Chemical study of triterpenoid resinous materials in archaeological findings by means of direct exposure electron ionisation mass spectrometry and gas chromatography/mass spectrometry

A systematic study of standard triterpenes (alpha-amyrine, oleanolic acid, betulin, lupeol, betulinic acid and lupenone) and of raw resinous materials (frankincense resin, mastic resin and birch bark pitch) was performed using direct exposure electron ionisation mass spectrometry (DE-MS) and gas chromatography/mass spectrometry (GC/MS). DE-MS provides a mass spectral fingerprint of organic materials in a few minutes which highlights the compounds that are the main components in the sample. The application of principal component analysis (PCA) on DE-MS data in the mass ranges m/z 181-260 and m/z 331-500, corresponding to the fragmentation of triterpenoid molecules, enabled us to distinguish between different triterpenoid materials such as mastic resin, frankincense resin and birch bark pitch, and to graphically plot the resinous substances in three separate clusters, retaining 89% of the total variance. GC/MS analysis of the same materials has permitted us to elucidate in detail the molecular composition and to identify minor components and species that act as markers of the degradation undergone by the materials. The paper also reports the results for the organic residues contained in an Egyptian censer (5th-7th century AD) which was recovered in the excavation of the Necropolis of Antinoe (Egypt), and for the hafting material found on a Palaeolithic tool recovered at the site of Campitello (Arezzo, Tuscany), dating back to the Mid-Pleistocene period. Although DE-MS was found to be a fast analytical tool, it failed to give any information on the presence of less abundant compounds when applied to mixtures of different materials: only mastic resin was found in the residues from the Roman censer, whereas GC/MS analysis identified the presence of a vegetable oil from Brassicaceae seeds and Pinaceae resin. Birch bark pitch as a pure material was identified in the sample from the Palaeolithic flint flake using both procedures.     

液相色谱-串联质谱法测定虾夷扇贝和长牡蛎中软骨藻酸的残留

建立了液相色谱-串联质谱测定虾夷扇贝和长牡蛎中贝类毒素软骨藻酸残留的检测方法。样品经50%甲醇提取,LC-SAX柱净化,3mL0.1mol/L甲酸溶液洗脱,电喷雾离子源(ESI),在正离子、多反应监测方式(MRM)模式下进行定性与定量,定性离子对为m/z 311.98/265.91,m/z 311.98/247.9,m/z 311.98/192.91,以m/z 311.98/265.91为定量离子对,外标法定量。结果表明,方法的检测限为0.01μg/g,定量限为0.02μg/g。在0.02~10μg/mL范围内线性相关系数为0.9999。当添加软骨藻酸质量分数为20~1000 ng/g时,虾夷扇贝样品中软骨藻酸的平均回收率为81.3%~105.4%,RSD为3.9%~8.9%(n=6);长牡蛎样品中软骨藻酸的平均回收率为83.5%~106.6%,RSD为4.6%~6.4%(n=6)。方法满足对贝类产品中软骨藻酸残留的测定。     

Determination of acetyltrimoprostil and its metabolite trimoprostil in human or dog plasma by gas chromatography-negative-ion chemical ionization mass spectrometry

A sensitive and specific procedure is described for the determination of the antisecretory prostaglandin acetyltrimoprostil and its metabolite trimoprostil in human or dog plasma using gas chromatography--negative-ion chemical ionization mass spectrometry (GC--NICI-MS). Trideuterated analogues of both compounds are added to plasma as the internal standards. The plasma is extracted at pH 7.3 with benzene--dichloromethane (9:1), and the residue of the organic extract is reacted at room temperature with pentafluorobenzyl bromide in the presence of 18-crown-6-ether and potassium acetate. The derivatives are reconstituted in heptane, and appropriate aliquots are analyzed by GC--NICI-MS with selected-ion monitoring of the intense (M--C6F5CH2)- fragment ions of acetyltrimoprostil (m/z 419), trimoprostil (m/z 377), and their respective trideuterated analogues (m/z 422 and m/z 380, respectively). Quantitation of an experimental plasma sample is based on a comparison of the m/z 419 versus m/z 422 and m/z 377 versus m/z 380 ion ratios in each sample to that obtained from the analysis of drug-free plasma fortified with various amounts of both protio compounds, and a fixed amount of each trideuterated internal standard. The limit of quantitation of the assay for human plasma is 0.2 ng ml-1 with mean relative standard deviations at this concentration of 15.5% and 9.7% for acetyltrimoprostil and trimoprostil, respectively.     

