An LC-MS-MS method for the comprehensive analysis of cocaine and cocaine metabolites in meconium.

A sensitive, precise, and accurate liquid chromatography-mass spectrometry (LC-MS-MS) method was developed to quantitate cocaine and cocaine metabolites, which were simultaneously extracted from suspected drug-positive meconium samples using solid-phase extraction. The ability to analyze cocaine and multiple cocaine metabolites in meconium makes this method a powerful tool for the study of cocaine exposure and metabolism in neonates. Of 22 samples, only 1 did not show the presence of cocaine or any metabolite of cocaine. The identified metabolites varied both qualitatively and quantitatively between samples. Ecgonine appears to hold the most promise as a diagnostic marker compound for neonatal cocaine exposure as this metabolite was present in 21 of 21 of the positive samples tested, and at a relatively high median concentration. However, a core group of eight metabolites (present in at least 20 of 21 positive samples) was identified that appears to possess the greatest utility for determining cocaine exposure. Finally, the use of this method for assessment of the magnitude of fetal cocaine exposure was demonstrated.

Mass spectrometric detectors for samples separated by planar electrophoresis.

Mass spectrometric detection for samples separated by planar chromatography (high-performance thin-layer chromatography and planar electrophoresis) has evolved over the past 10 years from concept to feasibility and to commercial availability. This review concentrates on the interface between planar electrophoresis and mass spectrometry. Although hardware aspects of the interface have been developed and refined over the past few years, and there are impressive demonstrations of feasibility, we are only beginning to exploit new methods in sample storage, preparation and reaction in conjunction with planar chromatographic separation, and new uses of complex multi-dimensional imaging data.

Liquid secondary ion mass spectra of 2-iminothiolane derivatives.

The derivatization reaction of 2-iminothiolane with several small peptides has been studied using liquid secondary ion mass spectrometry. The 2-iminothiolane reagent reacts with side-chain amino groups and with N-terminal amines in peptides. Addition of 2-iminothiolane introduces a free sulfhydryl group and an immonium group into the peptide. The signal intensity for the derivative of a small peptide is approximately the same as that of the [M + H]+ ion of the same underivatized peptide from a glycerol solution. The pattern of dissociation observed in the product ion MS/MS spectrum is altered to reflect the derivative. The sulfhydryl group introduced via 2-iminothiolane reaction further allows for the incorporation of maleimide fluorophores into the peptide for sensitive detection by ultraviolet/visible absorption or fluorescence. This work also reports a previously unrecognized recyclization side-reaction that involves loss of the immonium group during the derivatization reaction.

Calibration Point for Electron Ionization MS / MS spectra measured with multiquadrupole mass spectrometers.

A protocol for establishing standard instrument conditions for measurement of product ion MS/MS spectra from parent ions produced by electron ionization is presented. Within this protocol, the ion at m/z 231 (C5F9 (+)) from perfluorokerosene or perfluorotributylamine is selected as the parent ion and subjected to collision-induced dissociation. The relative intensities of product ions at m/z 69, 131, and 181 are monitored as a function of collision energy while keeping the target gas pressure constant within the range of 10(-4)-10(-6) torr (measured), or a beam attenuation of approximately 30-70%. The collision energy at which the ion intensities for product ions at m/z 69 and 181 are equal is defined as the calibration point at that collision gas pressure; the intensity of the ion at m/z 131 is very close to this value as well. Electron ionization MS/MS spectra taken at the calibration point using two different multiquadrupole instruments show good reproducibility for several test compounds. The high degree of similarity may aid in the establishment of a MS/MS spectral library.

Beam-induced reaction between meta-nitrobenzyl alcohol and dipyridocyanine dyes in liquid-secondary-ion mass spectrometry.

