The polarographic properties of cephalothin, cephacetrile, cefamandole, cefamandole nafate and cefoperazone were investigated by using cathode-ray polarography (CRP) and differential-pulse polarography (DPP). The electroactive group present in the investigated cephalosporins is the R' leaving group in CH2R', which is located at the 3-position. The electrochemical methods developed were applied to cephalosporins in dosage forms and a comparison was made with the Ni(ll)hydroxylamine method. The relative standard deviations obtained for the electroanalytical methods varied between 0.28 and 0.95% and for the comparative method between 0.54 and 1.91%.
Britton-Robinson buffers (BRB), pH 4-9, provide for sufficient stability of brotizolam (1) and may be used as supporting electrolytes for its DC, polarography. The polarographic behaviour of 1 was investigated: The i-E curves are markedly influenced by adsorption processes and cleavage of the C-Br bond. In spite of these difficulties a precise electrochemical method for the determination of 1 could be developed. A BRB (pH 6.3) is best suited for the assay by DC, and DPP. The lower sensitivity limit is 1k6 mol -L-1 with DC, polarography and lCb7 mol . L-I with DPP. In the ana- Brotizolam (Lendormina) is a very effective new triazolothienodiazepine with a high affinity to the benzodiazepine receptors used as a sleep inducing hypnotic1). Elimination half-lives are in the range of 3-6 h in healthy young subjects. There are no residual effects the next morning with doses of up to 0.25 mg at night2). ++++) DAAD scholar 1984DAAD scholar -1986 detailed electrochemical investigation the stability with time of the DCt polarographic waves of 1 was followed in 10 % DMF solutions using O.1N-HCl, BRB of different pH and 0.1N-NaOH as supporting electrolytes. In 0.1N-HCl a reduction wave at -0.56 V in addition to the original wave of -0.46 V was observed, probably corresponding to the expected ketone formation due to hydrolysis of the -N=C(R)-double bond (5,6). On the TLC plates two spots were detected indicating the degradation of 1 in this solution. Between pH values 4 and 9 the shape and the height of the waves remained unchanged for 24 h. The time depending character of the DCt polarographic (i.e. sampled) waves was also observed in 0.1 N-NaOH solutions.
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