Silver complexation and tandem mass spectrometry for differentiation of isomeric flavonoid diglycosides

For detection and differentiation of isomeric flavonoids, electrospray ionization mass spectrometry is used to generate silver complexes of the type (Ag + flavonoid)+. Collisionally activated dissociation (CAD) of the resulting 1:1 silver/flavonoid complexes allows isomer differentiation of flavonoids. Eighteen flavonoid diglycosides constituting seven isomeric series are distinguishable from each other based on the CAD patterns of their silver complexes. Characteristic dissociation pathways allow identification of the site of glycosylation, the type of disaccharide (rutinose versus neohesperidose), and the type of aglycon (flavonol versus flavone versus flavanone). This silver complexation method is more universal than previous metal complexation methods, as intense silver complexes are observed even for flavonoids that lack the typical metal chelation sites. To demonstrate the feasibility of using silver complexation and tandem mass spectrometry to characterize flavonoids in complex mixtures, flavonoids extracted from grapefruit juice are separated by high-performance liquid chromatography and analyzed via a postcolumn complexation ESI-MS/MS strategy. Diagnostic fragmentation pathways of the silver complexes of the individual eluting flavonoids allow successful identification of the six flavonoids in the extract.     

Enhanced detection of flavonoids by metal complexation and electrospray ionization mass spectrometry

Metal complexation with the use of an auxiliary ligand is explored as an alternative to conventional protonation or deprotonation for analysis of a series of flavonoids by electrospray ionization mass spectrometry. Use of a neutral auxiliary ligand, 2,2'-bipyridine, results in formation of [MII(flavonoid - H)bpy]+, ternary complexes with intensities that are 2 orders of magnitude greater than the corresponding protonated flavonoids and up to 1.5 orders of magnitude greater than the deprotonated flavonoids, based on confirmation by collisionally activated dissociation patterns. The formation of ternary complexes with six divalent transition metals, Co2+, Ni2+, Cu2+, Zn2+, Mn2+, and Fe2+ were compared. Cu2+ resulted in the most intense complexes and simplest mass spectra, while Co2+ gave the second most intense spectra and also produced two key products that could be useful for a selected ion monitoring strategy. Complexation with iron(III) bromide is also investigated to explore the feasibility of using triply charged metals.     

Quantitation of lysergic acid diethylamide in urine using atmospheric pressure matrix-assisted laser desorption/ionization ion trap mass spectrometry

A quantitative method was developed for analysis of lysergic acid diethylamide (LSD) in urine using atmospheric pressure matrix-assisted laser desorption/ionization ion trap mass spectrometry (AP MALDI-ITMS). Following solid-phase extraction of LSD from urine samples, extracts were analyzed by AP MALDI-ITMS. The identity of LSD was confirmed by fragmentation of the [M + H](+) ion using tandem mass spectrometry. The quantification of LSD was achieved using stable-isotope-labeled LSD (LSD-d(3)) as the internal standard. The [M + H](+) ion fragmented to produce a dominant fragment ion, which was used for a selected reaction monitoring (SRM) method for quantitative analysis of LSD. SRM was compared with selected ion monitoring and produced a wider linear range and lower limit of quantification. For SRM analysis of samples of LSD spiked in urine, the calibration curve was linear in the range of 1-100 ng/mL with a coefficient of determination, r(2), of 0.9917. This assay was used to determine LSD in urine samples and the AP MALDI-MS results were comparable to the HPLC/ ESI-MS results.     

Physical Studies of Some Hydrazinobenzoic Acid Complexes

The stability constants of complexes of 2-hydrazinobenzoic acid and 4-hydrazinobenzoic acid with Ni (Ⅱ), Cu (Ⅱ),Zn (Ⅱ), Cd (Ⅱ), and Hg (Ⅱ) were determined potentiometrically at different temperatures. The thermodynamic parameters,△AG°,△AH°, and △S° were calculated and proved that the complexation process is spontaneous and endothermic. The thermodynamic functions were analyzed in terms of electrostatic and non-electrostatic components and the results reveal that ionic bonds are formed between the studied ligands and metal ions. Conductometric titration was shown that the stoichiometry of the formed complexes are M:L and M:2L. The structure of the prepared solid complexes was characterized using IR, 1H NMR, 13C NMR spectroscopies as well as X-ray diffraction technique.Finally electrical conductivity of the ligands and their copper complexes was measured and shown that the ligands have a semiconductor behaviour.     

