挥发性有机物混合标准气体的配制

Preparation of standard mixture of volatile organic compounds

介绍一种简单、易操作、方便、灵活的配制标准有机气体混合物装置。以恒定压力作用在挥发性有机物混合液液面上，液体以恒定流速穿过一根长毛细管流出，由此制成标准发生源，流速的平均相对标准差为３．０％。将毛细管出口插入零空气流中，使液体挥发并混匀，以配成恒定浓度的有机物混合气体，改变发生源压力及稀释气流量即可改变混合气浓度，用气相色谱法测定浓度值，混合气浓度的平均相对标准差为５．７％，绝对误差±８％。比较实测值与计算值，两者无显著性差异。

This article presented a simple,convenient and flexible device for the preparation of standard mixtures of VOCs.By the aid of a constant pressure on the surface of a liquid with specific composition of VOCs,the liquid passed through a long capillary tube at a definite flow rate.A standard VOCs source was thus formed.The mean relative standdard deviation (RSD) of flow rate was 3%.As the outlet of capillary tube inserted in a stream of zero air,the components of liquid vaporized and eventually became a homogeneous gas mixture.The concentration of VOCs in the mixture varied with the pressure applied and the flow rate of dilution air.The mean RSD of concentration of total VOCs in the standard mixture determined by GC method was 5 7%,and the absolute error was 8%.No significent difference was found between the determined and calculated concentrations of the mixture.This method is suitable for preparation of standard mixtures of VOCs with boiling points lower than 150℃.