Electrospray Ion Trap Mass Spectrometry Research Articles

Evidence for linkage position determination in known feruloylated mono- and disaccharides using electrospray ion trap mass spectrometry.

Various feruloylated arabinose- and galactose-containing mono- and disaccharides with known linkage configurations (2-O-(trans-feruloyl)-L-arabinopyranose, 5-O-(trans-feruloyl)-L-arabinofuranose, O-[2-O-(trans-feruloyl)-alpha-L-arabinofuranosyl]-(1-->5)-L-arabinofuranose, and O-[6-O-(trans-feruloyl)-beta-D-galactopyranosyl]-(1-->4)-D-galactopyranose) were analyzed by electrospray ionization mass spectrometry using an ion trap or a quadrupole time-of-flight (Q-TOF) mass analyzer. Collision-induced dissociation (CID) experiments using the two mass analyzers generated similar tandem mass spectrometric (MS/MS) fragmentation patterns. However, the ester-bond cleavage ions were more abundant using the Q-TOF mass analyzer. Compared with the positive ion mode, the negative ion mode produces simpler and more useful CID product-ion patterns. For arabinose-containing feruloylated compounds, results obtained with both analyzers show that it is possible to assign the location of the feruloyl group to the O-2 or O-5 of arabinosyl residues. In the characterization of the 2-O-feruloyl and 5-O-feruloyl linkages, the relative abundance of the cross-ring fragment ions at m/z 265 (-60 u or -62 u after 18O-labelling) and at m/z 217 (-108 u or -110 u after 18O-labelling) play a relevant role. For galactose-containing feruloylated compounds, losses of 60, 90 and 120 Da observed in MS3 experiment correspond to the production of 0,2A1, 0,3A1 and (0,2A1-60 Da) cross-ring cleavage ions, respectively, fixing the location of feruloyl group at the O-6 of the galactose residue.

LC–MS analysis of phospholipids and lysophospholipids in human bronchoalveolar lavage fluid

A reversed phase HPLC method was developed for the simultaneous analysis of different phospholipids and lysophospholipids in human bronchoalveolar lavage fluid (BALF). Separation was achieved using a pellicular C8 column at elevated temperatures with an increasing gradient of acetonitrile containing 0.1% formic acid. Detection was carried out by electrospray ionization ion-trap mass spectrometry. Calibration graphs for selected phospholipids (phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol and lysophosphatidylcholine) showed linearity up to 50 ng allowing quantitative determinations. Identification of the individual species within each class was possible with tandem mass spectrometry. Analysis of BALF phospholipids was performed after liquid/liquid extraction with a mixture of chloroform/methanol/acetic acid. Recoveries ranged from 69 to 97% with standard deviations of less than 6%. The limit of detection varied slightly between different classes but was in the range 0.05–0.25 ng total injected amount.

Determination of perfluorooctane sulfonate and perfluorooctanoic acid in human plasma by large volume injection capillary column switching liquid chromatography coupled to electrospray ionization mass spectrometry

Rapid, selective, and sensitive methodology for the quantification of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in human plasma using packed capillary liquid chromatography coupled to electrospray ionization ion-trap mass spectrometry has been developed. Plasma proteins were precipitated using acetonitrile and the resulting supernatant was diluted 1+1 with water containing 10 mM ammonium acetate (NH4Ac) prior to injection. Sample volumes of 250 microL were loaded onto a 30 mm x 0.32 mm ID 10 microm Kromasil C18 precolumn by a carrier solution consisting of 10 mM NH4Ac in ACN/H2O (5/95, v/v) at a flow rate of 100 microL/min, providing on-line analyte enrichment and sample clean-up. Backflushed elution onto a 100 mm x 0.32 mm ID 3.5 microm Kromasil C18 analytical column was conducted using an ACN/H2O solvent gradient containing 10 mM NH4Ac. In order to improve the robustness and performance of the method, perfluoroheptanoic acid (PFHA) was used as internal standard. Separation and detection of PFOA, PFHA, and PFOS were achieved within 10 minutes. Ionization was performed in the negative mode in the m/z range 250-550. The method was validated over the concentration range 1-200 ng/mL for PFOA and over the range 5-200 ng/mL untreated plasma for PFOS, yielding correlation coefficients of 0.997 (PFOA) and 0.996 (PFOS), respectively. The within-assay (n = 6) and between-assay (n = 6) precisions were in the range 2.1-9.2 and 5.6-12%, respectively. The concentration limits of detection (cLOD) of PFOA was 0.5 ng/mL while the cLOD of PFOS was estimated to be 0.2 ng/mL in untreated plasma.

