Analytical Chemistry Chemical Cytometry Quantitates Superoxide

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Table 2. δ 13 C Values for Compounds Emitted from Various Tropical Plants and a Fossil Fuel Combustion Source a sand live oak Quercus geminata orange Citrus sinensis lemon Citrus limon plant type Students’ t test, and the results show that differences between the raw material on the elemental analyzer and the gases on the GC-IRMS system are significant. However, the percent difference between the two procedures is small; less than 9% error exists between the pooled results and those of the raw liquid compounds for all compounds except 2-pentanone, which has an associated error of 14.3%. Source Measurement Results. The δ 13 C results from the automotive exhaust and tropical plants are presented in Table 2. A representative chromatogram from the automotive exhaust sample is shown in the Supporting Information (Figure S-1) and serves as a good example of a complex sample matrix and the system’s peak resolution. We have also incorporated, in some instances, for both source and ambient samples, results for the OVOC acetaldehyde even though analysis of this compound is influenced by a variable artifact background. 9,41 Data for NMHCs, isoprene, benzene, and toluene are made known because they were easily identifiable in the chromatograms and offer a comparison to previously measured NMHCs δ 13 C values. 44-46 In general, a clear distinction exists between plant and fossil fuel emissions, and as would be expected based on the range of δ 13 C values for oils and fuels worldwide, 16,46 fossil fuel derived OVOC emissions were more enriched in 13 C compared to the plant results. Of particular note are the substantially enriched δ 13 C values (-5.0 ± 0.4‰) for ethanol, compared to the other compounds in the fossil fuel combustion experiments. Ethanol, derived from corn, is currently being blended into gasoline in mixtures g10% (v/v). It has been reported that biofuels consume >25% of U.S. corn production and that ethanol constitutes 99% of all biofuels in the United States. 47,48 Utilizing C4 photosynthesis, which discriminates less against 13 C, corn and other C4 plants are generally enriched in the isotope compared to C3 plants. (44) Iannone, R.; Koppmann, R.; Rudolph, J. J. Atmos. Chem. 2007, 58, 181– 202. (45) 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. (46) Rudolph, J.; Czuba, E.; Norman, A. L.; Huang, L.; Ernst, D. Atmos. Environ. 2002, 36, 1173–1181. (47) Barnett, M. O. Environ. Sci. Technol. 2010, 44, 5330-5331. (48) Farrell, A. E.; Plevin, R. J.; Turner, B. T.; Jones, A. D.; O’Hare, M.; Kammen, D. M. Science 2006, 311, 506–508. philodendron Philodendron selloum sea grape Coccoloba uvifera Keppler et al. 33 fossil fuel combustion acetaldehyde -29.9 (2.3) -25.7 (0.1) -22.4 (1.4)* -17.5 (0.5) -30.7 (1.1)* -24.9 (2.2) -20.9 (0.4) methanol -41.9 (3.1) -59.7 (2.9) -37.8 (2.6)* -27.5 (0.5) -30.7 (1.0)* -68.2 (11.2) -16.9 (1.3) ethanol -41.5 (0.8) -37.5 (0.3) -30.6 (0.2) -36.5 (0.2)* -29.4 (2.6) -5.0 (0.4) propanal -25.6 (2.7) isoprene off scale b -26.9 (3.7) -35.2 (3.5) -33.8 (2.6) -23.0 (2.6)* -16.7 (1.2) -32.6 (0.9)* acetone -35.7 (4.1) -37.4 (2.4) -32.8 (1.2) -38.8 (1.1) -29.3 (1.5)* -33.8 (0.8) -31.3 (0.8)* -28.1 (2.5) -25.6 (0.5) 2-pentanone -35.2 (1.4) benzene -26.9 (0.3) toluene -27.5 (0.6) a Also included are values for prepped and incubated biogenic samples from Keppler et al.. 33 All values are reported as the average (standard deviation). All samples n ) 5, except the fossil fuel source where n ) 3. All biogenic samples are wounded/clipped branches, except where noted (*), which represents an intact branch on the sample specimen. The fossil fuel source was collected from a 1972 Scout International with no catalytic converter at a constant cruise. b Isoprene was present; however, it saturated the detectors and the signal response was off scale and the δ 13 C value could not be calculated. 6804 Analytical Chemistry, Vol. 82, No. 16, August 15, 2010 Bulk carbohydrate analyses between the two plant types show an enrichment of ∼15‰ in carbohydrates extracted from C4 plant material. 49 Investigations of industrially produced ethanol originating from corn have been shown to have δ 13 C values of -10.71 ± 0.31‰. 