The determination of the positions of double bonds after dimethyl disulfide (DMDS) addition is described for triunsaturated compounds (alkatrienes and an ester). Different DMDS derivatives were studied according to the numbers, n 1 and n 2 , of methylene groups separating the double bonds. When n 1 and n 2 are smaller than four, a bicyclic thioether is formed and a predictable fragmentation pathway is observed in each case after electron ionization, allowing the determination of the positions of the three double bonds and the molecular structure of the compounds.
A liquid chromatography-electrospray-mass spectrometry technique for the screening and determination of five non-depolarizing neuromuscular blocking agents (NDBAs), atracurium and its product of degradation/metabolite laudanosine, rocuronium, pancuronium, vecuronium, and mivacurium has been developed using ambenonium as the internal standard (I.S.). Samples were acidified upon reception by adding 20 micro L 0.5M H(2)SO(4) to 500 micro L of biofluid. Sample preparation consisted of simple blood purification and/or protein precipitation using 1 mL I.S. in acetonitrile. Chromatographic separation was carried out on an X-TERRA trade mark column along with a gradient of acetonitrile in 2mM ammonium formate (pH 3). Detection was carried out in the positive selected ion monitoring mode, targeting one quantitation ion and one confirmation ion per compound. The limit of quantitation was 2.5 micro g/L for mivacurium and laudanosine, 5 micro g/L for rocuronium and pancuronium and 10 micro g/L for atracurium and vecuronium in serum (i.e., in the range of, or less than, therapeutic levels). The technique was found to be linear between the respective LOQs and 2000 micro g/L, with correlation coefficients higher than 0.999 in all matrices. Intra- and interday precision and accuracy in serum fulfilled the international criteria. This method was employed for the investigation of a case of suicide by infusion of drugs. Laudanosine, the metabolite or degradation product of both atracurium and cisatracurium, and rocuronium were found in urine and whole blood, at supratherapeutic concentrations in the latter (rocuronium: 1.53 and 2.18 mg/L, laudanosine: 8.86 and 0.31 mg/L, respectively), and even therapeutic concentrations would have been lethal in the absence of respiratory assistance.
The determination of the positions of double bonds after dimethyl disulfide (DMDS) addition is presented for linear or branched di-unsaturated esters and a di-substituted y lactone. Different DMDS derivatives are studied according to the number, n, of methylene groups separating the double bonds. For n = 0, a mono derivative is obtained following treatment with DMDS; for n = 1 , 2 or 3, a cyclic thioether is synthesized. For R = 0, only one double bond is located after a classical cleavage. For n = 1, 2 and 3, a systematic fragmentation pathway is observed allowing the determination of the positions of the double bonds and the molecular structures of the compounds.Alkenes and unsaturated fatty acids are very important molecules in biogeochemistry. The positions of the double bonds are often dependent on their origin. The electron impact mass spectra of these underivatized compounds give no indication about these double-bond positions.Dimethyl disulfide (DMDS) adducts of monounsaturated compounds obtained by addition of DMDS in the presence of iodine (Scheme l), have previously been investigated. This method allows the determination of the double bond position in olefins, fatty acids and esters.'-6 The use of dimethyl disulfide to locate the double bonds in di-unsaturated compounds is effective with acetate^,^ natural long-chain alkadienes' and short-chain alkadienes.'Author for correspondenceThe reaction of DMDS with di-unsaturated compounds differs according to the number of methylene groups ( n ) which separates the double bonds. Thus, (i) for n = 1, two mono-derivatized compounds are formed by addition of DMDS; (ii) for n=2, a five-membered cyclic thioether is synthesized; and (iii) for n = 3, two compounds are obtained: a six-membered cyclic thioether and a monoderivatized compound.' From n = 4, four methylthio groups are fixed and classical cleavages are ~bserved.~.'
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