Analytical Chemistry Chemical Cytometry Quantitates Superoxide

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Anal. Chem. 2010, 82, 6764–6769 Development of a Compound-Specific Carbon Isotope Analysis Method for 2-Methyltetrols, Biomarkers for Secondary Organic Aerosols from Atmospheric Isoprene Qiang Li, § Wu Wang,* ,†,‡ Hong-Wei Zhang, ‡ Yang-Jun Wang,* ,† Bing Wang, | Li Li, † Huai-Jian Li, † Bang-Jin Wang, † Jie Zhan, † Mei Wu, ⊥ and Xin-Hui Bi @ Institute of Environmental Pollution and Health, Shanghai University, 200444 Shanghai, China, Southern Medical University, 510515 Guangzhou, China, School of Stomatology, Tongji University, 200072 Shanghai, China, Hefei Artillery Academy, 230002 Hefei, China, Laboratory of Human Micromorphology, Qingdao University Medical College, 266071 Qingdao, China, and State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, 510640 Guangzhou, China The stable carbon isotope compositions of 2-methyltetrols, biomarker compounds for secondary organic aerosols formed from isoprene in the atmosphere, have been determined by gas chromatography/combustion/ isotope ratio mass spectrometry (GC/C/IRMS). In this work, isoprene with various δ 13 C values was used to produce 2-methyltetrols via an oxidation reaction with hydrogen peroxide in sulfuric acid under direct sunlight. The target compounds with different stable carbon isotope compositions were then derivatized by methylboronic acid with a known δ 13 C value and measured by GC/C/IRMS. With δ 13 C values of 2-methyltetrols and methylboronic acid predetermined, isotopic fractionation is evaluated for the derivatization process. Through reduplicate δ 13 C measurements, the carbon isotope analysis achieved excellent reproducibility and high accuracy with an average error of
indicators of atmospheric processing of volatile organic compounds; 9 for example, carbon isotope ratio measurements allow the calculation of the extent of photochemical processing of isoprene in the atmosphere. 10 Furthermore, Rudolph et al. 11 developed a gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) technique to measure the stable carbon isotope ratios of isoprene and its gas-phase oxidation products, MACR and MVK, and to gain insight into the atmospheric oxidation of isoprene. Very recently, this group has reported studies on the stable carbon kinetic isotope effects (KIE) of the reactions of isoprene, MACR, and MVK with OH radicals, as well as with ozone in the gas phase. 12-14 These data are valuable for obtaining insight into the role of loss processes in determining the atmospheric mixing ratios. However, there are no isotopic studies of isoprene SOA products in the aerosol phase. Methylboronic acid (MBA) has been reported to determine natural 13 C abundances of monosaccharides by derivatizing adjacent hydroxyl groups of monosaccharides followed by N,Obis(trimethylsilyl)trifluoroacetamide (BSTFA) derivatization of the remaining single OH groups. 15,16 Recently, Boschker et al. 17 reported a versatile method for stable carbon isotope analysis of carbohydrates by high-performance liquid chromatography/ isotope ratio mass spectrometry. To develop a compound-specific isotope analysis method for 2-methyltetrols, marker compounds of photooxidation products of isoprene, a technique from our previous work was adapted. 18 MBA was used as the derivatization reagent prior to gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). The derivatizing C from the reagent accounts for 29% of the analyte in the boronates, but 70% in the trimethylsilyl (TMS) derivatives. Therefore, the sensitivity of the MBA method should be high. The oxidation reaction of isoprene, atmospheric sampling, accuracy, and reproducibility of the method will be discussed in detail, and the stable carbon isotope effects during the procedure will be evaluated. δ 13 C data for atmospheric 2-methyltetrols will also be presented to demonstrate the practical utility of this method. EXPERIMENTAL SECTION Materials. Isoprene was obtained from three suppliers: Fluka, Sigma-Aldrich (>98% pure, M1); Alfa-Aesar (Lancaster, England) (99% pure, M2); and Toyo Kasei Kogyo Co. (Osaka, Japan) (99% pure, M3). Hydrogen peroxide (30% in water) was purchased from Guoyao (Shanghai, China). Methylboronic acid (MBA) was (9) Rudolph, J.; Czuba, E. Geophys. Res. Lett. 2000, 27, 3865–3868. (10) Rudolph, J.; Anderson, R. S.; Czapiewski, K. V.; Czuba, E.; Ernst, D.; Gillespie, T.; Huang, L.; Rigby, C.; Thompson, A. E. J. Atmos. Chem. 2003, 44, 39–55. (11) Iannone, R.; Koppmann, R.; Rudolph, J. J. Atmos. Chem. 2007, 58, 181– 202. (12) Rudolph, J.; Czuba, E.; Huang, L. J. Geophys. Res. 2000, 105, 29323–29346. (13) Iannone, R.; Koppmann, R.; Rudolph, J. Atmos. Environ. 2008, 38, 4093– 4098. (14) Iannone, R.; Koppmann, R.; Rudolph, J. Atmos. Environ. 2009, 43, 3103– 3110. (15) van Dongen, B.; Schouten, S.; Damste, J. Rapid Commun. Mass Spectrom. 2001, 15, 496–500. (16) Gross, S.; Glaser, B. Rapid Commun. Mass Spectrom. 