Tandem Mass Spectrometry Imaging Enables High Definition for Mapping Lipids in Tissues

Mass spectrometry imaging (MSI) of lipids in biological tissues is useful for correlating molecular distribution with pathological results, which could provide useful information for both biological research and disease diagnosis. It is well understood that the lipidome could not be clearly deciphered without tandem mass spectrometry analysis, but this is challenging to achieve in MSI due to the limitation in sample amount at each image spot. Here we develop a multiplexed MS² imaging (MS²I) method that can provide MS² images for 10 lipid species or more for each sampling spot, providing spatial structural lipidomic information. Coupling with on-tissue photochemical derivatization, imaging of 20 phospholipid C=C location isomers is also realized, showing enhanced molecular images with high definition in structure for mouse brain and human liver cancer tissue sections. Spatially mapped t-distributed stochastic neighbor embedding has also been adopted to visualize the tumor margin with enhancement by structural lipidomic information.     

Fast-atom bombardment tandem mass spectrometry of [13C]arachidonic acid labeled phospholipid molecular species

A method employing stable isotope labeling and fast-atom bombardment (FAB) tandem mass spectrometry has been developed to directly assess events of biosynthesis and metabolism of arachidonic acid containing phospholipid molecular species by cells carried in culture. Mast cells, cultured with [¹³C]linoleic acid, converted this precursor into arachidonic acid which was then incorporated into cellular phospholipids. Over a 24 hour period, the extent of label enrichment in each arachidonate-containing phospholipid molecular species was monitored by using negative FAB ionization with selected reaction monitoring. Specific incorporation of [¹³C₁₇] labeled arachidonate was determined from the ratio of the carboxylate anions at m/z 320 and 303, which correspond to [¹³C₁₇]arachidonate and unlabeled arachidonate, respectively, produced by collision-induced dissociation of each specific molecular anion. The use of [¹³C]linoleic acid as a precursor of arachidonic acid avoids the problem of changing the endogenous pool size by directly adding labeled arachidonic acid. Measurement of the [¹³C₁₇]label also avoids interferences from endogenous isobaric fatty acids that are naturally present at low levels.     

Global characterization of the photosynthetic glycerolipids from a marine diatom Stephanodiscus sp. by ultra performance liquid chromatography coupled with electrospray ionization-quadrupole-time of flight mass spectrometry

The photosynthetic glycerolipids composition of algae is crucial for structural and physiological aspects. In this work, a comprehensive characterization of the photosynthetic glycerolipids of the diatom Stephanodiscus sp. was carried out by ultra performance liquid chromatography-electrospray ionization-quadrupole-time of flight mass spectrometry (UPLC-ESI-Q-TOF MS). By use of the MS^E data collection mode, the Q-TOF instrument offered a very viable alternative to triple quadrupoles for precursor ion scanning of photosynthetic glycerolipids and had the advantage of high efficiency, selectivity, sensitivity and mass accuracy. Characteristic fragment ions were utilized to identify the structures and acyl compositions of photosynthetic glycerolipids. Comparing the abundance of fragment ions, it was possible to determine the position of the sn-glycerol-bound fatty acyl chains. As a result, four classes of photosynthetic glycerolipid in the extract of Stephanodiscus sp. were unambiguously identified, including 16 monogalactosyldiacylglycerols (MGDGs), 9 digalactosyldiacylglycerols (DGDGs), 23 sulfoquinovosyldiacylglycerols (SQDGs) and 8 phosphatidylglycerols (PGs). As far as our knowledge, this is the first report on global identification of photosynthetic glycerolipids, including lipid classes, fatty acyl composition within lipids and the location of fatty acids in lipids (sn-1 vs. sn-2), in the extract of marine microalgae by UPLC-ESI-Q-TOF MS directly.     

Structural studies on archaeal phytanyl-ether lipids isolated from membranes of extreme halophiles by linear ion-trap multiple-stage tandem mass spectrometry with electrospray ionization

The structures of archaeal glycerophospholipids and glycolipids are unique in that they consist of phytanyl substituents ether linked to the glycerol backbone, imparting stability to the molecules. In this contribution, we described multiple-stage linear ion-trap combined with high resolution mass spectrometry toward structural characterization of this lipid family desorbed as lithiated adduct ions or as the [M−H]⁻ and [M−2H]²⁻ ions by ESI. MSⁿ on various forms of the lithiated adduct ions yielded rich structurally informative ions leading to complete structure identification of this lipid family, including the location of the methyl branches of the phytanyl chain. By contrast, structural information deriving from MSⁿ on the [M−H]⁻ and [M−2H]²⁻ ions is not complete. The fragmentation pathways in an ion-trap, including unusual internal loss of glycerol moiety and internal loss of hexose found for this lipid family were proposed. This mass spectrometric approach provides a simple tool to facilitate confident characterization of this unique lipid family.     

