有机碳已成为多目标地球化学调查、 土地质量地球化学调查等项目研究的必测指标, 对有机碳的准确定量是地球化学调查工作的重要内容, 准确测定有机碳含量具有重要意义。 然而传统的重量法、 容量法流程长、 速度慢, 已经不能满足大批量及快速测定地球化学样品的要求。 采用稀盐酸去除样品中的无机碳, 应用高频红外碳硫分析仪对不同类型地球化学样品中有机碳的测定进行了研究, 着重从称样量、 酸的选择、 最佳浓度及用量、 助熔剂的选择和最佳加入量进行对比实验, 优化出适合分析地球化学样品中有机碳含量的条件, 并采用国家一级地球化学标准物质建立校准曲线, 建立盐酸预处理-红外吸收光谱法测定地球化学样品中有机碳含量的分析方法。 结果表明: 陶瓷坩埚经1 200 ℃灼烧处理可以有效降低碳空白, 减小对分析结果的影响; 选择50.0～70.0 mg称样量, 测试准确度高且样品熔融时不易喷溅; 0.40～0.60 mL稀盐酸（1+7）除尽样品中的无机碳同时减少有机碳流失损失; 0.40～0.50 g纯铁屑和1.50～1.70 g钨粒作为助熔剂, 助熔效果稳定; 采用国家一级地球化学标准物质建立校准曲线, 校准曲线线性良好（R2=0.998 5）。 该方法的检出限为69 μg·g-1, 测定结果的相对标准偏差（RSD, n=12）均小于8%。 经63个不同类型国家一级地球化学标准物质（土壤、 岩石、 水系沉积物）验证, 测定结果与标准值相符。 本方法操作简便, 检出限低, 灵敏度高, 结果准确可靠, 适用于地球化学样品中有机碳含量的测定。

Organic carbon is one of the indispensable indexes in multi-target geochemical surveys, land quality geochemical surveys and other project studies. Accurate quantification of organic carbon is an important part of the geochemical survey with great significance. However, the traditional gravimetric method and volumetric method have long processes and slow speed, which can no longer meet the requirements of large-scale and rapid determination of geochemical samples. In this paper, dilute hydrochloric acid was used to remove inorganic carbon in the samples, and a high-frequency infrared carbon-sulfur analyzer was used to determine the organic carbon in different types of geochemical samples. This paper optimized the conditions such as the sample weight, the choice of acids and fluxes and their optimal concentration and dosage by the comparative experiments. Additionally, the first-level geochemical reference materials also are utilized to establish the calibration curve. A hydrochloric acid pretreatment-infrared absorption spectrometry analysis method of organic carbonin geochemical samples was established by this paper. The experiments showed that the blank value of ceramic crucible could be reduced by burning at 1 200 ℃, which could reduce the impact on the results. The test accuracy was high when choosing the sample weight of 50.0～70.0 mg, and solving the problem of the splash when melting. 0.40～0.60 mL dilute hydrochloric acid (1+7) was chosen as it can remove the inorganic carbon and reduce the loss of organic carbon. The results also showed that the fluxing action was preferably when 0.40～0.50 g pure iron filings and 1.50～1.70 g tungsten particles were used as the mixed flux. The calibration curve of organic carbon established by national geochemical standard reference materials showed good linearity (R2=0.998 5). The detection limit of this method is 69 μg·g-1, and the relative standard deviations (RSD, n=12) of the measurement results is less than 8%. This method has been verified by 63 different types of national geochemical standard reference materials (soil, rock, and sediments), and the results are consistent with the standard values. The method provides the advantages of convenient operation with low detection limits, high sensitivity, and reliable results. It is believed that this method is suitable for the determination of organic carbon in geochemical samples.