Stir membrane liquid phase microextraction of tetracyclines using switchable hydrophilicity solvents followed by high-performance liquid chromatography.

A novel approach for stir membrane liquid phase microextraction of tetracyclines from biological fluids was developed. The microextraction procedure assumed in situ formation of microdroplets of a hydrophobic medium-chain fatty acid (extraction solvent) from homogeneous sample solution containing water-soluble medium-chain fatty acid salt by acidification and simultaneous analytes extraction and organic phase separation into pores of stir membrane disk. Obtained large surface area between the extraction solvent and aqueous phase and high porosity of the membrane provided fast extraction and phase separation (extraction time - 5 min) and reducing extraction solvent volume to the order of several µL.

Crystal structure of a 2:1 co-crystal of meloxicam with acetyl-endi-carb-oxy-lic acid.

The pharmaceutical 2:1 co-crystal of meloxicam [MXM; systematic name: 4-hy-droxy-2-methyl--(5-methyl-thia-zol-2-yl)-2-1,2-benzo-thia-zine-3-carboxamide 1,1-dioxide] with acetyl-enedi-carb-oxy-lic acid (ACA; systematic name: but-2-ynedioic acid), crystallizes with one MXM mol-ecule and half an ACA mol-ecule in the asymmetric unit, CHNOS·0.5CHO. The mid-point of the triple bond of ACA is located on an inversion centre.