Mapping and sequencing of cardiolipins from Geobacillus stearothermophilus NRS 2004/3a by positive and negative ion nanoESI-QTOF-MS and MS/MS

In the course of systematic studies on surface layer (S-layer) glycoproteins of bacilli, the chloroform/methanol extract from whole cells of Geobacillus stearothermophilus NRS 2004/3a has been submitted to MS analysis. Glucosylated cardiolipins were found as minor components of the total lipid and phospholipid mixture by de novo identification. After purification of the crude extract using a combined column chromatography/2D TLC protocol, structural investigations of components in the lipid fraction by high resolution ESI-QTOF MS analysis provided evidence about homologous molecules attributable to the cardiolipin species containing a glycosylated backbone, and about a diversity of ester-linked fatty acid substituents. In comparative studies by positive and negative ion nanoESI-QTOF-CID-MS, maps of cardiolipin molecular ions were obtained, followed by MS/MS of the most abundant species, to provide structural details of D-glucopyranosylcardiolipin and the fatty acid substituent patterns. Experiments of the parent ion scan type revealed the presence of fatty acid moieties as isobaric combinations, represented in single molecular ion species.     

Precise and global identification of phospholipid molecular species by an Orbitrap mass spectrometer and automated search engine Lipid Search

In the present research, we have established a new lipidomics approach for the comprehensive and precise identification of molecular species in a crude lipid mixture using a LTQ Orbitrap mass spectrometer (MS) and reverse-phase liquid chromatography (RPLC) combination with our newly developed lipid search engine “Lipid Search”. LTQ Orbitrap provides high mass accuracy MS spectra by Fourier-transform (FT) mass spectrometer mode and can perform rapid MSⁿ by ion trap (IT) mass spectrometer mode. In this study, the negative ion mode was selected to detect fragment ions from phospholipids, such as fatty acid anions, by MS2 or MS3. We selected the specific detection approach by neutral loss survey-dependent MS3, for the identification of molecular species of phosphatidylcholine, sphingomyelin and phosphatidylserine. Identification of molecular species was performed by using both the high mass accuracy of the mass spectrometric data obtained from FT mode and structural data obtained from fragments in IT mode. Some alkylacyl and alkenylacyl species have the same m/z value as molecular-related ions and fragment ions, thus, direct acid hydrolysis analysis was performed to identify alkylacyl and alkenylacyl species, and then the RPLC–LTQ Orbitrap method was applied. As a result, 290 species from mouse liver and 248 species from mouse brain were identified within six different classes of phospholipid, only those in manually detected and confirmed. Most of all manually detected mass peaks were also automatically detected by “Lipid Search”. Adding to differences in molecular species in different classes of phospholipids, many characteristic differences in molecular species were detected in mouse liver and brain. More variable number of saturated and monounsaturated fatty acid-containing molecular species were detected in mouse brain than liver.     

Use of liquid chromatography/tandem mass spectrometric molecular fingerprinting for the rapid structural identification of pharmaceutical impurities

Use of liquid chromatography/tandem mass spectrometric (LC/MSⁿ) molecular fingerprinting is systematically demonstrated as a very effective tool for rapid structural elucidation of pharmaceutical impurities through a case study in which three isomers of betamethasone sodium phosphate (BSP) were rapidly identified as degradants formed due to the D‐homoannular ring expansion of the steroid core structure of BSP in the solid state. The rapid structural elucidation of these degradants was achieved by matching or closely matching the UV profiles, molecular weights, and more importantly the fragmentation patterns obtained from the LC/MSⁿ (n = 1 to 3) analysis of their enzyme‐catalyzed hydrolytic products, respectively, with those of a D‐homoannular isomer of betamethasone available in our LC/MSⁿ molecular fingerprint database. This strategy of using LC/MSⁿ molecular fingerprinting to obtain high‐confidence structures of unknown species is then validated by structure verification through one‐ (1D) and two‐dimensional (2D) nuclear magnetic resonance (NMR) experiments. Copyright © 2009 John Wiley & Sons, Ltd.     

