Analysis of Heavy Metal Elements in Palm Oil Using MP-AES Based on Extraction Induced by Emulsion Breaking
LIU Hong-wei1, FU Liang2*, CHEN Lin3
1. College of Materials Science and Engineering, Hunan Institute of Technology, Hengyang 421002, China
2. College of Materials Science and Engineering, Chongqing University, Chongqing 400045, China
3. Institute of Chinese Materia, Hunan Academy of Traditional Chinese Medicine, Changsha 410013, China
Abstract：As one of the vegetable oil species with the largest production, consumption and trade in the world, palm oil is not only rich in carotenoids, vitamin E, coenzymes and sterols but also has the characteristics of good plasticity at room temperature, easy fractionation and low price, and is one of the major fat sources of the human body. However, due to the influence of natural factors and human activities, the heavy metals released into the environment are accumulated in palm tree fruits and are polluted by heavy metals in palm oil pressing and refining, resulting in the potential harm to human health once the contents of heavy metal elements exceed the standards. In order to fully clarify the content of various heavy metal elements in palm oil, and ensure the quality and safety control of palm oil, a new strategy for determination of heavy metals elements in palm oil using microwave plasma atomic emission spectroscopy (MP-AES) based on extraction induced by emulsion breaking (EIEB) was proposed. A surface-active acidic solution composed of 5% (W/V) Triton X-114 and 50% (V/V) hydrochloric acid was thoroughly mixed with the palm oil sample, and the formed water-in-oil emulsion was subjected to ultrasonic bath at 90 ℃ for 40 min, the formed aqueous phase was collected. The heavy metal elements As, Hg, Cd, Pb, Ni, and Cr were determined by MP-AES in the dual mode of the multimode sample introduction system (MSIS). The effects of EIEB parameters such as emulsifier, extraction agent, extraction temperature and extraction time on the extraction efficiency of analytes were evaluated in detail, and the spectral wavelengths of analytes were optimized. The accuracy and precision of the method were verified by spiked recovery of palm oil samples with oil standards. The palm oil samples were processed by microwave digestion technology and compared with inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) to verify the method's reliability. The results showed that the analytes showed a good linear relationship (linear correlation coefficient was greater than or equal to 0.999 8), the limit of detection (LOD) was between 0.025 and 0.29 μg·L-1, and the spiked recovery was between 96.5% and 105%, the relative standard deviation (RSD) was less than or equal to 4.1%. At the 95% confidence level, there is no significant difference between the analytical results of the method and those of ICP-MS/MS. EIEB separates and enriches the analytes from the oil phase to thewater phase, avoiding the interference of many matrices. Running MSIS in dual mode enables simultaneous determination of hydride and non-hydride elements. MP-AES extracts nitrogen from the air as the gas source without using expensive argon or flammable gas, which reduces the cost of analysis and operation. Furthermore, it is safe and environmentally friendly. The developed method has the advantages of simple and rapid operation, good analytical stability, accurate and reliable results, and can meet the high throughput detection requirements of multiple heavy metal elements in large batches of palm oil samples, and has been applied to the quality control and safety evaluation of palm oil samples.
Key words：Extraction induced by emulsion breaking; Microwave plasma atomic emission spectroscopy; Multimode sample introduction system; Palm oil; Heavy metal
刘宏伟，符 靓，陈 林. 基于破乳诱导萃取棕榈油中重金属元素的MP-AES分析[J]. 光谱学与光谱分析, 2023, 43(10): 3111-3116.
LIU Hong-wei, FU Liang, CHEN Lin. Analysis of Heavy Metal Elements in Palm Oil Using MP-AES Based on Extraction Induced by Emulsion Breaking. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2023, 43(10): 3111-3116.
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