2004, 18, 2753–2764. (17) Boschker, H. T. S.; Moerdijk-Poortvliet, T. C. W.; van Breugel, P.; Houtekamer, M.; Middelburg, J. J. Rapid Commun. Mass Spectrom. 2008, 22, 3902–3908. (18) Wang, W.; Li, L.; Li, H.; Zhang, D.; Wen, S.; Jia, W.; Wang, B.; Sheng, G.; Fu, J. Rapid Commun. Mass Spectrom. 2009, 23, 2675–2678. purchased from ABCR GmbH and Co. KG (Karlsruhe, Germany) (97% pure) and recrystallized three times from a benzene/acetone mixture (3:1). MBA of the same lot number was used for all derivatizations. Anhydrous pyridine (99% pure) was supplied by Acros Organics (Geel, Belgium). BSTFA [N,O-bis(trimethylsilyl) trifluoroacetamide] was purchased from Pierce (Rockford, IL). All solvents employed were HPLC grade. Preparation of Standard 2-Methyltetrols. 2-Methyltetrols were made by photooxidation of isoprene, which we conducted by exposing a 30 mL flask with a mixture of 5 mL of 30% H2O2 and 5 mL of isoprene (0.05 mol, 3.4 g) to sunlight. A few drops of sulfuric acid (0.1 M) was added until the pH of reaction mixture was between 1 and 2. The resulting mixture was then maintained with continuous and vigorous stirring in sunlight for4h; 19 15 mg of barium carbonate was added to 1 mL of the reacted solution for neutralization. After centrifugation, the supernatant was dried, and a slightly yellow oil (2.5 g, 36% yield) was obtained. It worth noting that exposure to sunlight is crucial for the production of 2-methyltetrols. The purification of crude 2-methyltetrols was performed according to a procedure reported by Wang et al. 20 The purity of 2-methyltetrols was verified by gas chromatography/mass spectrometry (GC/MS) after they had been derivatized with BSTFA, and the δ 13 C value was determined by elemental analyzer/ isotope ratio mass spectrometry (EA/IRMS). Derivatization of 2-Methyltetrols. The derivatization technique of 2-methyltetrols with methylboronic acid was adapted from Wang et al.; 18 100 µL of a solution of 2-methyltetrols (approximately 1 mg/mL in methanol) was dried under a gentle nitrogen flow, and then 5 mL of a solution of 1 mg of methylboronic acid in 10 mL of anhydrous pyridine was added. The molar ratio of MBA to 2-methyltetrols was ∼10:1. The mixture was allowed to react at 60 °C for 60 min. It should be noted that the pretreatment of pyridine with 4 Å molecular sieves in excess is crucial for a successful MBA derivatization. The δ 13 C value of methylboronic derivatives was determined by gas chromatography/combustion/isotopic ratio mass spectrometry (GC/C/ IRMS). Measurements of the δ 13 C Value of Standard Isoprene. The method for determining the δ 13 C value of isoprene was as follows. 21 Isoprene (1 mL) was sealed in a2mLglass vial with an open screw cap containing a Teflon-lined silica septum. After ∼1 h for equilibrium, 15 µL gas samples from the glass bottle were injected into the split/splitless injection port of the gas chromatograph using a Hamilton gastight locking syringe. Aerosol Sampling. Samples were collected in boreal-temperate Changbai Mountain Forest Ecosystem Research Station in Jilin Province and subtropical Dinghu Mountain Nature Reserve in Guangdong Province. The details for sampling sites have been described previously. 6 The sampling occurred during the summer when the meteorological conditions and the maximum solar radiation, as well as high temperatures, were favorable for the photooxidation of isoprene. A high-volume PM2.5 air sampler (19) Santos, L.; Dalmazio, L.; Eberlin, M.; Claeys, M.; Augusti, R. Rapid Commun. Mass Spectrom. 2006, 20, 2104–2108. (20) Wang, W.; Vas, G.; Dommisse, R.; Loones, K.; Claeys, M. Rapid Commun. Mass Spectrom. 2004, 18, 1787–1797. (21) Yu, Y.; Wen, S.; Feng, Y.; Bi, X.; Wang, X.; Peng, P.; Sheng, G.; Fu, J. Anal. Chem. 2006, 78, 1206–1211. <strong>Analytical</strong> <strong>Chemistry</strong>, Vol. 82, No. 16, August 15, 2010 6765
Page 1 and 2: Anal. Chem. 2010, 82, 6745-6750 Let
Page 3 and 4: purchased from Invitrogen-Molecular
Page 5 and 6: Figure 3. Electropherograms of TPP-
Page 7 and 8: Anal. Chem. 2010, 82, 6751-6755 Res
Page 9 and 10: (pH 8.0) with cysteine and cystamin
Page 11 and 12: Figure 4. Ion mobility mass spectra
Page 13 and 14: GOx glucose + O298 gluconic acid +
Page 15 and 16: coater at 2000 rpm for 20 s, and th
Page 17 and 18: Figure 5. Comparison of cyclic volt
Page 19: in channels with either no grooves
Page 23 and 24: Figure 1. GC/MS total ion chromatog
Page 25 and 26: Table 2. Concentrations and Stable
Page 27 and 28: on a substrate are preferred. 20-24
Page 29 and 30: Figure 4. SERS analysis of NAADP co
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Page 33 and 34: tion, 2 µL of proprionaldehyde wer
Page 35 and 36: Figure 4. Analysis of 2a by HPLC-MS
Page 37 and 38: eaction of 1a with PBH can be condu
Page 39 and 40: Numerous references had demonstrate
Page 41 and 42: Figure 1. TEM images of the prepare
Page 43 and 44: Figure 4. Schematic representation
Page 45 and 46: esult in a big SPR signal change wi
Page 47 and 48: also reduces chemical noise, which
