Application of Isotope Dilution Gas Chromatography−Mass Spectrometry in Analysis of Organochlorine Pesticide Residues in Ginseng Root

Abstract

A highly accurate and precise method based on isotope dilution gas chromatography-mass spectrometry was developed for the determination of five matrix-bound organochlorine pesticides, namely, hexachlorobenzene and hexachlorocyclohexanes (alpha-, beta-, delta-, and gamma- isomers), in a reference sample of Panax gingseng. Identification of the analytes was confirmed under selective ion monitoring mode by the presence of two dominant ion fragments within the specific time windows (+/-1% of the relative retention time with respect to the calibration standards) and matching of relative ion intensities of the concerned ions in samples and calibration standards (within +/-5%). Quantification was based on the measurement of concentration ratios of the natural and isotopic analogues in the sample and calibration blends. To circumvent the tedious iterative process of exact isotope matching that is often used in isotope dilution mass spectrometry analysis, a single-point calibration procedure was adopted with the isotopic amount ratios in the sample and calibration blends close to unity (0.9-1.1). Under the described approach, intraday and interday repeatability of replicate analyses of organochlorine pesticides in the ginseng root sample were below 1.4%. The expanded relative uncertainty ranging from 4.0 to 6.5% at a coverage factor of 2 was significantly lower than those of conventional gas chromatographic methods using other calibration techniques (internal or external standards). A deviation of less than 2.0% from the certified values was achieved when applying the developed method to determine hexachlorobenzene, alpha-, and beta-hexachlorocyclohexane in a certified reference material (CRM), BCR-CRM 115. Because of the unavailability of relevant CRMs of herbal origins, the concerned ginseng root sample, after verification of the "true values" of the concerned organochlorine pesticides by the valid primary method, is suitable for serving as an in-house reference material for quality assurance and method validation purposes.

Pesticide Residues in Natural Products with Pharmaceutical Use: Occurrence, Analytical Advances and Perspectives

“…Recent literature still uses these procedures because of the offered versatility derived from independence from expensive analytical instrumentation which are limiting requirements for laboratories. Acidic digestion procedures of the obtained organic extracts employing H 2 SO 4 were reported for the analysis of OCs pesticides in Ginseng root (Chan et al, 2007, Quan et al, 2004. Similarly, a selected group of OCs and OPs were determined in herbal essential oils by using this technique (Yoon et al, 1999).…”

“…However this strategy is limited for www.intechopen.com the analysis of a reduced group of non-hydrolysable compounds. Moreover, Soxhlet extraction was reported as enhanced extraction methodology for OCs determination in Ginseng root using EtAc (ethyl acetate):petroleum ether (7:3) (Chan et al, 2007) and acetone:petroleum ether (3:1) solvent mixtures (Quan et al, 2008). A selected group of carbamates (metalocarb, isoprocarb, fenobucarb, carbofuran, pirimicarb and carbaryl were extracted with Soxhlet based extraction in CH 2 Cl 2 from three different Chinese herbal medicines (Wu et al, 2005).…”

“…Chan and co-workers introduced the use of isotope dilution (ID) for the determination of HCB and HCH isomers by GC-MS in Ginseng root. ID-GC-MS showed to be a good quality assurance approach since inaccuracy and uncertainty were significantly reduced in a difficult matrix (Chan et al, 2007). However, this strategy is generally expensive, time consuming for routine analysis and is intended for MS only.…”

Use of assigned reference values: revisiting a small-scale inter-laboratory comparison for residual pesticides in tea

“…Apart from soaking tea powder with deionized water overnight (24 h), sample extraction and clean-up procedures in the GC-IDMS were similar to those of the above-described GC-lECD. The quantification relied on the exact matching approach that was reported in details by this laboratory [7].…”

Determination of sulfonamides in milk by ID-LC-MS/MS

“…It eliminates all errors at all stages of the method. IDMS technique traceable to International System of Units is a primary method and it is an acceptable alternative to estimate "true value" in the absence of a certified reference material (CRM) [23,24]. IDMS provides high accuracy and precision compared with internal standard addition or external calibration techniques [24].…”