UV-Vis spectrophotometric determination of isoprene in atmosphere based on Diels–Alder reaction
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Isoprene is the most abundant biogenic volatile organic compound in the atmosphere. Till now, chromatography is the main detection method for isoprene, dependent on sophisticated instruments and complex operations. An UV-Vis spectrophotometric method based on the Diels–Alder (D-A) reaction was developed to detect isoprene in the atmosphere. The fast D-A reaction between the probe 4-phenyl−1,2,4-triazolin−3,5-dione (PTAD) and isoprene may cause absorbance decrease, which enable it to detect isoprene in solution at 118 nmol·L−1 level. Further, isoprene in air at the level of ppbv was detected using this method. Compared with chromatography this method has the advantages of low cost, fast and less dependence on instrument.Keywords:
Isoprene
Absorbance
Volatile organic compound
Claeys questions whether gaseous epoxydiol is formed from the oxidation of isoprene and whether it is relevant to the formation of isoprene-derived secondary organic aerosol (iSOA). We argue that the alternative mechanism she proposes for iSOA applies primarily to chamber studies with high isoprene and is not as important in the atmosphere, where isoprene concentrations are much lower.
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Volatile organic compound
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Flame ionization detector
Volatile organic compound
Repeatability
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The VOCs emissions from plants are mainly isoprene and monoterpenes, which account for 2/3 of the total emissions from biosphere. 23 kinds of typical plants in Beijing area were screened to estimate the emission rates of isoprene and monoterpenes by adopting a bag-enclosure sampling method followed by a GC-FID analysis. It was found that such deciduous trees as Sophora japnica and Salix babyloniaca etc. were mainly emitting isoprene and coniferous trees as Pinus tabulaetormis mainly released monoterpenes. The study also showed that the emission of isoprene were affected by both temperature and Photosynthetic Active Radiation (PAR), while monoterpene emissions were mainly temperature-dependent.
Isoprene
Volatile organic compound
Monoterpene
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Gas-phase organic acids are ubiquitous throughout the atmosphere and are tracers for volatile organic compound oxidation, although their abundance and sources are poorly characterized. Several studies have pointed to the oxidation of isoprene and monoterpenes as major sources of formic and acetic acids. Here, we quantify >100 gas-phase organic acids produced from isoprene and α-pinene oxidation in a series of laboratory chamber experiments. Overall, gas-phase organic acids constitute 1–28% of the initial organic carbon reacted in the experiments. Isoprene is a precursor for detected organic acids in amounts at least 2–3× greater than α-pinene from OH oxidation. We compare laboratory observations with two summertime field sites—one dominated by isoprene emissions (Southern Oxidant and Aerosol Study—SOAS) and one by monoterpene emissions (Seasonal Particles in Forests Flux studY—SPiFFY). Daytime organic acid mixing ratios were 4× higher at SOAS than SPiFFY, likely because of the substantial isoprene OH oxidation. In contrast to SOAS, factor analysis reveals separate daytime and nighttime organic acid sources at SPiFFY not obviously originating from photochemical oxidation. When available, isoprene is likely a dominant precursor for gas-phase organic acids.
Isoprene
Volatile organic compound
Monoterpene
Organic acid
Pinene
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Abstract By means of ozone degradation experiments it has been shown that the isoprene units in copolymers of isoprene and isobutylene unite in the 1,4 positions. This conclusion is based on negative evidence. Since no evidence was found that would indicate a tendency for the isoprene units to occur in sequences, it is concluded that one isoprene unit cannot exert any directing influence on another, as far as their relative positions along the polymer chain are concerned. The existence of such an influence would necessitate the assumption of unprecedented long-range forces. Hence, the isoprene units must enter the chain in a random manner.
Isoprene
Isobutylene
Chain (unit)
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Natural volatile organic compound (VOC) emissions were investigated at two forested sites in the southeastern United States. A variety of VOC compounds including methanol, 2‐methyl‐3‐buten‐2‐ol, 6‐methyl‐5‐hepten‐2‐one, isoprene and 15 monoterpenes were emitted from vegetation at these sites. Diurnal variations in VOC emissions were observed and related to light and temperature. Variations in isoprene emission from individual branches are well correlated with light intensity and leaf temperature while variations in monoterpene emissions can be explained by variations in leaf temperature alone. Isoprene emission rates for individual leaves tend to be about 75% higher than branch average emission rates due to shading on the lower leaves of a branch. Average daytime mixing ratios of 13.8 and 6.6 ppbv C isoprene and 5.0 and 4.5 ppbv C monoterpenes were observed at heights between 40 m and 1 km above ground level the two sites. Isoprene and monoterpenes account for 30% to 40% of the total carbon in the ambient non‐methane VOC quantified in the mixed layer at these sites and over 90% of the VOC reactivity with OH. Ambient mixing ratios were used to estimate isoprene and monoterpene fluxes by applying box model and mixed‐layer gradient techniques. Although the two techniques estimate fluxes averaged over different spatial scales, the average fluxes calculated by the two techniques agree within a factor of two. The ambient mixing ratios were used to evaluate a biogenic VOC emission model that uses field measurements of plant species composition, remotely sensed vegetation distributions, leaf level emission potentials determined from vegetation enclosures, and light and temperature dependent emission activity factors. Emissions estimated for a temperature of 30°C and above canopy photosynthetically active radiation flux of 1000 μmol m −2 s −1 are around 4 mg C m −2 h −1 of isoprene and 0.7 mg C m −2 h −1 of monoterpenes at the ROSE site in western Alabama and 3 mg C m −2 h −1 of isoprene and 0.5 mg C m −2 h −1 of monoterpenes at the SOS‐M site in eastern Georgia. Isoprene and monoterpene emissions based on land characteristics data and emission enclosure measurements are within a factor of two of estimates based on ambient measurements in most cases. This represents reasonable agreement due to the large uncertainties associated with these models and because the observed differences are at least partially due to differences in the size and location of the source region (“flux footprint”) associated with each flux estimate.
Isoprene
Monoterpene
Volatile organic compound
Mixing ratio
Diurnal cycle
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Abstract Isoprene was dimerised by lithium naphthalene to linear isoprene dimer, a mixture of 2,6‐dimethyl‐2,6‐octadiene and 2,7‐dimethyl‐2,6‐octadiene, in 80% yield.
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The estimation of a biogenic volatile organic compound (BVOC, especially isoprene) and the influence of isoprene emissions on ozone concentrations in the Greater Busan Area (GBA) were carried out based on a numerical modeling approach during a high ozone episode. The BVOC emissions were estimated using a biogenic emission information system (BEIS v3.14) with vegetation data provided by the forest geographical information system (FGIS), land use data provided by the environmental geographical information system (EGIS), and meteorological data simulated by the MM5. Ozone simulation was performed by two sets of simulation scenarios: (1) without (CASE1) and (2) with isoprene emissions (CASE2). The isoprene emission (82 ton $day^{-1}$ ) in the GBA was estimated to be the most dominant BVOC followed by methanol (56) and carbon monoxide (28). Largest impacts of isoprene emissions on the ozone concentrations (CASE2-CASE1) were predicted to be about 4 ppb in inland locations where a high isoprene was emitted and to be about 2 ppb in the downwind and/or convergence regions of wind due to both the photochemical reaction of ozone precursors (e.g., high isoprene emissions) and meteorological conditions (e.g., local transport).
Isoprene
Volatile organic compound
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This paper mainly discussed the application of isoprene in fine chemicals.The dimerization of isoprene and techniques of the isoprene derivatives were presented.Some suggestions for the development of isoprene were given to the plants which produce isoprene with extraction-distillation
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