The positive ion fast atom bombardment mass spectra of ten glycoalkaloids and five related alkaloids are reported. The spectra of the glycoalkaloids are characterized by abundant [M + H]+ species and fragment ions, resulting from cleavage of the individual carbohydrate groups. Several of these ions have been observed to be diagnostic for individual glycoalkaloids and have allowed the analysis of mixtures of standards as well as crude extracts of potato peel and sprout.
Suramin and analogous diarylene ureas, which are potential compounds for the treatment of onchoceriasis (river blindness), have been investigated by negative ion fast atom bombardment mass spectrometry. Excellent abundances of the parent ions due to the sulfonate linkages were obtained, which enabled the determination of the sequences by tandem mass spectrometry experiments comparing model systems of unequivocal structures. In analogy to the fragmentation of peptides the preferential cleavages of NHCO bonds are observed, which are followed by consecutive degradations of the molecules. The formation of structure-specific fragment ions is influenced by the adjacent substituents within the phenylene moieties. The stabilities of the parent ions are documented by intense doubly charged species.
The quantification in plasma and urine of 2-dicyclopropylmethylamino-2-oxazoline (S-3341), a new antihypertensive drug is described using a sensitive gas chromatographic negative ion mass spectrometric method with ammonia as moderating gas. After a two-step extraction, derivatization is carried out with 3,5-bis(trifluoromethyl)benzoyl chloride and the abundance of the molecular ion (m/z 420) obtained is compared with that of the tetradeuterated standard (m/z 424). The low background due to the high mass and negative ion detection provides a detection limit of about 1 pg per injection. Oral administration of 1 or 2 mg S-3341 to patients gives a maximum concentration of 3.3 +/- 0.7 ng ml-1 and 7.6 +/- 2.0 ng ml-1 at 1.8 +/- 0.6 h and 1.4 +/- 0.7 h and an average elimination half-life of 6.7 h.
By use of negative ion chemical ionization and collision-activated decomposition in a triple quadrupole mass spectrometer a method has been developed for the quantification of ergotamine in human plasma at levels down to 2 pg ml-1.
The low incidence of myocardial infarction in Greenland Eskimos has been related to their traditional marine diet rich in eicosapentaenoic acid. However, whether dietary eicosapentaenoic acid is indeed transformed in man to antiaggregatory PGI3 and weakly proaggregatory TXA3 has not been clarified. In our studies we ingested either cod liver oil or mackerel both rich in eicosapentaenoic acid. Formation of TXB3, the hydrolysis product of TXA3, in platelet-rich plasma stimulated ex vivo with collagen was traced by capillary GC/EIMS. Via external standard, TXB3 formation in platelets was estimated to be 5-15% of TXB2 formation. From urine we extracted dinor metabolites of PGI according to a selective method. We utilized delta 17-2,3-dinor-6-keto-PGF1 alpha (PGI3-M) as an index of total body production of PGI3 in analogy to 2,3-dinor-6-keto-PGF1 alpha (PGI2-M), the major urinary metabolite of PGI2. We separated PGI2-M and PGI3-M as the Me, MO, Me3Si derivatives by capillary gas chromatography and identified PGI3-M by EI mass spectrometry. Excretion of PGI3-M, which was not detectable under control conditions, was 83 +/- 25 ng/24 h (SD) after ingestion of cod liver oil and 134 +/- 38 ng/24 h after mackerel ingestion, while excretion of PGI2-M was 162 +/- 52 ng/24 h and 236 +/- 32 ng/24 h, respectively. Our findings with diets rich in EPA show that it is possible in man to change in vivo the spectrum of biologically active prostanoids by nutritional means and alter it in a favourable direction.
A gas chromatographic mass spectrometric assay for (N-dicyclopropylmethyl) amino-2-oxazoline in plasma with a detection limit of 0.1 ng ml-1 was required. Various fluoroaryl derivatives of this compound (code name S3341) were synthesized and their positive ion chemical ionization and electron capture negative ion chemical ionization mass spectra recorded. While fluorobenzyl derivatives of S3341 could be made by heating with the requisite benzyl bromide and diisopropylethylamine in acetonitrile, initial efforts to synthesize corresponding fluorobenzoyl derivatives using a benzoyl chloride in dry ethyl acetate at 60 degrees C were unsuccessful. Mass spectral data indicated that only a fragment of the oxazoline ring was retained in the reaction product and that an N-(2-chloroethyl)benzamide was formed. However, when diisopropylethylamine was included in the reaction mixture, a benzoyl derivative of the complete molecule was obtained. The mechanisms of these reactions are discussed. The negative ion mass spectrum of the 3,5-bistrifluoromethylbenzoyl derivative of S3341 has a base peak at m/z 420 (the molecular ion) and, when this ion is specifically monitored, an amount of derivative equivalent to 1 pg of S3341 can be detected. This allowed the development of an assay for S3341 in plasma with a precision of 9% (SD) at 0.2 ng ml-1 and a lower limit for quantitative determination of 0.1 ng ml-1.
