Gas chromatography-mass spectrometry of carbonyl compounds in cigarette mainstream smoke after derivatization with 2,4-dinitrophenylhydrazine

An improved gas chromatography-mass spectrometry (GC-MS) method was described for the analysis of carbonyl compounds in cigarette mainstream smoke (CMS) after 2,4-dinitrophenylhydrazine (DNPH) derivatization. Besides formaldehyde, acetaldehyde, acetone, acrolein, propionaldehyde, methyl ethyl ketone, butyraldehyde, and crotonaldehyde that are routinely analyzed in cigarette smoke, this technique separates and allows the analysis of several C4, C5 and C6 isomeric carbonyl compounds. Differentiation could be made between the linear and branched carbon chain components. In cigarette smoke, the branched chain carbonyls are found at higher level than the linear chain carbonyls. Also, several trace carbonyl compounds such as methoxyacetaldehyde were found for the first time in cigarette smoke. For the analysis, cigarette smoke was collected using DNPH-treated pads, which is a simpler procedure compared to conventional impinger collection. Thermal decomposition of DNPH-carbonyl compounds was minimized by the optimization of the GC conditions. The linear range of the method was significantly improved by using a standard mixture of DNPH-carbonyl compounds instead of individual compounds for calibration. The minimum detectable quantity for the carbonyls ranged from 1.4 to 5.6 microg/cigarette.

High-performance liquid chromatographic analysis of dehydroepiandrosterone

Qualitative and quantitative analysis of dehydroepiandrosterone and its conjugates in biological matrices and establishment of their relationships with physiological functions is a very active field. This review article discusses methods of separation and quantification of dehydroepiandrosterone and its conjugates using high-performance liquid chromatographic techniques.

Determination of eltanolone in human plasma by high-performance liquid chromatography

A high-performance liquid chromatographic method for the determination of eltanolone in plasma has been developed. Plasma samples containing eltanolone were diluted with acetonitrile to precipitate plasma proteins, and derivatized with 2,4-dinitrophenylhydrazine before direct injection onto a C18 column. The mobile phase was acetonitrile-water (70:30, v/v) containing 0.1% trifluoroacetic acid and detection was by UV absorbance at 367 nm. The quantitation limit was 0.020 microg/ml. The method has proven to be rapid, precise and sensitive in the range of concentrations found during and following intravenous anaesthesia.

Determination of 4-hydroxycyclophosphamide in plasma, as 2,4-dinitrophenylhydrazone derivative of aldophosphamide, by liquid chromatography

A reversed-phase liquid chromatographic method to determine the concentration of 4-hydroxycyclophosphamide, a labile cytotoxic metabolite of cyclophosphamide, in plasma is described. In order to stabilize 4-hydroxycyclophosphamide, as well as to increase the selectivity and the sensitivity, a 2,4-dinitrophenylhydrazone derivative was formed. Plasma proteins were precipitated with acetonitrile prior to the derivatization with 2,4-dinitrophenylhydrazine at pH 2. The derivatization was performed at 50 degrees C for 5 min. The chromatographic system consisted of an octadecyl silica column and a mobile phase containing phosphate buffer and acetonitrile. Quantitation was performed using an UV detector operating at 357 nm. Optimal derivatization was obtained by adding 0.2 ml 2,4-dinitrophenylhydrazine (3.8 mg/ml) to 0.5 ml of the deproteinized plasma supernatant. The relative recovery of 4-hydroxycyclophosphamide from plasma is > or = 97%. Concentration levels down to 22 mg/ml of 4-hydroxycyclophosphamide in plasma could be determined with a R.S.D. of about 13%. No degradation of the derivative was observed after 24 h at room temperature. The t1/2 for 4-hydroxycyclophosphamide in blood is ca. 4 min at 37 degrees C, whereas 4-hydroxycyclophosphamide is stable for at least 1 h at 4 degrees C. Application of the method for the pharmacokinetic monitoring of 4-hydroxycyclophosphamide is described.

High-performance liquid chromatographic method for the determination of finasteride in human plasma at therapeutic doses

A high-performance liquid chromatographic (HPLC) method with ultraviolet detection for the determination of a novel 4-aza-steroidal inhibitor of 5 alpha-reductase in human plasma has been developed. The assay is based on a single solid-phase extraction and an efficient HPLC separation on two analytical columns in series. The assay has been fully validated and used to support Phase II and III clinical pharmacokinetic studies. The lowest limit of quantification was found to be at 1 ng/ml and allowed pharmacokinetic evaluation of the drug at doses down to 5 mg.

