Analytical Chemistry Chemical Cytometry Quantitates Superoxide

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Figure 3. GC/C/IRMS chromatogram of 2-methyltetrol-MBA derivatives: (a) standard derivative and (b) extract of the fine size fraction of a 24 h Hi-Vol aerosol sample collected at Dinghu, China, on August 2, 2006. Compounds 1 and 2 are 2-methylerythritol-MBA derivatives, and compound 3 is the 2-methylthreitol-MBA derivative. those predicted by eq 1. The predicted and measured δ 13 C values of methylboronates agreed well with each other. According to Rieley’s discussion of the kinetic isotope effect, 24 when a bond containing the carbon atom under consideration is changed in the rate-determining step, the primary isotopic effect is the most significant. If no carbon bond changed in the ratedetermining reaction or if no carbon-containing bond is involved in this step, there should not be a primary isotope effect on the δ 13 C value. In this work, four hydroxyl groups from two molecules of MBA react with four hydroxyl groups of 2-methyltetrol and eliminate four molecules of water. No other carboncontaining bonds, except C-O bonds of 2-methyltetrols, are involved in the reaction. The difference between measured and calculated δ 13 C values of methylboronic derivatives ranged from -0.10 to 0.29‰ (Table 1). Accuracy was well within the isotope technical specification (±0.5‰). It should be pointed out that the analytical error of the calculated data for underivatized 2-methyltetrol (usually expressed as the standard deviation, S) could be calculated by the following equation: 2 S2-methyltetrol ) (1/f2-methyltetrol ) 2 2 Smethylboronate + (fMBA /f2-methyltetrol ) 2 2 SMBA where fMBA and f2-methyltetrol are the same as in eq 1 and S2-methyltetrol, SMBA, and Smethylboronate are the analytical standard deviations of (24) Rieley, G. Analyst 1994, 119, 915–919. 6768 Analytical Chemistry, Vol. 82, No. 16, August 15, 2010 (2) 2-methyltetrols, MBA, and methylboronates, respectively. In this work, SMBA was 0.06‰ and Smethylboronate was 0.17 ± 0.04‰ (0.15-0.22‰). According to eq 2, the standard deviation of the measured δ 13 C value of 2-methyltetrol ranged from 0.21 to 0.31‰. The results imply that the method is promising and introduces no isotopic fractionation in the derivatization process, as confirmed by Table 1. The stable carbon isotopic determination exhibited high precision and good reproducibility. On the other hand, precursor isoprene was approximately 6.12-7.86‰ more enriched in 13 C than 2-methyltetrols (Table 1). This might reflect isotope fractionation during the photochemical oxidation reaction. Rudolph et al. 12 reported that the stable carbon isotope fractionation for the reaction of isoprene with OH radicals in the gas phase was 6.94 ± 0.80‰, very similar to the value in this work. To fully evaluate the usefulness of relating precursor isoprene δ 13 C values to those measured in aerosol, one must investigate the potential for the primary kinetic isotope effect (KIE) involving the carbon-carbon bond cleavage products (such as methylglyceric acid, glyoxal, and methylglyoxal) to influence the δ 13 C value of 2-methyltetrols. This is especially true since the reaction pathways for formation of 2-methyltetrols remain unclear. Gas-phase and mixed-phase mechanisms involving the aqueous aerosol phase have been considered. 1-3 Measurements of Atmospheric Samples. The target compounds in samples were well-separated (Figure 3), while the 2-methylerythritol derivative gave rise to double peaks, due to the
Table 2. Concentrations and Stable Carbon Isotopic Compositions of 2-Methyltetrols at Two Forested Sites sampling site sampling date concentration of 2-methyltetrols (ng/m 3 ) measured methylboronates b formation of both E and Z isomers during the reaction. From our previous work, 18 the erythro form of tetrols, erythritol, eluted earlier than the threo form, threitol. Under the same conditions, peaks 1 and 2 were identified as (Z)- and (E)-2-methylerythritol-MBA derivatives, respectively, while peak 3 was the 2-methylthreitol-MBA derivative. The latter derivative gives rise to only one tiny peak, due to the stereo hindrance of the 2-methyl group. The δ 13 C value of the 2-methyltetrol-MBA derivatives was obtained by defining these three peaks as one using the integral