Analyses of cationic dipyridocyanine dyes by liquid-secondary-ion mass spectrometry in a liquid matrix of meta-nitrobenzyl alcohol (rnNBA) provide evidence for beam-induced addition reactions between the sample molecule (C) and the mNBA solvent. The ionic products of these addition reactions formally correspond to [C+mNBA-O2](+), Ic+mNBA-O2-H](+), and [C+mNBA-O2-2H](+). Initial loss of H from the adduct ion extends the conjugation of the adduct into the mNBA ring structure, whereas the final loss of hydrogen is thought to be promulgated by the formation of a benzylic radical stabilized through resonance with the π-electron system of the nitrobenzyl alcohol. Alternatively, two hydrogens may be lost from the alcohol functionality to form an aldehyde.

Rapid extraction and structural characterization of biomolecules in agarose gels by laser desorption Fourier transform mass spectrometry.

A method originally developed for the extraction of biomolecules from agarose gel slices has been utilized as a rapid means of isolating biological compounds from gels for subsequent structural characterization by matrix-assisted last desorption-ionization Fourier transform mass spectrometry (MALDI/FTMS). This "freeze-squeeze" extraction method involves pressure extrusion of fluid from frozen gel slices and provides near 50% recovery of analyte in less than 5 min. Experiments were directed at examining the recovery efficiency of the extraction method using 14C-labeled adenosine monophosphate and investigating the effect of high buffer concentrations on the laser desorption mass spectra. When coupled with this extraction technique, MALDI/FTMS can be used to detect and identify biomolecules at the low picomole level in agarose gel slices. The accurate mass measurements and MS/MS capabilities of the FTMS were exploited to provide detailed structural information at the isomeric level for oligonucleotides electrophoresed into agarose gels.

Thin-layer chromatography/liquid secondary ion mass spectrometry in the determination of major bile salts in dog bile.

Positive and negative ion liquid-state secondary-ion mass spectrometry (LSIMS) was applied to several bile acids and bile salts and their spectra were measured directly from the surface of silica gel thin-layer chromatograms. Such spectra were identical to the LSIMS spectra of the pure compound at the same concentration. Three-dimensional ion images were obtained of a model mixture of cholic, chenodeoxycholic and lithocholic acids in both the positive and negative ion modes. A sample of dog bile was prepared, and the bile acids extracted from it were separated by high-performance TLC; TLC/LSIMS spectra were obtained for sodium taurocholate and sodium taurochenodeoxycholate/taurodeoxycholate, the predominant bile salts present. Quantitative estimates of the analytes were obtained by monitoring the ion intensity for the sample spot and a standard spot that had been developed in parallel on the same TLC plate. The concentration of sodium taurocholate in the bile of this particular dog was found to be 38 mg/ml.

Imaging analysis and selected sequence monitoring of small peptides using planar chromatography/secondary ion mass spectrometry.

Mixtures of enkephalins and bradykinins contained on silica gel thin-layer chromatograms were imaged by secondary ion mass spectrometry. Spatial profiles of the sample distribution in the chromatographic plane were determined using a precision manipulator that moves the sample into and out of the primary beam generated in a liquid metal gallium source. For instance, spatial profiles are conveniently measured by monitoring the protonated molecule [M + H]+ of each compound or, in a selected-sequence monitoring experiment, by monitoring a sequence ion common to the members of each peptide group. The latter experiment is useful for quick location and identification of a class of peptides separated by planar chromatography, including thin-layer chromatography and electrophoresis.

Derivatization of ketosteroids for fast atom bombardment mass spectrometry.

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.

Chemical modification of nucleic acids. Methylation of calf thymus DNA investigated by mass spectrometry and liquid chromatography.

