Negative Electrospray Ionization-tandem Mass Spectrometry Research Articles

Phenolic compounds from three brown seaweed species using LC-DAD–ESI-MS/MS

The phenolic compounds of extracts from Ascophyllum nodosum (ANE), Bifurcaria bifurcata (BBE) and Fucus vesiculosus (FVE) from Galicia (NW Spain) were analyzed by liquid chromatography-diode array detection coupled to negative electrospray ionization-tandem mass spectrometry (LC-DAD–ESI-MS/MS) with the interest to evaluate their potential application as functional ingredients. Phlorotannins were tentatively identified as the main phenolic compounds in the three extracts, followed by phenolic acids, and flavonoids. Fuhalols were present in ANE and BBE, while hydroxyfuhalols were identified in BBE and FVE. Eckol derivatives were present in the three extracts. Quinic acid derivatives were tentatively identified in the three seaweed species; in addition, ANE showed specifically hydroxybenzoic and rosmarinic acid derivatives, BBE showed rosmarinic acid, and FVE contained p-coumaric and ferulic acid derivatives. Regarding flavonoids, acacetin derivatives were tentatively identified in the three extracts, hispidulin and a gallocatechin derivative were specifically detected in ANE, and cypellocarpin C was present in BBE. In conclusion, all brown seaweed extracts studied could be exploited as sources of antioxidant phenolic compounds with potential applications in the food and health sectors.

Perfluorinated compounds (PFCs) in the atmosphere of Shenzhen, China: Spatial distribution, sources and health risk assessment

This study investigated the occurrence of perfluorinated compounds (PFCs) in the atmosphere of Shenzhen, China. 11 PFCs, including two perfluoroalkyl sulfonic acids (PFSAs, C6 and C8) and perfluoroalkyl carboxylic acids (PFCAs, C4–12) were determined by high performance liquid chromatography–negative electrospray ionization-tandem mass spectrometry (HPLC/ESI-MS/MS). Total PFC concentrations (∑ PFCs) in the atmospheric samples ranged from 3.4 to 34pgm−3 with an average of 15pgm−3. Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) were the two most abundant PFCs and on average accounted for 35% and 22% of ∑ PFCs, respectively. ∑ PFCs and total PFCA concentrations (∑ PFCAs) showed a tendency of low-lying East West, while the distribution of total PFSA concentrations (∑ PFSAs) was uniform. Higher concentrations of ∑ PFCs were found in Bao’an District which had very well-developed manufacturing industries. PCA model was employed to quantitatively calculate the contributions of sources. The results showed that PFOA-factor, long chain PFCs-factor and PFOS-factor were the three main source categories for PFCs in the atmosphere. Meanwhile, long-distance transport of pollutants from southeastern coastal areas might be another source of PFCs in Shenzhen atmosphere. PFCs in the atmosphere were more positively correlated with the levels PM10 than PM2.5, which indicated PFCs were more likely to adhere to particles with relatively large sizes. The hazard ratios of noncancer risk through breathing based on PFOS and PFOA concentrations were calculated and were less than unity, suggesting that PFCs concentrations may pose no or immediate threat to the residents in Shenzhen.

Simultaneous Analysis of Phytohormones in Fruits Using High-Performance Liquid Chromatography Mass Spectrometry

A method for the highly sensitive detection of some phytohormones is described. We evaluated some simple methods for the extraction and purification of phytohormones using organic solvents and high-performance liquid chromatography-mass spectrometry (LC-MS) using atmospheric pressure chemical ionization (APCI). The methodology developed was used for the simultaneous detection and quantitative determination of a series of 5 phytohormones, including indole-3-acetic acid (IAA), abscisic acid (ABA), cytokinins (CKs), gibberellins (GAs) and jasmonic acids (JAs). The detection limits ranged from 0.07 pmol for JA to 4.0 pmol for ABA. Compared with previous negative electrospray ionization-tandem mass spectrometry (ESI-MS/MS) methods, the sensitivity was found to be sufficient for the detection and analysis of the above phytohormones. This method was sufficiently sensitive to permit the measurement of the endogenous concentrations of IAA, ABA, CKs, GAs, and JAs in extracts of the “Le lectier” fruit.