49 The values we observed in the Scout samples are ∼5‰ heavier and, considering the widespread use of ethanol (7.5 billion gallons are expected to be used in fuel by 2012 48 ), may serve as a tracer for transportation related sources to the atmosphere. Some biogenic samples in this study, such as sand live oak and orange citrus, had substantially depleted values for methanol and agree with incubated emissions from various deciduous trees and grasses made by Keppler et al. 33 (Table 2). However, this observation is not consistent across all samples and suggest that variations in δ 13 C values may result from interspecies differences, microbe interaction on the leaf’s surface, prey/injury response, the potential presence of a methanol utilization pathway which oxidizes methanol to formaldehyde and formic acid/formate, 50,51 and other lesser known metabolic, formation, and loss pathways within plants. 52 Finally, a wound response may be observed between the clipped and intact philodendron and sea grape samples. In one distinct case, acetaldehyde emitted from clipped sea grape specimens were enriched by ∼4‰ compared to the fossil fuel emissions. Ambient Measurement Results. Considerable differences in δ 13 C are observed between ambient sampling locations (Table 3). Results from Miami International Airport are reflective of an averaged value for fresh vehicular sources. The measured δ 13 C range for airport samples is between -12.3 ± 3.7‰ (ethanol) to -35.3 ± 1.7‰ (3-pentanone). With the exception of ethanol, which has a δ 13 C value consistent with its C4 plant source, and 2- and 3-pentanone, the measured range at the airport agrees with that established for NMHCs from transportation-related sources by Rudolph, namely, -21.9 to -31.3‰. 25 Our acetaldehyde value is consistent with the range (49) Ishida-Fujii, K.; Goto, S.; Uemura, R.; Yamada, K.; Sato, M.; Yoshida, N. Biosci., Biotechnol., Biochem. 2005, 69, 2193–2199. (50) Cossins, E. A. Can. J. Biochem. 1964, 42, 1793–1802. (51) Gout, E.; Aubert, S.; Bligny, R.; Rebeille, F.; Nonomura, A. R.; Benson, A. A.; Douce, R. Plant Physiol. 2000, 123, 287–296. (52) Fall, R. In Reactive Hydrocarbons in the Atmosphere; Hewitt, C. N., Ed.; Academic Press: San Diego, CA, 1999; pp 43-97.
Table 3. Ambient Measurement Results for Samples Collected from Metropolitan Miami and Everglades National Park a Miami International Airport δ 13 C ± 1σ (‰) Miami Financial District Everglades National Park acetaldehyde -26.7 ± 0.7 -26.8 ± 1.2 -19.0 ± 2.7 methanol -36.3 ± 3.7 ethanol -12.3 ± 3.7 -17.2 ± 4.1 isoprene -30.3 ± 2.1 propanal -28.4 ± 1.5 -26.2 ± 2.4 acetone -31.0 ± 3.5 -26.6 ± 0.4 -23.7 ± 0.4 MEK -28.3 ± 2.1 -25.9 ± 1.9 2-pentanone -34.8 ± 6.5 -29.4 ± 0.1 3-pentanone -35.3 ± 1.7 -37.8 ± 1.8 toluene -33.7 ± 2.0 a Miami International Airport, n ) 5; Miami financial district, n ) 4; Everglades National Park, n ) 3. presented by Wen et al. who measured values via a derivatization procedure of ∼-21.0‰ and ∼-29.2‰ for samples collected at a bus station and petrochemical refinery, respectively. 36 Some observations at Miami’s Financial District are between 2.2 and 4.4‰ enriched in 13 C compared to the same compounds at Miami International Airport, and again we observe an anomalously enriched value for ethanol (-17.2 ± 4.1‰). Samples from the airport are general δ 13 C values we can expect for OVOCs from transportation related sources without addition from other sources and losses caused by solar radiation and reaction with OH. Miami’s Financial District is located within 0.1 mile of Biscayne Bay and 1 mile of the Port of Miami and was dominated by an onshore breeze during the sample collection. Therefore, we can expect values from the financial district to be enriched since the δ 13 C signature for each compound will reflect a combination of vehicular, biogenic, and possibly marine sources and, additionally, losses attributable to reactivity with OH and photolysis. Isotopic values for samples from the financial district are bound within the reported range of -15.8 to -37.4‰ for NMHCs sampled at a moderately polluted waterfront in Wellington, New Zealand. 25 In comparison with automobile exhaust (Table 2), the mean values observed at Miami International Airport and Miami’s financial district are generally depleted in 13 C. The two most obvious differences among these samples that may influence the observations are the fuel source and the presence of a catalytic converter. Emissions collected at the airport are a mix of refined petroleum and diesel, whereas the Scout International was fueled by unleaded gasoline. Furthermore, vehicle emissions at the airport are assumed to be produced by engines having a catalytic converter. However, the Scout lacked a converter, and the speeds of the engines producing the emissions were very different. Traffic through the airport’s lower roadway moved at an idle pace and rarely exceeded 15 mph. The Scout samples were obtained with the engine under significant load and at a constant revolution per minute (2000 rpm) and cruise speed (80 kph). To our knowledge, no studies exist showing how the presence of a catalytic converter or engine speed may influence the δ 13 C of emitted hydrocarbons. Samples from Everglades National Park spanned a large range from -19.0 to -36.3‰. Measured methanol from within the National Park was -36.3 ± 3.7‰, considerably depleted and consistent with other values obtained in the tropical plant enclosure studies (i.e., sand live oak δ13CMethanol )-41.9 ± 3.1‰) and with the results presented earlier from Keppler et al. 33 Similarly, δ13C values for isoprene released from C3 plants range from -26 to -29‰. 