tools of IRMS. It could be seen from Table 2 that δ 13 C values of 2-methyltetrols were distinctly different for the two sites. It has been documented that there were significant differences in carbon isotope ratios among C3, C4, and CAM plants, e.g., -35 to -23‰ for C3 with an average of -26‰, -14 to -10‰ for C4 with an average of -13‰, and intermediate carbon isotope compositions for CAM. 25 The δ 13 C of 2-methyltetrols might reveal the relation of atmospheric aerosol with the vegetation types and be used as an indicator of proportions of C3 to C4 plants in vegetation. CONCLUSIONS The stable carbon isotope compositions of 2-methyltetrols, biomarker compounds of isoprene in atmospheric aerosols, were determined by GC/C/IRMS. MBA was used as the derivatization reagent which allows only 29% contribution of the analyzed C. The δ 13 C values of 2-methyltetrols are calculated on the basis of the stoichiometric mass balance equation among 2-methyltetrols, methylboronic acid, and methylboronate derivatives. Excellent reproducibility and accuracy are achieved without carbon isotopic fractionation. Moreover, photosynthesis of 2-methyltetrols through photochemical oxidation of isoprene (25) Cerling, T. E.; Wang, Y.; Quade, J. Nature 1993, 361, 344–345. is introduced. The δ 13 C values of atmospheric 2-methyltetrols were determined for two forest aerosols. Considering the complex formation pathways of 2-methyltetrols, this technique will be helpful for full field application and will have potential in differentiation between homogeneous and heterogeneous oxidation processes. The application of this method may provide additional information about the sources and sinks of atmospheric isoprene. Further experiments on photochemical oxidation in a smog chamber are warranted. ACKNOWLEDGMENT This work was funded by the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant kzcx2-yw-139), the Natural Science Foundation of China (Grants 20677036, 20877051, and 40873073), the Innovation Program of Shanghai Municipal Education Commission (10YZ08), the Shanghai Municipal Health Bureau (054088), Shanghai Leading Academic Disciplines (S30109), and the Scientific Research Foundation for Returned Overseas Chinese Scholars, State Education Ministry, China. We thank the anonymous referee for insightful comments. We also thank Dr. Jia Wanglu (State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences) for his technical assistance. SUPPORTING INFORMATION AVAILABLE δ 13 C values (‰) of the Indiana reference n-alkanes measured by GC/C/IRMS (Isoprime) (Table 1S) and δ 13 C values of the reference materials of CH4 and carbon black (Table 2S). This material is available free of charge via the Internet at http://pubs.acs.org. Received for review January 25, 2010. Accepted April 19, 2010. AC100214P δ 13 C a calculated 2-MT c Changbai July 27, 2007 76.29 -24.27 ± 0.13 (n ) 3) -24.00 ± 0.18 July 28, 2007 108.8 -24.79 ± 0.61 (n ) 3) -24.73 ± 0.86 Dinghu August 1, 2006 65.30 -27.29 ± 0.10 (n ) 3) -28.22 ± 0.14 August 2, 2006 83.54 -26.93 ± 0.46 (n ) 3) -26.99 ± 0.64 a Stable carbon isotopic compositions reported in per mil relative to PDB. b Arithmetic means and standard deviations. Derivatized by methylboronic acid with a δ 13 C value of -24.96 ± 0.06‰ (eight measurements) determined by EA/IRMS. δ 13 C values determined by GC/C/IRMS. c Arithmetic means of calculated δ 13 C values based on mass balance relationship eq 1 and standard deviations (S) calculated according to eq 2. Analytical Chemistry, Vol. 82, No. 16, August 15, 2010 6769
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 and 20: in channels with either no grooves
Page 21 and 22: indicators of atmospheric processin
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Page 27 and 28: on a substrate are preferred. 20-24
Page 29 and 30: Figure 4. SERS analysis of NAADP co
Page 31 and 32: Anal. Chem. 2010, 82, 6775-6781 Hig
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
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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
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Page 71 and 72: carbon black and RP-C18 for the ext
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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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