Mass spectrometry provides an extremely sensitive method for the identification and quantification of modified nucleosides and hence for determining chemical modifications of nucleic acids. When mass spectrometry is used in conjunction with a new high-performance liquid chromatographic system capable of separating 15 methylated and naturally occurring nucleosides, this allows the quantification of products of in vitro DNA methylation. With synthetic (2H3)methyl-labeled methylnucleosides as internal references, the distribution of methylated products formed when calf thymus DNA was reacted with N-methyl-N-nitrosourea(MeNU) was determined. Five modified products, 1-methyldeoxyadenosine(m1dA), 3-methyldeoxycytidine(m3dC), 7-methyldeoxyguanosine(m7dG), 3-methylthymidine(m3T) and O4-methylthymidine(m4T) were detected and the relative distributions were measured. The ability of mass spectrometry/mass spectrometry (tandem mass spectrometry) to increase specificity and sensitivity in this determination is demonstrated and its application to in vivo studies is suggested.

Mass spectrometry: analytical capabilities and potentials.

The mass range of mass spectrometers has been extended by almost an order of magnitude in the past decade, ionization procedures have been introduced which allow ionic, nonvolatile compounds to be examined, and new capabilities have been achieved through the successful integration of separation and analysis techniques. In combination with other techniques, mass spectrometry has been used in biological and environmental research to characterize constituents of mixtures, including those present in trace amounts; in metabolic profiling, where high throughput and large dynamic range are important; and in protein structure determinations. Measurements of stable isotope abundances by mass spectrometry have been used in enzymology, studies of photosynthesis, and carbon dating. Outside the area of chemical analysis, mass spectrometry has been used to study gas-phase acidities and basicities and to study organic reaction mechanisms in the gas phase. Trends in mass spectrometry include multidimensional experiments, use of ionization methods, direct analysis without extensive sample preparation, and the development of advanced instrumentation including an ion trap and an inductively coupled plasma mass spectrometer. It is likely that mass spectrometry will come to be much more widely used and that data will increasingly be other than conventional mass spectra.

Mass spectrometry of large, fragile, and involatile molecules.

Desorption ionization makes it possible to obtain mass spectra of molecules whose vaporization by heating may lead to thermal degradation. Several methods are in use, but in general desorption is achieved by particle or photon bombardment of the sample and the mass spectra obtained by different methods are fundamentally similar. Desorption ionization techniques have been used to obtain mass spectra of biomolecules, including peptides, antibiotics, and oligosaccharides, for which normal mass spectral methods have been of limited power. Several examples are given of recent applications of these new techniques, and prospects for their further evolution are discussed.

Negative ion mass spectra of some polychlorinated 2-phenoxyphenols.

Polychlorinated 2-phenoxyphenols were studied by negative ion mass spectrometry. Common to almost all of the methane enhanced negative ion mass spectra were (M-1)-, (M-36-)-., (M-37)-, (M-72)-., and chorinated quinoxide ions. The (M-36)-. ion does not apparently form in a mechanism analogous to the thermal or photochemical ring closure of these compounds to form the chlorinated dioxins. The chlorinated quinoxide ion reflects the number of chlorines on the ring with hydroxy substituent. Collision-induced dissociation mass-analyzed ion kinetic energy spectra (CID-MIKES) from different isomers were qualitatively different in both the normal and charge reversed mode of operation. Comparison of these spectra with those from other classes of polychlorinated aromatic hydrocarbons such as the dioxins or the furans may reveal a common negative ion gas phase chemistry.

Methane-oxygen enhanced negative ion mass spectra of polychlorinated diphenyl ethers.

Methane-oxygen enhanced negative ion mass spectra of 15 chlorinated diphenyl ethers contained some combination of [M-]-., [M-1]-, [M-19]-, [M-36]-, [M-55]-, and [M+35]- anions. The relative abundances of these ions are related to the chlorine substitution pattern. Similar ions appear in the negative ion spectra of polychlorinated anisoles. The study of known isomers of polychlorinated model compounds extends the utility of the negative ion method in the analysis of polychlorinated aromatics such as polychlorinated biphenyls, dioxins and furans. The spectra were shown to be very dependent on the temperature of the ion source; a temperature change of 25 degrees C was shown to have pronounced effects. Spectral variation with temperature has implications for computer library searches, ultimate sensitivity limits and analysis in the presence of interfering isobaric ions.