Optimization of the high-performance liquid chromatrographic separation of a mixture of natural and synthetic corticosteroids

Liquid chromatographic method development for steroids determination (corticoids and anabolics)

A LC isocratic separation study of a complex mixture containing 18 steroids (corticoids and anabolics), used potentially as growth promoters, was carried out. For this purpose, using a Hypersil ODS column at controlled temperature, mobile phases (from binary to quaternary) prepared from water and MeOH, ACN or THF as organic modifiers and UV detection at 245 nm, were employed (dehydroepiandrosterone was detected at 200 nm). The optimum separation was achieved using water/acetonitrile (65:35, v/v) as mobile phase at 30 degrees C, allowing the separation of 16 out of 18 steroids in about 30 min. The retention scale using optimized binary mobile phases was related with steroids hydrophobicity and structure, allowing a classification into three groups for these compounds. To improve the separation several alkyl-silica packings were tested: Type A (Lichrospher C8) and Type B (Luna C18, Kromasil C18, Purospher C18 and Synergy C12). Taking into account resolution, number of separated compounds and run time analysis the Hypersil column was selected as the best choice for further applications. Calibration graphs were obtained using fluorocortisone, fluoxymesterone or methylprednisolone as internal standard. The optimized separation was applied to the analysis of piglet feed samples spiked with steroids. The sample preparation process included solvent extraction using diethyleter and solid phase extraction using silica cartridges. The recoveries were in the range 70-92%. Decision limits and detection capability were in the range 34-198 and 41-249 microg/kg, respectively. Repeatability was also evaluated.

Method development for betamethasone and dexamethasone by micellar liquid chromatography using cetyl trimethyl ammonium bromide and validation in tablets

An isocratic liquid chromatographic method for the determination of betamethasone (BM) and dexamethasone (DM) using methylprednisolone (MPL) as internal standard and micellar mobile phases consisting of cetyl trimethyl ammonium bromide (CTAB) and organic modifiers such as propanol, butanol and pentanol has been developed. The effect of organic modifiers, surfactant concentration, temperature and flow-rate on the separation has been studied. Method validation for dexametasone or bethametasone in tablets was carried out using a mobile phase 0.24% pentanol and 32.5 mM CTAB, a flow-rate of 0.5 ml min(-1), an Hypersil C18 column (60 degrees C), and UV detection at 243 nm. The recoveries for BM and DM found in the accuracy test were 99 +/- 3 and 101 +/- 2, respectively. Repeatability and intermediate precision expressed as R.S.D. were lower than 5% for both compounds. The proposed method was applied to cocktails containing both compounds.

Quantitative determination of dexamethasone in bovine milk by liquid chromatography–atmospheric pressure chemical ionization–tandem mass spectrometry

Dexamethasone (DXM) is a synthetic glucocorticoid that is authorized for therapeutic use in veterinary medicine. The European Community (EC) fixed a maximum residue limit (MRL) at 2ng/g for liver, 0.75ng/g for muscle and kidney tissues, and 0.3ng/ml for milk, while its use as growth-promoter is completely banned. The purpose of this study was to develop and validate a simple and reliable method to determine DXM residues in bovine milk. Milk proteins were removed by the addition of concentrated trichloroacetic acid and paper filtration. Solid-phase extraction clean-up on a C18 reversed phase column was performed to obtain an extract suitable for liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Chromatographic separation of DXM and the internal standard desoximetasone, was achieved on a PLRP-S polymeric reversed phase column, using a mixture of 0.1% (v/v) acetic acid in water (mobile phase A) and acetonitrile (mobile phase B) as the mobile phases. They were identified using the MS/MS detection technique, and were subsequently quantified. The method has been validated according to the requirements of the EC at 0.15, 0.30 and 0.60ng/ml (being half the MRL, the MRL and double the MRL levels fixed by the EC). Calibration graphs were prepared in the 0.15-5ng/ml range and good linearity was achieved (r>or=0.99 and goodness of fit <or=10%). A limit of quantification of 0.15ng/ml, i.e. half the MRL, was obtained. The limit of detection was 41pg/ml. The decision limit (CCalpha) and detection capability (CCbeta) were 0.48 and 0.76ng/ml, respectively. The within-day and between-day precisions, expressed as R.S.D. values, were all below the maximum allowed R.S.D. values calculated according to the Horwitz equation. The results for accuracy fell within the -50 to +20% range. Recovery was 56%. The method was used for the quantitative determination of DXM residues in milk after intravenous administration of DXM to lactating cows to determine its depletion kinetics.