Structural characterization of flavonoid glycosides from leaves of wheat (Triticum aestivum L.) using LC/MS/MS profiling of the target compounds

The aim of this study was to present integrated mass spectrometric methods for the structural characterization and identification of flavonoid glycoconjugates. During the liquid chromatography/mass spectrometry analyses, TriVersa NanoMate chip‐based system with nanoelectrospray ionization and fraction collection was combined to a quadrupole time‐of‐flight mass spectrometer. In the extract samples prepared from green leaves of wheat plantlets, 41 flavonoid derivatives were recognized. Part of the target natural products had the full structure being characterized after the registration of mass spectra, where m/z values for protonated [M + H]⁺ and deprotonated molecules [M ? H]^? were annotated. MS² and pseudo‐MS³ experiments were performed for [M + H]⁺ or [M ? H]^? and aglycone ions (Y₀^+/?‐type), respectively. It should be underlined that pseudo‐MS³ mass spectra were registered for aglycone product ions in the mass spectra of O‐glycosides present in the extract samples. In many cases, only tentative structural identification of aglycones was possible, mainly because of the presence of numerous C‐monoglycoside or C‐diglycoside in the samples. Acylation of the sugar moiety and/or methylation of the aglycone in the flavonoid glycosides under study was observed. The existence of isobaric and/or isomeric compounds was demonstrated in the extract studied. The collision‐induced dissociation mass spectra registered for C,O‐diglycosides and C,C‐diglycosides did not permit to draw complete structural conclusions about the compounds studied. For the investigated class of natural products, unambiguous classification of sugar moieties linked to the aglycones from the recorded mass spectra was not possible. Registration of the positive and negative ion mass spectra did not lead to the precise conclusion about the glycosylation position at C‐6 or C‐8, and O‐4′ or O‐7 atoms. It was possible, on the basis of the collected MS² spectra, to differentiate between O‐glycosides and C‐glycosides present in the samples analyzed. Copyright © 2013 John Wiley & Sons, Ltd.     

Molecular species analysis of arachidonate containing glycerophosphocholines by tandem mass spectrometry

Carboxylate anions arising from collision-induced dissociation (CID) of the [M - 15]^- ion produced by fast atom bombardment (FAB) of glycerophosphocholine (GPCho) were previously shown to be produced in an abundance ratio of 1:3 for the carboxylic acids esterified at sn - 1 and sn - 2, respectively. This observation has been confirmed in a series of 13 synthetic GPCho molecular species. A good correlation was found between the isomeric purity of GPCho molecular species as determined by negative-ion FAB/CID analysis and the isomeric purity of the sn - 2 fatty acid using a phospholipase A₂ assay. Negative-ion FAB mass spectra of several 1-0-alkyl-2-acyl-GPCho molecular species were found to be similar to those of diacyl GPCho. However, the cm spectra from the major high-mass ions are different from those of the diacyl species in that the [M - 15]^- ion yields only one carboxylate anion and the [M - 86]^- undergoes a neutral loss of the sn - 2 carboxylic acid as a major decomposition product. These results suggest several rules useful for structural characterization of GPCho molecular species by negative-ion tandem mass spectrometry (MS/MS): (1) For diacyl species, the mass of the two carboxyl anions plus the mass of the GPeho backbone (minus a methyl group) must correspond to the mass of the [M - 15] anion; (2) for diacyl species there is a carboxylate anion ratio approximately 1:3 for the substituents at sn - 1 and sn - 2; and (3) for alkylether species, only one fatty acyl group is present, and the difference between the [M - 15] ion and the GPCho backbone (minus methyl) plus the fatty acyl group at sn - 2 corresponds to an alkylether substituent. (4) Assignment of ether-linked molecular species can be made from the [M - 86]^- ion, which has a strong neutral loss of the sn - 2 fatty acid. Analysis of GPCho isolated from human neutrophils by total lipid extraction and normal-phase HPLC was carried out by negative-ion FABand MS/MS. The major arachidonate-eontaining molecular species, which comprise only 5% of total GPCho, were identified by using precursor ion scans for the arachidonate anion, m/ z 303. Decomposition of identified. precursor ions permitted the assignment of those molecular species of GPCho that contain arachidonate at sn - 2 and identification of the substituent at the sn - 1 position. These results were compared to previously identified molecular species from human neutrophils. Several minor arachidonate-containing molecular species were tentatively identified.     

