Keiichiro Hozumi

Determination of dissociation constants of sparingly soluble phenothiazine derivatives by second-derivative spectrophotometry

The dissociation constants (pKa) for sparingly soluble phenothiazines (promazine, chlorpromazine, trifluoropromazine) in water were measured by second-derivative spectrophotometry. The intense background signals in the absorption spectra due to the turbidity caused by the precipitation of insoluble free base of the phenothiazine derivatives were eliminated in the second-derivative spectra, and the solubilities of the phenothiazine derivatives could be easily determined from the peak-to-trough lengths (D values) of the second-derivative signals. The pKa values were calculated from the pH dependence of the D values. The pKa values obtained agreed well with reported values and the standard deviations for 6–10 determinations were ⩽ 0.02. The solubilities of the free bases of the phenothiazines were also determined.

Effect of the degree of polynomials in the Savitzky—Golay method for calculation of second-derivative spectra

Abstract The second-derivative spectra of absorption curves simulated by a Gaussian function were obtained by using Savitzky—Golay cubic (CPC) and quintic polynomial convolutions (QPC), based on 17 points assumed to be at 0.25-nm intervals. For data obtained directly from the simulated curves (real-type data), the second derivatives agreed with the true values if the widths at half height of the peaks were > 15 nm for CPC and 5 nm for QPC. But when integer values obtained from the real-type data were used to simulate a 12-bit A/D conversion, considerable noise appeared on the second-derivative spectra of peaks wider than the above values, obtained by both CPC and QPC. This occurred because the rounding errors introduced by the A/D conversion formed small shoulders on the digitally reproduced absorption curves, which were enhanced by the differentiation to generate noise. The noise was more intense in QPC than in CPC, thus CPC is preferable for peaks that are not very narrow.

Determination of isoniazid in tablets by second-derivative ultraviolet spectrophotometry of scraped-spot solutions from thin-layer chromatography

Abstract Isoniazid in solutions of tablets was separated by thin-layer chromatography (TLC). The portion of the precoated plate carrying the isoniazid spot was cut out and the coating was scraped off into water. The isoniazid was quantified in the solution, without separation of suspended adsorbent, by second-derivative spectrophotometry, which eliminated the background in the zero-order spectra. Relative standard deviations (n = 5) were

Preparation of immobilized glucose oxidase membrane by the plasma polymerization technique

Abstract Glucose oxidase was immobilized on a Millipore (MP) filter by coating with plasma-polymerized propargyl alcohol. The resulting immobilized enzyme membrane was used as a glucose sensor. The properties as a glucose electrode system were evaluated by amperometric response with either the steady-state method or the reaction rate method. The response was proportional to concentrations of the glucose solution up to 2 m M and the sensitivity was dependent on the amount of GOD impregnated into the MP filter.

Effect of savitzky—golay smoothing on second-derivative spectra

Abstract The rounding error arising from analog/digital conversion (12-bit) of a spectrum introduces small shoulders on the zero-order spectrum, which are enhanced in the second-derivative spectrum. To reduce this noise, Savitzky-Golay smoothing of the zero-order spectrum was examined by simulation. This smoothing procedure brings the second-derivative spectrum closer to the true spectrum. The effects of smoothing on the ultraviolet spectrum of salicylic acid in ethanolic solution are reported.