Development and validation of a one-step immunoassay for determination of cadmium in human serum.

A sensitive and simple one-step immunoassay was developed and validated for quantitative determination of Cd(II) in human serum. In this method, a monoclonal antibody that recognizes Cd(II)-EDTA complexes was directly immobilized onto microwell plates. The serum sample containing metallothionein(MT)-bound and non-MT-bound Cd(II) was acidified to displace the Cd(II) from MT. The sample was then treated with metal-free EDTA to convert Cd(II) to Cd(II)-EDTA complexes. A mixture of Cd(II)-EDTA complexes derived from serum samples and Cd(II)-EDTA conjugated with peroxidase enzyme was incubated in the wells to compete for binding sites of the immobilized antibody. After addition of peroxidase substrate, the bound fraction of the enzyme conjugate was measured by a microplate reader, and the signal was inversely proportional to the concentration of the Cd(II) in the sample. The assay limit of detection was 0.24 microg/L, and the effective working range at coefficient of variation of < or = 10% was 0.24-100 microg/L. Analytical recovery of spiked Cd(II), in the concentration range between 0.8 and 50 microg/L, was 97.8 +/- 4.0%. The assay was selective for Cd(II); other metal ions (Mn, Co, Cu, Zn, Mg, Hg, Ca, Ni, Fe, and Pb), tested at concentrations considerably higher than those present in human serum, did not significantly interfere with the assay. The assay results correlated well with those obtained by graphite furnace atomic absorption spectrometry (r = 0.984).     

Synthesis and photophysical studies of blue phosphorescent Ir(III) complexes with dimethylphenylphospine

New blue emitting mixed ligand iridium(III) complexes comprising one cyclometalating, two phosphines trans to each other such as Ir{(CF3)2Meppy}(PPhMe3)2(H)(L) [L = CI, NCMe, CN] [(CF3)2Meppy = 2-(3', 5'-bis-trifluoromethylphenyl)-4-methylpyridine] were synthesized and studied to tune the phosphorescence wavelength to the deep blue region and to enhance the luminescence efficiencies. To achieve deep blue emission, the trifluoromethyl group substituted on the phenyl ring and the methyl group substituted on the pyridyl ring increased HOMO-LUMO gap and achieved the hypsochromic shift. To gain insight into the factors responsible for the emission color change and the different luminescence efficiency, we investigate the electron-withdrawing capabilities of ancillary ligands using the DFT and TD-DFT calculations on the ground and excited states of the complexes. From these results, we discuss how the ancillary ligand influences the emission peak as well as the metal to ligand charge transfer (MLCT) transition efficiency. The maximum emission spectra of Ir{(CF3)2Meppy}(PPhMe3)2(H)(Cl), [Ir{(CF3),Meppy)(PPhMe3),(H)(NCMe)]+ and Ir{(CF3)2Meppy}(PPhMe3)2(H)(CN) were in the ranges of 441, 435, 434 nm, respectively.     