Multiple‐stage linear ion‐trap with high resolution mass spectrometry towards complete structural characterization of phosphatidylethanolamines containing cyclopropane fatty acyl chain in Leishmania infantum

The structures of phosphatidylethanolamine (PE) in Leishmania infantum are unique in that they consist of a rare cyclopropane fatty acid (CFA) containing PE subfamily, including CFA‐containing plasmalogen PE species. In this contribution, we applied multiple‐stage linear ion‐trap combined with high‐resolution mass spectrometry to define the structures of PEs that were desorbed as [M – H]^? and [M – H + 2Li]⁺ ions by ESI, respectively. The structural information arising from MSⁿ on both the molecular species are complimentary, permitting complete determination of PE structures, including the identities of the fatty acid substituents and their location on the glycerol backbone, more importantly, the positions of the double bond(s) and of the cyclopropane chain of the fatty acid chain, directing to the realization of the CFA biosynthesis pathways that were reported previously. We also uncovered the presence of a minor dimethyl‐PE subclass that has not been previously reported in L. infantum. This LIT MSⁿ mass spectrometric approach led to unambiguous identification of PE molecules including many isomers in complex mixture that would otherwise be very difficult to define using other analytical approaches. Copyright © 2014 John Wiley & Sons, Ltd.     

Identification of the unknown transformation products derived from lincomycin using LC‐HRMS technique

In this paper, a comprehensive study of the fate of an antibiotic, lincomycin, in the aquatic environment is presented. High‐resolution mass spectrometry was employed to assess the evolution of the process over time. Formation of intermediate compounds was followed by high performance liquid chromatography‐high resolution mass spectrometry (LC‐HRMS); accurate mass‐to‐charge ratios of parent ions were reported with inaccuracy below 1 mmu, which guarantee the correct assignment of their molecular formula in all cases, while their MS² and MS³ spectra showed several structural‐diagnostic ions that allowed to characterize the different transformation products (TPs) and to discriminate the isobaric species. The simulation of phototransformation occurring in the aquatic environment and the identification of biotic and abiotic TPs of the pharmaceutical compound were carried out in different experimental conditions: dark experiments, homogeneous photolysis and heterogeneous photocatalysis using titanium dioxide, in order to recreate conditions similar to those found in the environment. Twenty‐one main species were identified afterwards lincomycin transformation. Several isomeric species were formed and characterized by analyzing MS and MSⁿ spectra and by comparison with parent molecule fragmentation pathways. The major transformation process for lincomycin is hydroxylation either at N‐alkyl side chain or at the pyrrolidine moiety. In addition, oxidation/reduction, demethylation or cleavage of pyranose ring occurs. Based on this information and additional assessment of profiles over time of formation/disappearance of each species, it was possible to recognize the transformation pathways followed by the drug. Copyright © 2012 John Wiley & Sons, Ltd.     

Determination of ent-kaurene in subcutaneous fat of Iberian pigs by gas chromatography multi-stage mass spectrometry with the aim to differentiate between intensive and extensive fattening systems

This work presents a gas chromatography multi-stage mass spectrometry (GC-MS³) method for the determination of ent-kaurene in subcutaneous fat of Iberian pig, present in adipose tissue of animals due to pasture ingestion (extensive fattening system). The method comprises a saponification and a liquid-liquid extraction of the unsaponifiable fraction, followed by an isolation of the hydrocarbon fraction by high performance liquid chromatography (HPLC) and analysis by GC-MS³ (ion trap) with electronic ionization. The GC-MS³ analysis allows the isolation and characterization of specific fragments from the original (MS¹) molecular structure, and particularly, those fragments originated from the precursor ion (m/z = 229) characteristic of ent-kaurene. The MS/MS product fragment m/z = 213 is used as a further precursor fragment giving rise to a MS³ spectrum specific for ent-kaurene. The limit of detection of the MS³ technique is lower than 0.2 μg kg⁻¹ and a linear regression has been found between 0.2 and 112 μg kg⁻¹. This method is applicable for the determination of the fattening system of the Iberian pig.     

Studies on the aconitine-type alkaloids in the roots of Aconitum Carmichaeli Debx. by HPLC/ESIMS/MS

Studies of aconitine-type alkaloids in the Chinese herb Aconitum Carmichaeli were performed by HPLC/ESIMS/MSⁿ and FTICR/ESIMS in positive ion mode. The characteristic fragmentation pathways in the MSⁿ spectra were summarized based on previously published research literature and further study. According to the fragmentation pathways of mass spectrometry, results from the analysis of standard compounds and reports from literature, 111 compounds were identified or deduced in a total of 117 found compounds in A. Carmichaeli. In the 11 monoester-diterpenoid alkaloids (MDA), 10 diesterditerpenoid alkaloids (DDA) and 81 lipo-alkaloids, the novel alkaloids including 1 MDA, 2 DDA and 48 lipo-alkaloids were detected. In addition, 1 DDA, 7 lipo-alkaloids and 2 alkaloids with small molecular weights that possess C19-norditerpenoid skeleton were reported in A. Carmichaeli for the first time.     

