Rapid probe and isolation of bioactive compounds from Dioscorea panthaica using human serum albumin functionalized magnetic nano-particles (HSA-MNPs)-based ligand fishing coupled with electrospray ionization mass spectrometry

The chemical diversity of secondary metabolites in medicinal plant makes it a huge challenge to isolate the bioactive compounds from herbal extracts, so quick recognition of the bioactive ones is of vital importance for improving the efficiency of isolation. In this study, a ligand fishing experiment based on human serum albumin functionalized magnetic nano-particles (HSA-MNPs) was performed to probe the bioactive components in a traditional Chinese medicinal plant, Dioscorea panthaica. The minor compounds fished out by HSA-MNPs were identified by electrospray ionization mass spectrometry (ESI-MS), and then separated from the extract of the whole plant by one or two steps of column chromatography under the guidance of ESI-MS. Four biologically active compounds, progenin II, progenin III, dioscin and gracillin, were isolated much faster than in the normal lengthy phytochemical procedure. The present study demonstrates that biological macromolecule (protein, enzyme, receptor, et al.) functionalized MNPs may serve as baits to recognize bioactive small molecules in complex herbal extracts. It is expected that a macromolecule functionalized MNPs-based ligand fishing experiment coupled with ESI-MS may accelerate the process of identification and isolation of bioactive components from medicinal plants, and thus benefit the speed of drug discovery.     

High performance liquid chromatography/electrospray mass spectrometry of Hypericum perforatum extracts

Hypericum perforatum L. (St. John's Wort) is a widely distributed herbaceous perennial plant which has been well known as a medicinal plant since antiquity. In recent years, H. perforatum has received increasing attention for the treatment of depression and other neuralgic disorders. The main constituents of H. perforatum extract include flavonoids, naphthodianthrones, phloroglucinols, essential oils and xanthones. The present work reports the analysis of naphthodianthrones and phloroglucinols in H. perforatum extracts by means of high performance liquid chromatography (HPLC) coupled simultaneously to a diode array detector (DAD) and electrospray mass spectrometry (ESI-MS). Hypericin, pseudohypericin, hyperforin and adhyperforin were separated and identified on the base of their on-line UV and mass spectra. Quantitative analysis of hypericin derivatives in different extracts of H. perforatum using DAD and MS detectors was performed. In addition, direct infusion ESI-MS of H. perforatum extracts was applied to obtain rapid mass fingerprints of constituents present in the sample.     

Characterization of the variation in the imidazole alkaloid profile of Pilocarpus microphyllus in different seasons and parts of the plant by electrospray ionization mass spectrometry fingerprinting and identification of novel alkaloids by tandem mass spectrometry

Pilocarpus microphyllus (Rutaceae), popularly known as jaborandi, is the only commercial source of an imidazole alkaloid named pilocarpine. In the present study, the variation in the profile of imidazole alkaloids in different seasons and in different parts of the P. microphyllus plant during the summer was analyzed by electrospray ionization mass spectrometry in the positive ion mode [ESI(+)-MS]. The fingerprints of these extracts repeatedly presented similar ions which were mass-selected and studied by tandem mass spectrometry (ESI-MS/MS and ESI-MS/MS/MS) and high-resolution mass spectrometry, resulting in the characterization of eight imidazole alkaloids. The data from the ESI(+)-MS fingerprints were analyzed by principal component analysis (PCA), showing that pilocarpine was present mainly in the summer, whereas in the autumn mainly pilosine and winter anhydropilosine were found. Three alkaloids, reported for the first time in extracts of P. microphyllus, were found. Analysis of the distribution of alkaloids in different parts of the plant during the summer showed that, although pilocarpine was present throughout the plant, 13-nor-8(11)-dihydropilocarpine was found mainly in the stem, pilosine and anhydropilosine were present mainly in the intermediary leaves, and the three new alkaloids were mainly found in the leaflets and petioles. Based on the dissociation patterns of these alkaloids, we observed that there were three structurally related groups of alkaloids differing in their distribution in the plant tissues and responding differently to seasonal variations. These results also indicate that these three groups of alkaloids could belong to intermediate, parallel or competitive pathways for pilocarpine formation biosynthesis.     