Kinetic Resolution of d,l-Amino Acids Based on Gas-Phase Dissociation of Copper(II) Complexes

Chiral recognition of d- and l-amino acids is achieved in the gas phase on the basis of the kinetics of competitive fragmentations of trimeric Cu(II)-bound complexes. The singly charged copper(II)-amino acid trimeric cluster ions [A(2)BCu(II) - H](+) dissociate to form [A(2)Cu(II) - H](+) and [ABCu(II) - H](+) upon collision-induced dissociation (CID) in a quadrupole ion trap. The abundance ratios of these fragments depend strongly on the stereochemistry of the ligands in the [A(2)BCu(II) - H](+) complex ion. The kinetic method was used to calculate relative Cu ion affinities (ΔCu(II)') for homo- and heterochiral copper(II)-bound dimeric cluster ions as the indicator of chiral discrimination. Six amino acids of four different types showed chiral distinctions which ranged from 0 to 6.5 kJ/mol in terms of values of ΔCu(II)' with abundance ratios, referenced to the other enantiomer, ranging from 1 to 9.2. Amino acids with aromatic substituents displayed the largest chiral distinction, which correlates well with reported chromatographic results. The methodology presented here provides a sensitive means to study enantiomers by mass spectrometry, and initial results show that it is applicable to measurement of enantiomeric excess.     

Analysis of epipolythiodioxopiperazines in fungus Chaetomium cochliodes using HPLC-ESI-MS/MS/MS

A series of epipolythiodioxopiperazines in the fungus Chaetomium cochliodes was investigated using reversed-phase liquid chromatography with diode array detection and electrospray quadrupole time-of-flight-type tandem mass spectrometry in the positive ion mode. The fragmentation of protonated molecular ions including low-abundance parent ions, [M+H]+ for five known epipolythiodioxopiperazines, dethiotetra(methylthio)chetomin, chaetocochins A-C, and chetomin, was carried out using low-energy collision-induced electrospray ionization tandem spectrometry. It was found that McLafferty rearrangements occurred in the CID processes and produced a complementary pair of characteristic fragment ions containing piperazine rings (fused and unfused), especially to determine the number of S atoms on each ring. The fragmentation differential between [M+H]+ and [M+Na]+ was uncovered. Complementary fragmentation information obtained from [M+H]+ and [M+Na]+ precursor ions is especially valuable for rapid identification of epipolythiodioxopiperazines. A likely known compound, possibly related to chetoseminudin A, and three new species of epipolythiodioxopiperazines from the fungus C. cochliodes were identified or tentatively characterized based on tandem mass spectra of known ones.     

Structural analysis of ionic organotin(IV) compounds using electrospray tandem mass spectrometry

A novel electrospray ionization (ESI) mass spectrometric approach for the structure elucidation of ionic organotin(IV) compounds or complexes with weakly bonded ligands as for example monodentate carboxylates or sulfonates is proposed using both positive-ion and negative-ion ESI tandem mass spectra. The ionization mechanism of organotin(IV) compounds involves the cleavage of the most labile bond with an ionic character yielding two complementary ions, [Cat]+ and [An]-. Positively charged species containing tin atom, [Cat]+, are analyzed in the positive-ion mode and negatively charged species without the tin atom, [An]-, in the negative-ion mode. Fragmentation patterns of [C24H29N2Sn]+, [C21H22NSn]+, and [C17H30NSn]+ ions are proposed based on the detailed interpretation of MSn spectra, which is simplified by an easy recognition of characteristic tin isotopic clusters in particular fragment ions. Proposed fragmentation mechanisms are supported by comparison with MSn spectra of deuterium-labeled analogues. The applicability of this method is illustrated on two sets of organotin(IV) compounds, including seven [2,6-bis(dimethylaminomethyl)phenyl]diphenyltin(IV) derivatives with small inorganic counteranions X (Br, NO3, SCN, BF4, SeCN, CN, PF6), six organotin(IV) complexes containing two C,N-chelating ligands with azo dyes, and the identification of unknown hydrolysis products.     

