Simultaneous Determination of 21 Plant Growth Regulators in Various Fruits Using QuEChERS Coupled with an HPLC-MS/MS Technique

Importance of the topic

Monitoring plant growth regulators (PGRs) in fruits is critical to ensure food safety and regulatory compliance. PGRs, synthetic analogues of natural hormones, can enhance crop yield and quality but pose health risks when residues exceed permissible limits. Authorities worldwide have established maximum residue levels (MRLs) for various PGRs in fruits. A rapid, sensitive, and reliable multi-residue method addresses the need for routine surveillance and supports consumer protection.

Study objectives and overview

This work aimed to develop and validate a streamlined approach for the simultaneous determination of 21 diverse PGRs in fruits. Leveraging a modified QuEChERS extraction coupled with high-performance liquid chromatography–tandem mass spectrometry (HPLC-MS/MS), the study targeted apple, pear, strawberry, grape, and orange matrices. Performance parameters including linearity, sensitivity, recovery, precision, and matrix effects were systematically evaluated to demonstrate method robustness and suitability for routine analysis.

Methodology and Instrumentation

Sample Preparation and Cleanup:

• Homogenize 10 g fruit sample with 10 mL acetonitrile containing 1 % acetic acid.
• Salt-out with 4 g MgSO₄ and 1.5 g sodium acetate; centrifuge.
• Dispersive SPE cleanup using 25 mg C18 and 150 mg MgSO₄; vortex and centrifuge.
• Filter supernatant through 0.22 µm membrane before analysis.

HPLC-MS/MS Conditions:

• Agilent Infinity UHPLC 1290 System with XDB-C18 column (4.6 × 150 mm, 5 µm) at 35 °C.
• Gradient elution: 5 mM ammonium acetate with 0.05 % formic acid in water (A) and acetonitrile (B); flow rate 0.5 mL/min.
• Injection volume 5 µL; needle wash 100 % methanol.
• Agilent 6460 Triple Quadrupole MS with ESI source in MRM mode; positive and negative ionization segments optimized per analyte.

Main results and discussion

Calibration and Sensitivity:

• Matrix-matched external calibration showed linear dynamic ranges over 2–3 orders of magnitude (0.10–1,000 µg/L) with R² > 0.99.
• Limits of detection (LOD) ranged from 0.020 to 6.0 µg/kg; limits of quantification (LOQ) from 0.10 to 15.0 µg/kg, well below typical MRLs.

Recovery and Precision:

• Spiking experiments at three levels in five fruit matrices yielded average recoveries of 73.0–111.0 %.
• Relative standard deviations (n = 6) ranged from 3.0 to 17.2 %, meeting acceptance criteria for residue analysis.

Matrix Effects:

• Evaluation of signal suppression/enhancement revealed significant matrix effects for 48 % of analytes in certain fruits.
• Adoption of matrix-matched calibration effectively compensated for these interferences, ensuring accurate quantification.

Practical benefits and applications

The proposed method is rapid (total run time < 25 min), easy to perform, and compatible with high-throughput laboratories. Its broad analyte scope and sensitivity enable compliance monitoring of regulated PGRs in diverse fruit commodities. The streamlined workflow reduces solvent consumption and minimizes sample handling, supporting efficiency in quality control and regulatory laboratories.

Future Trends and Applications

Continued advances may include:

• Extension to other food matrices (vegetables, cereals) and additional PGR classes.
• Integration of high-resolution MS for non-target screening and confirmatory analysis.
• Automation of QuEChERS cleanup and online SPE coupling to reduce manual steps.
• Green chemistry optimization, such as miniaturized extraction and reduced solvent volumes.

Conclusion

This study presents a validated QuEChERS-HPLC-MS/MS method for simultaneous quantification of 21 PGRs in fruits. It delivers high sensitivity, accuracy, and reproducibility across multiple matrices, meeting stringent regulatory requirements. The approach is well suited for routine monitoring, reinforcing food safety and consumer confidence.

Reference

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