Characterization of phenolic compounds in the Chinese herbal drug Tu-Si-Zi by liquid chromatography coupled to electrospray ionization mass spectrometry

Phenolic compounds are the major bioactive constituents of the Chinese herbal drug Tu-Si-Zi, which is prepared from the seeds of Cuscuta chinensis. However, seeds of C. australis also are offered under the name of this drug in the herb market. In order to make a comparison of their chemical constituents, the phenolic compounds of these two Cuscuta species were analyzed by high-performance liquid chromatography/diode-array detection/electrospray ion trap tandem mass spectrometry (HPLC/DAD/ESI-MS(n)). A total of 50 compounds were observed in the methanol extracts, including 23 flavonoids, 20 lignans and 7 quinic acid derivatives. These compounds were separated on a C18 column and identified or tentatively characterized based on UV spectra and MS fragmentation behavior. In contrast to previous reports, the phenolic patterns of these two Cuscuta species were found to be very different. Kaempferol and astragalin were the predominant constituents of C. australis, while hyperoside was the major compound in C. chinensis. Most of the identified compounds, especially the acylated flavonoid glycosides, have not previously been reported from Cuscuta species. In addition, a 30 Da neutral loss observed for flavonols was investigated and could be used to differentiate flavonoid isomers such as kaempferol and luteolin. The ESI-MS fragmentation behavior of furofuran lignans was also investigated, and a characteristic pathway is proposed. The large differences observed between the phenolic constituents of C. chinensis and C. australis strongly encouraged further comparison of the bioactivities of these two species.     

Chemotaxonomic markers of organic, natural, and genetically modified soybeans detected by direct infusion electrospray ionization mass spectrometry

Summary The crude methanolic extracts of a single bean from samples of organic, natural or genetically modified (GM) soybeans [Glycine max. (Merrill) L.] were analyzed by direct infusion electrospray ionization mass spectrometry (ESI-MS). These extracts, containing the most polar natural products of soybeans (free aglycones, monoglucosides, diglucosides and esters including isoflavones and flavones) provide characteristic fingerprinting mass spectra owing to different proportions or sets of components. Spectra distinctiveness is confirmed by chemometric multivariate analysis of the ESI-MS data, which place the three-types of beans into well-defined groups. When ESI-MS is applied, these polar components constitute therefore unique chemotaxonomic markers able to provide fast soybean typification.     

Characterization of dansylated glutathione, glutathione disulfide, cysteine and cystine by narrow bore liquid chromatography/electrospray ionization mass spectrometry

A method using reversed phase high performance liquid chromatography/electrospray ionization-mass spectrometry (RP-LC/ESI-MS) has been developed to confirm the identity of dansylated derivatives of cysteine (C) and glutathione (GSH), and their respective dimers, cystine (CSSC) and glutathione disulfide (GSSG). Cysteine, GSH, CSSC and GSSG are present at low concentrations in rainbow trout (Oncorhynchus mykiss) liver cells. Initially, hepatic cells were sampled from a suspension culture and disrupted upon addition of 10% perchloric acid. The reduced thiols present in the cell extracts were acetylated to prevent dimerization and then the C and GSH species were derivatized with dansyl chloride for fluorescence detection. An LC system using a weak anion exchange column (AE) with fluorescence detection (FLD) was used for sensitive routine analysis; however, it produced peaks of unknown origin in addition to the expected analytes. Analytes were then separated on a C18 RP-LC system using a water/acetonitrile gradient with 0.2% formic acid, and detected using LC/ESI-MS at 3.5 KV which produced an intense ion with a minimum limit of detection of less than 0.5 pmole injected (>10:1 signal-to-noise (S/N). Subsequently, fractions of effluent from the AE-LC/FLD system were analyzed by LC/ESI-MS to confirm the presence of the target analytes in routine cell extracts. Monodansylated GSSG was identified as a product that could possibly affect the quantification of GSH and GSSG.     