Determination of phosphatidylethanolamine molecular species in various food matrices by liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS2)

A liquid chromatographic–electrospray ionization–tandem mass spectrometric (LC–ESI–MS²) method has been developed for determination of the molecular species of phosphatidylethanolamine (PE) in four food matrices (soy, egg yolk, ox liver, and krill oil). The extraction and purification method consisted of a pressurized liquid extraction procedure for total lipid (TL) extraction, purification of phospholipids (PLs) by adsorption on a silica gel column, and separation of PL classes by semi-preparative normal-phase HPLC. Separation and identification of PE molecular species were performed by reversed-phase HPLC coupled with electrospray ionization tandem mass spectrometry (ESI–MS²). Methanol containing 5 mmol L⁻¹ ammonium formate was used as the mobile phase. A variety of PE molecular species were detected in the four food matrices. (C16:0–C18:2)PE, (C18:2–C18:2)PE, and (C16:0–C18:1)PE were the major PE molecular species in soy. Egg yolk PE contained (C16:0–C18:1)PE, (C18:0–C18:1)PE, (C18:0–C18:2)PE, and (C16:0–C18:2)PE as the major molecular species. Ox liver PE was rich in the species (C18:0–C18:1)PE, (C18:0–C20:4)PE, and (C18:0–C18:2)PE. Finally, krill oil which was particularly rich in (C16:0(alkyl)–C22:6(acyl))plasmanylethanolamine (PakE), (C16:0–C22:6)PE, and (C16:0–C20:5)PE, seemed to be an interesting potential source for supplementation of food with eicosapentaenoic acid and docosahexaenoic acid.     

Analysis of aminophospholipid molecular species by methyl-beta-cyclodextrin modified micellar electrokinetic capillary chromatography with laser-induced fluorescence detection

Micellar electrokinetic capillary chromatography (MEKC) with laser-induced fluorescence detection is used for the analysis of three classes of aminophospholipids: phosphatidylethanolamine (PE), phosphatidylserine (PS), and lysophosphatidylethanolamine (LPE) molecular species. 3-(2-Furoyl) quinoline-2-carboxaldehyde (FQ), a fluorogenic dye, was employed for labeling of these phospholipids. The FQ-labeled lipid species were then separated by sodium deoxycholate MEKC modified with methyl-beta-cyclodextrin. Baseline resolution of each class of phospholipids was achieved within 7 min. The migration time in each class increased with the carbon number of their side aliphatic chain. Separation efficiencies of approximately 3x10(5) plates were observed for most of these species. Concentration detection limits (3 sigma) were from 10(-9) to 10(-10) M for PE and LPE species and from 10(-8) to 10(-9) M for PS species. The relative standard deviations for migration time and peak area were less than 0.9% and 4.5%, respectively, for seven PE species. This method was applied to the separation of PE isolated from HT29 human colon cancer cells and roughly 30 PE species were resolved.     

Mathematical modeling of the graft reaction between polystyrene and polyethylene

Polystyrene (PS) and polyethylene (PE) are two major components of household plastic waste whose blends are immiscible. Recycling them together is an attractive option that requires a compatibilization process to improve the blend mechanical properties. If a PE/PS copolymer is added or formed in situ, it may act as compatibilizer. The structure and molecular properties of this copolymer are key factors to assure its effectivity as a compatibilizer. In this work, we study the graft copolymerization reaction between polystyrene and polyethylene using the catalytic system composed of AlCl₃ and styrene. We develop a model of this process which considers that PE/PS grafting and PS degradation occur simultaneously. We propose a kinetic mechanism for the whole process and apply the method of moments to solve the mass balance equations. The model is able to calculate average molecular weights as well as the amount of grafted PS. It accurately describes the available experimental data, constituting a valuable tool for simulation and optimization purposes.     