The characterisation of selected drugs with amine-containing side chains using electrospray ionisation and ion trap mass spectrometry and their determination by HPLC–ESI-MS

The electrospray ionisation–ion-trap mass spectrometry (ESI-MS n ) of selected drug compounds with amine-containing side chains has been investigated. Certain characteristic in-source fragmentations have been observed for these molecules. Sequential product ion fragmentation experiments (MS n ) have been performed in order to elucidate the degradation pathways for the [ M + H] + ions and their predominant fragment ions. These MS n experiments also show certain characteristic fragmentations with respect to the amine-containing side chains. QTOF-MS/MS has been used to support the identity of the proposed fragments. The data presented in this paper therefore provides useful information on the structure of these compounds with amine-containing side chains and can be used in the characterisation of such drugs, their structurally related metabolites and unknown molecules of pharmaceutical significance extracted from animal and plant sources, for example. Amphetamine, clenbuterol, flurazepam and methadone can be identified and determined in mixtures at low ng/ml concentrations by the application of HPLC–ESI-MS which can also be used for their analysis in saliva samples.

Rapid and direct analysis of γ-hydroxybutyric acid in urine by capillary electrophoresis–electrospray ionization ion-trap mass spectrometry

The present work was aimed at the development of a capillary electrophoretic analysis of γ-hydroxybutyric acid (GHB) using electrospray ion trap mass spectrometry to achieve the direct and unequivocal detection of this analyte in human urine. Optimized capillary electrophoretic conditions were: injection, 20 s at 0.5 psi (1 psi = 6894.76 Pa); buffer electrolyte, 12.5 mM ammonium formate adjusted to pH 8.35 with diethylamine; fused silica capillary: 100 cm × 50 μm i.d.; separation voltage, 25 kV (forward polarity) + 0.5 psi; room temperature. Electrospray and mass spectrometric conditions were: drying gas and nebulizing gas (nitrogen) at flow rate 3 l/min, temperature 250 °C, nebulizer pressure: 10 psi; sheath liquid solution: methanol–water (90:10) containing 0.1% ammonia delivered at 3 μl/min; spray voltage 3.5 kV. Mass spetrometric detection was carried out in the selected ion monitoring mode of negative molecular ions at 103 m/ z for GHB and 115 m/ z for maleic acid (I.S.). Under these conditions the baseline separation of GHB and the I.S. was obtained. The selectivity of the analysis allowed for direct injection of unextracted urine, previously diluted 1:4 with water. Linearity was assessed in the GHB concentration range from 80 to 1280 μg/ml in urine. Analytical sensitivity (as limit of detection) resulted about 5 μg/ml in water and 20 μg/ml in original urine. Analytical precision was fairly acceptable with R.S.D. values lower than 5% for migration times and 18% for quantitation in real samples, in both intra day and day-to-day experiments. On these grounds, the developed method can be adopted for rapid identification of acute intoxications from GHB in humans.

A Systematical Analysis of Tryptic Peptide Identification with Reverse Phase Liquid Chromatography and Electrospray Ion Trap Mass Spectrometry

In this study we systematically analyzed the elution condition of tryptic peptides and the characteristics of identified peptides in reverse phase liquid chromatography and electrospray tandem mass spectrometry (RPLC-MS/MS) analysis. Following protein digestion with trypsin, the peptide mixture was analyzed by on-line RPLC-MS/MS. Bovine serum albumin (BSA) was used to optimize acetonitrile (ACN) elution gradient for tryptic peptides, and Cytochrome C was used to retest the gradient and the sensitivity of LC-MS/MS. The characteristics of identified peptides were also analyzed. In our experiments, the suitable ACN gradient is 5% to 30% for tryptic peptide elution and the sensitivity of LC-MS/MS is 50 fmol. Analysis of the tryptic peptides demonstrated that longer (more than 10 amino acids) and multi-charge state (+2, +3) peptides are likely to be identified, and the hydropathicity of the peptides might not be related to whether it is more likely to be identified or not. The number of identified peptides for a protein might be used to estimate its loading amount under the same sample background. Moreover, in this study the identified peptides present three types of redundancy, namely identification, charge, and sequence redundancy, which may repress low abundance protein identification.