Characterization of compounds in the Chinese herbal drug Mu-Dan-Pi by liquid chromatography coupled to electrospray ionization mass spectrometry

Cortex Moutan is a well-known traditional Chinese medicine derived from Paeonia suffruticosa ANDREWS. However, root cortices of P. delavayi and P. decomposita also are used under the name of this drug in some regions such as Yunnan and Sichuan Provinces, respectively. In order to make a comparison of their chemical constituents, the compounds of the three Paeonia species were analyzed by high-performance liquid chromatography-diode array detection/electrospray ionization and quadrupole-time-of-flight tandem mass spectrometry (HPLC-DAD/ESI-MS2). A total of 50 compounds were observed in the 50% (v/v) methanolic extracts, including 17 monoterpenes, 14 galloyl glucoses, 10 acetophenones, 5 phenolic acids, 3 flavonoids and 1 triterpene. These chemical constituents were separated on a C18 column and identified or tentatively characterized based on UV spectra and MS fragmentation behavior. The chemical compositions of the three Paeonia species were found to have many differences. Paeonol was the predominant constituent of P. suffruticosa and P. decomposita, while P. delavayi contained albiflorin and more galloyl glucoses than the other two Paeonia species. Most of these identified compounds have been reported from P. delavayi and P. decomposita for the first time. The ESI-MS fragmentation behavior of monoterpene glycosides, acetophenones and galloyl glucoses was also investigated successively, and appropriate characteristic pathways were proposed. The large differences in chemical compounds among the three Paeonia species strongly encouraged further comparison of the bioactivities of these three species.     

Micro-TLC Approach for Fast Screening of Environmental Samples Derived from Surface and Sewage Waters

In this work we demonstrated analytical capability of micro-planar (micro-TLC) technique comprising one and two-dimensional (2D) separation modes to generate fingerprints of environmental samples originated from sewage and ecosystems waters. We showed that elaborated separation and detection protocols are complementary to previously invented HPLC method based on temperature-dependent inclusion chromatography and UV-DAD detection. Presented 1D and 2D micro-TLC chromatograms of SPE (solid-phase extraction) extracts were optimized for fast and low-cost screening of water samples collected from lakes and rivers located in the area of Middle Pomerania in northern part of Poland. Moreover, we studied highly organic compounds loaded in the treated and untreated sewage waters obtained from municipal wastewater treatment plant “Jamno” near Koszalin City (Poland). Analyzed environmental samples contained number of substances characterized by polarity range from estetrol to progesterone as well as chlorophyll-related dyes previously isolated and pre-purified by simple SPE protocol involving C18 cartridges. Optimization of micro-TLC separation and quantification protocols of such samples were discussed from the practical point of view using simple separation efficiency criteria including total peaks number, log(product ΔhR _F), signal intensity and peak asymmetry. Outcomes of the presented analytical approach, especially using detection involving direct fluorescence (UV366/Vis) and phosphomolybdic acid (PMA) visualization are compared with UV-DAD HPLC-generated data reported previously. Chemometric investigation based on principal components analysis revealed that SPE extracts separated by micro-TLC and detected under fluorescence and PMA visualization modes can be used for robust sample fingerprinting even after long-term storage of the extracts (up to 4 years) at subambient temperature (?20 °C). Such approach allows characterization of wide range of sample components that are present in given extract in high and middle concentration range. Due to protocol simplicity and low cost of analysis this method can be useful for preliminary sample screening.     

