Performance characteristics of methods of analysis used for regulatory purposes. I. Drug dosage forms. F. Gravimetric and titrimetric methods.

The original gravimetric and titrimetric methods approved by AOAC for the analysis of pharmaceutical preparations, particularly during the period 1915-1950, show precision, recovery, and outlier parameters approximately the same as those exhibited by the previously reviewed instrumental methods that are currently used. Fifty-nine published collaborative studies utilized gravimetric methods and 85 used titrimetric. The studies of the gravimetric methods encompassed 47 analytes, 95 dosage forms, and 136 assays; the corresponding figures for the titrimetric studies are 72, 112, and 152. An average of approximately 7 laboratories participated per study. The line of best fit of the relative standard deviation between-laboratories (RSDR) plotted against the negative logarithm of the fractional concentration, C, extends from 1.2 and 1.0% for the gravimetric and titrimetric methods, respectively, at 100% concentration to 2.2 and 2.8% at 1.0% concentration. Below this concentration the precision of the titrimetric methods degenerates faster than that of the gravimetric methods. Above about 0.1% concentration the gravimetric and titrimetric methods are somewhat more precise than the instrumental methods in current use for drug analysis. The difference, however, is not statistically significant and the general equation, RSDR = 2 exp(1-0.5 log C), is also applicable to gravimetric and titrimetric methods above a concentration level of about C = 0.001 (0.1%).

Quantitative liquid chromatography of ampicillin: collaborative study.

A previously published liquid chromatographic method proposed for official use for the analysis of ampicillin in the market place was subjected to an international collaborative study. The method is rigorously defined in terms of performance requirements, yet allows a degree of flexibility to the individual analyst. Twenty-four participating laboratories from 9 countries submitted results of analysis of 3 samples. The data from one laboratory were rejected because they failed to meet the prescribed performance criteria. Evaluation of the data shows a coefficient of variation less than 1.8% between laboratories for each sample.

Quantitation of amphotericins by reverse-phase high-performance liquid chromatography.

A reverse-phase high-performance liquid chromatographic (HPLC) method was developed for simultaneous potency determination of amphotericin A and amphotericin B in bulk amphotericin B preparations. This single, rapid, specific, and simple method can be used for qualitative and quantitative analyses and is proposed to replace a combination of cumbersome official tests presently in use. This new HPLC method employs an isocratic acidic phosphate bufhotericin A and amphotericin B in bulk amphotericin B preparations. This single, rapid, specific, and simple method can be used for qualitative and quantitative analyses and is proposed to replace a combination of cumbersome official tests presently in use. This new HPLC method employs an isocratic acidic phosphate buffer-methanol mixture in a reverse mode on an octade-cylsilane-bonded silica column at ambient temperature, using UV detection at 313 nm. Results obtained by HPLC compare favorably with the official assay results. During these studies, an apparent heptaenic component, not previously described, was detected in commercial amphotericin B preparations at concentrations ranging from approximately 6 to 14%.

High pressure liquid chromatographic determination of antihistamine-adrenergic combination products: collaborative study.

A reverse phase high pressure liquid chromatographic method in which ion-pairing is used for the determination of combinations of pseudoephedrine hydrochloride with triprolidine hydrochloride or chlorpheniramine maleate in syrups and tablets was collaboratively studied by 8 laboratories. Collaborators were supplied with 12 samples including synthetic and commercial syrup formulations and commercial tablet composites. Mean recoveries of pseudoephedrine hydrochloride and triprolidine hydrochloride from synthetic syrup formulations were 100.5 and 99.6%, respectively. Mean recoveries of pseudoephedrine hydrochloride and chlorpheniramine maleate from synthetic syrups were 98.8 and 100.5%, respectively. Mean coefficients of variation for syrups and tablets ranged from 1.68 to 3.07% for pseudoephedrine hydrochloride, from 2.92 to 3.85% for triprolidine hydrochloride, and from 1.34 to 2.15% for chlorpheniramine maleate. The method has been adopted official first action.

GLC determination of N,N-dimethylaniline in penicillins.

A reliable GLC procedure was developed for the determination of residual N,N-dimethylaniline as a contaminant in ampicillin commerical samples from various sources. The procedure was similarly applied to other penicillins and cephalosporins. The method involves dissolution of the sample in aqueous alkali, extraction of the organic base with cyclohexane containing naphthalene as an internal standard, and injection into gas chromatograph with a phenyl methyl silicone column. Levels of 0.1 ppm of dimethylaniline were easily measured with a coefficient of variation less than 10%, and recoveries from spiked samples exceeded 99%.

GLC analysis of griseofulvin: a collaborative study.

A GLC method for the assay of griseofulvin in bulk and dosage forms was subjected to a wide and rigorous collaborative study. An overall recovery of 99.52 plus or minus 2.33% for three samples from 19 participating laboratories was obtained. The success of this study is ascribed to the fact that strict performance requirements are specified for the operating system.