天然气.用气相色谱法测定规定的不确定度的组分.第6部分:用三个毛细管柱测定氢、氦、氧、氮、二氧化碳和C1到C8的烃类

[中文适用范围]： ISO 6974的这一部分描述了使用三个毛细管柱定量测定天然气样品中氢、氦、氧、氮、二氧化碳和C1至C8烃含量的气相色谱方法。 它适用于分析含有表 1 给出的摩尔分数范围内的成分的气体，并且通常用于实验室应用。 这些范围并不代表检测限，而是代表该方法所规定的精度所适用的限制。 尽管样品中的一种或多种成分可能无法以可检测的水平存在，但该方法仍然适用。 ISO 6974 的这一部分仅在与 ISO 6974 的第 1 部分和第 2 部分结合使用时才适用。 该方法也可适用于天然气替代品的分析。 注：相关时还给出了关于本方法在确定天然气替代品方面的适用性的附加信息。 [外文原描述]： ISO 6974-6:2002 describes a gas chromatographic method for the quantitative determination of the content of helium, hydrogen, oxygen, nitrogen, carbon dioxide and C 1 to C 8 hydrocarbons in natural gas samples using three capillary columns. This method is applicable to the determination of these gases within the mole fraction ranges varying from 0,000 1 % to 40 %, depending on the component analysed, and is commonly used for laboratory applications. However, it is only applicable to methane within the mole fraction range of 40 % to 100 %. These ranges do not represent the limits of detection, but the limits within which the stated precision of the method applies. Although one or more components in a sample may not be present at detectable levels, the method can still be applicable. ISO 6974-6:2002 is only applicable if used in conjunction with ISO 6974-1:2000 and ISO 6974-2:2001. This method can also be applicable to the analysis of natural gas substitutes. Additional information on the applicability of this method to the determination of natural gas substitutes is also given where relevant.