Nutrient overages and methodology trends.

Because infant formula provides the sole dietary intake for many infants, it is important that the nutrient composition be carefully controlled. Establishing nutrient levels depends on laboratory testing. Current testing methods have certain limitations, some of which can be overcome by modern trends in analytical technology.

Spectrophotometric determination of cephapirin, a cephalosporin antibacterial.

A simple and specific method for the quantitative determination of cephapirin, a cephalosporin antibacterial, in finished bulk and dosage forms is reported. The method is based on reproducible degradation under controlled conditions to an unidentified species, which is measured spectrophotometrically at 375 nm. The procedure can be performed manually on a short series of samples in about 15 min or can be automated for large runs. Precursors and related substances show minimal interference. The coefficient of variation of the automated system is about 1% within days and 1.3% among days.

Gas chromatographic determination of carboxylic acid chlorides and residual carboxylic acid precursors used in the production of some penicillins.

An improved gas chromatographic method is described for the simultaneous determination of carboxylic acid chlorides and related carboxylic acids used in the production of some commercial semisynthetic penicillins. The acid chloride reacts with diethylamine to form the corresponding diethylamide. Carboxylic acid impurities are converted to trimethylsilyl esters. The two derivatives are separated and quantitated in the same chromatographic run. This method, an extension of the earlier procedure of Hishta and Bomstein (1), has been applied to the acid chlorides used to make oxacillin, cloxacillin, dicloxacillin, and methicillin (Figure 1); it shows promise of application to other acid chlorides. The determination is more selective than the usual titration methods, which do not differentiate among acids with similar pK's. Relative standard deviations of the acid chloride determination are 1.0-2.5%. Residual carboxylic acid can be repetitively determined within a range of 0.6% absolute.

High-performance liquid chromatographic determination of kanamycin.

A fast, selective, and precise liquid chromatographic method for simultaneous, independent determination of kanamycins A and B is described. Sample components are separated on a pellicular cation exchanger and monitored by fluorescence using post-column on-line derivatization. Less than 0.35 mug of kanamycin B can be detected in as much as 7 mug kanamycin A injected. The detection limit for kanamycin A is less than 20 ng injected. Reproducibility of the entire chromatographic system is about 1% (2 theta) based upon repeated injections of standards. Precision of repeated process sample preparation is about 6% (2 theta). Chromatographic analysis time is less than 15 min per sample.