Determination of dehydroandrographolide succinate in human plasma by liquid chromatography tandem mass spectrometry (LC–MS/MS): Method development, validation and clinical pharmacokinetic study

A LC–MS/MS method was developed and validated for the determination of dehydroandrographolide succinate (DAS), a traditional Chinese medicine derivative used for the treatment of pneumonia, upper respiratory tract infection, and chronic bronchitis. Following protein precipitation, DAS was detected by ion transition at m/ z 531.2/99.0 in multiple reaction monitoring mode with negative electrospray ionization-tandem mass spectrometry. The limit of detection was 0.5 ng/mL, and the lower limit of quantification was 10 ng/mL in human plasma. Good linearity was maintained over the range of 10–5000 ng/mL, and the correlation coefficient was better than 0.99. The accuracy ranged from 95.3% to 113%, RSD from 0.928% to 6.47%, for the within- and between-run analysis at all QC levels. The recovery ranged from 85.5% to 93.4% and the matrix effect from 107% to 119%. No significant carryover and good stability were found during method validation. The developed method was successfully applied to the determination of DAS in human plasma in a pharmacokinetic study following intravenous infusion of potassium sodium DAS to nine healthy volunteers.

Liquid Chromatographic Determination of Narirutin and Hesperidin in Zhi Ke (Citrus aurantium L.) in the Form of the Raw Herb and of the Dried Aqueous Extract

A validated analytical method is reported for the analysis of narirutin and hesperidin in Zhi Ke (Citrus aurantium L.) in the form of the dried raw herb and of the commercially prepared dried aqueous extract. The samples were extracted by sonication in methanol and the extract was analyzed by liquid chromatography-photodiode array (PDA) detection with identity confirmation by negative electrospray ionization-tandem mass spectrometry (MS). A C18 column was used with a methanol-water gradient mobile phase. Narirutin and hesperidin were quantified at 284 nm using the PDA detector. Using the MS detector, the narirutin precursor ion with m/z 579 produced daughter ions with m/z 271 and 151. For hesperidin, the precursor ion with m/z 609 produced the m/z 301, 285, and 164 ions. The amounts of narirutin and hesperidin found in the certified raw herb were 14.2 and 147.9 mg/g, respectively, and in the dried aqueous extract the amounts were 9.2 and 8.6 mg/g, respectively. For the raw herb, the average recovery across the three spike levels (50, 100, and 150%) for narirutin and hesperidin were 110.7 and 94.5%, respectively. For the dried aqueous extract, the average recovery across the three spike levels for narirutin and hesperidin were 85.8 and 98.9%, respectively.

Determination of Ten Haloacetic Acids in Drinking Water Using High-Performance and Ultra-Performance Liquid Chromatography-Tandem Mass Spectrometry

Haloacetic acids (HAAs) are a class of byproducts resulting from the reaction of chlorinated disinfectants with natural organic matter. These chemicals have been found in animal studies to possibly influence hepatic, reproductive, and developmental functions, and they may be mutagenic and carcinogenic. Because HAAs are hydrophilic and strongly acidic, it is a challenge to measure them at low levels. In this study, nine traditional HAAs and monoiodoacetic acid, an emerging disinfection byproduct, are analyzed in water directly. HAAs were separated on a BetaMax Acid column or a HILIC UPLC column, and they were detected by negative electrospray ionization-tandem mass spectrometry. Although the on-column limits of detection of HAAs were lower when using an HILIC UPLC column (0.08-2.73 microg/L) than when using a BetaMax Acid column (0.18 to 71.5 microg/L), to use an HILIC UPLC column, it was required to dissolve water samples in 90% acetonitrile before injection and result in sample dilution. BetaMax Acid column was found to be more suitable for the analysis of HAAs in drinking water because there was no need of sample preparation. Major species of HAAs, such as dichloroacetic acid and trichloroacetic acid, and other primary species (e.g., dibromoacetic acid, bromochloroacetic acid and bromodichloroacetic acid) can be detected using the BetaMax Acid column at concentrations higher than 1-3 microg/L.