Probing the molecular weight distributions of non-boiling petroleum fractions by Ag+ electrospray ionization mass spectrometry

This work explores the possibility of Ag+ electrospray ionization mass spectrometry (ESI-MS) to determine the molecular weight distributions of non-boiling petroleum fractions. Information about the molecular weight distributions is needed for fundamental studies on the nature of heavy crude oils and bitumens and for the development of novel recovery and processing methods. The method does not depend on thermal processes for the introduction of the fractions into the gas phase of the mass spectrometer, which is a considerable advantage over most other ionization methods. The Ag+ electrospray mass spectra of the fractions analyzed by using a toluene/methanol/cyclohexane (60:28:12%) solvent system display bimodal distributions in the ranges m/z approximately 300 to approximately 3000 and m/z 3000 to approximately 20,000. The abundances of the high molecular weight peak distributions can be reduced by in-source collisional activation experiments. Comparisons with the results obtained for model heteroatom-containing compounds (molecular weight < 600 Da) and high molecular weight polystyrene standards (up to one million Da) indicate that the majority of the structures in the saturate, naphthenoaromatic and polar aromatic fractions, and a significant portion of the asphaltenes, are small molecules. However, a considerable portion of the asphaltenes and some portion of the other fractions contain high molecular weight structures bound by covalent or strong non-covalent bonds. The results obtained by the Ag+ ESI method in this study for the saturate, aromatic, and polar fractions in a bitumen are in qualitative agreement with published molecular weight average results obtained for Cold Lake bitumen fractions analyzed by conventional gel permeation chromatography and field desorption mass spectrometry. Further work is needed to study the nature of the bonds and the interactions of the molecules in the asphaltene fractions by Ag+ ESI-MS.     

Characterisation of nicotine and related compounds using electrospray ionisation with ion trap mass spectrometry and with quadrupole time-of-flight mass spectrometry and their detection by liquid chromatography/electrospray ionisation mass spectrometry

Electrospray ionisation ion trap mass spectrometry (ESI-MS(n)) has been used to study the fragmentation patterns of nicotine and nine of its related compounds. From this study certain characteristic fragmentations are apparent with generally the pyrrolidine or piperidine ring being subject to chemical modifications. The structures of the product ions proposed for the ESI-MS(n) study have been supported by results from electrospray ionisation quadrupole time-of-flight mass spectrometry (ESI-QTOF-MS). Compounds with pyrrolidine and piperidine rings that possess an unsubstituted N atom have been shown to lose NH(3) at the MS(2) stage. Those compounds with N-methyl groups lose CH(3)NH(2) at the MS(2) stage. The loss of NH(3) or CH(3)NH(2) leaves the corresponding rings opened and this is followed by ring closure at the pyridine-2 carbon atom. Mono-N-oxides fragment in a similar way but the di-N-oxide can also fragment by cleavage of the bond between the pyridine and pyrrolidine rings. Cotinine also can undergo cleavage of this bond between the rings.This data therefore provides useful information on how substituents and the nature of the non-pyridine ring can affect the fragmentation patterns of nicotine and its related compounds. This information can be used in the characterisation of these compounds by liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) which results in the separation of nicotine and its related compounds with limits of detection (LODs) ranging from 15 to 105 ng/mL. The use of LC/ESI-MS to study nicotine-containing samples resulted in the simultaneous and unambiguous identification of seven of the compounds discussed in this paper: cotinine identified at retention time 12.5 min (with its [M+H](+) ion at m/z 177), nornicotine 16.0 min (m/z 149), anatabine 18.0 min (m/z 161), myosmine 18.5 min (m/z 147), anabasine 20.4 min (m/z 163), nicotine 22.2 min (m/z 163), and nicotyrine 31.4 min (m/z 159). For quality control of nicotine replacement therapy products, these nicotine impurities can be readily identified and determined at levels up to 0.3% for single impurities and up to 1.0% for total impurities.     

