Determination of four quaternary ammonium polar pesticides in food and beverage samples by tandem IC-MS/MS

Význam tématu

Quaternary ammonium polar pesticides are among the most widely used agrochemicals globally. Their high polarity and cationic nature pose significant analytical challenges in complex food and beverage matrices, leading to potential co-extractive interference and ion suppression in mass spectrometry. Reliable, sensitive and cost-effective methods are essential to ensure consumer safety, comply with evolving regulatory limits, and support routine QA/QC in food testing laboratories.

Cíle a přehled studie / článku

This study aimed to develop and validate a rapid, robust ion chromatography–tandem mass spectrometry (IC-MS/MS) method for simultaneous baseline separation, identification and quantitation of four quaternary ammonium pesticides (chlormequat, mepiquat, paraquat, diquat) in a variety of simulated and real food/beverage samples. The performance of Thermo Scientific™ Dionex™ IonPac™ CS21-Fast-4 µm column coupled to a TSQ Altis™ triple quadrupole MS was assessed under routine conditions.

Použitá metodika a instrumentace

Chromatographic separation was achieved on a 2 × 150 mm IonPac CS21-Fast-4 µm column with a guard, using an electrolytically generated methanesulfonic acid gradient (3–25 mM) at 0.3 mL/min and 40 °C in 15 min. Post-column suppression was performed with a Dionex CDRS 600 suppressor. Detection was carried out in positive heated-ESI SRM mode on a Thermo Scientific TSQ Altis triple quadrupole mass spectrometer. Divert valve switching protected the MS source from high-conductivity eluent and matrix ions. Sample preparation for foods and beverages followed a simplified QuPPe methanol/water extraction, filtered and diluted where necessary.

Hlavní výsledky a diskuse

• Chromatographic resolution: Complete baseline separation of the four analytes and major matrix cations (Li⁺, Na⁺, NH₄⁺, K⁺, Mg²⁺, Ca²⁺) was achieved on the CS21-Fast column, eliminating co-elution issues of paraquat/diquat observed on earlier CS17 phases.
• Linearity and sensitivity: Normalized calibration (1–100 µg/L) exhibited r² ≥ 0.999 across all analytes and matrices. Limits of quantitation (LOQ) by t-test were below 0.2 µg/L for all compounds in DI water; 0.04–0.31 µg/L in high ionic strength matrix.
• Matrix effects: Monovalent analytes (chlormequat, mepiquat) showed negligible suppression; divalent paraquat and diquat experienced up to 40% signal suppression in simulated high-ionic matrices. Isotopically labeled internal standards fully corrected these effects, yielding ≤3% RSD.
• Precision and accuracy: Instrument precision (n=7) was <1.7% RSD at 1 µg/L and <0.4% at higher levels. Corrected recoveries in water, simulated matrices, tea infusions and QuPPe-extracted food samples (carrot baby food, wheat flour) ranged 92–113% across spike levels.

Přínosy a praktické využití metody

This IC-MS/MS workflow provides a streamlined, single-extract approach for both anionic and cationic polar pesticide screening using a unified QuPPe preparation. It offers high throughput (15 min run time), low detection limits, and robust quantitation in diverse matrices without costly HRAM instrumentation. The method is suitable for routine regulatory compliance, environmental monitoring and research applications in food safety labs.

Budoucí trendy a možnosti využití

• Extension to broader suites of polar pesticides including novel cationic or zwitterionic compounds.
• Integration with automated sample preparation and online dilution for ultra-high throughput screening.
• Combination with high-resolution MS for non-targeted screening of emerging contaminants.
• Further reduction of analysis time via ultra-high-pressure IC or monolithic columns.

Závěr

The developed Dionex IonPac CS21-Fast-4 µm IC-MS/MS method achieves reliable baseline separation and low-level quantitation of four quaternary ammonium pesticides in complex food and beverage samples. Isotopically labeled internal standard correction ensures accuracy and precision across varied matrices. This cost-effective, robust protocol supports routine monitoring and regulatory compliance, addressing a critical gap in cationic polar pesticide analysis.

Reference

1. Adams, S.; Guest, J.; Dickinson, M.; et al. J. Agric. Food Chem. 2017, 65, 7294–7304.
2. Thermo Scientific TN 73204 (2019) Multi-residue analysis of polar anionic pesticides in food via IC-MS/MS.
3. Thermo Scientific Poster 72781 (2018) Direct determination of cationic polar pesticides in produce by IC-MS/HRAM.
4. Thermo Scientific AN 72908 (2018) Determination of cationic polar pesticides in fruit/vegetable homogenates with IC-HRAM MS.
5. Anastassiades, M.; Kolberg, D. I.; et al. QuPPe method v9.3, EU Reference Laboratory SRM.
6. Thermo Scientific AN 661 (2016) Fast routine analysis of polar pesticides in foods by suppressed IC-MS.
7. EU QuPPe-PO v.11 Method (2020) http://quppe.eu/.
8. Thermo Scientific AN 73339 (2020) Anionic polar pesticides by IC with conductivity and MS detection.