Terbutaline enantiomer separation and quantification by complexation and field asymmetric ion mobility spectrometry-tandem mass spectrometry

Recently, we introduced a new approach to chiral separation and analysis of amino acids by chiral complexation and electrospray high-field asymmetric waveform ion mobility spectrometry coupled to mass spectrometry (ESI-FAIMS-MS). In the present work, we extended this approach to the separation of the drug compound terbutaline. Terbutaline enantiomers were complexed with metal ions and an amino acid to form diastereomeric complexes of the type [M(II)(L-Ref)2((+)/(-)-A)-H](+), where M(II) is a divalent metal ion, L-Ref is an amino acid in its L-form, and A is the terbutaline analyte. When metal and reference compound were suitably chosen, these complexes were separable by FAIMS. We also detected and characterized larger clusters that were transmitted at distinct FAIMS compensation voltages (CV), disturbing data analysis by disintegrating after the FAIMS separation and forming complexes of the same composition [M(II)(L-Ref)2((+)/(-)-A)-H](+), thus giving rise to additional peaks in the FAIMS CV spectra. This undesired phenomenon could be largely avoided by adjusting the mass spectrometer skimmer voltages in such a way that said larger clusters remained intact. In the quantitative part of the present work, we achieved a limit of detection of 0.10% (-)-terbutaline in a sample of (+)-terbutaline. The limit of detection and analysis time per sample compared favorably to literature values for chiral terbutaline separation by HPLC and CE.     

Solid-phase extraction of Mn(II), Co(II), Ni(II), Cu(II), Cd(II) and Pb(II) ions from environmental samples by flame atomic absorption spectrometry (FAAS)

A new method using a column packed with Amberlite XAD-2010 resin as a solid-phase extractant has been developed for the multi-element preconcentration of Mn(II), Co(II), Ni(II), Cu(II), Cd(II), and Pb(II) ions based on their complex formation with the sodium diethyldithiocarbamate (Na-DDTC) prior to flame atomic absorption spectrometric (FAAS) determinations. Metal complexes sorbed on the resin were eluted by 1 mol L(-1) HNO3 in acetone. Effects of the analytical conditions over the preconcentration yields of the metal ions, such as pH, quantity of Na-DDTC, eluent type, sample volume and flow rate, foreign ions etc. have been investigated. The limits of detection (LOD) of the analytes were found in the range 0.08-0.26 microg L(-1). The method was validated by analyzing three certified reference materials. The method has been applied for the determination of trace elements in some environmental samples.     

Complexation of Be(II) Ion with 1-(2,4-Dihydroxy-1-phenylazo)-8-hydroxy-3,6-naphthalenedisulfonate as the Chemical Basis of the Selective Detection of Ultratrace Be by Reversed-Phase High-Performance Liquid Chromatography

The complexation reactions of beryllium(II) ion with 1-(2,4-dihydroxy-1-phenylazo)-8-hydroxy-3,6-naphthalenedisulfonate (H-resorcinol) are studied. The acid dissociation constants of H-resorcinol, H(3)L(2-), at 293 K and I = 0.10 [K(OH, NO(3))] are pK(a)((1)) = 5.67, pK(a)((2)) = 8.57, and pK(a)((3)) > 13. The formation constant at 293 K and I = 0.10 [(K,H)NO(3)] is estimated to be log[{[Be(HL)(2-)][H(+)](2)}/{[Be][H(3)L(2-)]}] = -4.58, and pK(a)' = 6.39 for [Be(HL)](2-), which give the basis for the optimization of the precolumn chelation reactions and the masking system with EDTA. The kinetic data for ligand substitution reactions with sulfosalicylate ion are also reported to demonstrate the remarkable inertness of the Be chelate, which is suitable for HPLC separation. Reported is an accurate method for determining traces of Be(II) ion at nanomolar levels with photometric detection coupled with ion-pair reversed-phase HPLC. The chelate, [Be(II)L](3-), is efficiently separated on an Asahipak ODP-50 column using tetrabutylammonium bromide as an ion-pairing agent in a methanol (35 wt %)-water eluent. Only Al and Fe give peaks under the conditions used. The large molar absorptivity of the H-resorcinol chelate, 3.99 × 10(4) M(-1) cm(-1) at 500 nm, and the short retention time with excellent peak resolution ensure the ultralow detection limit (3σ blank) down to 7.2 ppt (0.8 nM) with no preconcentration procedures. The excellent toughness toward the matrix influence was demonstrated using the model solution for an air-dust sample. The HPLC separation, coupled with the EDTA masking procedure, enables one to detect Be(II) ion at 20 nM in the presence of metals at the natural abundance levels in air samples, such as Al, Fe, Ca, Mg, Zn, and Pb at 240, 140, 300, 66, 16, and 6.2 μM, respectively, in the final solution.     