High-performance liquid chromatography/mass spectrometric identification of dibenzylbutyrolactone-type lignans: insights into electrospray ionization tandem mass spectrometric fragmentation of lign-7-eno-9,9'-lactones and application to the lignans of Linum usitatissimum L. (Common Flax)

In continuation of our studies into the mass spectrometric detection of natural lignans and their identification in complex mixtures such as crude plant extracts, the electrospray ionization tandem mass spectrometric (ESI-MS/MS) fragmentation of Delta(7,8)-unsaturated dibenzylbutyrolactone-type lignans (lign-7-eno-9,9'-lactones) was studied in detail. It is demonstrated that the characteristic fragmentation allows unambiguous identification including distinction between constitutional isomers. These lignans containing an alpha,beta-unsaturated lactone structure exist as equilibrium mixtures of E- and Z-isomers indistinguishable by mass spectrometry, but it is shown that chromatographic retention time can be used to distinguish between the isomeric forms. Based on these observations, re-analysis of the dichloromethane extract obtained from flowering aerial parts of Linum usitatissimum L. by high-performance liquid chromatography (HPLC)/ESI-MS/MS led to the identification of eighteen lignans of these types (five lignano- and one lignenolactone previously reported along with five further lignano- as well as seven lignenolactones hitherto unreported for this plant). The simultaneous identification of eighteen different lignans in the complex matrix of a crude plant extract by a single analysis demonstrates the potential of this method, which will certainly lead to new insights into the lignan composition and metabolism of different Linum species and many other plants.     

Characterization of isoquinoline alkaloids, diterpenoids and steroids in the Chinese herb Jin-Guo-Lan (Tinospora sagittata and Tinospora capillipes) by high-performance liquid chromatography/electrospray ionization with multistage mass spectrometry

This study sought to determine the primary components (isoquinoline alkaloids, diterpenoids and steroids) in crude extracts of the Chinese herb Jin-Guo-Lan, prepared from the roots of Tinospora sagittata and T. capillipes, by liquid chromatography/electrospray ionization multistage mass spectrometry coupled with diode-array detection (LC-DAD/ESI-MS(n)). After separation on a reversed-phase C(18) column using gradient elution, positive and negative ESI-MS experiments were performed. In positive ion mode, the three types of compounds showed very different characteristic ions: strong [M](+) or [M+H](+) ions were observed for isoquinoline alkaloids; [M+NH(4)](+) and/or [M+H-CO(2)](+) for diterpenoids; [M+H-nH(2)O](+) (n=1-3) for steroids. These adduct ions and/or fragments were used to deduce the mass and categories of known and unknown components in crude extracts, and their structures were further confirmed by ESI-MS(n) in positive ion mode. Moreover, UV absorption peaks obtained from DAD provided useful functional group information to aid the MS(n)-based identification. As a result, 11 compounds were unambiguously identified by comparing with standard compounds and 13 compounds were tentatively identified or deduced according to their MS(n) data. Two of these compounds (13-hydroxycolumbamine and 13-hydroxyjatrorrhizine) were found to be new compounds and another one (13-hydroxypalmatine) was detected for the first time as a natural product. In addition, a [M-*CH(3)-H(2)O](*+) ion in MS(2) of [M](+) after in-source collision-induced dissociation was used to differentiate positional isomers of protoberberine alkaloids, columbamine and jatrorrhizine. Although the roots of T. sagittata and T. capillipes contain almost identical compounds, the content of the compounds in them is dramatically different, suggesting the necessity for further comparison of the bioactivities of the two species.     

Dissimilar chromatographic systems to indicate and identify antioxidants from Mallotus species