45 Isoprene values at the National Park are lighter (-30.3 ± 2.1‰) than the range presented by Rudolph et al. However, when the precision of the measurement is considered, the isoprene values measured from the Everglades’ samples overlap the range observed with that previous work. Acetone and acetaldehyde values from within the National Park are more enriched than anticipated. The mean δ13C values for these compounds are -23.7‰ and -19.0‰, respectively. Each are enriched approximately 7.5‰ compared to samples collected at Miami International Airport and are fairly consistent with samples from Miami’s financial district and fossil fuel combustion. When estimated atmospheric lifetimes (τ) are considered for these compounds in the troposphere for losses caused by OH OH reactivity with OH (τacetone ) 66 days; τacetaldehyde ) 11 h) and hν hν photolysis (τacetone ) 38 days; τacetaldehyde ) 5 days), these observations can be explained, especially for the enrichment of acetaldehyde over acetone (∼5‰). Few studies of ambient δ13C for acetaldehyde exist, 29,36 and only one exists for acetone. 37 For samples collected within a biosphere reserve in China, Guo et al. measured acetaldehyde values between -31.6 and -34.9‰. These values are depleted in 13C compared to our measurements. However, they report weak photolytic loss of formaldehyde in the same study, and considering formaldehyde’s lifetime against photolysis is shorter (4 h) compared to acetaldehyde (5 days), we assume this to be true for acetaldehyde at the same location. Guo et al. used a derivatization method to calculate δ13C values for acetone collected at a forested site (∼-31‰) and at the top of a 10 m building influenced by vehicle emissions (∼-26‰). The acetone values from Everglades National Park are enriched by 2-7‰ compared to the values presented by Guo et al. Isotopic values obtained from the forest may reflect the signature of fresh acetone emissions from biomass, while values for Everglades National Park samples may be more strongly influenced by photochemistry. The measured values for acetone and acetaldehyde from within the Everglades may also indicate contributions from in situ atmospheric production via oxidation and photolysis of higher order hydrocarbons. An exact assessment to separate direct emissions from photochemical production and loss is not possible at this time since fractionations associated with these pathways are not known. CONCLUSIONS A new method for measuring δ 13 C values of low-molecular weight OVOCs from direct sources and ambient samples was developed. The method incorporated a carbon sorbent, a lowvolume capillary reactor, water trap, and balanced working reference gas delivery system. The method’s total precision ranged between 0.6 and 2.9‰, and negligible sample fractionation occurred while sampling and trapping gases. Further testing showed that measured δ 13 C values had little dependence Analytical Chemistry, Vol. 82, No. 16, August 15, 2010 6805
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Anal. Chem. 2010, 82, 6745-6750 Let
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Figure 3. Electropherograms of TPP-
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Anal. Chem. 2010, 82, 6751-6755 Res
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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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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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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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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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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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Analytical Chemistry Chemical Cytometry Quantitates Superoxide

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