High-pressure liquid chromatography of drugs. An evaluation of an octadecylsilane stationary phase

Determination of ketoprofen in biological fluids by reversed-phase chromatography

A sensitive and specific high-performance liquid chromatographic method was developed for the determination of ketoprofen [2-(3-benzoylphenyl)propionic acid] in plasma and urine. The method includes an extraction of the drug and the internal standard [2-(4-benzoylphenyl)butyric acid] into ether from acidified plasma. The organic phase is evaporated, and the residue is dissolved in the mobile phase (acetonitrile-0.02 M phosphate buffer, pH 3) (45:55). A 20-microliter aliquot is analyzed on a reversed-phase column. The accuracy is within 1.5% for therapeutic concentrations, and the coefficients of variation are 5.5 and 3.4% for 2 and 10 micrograms/ml, respectively. For the urine assay, the accuracy is within 3%, and the cofficients of variation are 1.9 and 1.7% for 3 and 50 micrograms/ml, respectively. This method was applied successfully to the determination of ketoprofen in humans for pharmacokinetic studies.

Determination of isofezolac in biological fluids by reversed-phase liquid column chromatography

A rapid, sensitive, and specific reversed-phase high-performance liquid chromatography assay was developed for the determination of 1,3,4-triphenylpyrazole-5-acetic acid (isofezolac) in plasma and urine. The assay involves extraction into diethyl ether from plasma buffered at pH 4.4. The organic phase is evaporated and the residue, dissolved in the mobile phase [acetonitrile-water-0.2 M phosphate buffer (pH 3) (65 : 15 : 20)] is chromatographed at a flow-rate of 1.5 ml/min. The drug is detected by its UV absorption (detection limit 100 ng/ml) or its very intense fluorescence (detection limit 10 ng/ml). Absolute analytical recoveries for isofezolac varied from 92.9 to 100.4%. The accuracy is ca. 1%. Each separation requires about 6 min. This method was applied successfully to the determination of isofezolac in humans for pharmacokinetic studies.

Simultaneous high-pressure liquid chromatographic determination of acetaminophen, guaifenesin, and dextromethorphan hydrobromide in cough syrup

Acetaminophen (I), guaifenesin (II), and dextromethorphan hydrobromide (III) were separated and quantitated simultaneously in cough syrup by high-pressure liquid chromatography. A chemically bonded octadecylsilane stationary phase was used with a mobile phase of 48% (v/v) aqueous methanol. The mobile phase pH was stabilized to 4.2 by adding formic acid--ammonium formate buffer (approximately 0.4%). The internal standard was o-dinitrobenzene. Retention volumes were 4 ml for I, 6 ml for II, 11 ml for the internal standard, and 20 ml for III. Inactive syrup components did not interfere, permitting direct diluted sample injection. Results on active ingredients were essentially 100% of the claim, with standard deviations of +/- 1.5, 1.2, and 2.1% for I, II, and III, respectively.

Rapid determination of chlorpromazine hydrochloride and two oxidation products in various pharmaceutical samples using high-performance liquid chromatography and fluorescence detection

A rapid, simple, and accurate high-performance liquid chromatographic procedure using an amino-bonded microparticulate column is reported for the determination of chlorpromazine hydrochloride (I) and its two oxidation products, the sulfoxide (II) and the sulfone (III), in commercially available pharmaceutical dosage preparations. Simultaneous identification and quantitation of II and III in the presence of at least 100 times the amount of parent compound were achieved with selective fluorometric detection. Identification and quantitation of I were achieved by changing the fluorescence detection mode. A typical chromatographic run was completed within 15 min. The described procedure is simpler, more sensitive, and more accurate than the USP XIX methods, particularly for the analysis of II in injectables. Quantitation of II and III at levels as low as 0.1 microgram, representing 0.1% contamination, was demonstrated.