3,5-Dihydroxyphenylpropionic acid, 3,5-dihydroxycinnamic acid and 2,3-dihydroxycinnamic acid were detected for the first time to be components of human urine. In the course of this investigation all constitutional isomers of dihydroxy-benzoic, -phenylpropionic, -phenylacetic and -cinnamic acid were synthesized. Mass spectra and retention indices of methyl and trimethylsilyl (TMS) derivatives were determined. In contrast to many other substituted aromatic compounds the mass spectra of methyl and TMS derivatives of dihydroxy aromatic acids often allow a firm distinction to be made between constitutional isomers: TMS derivatives of aromatic acids containing two hydroxy groups located in the ortho position to each other can be recognized by ions resulting from a primary cleavage reaction mainly in the side chain or ester group, followed by loss of tetramethylsilane. In methyl derivatives of 1,2,3-trisubstituted isomers, methoxy groups are lost much more easily from the ions corresponding to the benzylic cleavage than in other isomers. Methyl derivatives of dihydroxycinnamic acids containing at least one methoxy group in the ortho position to the side chain are characterized by a fragmentation reaction, corresponding to the loss of dimethyl ether. TMS and methyl derivatives of 3,5-dihydroxy aromatic acids show unique structure-specific fragmentation reactions.
Positive and negative ion fast atom bombardment (FAB) mass spectra of the molecular ion region of calcitonin using several solution matrices produce an isotopic distribution which is indicative of a mixture of reduced and oxidized disulfide bonds. The insensitivity of the distribution to the choice of matrix and positive/negative ion mode suggest that the spectra reflect the natural abundance of reduced calcitonin in the sample, rather than an artifact of the fast atom bombardment technique.
Non-volatile nitrosamines exemplified by nitroso amino acids, -dipeptides, -oxazolidines and -thiazolidines have been analysed by moving belt liquid chromatography/mass spectrometry (LC/MS) and spectra obtained by ammonia chemical ionization. Optimal conditions such as source temperature, source pressure and belt vaporizer temperature have been established. Interface degradation involving decarboxylation and denitrosation was experienced but could be alleviated to some extent by deactivation of the polyimide belt by silylation.
The chemical reactivity of compounds related to N-hydroxy-2-aminofluorene, a class of carcinogenic arylamines, was investigated and reaction products identified by electron impact mass spectrometry. NOH(R) derivatives can be distinguished from the rearranged C(R) derivatives by means of their fragmentation patterns.
The mass spectrometric behaviour of methyl O-acetyl-β-D-xylopyranosides has been studied using electron impact, methane and ammonia chemical ionization and collisional activation mass spectrometry. Based on this study the fragmentation of the compounds studied has been described. The structures of ions occurring after elimination of ketene in the fragmentation reactions of acetylated saccharides were studied by using the MNDO semi-empirical quantum chemical method. Calculated geometrical parameters (bond lengths, bond and torsional angles), distribution of net atomic charges and the difference in heat of formation (70 kJ mol−1) between the keto and enol isomers of [C5H7O3]+ ions studied predict that the enol structure is more stable thermodynamically than its corresponding keto isomer. The electron impact and chemical ionization mass spectra do not provide complete information for determination of the location of acetyl groups in methyl O-acetylpentopyranosides. The number and position of the acetyl groups however, can be determined unambiguously from collisional activation mass spectra of the [M - OCH3]+ ions. The reproducibility of the mass spectral data, obtained by the applied mass spectral methods was evaluated by calculation of discrepancy factors. From this point of view the collisional activation method is approximately five times more precise than electron impact and 10 times more precise than chemical ionization methods.
The high bladder toxicity of the alkylating oxazaphosphorine anticancer drugs, cyclophosphamide and ifosfamide is effectively reduced by the concomitant administration of mesna (sodium 2-mercaptoethane sulphonate). The formation and rapid urinary excretion of conjugates of the activated (4-hydroxylated) oxazaphosphorine metabolites with mesna has been suggested as the pharmacological basis for the selective detoxification, but separation and identification of such metabolites in vivo have been extremely difficult due to their high polarity and chemical lability. In this study an ion-pair extraction procedure in combination with positive and negative ion fast atom bombardment mass spectrometry has been developed which enabled the identification and quantification of the conjugation products of activated oxazaphosphorine metabolites with mesna in urine. The conjugates extracted as the tetra-n-butylammonium salts are directly identified by their characteristic positive molecular ion adducts and fragment ions, and the corresponding abundant molecular anions. The pattern of molecular and fragment ion formation was established by comparison of the fast atom bombardment mass spectra of synthetic cyclophosphamide-mesna conjugates with various organic and inorganic counter ions. The ifosfamide-4-(2-thioethylsulphonate) (ifosfamide-mesna) conjugate was identified as a metabolite in the urine of rats, and in patients after administration of the combination, ifosfamide + mesna. By means of a two-step extraction and with the use of suitable analogues as internal standards, procedures for the quantification of parent oxazaphosphorine and of oxazaphosphorine-mesna conjugates by negative ion fast atom bombardment mass spectrometry have been developed, and first examples for the determination of excretion kinetics are described.
