Determination of Trace Heavy Metal Elements in Plant Essential Oils by Inductively Coupled Plasma Optical Emission Spectrometry
LI Ai-yang1, FU Liang2*, CHEN Lin3
1. College of Material and Chemical 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 Medica, Hunan Academy of Traditional Chinese Medicine，Changsha 410013, China
Abstract：Plant essential oils are naturally complex compounds extracted from aromatic plants with volatile and tangy aromas as secondary metabolites of aromatic plants, and their diverse biological activities are widely used in the pharmaceutical and cosmetic industries. Plant essential oils are highly permeable and can penetrate skin tissue in an active molecular state and enter the bloodstream after absorption via the lymph glands. The heavy metal elements they contain are also highly susceptible to the entry of plant essential oils into the human body, posing a potential threat to health. This paper used nitric acid and hydrogen peroxide for microwave digestion of plant essential oils. In the dual-mode of multimode sample introduction system (MSIS), the contents of vapor forming heavy metal elements As, Sn, Sb, and Hg and non-vapor forming heavy metal elements Cr, Ni, Cd, and Pb were determined by inductively coupled plasma optical emission spectrometry (ICP-OES). Hydrochloric acid was selected to acidify the sample and reduce the oxidized analytes in the sample. L-cysteine/tartaric acid was added online to improve the vapor generation efficiency. Sodium borohydride/sodium hydroxide was selected to transform As, Sn, Sb, and Hg into the vapor state in MSIS. Because of the multiple or single spectral overlap and background interference in the analysis process, the pure solutions for the blank, analyte and the expected interferences are measured in the sample, and the fast automatic curve fitting technology (FACT) was constructed according to the obtained spectral response data by deconvolution. Analytical spectral lines were separated from interference spectral lines to realize real-time correction of spectral overlap interference and background interference. The method’s accuracy was evaluated by the spike recovery experiments and comparison with inductively coupled plasma mass spectrometry (ICP-MS). The method detection limit (MDL) of analyte was between 0.38～11.2 μg·kg-1, the spiked recovery was 95.4%～104%, the relative standard deviation (RSD) was 1.9%～4.9%, and the relative error (RE) of the comparative analysis ranged from -2.1% to 2.7%, indicating that the method was accurate and reliable with high precision. The heavy metal elements in eight plant essential oils were analyzed, and the levels of As, Hg, and Pb in all plant essential oil samples were well below the maximum limit standards established by GB/T 26516—2011, while the levels of Cr, Ni, Sn, Cd, and Sb, the heavy metal elements in plant essential oils, although no limit standards were established, were at extremely low levels. MSIS has the dual functions of traditional atomization and vapor generation. It does not need to switch different sampling systems when analyzing vapor forming elements and non-vapor forming elements. It can meet the needs of high-throughput analysis of trace heavy metal elements in large quantities of plant essential oils.
李爱阳，符 靓，陈 林. 电感耦合等离子体发射光谱测定植物精油中的重金属元素[J]. 光谱学与光谱分析, 2022, 42(04): 1162-1167.
LI Ai-yang, FU Liang, CHEN Lin. Determination of Trace Heavy Metal Elements in Plant Essential Oils by Inductively Coupled Plasma Optical Emission Spectrometry. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2022, 42(04): 1162-1167.
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