Preparation of the diphenylcarbazone-functionalized silica gel and its application to on-line selective solid-phase extraction and determination of mercury by flow-injection spectrophotometry

A new solid-phase extractor, diphenylcarbazone-functionalized silica gel has been synthesized and confirmed by IR and Raman spectrometry. The new solid-phase extractor is found to be stable in 1-6 mol L(-1) HCl or H(2)SO(4), and also in common organic solvents. It can be used to separate and enrich Hg(II) selectively from eight metal ions with similar characteristics such as Cd(II), Ni(II), Co(II), Mn(II), Pb(II), Zn(II), Cu(II) and Fe(III). The pre-concentration factor is as high as 500. The results show that this new solid extractor has a good stability and can be reused for many times without decreasing its extraction percentage. The micro-column packed with diphenylcarbazone-functionalized silica gel was used for on-line solid-phase extraction and determination of mercury in real samples by flow-injection spectrophotometry. At the optimal conditions, the linear range and the detection limit for the determination of Hg(II) is found to be 1-1500 and 0.90 ng mL(-1), respectively. The relative standard deviation of 11 replicate measurements is less than 3%. The proposed method was demonstrated to be simple, fast, selective, low cost and less pollution.     

Identification and quantification of arsenolipids using reversed-phase HPLC coupled simultaneously to high-resolution ICPMS and high-resolution electrospray MS without species-specific standards

Although it has been known for decades that arsenic forms fat-soluble arsenic compounds, only recent attempts to identify the compounds have been successful by using a combination of fractionation and elemental and molecular mass spectrometry. Here we show that arsenolipids can directly be identified and quantified in biological extracts using reversed-phase high-performance liquid chromatography (RP-HPLC) simultaneously online-coupled to high-resolution inductively coupled plasma mass spectrometry (ICPMS) and high-resolution electrospray mass spectrometry (ES-MS) without having a lipophilic arsenic standard available. Using a methanol gradient for the separation made it necessary to use a gradient-dependent arsenic response factor for the quantification of the fat-soluble arsenic species in the extract. The response factor was obtained by using the ICPMS signal of known concentration of arsenic. The arsenic response was used to determine species-specific response factors for the different arsenic species. The retention time for the arsenic species was utilized to mine the ES-MS data for accurate mass and their tandem mass spectrometry (MS/MS) fragmentation pattern to give information of molecular formula and structure information. The majority of arsenolipids, found in the hexane phase of fish meal from capelin ( Mallotus villosus ) was in the form of three dimethylarsinoyl hydrocarbons (C(23)H(38)AsO, C(17)H(38)AsO, C(19)H(42)AsO) with minor amounts of dimethylarsinoyl fatty acids (C(17)H(36)AsO(3), C(23)H(38)AsO(3), C(24)H(38)AsO(3)). One of the dimethylarsinoyl fatty acids (C(24)H(38)AsO(3)), with an even number of carbon in the fatty acid chain, was identified for the first time in this work. This molecular formula is unusual and in contrast to all previously identified arsenic-containing fatty acids with odd numbers of carbon.     

