Enantioselective quantitative analysis of amphetamine in human plasma by liquid chromatography/high-resolution mass spectrometry.

A method for the quantitative enantioselective analysis of amphetamine in human plasma by LC-HRMS is presented. High-resolution detection, alone and in combination with targeted MS/MS, was validated and compared to a highly sensitive GC-NICI-Method. Derivatization with (S)-N-(heptafluorobutyryl)-prolyl chloride was accomplished to yield derivatives suitable for enantioselective analysis of amphetamine on a nonchiral reversed phase column with MS-compatible mobile phase. Equal analytical performance was observed for the methods presented and the GC-NICI-MS method. A dynamic range of 4,000 was found for the established calibration curves. A fivefold deuterated analogue of both enantiomeres was used as an internal standard. Full validation data are given to demonstrate the usefulness of the assay, including specificity, linearity, accuracy and precision, autosampler stability, matrix effect, and prospective analytical batch size accuracy. The method has been successfully applied to pharmacokinetic profiling of the drug after oral application.

Quantitative determination of amphetamine in plasma using negative ion chemical ionization GC-MS of o-(pentafluorobenzyl-oxycarbonyl)-2,3,4,5-tetrafluorobenzoyl derivatives.

Quantitative determination of amphetamine in plasma by the use of a novel electrophoric derivatization reagent, o-(pentafluorobenzyloxycarbonyl)-2,3,4,5-tetrafluorobenzoyl chloride is described. Amphetamine can be quantitatively measured down to 49 pg/mL plasma using only 250 µL of sample due to the extraordinary sensitivity of the derivatives under negative ion chemical ionization MS. Plasma samples were made alkaline with carbonate buffer and treated with n-hexane and reagent solution for 20 min, which, after concentration was measured by negative ion chemical ionization GC-MS. The method is rapid as extraction and derivatization occur in one single step. [(2)H(5)]-Amphetamine was used as an internal standard. Validation data are given to demonstrate the usefulness of the assay, including specificity, linearity, accuracy and precision, benchtop stability, freeze-thaw stability, autosampler stability, aliquot analysis, and prospective analytical batch size accuracy.

Quantitative method for determination of amphetamine in plasma using negative ion chemical ionisation GC-MS of o-(pentafluorobenzyloxycarbonyl)-benzoyl derivatives.

The use of a novel electrophoric derivatisation reagent, o-(pentafluorobenzyloxycarbonyl)-benzoyl chloride is described for the quantitative determination of amphetamine in plasma. Amphetamine can be quantitatively measured down to 49 pg/mL plasma using only 250 µL of sample due to the extraordinary sensitivity of the derivatives under negative ion chemical ionisation mass spectrometry. Plasma samples were made alkaline with carbonate buffer and treated with n-hexane and reagent solution for 20 min, which, after concentration was measured by negative ion chemical ionisation gas chromatography-mass spectrometry. The method is rapid as extraction and derivatisation occur in one single step. [(2)H(5)]-Amphetamine was used as an internal standard. Validation data are given to demonstrate the usefulness of the assay, including specificity, linearity, accuracy and precision, benchtop stability, freeze-thaw stability, autosampler stability, aliquot analysis and prospective analytical batch size accuracy.

Bis-pentafluorobenzyl derivatives of N-acetyl-L-methionine and N-acetyl-L-selenomethionine for the quantitative determination in human plasma by gas chromatography-negative ion chemical ionisation mass spectrometry.

Targeted anti-cancer combination therapy with infusion of N-acetyl-L-methionine (NALM) and N-acetyl-L-selenomethionine (NASeLM) shows promising results in cancer treatment. Selenium has been recognised as a valuable additive in cancer therapeutics due to its ability to minimise side effects of chemotherapy and its role in cancer prevention and therapy. Due to the promising results of this new therapeutic approach evaluation of pharmacokinetic data for NALM and NASeLM is of ultimate importance. We have therefore elaborated a method for the quantitative measurement of these compounds in human plasma based on GC-negative ion chemical ionisation-MS. The derivatisation sequence elaborated can be regarded as a novel strategy for the chemical modification of delicate sulphur- and selenium-containing compounds, and underlines the enhanced reactivity of selenium-analogues of sulphur-containing amino acids. The target compounds were extracted from plasma with ethyl acetate and converted to the S/Se-pentafluorobenzyl-homocysteine pentafluorobenzyl ester derivative. Reaction conditions were optimised for derivative yield. Calibration graphs were established in the range of 2.938-481.105 ng/0.5 mL plasma (NALM) and 0.233-59.543 ng/0.5 mL plasma (NASeLM). Accuracy, precision and stability data were elaborated. The method was applied to pharmacokinetic profiling of the compounds after infusion into human volunteers.

(S)-(-)-N-(pentafluorobenzylcarbamoyl)prolyl chloride: a chiral derivatisation reagent designed for gas chromatography/negative ion chemical ionisation mass spectrometry of amino compounds.