Page 49 and 50: Table 1. Extraction Yields, Liquid
Page 51 and 52: scanning of AMPP amides of the anal
Page 53 and 54: Anal. Chem. 2010, 82, 6797-6806 δ
Page 55 and 56: Figure 1. Schematic view of the pre
Page 57 and 58: from the specimen and enclosed in a
Page 59 and 60: Figure 4. (A) IRMS mass-44 chromato
Page 61 and 62: Table 3. Ambient Measurement Result
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Page 65 and 66: Polymerase (1 U per sample). Reacti
Page 67 and 68: of which was constant for all ampli
Page 69 and 70: analytically useful signals at less
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carbon black and RP-C18 for the ext
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solution in an equal volume, and 1
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Table 2. Concentrations and Ratios
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Anal. Chem. 2010, 82, 6821-6829 Mac
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mg/mL protein, followed by separati
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Figure 2. Productivity of SEQUST an
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Figure 4. High-resolution MS/MS spe
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Figure 6. Characterization of PSMs
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containing T-T mismatches. 23 Based
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Figure 1. Extinction spectra of sol
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Figure 3. (A) The value of Ex650 nm
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Figure 5. Extinction spectra and co
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wished to explore the dehydration o
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constant medium for separation; we
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Figure 2. Standards of (Pi)n, n ) 1
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Figure 5. Quantitative calibration
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Anal. Chem. 2010, 82, 6847-6853 Met
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Figure 1. 226 Ra spectrum by liquid
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Table 1. Counting Properties and De
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Table 3. Analysis of 226 Ra in Sedi
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mercial microarray scanner and fabr
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Figure 2. Optical transmission meas
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Figure 5. Volcano plots detailing t
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data as well. The 41 genes in Table
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corresponding compound if its chemi
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Figure 1. Schematic illustration of
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Table 1. Absolute Quantification Re
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ment. Therefore, the long-time drea
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Figure 1. Chemically actuated micro
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Figure 2. Influence of a surfactant
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Figure 5. Device to eject and mix s
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Anal. Chem. 2010, 82, 6877-6886 Imm
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NaCl, phosphate buffer saline (PBS)
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Figure 2. Product ion mass spectra
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-70 °C resolved the problem, givin
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Table 1. Intraday Precision and Acc
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Anal. Chem. 2010, 82, 6887-6894 Fer
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Figure 1. Infrared spectra of (A) u
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Figure 3. Cyclic voltammograms obta
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Figure 6. Calculated charge from ch
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Anal. Chem. 2010, 82, 6895-6903 Ele
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Table 1. Chemical Structure, pKa Va
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pH with a tilted baseline (Figure 1
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Table 2. Linearity and Detection Li
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ascorbic acid (AA), uric acid (UA),
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the multielement capabilities, the
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RESULTS AND DISCUSSION Sulfur Detec
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Table 2. Molecular Properties and C
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Anal. Chem. 2010, 82, 6911-6918 Dir
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dilution and hybridization buffer.