Study of the determination and pharmacokinetics of Compound Danshen Dripping Pills in human serum by column switching liquid chromatography electrospray ion trap mass spectrometry

Compound Danshen Dripping Pill (CDDP) is an important drug widely used for the treatment of cardiovascular diseases. An active component Danshensu (DS) of CDDP was separated by reversed-phase high performance liquid chromatography using column-switching system and analyzed by electrospray mass spectrometry. With this validated assay the pharmacokinetics of CDDP was studied in 10 healthy volunteers after a single oral administration of 250 mg. After trichloroacetic acid precipitation of serum proteins, the analytes were preconcentrated and black-flushed on a reversed-phase column for separation using a switching valve. The analytes were ionized using negative electrospray ionization (ESI) mode. The precursor ion of m/ z 196.6 was used to quantify DS in serum. The linear calibration curve ranged from 1.25 to 175 μg/mL. The limit of quantification (LOQ) for DS was 0.15 μg/mL. The intra-day and inter-day precision (R.S.D.) was less than 7.4 and 7.9%, respectively.

Siderophore Peptide, a New Type of Post-translationally Modified Antibacterial Peptide with Potent Activity

Microcin E492 (MccE492, 7886 Da), the 84-amino acid antimicrobial peptide from Klebsiella pneumoniae, was purified in a post-translationally modified form, MccE492m (8717 Da), from culture supernatants of either the recombinant Escherichia coli VCS257 strain harboring the pJAM229 plasmid or the K. pneumoniae RYC492 strain. Chymotrypsin digestion of MccE492m led to the MccE492m-(74-84) C-terminal fragment that carries the modification and that was analyzed by mass spectrometry and nuclear magnetic resonance at natural abundance. The 831-Da post-translational modification consists of a trimer of N-(2,3-dihydroxybenzoyl)-l-serine linked via a C-glycosidic linkage to a beta-d-glucose moiety, itself linked to the MccE492m Ser-84-carboxyl through an O-glycosidic bond. This modification, which mimics a catechol-type siderophore, was shown to bind ferric ions by analysis of the collision-induced dissociation pattern obtained for MccE492m-(74-84) by electrospray ion trap mass spectrometry experiments in the presence of FeCl(3). By using a series of wild-type and mutant isogenic strains, the three catechol-type siderophore receptors Fiu, Cir, and FepA were shown to be responsible for the recognition of MccE492m at the outer membrane of sensitive bacteria. Because MccE492m shows a broader spectrum of antibacterial activity and is more potent than MccE492, we propose that by increasing the microcin/receptor affinity, the modification leads to a better recognition and subsequently to a higher antimicrobial activity of the microcin. Therefore, MccE492m is the first member of a new class of antimicrobial peptides carrying a siderophore-like post-translational modification and showing potent activity, which we term siderophore-peptides.

A computational and experimental study of cation affinity (Na+) of nucleobases and modified nucleobases by electrospray ionization ion trap mass spectrometry.

Gas-phase Na+ affinities of modified or unmodified nucleobases were determined theoretically at the density functional theory level, with the B3P86 functional and the 6-31 + G* basis set, and experimentally using electrospray ionization ion trap mass spectrometry (ESI-ITMS) and the kinetic method. For the calculations, the sodium cation affinities (SCA) were obtained from energies of the most stable complexes of the free nucleobases. Experimentally and theoretically relative scales of cation affinities were determined using eight modified and unmodified nucleobases and a very good agreement was obtained.

Brevinin-1 and multiple insulin-releasing peptides in the skin of the frog Rana palustris.

Few studies have comprehensively examined amphibian granular gland secretions for novel insulinotropic peptides. This study involved isolation and characterisation of biologically active peptides from the skin secretions of Rana palustris frogs. Crude secretions obtained by mild electrical stimulation from the dorsal skin surface were purified by reversed-phase HPLC on a semipreparative Vydac C18 column, yielding 80 fractions. These fractions were assayed for insulin-releasing activity using glucose-responsive BRIN-BD11 cells. Acute 20 min incubations were performed in Krebs Ringer bicarbonate buffer supplemented with 5.6 mmol/l glucose in the absence (control) and presence of various fractions. Fractions 29-54 and fractions 68-75 showed significant 2.0-6.5-fold increases in insulin-releasing activity (P<0.001). The fractions showing most prominent insulinotropic activity were further purified to single homogeneous peaks, which, on testing, evoked 1.5-2.8-fold increases in insulin release (P<0.001). The structures of the purified peptides were determined by mass spectrometry and N-terminal amino acid sequencing. Electrospray ionisation ion-trap mass spectrometry analysis revealed molecular masses of 2873.5-8560.4 Da. Sufficient material was isolated to determine the primary amino acid sequence of the 2873.5 Da peptide, revealing a 27 amino acid sequence, ALSILRGLEKLAKMGIALTNCKATKKC, repressing palustrin-1c. The database search for this peptide showed a 48% homology with brevinin-1, an antimicrobial peptide isolated from various Rana species, which itself stimulated insulin release from BRIN-BD11 cells in a concentration-dependent manner. In conclusion, the skin secretions of R. palustris frogs contain a novel class of peptides with insulin-releasing activity that merit further investigation.