The genus of Mallotus contains several species commonly used as traditional medicines in oriental countries. A data set containing 39 Mallotus samples, differing in species, cultivation conditions, harvest season and/or part of the plant was used to develop fingerprints on two dissimilar chromatographic systems. An exploratory analysis with principal component analysis (PCA) was performed on both data sets individually. The results were also combined to obtain additional information on the unknown samples included in the data set. Furthermore, the antioxidant activity of the samples was measured and modelled as a function of the fingerprints using the orthogonal projections to latent structures (O-PLS) technique. The regression coefficients of the models were studied to indicate the peaks potentially responsible for the antioxidant activity. The indicated peaks were analyzed and identified by HPLC coupled to mass spectrometry (HPLC-MS). Because of the complexity of biological samples, it was aspired to separate co-eluting components based on the significant difference in chromatographic selectivity on the dissimilar systems and consequently obtain additional, complementary information on the contribution of the individual components to the antioxidant activity. The results illustrate the potential use of dissimilar chromatographic systems. Several initially co-eluting compounds could be separated on the dissimilar system. The corresponding regression coefficients provided complementary information on the potential antioxidant activity of the separated compounds.     

Peptide fingerprinting of snake venoms by direct infusion nano-electrospray ionization mass spectrometry: potential use in venom identification and taxonomy

Fingerprinting by mass spectrometry has been increasingly used to study venom variations and for taxonomic analyses based on venom components. Most of these studies have concentrated on components heavier than 3 kDa, but Bothrops snake venoms contain many biologically active peptides, principally C-type natriuretic peptides and bradykinin-potentiating peptides (BPPs). In this work, we have examined the peptide profile of Bothrops venoms (B. alternatus, B. erythromelas, B. insularis, B. jararaca, B. jararacussu, B. leucurus and B. moojeni) using direct infusion nano-electrospray ionization mass spectrometry (nano-ESI-MS) subjecting the data further to principal components analysis (PCA) to assess whether the peptide distributions are reliable in distinguishing the venoms. ESI-MS of a low molar mass fraction obtained by ultrafiltration of each venom (5 kDa nominal cutoff filters) revealed that the venoms have a variety of peptides in common but that each venom also contains taxonomic marker peptides not shared with other venoms. One BPP peptide, QGGWPRPGPEIPP, was found to be common to the seven Bothrops species examined. This peptide may represent a specific marker for this genus since it was not found in the venom of the South American rattlesnake, Crotalus durissus terrificus. PCA on the ESI-MS data reveals a close relationship between B. jararaca, B. jararacussu and B. moojeni venoms, with B. leucurus and B. erythromelas being more distant from these three; B. alternatus and B. insularis were also located distant from these five species, as was C. d. terrificus. These results agree partially with established phylogenetic relationships among these species and suggest that ESI-MS peptide fingerprinting of snake venoms coupled with PCA is a useful tool for identifying venoms and for taxonomic analyses.     

Analysis of Geting Bituminous Coal by Electrospray Ionization and Direct Analysis in Real Time Mass Spectrometry

Understanding the structure and composition of coals is important for effective, clean, and value-added utilization. In addition to gas chromatography/mass spectrometry which is commonly used to analyze coal, mass spectrometry (MS) may be used with other ion sources such as electrospray ionization (ESI) and direct analysis in real time (DART) for characterization. In this work, Geting bituminous coal was extracted sequentially and exhaustively with petroleum ether, carbon disulfide, methanol, acetone, an isometric acetone/carbon disulfide mixture, tetrahydrofuran, and an isometric tetrahydrofuran/carbon disulfide mixture. Raw coal, extracts, and the extraction residue were analyzed using MS equipped with ESI or DART. Organic heteroatomic species in the extracts were determined by liquid chromatography-mass spectrometry equipped with ESI. Molecular weight distributions of organic species in raw coal, extracts, and extraction residue were characterized by ESI-MS and DART-MS. Associated molecules and homologous compounds in coal extracts were identified.     

