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

植物精油是从芳香植物提取的天然复杂化合物，作为芳香植物的次生代谢产物具有挥发性和浓郁香味，其特有的多样化生物活性广泛应用于医药和化妆品行业。植物精油具有高渗透性，能以活跃的分子态渗透皮肤组织，经淋巴腺吸收后进入血液，其所含的重金属元素也极易随植物精油进入人体对健康构成潜在威胁。采用硝酸-双氧水对植物精油进行微波消解，在多模式样品导入系统（MSIS）的双重模式下，采用电感耦合等离子体发射光谱（ICP-OES）测定其中可形成蒸气重金属元素As，Sn，Sb，Hg和不可形成蒸气重金属元素Cr，Ni，Cd和Pb的含量。选择盐酸对样品进行酸化并预还原氧化态元素，通过在线加入L-半胱氨酸/酒石酸提高可形成蒸气元素的蒸气发生效率，利用硼氢化钠/氢氧化钠在MSIS中将As，Sn，Sb和Hg转变为蒸气状态；针对分析过程中存在的多个或单个光谱重叠和背景干扰，分别对空白溶液、分析元素和预期干扰元素的纯溶液进行测定，根据获得的光谱响应数据解卷积构建快速自动曲线拟合技术（FACT）模型，将分析谱线从干扰谱线中分离出来，从而实现光谱重叠干扰和背景干扰的实时校正；采用加标回收并与电感耦合等离子体质谱（ICP-MS）进行对比分析评价方法的准确性。各元素方法的检出限（MDL）为0.38~11.2 μg·kg-1，加标回收率为95.4%~104%，相对标准偏差（RSD）为1.9%~4.9%，对比分析的相对误差（RE）在-2.1%~2.7%之间，表明方法准确可靠，精密度高。对8种植物精油中的重金属元素进行了分析，所有植物精油样品中重金属元素As，Hg和Pb的含量远低于GB/T 26516—2011制定的限量标准，植物精油中重金属元素Cr，Ni，Sn，Cd和Sb的含量虽然没有制定限量标准，但均处于极低水平。MSIS兼具传统雾化和蒸气发生双重功能，在分析可形成蒸气元素和不可形成蒸气元素时无需切换不同进样系统，能满足大批量植物精油中微量重金属元素的高通量分析需要。

Determination of Trace Heavy Metal Elements in Plant Essential Oils by Inductively Coupled Plasma Optical Emission Spectrometry

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.