Mass spectrometric characterization of toremifene metabolites in human urine by liquid chromatography-tandem mass spectrometry with different scan modes

The metabolism and excretion of toremifene were investigated in one healthy male volunteer after a single oral administration of 120 mg toremifene citrate. Different liquid chromatographic/tandem mass spectrometric (LC/MS/MS) scanning techniques were carried out for the characterization of the metabolites in human urine for doping control purposes. The potential characteristic fragmentation pathways of toremifene and its major metabolites were presented. An approach for the metabolism study of toremifene and its analogs by liquid chromatography-tandem mass spectrometry was established. Five different LC/MS/MS scanning methods based on precursor ion scan (precursor ion scan of m/z 72.2, 58.2, 44.2, 45.2, 88.2 relative to five metabolic pathways) in positive ion mode were assessed to recognize the metabolites. Based on product ion scan and precursor ion scan techniques, the metabolites were proposed to be identified as 4-hydroxy-toremifene (m/z 422.4), 4'-hydroxy-toremifene (m/z 422.4), α-hydroxy-toremifene (m/z 422.4), 3,4-dihydroxy-toremifene (m/z 404.2), toremifene acid (m/z 402.2), 3-hydroxy-4-methoxy-toremifene (m/z 456.2), dihydroxy-dehydro-toremifene (m/z 440.2), 3,4-dihydroxy-toremifene (m/z 438.2), N-demethyl-4-hydroxy-toremifene (m/z 408.3), N-demethyl-3-hydroxy-4-methoxy-toremifene (m/z 438.3). In addition, a new metabolite with a protonated molecule at m/z 390.3 was detected in all urine samples. The compound was identified by LC/MS/MS as N-demethyl-4,4'-dihydroxy-tamoxifene. The results indicated that 3,4-dihydroxy-toremifene (m/z 404.2), toremifene acid (m/z 402.2) and N-demethyl-4,4'-dihydroxy-tamoxifene (m/z 390.3) were major metabolites in human urine.     

液相色谱-串联质谱检测蔬菜和茶叶中吡虫啉的残留量

介绍了利用液相色谱-串联质谱（LC-MS/MS）快速、准确地测定蔬菜、茶叶产品中吡虫啉残留量的方法。前处理方法为用乙腈提取,再用弗罗里硅土和活性炭混合柱净化。用多反应监测技术确定吡虫啉的两对离子(m/z 256.0/209.3,m/z 256.0/175.2)为定性离子对,m/z 209.3为定量离子。方法的定量限为0.01 mg/kg,线性范围为0.01～0.5 mg/L,加标回收率为76%～90%,相对标准偏差（RSD）为7.4%～11.0%。     

Improved mass accuracy for higher mass peptides by using SWIFT excitation for MALDI-FTICR mass spectrometry

Stepwise-external calibration has previously been shown to produce sub part-per-million (ppm) mass accuracy for the MALDI-FTICR/MS analyses of peptides up to m/z 2500. The present work extends these results to ions up to m/z 4000. Mass measurement errors for ions of higher mass-to-charge are larger than for ions below m/z 2500 when using conventional chirp excitation to detect ions. Mass accuracy obtained by using stored waveform inverse Fourier transform (SWIFT) excitation was evaluated and compared with chirp excitation. Analysis of measurement errors reveals that SWIFT excitation provides smaller deviations from the calibration equation and better mass accuracy than chirp excitation for a wide mass range and for widely varying ion populations.     

Characterization of Acacia mangium polyflavonoid tannins by MALDI-TOF mass spectrometry and CP-MAS C NMR

The MALDI-TOF mass spectrometry (MS) and solid state CP-MAS ¹³C Nuclear Magnetic Resonance (NMR) spectroscopic technique were introduced to characterize Acacia mangium tannin (condensed tannins). The MALDI-TOF MS illustrated a series of peaks corresponding to oligomers of condensed tannins of up to 11 flavonoid units (3200 Da). A. mangium condensed tannins were found to consist predominantly of prorobinetinidin combined with profisetinidin and prodelphinidin. Both the MALDI-TOF mass spectra and the solid state CP-MAS ¹³C NMR indicated that the A. mangium tannins obtained from Kudat, had an almost completely linear structure; In addition, Lembah Beringin, consist of “angular” polymer structure; and Tawau, has included “twice-angular” polymer structures present in oligomers type of up to 7 flavonoid units. The high degree of polymerization of linear, angular type, twice-angular structures and longer oligomer (3200 Da) chains have not been observed in previous studies of condensed tannins. The spectra also indicated that A. mangium tannins are more heavily branched and have higher degree of polymerization (>7.0) compared to commercial mimosa (A. mearnsii) tannin (4.9). Because tannins are phenolic, it was expected that they can be used to replace phenol-formaldehyde (PF) adhesives.     

