Determination and Dietary Risk Assessment of 8 Pesticide Residues in Ginger Oleoresin and Ginger Essential Oil by QuEChERS-LC-MS/MS

Ginger (Zingiber officinale Rosc.) is the first batch of medicinal and edible plants announced by the Ministry of Health in China. Ginger oleoresin and ginger essential oil are the products extracted from ginger, widely used as flavours and fragrances, of which the quality has a direct influence on food safety. Due to the complex composition of ginger oleoresin and ginger essential oil, the qualitative and quantitative detection of pesticide residues is challenging. In this study, a liquid-liquid extraction and QuEChERS pretreatment method of 8 pesticide residues in ginger and subsequently analysis of the extracts by liquid chromatography-tandem mass spectrometry (LC-MS/MS) were developed and validated. The sample was extracted by 1% acidic acetonitrile solution, followed by addition of an equal volume of water and a small amount of hexane to the sample. After vortexing and centrifugation, the sample underwent purification via an optimized QuEChERS technique. The purified sample was analyzed by electrospray ionization MS under positive ion mode with multiple reaction monitoring (MRM). Under optimized conditions, the results showed that the calibration curves of the 8 pesticides have good linearity within the range of 1-32 μg/L, with correlation coefficients(R²) higher than 0.99. The limits of detection (LODs) are 0.03-0.16 mg/kg, and the limits of quantification (LOQs) are 0.10-0.53 mg/kg. The recoveries are 70%-119%, and the relative standard deviations (RSDs) are lower than 20% (n=6) at high, medium and low of spiking levels. The method was successfully applied to 20 ginger, 15 oleoresin, and 15 essential oil samples. The results showed that the positive detection rates of thiamethoxam, imidacloprid, and clothianidin are 56%, 58%, 52%, respectively. The detection rates of other five pesticides are lower than 20%. The proportion of residual levels greater than 1 mg/kg were found to be at a rate of 12%, 16% and 10% for thiamethoxam, imidacloprid and clothianidin with maximum levels recorded as 2.16, 1.92 and 2.01 mg/kg, respectively. Dietary exposure risk of the 3 pesticides in ginger, ginger essential oil and ginger oleoresin was evaluated based on the median value of pesticide residues. The evaluation result was far less than 100%, indicating that dietary exposure risk of pesticide residues in ginger oleoresin and ginger essential oil should be acceptable. This study provides not only an efficient and reliable quantitative method for the detection of various pesticide residues in ginger oleoresin and ginger essential oil, but also a practical technical reference for the internal quality control of plant extract enterprises and market supervision of government departments. Moreover, in view of the fact that pesticide residues have been detected in plant extract products, such as ginger oleoresin and ginger essential oil, it is recommended to formulate the maximum residue limit (MRL) standards of various plant extracts according to the acceptable daily intake (ADI) values of pesticides, MRL standards of plant extracts raw materials and extraction concentration factors to regulate the market.