The ability to accurately determine the metal content of crude oils is necessary for reasons ranging from the need to identify the source of the oils (Ni and V) to removing components that might inhibit catalysis during refining or impact negatively on the environment during hydrocarbon combustion. Here we show that ashing followed by chemical oxidation and acid digestion, coupled with ICP-MS analysis, provides an accurate method for determining the concentration of metals in crude oil. Nickel and vanadium concentrations were measured in certified Ni and V oil standards and in various light, intermediate and heavy crude oils after application of a single vessel ashing-chemical oxidation-acid digestion sample preparation and storing technique. Prior to the ashing, chemical oxidation and acid digestion, an aliquot of the crude oil was placed in a 10 ml Pyrex™ culture tube and capped with quartz wool. The capped culture tubes were then subjected to thermal combustion, followed by chemical oxidation and leaching. The leachates and the aqueous standards were diluted and analyzed for their Ni and V contents using inductively coupled plasma mass spectrometry (ICP-MS). The measured concentrations of Ni in oil standards, reported to contain 1, 100, and 1000 mg kg-1 Ni (±2% error), were 1.1 ± 0.01, 99.8 ± 1.46, and 1025 ± 24 mg kg-1 respectively. The corresponding concentrations of V in these standards, reported to contain 2, 100, and 1000 mg kg-1 V, were measured to be 1.93 ± 0.06, 104 ± 1.3, and 1027 ± 7.5 mg kg-1, respectively. Crude oil samples, A, B, C, D and E, that varied significantly in their composition, and ranged from light to heavy, were determined to contain 5.59 ± 0.32, 4.05 ± 0.03, 6.22 ± 0.22, 33.8 ± 0.7 and 41.6 ± 3.5 mg kg-1 Ni, respectively. Their V contents were determined to be 11.98 ± 0.1, 12.2 ± 0.1, 16.5 ± 0.4, 34.7 ± 0.4, and 104 ± 8.9 mg kg-1, respectively. The results were thus repeatable on average to 4.1% and 2.75% for Ni and V, respectively; the repeatability was worst (∼8.5%) for crude oil E, a heavy (viscous) oil with a very high asphaltene content (27.2%). This modified single vessel ashing-digestion technique (combustion, chemical oxidation, acid leaching and storing) minimizes contamination and significantly reduces the loss of ash. Our results are repeatable, comparable to, and in some cases superior to those of other methods. The method is applicable to a wide range of crude oil compositions, is very accessible and robust, easy to use, and does not require costly equipment in preparing the samples for analysis by ICP-MS.

中文翻译：

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一种测定原油中镍、钒和其他金属浓度的方法

准确测定原油金属含量的能力是必要的，其原因包括需要确定油类（镍和钒）的来源，以及去除可能在精炼过程中抑制催化作用或在碳氢化合物燃烧过程中对环境产生负面影响的成分。在这里，我们展示了灰化、化学氧化和酸消解，再加上 ICP-MS 分析，提供了一种确定原油中金属浓度的准确方法。在应用单容器灰化-化学氧化-酸消解样品制备和储存技术后，在经认证的 Ni 和 V 油标准以及各种轻质、中质和重质原油中测量镍和钒浓度。在灰化、化学氧化和酸消化之前，将等分的原油置于 10 ml Pyrex™ 培养管中，并用石英棉盖住。然后将加盖的培养管进行热燃烧，然后进行化学氧化和浸出。使用电感耦合等离子体质谱法 (ICP-MS) 对浸出液和水性标准品进行稀释并分析其 Ni 和 V 含量。据报道，油标准品中 Ni 的测量浓度分别为 1、100 和 1000 mg kg-1 Ni（±2% 误差），分别为 1.1 ± 0.01、99.8 ± 1.46 和 1025 ± 24 mg kg-1。这些标准中相应的 V 浓度，据报道含有 2、100 和 1000 mg kg-1 V，测量结果分别为 1.93 ± 0.06、104 ± 1.3 和 1027 ± 7.5 mg kg-1。原油样品 A、B、C、D 和 E，其成分差异很大，从轻到重，分别确定含有 5.59 ± 0.32、4.05 ± 0.03、6.22 ± 0.22、33.8 ± 0.7 和 41.6 ± 3.5 mg kg-1 Ni。它们的 V 含量分别确定为 11.98 ± 0.1、12.2 ± 0.1、16.5 ± 0.4、34.7 ± 0.4 和 104 ± 8.9 mg kg-1。因此，对于 Ni 和 V，结果的平均可重复性分别为 4.1% 和 2.75%；原油 E 的可重复性最差（~8.5%），这是一种沥青质含量非常高（27.2%）的重（粘性）油。这种改进的单容器灰化消化技术（燃烧、化学氧化、酸浸和储存）可最大限度地减少污染并显着减少灰分损失。我们的结果是可重复的、可比的，并且在某些情况下优于其他方法。该方法适用于广泛的原油成分，非常容易获得和稳健，易于使用，