1.1 这些试验方法包括使用毛细管气相色谱法分离这些酸的挥发性甲酯，测定分馏塔尔油产品中单个脂肪酸和松香酸的含量。 1.2 描述了形成甲酯的四种方法，以及测定单个脂肪酸和松香酸含量的两种方法。 1.2.1 形成甲酯的经典方法是使用重氮甲烷，但重氮甲烷是一种危险有毒物质，因此不再是首选试剂。 重氮甲烷的使用详见附录。甲酯可通过使用四甲基氢氧化铵（TMAH）、三甲基苯基氢氧化铵（TMPAH）或N，N-二甲基甲酰胺二甲基缩醛（DMF-DMA）形成。 1.2.2 测定单个脂肪酸和松香酸含量的两种方法是“内标”法（产生绝对值）和“面积百分比”法（产生相对值）。 1.3 本标准并非旨在解决与其使用相关的所有安全问题（如有）。 本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.4 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 3.1 从塔尔油中提取的塔尔油分馏产品是重要的商业材料，主要由脂肪酸和松香酸组成，但也含有一些中性物质（见术语 D804 ). 对于许多应用，有必要了解这些产品中存在的单个脂肪酸和松香酸的水平。气相色谱法已被证明是此类测定的有用工具（见试验方法 D509 )这些试验方法中描述的毛细管色谱法被认为是目前可用的最有效的气相色谱技术。在特定情况下，其他技术可能比气相色谱法更合适。例如，样品中脂肪酸酯的存在将导致衍生步骤中的酯交换，这可能会影响结果。 3.2 由于氢键作用，未经改性的塔尔油脂肪酸和松香酸在大气压下不能挥发而不分解。因此，在色谱分离之前，有必要将游离酸转化为更易挥发和更稳定的甲酯。 3.3 这些试验方法描述了制备甲酯的四种方法。经典方法是通过使用重氮甲烷，但重氮甲烷是一种危险有毒物质，因此不再是首选药剂。重氮甲烷的使用详见 附录X1 . 3.3.1 TMAH即使稍微过量使用，也会导致样品的双不饱和脂肪酸和多不饱和脂肪酸异构化。这导致单个脂肪酸成分的结果不准确。TMAH应用于仅含有松香酸的材料，或当单个脂肪酸成分的识别或定量不重要时。 3.3.2 当需要识别或定量单个双不饱和脂肪酸和多不饱和脂肪酸时，TMPAH是推荐的甲基化剂。TMPAH产生的结果与重氮甲烷非常相似，但没有与重氮甲烷相关的危险。 大量过量的TMPAH可能会导致共轭化合物的异构化，与TMAH类似。 3.3.3 DMF-DMA的结果与TMPAH相当，使用简单安全。然而，该试剂对水分敏感，要求样品中没有任何明显的水分。 3.4 这些试验方法包括两种计算单个脂肪酸和松香酸甲酯含量的试验方法。当需要给定化合物的实际重量百分比时，必须使用“内标”方法。该方法涉及将已知量的内标物添加到已知量的试验材料中，并将与内标物相关的峰面积与单个脂肪酸或松香酸甲酯的峰面积进行比较。 “面积百分比”方法将通过将适当峰的面积与所有峰的总面积进行比较，得出每个成分的相对量。非洗脱化合物将导致该方法的错误（绝对）结果。 甲酯的制备 注1: 可以使用这三种方法中的任何一种，选择取决于中提到的因素 3.3 .

1.1 These test methods cover the determination of the amounts of the individual fatty acids and rosin acids in fractionated tall oil products, using capillary gas chromatographic separation of the volatile methyl esters of these acids. 1.2 Four methods for forming the methyl esters, and two methods for determining the amounts of the individual fatty acids and rosin acids are described. 1.2.1 The classic method for the formation of methyl esters is through the use of diazomethane, but diazomethane is a hazardous and toxic material, and so is no longer the preferred reagent. The use of diazomethane is detailed in the Appendix. Methyl esters may be formed through the use of tetramethylammonium hydroxide (TMAH), trimethylphenylammonium hydroxide (TMPAH), or N,N-dimethylformamide dimethyl acetal (DMF-DMA). 1.2.2 The two methods for determining the amount of the individual fatty acids and rosin acids are the “internal standard” method, which yields absolute values, and the “area percent” method, which yields relative values. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 3.1 Tall oil fractionated products derived from tall oil are important commercial materials, primarily composed of fatty acids and rosin acids, but also containing some neutral material (see Terminology D804 ). For many applications, it is necessary to know the level of the individual fatty acids and rosin acids present in these products. Gas chromatography has proven to be a useful tool for such determinations (see Test Methods D509 ), and capillary chromatography, described in these test methods, is considered to be the most effective gas chromatographic technique currently available. In particular situations, other techniques may be more suitable than gas chromatography. For example, the presence of fatty acid esters in the sample would result in transesterification during the derivatization step that may affect the results. 3.2 Due to hydrogen bonding, unmodified tall oil fatty acids and rosin acids cannot be volatilized at atmospheric pressure without undergoing decomposition. So, it is necessary to convert the free acids to the more volatile and more stable methyl esters, prior to chromatographic separation. 3.3 These test methods describe four ways to prepare methyl esters. The classic method is through the use of diazomethane, but diazomethane is a hazardous and toxic material, and so is no longer the preferred agent. The use of diazomethane is detailed in Appendix X1 . 3.3.1 TMAH causes isomerization of a sample’s di- and polyunsaturated fatty acids, when it is used in even a slight excess. This leads to inaccurate results for the individual fatty acid components. TMAH should be used for materials containing only rosin acids, or when the identification or quantitation of individual fatty acid components is not important. 3.3.2 TMPAH is the recommended methylating agent when the identification or quantitation of individual di- and polyunsaturated fatty acids is required. TMPAH produces results that are very similar to those of diazomethane, but without the hazards that are associated with diazomethane. A considerable excess of TMPAH may cause isomerization of conjugated compounds similar to that encountered with TMAH. 3.3.3 DMF-DMA gives results comparable to TMPAH and is easy and safe to use. However, the reagent is moisture sensitive, requiring samples to be free of any significant levels of water. 3.4 Two test methods for calculating the amounts of the individual fatty acid and rosin acid methyl esters are included in these test methods. When the actual weight percentage of a given compound is required, the “internal standard” method must be used. This method involves adding a known amount of an internal standard to a known amount of test material, and comparing the area of the peak associated with the internal standard with the area of the peak of the individual fatty acid or rosin acid methyl esters. The “area percent” method will give the relative amount of each component, by comparing the area of the appropriate peak to the total area of all peaks. Non-eluting compounds will lead to erroneous (absolute) results with this method. PREPARATION OF METHYL ESTERS Note 1: Any of these three methods can be used, with the choice being dependent on the factors mentioned in 3.3 .