PubMed · 12196739
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
Kevin M Klauer. Life beyond MUDPILES.. https://pubmed.ncbi.nlm.nih.gov/12196739/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
A method for the quantitative determination of acetaminophen by measuring the kinetics of its oxidation by the enzyme tyrosinase in the presence of the nucleophilic agent 3-methyl-2-benzothiazolone hydrazone (Besthorn's hydrazone) is described. The hydrazone traps the o-quinone product of the catalytic activity, 4-acetamido-o-benzoquinone, thus increasing the level of the catecholic intermediate, 3'-hydroxyacetaminophen, in the pathway, as was shown by liquid chromatography. This reduces the time necessary for the steady state to be reached and increases the steady state oxidation rate, reaching activations of 124 times at an initial concentration of 3mM hydrazone. Despite being rapid and simple the method is thorough and provides a linear range of quantification of the drug from 10 nmol/ml to 1.4 micromol/ml. The assay can be performed in continuous or discontinuous form, meaning that it can be used with the immobilized enzyme for the design of specific biosensors.
The effects of some crystallisation conditions on the formation of orthorhombic paracetamol from ethanolic solution are examined when seeding technique is applied under fixed agitation (700 rpm) and harvesting time (30 min). Three equally spaced levels were used for initial concentration, C(I) (30 +/- 4% w/v), for seeding temperature, T(S) (7 +/- 7 degrees C) and for cooling temperature, T(C) (-10 +/- 10 degrees C). The influences on parameters of temperature change in the crystallisation solution were quantitatively determined as were influences on crystal yield (Y%), crystal size and shape, and orthorhombic content of the final crystalline product. Conditions for improvement of Y% under reproducible formation of orthorhombic form were elucidated. It was found that Y% increases remarkably by increasing C(I) but there is a corresponding decrease in the content of orthorhombic form. Increased content of monoclinic form is explained by nucleation under conditions of high C(I) (34% w/v), low seeding temperature (below 7 degrees C) and long seeding time (more than 14.7 min) in addition to transformation of grown orthorhombic seeds. However, reproducible formation of pure orthorhombic form is possible at medium C(I) (30% w/v) and optimal crystal yield (60.9% w/w) corresponds to -20 degrees C T(C) and 0 degrees C seeding temperature. Crystal size is affected by all the crystallisation conditions due to the alteration in the degree of supersaturation, and consequently, in the nucleation and growth processes. Aspect ratio is affected due to the presence of less elongated monoclinic crystals. The fullness ratio increases with the cooling temperature but decreases with the initial concentration, probably because of secondary nucleation on the crystal surfaces or erosion due to initiation of transformation.
The purpose of this study is to characterize the monoclinic crystals in tablets by using X-ray powder diffraction data and to evaluate the deformation feature of crystals during compression. The monoclinic crystals of acetaminophen and benzoic acid were used as the samples. The observed X-ray diffraction intensities were fitted to the analytic expression, and the fitting parameters, such as the lattice parameters, the peak-width parameters, the preferred orientation parameter and peak asymmetric parameter were optimized by a non-linear least-squares procedure. The Gauss and March distribution functions were used to correct the preferred orientation of crystallites in the tablet. The March function performed better in correcting the modification of diffraction intensity by preferred orientation of crystallites, suggesting that the crystallites in the tablets had fiber texture with axial orientation. Although a broadening of diffraction peaks was observed in acetaminophen tablets with an increase of compression pressure, little broadening was observed in the benzoic tablets. These results suggest that "acetaminophen is a material consolidating by fragmentation of crystalline particles and benzoic acid is a material consolidating by plastic deformation then occurred rearrangement of molecules during compression". A pattern-fitting procedure is the superior method for characterizing the crystalline drugs of monoclinic crystals in the tablets, as well as orthorhombic isoniazid and mannitol crystals reported in the previous paper.