Corrosion inhibition performance of tannins for mild steel in hydrochloric acid solution

Research on Chemical Intermediates - The corrosion inhibition behavior of commercial hydrolysable tannin (tara tannin), condensed tannin (black wattle tannin) and complex tannin (bayberry tannin)...     

Mass spectrometric investigation of gallium and zirconium complexes with octaethylporphyrin and tetraphenylporphyrin

Gallium and zirconium octaethylporphyrin (OEP) and tetraphenylporphyrin (TPP) were examined by electrospray ionization (ESI) mass spectrometry. All systems were prepared in dichloromethane with addition of a stabilizing lipophilic anionic agent, sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaTFPB). In the solutions examined both monomeric and dimeric metalloporphyrins were observed. In the gallium-OEP mass spectrum the ion registered at m/z 601 was attributed to monomeric [Ga(OEP)](+) and that at m/z 1219 to the dimeric form, [[Ga(OEP)](2)OH](+). Peaks appearing in the ESI mass spectra of zirconium systems were substantially less intense, probably owing to the relatively low stability of complexes of this metal caused by its different geometry preferences. The most abundant monomeric zirconium-OEP complexes were [[Zr(OEP)OH]](+) (m/z 639) and [Zr(OEP)Cl](+) (m/z 657), and dimeric [[Zr(OEP)OH](2)](2+) (m/z 639). Analogous species were observed in the Zr(TPP) system: monomeric [[Zr(OEP)OH]](+) (m/z 719) and [Zr(TPP)Cl](+) (m/z 737) and dimeric [[Zr(TPP)OH](2)](2+) (m/z 719). In both cases series of other dimers, e.g. [[Zr(OEP)](2)O(2)H](+) (m/z 1277), [[Zr(OEP)OH](2)Cl](+) (m/z 1313), [Zr(TPP)(2)O(2)H](+), (m/z 1437), [[Zr(TPP)OH](2)OH](+) (m/z 1455) and [[Zr(TPP)OH](2)Cl](+) (m/z 1473), appeared. The results obtained confirmed the hypothesis concerning the formation of dimeric metalloporphyrins in solutions containing stabilizing lipophilic anions. It also allowed us to explain the super-Nernstian slopes of the calibration curves towards primary anions of ion-selective electrodes with membranes containing the examined metalloporphyrins.     

乳制品中那他霉素的超高效液相色谱-串联质谱法快速测定

建立了超高效液相色谱-电喷雾串联质谱(UPLC-MS/MS)快速检测乳制品中那他霉素的方法。样品用甲醇提取,以甲醇-水为流动相经反相色谱柱分离后,采用多反应监测(MRM)负离子模式检测,定性离子对为m/z663.6/421.1和m/z663.6/439.1,其中m/z663.6/421.1用于外标法定量。空白样品及其加标实验结果表明:特征离子相对强度比值稳定,无基质干扰,结合保留时间可实现准确的定性定量;方法定量下限为50.0μg/kg;乳制品加标量为50~500μg/kg时,平均回收率为80%~91%,相对标准偏差(n=6)为2.7%~5.2%。方法简单、灵敏、稳定,可满足乳制品中那他霉素的快速检测与确证需要。     

In situ analysis of agrochemical residues on fruit using ambient ionization on a handheld mass spectrometer

We describe a rapid in situ method for detecting agrochemicals on the surface or in the tissue of fruit using a portable mass spectrometer equipped with an ambient ionization source. Two such ionization methods, low temperature plasma (LTP) and paper spray (PS), were employed in experiments performed at a local grocery store. LTP was used to detect diphenylamine (DPA) directly from the skin of apples in the store and those treated after harvest with DPA were recognized by MS and MS/MS. These data therefore allowed ready distinction between organic and non-organic apples. DPA was also found within the internal tissue of purchased apples and its distribution was mapped using LTP. Similarly, thiabendazole residues were detected on the skin of treated oranges in a grocery store experiment in which paper spray was performed by wiping the orange surface with a moist commercial lens wipe and then applying a high voltage to ionize the chemicals directly from the wipe. The handheld mass spectrometer used in these measurements is capable of performing several stages of tandem mass spectrometry (up to MS(5)); the compounds on the fruit were identified by their MS/MS fragmentation patterns. Protonated DPA (m/z 170) produced a characteristic MS(2) fragment ion at m/z 92, while thiabendazole was identified by MS(3) using precursor to fragment ion transitions m/z 202 →m/z 175 →m/z 131. These particular examples exemplify the power of in situ analysis of complex samples using ambient ionization and handheld mass spectrometers.     

