Determination of cortisol in human plasma by capillary gas chromatography-mass spectrometry using [2H5] cortisol as an internal standard

Review: derivatization in mass spectrometry-6. Formation of mixed derivatives of polyfunctional compounds

The review describes chemical transformations of multifunctional compounds (amino acids and peptides, amino alcohols, amino thiols, hydroxy acids, oxo acids, oxo alcohols, compounds containing simultaneously three or more different groups etc.) by using step-wise or one-step modification or protection of functional groups. Some chemical aspects of mixed derivatization performed for improving the physical-chemical properties and mass spectral characteristics are discussed. Application of mixed derivatization to qualitative and quantitative analysis of various multifunctional compounds mainly in biological fluids and other matrices by gas chromatography/mass spectrometry in electron ionization, chemical ionization, negative-ion chemical ionization and selected ion monitoring modes is considered.

Determination of serum cortisol by isotope-dilution liquid-chromatography electrospray ionization tandem mass spectrometry with on-line extraction

A liquid chromatographic-mass spectrometric method for the determination of cortisol in serum using atmospheric pressure electrospray ionization and tandem mass spectrometry is described. During sample preparation, 150 microl of serum were deproteinized with methanol/zinc sulfate followed by on-line solid phase extraction employing column switching. Tri-deuterated cortisol was used as the internal standard. The following transitions were monitored: cortisol, 363>309 m/z; d3-cortisol, 366>312 m/z. The total run-time was 5 minutes. The method proved linear (0-500 microg/l; r=0.999), precise (total coefficient of variation between 5.0% and 3.2% at a mean cortisol concentration of 15.1 microg/l and 269 microg/l, respectively; n=16) and specific with regard to relevant endogenous and exogenous steroids.

Derivatization procedures for gas chromatographic-mass spectrometric determination of xenobiotics in biological samples, with special attention to drugs of abuse and doping agents

The development of low cost MS detectors in recent years has promoted an important increase in the applicability of GC-MS system to analyze for the presence of foreign substances in the human body. Drugs and toxic agents are in vivo metabolized in such a way that more polar compounds are usually formed. Derivatization of these metabolites is often an unavoidable requirement for gas chromatographic analysis. Application of derivatization methods in recent years has been relevant, especially for silylation, acylation, alkylation and the formation of cyclic or diastereomeric derivatives. Given the relevance of drug of abuse testing in modern toxicology, main derivatization procedures for opiates, cocaine, cannabis, amphetamines, benzodiazepines and LSD have been reviewed. Papers describing the analyses of drugs of abuse in matrixes other than blood, such as hair or sweat, have received special attention. Advances in derivatization for sports drug testing have been particularly relevant for anabolic steroids, diuretics and corticosteroids. Among the several methodologies applied, the formation of trimethylsilyl, perfluoroacyl or methylated derivatives have proved to be both versatile and extensively used. Further advances in derivatization for GC-MS applications in clinical and forensic toxicology will depend on the one hand on the degree of further use of GC-MS for routine applications and, on the other hand, on the alternative progress made for developments in LC-MS or CE-MS. Last but not least, the appearance of comprehensive libraries in which reference spectra for different derivatives of many drugs and their metabolites are collected will have an important impact on the expansion of derivatization in GC-MS for toxicological applications.

Stable isotope dilution mass spectrometry for the simultaneous determination of cortisol, cortisone, prednisolone and prednisone in plasma

A capillary gas chromatographic-mass spectrometric method for the simultaneous determination of cortisol, cortisone, prednisolone and prednisone in human plasma is described. [1,1,19,19,19-2H5]Cortisol, [1,1,19,19,19-2H5]cortisone, [1,19,19,19-2H4]prednisolone and [1,19,19,19-2H4]prednisone were used as internal standards. Formation of the bismethylenedioxy-3-heptafluoro-n-butyryl (BMD-HFB) derivatives made possible the separation of the four corticosteroids with good gas chromatographic behaviour. The new double derivatization has been demonstrated to be of value for sensitive and selective quantification by this technique. Detection was performed by monitoring the molecular ion (M+) of the BMD-HFB derivatives for cortisone and prednisolone, the [M - 18]+ ion for cortisol, and the [M - 30]+ ion for prednisone. The method requires no complex corrections for contributions and provides good accuracy and precision.

Simultaneous determination of cortisol and cortisone in human plasma by stable-isotope dilution mass spectrometry

A method for the simultaneous determination of cortisol and cortisone in human plasma was developed using capillary gas chromatography-mass spectrometry-selected ion monitoring. [2H5]Cortisol and [2H5]cortisone were used as internal standards. Cortisol and cortisone in plasma were determined from the peak-height ratios of the [M-31] fragment ions of the methoxime-trimethylsilyl derivatives of cortisol and [2H5]cortisol (m/z 605 and 610) and of cortisone and [2H5]cortisone (m/z 531 and 536). Sensitivity, specificity, precision, accuracy and reproducibility of the method were demonstrated to be satisfactory for measuring the circulating concentrations of cortisol and cortisone.