Analysis of betamethasone, dexamethasone and related compounds by liquid chromatography/electrospray mass spectrometry

A reversed-phase high-performance liquid chromatography/electrospray ionisation mass spectrometry (HPLC/ESI-MS) method has been developed to conclusively differentiate the epimers betamethasone and dexamethasone and various esterification products (betamethasone and dexamethasone 21-acetate, betamethasone and dexamethasone 21-phosphate, betamethasone 17-valerate, betamethasone 21-valerate and betamethasone 17,21-dipropionate) in counterfeit drugs. Good separation with baseline resolution of all epimers or isomers was obtained on a Zorbax Eclipse XDB or Luna C8 column, using a step gradient with mobile phases of 0.05 M ammonium acetate and acetonitrile. Betamethasones can also be distinguished by the relative abundance of their m/z 279 ion in the positive electrospray tandem mass spectra. The LC/MS or LC/MS/MS method developed was successfully applied to the analysis of drug product samples, i.e. creams and tablets.

Method development for corticosteroids and anabolic steroids by micellar liquid chromatography

A systematic optimization of the HPLC separation of a complex mixture containing urinary steroids (anabolics and corticoids), boldenone and bolasterone (synthetic anabolics) by micellar liquid chromatography has been carried out. The isocratic micellar mobile phases (from binary to quaternary) consisted of sodium dodecyl sulphate and organic modifiers such as acetonitrile, tetrahydrofuran, propanol, butanol or pentanol. The effect of the organic modifiers, surfactant concentration, temperature, ionic strength and flow-rate on the separation has been studied. A micellar mobile phase made of 5% propanol and 40 mM surfactant allowed the separation of 13 steroids in about 23 min. A bivariant optimization method for the micellar mobile phase surfactant-propanol corroborated the above results. The separations obtained show good perspectives for future developments.

Determination of natural corticosteroids in urine samples from sportsmen

A method for the determination of natural corticosteroids (cortisone, cortisol, 5beta-dihydrocortisone, 5beta-dihydrocortisol, tetrahydrocortisone and tetrahydrocortisol) found in the urine of sportsmen, was developed using a capillary gas chromatography-mass spectrometry ion trap system. 17alpha-Methyltestosterone was used as an internal standard. The different corticosteroids were determined from the peak area ratios of the [M]; [M-90] and [M-90-90] fragment ions of their methoxime-trimethylsiyl derivatives. Sensitivity (15 ppb), specificity, accuracy (96%) and reproducibility (RSD=4-10%) of the method were demonstrated to be satisfactory for measuring the urinary concentrations of the selected natural corticosteroids.

Clinical measurement of steroid metabolism

Analysis of steroids in biological samples is used routinely in the diagnosis of endocrine disorders. Binding assays (radioimmunoassays, immunosorbant immunoassays and non-radioactive immunoassays) are reported often for the analysis of single steroids in plasma and urine. Chromatographic methods (high-performance liquid chromatography and gas chromatography) are used for steroid profiling where complex mixtures of steroids are analysed and the activity of biosynthetic and metabolic pathways deduced. Mass spectrometry is the ideal reference technique for detection of steroids, allowing high specificity and sensitivity. This review describes the practical issues concerning the quality of the assays performed and the potential pitfalls facing the analyst in the design of such methods. Novel approaches for the quantification of steroids, including microarrays and stable-isotope tracers are described, with these being applied in the research environment as opposed to routine biochemical laboratories.

