Determination of Chloral Hydrate in Soft Gelatin Capsules by NMR

Quantitative 1H NMR: Development and Potential of a Method for Natural Products Analysis

“…The most widely used is maleic acid, which was the reference compound of choice in a number of quantitative qHNMR studies involving catecholamines, 78 muscle relaxants, 79 and antidepressants, 80 as well as in the semiquantitative analyses of herbal drug preparations such as kava-kava 81 and in mixtures of methamphetamine and ephedrine in substances of abuse. 82 The publications by Turczan and co-workers [32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51] are a valuable source of qHNMR reference standards and include tert-butyl alcohol, 1,4-dinitrobenzene, hexamethylcyclotrisiloxane, methenamine, biphenyl, benzyl benzoate, and again maleic acid. One report proposes the 1 H singlet signal of 1,4-dioxane for calibration, 83 which raises a caveat with regard to its volatility (bp 101 °C).…”

“…Their articles cover relaxation, digitization, and instrumental parameters and provide valuable sources of information independent from the observed nuclei. Certainly noteworthy, while exclusively dealing with analyses of drugs and pharmaceuticals, is the extensive qHNMR work by Turczan and co-workers at the FDA, [32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51] which to our best knowledge has not been summarized in a review format. Their experience shows that typical errors fall in the 0.5-2% range, and their reports serve as a valuable resource when it comes to the selection of qNMR reference standards (see below).…”