Chromatography as a reference technique for the determination of clinically important steroids

Chromatographic methods (paper chromatography, thin layer chromatography, high performance liquid chromatography, gas chromatography and gas chromatography-mass spectrometry) for the determination of clinically important steroids in biological specimens are reviewed. The emphasis is on the use of gas chromatography, gas chromatography-mass spectrometry and high performance liquid chromatography as reference rather than routine techniques. Chromatographic methods are compared with colorimetric, fluorimetric and radioimmunoassay procedures in terms of simplicity of operation, cost and ability to analyse large numbers of specimens. The importance of correct specimen collection and storage are discussed. Sample preparation techniques for the various analytical methods are described. These include extraction of free and conjugated steroids from serum, plasma, urine and saliva by solvent partition, with polymer-based resins such as Amberlite XAD-2, DEAE-Sephadex and Sephadex resins bonded with various other function groups and, more recently, with chemically bonded reversed-phase silicas.

Application of high-performance liquid chromatography to the measurement of cortisol secretion rate

After administration of [3H] cortisol, the specific radioactivity of the urinary cortisol metabolites is determined by chemical conversion of the 17-hydroxycorticosteroid conjugates to 17-ketosteroids, extraction with Sep-Pak C18 cartridges, derivatisation with 2,4-dinitrophenylhydrazine and isocratic reversed-phase high-performance liquid chromatography. This allows on-line measurement of ultra-violet absorbance; fractions are collected and 3H is measured by scintillation counting. Alternatively extraction and chromatography are done after enzymic hydrolysis of the steroid conjugates, and the major metabolites are determined colorimetrically in the fractions. The results from the two methods were consistent with each other and with published data.

Separation of corticosteroids by high-performance liquid chromatography on dynamically modified silica

High-performance liquid chromatographic methods have been elaborated for the separation of 12 different corticosteroids by reversed-phase chromatography on bare silica, dynamically modified by cetyltrimethylammonium bromide added to the eluent. The selectivity of the systems towards a mixture of the 12 corticosteroids and towards a mixture of hydrocortisone and its related impurities were investigated using different brands of silica. The variations in selectivity were found to be substantially smaller than those of chromatographic systems based on chemically bonded ODS-silicas from the same sources.

Clinical applications of the rapid high-performance liquid chromatographic determination of serum cortisol

We report a rapid and specific analytical method for the measurement of serum cortisol by reversed-phase high-performance liquid chromatography (HPLC). The method allows the diagnostic measurement of cortisol in emergency clinical circumstances of glucocorticoid deficiency or excess. Results obtained by HPLC are comparable to those by radioimmunoassay. The lower limit of sensitivity is 6 ng cortisol per ml of serum.

High performance liquid chromatographic analysis of cholesterol in milk

A method was developed for analysis of cholesterol in whole milk powder and commercial liquid milk products. High performance liquid chromatography employed a nonaqueous reversed phase chromatographic system. Sample preparation was by saponification with methanolic potassium hydroxide followed by extraction with ether. Potential interfering substances were removed prior to injection by a simple clean-up procedure using a silica gel Sep-pakTM. The chromatographic system included a carbon-18 column with a hexane/isopropanol mobile phase and detection at 205 nm. Method validation and recovery studies using carbon-14 labeled cholesterol indicated excellent performance.

Formation and separation by reversed-phase high-performance liquid chromatography of fluorescent and UV-absorbing bile salt derivatives

A method is described for the production of bile salt derivatives via the substituent hydroxyl groups on the steroid nucleus that permits derivatization of taurine and glycine conjugates. The method involves the oxidation of the hydroxyl groups at C-3 alpha or C-7 alpha on the nucleus by the action of hydroxysteroid dehydrogenases. The keto bile salts produced are isolated and reacted with 2,4-dinitrophenylhydrazine or Dns-hydrazine to yield ultraviolet absorbing or fluorescent derivatives, respectively. The bile salt hydrazones were separated using a reversed-phase C18 radial compression cartridge with a methanol-phosphate buffer gradient elution. Although the 3-keto derivatives of chenodeoxycholic and deoxycholic acids were not resolved, the 7-keto Dns-hydrazone of chenodeoxycholic acid was separated from 3-keto derivative of deoxycholic acid.