Sampling and analysis of airborne particulate matter and aerosols using in-needle trap and SPME fiber devices

A needle trap device (NTD) and commercial poly(dimethylsiloxane) (PDMS) 7-microm film thickness solid-phase microextraction (SPME) fibers were used for the sampling and analysis of aerosols and airborne particulate matter (PM) from an inhaler-administered drug, spray insect repellant, and tailpipe diesel exhaust. The NTD consisted of a 0.53-mm o.d. stainless steel needle having 5 mm of quartz wool packing section near the needle tip. Samples were collected by drawing air across the NTD with a Luertip syringe or via direct exposure of the SPME fiber. The mass loading of PM was varied by adjusting the volume of air pulled through the NTD or by varying the sampling time for the SPME fiber. The air volumes ranged from 0.1 to 50 mL, and sampling times varied from 10 s to 16 min. Particulates were either trapped on the needle packing or sorbed onto the SPME fiber. The devices were introduced to a chromatograph/mass spectrometer (GC/MS) injector for 5 min desorption. In the case of the NTD, 10 microL of clean air was delivered by a gas-tight syringe to aid the introduction of desorbed analytes. The compounds sorbed onto particles extracted by the SPME fiber or trapped in the needle device were desorbed in the injector and no carry-over was observed. Both devices performed well in extracting airborne polycyclic aromatic hydrocarbons (PAHs) in diesel exhaust, triamcinolone acetonide in a dose of asthma drug and DEET in a dose of insect repellant spray. Results suggest that the NTDs and PDMS 7-microm fibers can be used for airborne particulate sampling and analysis, providing a simple, fast, reusable, and cost-effective screening tool. The advantage of the SPME fiber is the open-bed geometry allowing spectroscopic investigations of particulates; for example, with Raman microspectroscopy.

Optimization of the high-performance liquid chromatographic separation of a complex mixture containing urinary steroids, boldenone and bolasterone: application to urine samples

An HPLC separation of a complex mixture containing 13 urinary anabolics and corticoids, and boldenone and bolasterone (synthetic anabolics) has been carried out. The applied optimization method involved the use of binary, ternary and quaternary mobile phases containing acetonitrile, methanol or tetrahydrofuran as organic modifiers. The effect of different reversed-phase packings and temperature on the separation was studied. The optimum separation was achieved by using a water-acetonitrile (60:40, v/v) mobile phase in reversed-phase HPLC at 30 degrees C, allowing the separation of all the analytes in about 24 min. Calibration graphs were obtained using bolasterone or methyltestosterone as internal standards. Detection limits were in the range 0.012-0.107 microg ml(-1). The optimized separation was applied to the analysis, after liquid-liquid extraction, of human urine samples spiked with steroids.

High-performance liquid chromatographic optimization study for the separation of natural and synthetic anabolic steroids. Application to urine and pharmaceutical samples

An HPLC separation of a complex mixture containing 14 androgenic anabolic steroids (natural and synthetic) for screening purposes has been carried out. The applied optimization method involved the use of binary, ternary and quaternary mobile phases containing acetonitrile, methanol or tetrahydrofuran as organic modifiers. The effect of different reversed-phase packings and temperature on the separation using acetonitrile as organic modifier was studied. The optimum separation was achieved by using a water-acetonitrile (55:45, v:v) mobile phase and a Hypersil ODS (250 mm x 4.6 mm) 5 microm column (30 degrees C) in about 38 min, allowing the separation of 14 out of 14 compounds tested (when danazol is excluded, 13 out of 14 were separated in 23 min). Calibration graphs were obtained using bolasterone, methyltestosterone and canrenone as internal standards. Detection limits were in the range 0.012-0.11 microg ml(-1). The optimized separation was applied for monitoring the norethindrone acetate hydrolysis from tablets and to the analysis, after liquid-liquid extraction, of urine samples spiked with steroids.

