Feasibility study concerning the use of expert systems for the development of procedures in pharmaceutical analysis.

The feasibility of using expert systems for the development of analytical procedures is investigated. A system for the computer generation of procedures to determine active drug substances in commercial formulations is proposed. It is shown that in nearly 85% of the cases investigated the present system immediately yields a correct procedure or conclusion. It is concluded that selecting methods and developing procedures with the use of expert systems is difficult but feasible.

Extraction of organic acids by ion-pair formation with tri-n-octylamine. Part 7. Comparison of methods for extraction of synthetic dyes from yogurt.

Synthetic dyes were extracted from yogurt by different methods, but all methods had in common a liberation of dyes from the food followed by ion-pair formation with tri-n-octylamine. Extraction with pH 5.5 phosphate buffer gave high recoveries for 5 of the 7 dyes investigated and was relatively fast. Precipitation of proteins followed by polyamide adsorption and desorption gave high yields for all the dyes but was tedious and long.

Extraction of organic acids by ion-pair formation with tri-n-octylamine. Part 6. Determination of sorbic acid, benzoic acid, and saccharin in yogurt.

The sorbate content of commercial yogurt samples is determined by reverse phase liquid chromatography following ion-pair extraction with tri-n-octylamine. Mean recoveries (70-88%), precision (1.1-3.3% RSD), and detection limit of the method are presented for sorbic acid, benzoic acid, and saccharin.

Extraction of organic acids by ion-pair extraction with tri-n-octylamine - VIII. Identification of synthetic dyes in pharmaceutical preparations.

Synthetic dyes were extracted from syrups, oral suspensions, tablets, gelatin capsules, suppositories and granules by ion-pair formation with tri-n-octylamine (TnOA) and back-extracted with perchlorate ions. Identification was performed by TLC on cellulose layers and by reversed phase ion-pair HPLC.

Extraction of organic acids by ion-pair formation with tri-n-octylamine. Part V. Simultaneous determination of synthetic dyes, benzoic acid, sorbic acid, and saccharin in soft drinks and lemonade syrups.

Synthetic dyes, benzoic acid, sorbic acid, and saccharin are extracted simultaneously from soft drinks with 0.01M tri-n-octylamine at pH = 5.5 and are back-extracted to an aqueous phase with 0.1M sodium perchlorate. The perchlorate solution is injected directly into the reverse phase liquid chromatographic system which permits the separation of all the substances investigated. Forty-six commercial samples of soft drinks and 11 lemonade syrups were analyzed. All samples conformed to the legal prescriptions.

High performance liquid chromatographic and colorimetric determination of synthetic dyes in gelatin-containing sweets, following polyamide adsorption and ion-pair extraction with tri-n-octylamine.

Dyes are determined in gelatin-containing sweets. The gelatin must be eliminated first because it interferes with the normal ion-pair extraction of dyes with tri-n-octylamine to chloroform. Techniques such as precipitation of gelatin with organic solvents, and acid and enzymatic digestion of gelatin are shown to be unsuccessful because the remaining gelatin still influences the extraction scheme. Positive results are obtained when dyes are adsorbed on polyamide, gelatin is washed away, and dyes are desorbed with a methanol-ammonia mixture. Dyes are identified by thin layer chromatography and high performance liquid chromatography (HPLC), and quantitated by HPLC or colorimetry.

Isolation, identification, and determination of food dyes following ion-pair extraction.

Food dyes are extracted as ion-pairs with tri-n-octylamine and tetrabutylammonium. Extraction from aqueous solutions to chloroform is quantitative with 0.1M counter ion concentrations. The dye may be back-extracted to an aqueous phase with chloride, bromide, iodide, nitrate, or perchlorate ions; perchlorate is most successful. The method is applied to the qualitative analysis of dyes in grenadine, pickles, and milk desserts, and quantitative analysis in alcoholic beverages. Commercial samples are analyzed by using a standard addition method.

Potentiometric determination of iodine in pharmaceutical preparations.

Methods for the determination of organically bound iodine were compared. A preliminary destruction of the sample was preferable. The sample was mineralized using the Schöniger combustion. Since direct potentiometry of the iodide ion was used, further reduction of the sample was necessary. Several reductors were compared, and the best results were obtained with Devarda alloy. The proposed method was amployed for the determination of iodine in X-ray contrast products. Pure compounds and pharmaceutical preparations were investigated. The coefficient of variation of the method was 0.9%.

Evaluation and optimal combination of TLC systems for qualitative identification I: sulfonamides.

A mathematical criterion for the evaluation of chromatographic analysis procedures is given by the information content as derived from Shannon's equation. This information content yields a numerical value representative of the merits of each chromatographic separation and thus allows selection of the optimal systems. In most cases, however, one analysis is not sufficient to allow the qualitative identification of the sample. Therefore, several chromatographic systems are combined. Two approaches allow the desired combination; one either calculates the information content of several procedures as one mathematical value or classifies the systems according to mutual resemblance by numerical taxonomy techniques. From the resulting groups of dissimilar systems, one optimal system can be chosen per group according to the information content. The results obtained by these mathematical procedures are illustrated with a practical example: the selection and evaluation of systems for the TLC analysis of sulfonamides.

A contribution to the study of fluoride excretion.

Three population groups (two of them consisting of school-going children) with a low content of fluoride in the drinking water have been used to investigate parameters influencing fluoride excretion. For the population living in an area contaminated by F-air pollution, there was no significant effect of age or sex from 3 to 17 years. For the population living in a non-contaminated area, there is an increase with age. The data are distributed according to log normal. To determine these excretion levels, first-morning samples were used and it is concluded that for population research (not necessarily for individuals) this is more practical than 24-h samples and yield reliable results. To correct for urine concentration, correlation with Ca2+, Cl- and creatinine were investigated. Low or insignificant correlations were obtained.