Correlation between the retention of cardiac glycosides in reversed-phase high-performance liquid chromatography with a diphenylsilyl stationary phase, the structure of their molecules and their biological activity

The separation of mixtures of cardiac glycosides by reversed-phase high-performance liquid chromatography on silica gel with chemically grafted diphenylsilyl groups using water-ethanol as the eluent was carried out. It is shown that the configuration and conformation of the glycoside molecules, and the hydrophilic properties of their aglycones and glycones, influence the separation. The hydrophilic properties of the aglycones are more important than those of the glycones. The glycosides with more hydrophilic aglycones have higher biological activity. This is probably related to the easier transport of these glycosides to the receptor.

High-pressure liquid chromatography of steroids

After a brief discussion of the merits and limitations of high-pressure liquid chromatography (HPLC) relative to other chromatographic methods, special problems in the application to steroids are discussed. Publications on HPLC of steroids are then discussed under the headings of individual classes, arranged generally in the order of increasing polarity.

Celite column chromatography followed by reversed-phase high-performance liquid chromatography: a simple, two-step method for separating 14 testicular steroids

The separation of 14 major testicular steroids has been effected by a simple, two-step procedure involving Celite column chromatography followed by reversed-phase high-performance liquid chromatography. The technique does not alter the resolved steroids, which are then available for subsequent analysis.

Separation and quantitation of esterified estrogens in bulk mixtures and combination drug preparations using high-performance liquid chromatography

A high-performance liquid chromatographic method for esterified estrogens is described. By using a facile acid hydrolysis extraction procedure for the sample preparation, the compounds are chromatographed as their free phenolic forms. The separation of structurally similar compounds, such as equilenin, equilin, estrone, and estradiol, was achieved with a reversed-phase column and a methanol--water mobile phase. Several samples of bulk mixtures and tablets were assayed; the results compared favorably with those obtained using the USP XIX method. The method was rapid, and the detector response was linear over a wide concentration range. A relative standard deviation of +/- 5% indicates the reliability and accuracy of the proposed method.

Investigations of anabolic drug abuse in athletics and cattle feed. II. Specific determination of methandienone (Dianabol) in urine in nanogram amounts

A high-performance liquid chromatographic method for the determination of the free excreted anabolic drug methandienone in pharmacokinetic studies is described. After extraction of the free steroids from urine, separation on reversed-phase columns leads to quantitative determination of this drug down to 5 ng, and to qualitative detection of less than 1 ng amounts. Because the anabolic drugs and their metabolites are eluted later than the other normally excreted constituents this method is also useful for the routine surveillance of anabolic drug abuse in the sports in general.

Separation of estrogen conjugates by high pressure liquid chromatography

High pressure liquid chromatography using a prepacked commercial strong anion exchanger column (mu Partisil 10 SAX, 25 cm x 4.6 mm) was used to separate a mixture of eight estrogen conjugates. Chromatographic conditions using a 0.01 M potassium phosphate or 0.1 M NaCl as solvent in the isocratic mode are described for the separation of estrone glucosiduronate, 17beta-estradiol-3-glucosiduronate, 17beta-estradiol-17-glucosiduronate, estriol-3-glucosiduronate, estriol-16alpha-glucosiduronate, estriol-17-glucosiduronate, estrone sulfate and 17beta-estradiol-3-sulfate. This system gives high resolution of the estrogen conjugates in small eluent volumes in less than 30 min. The advantages of this high pressure liquid chromatographic system over other methods of separation are discussed.

A quantitative assay of cortisol in human plasma by high performance liquid chromatography using a selective chemically bonded stationary phase

The extraction and subsequent liquid chromatographic analysis of human plasma samples for cortisol is described. Extraction and chromatography are optimized, resulting in a recovery for cortisol of 96% and a detection limit of 1 microgram cortisol in 100 ml plasma. The application of two chemically modified silicas has been evaluated. The specificity of the method was tested by field desorption - mass spectrometry experiments.