Coumarin’s Anti-Quorum Sensing Activity Can Be Enhanced When Combined with Other Plant-Derived Small Molecules

Coumarins are class of natural aromatic compounds based on benzopyrones (2H-1-benzopyran-2-ones). They are identified as secondary metabolites in about 150 different plant species. The ability of coumarins to inhibit cell-to-cell communication in bacterial communities (quorum sensing; QS) has been previously described. Coumarin and its derivatives in plant extracts are often found together with other small molecules that show anti-QS properties too. The aim of this study was to find the most effective combinations of coumarins and small plant-derived molecules identified in various plants extracts that inhibit QS in Chromobacterium violaceum ATCC 31532 violacein production bioassay. The coumarin and its derivatives: 7-hydroxycoumarin, 7.8-dihydroxy-4-methylcoumarin, were included in the study. Combinations of coumarins with gamma-octalactone, 4-hexyl-1.3-benzenediol, 3.4.5-trimethoxyphenol and vanillin, previously identified in oak bark (Quercus cortex), and eucalyptus leaves (Eucalyptus viminalis) extracts, were analyzed in a bioassay. When testing two-component compositions, it was shown that 7.8-dihydroxy-4-methylcoumarin, 4-hexyl-1.3-benzendiol, and gamma-octalactone showed a supra-additive anti-QS effect. Combinations of all three molecules resulted in a three- to five-fold reduction in the concentration of each compound needed to achieve EC₅₀ (half maximal effective concentration) against QS in C. violaceum ATCC 31532.     

A shotgun tandem mass spectrometric analysis of phospholipids with normal-phase and/or reverse-phase liquid chromatography/electrospray ionization mass spectrometry

Electrospray ionization mass spectrometry is used in lipidomics studies. The present research established a top-down liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) shotgun analysis method for phospholipids (PLs) using a normal-phase column or a C30 reverse-phase column with the data-dependent MS/MS scanning mode. A normal-phase column can separate most of the major different classes of PLs. By using LC/ESI-MS/MS with a normal-phase column, approximately 50 molecular species were identified in a PL mixture from rat liver. When the reverse-phase column was used, the PLs could be separated depending on their hydrophobicity, essentially the length of their fatty acyl chains and the number of unsaturated bonds in them. The LC/ESI-MS/MS method using a C30 reverse-phase column was applied to phosphatidylcholine (PC) and phosphatidylethanolamine (PE) mixtures as test samples. Molecular species with the same molecular mass but with different pairs of fatty acyl chains were separately identified. As a result, about 60 PC and 50 PE species were identified. PLs from rat liver were subjected to LC/ESI-MS/MS using the C30 reverse-phase column and about 110 molecular species were identified. Off-line two-dimensional LC/ESI-MS/MS with the normal-phase and C30 reverse-phase columns allowed more accurate identification of molecular species by using one-dimensional C30 reverse-phase LC/ESI-MS/MS analysis of the collected fractions.     

Letter: characterisation and identification of spermine and spermidine derivatives in Microdesmis keayana and Microdesmis puberula roots by electrospray ionisation tandem mass spectrometry and high-performance liquid chromatography/electrospray ionisation tandem mass spectrometry

Three new N(1),N(5),N(14)-tris(4- hydroxycinnamoyl)spermines were identified in hydromethanolic root extracts of Microdesmis keayana J. Léonard and Microdesmis puberula Hook f. The electrospray ionisation tandem mass spectrometry (ESI-MS/MS) technique with specific nuclear magnetic resonance analysis of hydrolysed products made it possible to identify N(1),N(5),N(14)-tris(p-coumaroyl)spermine, N(1)-feruloyl,N(5),N(14)-di(p-coumaroyl)spermine and N(1),N(5),N(14)-tris(feruloyl)spermine, named keayanines B, C and D, respectively. ESI-MS/MS analysis most effectively provided structural data although high-performance liquid chromatography/electrospray ionisation tandem mass spectrometry was also used to characterise four other compounds from Microdesmis puberula-keayanidines A, B, C and keayanine A-which had already been identified in M. keayana. This chemical data is the first to be published for M. puberula which is a commonly used plant in Central African traditional medicine.     