Characterization of dipeptide isomers by tandem mass spectrometry of their mono- versus dilithiated complexes

The Li+ complexes of the isomeric dipeptide pairs PheGly/GlyPhe, PheAla/AlaPhe, and TrpAla/AlaTrp, namely, [Pep + Li]+, and of the corresponding lithium carboxylates, namely, [Pep - H + 2Li]+, are produced in the gas phase by desorption ionization, and their unimolecular chemistry is probed by tandem mass spectrometry experiments at various activation conditions. At low internal energies, monolithiated isomers dissociate to the same products, formed through a mixed anhydride intermediate in which the sequence information is lost. Isomerization to the mixed anhydride is less competitive at higher internal energies, which start promoting sequence-specific fragmentations. On the other hand, dilithiated isomers (they contain a permanent COO-Li+ salt bridge) do not rearrange to an anhydride and give rise to substantially different fragmentation patterns; structurally diagnostic c1- and y1-type fragments are observed at all internal energies, allowing for unequivocal sequence assignment. The mono- and dilithiated peptides undergo loss of their aromatic side chain to form distonic radical ions carrying Li+ charge(s) and one unpaired electron at an alpha-C atom of the peptide backbone. The yield of such metal-bound peptide radicals is particularly high from the dilithiated complexes, [Pep - H + 2Li]+. Upon activation, the Li+ ions become mobile and can be shuttled to the various basic sites of the dipeptides, where they may initiate backbone fragmentation or the elimination of small neutral molecules.     

Thermolysis of some transition metal nitrate complexes with 1,4-diamino butane ligand

Four complexes are prepared and characterized having molecular formula [Zn(dab)(2)](NO(3))(2), [Cu(dab)(2)](NO(3))(2).H(2)O, [Ni(dab)(2)](NO(3))(2).2H(2)O and [Mn(dab)(2)](NO(3))(2), where dab: 1,4-diaminobutane. Thermolyses of these complexes were investigated by simultaneous thermogravimetry (TG), derivatives thermogravimetry (DTG), differential thermal analysis (DTA) and differential scanning calorimetry (DSC). The kinetics of the thermolysis at early stages is investigated using isothermal TG by applying model-fitting and isoconversional method. Thermolytic process is slow in inert (N(2)) and is fast in air atmosphere due to oxidative nature. To investigate the response of these complexes under the condition of rapid heating, ignition delay (D(i)) has been measured. Thermal stability of the complexes was found to increase in the order Mn < Cu < Ni < Zn.     

Speciation of mercury by hydrostatically modified electroosmotic flow capillary electrophoresis coupled with volatile species generation atomic fluorescence spectrometry

A novel method for speciation analysis of mercury was developed by on-line hyphenating capillary electrophoresis (CE) with atomic fluorescence spectrometry (AFS). The four mercury species of inorganic mercury Hg(II), methymercury MeHg(I), ethylmercury EtHg(I), and phenylmercury PhHg(I) were separated as mercury-cysteine complexes by CE in a 50-cm x 100-microm-i.d. fused-silica capillary at 15 kV and using a mixture of 100 mmol L(-1) of boric acid and 12% v/v methanol (pH 9.1) as electrolyte. A novel technique, hydrostatically modified electroosmotic flow (HSMEOF) in which the electroosmotic flow (EOF) was modified by applying hydrostatical pressure opposite to the direction of EOF was used to improve resolution. A volatile species generation technique was used to convert the mercury species into their respective volatile species. A newly developed CE-AFS interface was employed to provide an electrical connection for stable electrophoretic separations and to allow on-line volatile species formation. The generated volatile species were on-line detected with AFS. The precisions (RSD, n = 5) were in the range of 1.9-2.5% for migration time, 1.8-6.3% for peak area response, and 2.3-6.1% for peak height response for the four mercury species. The detection limits ranged from 6.8 to 16.5 microg L(-1) (as Hg). The recoveries of the four mercury species in the water samples were in the range of 86.6-111%. The developed technique was successfully applied to speciation analysis of mercury in a certified reference material (DORM-2, dogfish muscle).     