RATIONALE: The synthesis of a novel chiral derivatisation reagent, (S)-(-)-N-(pentafluorobenzylcarbamoyl)prolyl chloride is described which is preferably useful for negative-ion chemical ionisation mass spectrometry. METHODS: Preparation of the reagent followed a general strategy used to prepare enantioselective reagents based on the N-substitution of L-proline. Pentafluorobenzyl chloroformate smoothly reacted with L-proline to give the desired derivatisation reagent after conversion into the acyl chloride. The product was sufficiently pure to be used in the following steps without any additional purification. RESULTS: The reagent was tested against selected chiral and non-chiral analytical targets. Chromatographic enantioseparation was at least equal to the commonly used (S)-(-)-N-(heptafluorobutyryl)prolyl derivatives. The derivatives exhibit excellent mass spectral properties under negative ion chemical ionisation, i.e. reduced fragmentation and thus high ion current for the targeted m/z during analysis. With electron ionisation, the fragmentation that occurs is mainly directed by the introduced group. Enantioseparation with gas chromatography/negative-ion chemical ionisation mass spectrometry of the derivatives was demonstrated for the enantiomers of amphetamine, α-aminocaprylic acid methyl ester and threo-methylphenidate. CONCLUSIONS: The new derivatisation reagent shows highly improved mass spectral properties for negative-ion chemical ionisation mass spectrometry and is thus suitable for sensitive chiral detection of amino compounds. The reagent extends the applicability of dissociative resonance electron capture using pentafluorobenzyl derivatives to chiral analysis.

Gas chromatography-negative ion chemical ionisation mass spectrometry using o-(pentafluorobenzyloxycarbonyl)-2,3,4,5-tetrafluorobenzoyl derivatives for the quantitative determination of methylphenidate in human plasma.

A novel electrophoric derivatisation procedure using o-(pentafluorobenzyloxycarbonyl)-2,3,4,5-tetrafluorobenzoyl chloride for the quantitative determination of methylphenidate in human plasma is described. The drug can be quantitatively measured down to 0.006 pg/mL plasma due to the extraordinary sensitivity of the derivatives under negative ion chemical ionisation mass spectrometry. Plasma samples were made alkaline with carbonate buffer and treated with extraction solvent (n-hexane) and reagent solution for 15 min, which, after concentration was measured by GC-NICI-MS. The method is rapid as extraction and derivatisation occur in one single step. A stable isotope labelled internal standard was used. Validation data are given to demonstrate the usefulness of the assay, including selectivity, linearity, accuracy and precision, autosampler stability, aliquot analysis, robustness, and prospective analytical batch size accuracy. The method has been successfully applied to pharmacokinetic profiling of the drug after oral administration.

Quantitative determination of methylphenidate in plasma by gas chromatography negative ion chemical ionisation mass spectrometry using o-(pentafluorobenzyloxycarbonyl)-benzoyl derivatives.

The use of a novel electrophoric derivatisation reagent, o-(pentafluorobenzyloxycarbonyl)-benzoyl chloride, for the quantitative determination of methylphenidate in plasma is described. The drug can be quantitatively measured down to 72 pg/mL plasma using only 250 µL of sample due to the extraordinary sensitivity of the derivatives under negative ion chemical ionisation mass spectrometry. Plasma samples were made alkaline with carbonate buffer and treated with extraction solvent n-hexane and reagent solution for 30 min, which, after concentration, was measured by GC-NICI-MS. The method is rapid as extraction and derivatisation occur in one single step. A stable isotope-labelled internal standard was used and its synthesis described. Full validation data are given to demonstrate the usefulness of the assay, including specificity, linearity, accuracy and precision, long-term stability, short-term stability, freeze-thaw stability, stock solution stability, autosampler stability, aliquot analysis, robustness, matrix effect, and prospective analytical batch size accuracy. The method has been successfully applied to pharmacokinetic profiling of the drug after oral application.

o-(Pentafluorobenzyloxycarbonyl)benzoyl chloride: a novel electrophoric derivatisation reagent for amino compounds designed for negative ion chemical ionisation mass spectrometry.

The synthesis of a novel electrophoric derivatisation reagent, o-(pentafluorobenzyloxycarbonyl)benzoyl chloride, is described. The reagent was tested against selected primary and secondary amino compounds as analytical targets. The derivatives exhibit excellent mass spectral properties under negative ion chemical ionisation (NICI), i.e. reduced fragmentation and thus high ion current for the targeted m/z during analysis. Since the reagent bears a pentafluorobenzyl ester group, resulting mass NICI mass spectra were expectedly dominated by dissociative resonance electron capture typically observed with these compounds. The reagent is suitable for detecting volatile primary and secondary amines with high sensitivity. Background is reduced by a shift in detected m/z and retention time, as demonstrated for the analysis of the drug methylphenidate from human plasma.

Simultaneous quantitative determination of alpha-ketoglutaric acid and 5-hydroxymethylfurfural in human plasma by gas chromatography-mass spectrometry.

Alpha-ketoglutaric acid (alpha-KG) and 5-hydroxymethylfurfural (5-HMF) are currently under investigation as promising cancer cell damaging agents. A method for the simultaneous quantitative determination of alpha-KG and 5-HMF in human plasma was established for screening these compounds in human plasma. Plasma samples were directly treated with O-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine hydrochloride to form the corresponding oximes, thus facilitating subsequent liquid-liquid extraction. After formation of the trimethylsilyl ethers, samples were analyzed by gas chromatography with electron ionization mass spectrometry. Stable isotope labeled standards were used, the preparation of (13)C(6)-5-HMF is described. Limits of quantitation were set to 0.938 microg/mL for alpha-KG and 0.156 microg/mL for 5-HMF. Inter-day accuracy was < or = 93.7% (alpha-KG) and < or = 92.8% (5-HMF). Inter-day precision was < or = 6.0% (alpha-KG) and < or = 4.6% (5-HMF). The method has been successfully applied to pharmacokinetic profiling of the compounds after intravenous application.