromatography (gas and liquid) coupled with tandem mass spectrometry (GC-MS/MS and LC-HR MS/MS) and found in both solutions. In vitro tests on Vibrio fischeri bacteria showed that the overall ecotoxicity of chlorphenesin increased with increasing irradiation time in both samples.

Photodegradation of cyprodinil under UV-visible irradiation - chemical and toxicological approaches.

Rationale: Cyprodinil is a fungicide active on grapes, strawberries, tomatoes, and many other fruits. Under UV-visible irradiation, it undergoes photodegradation through various processes to form transformation products (TPs) whose structures and potential toxicities are unknown. The structures of the TPs were elucidated by comparing the photodegradation of cyprodinil and cyprodinil-D5 .

Structural elucidation of metolachlor photoproducts by liquid chromatography/high-resolution tandem mass spectrometry.

Rationale: Metolachlor is one of the most intensively used chloroacetanilide herbicides in agriculture. It has been detected in water; consequently, under UV-visible irradiation, it can be transformed in degradation products (TPs). The structures of TPs were elucidated by liquid chromatography/high-resolution tandem mass spectrometry (LC/HR-MS/MS).

Isomerization of fenbuconazole under UV-visible irradiation - chemical and toxicological approaches.

Rationale: Fenbuconazole is a fungicide commonly used for the protection of vineyards, vegetables and grain crops. Under UV-visible irradiation, it undergoes isomerization through various cyclization processes. Isomeric structures were elucidated by liquid chromatography/high-resolution multiple-stage mass spectrometry (LC/HR-MS(n) ) coupling.

Using mass spectrometry to highlight structures of degradation compounds obtained by photolysis of chloroacetamides: case of acetochlor.

The photooxidation of acetochlor (a pesticide belonging to the acetamides group) using a polychromatic UV irradiation in ultrapure water was studied. This study reports the efficiency of mass spectrometry for the characterization of photodegradation products of acetochlor. Decompositions of protonated ions MH+are proposed in electrospray (ESI) mode for LC–MS, while electron ionization (EI) and chemical ionization modes (CI) are used for GC–MS.

Ultraviolet degradation of procymidone--structural characterization by gas chromatography coupled with mass spectrometry and potential toxicity of photoproducts using in silico tests.

Rationale: Procymidone is a dicarboximide fungicide mainly used for vineyard protection but also for different crops. The structural elucidation of by-products arising from the UV-visible photodegradation of procymidone has been investigated by gas chromatography coupled with mass spectrometry. The potential toxicities of photoproducts were estimated by in silico tests.

Characterization of the photodegradation products of metolachlor: structural elucidation, potential toxicity and persistence.

Aqueous solutions of metolachlor and metolachlor-d(6) were photolyzed with UV-visible radiations. The structures of 15 by-products of metolachlor were determined through gas chromatography-mass spectrometry analyses using electron and chemical ionization combined with multistage mass spectrometry. The photolysis by-products of metolachlor resulted mainly from dehalogenation and hydroxylation, in some cases accompanied by cyclization.

GC-MS(n) and LC-MS/MS couplings for the identification of degradation products resulting from the ozonation treatment of Acetochlor.

The degradation of the chloracetamide herbicide acetochlor has been studied under simulated ozonation treatment plant conditions. The degradation of acetochlor included the formation of several degradation products that were identified using GC/ion-trap mass spectrometry with EI and CI and HPLC/electrospray-QqTOF mass spectrometry. Thirteen ozonation products of acetochlor have been identified.

Estrone direct photolysis: by-product identification using LC-Q-TOF.

The identification of degradation products generated upon photolysis of estrone (E1), a natural estrogenic hormone, under simulated UV irradiation conditions was addressed by the use of LC-Q-TOF mass spectrometry. The structures of the main degradation products were elucidated, demonstrating how the use of model molecules 5,6,7,8-tetrahydro-2-naphtol (THN), 2-methylcyclopentanone (MCP), labeled molecule estrone D(4) (E1-D(4)), the investigation of the fragmentation pathways of the parent E1, the concurrent use of CID and exact mass measurements permit the characterization of structural modifications induced by photodegradation processes. In the present study, we identified nine major by-products of which seven photoproducts correspond to E1H(+) modified in positions other than the C-2, C-4 and C-16 of E1.

Molecular criteria for discriminating museum Asian lacquerware from different vegetal origins by pyrolysis gas chromatography/mass spectrometry.

This paper focuses on the identification of several chemical markers of vegetal species of Oriental lacquers with the aim at providing a methodology consistent with sampling restrictions necessarily applied in the field of cultural heritage. The method proposed is based on rapid and easy single step thermally assisted hydrolysis-methylation (THM) pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) analysis that can be carried out with a minimum amount of matter (typically 10 μg for a sample collected on a museum or an archaeological object). The main contribution of this study is to provide multiple molecular criteria for discriminating the three Asian species used for making lacquers, namely Rhus verniciflua Stokes, Rhus succedanea and Melanorrhoea usitata.

Investigation of the unusual behavior of metolachlor under chemical ionization in a hybrid 3D ion trap mass spectrometer.

This article describes the strange behavior of the widely used herbicide metolachlor under chemical ionization conditions in a hybrid source ion trap mass spectrometer in gas chromatography/mass spectrometry (GC/MS) coupling. With the use of ammonia as the reagent gas, metolachlor provides a chlorinated ion at m/z 295/297, almost as abundant as the protonated molecule at m/z 284/286, which cannot be isolated to perform tandem mass spectrometry (MS(n)) experiments. Curiously, this ion at m/z = M + 12 is not observed for the herbicides acetochlor and alachlor, which present very similar chemical structures.

Elucidation of the dissociation pathways of electro-ionized estrone.

With the future aim of using gas chromatography coupled with mass spectrometry to characterize the transformation products of estrone submitted to UV-photolysis or to waste water treatment plants, an interpretation of the electron impact mass spectrum of estrone is presented. Fragmentation mechanisms are proposed on the basis of high-resolution measurements performed with a magnetic sector analyzer. Multiple-stage mass spectrometry experiments were carried out using an ion trap mass spectrometer.