Abstract

An ultra-sensitive modified catalytic spectrophotometric method for vanadium determination in lubricating oils was developed. The method was based on catalytic effect of vanadium(V) on N,N-diethyl-p-phenylenediamine (DPD) oxidation by bromate. The oxidized product was spectrophotometrically measured at 550 nm after 30 min from starting the reaction. Thirty activators at different concentrations were examined to obtain the maximum sensitivity. 5-sulfosalicylic acid in the presence of citric acid recorded ultra-sensitivity with limits of detection and quantification of 5 and 17 pg/mL, respectively. These levels allow for direct determination of vanadium with no need of preconcentration approaches. The optimum concentrations (mmol/L) were as follows: 1.50 DPD, 40 bromate, 4.0 5-sulfosalicylic acid, and 60 citric acid. Excellent linearity, with a correlation coefficient of 0.9998, was obtained in the range of 0.02–0.50 ng/mL. The method was also precise with relative standard deviations of intra- and inter-day precision of 1.6 and 2.6%, respectively. The method was applied to different lubricating oil samples. The mean concentrations (ng/mL) and standard deviation (n = 3) values for virgin engine, hydraulic, and gear oils were 19.7 ± 0.27, 4.175 ± 0.175, and 10.085 ± 0.16, respectively, while those for used engine and gear oils were 599.77 ± 5.39 and 60.34 ± 2.18, respectively. The range of recovery values of vanadium in oil samples, which were obtained from spiking in all samples, were 100.1–103.8% indicating good accuracy.

中文翻译：

---

建立超灵敏催化光度法测定初榨和废润滑油中的钒

摘要

建立了一种超灵敏的改进催化光度法测定润滑油中钒。该方法基于钒（V）对N，N-二乙基-p的催化作用-苯二胺（DPD）被溴酸盐氧化。从反应开始30分钟后，在550nm下用分光光度法测量氧化产物。检查了三十种不同浓度的活化剂以获得最大灵敏度。在柠檬酸存在下的5-磺基水杨酸记录超灵敏性，其检测和定量极限分别为5 pg / mL和17 pg / mL。这些水平无需直接浓缩即可直接测定钒。最佳浓度（mmol / L）如下：1.50 DPD，40溴酸盐，4.0 5-磺基水杨酸和60柠檬酸。在0.02–0.50 ng / mL的范围内获得了出色的线性，相关系数为0.9998。该方法也很精确，日内和日间相对精度的标准偏差为1.6和2.6％，分别。该方法适用于不同的润滑油样品。平均浓度（ng / mL）和标准偏差（n = 3）原始机油，液压油和齿轮油的值分别为19.7±0.27、4.175±0.175和10.085±0.16，而用过的发动机油和齿轮油的值分别为599.77±5.39和60.34±2.18。通过加标所有样品获得的石油样品中钒的回收值范围为100.1-10.38％，这表明准确性很高。