Rapid determination of acetaminophen in physiological fluids by liquid chromatography using SDS mobile phase and ED detection

Acetaminophen is determined in serum and urine samples by a rapid, sensitive, and precise chromatographic method without any pretreatment step in a C18 column using a pure micellar mobile phase of 0.02M sodium dodecyl sulfate at pH 7. Acetaminophen is eluted in less than 5 min with no interference of the protein band. The use of electrochemical and UV detection is compared. Linearities (r > 0.999), as well as intra- and interday precision, are studied in the validation of the method. Limits of detection (LOD) are also calculated to be 0.56, 0.83, and 0.74 ng/mL in micellar solution, serum, and urine using electrochemical detection. The developed micellar liquid chromatographic method is useful for the quantitation of acetaminophen in serum and urine. Recoveries in the biological matrices are in the 98-107% range and results are compared with those obtained using a reference method. Drug excretion (in urine) and serum distribution are studied in several healthy volunteers, and no interference from metabolites is found. The developed procedure can be applied in routine analyses, toxicology, and therapeutic monitoring.     

Mechanism of the oxidation of cycloheptanone by chloramine-T

The oxidation kinetics of cycloheptanone by chloramine-T in alkaline media has been investigated. A mechanism involving the formation of an intermediate by the interaction between the enolic anion of cycloheptanone and chloramine-T in a slow step followed by its interaction with another molecule of chloramine-T in a fast step leading to products has been proposed. The scheme satisfactorily accords with the observed stoichiometry, negligible influence of ionic strength and a positive dielectric effect. Various rate parameters have been computed and 1.2-cycloheptanedione identified as the end product.With 2 Figures     

31P and 1h NMR as probes of domain alignment in a rigid crystalline surfactant mesophase

A viscous reverse hexagonal surfactant mesophase containing bis(2-ethylhexyl) sodium sulfosuccinate (AOT) and alpha-phosphatidylcholine (lecithin), with comparable volume fractions of isooctane and water, was characterized by Fourier transform (31)P and (1)H NMR spectroscopy. Shear alignment was reflected through both (31)P NMR and (1)H NMR spectra. A complicated (31)P spectrum was observed as a result of superposition of chemical shifts according to the distribution of crystalline domains prior to shear. The initially disordered samples with polydomain structures become macroscopically aligned after Couette shear. (31)P NMR chemical shift anisotropy characteristics are used to elucidate orientation of the hexagonal phase. Interestingly, (1)H NMR spectra exhibit spectral changes upon shear alignment closely corresponding with that of (31)P NMR spectra. These observations complement the findings of mesophase alignment obtained using SANS and imply that (31)P and (1)H NMR spectroscopy can be used as probes to define microstructure and monitor orientation changes in this binary surfactant system. This is especially beneficial if these mesophases are used as templates for materials synthesis.     

Domino "[3+3]-cyclization-homo-Michael" reactions of 1,3-bissilyl enol ethers with 1,1-diacylcyclopropanes

The Lewis acid mediated domino "[3+3]-cyclization-homo-Michael" reaction of 1,3-bissilyl enol ethers with 1,1-diacylcyclopropanes allows an efficient one-pot synthesis of functionalized salicylates containing a halogenated side chain. A great variety of substitution patterns could be realized by variation of the starting materials and of the Lewis acid. The mechanism of the domino process was studied.     

Mixing examples in the class of piecewise monotone and continuous maps of the unit interval

A process (T, P) is said to have the “ ” property if there is a uniform, positive lowerbound δ on the separation between theT-P names of (almost) every pair of pointsx≠y. A finite group rotation with partition into distinct points provides a trivial example. Given any process having the property we show that there exists a Bernoulli shiftB so thatT×B is measurably isomorphic to the natural extension of a piecewise monotone, continuous, and expanding map of the unit interval. This construction is applied to produce interval maps which are ergodic but not weak-mixing, weak-mixing but not mixing, and mixing but not exact with respect to their unique absolutely continuous invariant measures, in contrast with the results known for piecewiseC ^1+∈ expansive interval maps. In obtaining these examples we identify a number of nontrivial classes of automorphismsT which admit processes having the property. Supported by NSERC grant OGP0046586 90.     

Effect of radiation dose on the thermal decomposition of sodium bromate

Influence of radiation dose in the range of 0.5–2.0 MGy of⁶⁰Co -rays on the isothermal decomposition of sodium bromate at 633.0 K shows that irradiation increases the initial gas evolution {ie37-1}, shortens the induction period (I), enhances the rate of reaction in the accelerating and decay stages. The data fit well the Prout-Tompkins relationship, indicating that nucleation occurs in a chain branching manner during the process. The fraction decomposed, , increases with increasing radiation dose.     

Determination of thiol groups with o-diacetoxy-iodobenzoate

o-Diacetoxyiodobenzoate is used for determining thiol groups by two procedures. In the first, thiols are titrated directly with the reagent at pH 6-8, with leuco-2,6-dichlorophenolindophenol and potassium iodide as indicator. In the second, thiols are treated at pH 7 with an excess of the reagent, the surplus being determined by reaction with excess of mercaptoacetic acid followed by back-titration of the latter with iodine. Both procedures yield results within 0.2% of the theoretical.