Simultaneous monitoring and dietary risk assessment of 386 pesticides in market samples of black tea.

Black tea samples (390) collected from local markets situated in different locations of India were monitored for the residues of 386 pesticides using QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) based extraction and analysis by gas and liquid chromatography tandem mass spectrometry (GC-MS/MS and LC-MS/MS). Residues of seventeen pesticides were detected, of which propargite, cypermethrin, and novaluron showed the highest % positive detections. A comparison of the concentrations of the detected pesticide residues with the available national and international maximum residue limits (MRLs) showed that seven samples exceeded the Indian MRLs while no sample was found to exceed the CODEX MRLs.

Light-induced dissolution and concomitant crystallization of a Keggin-type polyoxometalate mimicking a naturally occurring phenomenon.

A suspension of a yellow polycrystalline compound [PPh][PMoO] in -methylformanilide (NMF) (in which it is not soluble), on irradiation with sunlight, initiates dissolution its reduction followed by its crystallization leading to the isolation of single crystals of compound [PPh][PMoMoO]·3CH(CH)NCHO (1). Compounds [PPh][PMoO]·1.75 CH(CH)NCHO (2) and [PPh][PMoO]·2CH(CH)NCHO (3), each containing an oxidized Keggin anion, are obtained at two different temperatures when the corresponding mother liquor is kept in the dark.

Solvent mediated reversible solid state photochromism of {MoFe} Keplerate.

When the yellow rhombohedral crystals of Keplerate [Mo72Fe30O252(CH3COO)12{Mo2O7(H2O)}2{H2Mo2O8(H2O)}(H2O)91]·150H2O (1), on wetting with N,N-dimethylformamide (DMF), are irradiated with sunlight, a remarkable reversible solid state photochromic behaviour is achieved with the formation of green coloured crystals (1red). The reduction of the {MoVI} centres to {MoV} is responsible for the observed colour change from yellow to dark green. Importantly, compound 1 can be activated towards photochromism only in the presence of the DMF solvent.

A Reversible Redox Reaction in a Keggin Polyoxometalate Crystal Driven by Visible Light: A Programmable Solid-State Photochromic Switch.

The colourless crystals of (PPh ) [PW O ]⋅3 C H NO (1) are converted to the dark blue crystals of {(PPh ) [PW O ]⋅3C H NO} {(PPh ) (C H NO) [PW W O ] ⋅2C H NO)} (2) upon irradiation with visible light in an interesting single crystal to single crystal transformation. This photochromic conversion is accompanied by the reduction of concerned Keggin anion from {PW } to {PW W }. This redox conversion is characterized by various spectroscopic techniques including single crystal X-ray diffraction studies.