Toward the prediction of the activity of antioxidants: experimental and theoretical study of the gas-phase acidities of flavonoids

The relative gas-phase acidities were determined for eight flavonoids, applying the kinetic method, by means of electrospray-ion trap mass spectrometry. The experimental acidity order, myricetin > luteolin > quercetin > (±)-taxifolin > kaempferol > apigenin > (+)-catechin > (±)-naringenin shows good agreement with the order obtained by theoretical calculations at the B3LYP/6-311 + G(2d,2p)//HF/6-31G(d) level. Moreover, these calculations provide the gas-phase acidities of the different OH groups for each flavonoid. The calculated acidity values (Δ acH), corresponding to the most favorable deprotonation, cover a narrow range, 314.8–330.1 kcal/mol, but the experimental method is sensitive enough to differentiate the acidity of the various flavonoids. For all the flavones and the flavanol, catechin, the 4′-hydroxyl group is the most favored deprotonation site whereas for the flavanones studied, taxifolin and naringenin, the most acidic site is the 7-hydroxyl group. On the other hand, the 5-hydroxyl, in flavones and naringenin, and the 3-hydroxyl, in taxifolin and catechin, are always the less acidic positions. The acidity pattern observed for this family of compounds mainly depends on the following structural features: The ortho-catechol group, the 2,3 double bond and the 4-keto group.

Lipid A components from Pseudomonas aeruginosa PAO1 (serotype O5) and mutant strains investigated by electrospray ionization ion-trap mass spectrometry.

The lipid A components of the Pseudomonas aeruginosa strains PAO1 (wild-type) and derived mutants PAO1 algC::tet and PAO1 PDO100 were isolated after mild acetic acid hydrolysis of LPS. Their structural heterogeneities were characterized using electrospray ionization (ESI) ion-trap mass spectrometry (MS) with direct infusion in the negative ion mode without prior derivatization. The ESI-mass spectra revealed monophosphorylated molecules corresponding to known tetra-, penta- and hexaacylated structures of P. aeruginosa lipid A. The MS/MS fragmentation patterns allowed the location of fatty acyl chains on the disaccharide backbone of lipid A. In addition, a hexaacylated lipid A containing a hexadecanoyl chain was detected for the first time in strain P. aeruginosa PAO1. With multiple stages of fragmentation (MS(n)), the position of this hexadecanoyl chain O-linked to the decanoyl chain at the C-3(') position of the glucosamine backbone was determined. This sensitive method is suitable to reveal lipid A heterogeneity, i.e. the nature, number and distribution of acyl chains, without prior lipopolysaccharide purification. The lipid A from mutant strains were also characterized and significant differences were shown in the abundance of monophosphorylated lipid A components between the wild-type and the mutant strains.

Sensitive biomonitoring of phthalate metabolites in human urine using packed capillary column switching liquid chromatography coupled to electrospray ionization ion-trap mass spectrometry.

A rapid and sensitive method for the determination of the phthalate monoesters monoethyl phthalate (MEP), monobutyl phthalate (MBP), monobenzyl phthalate (MBzP) and monoethylhexyl phthalate (MEHP), in human urine, using packed capillary column liquid chromatography coupled to electrospray quadrupole-ion trap mass spectrometry (ESI-QITMS(n)) has been developed. Sample volumes of 200 microL of deconjugated and diluted urine were loaded onto a precolumn of 30 mmx0.32 mm I.D. packed with Hypercarb 5 microm particles, using a sample carrier consisting of acetonitrile/water (15/85, v/v, adjusted to pH 2 using HCl) with a flow rate of 20 microL/min. Backflushed elution onto a 100 mmx0.32 mm I.D. analytical column packed with 5 microm Hypercarb particles was conducted using a tetrahydrofuran/water gradient where both solvents contained 10 mM ammonium acetate, at a flow rate of 4 microL/min. Determination of the monophthalates was achieved within 8 min. Ionization was performed in the negative mode and the analytes were observed as [M-H](-) at m/ z=193.1, 221.1, 255.1 and 277.0 for MEP, MBP, MBzP and MEHP, respectively. Quantification was performed in the multiple reaction monitoring (MRM) mode monitoring the fragments at m/ z=121.1, 177.0, 183.0 and 233.0 for MEP, MBP, MBzP and MEHP, respectively. The method was validated over the concentration range 2.5-125 ng/mL in pretreated urine samples, corresponding to 25-1250 ng/mL untreated urine, yielding correlation coefficients in the range 0.996-0.999. The within-assay ( n=6) and between-assay ( n=6) repeatabilities were in the range 4.0-18% and 4.8-15% RSD, respectively. The mass limits of detection were in the range 32-70 pg, corresponding to concentration limits of detection of 1.6-3.5 ng/mL of untreated urine.