Determination of the anti-allergenic agent, 2-methoxy-11-oxo-11H-pyrido[2,1-b]quinazoline-8-carboxylic acid, in biological fluids by high-performance liquid chromatography

A rapid, sensitive, and specific high performance liquid chromatographic (HPLC) assay was developed for the determination of 2-methoxy-11-oxo-11H-pyrido-[2,1-b]quinazoline-8-carboxylic acid (I) from biological fluids. The overall recovery from blood and plasma is 69 +/- 10% (S.D.) and 84 +/- 6% (S.D.), respectively, and the sensitivity limit of quantitation is 100 ng/ml by UV absorption and 5 ng/ml by fluorescence detection using a 1 ml specimen. The assay was used in the determination of blood levels of compound in the Rhesus monkey following intravenous administration of a 10 mg/kg dose, and of blood and urine levels of compound I in a dog following intravenous and oral administration of a 1 mg/kg dose.

Determination of buflomedil hydrochloride [2',4',6'-trimethoxy-4-(pyrrolidinyl)butyrophenone hydrochloride] by reversed-phase ion-pair high-performance liquid chromatography

A simple and rapid method for the determination of buflomedil hydrochloride [2',4',6'-trimethoxy-4-(pyrrolidinyl)butyrophenone hydrochloride] in pharmaceutical formulations by reversed-phase ion-pair high-performance liquid chromatography is described. The sample is dissolved in methanol and 1,3,5-trimethoxybenzene is added as an internal standard. The resulting solution is chromatographed on an octadecylsilane column using ion-pair partition chromatography with lauryl sulphate as the counter ion. A 25-microliter injection (containing 3.5 micrograms of buflomedil hydrochloride) produces a 60% full-scale peak (0.2 a.u.f.s.) at the absorbance maximum (275 nm). The relative standard deviation of the method ranges from 1 to 3%, depending on the particular tablet formulation examined. Excipients present in the preparations do not interfere.

Simultaneous quantitation of morphine and paraben preservatives in morphine injectables

A high-performance liquid chromatographic method for the simultaneous determination of morphine sulfate, methylparaben, and propylparaben in morphine sulfate injection was developed. A reversed-phase system, based on an octadecylsilane stationary phase, was used with a binary solvent mobile phase consisting of methanol--phosphate buffer (pH 4.0) containing methanol (5%) delivered at a constant rate (0.6:0.4 ml/min) using a two-pump system. The detector response at 254 nm was linear with the amount injected over a wide range, allowing rapid and reproducible quantitation of each component.

Analysis of LSD in human body fluids by high-performance liquid chromatography, fluorescence spectroscopy and radioimmunoassay

A scheme of analysis is described in which the particular advantages of high-performance liquid chromatography (HPLC), fluorescence spectroscopy and radioimmunoassay (RIA) are exploited to the greatest effect. RIA affords a rapid and sensitive preliminary screening method, while the subsequent HPLC analysis using fluorimetric detection yields quantitative chromatographic evidence together with characteristic fluorescence spectra. Fractionation of samples by HPLC followed by RIA of the fractions gives further confirmation of the presence of LSD and its metabolites. The combined methodology has been applied to the analysis of LSD in body fluids for forensic and clinical purposes. Levels down to 0.5 ng of LSD per ml can be detected using the minimum of sample.

Determination of imipramine in plasma by high pressure liquid chromatography and field ionization mass spectrometry: increased sensitivity in comparison with gas chromatography mass spectrometry

A quantitative method is reported for the determination of imipramine in plasma samples in the low nanogram and subnanogram range. The sensitivity and precision of the technique, which involves high pressure liquid chromatography and direct probe field ionization mass spectrometry, are approximately an order of magnitude greater than are offered by gas chromatography mass spectrometry with selected ion monitoring using deuterated or other types of internal standards. [2H6]Imipramine, labeled in the ethylene bridge and in the aromatic rings, serves as the isotopic diluent. The method has been used for the determination of the comparative bioavailabilities of two different commercial preparations of imipramine. In these tests, subjects ingested a 25 mg tablet of one or the other drug preparation together with a solution containing an equivalent amount of imipramine deuterated in the ethylene bridge ([2H2]imipramine). The latter served as an internal check for intrasubject variability in absorption of the imipramine tablets. Typical results from one of the subjects are presented.

