Determination of enantiomers in a synthetic argininal peptide using capillary zone electrophoresis and high-performance liquid chromatography.

SCH 201781 is a synthetic argininal peptide containing two chiral centers and an aromatic sulfonamide group. It can exist as four reversible forms, the aldehyde, the hydrate, and two diastereomeric aminals. Capillary zone electrophoresis (CZE) and reversed-phase high-performance liquid chromatographic (HPLC) methods were developed to separate and quantitate the enantiomers in SCH 201781. Comparable results were obtained using both methods. The CZE method uses direct injection, while the HPLC method requires a precolumn derivatization and is more time consuming. The CZE method provides superior sensitivity to the HPLC method. Both methods were shown to be precise and reproducible.

Automated stability-indicating high-performance liquid chromatographic assay for ethinyl estradiol and (levo)norgestrel tablets.

An automated high-performance liquid chromatography (HPLC) assay for ethinyl estradiol and norgestrel or levonorgestrel in oral contraceptive tablets was developed. Tablets were prepared for on-line injection using a solid sampler and segmented continuous flow techniques. The active components were separated from tablet excipients, impurities, and degradation products on reversed-phase C8 and C18 columns by elution with water-acetonitrile-methanol (45:35:15). A UV detector connected in series with a fluorometric detector measured the UV absorbance of levonorgestrel and norgestrel at 240 nm and the fluorescence of ethinyl estradiol at 310 nm (excitation at 210 nm). The method employed computer control of the injection system and solid sampler for synchronization of the chromatographic and segmented flow streams. The method is applicable for content uniformity and stability testing at a rate of eight samples per hour.

Liquid chromatographic assays for barbiturate injections.

Precise, rugged, stability-indicating HPLC assays were developed for phenobarbital, pentobarbital, and secobarbital sodium injections. Degradation products of the three barbiturates were prepared and chromatographed to demonstrate method specificity. The degradation products were also used to demonstrate specificity of official GC methods for pentobarbital and secobarbital sodium capsules. The acetylurea degradation products of pentobarbital and secobarbital were characterized following the separation of their diastereoisomers by HPLC.

Stability-indicating high-performance liquid chromatographic assay for oxazepam tablets and capsules.

A stability-indicating high-performance liquid chromatographic (HPLC) assay for oxazepam in capsules and tablets was developed. The material was extracted with 2% aqueous methanol and chromatographed on a C18 reverse-phase column, which was eluted with methanol-water-acetic acid (60:40:1). A wavelength of 254 was used for detection. This assay separated oxazepam from all degradation products mentioned in the literature or observed in stress-degraded samples. Degradation products could be detected at the 0.1% level. Degradation of oxazepam to 6-chloro-4-phenyl-2-quinazolinecarboxaldehyde and 2-amino-5-chlorobenzophenone was observed after either acid or base treatment. Acidic conditions also afforded 2'-benzoyl-4'-chloroglyoxanilide and 6-chloro-4-phenyl-2(1H)-quinazolinone.

Purity profiles of pteroylglutamate reference substances by high-performance liquid chromatography.

High-performance liquid chromatography (HPLC) in the reversed-phase mode was used for the purity analysis of three pteroylglutamic acid-type reference substances (folic acid, leucovorin calcium, and methotrexate). The influence of the pH of the mobile phase on the separation of an artificial mixture of six pteroylglutamic acid derivatives and three potential impurities was studied. Results of purity analysis of current lots of USP reference standards are reported. A better separation of methotrexate from its major impurities was achieved by using a standard buffer, rather than an ion-pairing mobile phase. A separation of methotrexate and its biologically inactive 7-isomer is reported.

Chromatographic assays for folic acid.

TLC and high-pressure liquid chromatographic (HPLC) assays for folic acid were developed. In the TLC procedure, the folic acid band was extracted from the silica gel after development and determined spectrophotometrically by an oxidation and Bratton-Marshall sequence. A column packed with octadecylsilane chemically bonded to microparticulate silica gel was used for the HPLC assay. Potentiometric determination of water in folic acid samples was necessary to obtain accurate purity values. In a comparison of four assay methods, a direct colorimetric method gave precise, but unspecific, results, while the USP XIX colorimetric method lacked both precision and specificity. The two chromatographic methods were both precise and specific and gave the same assay results. Both methods separated p-aminobenzoic acid, N-(p-amino-benzoyl)-L-glutamic acid, 2-amino-1,4-dihydro-4-oxo-6-pteridinecarboxylic acid, 2-amino-4(1H)-pteridinone, and several unidentified impurities from folic acid.

Metabolism of 1-(0-chlorophenyl)-1-(p-chlorophenyl)-2,2-dichloroethane (o,p'-DDD) in rats.

The metabolism of 14C-labeled 1-(p-chlorophenyl)-2,2-dichloroethane (o,p'-DDD) in rats was investigated. Metabolites were identified in feces and urine extracts by thin-layter chromatography (TLC), gas-liquid chromatography, and mass spectropmetry. Extracts of acidic metabolites were methylated with diazomethane for identification. Metabolites were quantitated by TLC and liquid scintillation counting. After a 100-mg oral dose to each of three rats, an average of 7.1% of the radioactivity was excreted in the urine and 87.8% in the feces within 8 days. The urine was found to contain o,p'-dichlorodiphenylacetic acid (o,p'-DDA) as well as 4-hydroxy-, 3-hydroxy-, and 3,4-dihydroxy-substituted o,p'-DDA. The serine and glycine conjugates of o,p'-DDA were also identified. In addition to the above metabolites the feces contained o,p'-DDD. 1-(o-chlorophenyl)-1-(P-chlorophenyl)-2-chloroethylene, and the aspartic acid conjugate of o,p'-DDA. The presence of aromatic mono- and dihydroxylated o,p'-DDD was also detected in feces.