Automated Lipid A Structure Assignment from Hierarchical Tandem Mass Spectrometry Data

Infusion-based electrospray ionization (ESI) coupled to multiple-stage tandem mass spectrometry (MS ⁿ ) is a standard methodology for investigating lipid A structural diversity (Shaffer et al. J. Am. Soc. Mass. Spectrom. 18(6), 1080–1092, 2007). Annotation of these MS ⁿ spectra, however, has remained a manual, expert-driven process. In order to keep up with the data acquisition rates of modern instruments, we devised a computational method to annotate lipid A MS ⁿ spectra rapidly and automatically, which we refer to as hierarchical tandem mass spectrometry (HiTMS) algorithm. As a first-pass tool, HiTMS aids expert interpretation of lipid A MS ⁿ data by providing the analyst with a set of candidate structures that may then be confirmed or rejected. HiTMS deciphers the signature ions (e.g., A-, Y-, and Z-type ions) and neutral losses of MS ⁿ spectra using a species-specific library based on general prior structural knowledge of the given lipid A species under investigation. Candidates are selected by calculating the correlation between theoretical and acquired MS ⁿ spectra. At a false discovery rate of less than 0.01, HiTMS correctly assigned 85% of the structures in a library of 133 manually annotated Francisella tularensis subspecies novicida lipid A structures. Additionally, HiTMS correctly assigned 85% of the structures in a smaller library of lipid A species from Yersinia pestis demonstrating that it may be used across species.     

Imaging of small molecules in tissue sections with a new intermediate-pressure MALDI linear ion trap mass spectrometer

We describe a new intermediate-pressure MALDI linear ion trap mass spectrometer and its capabilities for imaging mass spectrometry. The instrument design is described and is characterized in terms of four performance issues (1) MALDI performance at intermediate pressure; (2) analysis of samples on non-conductive and conductive glass slides; (3) critical importance of tandem mass spectrometry (both MS² and MS³) for identification of analyte species and imaging of isobaric species; (4) capability for repeated analysis of the same tissue section. Application of the new instrument to imaging phospholipids in rat brain sections is described in detail.     

Diagnostic filtering to screen polycyclic polyprenylated acylphloroglucinols from Garcinia oblongifolia by ultrahigh performance liquid chromatography coupled with ion mobility quadrupole time-of-flight mass spectrometry

A novel multistage MS approach, insource collision-induced dissociation (CID) combined with Time Aligned Parallel (TAP) fragmentation, was established to study the fragmentation behavior of polycyclic polyprenylated acylphloroglucinols (PPAPs), which could provide a more reliable fragmentation relationship between precursor and daughter ions. The diagnostic ions for different subtypes of PPAPs and their fragmentation behaviors have been summarized. Moreover, a new and reliable multidimensional analytical workflow that combines ultrahigh performance liquid chromatography (UHPLC), data-independent mass spectrometry (MS^E), and tandem MS with ion mobility (IM) has been optimized and established for the analysis of PPAPs in the plant Garcinia oblongifolia by diagnostic filtering. Diagnostic fragment ions were used to selectively screen PPAPs from extracts, whereas IM coupled to MS was used to maximize the peak capacity. Under the optimized UHPLC-IM-MS^E and UHPLC-IM-MS/MS method, 140 PPAPs were detected from the crude extract of G. oblongifolia, and 10 of them were unambiguously identified by comparing them to the reference compounds. Among those PPAPs, 7 pairs of coeluting isobaric PPAPs that were indistinguishable by conventional UHPLC-HRMS alone, were further resolved using UHPLC-IM-MS. It is anticipated that the proposed method will be extended to the rapid screening and characterization of the other targeted or untargeted compounds, especially these coeluting isomers in complex samples.     

Screening and identification of multi-component in Qingkailing injection using combination of liquid chromatography/time-of-flight mass spectrometry and liquid chromatography/ion trap mass spectrometry

An approach for screening and identification of multi-component in complex traditional Chinese medicine systems with a combinative LC/MS (MSⁿ) technique was described in this paper. The chemical profile of Qingkailing injection, a well-known traditional Chinese formula in China, was studied using the established method as for an application. Benefit from combining the accurate mass measurement of LC/TOF-MS to generate elemental compositions and the complementary multilevel structural information provided by LC/ion trap MSⁿ, 33 components in Qingkailing injection were identified in all. The three isomers of chlorogenic acid, isochlorogenic acid and neochlorogenic acid which are derived from Flos Lonicerae, one of the medicinal materials in Qingkailing, were differentiated by verifying their MS³ fragmentation data. All the components identified were surveyed and classified according to their medicinal materials derivation. This study is expected to provide an effective and reliable pattern for comprehensive and systematic characterization of the complex traditional Chinese medicine systems.