Work Environment Toxicology, Institute of Environmental Medicine, Karolinska Institutet, SE-171 77 Stockholm, Sweden.
J Appl Toxicol. 2010 Jan;30(1):59-62. doi: 10.1002/jat.1473.
Blood-air and tissue-blood coefficients (lambda) are essential to characterize the uptake and disposition of volatile substances, e.g. by physiologically based pharmacokinetic (PBPK) modelling. Highly volatile chemicals, including many hydrofluorocarbons (HFC) have low solubility in liquid media. These characteristics pose challenges for determining lambda values. A modified head-space vial equilibrium method was used to determine lambda values for five widely used HFCs. The method is based on automated head-space gas chromatography and injection of equal amount of chemical in two head-space vials with identical air phase volumes but different volumes of the liquid phase. The liquids used were water (physiological saline), fresh human blood, and olive oil. The average lambda values (n = 8) were as follows: 1,1-difluoroethane (HFC152a) - 1.08 (blood-air), 1.11 (water-air) and 5.6 (oil-air); 1,1,1-trifluoroethane (HFC143a) - 0.15, 0.15 and 1.90; 1,1,1,2-tetrafluoroethane (HFC134a) - 0.36, 0.35 and 3.5; 1,1,1,2,2-pentafluoroethane (HFC125) - 0.083, 0.074 and 1.71; and 1,1,1,3,3-pentafluoropropane (HFC245fa) - 0.62, 0.58 and 12.1. The lambda values appeared to be concentration-independent in the investigated range (2-200 ppm). In spite of the low lambda values, the method errors were modest, with coefficients of variation of 9, 11 and 10% for water, blood and oil, respectively.
血-气和组织-血分配系数（lambda）对于描述挥发性物质的摄取和分布至关重要，例如通过生理基础药代动力学（PBPK）建模。高度挥发性的化学物质，包括许多氢氟碳化合物（HFC），在液体介质中的溶解度较低。这些特性给 lambda 值的确定带来了挑战。本文采用改良的顶空瓶平衡法来测定五种广泛使用的 HFC 的 lambda 值。该方法基于自动化顶空气相色谱法，将等量的化学物质注入两个顶空瓶中，两个顶空瓶的气相体积相同，但液相体积不同。所用的液体为水（生理盐水）、新鲜人血和橄榄油。8 次重复实验的平均 lambda 值（n=8）如下：1,1-二氟乙烷（HFC152a）-1.08（血-气）、1.11（水-气）和 5.6（油-气）；1,1,1-三氟乙烷（HFC143a）-0.15、0.15 和 1.90；1,1,1,2-四氟乙烷（HFC134a）-0.36、0.35 和 3.5；1,1,1,2,2-五氟乙烷（HFC125）-0.083、0.074 和 1.71；和 1,1,1,3,3-五氟丙烷（HFC245fa）-0.62、0.58 和 12.1。在所研究的浓度范围内（2-200 ppm），lambda 值似乎与浓度无关。尽管 lambda 值较低，但该方法的误差适中，水、血和油的变异系数分别为 9%、11%和 10%。