Girard's reagents were used to derivatize ketosteroids and conjugates for analysis by positive ion fast atom bombardment mass spectrometry. Spectra contain an abundant ion corresponding to the cation (C+) of the newly formed ionic derivative (C+A-) and relatively little fragmentation. With derivatization, detection of ketosteroids at a concentration of 1 microgram microliter-1 in glycerol was straightforward. Such derivatization schemes may prove useful in the analysis of ketosteroids in complex biological mixtures.
A sensitive and highly specific method based on capillary column gas chromatography/mass spectrometry has been developed for the detection of 19-nortestosterone (17 beta-hydroxy-4-estren-3-one) metabolites in urine. After intramuscular administration of 19-nortestosterone decanoate to man, urine samples were collected during several days and treated with Helix pomatia digestive juice. The free steroids were extracted and converted into O-methyl-oxime-trimethylsilyl or the trimethylsilyl ether derivatives and analysed by capillary column gas chromatography/mass spectrometry (GC/MS). Three isomeric metabolites were detected and identified as 3 alpha-hydroxy-5 alpha-extran-17-one (19-norandrosterone), 3 alpha-hydroxy-5 beta-estran-17-one (19-noretiocholanolone) and 3 beta-hydroxy-5 alpha-estran-17-one (19-norepiandrosterone). Packed column GC/MS was also employed in the selected ion monitoring mode for the specific detection of 19-norandrosterone, the most abundant urinary metabolite of 19-nortestosterone. These gas chromatographic/mass spectrometric methods are highly specific tests which can be used on a routine basis for the confirmation of 19-nortestosterone administration to athletes as well as for therapeutic monitoring following administration of the drug.
The antifungal ketoconazole affects testosterone synthesis in dispersed rat testicular cells. In the presence of ketoconazole an accumulation of 17 alpha,20 alpha-dihydroxyprogesterone has been observed. This steroid was isolated from the testis of Wistar rats after a [4-14C]progesterone incorporation in the presence of ketoconazole. Its identification was achieved from the gas chromatographic/mass spectrometric analysis of the isolated radioactive fraction. A chemical derivatization of the fraction with butylboronic acid followed by mass spectrometric analysis confirmed the presence of 17 alpha,20 alpha-dihydroxyprogesterone.
Quinoxalinol t-butyldimethylsilyl ethers were prepared from three branched-chain and from two aliphatic unbranched 2-keto acids. The electron impact (EI) mass spectra display pronounced [M-57]+ ions. With 39-51% of total ion current contained within them, sensitivity is greater than on chemical ionization (CI) mass spectrometry of O-trimethylsilyl derivatives. Mass spectra and chromatographic behaviour of these novel keto acid derivatives are discussed and preliminary quantitative data from rat muscle are given.
The increasing number of applications for fast atom bombardment (FAB) mass spectrometry has seen a corresponding increase in the use of different matrix compounds. This review discusses briefly the use of matrix compounds in general and the use of cosolvents and/or additives with glycerol that assist in producing superior FAB mass spectra than when glycerol is used on its own. The main part of the review deals with alternative matrix compounds to glycerol including thioglycerol, polyethyleneglycols, triethanolamine, diamylphenol, crown ethers and various miscellaneous matrix compounds.
Organic compounds were extracted by a modified continuous liquid-liquid extractor. The extract was analysed by computerized high-resolution gas chromatography/mass spectrometry (GC/MS). The results of the analysis indicated the presence of many halogenated compounds, such as halogenated methoxybenzenes, dichlorobenzene, benzene hexachloride, methylated triclosan and oxadiazon. Alkylphenol ethoxylates, which are known as degradation products of poly(oxyethylene)alkylphenyl ether, were also found in the extract.
When sampled by laser irradiation from a suitable matrix, cationized sugars can be desorbed in far higher yields for longer periods than in experiments which do not employ a matrix. Daughter spectra reveal that Li+ reacts differently from the other alkali ions in that it can catalyse ring opening; collision-induced dissociation then causes successive CC cleavage reactions. Selectivity is also exhibited by the substrate; some isomers yield much more intense ion currents with the alkali metals than do others. These findings should contribute to a wider use of laser desorption, including selective examination of mixtures for particular types of compounds, as well as detailed structural studies on individual substances.
