Determination of vitamin A in milk and flour consumed by one- to four-year-old children in Côte d'Ivoire.

As part of a United Nations Children's Found (UNICEF) study, an analytical method is proposed for routine analysis of vitamin A in milk and flour consumed by 1- to 4-year-old children in Côte d'Ivoire. The method involves liquid-liquid extraction of sample followed by reversed-phase liquid chromatography (LC). The method has been validated and used to analyze various samples collected at different locations and stored under unfavorable conditions. Average vitamin A content was 575 micrograms/100 g for milk powder and 1350 micrograms/100 g for millet flour. Lower contents were found in corn flour (40-240 micrograms/100 g), and no vitamin A could be detected in rice flour.

Column liquid chromatography determination of vitamins A and E in powdered milk and local flour: a validation procedure.

A high-performance liquid chromatography method was developed for the simultaneous routine determination of vitamins A and E in powdered milk and flour made from local plants and purchased from open markets in the Ivory Coast. The method involves saponification followed by extraction with a mixture of organic solvents. The vitamins were resolved by reversed-phase HPLC and detection at a single wavelength. The main tests of method validation were applied to the procedure. The results show the reliability of the analytical method for the intended application.

Individual degradation rate constants for cefotaxime, deacetylation profile.

The individual degradation rate constants for cefotaxime in aqueous solution were calculated within a pH range of 1.6-10.0 at 37 degrees C from high performance liquid chromatography data. This allowed the general degradation profile of cefotaxime to be decomposed into a degradation profile attributed to the opening of the beta-lactam nucleus and a degradation profile attributed to the deacetylation. From the calculations of the individual rate constants, the activity of degraded cefotaxime solutions could be predicted. In the pH range of injectable solutions of cefotaxime 5-7, roughly equivalent amounts of inactive beta-lactam cleavage products and deacetylated compound which has a different spectrum of antibacterial activity are formed.

Determination of aminoglycosides in pharmaceutical formulations--I. Thin-layer chromatography.

A simple, fast and reliable procedure for the determination of seven major aminoglycosides in commercial formulations (injections, capsules, eye drops, solutions and ointments) is presented. The aminoglycosides are separated on silica gel plates then located with ninhydrin and analysed in situ using a chromatogram spectrophotometer. Linearity tests, repeatability (relative standard deviation congruent to 3.5%) detection limits (60-200 ng) were satisfactory for all the compounds. Recovery data in pharmaceutical formulations (expressed as the percentage of the label claim) from thin-layer chromatography (TLC) and microbiological assays did not give any significant difference (P = 0.05); this result shows that TLC is a reliable method for the determination of aminoglycosides as the drug substance and in pharmaceutical formulations.

Determination of aminoglycosides in pharmaceutical formulations--II. High-performance liquid chromatography.

A post-column derivatization procedure using OPA and fluorescence detection has been used for the determination of seven aminoglycosides (dibekacin, framycetin, kanamycin, netilmicin, sisomicin, tobramycin and gentamicin) in commercial pharmaceutical formulations. The linearity, precision and detection limits were satisfactory. Recoveries from eye drops, ointments, injections and capsules were comparable (P = 0.05) to those obtained with TLC or microbiological assays. A ruggedness test showed that the method was not sensitive to minor variations in the mobile phase composition, post-column derivatization system or detection wavelength.

Photodegradation paths of cefotaxime.

The degradation kinetics of cefotaxime sodium salt in aqueous solution, under UV light at 254 nm, was investigated by HPLC and antibiotic activity. This degradation is the result of two competitive processes, an isomerization and a photolysis. This study is mostly about the isomerization step. The measured quantum yields for the cefotaxime to its anti-isomer and anti-isomer to cefotaxime isomerizations are, respectively, 0.10 and 0.12. A photostationary state characterized by an anti:syn ratio of 1.2 is obtained after 30 min of irradiation. The competitive photolysis, which actually consists of at least two processes (one on the delta 3-cephem ring and the second on the methoxyimino group), leads to an intense yellowing of the solution corresponding to the destruction of the molecule. The comparative evolution of the absorption spectra, under irradiation at 254 nm, of cefotaxime, thiazoximic acid, and 7-aminocephalosporanic acid shows that it is the delta 3-cephem ring photolysis which gives the yellow color. The major conclusion of this work is to call attention to the photoisomerization step which leads efficiently to the inactive anti-isomer, without giving any visible notice of degradation. Such a process is to be expected in all antibiotics containing an alkoxyimino linkage on the C-7 substitution.

Autoxidation and hydrolysis kinetics of the sodium salt of phenylbutazone in aqueous solution.