Development of a high-Performance MALDI-TOF mass spectrometer utilizing a spiral ion trajectory

A novel MALDI-TOF mass spectrometer that utilizes a spiral ion trajectory was developed. In this mass spectrometer, the ions sequentially passed through four toroidal electrostatic sectors and revolved along a figure-eight-shaped orbit on a particular projection plane. Each toroidal electrostatic sector had eight stories, and during multiple revolutions, the ion trajectory shifted perpendicular to the projection plane in every cycle, thereby generating a spiral trajectory. The flight path length of one cycle was 2.1 m; therefore, when the ions completed eight cycles, the total flight path length was 17 m. By adopting an ion optical system that had a flight path length five times longer than that in the commonly used reflectron ion optical system, the mass dependence on the mass resolving power was reduced, while improving the mass accuracy of the mass measurements. The basic performance of the system was tested by using standard peptides or the tryptic digest of bovine serum albumin. A mass resolving power of 80,000 (full width at half maximum) was achieved at m/z = 2564 (ACTH18-39). An improved mass accuracy less than 2 ppm was realized over a wide m/z range of 500 to 3000 by correction using one or two internal standard substances.     

高效液相色谱-串联质谱检测牛奶中的甲状腺素

建立了高效液相色谱-串联质谱(HPLC-MS/MS)检测牛奶中甲状腺素3,3′,5,5′-四碘-L-甲腺原氨酸(T4), 3,3′,5-三碘-L-甲腺原氨酸(T3)和3,3′,5′-三碘-L-甲腺原氨酸(rT3)的方法。样品用乙腈提取,离心,上清液经氨水碱化和Cleanert PAX固相萃取小柱净化,在Zorbax Eclipse XDB-C18 (150 mm×2.1 mm, 3.5 μm)色谱柱上以0.1%(v/v)乙酸水溶液和甲醇为流动相等度洗脱分离,以电喷雾正离子(ESI+)模式电离,多反应监测(MRM)模式质谱检测,内标法定量。结果表明,甲状腺素的检出限(LOD)不大于0.03 ng/g,定量限(LOQ)不大于0.1 ng/g;在考察的浓度范围内线性关系良好(r2＞ 0.998);回收率为80.61%～101.7%,相对标准偏差(RSD)为1.48%～9.70%。室温下样品溶液中的甲状腺素保持稳定。对5个牛奶样品的测定结果显示,T3含量为0.59～1.30 ng/g, RSD为2.06%～7.70%; T4和rT3未检出。该方法具有样品处理简单,灵敏度高,重现性好,定性和定量结果可靠等特点,为牛奶中甲状腺素的测定和相关质量安全评价提供了可靠手段。     

Matrix-assisted laser desorption using a fast-atom bombardment ion source and a magnetic mass spectrometer.

A conventional fast-atom bombardment (FAB) ion source was used to achieve matrix-assisted laser desorption (MALD) in a high-mass, double-focusing, magnetic mass spectrometer. The pulsed ion signals generated by irradiation of a mixture of sample and matrix (2,5-dihydroxybenzoic acid) with either a XeF excimer laser (353 nm) or a nitrogen laser (337 nm) were recorded with a focal-plane detector. A resolution (full-width at half maximum) of 4500 was achieved at m/z 1347.7 (the peptide substance P), 2500 for CsI cluster ions at m/z 10,005.7, and 1250 for the isotope cluster of the small protein cytochrome c (horse) [M+H]+ = m/z 12,360 (average). Sensitivity is demonstrated with 11 fmol of substance P. A survey scan is taken to locate the m/z of the sample molecular ion. The segment that contains the sample can then be integrated for a longer time to produce a better signal-to-noise ratio. In addition to higher sensitivity and lower matrix interference, the advantage of MALD over FAB is the former's lower susceptibility to the presence of salts, and competition between hydrophobic and hydrophilic components of a mixture. This feature is demonstrated by the complete MALD spectrum of a crude partial tryptic digest of sperm-whale apomyoglobin, containing 24 peptides, representing the entire sequence of this protein.     

