Multi-Element Analysis of Jatropha curcas L. Oil Using Inductively Coupled Plasma Tandem Mass Spectrometry
JIANG Bo1,3, HUANG Jian-hua2*
1. Chongqing Key Laboratory of Characteristic Plant Resource Protection and Utilization in Wuling Mountain Area, Yangtze Normal University, Chongqing 408100，China
2. Institute of Chinese Materia Medica, Hunan Academy of Traditional Chinese Medicine, Changsha 410013, China
3. Collaborative Innovation Center of Green Development for Wuling Mountain Areas, Yangtze Normal University, Chongqing 408100, China
Abstract：According to the development of industrialization and modernization, much more conventional fossil energy resource is excess consumed, with the depletion of non-renewable energy resource, the development of new renewable energy was urgently needed. As one of the hottest concerned biodiesel resources, Jatropha curcas L. oil was thought as the most possible renewable energy to replace conventional fossil energy resource. The trace elements in Jatropha oil might affect the performance of engine, and deteriorate environment. In order to obtain the contents of multi-elements in Jatropha curcas L. oil, an analytical method was established for accurately determination of Si, P, S, Cr and As in Jatropha curcas L. oil by using inductively coupled plasma tandem mass spectrometry (ICP-MS/MS). Jatropha oil was processed by using microwave-assisted acid-digested reaction with nitric acid and hydrogen peroxide. The changes of detection limit (DL) and background equivalent concentration (BEC) for multi-elements in different analysis modes were optimized in detail. In the MS/MS mode, O2 was introduced into the collision reaction cell (CRC), then Si+, P+, S+, Cr+ and As+ were reacted with O2 to generate SiO+2, PO+, SO+, CrO+ and AsO+ respectively; thus mass spectrometry interference can be eliminated by mass shift caused by reactions. As Cl+ can reaction with H2 to form ClH+2, while Na+, Si+, K+ elements cannot reaction with it, the mass shift caused by reaction with H2 was selected to eliminate mass spectrum interference. Sc was selected as internal standard element to correct the matrix effects. The flow rates in the CRC of different reaction gas were optimized by considering the background equivalent concentration (BEC) of analytes, and the best gas flow rate for O2 and H2 were 0.45 mL·min-1, and 7.5 mL·min-1, respectively. The DL for Na, Si, P, S, Cl, K, Ti, V, and As were 6.41, 37.3, 24.6, 118, 530, 7.96, 7.61, 0.34, and 3.20 ng·L-1, respectively, under the optimized conditions. The linear correlation coefficient (R2) of analytes were ≥0.999 8 in the range 0～50 μg·L-1. The recovery of all elements ranged from 91.2% to 108%, and the relative standard deviation (RSD) was ranged from 1.9% to 4.6%. These results showed that the proposed method was accuracy and precise. Analytical results obtained from different original Jatropha curcas L. oil showed that the contents of element P, S, and (Na+K) were ≤164, 2 310, and 1 690 ng·g-1, respectively. These indexes were much lower than those of the contents in the conventional fossil energy resource, and reached the standards of Chinese national standard of biodiesel, European IV biodiesel standard, German biodiesel standard, and American biodiesel standard. This study proposed a new approach for the determination of multi-element in Jatropha curcas L. oil with convenience and feasibility, and provided a scientific basis for the quality control and safety application of Jatropha curcas L. oil.
Key words：Jatropha curcas L. oil；Inductively coupled plasma tandem mass spectrometry；Multi-element；Collision reaction cell；Reaction gas
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