This paper describes a strategy for the development of chromatographic methods for drug candidates based upon the use of simple MS compatible mobile phases and optimization of the chromatographic selectivity through variations of the stationary phase and mobile phase pH. The strategy employs an automated column selection system and a series of HPLC columns, varying in hydrophobicity and silanol activity, in combination with DryLab software to develop chromatographic methods for the separation of mixtures of bupivacaine and its metabolites; acidic, basic, and neutral compounds; and atenolol, nitrendipine, and their degradation products.
A rapid sequential injection spectrophotometric method
for the selective determination of 2,4,6-trinitrotoluene
(TNT) in soil samples is presented. The method is based
on a derivatization reaction of TNT with sodium sulfite in
a basic acetone medium. The reaction conditions, namely
the percentage of acetone used in the reaction, the sample
and reagent volumes, the mixing coil volume, and the
reaction time, were optimized. The reaction was found to
be particularly sensitive to the concentration of acetone;
an acetone/water medium of 88% (v/v) acetone was found
to be optimal. A study of the response of the method to
other explosives demonstrated that the method is selective
for TNT. In particular, it was shown that the method had
little (<2%) or no response to other secondary explosives
such as 2,4- or 2,6-dinitrotoluene (DNT). An average
precision of 6.1% RSD was established for five soil
samples (n = 4). The limit of detection was 0.5 μg mL-1
for aqueous standards and 80 μg g-1 for ∼300 mg soil
samples. Analysis time was approximately three minutes
per sample. Quantitative results from the determination
of TNT in authentic contaminated soil samples compared
favorably to those obtained using a standard method. The
extension of the method to water samples and the means
by which samples can be preconcentrated on-line using
solid-phase extraction (SPE) techniques are discussed.
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