Identification and characterization of selenium species in enriched green onion (Allium fistulosum) by HPLC-ICP-MS and ESI-ITMS

In this study speciation of selenium in selenium-enriched green onions (Allium fistulosum) was done with reversed-phase ion-pairing high performance liquid chromatography (RP-IP-HPLC) and size-exclusion chromatography (SEC) coupled on-line to ICP-MS for selenium specific detection. The plant extract obtained using sodium hydroxide (0.1 mol l−1) analyzed by SEC (CAPS 10 mmol l−1, pH 10.0) with ICP-MS detection showed the incorporation of selenium in both high (∼12 kDa) and low molecular weight (0.36–2 kDa) fractions. Presumably protein bound selenoamino acids were released using enzymes (Proteinase K and Protease XIV) and selenoamino acids found in cytosol in their free form were extracted using 0.1 M HCl. The extracts were analyzed for speciation studies by RP-IP-HPLC [0.1% (v/v) heptafluorobutyric acid, 5% (v/v) methanol, pH 2.5]. Matching the chromatographic retention times with commercially available standards provided evidence for the presence of Se-cystine, methylselenocysteine, Se-methionine, and inorganic selenium. Electrospray ionization ion trap mass spectrometry (ESI-ITMS) confirmed the presence of γ-glutamyl-Se-methylselenocysteine in green onions as has been reported in other onion types.

Mechanism of enzymatic degradation of the azo dye Orange II determined by ex situ 1H nuclear magnetic resonance and electrospray ionization-ion trap mass spectrometry

Mechanism of enzymatic degradation of the azo dye Orange II determined by ex situ 1H nuclear magnetic resonance and electrospray ionization-ion trap mass spectrometry

Nano-scale liquid chromatography-mass spectrometry of 2-aminobenzamide-labeled oligosaccharides at low femtomole sensitivity

Conventional normal-phase high performance liquid chromatography of fluorescently labeled oligosaccharides with or without on-line mass spectrometry is an established tool for the structure characterization of protein and lipid derived glycans. Here we describe the miniaturization of such a system to the nano-scale using a 75 μm internal diameter normal-phase amide column on-line with electrospray ionization ion-trap mass spectrometry. 2-Aminobenzamide-labeled oligosaccharides have a predictable retention on this normal-phase column that can be expressed as glucose units by comparison to the retention of a standard 2-aminobenzamide glucose polymer mixture. Isobaric compounds are separated on the basis of their structural differences, and by on-line electrospray ionization ion-trap mass spectrometry, the sequence of the monosaccharides can be deduced. The major improvement of the on-line nano-LC-MS system in comparison to conventional systems is the gain in sensitivity with detection of low femtomole amounts of glycans. This implies that LC-MS of 2-aminobenzamide-labeled oligosaccharides can now be performed at higher sensitivity than their analysis with fluorescence detection.

Characterisation of selected hypnotic drugs and their metabolites using electrospray ionisation with ion trap mass spectrometry and with quadrupole time-of-flight mass spectrometry and their determination by liquid chromatography-electrospray ionisation–ion trap mass spectrometry