Hot-water and solid-phase extraction of fluorescent whitening agents in paper materials and infant clothes followed by unequivocal determination with ion-pair chromatography-tandem mass spectrometry

A comprehensive method for the determination of four stilbene-type disulfonate and one distyrylbiphenyl-type fluorescent whitening agents (FWAs) in paper materials (napkin and paper tissue) and infant clothes was developed. FWAs were extracted from paper material and cloth samples using a hot-water extraction, and the aqueous extracts were then preconcentrated with the newly developed Oasis WAX (mixed-mode of weak anion exchange and reversed-phase sorbent) solid-phase extraction cartridge. The analytes were unequivocal determined by ion pair chromatography coupled with negative electrospray ionization-tandem mass spectrometry (HPLC-ESI–MS–MS), applying a di- n-hexyl-ammonium acetate (DHAA) as the ion-pairing reagent in mobile phase. Limits of quantitation (LOQ) were established between 0.2 and 0.9 ng/g in 2 g of samples. Recovery of five FWAs in spiked commercial samples was between 42 and 95% and RSD ( n = 3) ranging from 2 to 11%. The method was finally applied to commercial samples, showing that two stilbene-type disulfonates were predominant FWAs detected in napkin and infant cloth samples.

A method for profiling classes of plant hormones and their metabolites using liquid chromatography-electrospray ionization tandem mass spectrometry: an analysis of hormone regulation of thermodormancy of lettuce (Lactuca sativa L.) seeds.

A highly selective and sensitive method for the simultaneous analysis of several plant hormones and their metabolites is described. The method combines high-performance liquid chromatography (HPLC) with positive and negative electrospray ionization-tandem mass spectrometry (ESI-MS/MS) to quantify a broad range of chemically and structurally diverse compounds. The addition of deuterium-labeled analogs for these compounds prior to sample extraction permits accurate quantification by multiple reaction monitoring (MRM). Endogenous levels of abscisic acid (ABA), abscisic acid glucose ester (ABA-GE), 7'-hydroxy-abscisic acid (7'-OH-ABA), phaseic acid (PA), dihydrophaseic acid (DPA), indole-3-acetic acid (IAA), indole-3-aspartate (IAAsp), zeatin (Z), zeatin riboside (ZR), isopentenyladenine (2iP), isopentenyladenosine (IPA), and gibberellins (GA)1, GA3, GA4, and GA7 were determined simultaneously in a single run. Detection limits ranged from 0.682 fmol for Z to 1.53 pmol for ABA. The method was applied to the analysis of plant hormones and hormonal metabolites associated with seed dormancy and germination in lettuce (Lactuca sativa L. cv. Grand Rapids), using extracts from only 50 to 100 mg DW of seed. Thermodormancy was induced by incubating seeds at 33 degrees C instead of 23 degrees C. Germinating seeds transiently accumulated high levels of ABA-GE. In contrast, thermodormant seeds transiently accumulated high levels of DPA after 7 days at 33 degrees C. GA1 and GA3 were detected during germination, and levels of GA1 increased during early post-germinative growth. After several days of incubation, thermodormant seeds exhibited a striking transient accumulation of IAA, which did not occur in seeds germinating at 23 degrees C. We conclude that hormone metabolism in thermodormant seeds is surprisingly active and is significantly different from that of germinating seeds.

Simultaneous analysis of 14 non-steroidal anti-inflammatory drugs in human serum by electrospray ionization—tandem mass spectrometry without chromatography

A method is described for the simultaneous analysis of 14 non-steroidal anti-inflammatory drugs (NSAIDS) in human serum using negative electrospray ionization-tandem mass spectrometry (ESI-MS/MS). After addition of internal standard and protein precipitation using acetonitrile, samples were transferred to autosampler vials for direct analysis without chromatography. Injection of an air bubble with the sample and a multiple reaction monitoring (MRM) method using argon collision-induced dissociation (CID) of analyte (M-H)- ions permitted integration of the product ion peak areas to produce reproducible quantitative data over the range of concentrations expected in serum during routine use of these drugs. The method permitted the analysis of 30 samples per hour. Two hundred fifty consecutive analyses did not adversely affect instrument sensitivity.