Routine screening and quantitation of urinary corticosteroids using bench-top gas chromatography-mass-selective detection

A method was developed for the routine screening, confirmation and quantitation of corticosteroids in human urine using bench top capillary gas chromatography (GC)-mass-selective detection. The free and conjugated corticosteroid fractions were isolated by liquid-liquid partition. After evaporation to dryness under vacuum the corticosteroid residues were derivatized to form the methyloxime trimethylsilyl ether derivatives. Both GC retention data and characteristic spectral data based on authentic reference standards were used for the identification and quantitation of cortisol, cortisone, tetrahydrocortisol and tetrahydrocortisone in the ppb (ng/ml) concentration range. The method is simpler and more efficient than the other GC-mass spectrometric (MS) techniques. It is also more sensitive than the liquid chromatographic-MS method.

Preparation of multiply deuterium-labeled cortisol

Cortisol labeled with four deuterium atoms at chemically stable sites ([9,11,12,12-(2)H4]cortisol, cortisol-d4) was prepared by hydrogen-deuterium exchange and reductive deuteration reactions. After protecting the C-17 dihydroxyacetone side chain of cortisone (cortisone-BMD), hydrogen-deuterium exchange was carried out with 6.5% NaOD in MeOD, which was followed by protection of the C-3 carbonyl as the semicarbazone. Subsequent reductive deuteration at C-11 with NaBD4 followed by removal of exchangeable deuterium under the same exchange-reaction conditions in a medium of 6.5% NaOH in MeOH and deprotection afforded the desired cortisol-d4 with high isotopic content (d3, 21.2%; d4, 78.1%; d5, 0.74%). The method was applied to the synthesis of cortisol labeled with nine deuterium atoms [( 1,1,9,11,12,12,19,19,19-(2)H9]cortisol, cortisol-d9) starting from [1,1,19,19,19-(2)H5]cortisone (cortisone-d5).

Increasing thermospray response for cortisol by derivatization

The 21-hydroxyl group of cortisol was selectively acetylated under mild conditions without affecting the more sterically hindered 11 beta- and 17 alpha-hydroxyl groups. The reaction was performed with a mixture of acetic anhydride and triethylamine in acetonitrile and was complete in less than 15 min at room temperature. The thermospray mass spectrum of cortisol 21-acetate showed minimal fragmentation with the [M + H]+ ion as the base peak. High sensitivity was achieved for acetylated cortisol during selected ion monitoring, the signal-to-noise ratio being increased by a factor of about 4, compared to underivatized cortisol. The limit of detection of cortisol 21-acetate was estimated at 0.24 pmol injected, making thermospray liquid chromatography-mass spectrometry competitive with gas chromatography-mass spectrometry for the determination of cortisol in biological fluids.

Diurnal rhythm in the plasma concentration of cortisol in paediatric patients with orthostatic dysregulation

A gas chromatographic/mass spectrometric method using stable isotopically labelled cortisol as an internal standard was employed to determine patterns of episodic secretion of cortisol in three normal subjects and four paediatric patients with orthostatic dysregulation. The measurement of the plasma cortisol level at frequent time intervals revealed how the daily secretory pattern of cortisol differs in these patients and normal subjects.

Simultaneous measurements of endogenous and deuterium-labelled tracer variants of androstenedione and testosterone by capillary gas chromatography-mass spectrometry

A capillary gas chromatographic-mass spectrometric method for the simultaneous determination of androstenedione and testosterone in human plasma using [19,19,19-2H3]androstenedione and [19,19,19-2H3]testosterone as internal standards is described. For calculation of plasma androstenedione and testosterone, peak heights were measured by selected-ion monitoring of the molecular ions of the heptafluorobutyryl derivatives of androstenedione and [2H3]androstenedione (m/z 482 and 485) and of testosterone and [2H3]testosterone (m/z 680 and 683). The isotope dilution method needed no complex corrections for contributions and provides a sensitive and reliable technique with good accuracy, precision and reproducibility.

Determination of cortisol in human plasma by stable isotope dilution mass spectrometry

Cortisol selectively labelled with 2H at the 19-methyl and the C-1 position (cortisol-d5) was synthesized and used as an internal standard in stable isotope dilution mass spectrometry in order to determine cortisol in human plasma. A capillary gas chromatographic/mass spectrometric method provided a sensitive and reliable technique with good accuracy, precision and reproducibility without complex corrections for contributions by using cortisol-d5 as an internal standard. For calculation of plasma cortisol, peak areas were measured by selected ion monitoring on the characteristic fragment ions of the dimethoxime tri(trimethylsilyl) derivatives of cortisol and cortisol-d5 (m/z 605 and 610, respectively). The sensitivity of the gas chromatographic/mass spectrometric assay was 1.02 ng per injection, with a signal-to-noise ratio of about 6. The inter- and intra-assay coefficients of variation for plasma sample were 3.07% and 1.77%, respectively.