Spectrophotometric determination of aluminium and indium with 2,2',3,4-tetrahydroxy-3',5'-disulphoazobenzene

2,2',3,4-Tetrahydroxy-3',5'-disulphoazobenzene (tetrahydroxyazon 2S) has been synthesized for the first time. This reagent has been used for the spectrophotometric determination of aluminium and indium ions. The method is very sensitive and selective for the direct determination of aluminium and indium. The optimum pH and absorbance of complexes formed of tetrahydroxyazon 2S with aluminium and indium are 5; 500 nm and 495 nm for Al and In, respectively. The system obeys Beer's law at 0.05-1.6 microg mL(-1) of aluminium and 0.06-2.1 microg mL(-1) of indium concentration. The molar absorptivity is 6.42 x 10(4)L mol(-1)cm(-1) for aluminium and 7.70 x 10(4)L mol(-1)cm(-1) for indium. The molar compositions of the complexes are 1:1 at optimum conditions. Alkaline and alkaline earth elements, halogens, thiourea, ascorbic acid, Cd(II), Pb(II), Mn(II), Zn(II), Co(II), Ni(II), Cr(III), Bi(III), La(III), Si(IV) do not interfere this method. The method can be applied to the direct spectrophotometric determination of trace amounts of aluminium in steel, alloys, waste water, river waters, spring water and ground water. The method was also successfully applied to the indium determination in artificial mixture.     

A multi-element solid-phase extraction method for trace metals determination in environmental samples on Amberlite XAD-2000

A method for the preconcentration of some transition elements at trace level was proposed using a column filled with Amberlite XAD-2000 resin. Metal ions were adsorbed on XAD-2000 as their diethyldithiocarbamate chelates, then analytes retained on the resin were eluted by 1 mol L(-1) nitric acid in acetone and determined by flame atomic absorption spectrometry (FAAS). The influences of some analytical parameters including pH of sample solution, ligand amount, the type, concentration and volume of elution solution, flow rates of the sample and eluent solutions, adsorption capacity of the resin and sample volume on the preconcentration efficiency have been investigated. The influences of some matrix elements were also examined. The detection limit (N=20, 3 sigma) for Mn(II), Fe(II), Co(II), Cu(II), Cd(II), Zn(II), Pb(II) and Ni(II) were found as 0.20, 0.35, 0.25, 0.20, 0.20, 0.15, 0.45 and 0.25 microg L(-1), respectively. The validation of the procedure was carried out by analysis of certified reference materials. The proposed method was applied to natural waters and kale vegetable (Brassica oleracea var. acephala).     

Development of a liquid chromatography-electrospray-tandem mass spectrometry method for the quantitative determination of benzoxazinone derivatives in plants

A new method for the quantification of benzoxazinone derivatives in extracts of wheat foliage and root samples using liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS-MS) is described. Using this method, the characterization, separation, and quantitative detection of a mixture of six naturally occurring 1,4-benzoxazin-3(4H)-one derivatives, including the hydroxamic acids (DIMBOA, DIBOA), lactams (HBOA, and HMBOA), benzoxazilinones (BOA, MBOA), and two synthetic methoxylated variations of DIBOA and HBOA, was achieved. The application of a novel, highly modified reversed-phase LC column, the dodecyl (C12) TMS end-capped Synergi MAX-RP, enhanced the on-line chromatographic separation through improvements to component resolution, analyte stability and peak shape and also to the column lifetime. The complete ESI-MS-MS precursor-product ion fragmentation pathways for the benzoxazinone derivatives are described for the first time and used to deduce a generic fragmentation pattern for the compound class. Characteristic transitions for the benzoxazinones were thus used in the developed analytical method enabling reliable quantification with simultaneous screening for other potentially present derivatives, while eliminating interferences from other coeluting contaminants from the complex plant extract matrix. Quantitative analysis was done in the multiple reaction monitoring mode, using two specific combinations of a precursor-product ion transitions for each compound. The ESI-MS-MS detection method offered improvements to the sensitivity and selectivity, as compared with previously applied LC methods, with detection limits down to 0.002-0.023 ng/microL. The developed method was demonstrated by analyzing foliages and roots of six different wheat cultivars using pressurized liquid extraction-solid-phase extraction cleanup-LC-ESI-MS-MS. The analytes were detected in the range of 0.7-207 microg/g of dry weight.