Dihydroergotoxine: separation and determination of four components by high-performance liquid chromatography

The evaluation of a new high-performance liquid chromatographic method is described. It permits the separation and determination of the four components of dihydroergotoxine (dihydroergocristine, dihydroergocornine, dihydro-alpha-ergocryptine, and dihydro-beta-ergocryptine) in a single step. On reversed-phase microparticles, complete baseline separation is possible with different mobile phases containing about 10(-2) M base. The analysis of dihydroergotoxine mesylate drug substance or its dosage forms can be carried out in about 15 min. No reference substance is required for the determination of the proportions of the components. This method is simple and exhibits high accuracy, reproducibility, and selectivity. It permits the analytical control of dosage forms containing dihydroergotoxine mesylate to ensure that they comply with the specifications for the drug substance used in clinical and pharmacological studies.

High-speed liquid chromatographic analysis of dapsone and related compounds

A nonaqueous solvent absorptive support system and an aqueous solvent reversed-phase support liquid chromatographic system for analysis of dapsone and related compounds were investigated. The absorptive support system was more suitable for analysis of dapsone in raw materials, formulations, and tissue residues. The suitability was judged by the relative selectivity, efficiency, precision, and sensitivity of the systems. The adsorptive support system was used for the analysis of trace amounts of raw material impurities and dapsone metabolites. Coupling fluorometric detection to the chromatographic system yielded a 10-pg on-column detection limit for dapsone; the UV detection limit was 250 pg.

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.

Chromatographic characterization of phenothiazine drugs by a reversed-phase thin-layer technique

A reversed-phase thin-layer chromatographic technique was used for the characterization of 26 phenothiazine drugs. With two chromatographic systems having the sam stationary phase and phase volume ratio, but mobile phases of different pH, all but two of the compounds could be identified. Rf values in the different systems were standardized by applying a reference compound to the plates next to each compound under investigation; the corrected Rf values were calculated from the differences in the Rm values of the compounds and the reference compound, and the theoretical Rm value of the reference. It was shown that Rf values for different chromatographic systems with the same stationary phase could be predicted with reasonable accuracy. The pH of the mobile phase, for which a maximum difference in Rf values was obtained for pairs of compounds, could also be calculated and corresponded well with the observed values.

Analysis of benzoylecgonine in urine by high-performance liquid chromatography and gas chromatography-mass spectrometry

Benzoylecgonine, a polar metabolite of cocaine, was extracted and purified from urine using a reversed-phase high-performance liquid chromatographic column. The portion of the eluent corresponding to elution of the drug was collected, derivatized, and quantified using gas chromatography-mass spectrometry with selected ion monitoring. Using this procedure, analysis of 1 ng/ml of benzoylecgonine in urine can be achieved.

Forensic aspects of high-pressure liquid chromatography

This paper reviews the applications of high-pressure liquid chromatography (HPLC) to forensic problems, and discusses some of the developments that have taken place in the use of the technique in the Metropolitan Police Laboratory. Preparation of octadecyltrichlorosilane-modified silica is described and some of the chromatographic characteristics of this material are investigated. Applications of HPLC to the analysis of cannabis, opium alkaloids, amphetamine-related materials, LSD and polynuclear hydrocarbons are described.

Applications of high-performance liquid chromatography in the pharmaceutical industry

A survey of the literature has been carried out, covering pharmaceutical applications of high-performance liquid chromatography (HPLC) from 1972-1975. The abstracts are divided into seven groups, viz. alkaloids, antibiotics, nitrogen-containing compounds, steroids, sulphur-containing compounds, formulations, and general analytical techniques. A general resume of the development of HPLC in our own laboratory from 1969 onwards is given together with fourteen chromatograms covering the spectrum of our more novel activities in pharmaceutical analysis.

High-pressure liquid chromatography of drugs. II. An evaluation of a microparticulate cation-exchange column

A microparticulate cation-exchange column has been evaluated for the chromatography of thirty compounds selected as representative of a wide variety of drug substances. Although the column exhibited a strong partition effect besides the expected ion-exchange mechanism, the retention of drugs could be predictably influenced by variation of the eluent ionic strength and organic solvent content. For acidic drugs the column showed little selectivity (although a salting-out effect increased retention at high eluent ionic strengths), but for basic substances Partisil SCX may afford a useful separative medium offering reasonable chromatographic efficiency (HETP is approximately 0.1 mm). The column longevity, however, is at present questionable.