The present investigation offers experimental results concerning the degradation kinetics of the sodium salt of phenylbutazone based on a reliable HPLC procedure. The method allows the simultaneous determination of the parent compound and its main decomposition products. The degradation kinetics at 37 degrees C were compared at pH 7.9 and 10.0 and under oxygen and nitrogen atmospheres. Parallel tests were carried out in the dark and under photolytic conditions for the aforementioned conditions. The influence of traces of iron and a chelating agent of iron on the degradation was studied. At pH 7.9 and pH 10.0 the main degradation products are 3-hydroxy-2-oxohexanoic acid 1,2-diphenylhydrazide and 3-carboxy-2-oxohexanoic acid 1,2-diphenylhydrazide. Azobenzene is formed only at pH 10.0. At pH 7.9, in the dark, the degradation proceeds with a lag phase. In contrast, no lag phase is observed under photolytic conditions. The process of autoxidation and hydrolysis is catalyzed by traces of iron both in the dark and under irradiation conditions. An unexpected increase in the degradation is observed in the presence of iron(III) and EDTA in aerobic conditions and under irradiation.

Stability-indicating assay for phenylbutazone: high-performance liquid chromatographic determination of hydrazobenzene and azobenzene in degraded aqueous phenylbutazone solutions.

A high-performance liquid chromatographic method was developed for the simultaneous determination of azobenzene, hydrazobenzene, and four other decomposition products in phenylbutazone injectable formulations. Separation was achieved on a C18 column, with 0.1 M Tris-citrate buffer (pH 5.25) and acetonitrile (52:48), at a flow rate of 2 mL/min and a detection wavelength of 237 nm. Diphenylamine was used as an internal standard. The limit of quantitation is 0.5% (with respect to phenylbutazone) of each degraded product. The detectability is 2.4 X 10(-3) micrograms for azobenzene and 1.5 X 10(-3) micrograms for hydrazobenzene. The limit of quantitation may be lowered to 0.1% (with respect to phenylbutazone) for azobenzene and hydrazobenzene in the presence of the two major decomposition products, which have been determined in commercially available injectable formulations. A higher sensitivity was obtained for azobenzene using the mobile phase 0.1 M Tris-citrate buffer (pH = 5.25) and acetonitrile (40:60) with detection at 314 nm. Under these conditions, 0.025% (with respect to phenylbutazone) of azobenzene is quantitated.

Quality control of phenylbutazone II: Analysis of phenylbutazone and its decomposition products in drugs by high-pressure liquid chromatography.

A rapid, sensitive, accurate, and reproducible procedure for the simultaneous separation and determination of phenylbutazone and three major degradation products is proposed using reversed-phase high-pressure liquid chromatography and UV detection. The method is approximately 20 times more sensitive than TLC and allows an accurate determination of degradation products without decomposition during the analysis.

Quality control of phenylbutazone I: Analysis of phenylbutazone and decomposition products in drugs by TLC.

A modified TLC procedure for the analysis of phenylbutazone and its degradates on silica plates is reported. This method avoids phenylbutazone degradation in situ by chelating the iron of the silica plate, which allows rapid characterization with a fluorescence indicator. A selective and sensitive assay of phenylbutazone (0.025 microgram), using a chromatographic spectrophotometer, was performed on silica plates without a fluorescence indicator. Quantitative analysis of an injectable solution is outlined.

Thin layer chromatography reflectometric determination of benzoic and sorbic acids in fruit beverages.

A procedure is proposed for the quantitative determination of both benzoic and sorbic acids in fruit beverages. This method is carried out by direct ultraviolet spectrophotometric measurements in silica chromatoplates after development with chloroform-methanol-water (65 + 35 + 7) and makes use of an internal standard. Applied to samples spiked with benzoic and sorbic acids, this technique gives accurate and reliable results with good recoveries. The sensitivity (about 1 ppm) is particularly convenient for trace level determination.

Quantitative determination of thiourea in citrus fruits.

A quantitative method for thiourea determination in orange peels is proposed, with direct reflectance spectrometric measurements on chromatoplates. Thiourea is separated on a silica gel plate with methanol-chloroform (10 + 90), and the spots are characterized with 2,6-dichloroquinone chloroimide; this colorimetric reaction is unstable, so thiourea is quantitated on the chromatogram by direct ultraviolet reflectance spectrometric measurements at 240 nm. Comparison between this method and the AOAC colorimetric method shows interferences and higher results in the colorimetric assay. By slightly modifying the extraction technique, such as purifying the extract on an alumina column, it is possible to decrease these interferences and to avoid erroneous results with the AOAC colorimetric method. For both methods, colorimetry in solution and reflectometry on chromatoplates, applied after the proposed extraction technique, the sensitivity is about 1 ppm and the reliabilities are similar.