The electrospray ionisation–ion trap mass spectrometry (ESI–MS n ) of selected hypnotic drugs, i.e. zopiclone, zolpidem, flunitrazepam and their metabolites have been investigated. Sequential product ion fragmentation experiments (MS n ) have been performed in order to elucidate the degradation pathways for the [ M+H] + ions and their predominant fragment ions. These MS n experiments show certain characteristic fragmentations in that functional groups are generally cleaved from the ring systems as neutral molecules such as H 2O, CO, CO 2, NO 2, amines and HF. When an aromatic entity is present in a drug molecule together with a nitrogen-containing saturated ring structure as with zopiclone and its N-desmethyl metabolite fragmentation initially occurs at the latter ring with the former being resistant to fragmentation. The structures of fragment ions proposed for ESI–MS n can be supported by electrospray ionisation–quadrupole time-of-flight mass spectrometry (ESI–QTOF–MS). These molecules can be identified and determined in mixtures at low ng/ml concentrations by the application of liquid chromatography (LC)–ESI–MS n which can be used for their analysis in saliva samples. This paper includes a tabulation of mass losses/signals at low m/ z values for these hypnotic drugs and many others in recent publications which will be of value in the characterisation of drug metabolites of unknown structure and also natural product pharmaceuticals isolated from plants, etc.

Metabolite profiling in rat urine by liquid chromatography/electrospray ion trap mass spectrometry. Application to the study of heavy metal toxicity.

This work reports the use of reverse-phase liquid chromatography coupled to electrospray ion trap (QIT) mass spectrometry for the analysis of the metabolome in rat urine. An injection of 20 microL of urine into the chromatographic system is followed by a slow gradient elution and mass spectrometric detection in the scanning mode from m/z 100-1000 in both positive and negative modes. Over a time scale of 90 min, 30 and 20 resolved peaks were observed in the positive and the negative modes, respectively, corresponding to the presence of a few hundred m/z ratios. By using a QIT analyzer, data-dependent tandem mass spectrometry of selected m/z ratios identified several compounds in rat urine and characterized various chemical families, including carboxylic acids, amines, sulfated compounds, glucuronides and glycosides, by the observation of characteristic fragment ions or neutral losses. The method has been applied to the investigation of the chronic toxicity of heavy metals in rat urine. A few tens of m/z ratios, differing in intensity more than threefold from control values, were observed in both positive and negative modes. The time variations for some selected ions suggest that LC/ESI-MS could allow selective characterization of biomarkers in response to specific toxic compounds.

Determination of loratadine in human plasma by liquid chromatography electrospray ionization ion-trap tandem mass spectrometry

A sensitive and specific liquid chromatography electrospray ionization ion-trap mass spectrometry (LC–ESI-IT-MS/MS) method has been developed and validated for the identification and quantitation of loratadine in human plasma. After the addition of the internal standard (IS), plasma samples were extracted using isooctane:isoamyl alcohol mixture. The compounds were separated on a prepacked Zorbax phenyl column using a mixture of acetonitrile, 0.20% formic acid as mobile phase. A Finnigan LCQ DUO ion-trap mass spectrometer connected to a Waters Alliance high performance liquid chromatography (HPLC) was used to develop and validate the method. The results were within the accepted criteria as stated in the FDA bioanalytical method validation guidance. The method was proved to be sensitive and specific by testing six different plasma batches. Linearity was established for the range of concentrations 0.10–10.0 ng/ml with a coefficient of determination ( r 2) of 0.9998. Accuracy for loratadine ranged from 105.00 to 109.50% at low, mid and high levels. The intra-day precision was better than 10.86%. The lower limit of quantitation (LLOQ) was identifiable and reproducible at 0.10 ng/ml with a precision of 9.84%. The proposed method enables the unambiguous identification and quantitation of loratadine for pharmacokinetic, bioavailability or bioequivalence studies.

Separation of cisplatin and its hydrolysis products using electrospray ionization high-field asymmetric waveform ion mobility spectrometry coupled with ion trap mass spectrometry.

Cisplatin and its mono- and dihydrated complexes have been separated using a high-field asymmetric waveform ion mobility spectrometry (FAIMS) analyzer interfaced with electrospray ionization (ESI) and ion trap mass spectrometry (ITMS). The addition of helium to the nitrogen curtain/carrier gas in the FAIMS device improved both the sensitivity and selectivity of the electrospray analysis. Introduction of a three-component mixture as curtain/carrier gas, nitrogen, helium, and carbon dioxide, resulted in further improvements to sensitivity. Compared with conventional ESI-MS, the background chemical noise in the ESI-FAIMS-ITMS spectrum was dramatically reduced, resulting in over 30-fold improvement in the signal-to-noise ratio for cisplatin. Analytical results were linear over the concentration range 10-200 ng/mL for intact cisplatin with a corresponding detection limit determined of 0.7 ng/mL with no derivatization or chromatographic separation prior to analysis.