固相萃取-气相色谱/质谱法同时测定化妆品中的邻苯二甲酸酯和对羟基苯甲酸酯

采用超声协助甲醇提取、固相萃取净化、气相色谱/选择离子质谱联用法,同时测定化妆品中8种邻苯二甲酸酯和4种对羟基苯甲酸酯。该方法线性范围广、重现性好、快速简便、干扰小。样品的加标回收率为80%～100%;含量检测的相对标准偏差小于10%;方法的检出限为0.1~5.0 μg/kg。用该方法对15种实际样品中的12种残留物进行定量检测,结果表明除了一种样品中不含待测物外,其余样品均检测到3~7种待测物。其中以对羟基苯甲酸甲酯、对羟基苯甲酸丙酯、邻苯二甲酸丙酯、邻苯二甲酸环己酯和邻苯二甲酸乙基庚基酯为主。     

Analysis of commercial vegetable tanning agents by reversed-phase liquid chromatography-electrospray ionization-tandem mass spectrometry and its application to wastewater

Commercial vegetable tanning agents that are derived from plants and consist of condensed or hydrolyzable tannins were analyzed by electrospray ionization–tandem mass spectrometry (ESI–MS/MS) to identify their major constituents and to study their collision-induced dissociation. In the condensed tannin wattle a series of proanthocyanidin dimers to tetramers was identified together with the flavonoid monomers catechin and gallocatechin. The composition of the hydrolyzable tannin chestnut was more heterogenous. Besides the monomers ellagic and gallic acid a variety of gallotannins were detected, namely mono-, di- and trigalloylglucose, and a variety of ellagitannins. Reversed-phase HPLC–ESI–MS/MS methods were developed to detect condensed and hydrolyzable tannins in tannery wastewaters by multiple reaction monitoring (MRM). The methods proved suitable even for highly loaded wastewaters. However, the detected amount of wattle tanning agent in spent retanning baths was about two orders of magnitude below the amount used for the retanning. This suggests that the condensed tannins of polyphenolic structure are rapidly transformed during the tanning process to yet unknown products.     

Gas chromatography/isotope-ratio mass spectrometry method for high-precision position-dependent 15N and 18O measurements of atmospheric nitrous oxide

We describe an automated gas chromatography/isotope-ratio mass spectrometry (GC/IRMS) method for the determination of the (18)O and position-resolved (15)N content of nitrous oxide at natural isotope abundance. The position information is obtained from successive measurement of the isotopic composition of the N(2)O(+) ion at m/z 44, 45, 46 and the NO(+) fragment ion at m/z 30, 31. The fragment ion analysis is complicated by a non-linearity in the mass spectrometer that has to be taken into account. Evaluation of the absolute peak areas allows for a simultaneous determination of the N(2)O mixing ratio for atmospheric samples. Samples with mixing ratios ranging from a few nmol/mol up to the percent level can be analyzed using different sample inlet systems. The high concentration inlet system provides an easy and quick method to carry out various diagnostic tests, in particular to perform realistic linearity tests. A gas chromatographic set-up with a split column and a backflush possibility improves analytical precision and excludes interferences by substances with long retention times from preceding runs. We also describe a new open split interface that uses only a single transfer capillary to the mass spectrometer for sample and reference gas.     

Accurate mass filtering of ion chromatograms for metabolite identification using a unit mass resolution liquid chromatography/mass spectrometry system

Acceleration of liquid chromatography/mass spectrometric (LC/MS) analysis for metabolite identification critically relies on effective data processing since the rate of data acquisition is much faster than the rate of data mining. The rapid and accurate identification of metabolite peaks from complex LC/MS data is a key component to speeding up the process. Current approaches routinely use selected ion chromatograms that can suffer severely from matrix effects. This paper describes a new method to automatically extract and filter metabolite-related information from LC/MS data obtained at unit mass resolution in the presence of complex biological matrices. This approach is illustrated by LC/MS analysis of the metabolites of verapamil from a rat microsome incubation spiked with biological matrix (bile). MS data were acquired in profile mode on a unit mass resolution triple-quadrupole instrument, externally calibrated using a unique procedure that corrects for both mass axis and mass spectral peak shape to facilitate metabolite identification with high mass accuracy. Through the double-filtering effects of accurate mass and isotope profile, conventional extracted ion chromatograms corresponding to the parent drug (verapamil at m/z 455), demethylated verapamil (m/z 441), and dealkylated verapamil (m/z 291), that contained substantial false-positive peaks, were simplified into chromatograms that are substantially free from matrix interferences. These filtered chromatograms approach what would have been obtained by using a radioactivity detector to detect radio-labeled metabolites of interest.