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A reference data set for validating vapor pressure measurement techniques: homologous series of polyethylene glycols

机译：用于验证蒸气压测量技术的参考数据集：同源系列聚乙二醇

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To predict atmospheric partitioning of organic compounds between gas and aerosol particle phase based on explicit models for gas phase chemistry, saturation vapor pressures of the compounds need to be estimated. Estimation methods based on functional group contributions require training sets of compounds with well-established saturation vapor pressures. However, vapor pressures of semivolatile and low-volatility organic molecules at atmospheric temperatures reported in the literature often differ by several orders of magnitude between measurement techniques. These discrepancies exceed the stated uncertainty of each technique which is generally reported to be smaller than a?factor of 2. At present, there is no general reference technique for measuring saturation vapor pressures of atmospherically relevant compounds with low vapor pressures at atmospheric temperatures. To address this problem, we measured vapor pressures with different techniques over a?wide temperature range for intercomparison and to establish a?reliable training set. We determined saturation vapor pressures for the homologous series of polyethylene glycols (H???(O???CHsub2/sub???CHsub2/sub)subn/sub???OH) for in/i?=?3 to in/i?=?8 ranging in vapor pressure at 298?K from 10sup?7/sup to 5×10sup?2/sup?Pa and compare them with quantum chemistry calculations. Such a?homologous series provides a?reference set that covers several orders of magnitude in saturation vapor pressure, allowing a?critical assessment of the lower limits of detection of vapor pressures for the different techniques as well as permitting the identification of potential sources of systematic error. Also, internal consistency within the series allows outlying data to be rejected more easily. Most of the measured vapor pressures agreed within the stated uncertainty range. Deviations mostly occurred for vapor pressure values approaching the lower detection limit of a?technique. The good agreement between the measurement techniques (some of which are sensitive to the mass accommodation coefficient and some not) suggests that the mass accommodation coefficients of the studied compounds are close to unity. The quantum chemistry calculations were about 1 order of magnitude higher than the measurements. We find that extrapolation of vapor pressures from elevated to atmospheric temperatures is permissible over a?range of about 100?K for these compounds, suggesting that measurements should be performed best at temperatures yielding the highest-accuracy data, allowing subsequent extrapolation to atmospheric temperatures.
机译：为了预测基于用于气相化学的显式模型的气体和气溶胶颗粒相之间的有机化合物的大气分配，需要估计化合物的饱和蒸气压力。基于功能群贡献的估计方法需要具有良好饱和蒸气压力的培训套化合物。然而，文献中报道的大气温度下半血管和低挥发性有机分子的蒸气压通常在测量技术之间的几个数量级不同。这些差异超过了每种技术的所述不确定度，通常报道小于a的Δfs2。目前，没有一般参考技术，用于测量大气温度下具有低蒸气压力的大气相关化合物的饱和蒸气压力。为了解决这个问题，我们测量了在宽温度范围内用不同技术测量的蒸汽压力，并建立一个可靠的训练集。我们确定了用于同源蒸汽压力的聚乙二醇系列（H ???（o ??? CH 2 2 Ch 2 ） n ?? OH）对于 n ？=Δ3至 n ？8在蒸汽压力中，在10 αk298Ωk Sup>到5×10 ？2 ？PA并将它们与量子化学计算进行比较。这样的？同源系列提供了一个？参考集，涵盖饱和蒸气压下几个数量级，允许对不同技术的蒸汽压力检测的下限以及允许识别潜在的系统来源错误。此外，该系列内的内部一致性允许更容易地拒绝偏远的数据。大多数测量的蒸汽压力在所述不确定性范围内同意。偏差主要用于蒸汽压力值接近较低的检测限A技术。测量技术之间的良好一致性（其中一些对批量容纳系数敏感，有些没有）表明所研究的化合物的质量容纳系数接近统一。量子化学计算比测量值高约1级。我们发现，对于这些化合物，允许从升高到大气温度的蒸汽压力的外推。对于这些化合物，约为100μk的范围，表明应在产生最高精度数据的温度下最佳地进行测量，从而使随后的外推到大气温度。

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