Robaina Nicolle F, Feiteira Fernanda N, Cassella Alessandra R, Cassella Ricardo J
Departamento de Química Analítica, Universidade Federal Fluminense, Outeiro de São João Batista s/n, Centro, Niterói/RJ, 24020-141, Brazil.
PETROBRAS, CENPES, PDEDS/QM, Av. Horácio Macedo 950, Ilha do Fundão, Rio de Janeiro/RJ 21941-915, Brazil.
J Chromatogr A. 2016 Aug 5;1458:112-7. doi: 10.1016/j.chroma.2016.06.066. Epub 2016 Jun 21.
The present paper reports on the development of a novel extraction induced by emulsion breaking (EIEB) method for the determination of chloride in crude oils. The proposed method was based on the formation and breaking of oil-in-water emulsions with the samples and the consequential transference of the highly water-soluble chloride to the aqueous phase during emulsion breaking, which was achieved by centrifugation. The determination of chloride in the extracts was performed by ion chromatography (IC) with conductivity detection. Several parameters (oil phase:aqueous phase ratio, crude oil:mineral oil ratio, shaking time and type and concentration of surfactant) that could affect the performance of the method were evaluated. Total extraction of chloride from samples could be achieved when 1.0g of oil phase (0.5g of sample+0.5g of mineral oil) was emulsified in 5mL of a 2.5% (m/v) solution of Triton X-114. The obtained emulsion was shaken for 60min and broken by centrifugation for 5min at 5000rpm. The separated aqueous phase was collected, filtered and diluted before analysis by IC. Under these conditions, the limit of detection was 0.5μgg(-1) NaCl and the limit of quantification was 1.6μgg(-1) NaCl. We applied the method to the determination of chloride in six Brazilian crude oils and the results did not differ statistically from those obtained by the ASTM D6470 method when the paired Student-t-test, at 95% confidence level, was applied.
本文报道了一种用于测定原油中氯离子的新型破乳诱导萃取（EIEB）方法的开发。该方法基于样品与水包油乳液的形成与破乳，以及破乳过程中高水溶性氯离子向水相的转移，这一过程通过离心实现。萃取物中氯离子的测定采用离子色谱（IC）和电导检测法。评估了几个可能影响该方法性能的参数（油相：水相比例、原油：矿物油比例、振荡时间以及表面活性剂的类型和浓度）。当1.0g油相（0.5g样品 + 0.5g矿物油）在5mL 2.5%（m/v）的 Triton X - 114溶液中乳化时，可实现样品中氯离子的完全萃取。所得乳液振荡60min，然后在5000rpm下离心5min破乳。收集分离出的水相，过滤并稀释后进行IC分析。在这些条件下，检测限为0.5μg g⁻¹ NaCl，定量限为1.6μg g⁻¹ NaCl。我们将该方法应用于六种巴西原油中氯离子的测定，当采用95%置信水平的配对学生t检验时，结果与通过ASTM D6470方法获得的结果在统计学上无差异。