High-pressure liquid chromatography of steroids secreted by human adrenal and testis cells in monolayer culture

Reversed-phase high-pressure liquid chromatography with gradient elution on Zorbax-ODS columns has been used to separate, identify, and measure, spectrophotometrically, the steroids secreted by both human adrenal and testis cells in primary monolayer culture. Three related systems using exponential concave gradients have been developed with the specific objective of resolving the steroids produced by these two tissues. A methanol-water gradient has been used to separate most adrenal steroids, an acetonitrile-water gradient to separate testis steroids, and a dioxane-water gradient to separate polar steroids, including aldosterone. These three systems together permit the resolution of at least 43 naturally occurring steroids, plus four synthetic steroids with adrenocortical activity, with overall total elution times of 1 h or less for each system. Retention data for these steroids are given and the separation of steroids in the biological samples illustrated.

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 free and conjugated 17-ketosteroids (author's transl)]

High-pressure liquid chromatography (HPLC) should be used more frequently in biomedical research because heavy molecules can be analysed at ambient temperature without derivatisation to volatile compounds. In this paper the separation of four free 17-ketosteroids, their ester sulfates and glucuronides by reversed-phase HPLC on a Micropak CH column is described. In order to improve the separation several parameters have been studied. Retention data allow comparison of the hydrophilic behaviour of free and conjugated steroids.

Separation of C27, C28 and C29 sterols by reversed-phase high-performance liquid chromatography on small particles

The application of reversed-phase high-performance liquid chromatography to the analytical- and preparative-scale separation of sterols has been evaluated. The capacity factors, k', for a number of compounds chromatographed on a muBondapak C18 (LESS THAN 10 MUM) COLUMN ARE PRESENTED. C27, C28 and C29 sterols and also sterols differing in degree of unsaturation could be readily separated as their acetates in this system. The present reversed-phase chromatographic method is apparently not as selective as silver nitrate-silica gel thin-layer chromatography for the position of unsaturation in the sterol molecule.

High-speed liquid chromatographic determination of canrenone in pharmaceutical dosage forms

Canrenone can be determined by high-speed liquid chromatography in pharmaceutical dosage forms without interference from common excipients or degradation products. This stability-indicating assay, using o-nitroaniline as the internal standard, is rapid and accurate.

Laboratory automation of high-pressure liquid chromatography

An automated system for high-pressure liquid chromatography was developed. The system is built around commercial modules wherever possible, modified to varying degrees. An automatic sampler, a sample pump, a high-pressure sampling valve, a recorder with an integrator, and a high-pressure liquid chromatograph comprise the commercial instruments. Relays, solenoid valves, and timers control chromatographic events, i.e., duration of sampling and rinse, mobile phase pump refill, sample injection, and chromatographic time. The automated system is dependable over long periods of unattended operation. With the 40-sample capacity of the sample tray and the last sample stop capability, the automated system produces, for example, 40 20-min chromatograms in approximately 13 hr of unattended operation. Data demonstrate the reliability and utility of the system.

Resolution of prostaglandin p-nitrophenacyl esters by liquid chromatography and conditions for rapid, quantitiative p-nitrophenacylation

The p-nitrophenacyl esters of a number of closely related and isomeric prostaglandins were resolved by HPLC on a microparticulate silica gel column (Zorbax-Sil, DuPont). Ten F-series prostaglandin analogs, eight E-series prostaglandin analogs, the isomeric 15(R)- and 15(S)-methyl prostaglandins of the E- and F-series and, lastly, PGA2 and PGB2 were chromatographed under conditions generating 2,000 to 7,000 theoretical plates. Conditions are described for quantitative conversion of prostaglandins to p-nitrophenacyl esters in less than 6 minutes at room temperature. Linear peak height and peak area plots were obtained for in-situ esterified PGE2 p-nitrophenacyl ester over the range of 0.4 - 3.1 mug. The lower limit of detection of this ester is about 1 ng. A linear relationship is observed between silica gel TLC 1/Rf values and HPLC retention times as predicted by theory.

Quantitative determination of cortisol in human plasma by high-pressure liquid chromatography

A method is described for the determination of cortisol in human plasma by high-pressure liquid chromatography. The simplified extraction procedure makes the method applicable to routine clinical assays. Partition chromatography is carried out on a Zorbax-Sil column with the eluent system dichloromethane-ethanol-water. A 78% recovery was obtained for cortisol. The detection limit is 1 mug per 100 ml in 1 ml of plasma. Cortisol values were determined in samples from a random selection of patients.