No abstract

Alkyl isothiocyanates were proposed for the determination of 1,1 dimethylhydrazine (DMH) in the form of 4 alkyl 1,1 dimethylthiosemicarbazides by gas chromatography coupled with mass spectrometry (GC MS). 4 Alkyl 1,1 dimethylthiosemicarbazides are selectively formed under mild conditions in the absence of catalysts. During the chromatography, these thiosemi carbazides are efficiently resolved from excess of alkyl isothiocyanates. A possibility of identifi cation of DMH derivatives on the basis of the chromatographic retention parameters and fragmentation data under electron ionization conditions was demonstrated.

No abstract

Pyridine derivatives R 0380Alkyl 2-Amino-5,6-dialkyl-3-cyanopyridine-4-carboxylates (I) in Reactions with Electrophilic Reagents. -(VASIL'EV, A. N.; LYSHCHIKOV, A. N.; NASAKIN, O. E.; PARAMONOV, S. A.; KAYUKOV, Y. S.; Russ. J. Org. Chem. 43 (2007) 10, 1537-1544; Chuvash Ul'yanov State Univ., Cheboksary 428015, Russia; Eng.) -R. Langenstrassen 15-141

A specific, sensitive, rapid and reproducible method for the determination of flomoxef in human plasma using high-performance liquid chromatography-tandem mass spectrometry was developed and validated. Flomoxef was detected using an electrospay ionization method operated in negative-ion mode. Chromatographic separation was performed in gradient elution mode on a Luna® C18(2) column (3 μM, 20 × 4.0 mm) at a flow rate of 1 mL/min and runtime 3.5 min. The mobile phase consisted of acetonitrile and water containing 0.1% formic acid as additive. Extraction of flomoxef from plasma and precipitation of plasma proteins was performed with acetonitrile with an absolute recovery of 86.4 ± 1.6%. The calibration curve was linear with a correlation coefficient of 0.999 over the concentration range 10-5000 ng/mL and the lower limit of quantification was 10 ng/mL. The intra- and inter-day precisions were <11.8%, while the accuracy ranged from 99.6 to 109.0%. A stability study of flomoxef revealed that it could be successfully analyzed at 4 ºС over 24 h, but it was unstable in solutions at room temperature during short-term storage (4 h) and several freeze-thaw cycles.