Quantitative determination of capsaicin in liniments by microemulsion liquid chromatography

A technique for the quantitative determination of capsaicin in liniments by the microemulsion liquid chromatography method is proposed. Due to the absence of the homogenization, extraction and filtration stages, the procedure of sample pretreatment takes 5 minutes, which is much more rapid in comparison with the variants described in the literature (from 30 minutes to 12 hours). The full time of the analysis (including the procedure for sample pretreatment) is 20 minutes. The graduation curve is linear in the range from 0.02 to 240 mg/l. The limit of determination of capsaicin was 8 μg/I.     

Simultaneous determination of fat- and water-soluble vitamins by microemulsion electrokinetic chromatography

A new procedure was developed for the simultaneous determination of water- and fat-soluble vitamins by microemulsion electrokinetic chromatography. Using microemulsions based on sodium dodecyl sulfate, Brij 35, 1-butanol, and heptane, 10 vitamins were separated (4 water-soluble and 6 fat-soluble) within 35 min. The efficiency of the separation was 800000 theoretical plates (effective capillary length, 40 cm). To enhance the selectivity, 2-propanol was used as a hydrophobizing addition into the microemulsion. The procedure was used for analyzing a kaolin-based vitamin premix. The use of microemulsion as an agent for extracting vitamins from the support considerably simplifies the sample preparation.     

Conversion of low spin states in a monochelate complex of Fe(III) with an asymmetric tridentate azomethine ligand

An iron(III)-containing complex with the asymmetric tridentate azomethine ligand 4,4′-dodecyloxybenzoyloxybenzoyl-4-salicylidene-N′-ethyl-N-ethylenediamine with a PF ₆ ^? counterion is obtained. The presence of the complexing ion is confirmed by far IR Fourier spectra. The structure of the compounds is determined by matrix-assisted laser desorption/ionization with a time-of-flight mass analyzer (MALDI-ToF). The results of mass spectrometric studies are consistent with the elemental analysis data. It is found that the complexation of iron salt with an asymmetric tridentate ligand results in the formation of compounds of the composition 1:1 with octahedral packing of a metal ion in the complex. The electrochemical behavior of the compound in organic solvents is examined. The EPR study shows that iron(III) ions are in both low spin (LS) and high spin (HS) states in the complex. The LS and HS iron(III) centers are coupled into dimers in which a water molecule and the PF ₆ ^? counterion act as bridges. It is also found that for LS complexes in the lowtemperature phase (4.2–300 K), the (d _xz ,d _yz )⁴(d _xy )¹ electronic state is the ground state. It is revealed that the conversion of the sample into a high-temperature liquid crystalline (387–405 K) phase is accompanied by the conversion of the LS states of the Fe(III) ion: (d _xz ,d _yz )⁴(d _xy )¹ ? (d _xy )²(d _xz ,d _yz )³. The conversion of LS states is temperature reversible and is driven by the temperature. X-ray crystallographic data confirm that the compound obtained consists of dimer formed by a hydrogen (O-H...F) bond.