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solution under appropriate incubati
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Figure 4. Standardization curve for
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Anal. Chem. 2010, 82, 6919-6925 Ele
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the ×10 objective, to have a large
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Figure 2. With a suitable removal o
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the NB signal in a much better foot
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Scheme 1. Reactions of Selenium Rea
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Figure 2. (a) ESI-MS spectrum showi
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Figure 4. (a) ESI-MS spectrum showi
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Anal. Chem. 2010, 82, 6933-6939 Dif
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trode 28 by a finite element using
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Figure 4. Comparison between simula
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Figure 6. Comparison between simula
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educed in the vicinity of double bo
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Figure 2. Normalized product ion ab
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Figure 4. EID (a) and IRMPD (b) of
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Anal. Chem. 2010, 82, 6947-6957 Ide
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Figure 1. Schematic flowchart showi
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difference, ppm compound Table 1. I
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isoforms, its successful use, in th
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Figure 5. Extracted ion current ESI
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m/z 1172.935 was observed for Ser14
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linked products via affinity tags.
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Scheme 2. Fragmentation Mechanism o
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Figure 1. (A) ESI-LTQ-CID-MS 2 prod
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Figure 3. (A) ESI-LTQ-CID-MS 2 prod
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Figure 5. (A) MALDI-TOF/TOF product
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Anal. Chem. 2010, 82, 6969-6975 Ana
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Figure 3. Equilibrium response as a
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Figure 6. The average measured resp
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for the fill time, and we find that
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nucleotide tails. 3-5 Thus, the amo
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allow the use of higher aptamer con
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quent ligation of the aptamers afte
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Anal. Chem. 2010, 82, 6983-6990 Imp
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Figure 2. Configuration editor wind
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Figure 4. Dependencies between volu
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Since the time for liquid expulsion
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Anal. Chem. 2010, 82, 6991-6999 Int
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Figure 1. Representation of the Car
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Table 2. Capillary Electrophoresis
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Figure 4. (A) Typical raw electroph
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field. DNA profiles were delivered
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Another approach to handle this lim
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(principal components, PCs) in whic
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Figure 5. Relevant score plots and
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CONCLUSIONS In this paper we have i
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electroactive-species loaded liposo
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Figure 2. Qdot-based FLFTS response
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Figure 6. Fluorescence imaging of Q
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Anal. Chem. 2010, 82, 7015-7020 Sel
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Table 1. Effect of 1 D-LC Condition
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Figure 3. Peak-production rate vers
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Anal. Chem. 2010, 82, 7021-7026 Cel
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luciferase (T7 control vector) was
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Figure 3. Inhibitory effects of luc
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Anal. Chem. 2010, 82, 7027-7034 Pat
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Electrochemistry. Electrochemical m
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Figure 2. SEM images of Au substrat
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Table 3. Film Thickness Measurement
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Anal. Chem. 2010, 82, 7035-7043 Qua
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Figure 1. (A) FL spectra of BSPOTPE
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Figure 4. (A) Variation in the FL i
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Figure 6. (A) FL spectra of BSPOTPE
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Scheme 1. Proposed Mechanism for Fl
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one or more drawbacks including poo
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Figure 2. Free fluorophores do not
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Anal. Chem. 2010, 82, 7049-7052 Dev
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Figure 2. Comparative analysis of d
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