Seung-Hyun Yang, Yongho Shin, Hoon Choi
Abstract
A method for the simultaneous analysis of pesticide multiresidues in three root/rhizome-based herbal medicines (Cnidium officinale, Rehmannia glutinosa, and Paeonia lactiflora) was developed with GC-MS/MS. To determine the concentrations of pesticide residues, 5 g of dried samples were saturated with distilled water, extracted with 10 mL of 0.1% formic acid in acetonitrile/ethyl acetate (7:3, v/v), and then partitioned using magnesium sulfate and sodium chloride. The organic layer was purified with Oasis PRiME HLB plus light, followed by a cleanup with dispersive solid-phase extraction containing alumina. The sample was then injected into GC-MS/MS (2 μL) using a pulsed injection mode at 15 psi and analyzed using multiple reaction monitoring (MRM) modes. The limit of quantitation for the 296 target pesticides was within 0.002–0.05 mg/kg. Among them, 77.7–88.5% showed recoveries between 70% and 120% with relative standard deviations (RSDs) ≤20% at fortified levels of 0.01, and 0.05 mg/kg. The analytical method was successfully applied to real herbal samples obtained from commercial markets, and 10 pesticides were quantitatively determined from these samples.
Introduction
Herbal medicines are generally defined as the parts of plants or their complex mixtures having biologically active ingredients [1]. For over 3,000 years, they have been used to treat a wide range of symptoms and ailments, including colds, headaches, menstrual problems, asthma, and other immune problems, liver disease, and various cancers [2]. Originating in Asia, herbal medicines are also called Chinese herbal medicine (CHM) in China, Kampo-yaku in Japan, and Hanyak in Korea, and have become a popular alternative to synthetic pharmaceutical drugs in Western countries [3].
Materials and method
Stock solutions of the target pesticides (analytical grade) were purchased from Kemidas Standard (Gunpo, Republic of Korea). Acetonitrile (ACN; HPLC grade) was obtained from J. T. Baker (Centre Valley, PA, USA). HPLC grade ethyl acetate (EA) and magnesium sulfate (MgSO4; ≥99%) were purchased from Daejung Chemicals & Metals (Siheung, Republic of Korea). Formic acid (≥99%), acetic acid (≥99%), and sodium chloride (NaCl; ≥97%) were obtained from Junsei Chemicals (Tokyo, Japan). Ceramic homogenizers for 50-mL tubes and various dispersive-solid phase extraction (d-SPE) tubes, including Part No. 5982–4921 (25 mg C18 and 150 mg MgSO4), 5982–5021 (25 mg primary secondary amine; PSA and 150 mg MgSO4), 5982–5121 (25 mg PSA, 25 mg C18, and 150 mg MgSO4), 5982–5122 (50 mg PSA, 50 mg C18, and 150 mg MgSO4), 5982–5221 (25 mg PSA, 2.5 mg graphitized carbon black; GCB, and 150 mg MgSO4), and 5982–5321 (25 mg PSA, 7.5 mg GCB, and 150 mg MgSO4), were purchased from Agilent technology (Santa Clara, CA, USA). Alumina (≥99%) was purchased from Sigma-Aldrich (St. Louis, MO, USA). The Oasis PRiME HLB cartridge plus light (100 mg) was obtained from Waters Corporation (Milford, MA, USA). Deionized water (18.2 MΩ/cm) was prepared in-house using a Direct-Q3 UV (Darmstadt, Germany).
Results
Pulsed-splitless injection of GC can improve the shape and sensitivity of the target peaks by establishing the optimal inlet pressure during sample injection. In many studies analyzing pesticides using GC systems, the pulsed injection mode was used [26–28]. Ling et al. reported that the peak heights of methamidophos, acephate, and omethoate improved using pulsed splitless injection at 30 psi [27]. Godula et al. (1999) recommended not using a pulsed pressure exceeding 60 psi to obtain good responses for all analytes, including early eluting pesticides [28].
Discussion
A comparison of the peak areas of the 296 target analytes at 5, 15, 25, 35, and 45 psi in the unpulsed mode revealed a characteristic intensity pattern for four retention time (tR) segments (8–14, 14–16.2, 16.2–18, and 18–25 min), as shown in S1 Fig. At the 5 psi pressure pulse, the average relative intensities were less than 74% of those observed in the unpulsed injection (100%). At 25, 35, and 45 psi pressure pulses, the average relative intensities were inferior (58–96%) to those at the unpulsed injection in the tR range of 8–16.2 min, but the magnitude of the relative intensities improved at longer retention times, showing more than 109% at 16.2–25 min. Furthermore, the differences in the average relative intensities for each tR increased as the pulse pressure increased. Therefore, the tested pulsed pressures are not suitable as multiresidue instrument conditions since they do not improve the intensities of the analytes in the overall tR. However, when the pulse pressure was set to 15 psi, the average relative intensities (102–112%) increased compared to those in the unpulsed condition in the overall tR ranges. Therefore, a pulse pressure of 15 psi was applied in the established analytical method
Conclusions
A simultaneous analysis of 296 pesticides in three herbal medicines (C. officinale, R. glutinosa, and P. lactiflora) was developed with GC-MS/MS and modified QuEChERS method. Under the MRM detection mode and 15 psi pulsed-splitless injection of GC-MS/MS, extraction with acidified ACN/EA (7:3, v/v) and combination of Oasis PRiME HLB plus light and alumina d-SPE cleanup were found to be the optimal procedures for the multiresidue analysis in these herbal medicines. Using the established analytical method, we acquired reasonable validation data, including the LOQ (0.002–0.05 mg/kg), linearity of calibration, and recovery for most pesticides. The established method improved the extraction efficiency and reduced interferences, resulting in a reduction of the matrix effect for the target analytes. It was successfully applied to monitor multiresidues in samples obtained from commercial markets. The residue results can be used as reference data for the pesticide risk assessment in herbal medicines.
Citation: Yang S-H, Shin Y, Choi H (2023) Simultaneous analytical method for 296 pesticide multiresidues in root and rhizome based herbal medicines with GC-MS/MS. PLoS ONE 18(7): e0288198. https://doi.org/10.1371/journal.pone.0288198
Editor: Totan Adak, ICAR-National Rice Research Institute, INDIA
Received: December 6, 2022; Accepted: June 21, 2023; Published: July 6, 2023
Copyright: © 2023 Yang et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: All relevant data are within the manuscript and its Supporting Information files.
Funding: This study was supported by a grant (21172MFDS149) from the Ministry of Food and Drug Safety for the draft submission, and there was no additional external funding received for this study during revision period. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
Source: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0288198#sec016