Mass spectrometric analysis of chemical warfare agents and their degradation products in soil and synthetic samples

A packed capillary liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) method was developed for the identification of chemical warfare agents, their degradation products and related compounds in synthetic tabun samples and in soil samples collected from a former mustard storage site. A number of organophosphorus and organosulfur compounds that had not been previously characterized were identified, based on acquired high-resolution ESI-MS data. At lower sampling cone voltages, the ESI mass spectra were dominated by protonated, sodiated and protonated acetonitrile adducts and/or their dimers that could be used to confirm the molecular mass of each compound. Structural information was obtained by inducing product ion formation in the ESI interface at higher sampling cone voltages. Representative ESI-MS mass spectra for previously uncharacterized compounds were incorporated into a database as part of an on-going effort in chemical warfare agent detection and identification. The same samples were also analyzed by capillary column gas chromatography (GC)-MS in order to compare an established method with LC-ESI-MS for chemical warfare agent identification. Analysis times and full-scanning sensitivities were similar for both methods, with differences being associated with sample matrix, ease of ionization and compound volatility. GC-MS would be preferred for organic extracts and must be used for the determination of mustard and relatively non-polar organosulfur degradation products, including 1,4- thioxane and 1,4-dithiane, as these compounds do not ionize during ESI-MS. Diols, formed following hydrolysis of mustard and longer-chain sulfur vesicants, may be analyzed using both methods with LC-ESI-MS providing improved chromatographic peak shape. Aqueous samples and extracts would, typically, be analyzed by LC-ESI-MS, since these analyses may be conducted directly without the need for additional sample handling and/or derivatization associated with GC-MS determinations. Organophosphorus compounds, including chemical warfare agents, related compounds and lower volatility hydrolysis products may all be determined during a single LC-ESI- MS analysis. Derivatization of chemical warfare agent hydrolysis products and other compounds with hydroxyl substitution would be required prior to GC-MS analysis, giving LC-ESI-MS a definite advantage over GC-MS for the analysis of samples containing chemical warfare agents and/or their hydrolysis products.     

Electrospray ionization mass spectrometry fingerprinting of propolis

Crude ethanolic extracts of propolis, a natural resin, have been directly analysed using electrospray ionization mass (ESI-MS) and tandem mass spectrometry (ESI-MS/MS) in the negative ion mode. European, North American and African samples have been analyzed, but emphasis has been given to Brazilian propolis which displays diverse and region-dependent chemical composition. ESI-MS provides characteristic fingerprint mass spectra, with propolis samples being divided into well-defined groups directly related to their geographical origins. Chemometric multivariate analysis statistically demonstrates the reliability of the ESI-MS fingerprinting method for propolis. On-line ESI-MS/MS tandem mass spectrometry of characteristic [M - H](-) ion markers provides an additional dimension of fingerprinting selectivity, while structurally characterizing the ESI-MS marker components of propolis. By comparison with standards, eight such markers have been identified: para-coumaric acid, 3-methoxy-4-hydroxycinnamaldehyde, 2,2-dimethyl-6-carboxyethenyl-2H-1-benzopyran, 3-prenyl-4-hydroxycinnamic acid, chrysin, pinocembrin, 3,5-diprenyl-4-hydroxycinnamic acid and dicaffeoylquinic acid. The negative mode ESI-MS fingerprinting method is capable of discerning distinct composition patterns to typify, to screen the sample origin and to reveal characteristic details of the more polar and acidic chemical components of propolis samples from different regions of the world.     

Approaches to sample pretreatment in the determination of perchlorate in real world samples

Perchlorate can be determined by the tandem technique of ion chromatography (IC) coupled to electrospray ionization mass spectrometry (ESI-MS). However, detection by ESI-MS can be compromised by the coelution of matrix components that can suppress the analyte signal. In addition, the presence of surface-active and other types of matrix components can cause fouling of the electrospray inlet, reducing overall signal and requiring frequent maintenance. The influences of matrix components can be minimized by using analytical columns with different selectivities, in-line diversion of separated matrix components, and off-line selective removal of matrix components via ion exchange or adsorption. This paper will discuss these sample preparation approaches for samples containing anionic species including surfactants and inorganic ions that elute in the vicinity of perchlorate.