Optimization of separation of a complex mixture of natural and synthetic corticoids by micellar liquid chromatography using sodium dodecyl sulphate. Application to urine samples

A systematic optimization of the separation of a mixture of corticoids by micellar liquid chromatography, using sodium dodecyl sulphate as surfactant, a Hypersil (250 mm x 3.2 mm I.D.) C18 column, a flow-rate of 0.5 ml min(-1), and UV absorbance detection at 245 nm has been carried out. Several mobile phases consisting of sodium dodecyl sulphate and different organic modifiers were tested of which tetrahydrofuran, PrOH and BuOH were finally selected. On the basis of analysis time, resolution and number of compounds separated, a mobile phase containing 36 mM sodium dodecyl sulphate and 1.91% butanol allowed the separation of thirteen corticoids out of sixteen in about 27 min. Under these conditions the optimal concentration of sodium dodecyl sulphate was found to be 36 mM. A bivariant optimization method for the mobile phase BuOH-sodium dodecyl sulphate corrobored these results. The effects of temperature, ionic strength and flow-rate effect have also been studied. The most important analytical figures of merit were assessed and compared with those obtained using conventional mobile phases. The optimized method was applied to human urine samples of subjects administered with Dezacor (tablets containing 30 mg of the active ingredient deflazacort) with and without sample preparation.

Simultaneous determination of triamcinolone acetonide and hydrocortisone in human plasma by high-performance liquid chromatography

A validated HPLC method for the simultaneous determination of triamcinolone acetonide and hydrocortisone has been established to monitor the plasma levels of the compounds in healthy volunteers following intramuscular (i.m.) administration of triamcinolone acetonide. Plasma (1.0 ml) was extracted with dichloromethane after addition of the internal standard, fluocortolone. The compounds were separated using a LiChrospher RP 18 column and detected by UV absorbance. Specificity, linearity, as well as the repeatability, intermediate precision and accuracy of the method were established. The limit of quantification was 0.6 ng/ml for triamcinolone acetonide (C.V. = 8.7%, R.E. = 2.6%, n = 6) and 2.0 ng/ml for hydrocortisone (C.V. = 8.3%, R.E. = 2.8%, n = 6). Data on the stability of triamcinolone acetonide in human plasma are presented. Recovery of the compounds and the internal standard have been studied. The results of quality control samples (n = 126) determined during routine analysis of volunteer samples are described. Plasma levels of triamcinolone acetonide after i.m. administration of 40 mg of triamcinolone acetonide are presented.

Extraction and high-performance liquid chromatographic separation of deflazacort and its metabolite 21-hydroxydeflazacort. Application to urine samples

Two HPLC methods for the separation of a mixture of corticoids including the oxazolinic corticoid deflazacort and its metabolite 21-hydroxydeflazacort using different water-tetrahydrofuran mobile phases were developed. Both separations allowed the detection and determination of fifteen out of sixteen corticoids using different C18 columns. Extraction data for deflazacort and its metabolite using different extraction procedures are also reported. These separation conditions were applied to urine samples from two male volunteers administered Dezacor, with both doping control and clinical purposes.

Solvent and solid-phase extraction of natural and synthetic corticoids in human urine

Optimization of the main variables that affect solvent and solid-phase extraction processes, using disposable C18 cartridges and the non-ionic polymeric resin Serdolit AD-2, of human urine containing natural and synthetic corticoids is described. The data were obtained from different HPLC separations of these compounds using calibration graphs obtained before and after extraction of these compounds. The procedures, including sample preconcentration, showed efficiencies over 90%. NaCl was used to avoid emulsion formation in solvent extraction. The results achieved using solvent and solid-phase extraction are discussed.