White-wine method screens 107 pesticides in a 36-minute cycle

Faster screening with chiral separation

LCGC International discussed the study on Monday, November 9, and the work was published in Analytica Chimica Acta. The researchers used low-pressure gas chromatography coupled with tandem mass spectrometry, or LPGC-MS/MS, to screen white wine for 107 pesticides in a 36-minute cycle. Data acquisition took 27 minutes, and the method provided acceptable separation of 7 chiral pesticide pairs.¹

Chiral pesticides occur as 2 mirror-image forms called enantiomers. These forms can behave differently in organisms and the environment: 1 may account for most of the desired pest-control effect, while the other may be less useful or present different toxicological risks. Residue rules nevertheless tend to regulate the pesticide’s total concentration rather than each enantiomer separately.¹

That distinction is difficult in wine because residues may occur at very low concentrations within a matrix containing alcohol, sugars, pigments and numerous natural compounds. Previous pesticide methods for wine did not separate enantiomers even when the compounds under examination were chiral.¹

Column design and operating conditions

The method was intended to balance speed, resolution and sample capacity, factors that commonly compete in chiral gas chromatography. Instead of the long, narrow columns often used to obtain strong resolution at the cost of longer runs and limited loading, the team paired a short, wide-bore chiral column with low-pressure outlet conditions. Corresponding author Mariosimone Zoccali said this configuration enabled higher gas velocities and quicker separation while retaining sufficient resolution for the targeted pesticides.¹

The selected setup used a 5 m wide-bore γ-cyclodextrin column and raised the temperature from 50 °C to 180 °C at 5 °C per minute. Zoccali identified temperature control as the largest influence on enantiomeric resolution because the weak interactions responsible for separation are heat-sensitive. Faster ramps impaired separation; slowing the ramp to 2 °C per minute improved it but extended the run to about 75 minutes. The final conditions balanced speed, separation and signal quality.¹

The wide-bore column also supported greater sample loading and operational durability. Researchers injected 5 μL of concentrated extract in splitless mode, increasing trace-residue detectability without overloading the column. The system remained usable for about 450 injections.¹

Extraction and detection

Sample preparation followed a modified QuEChERS procedure based on ethyl acetate. The team extracted 10 g of wine with 10 mL of ethyl acetate in the presence of magnesium sulfate, sodium chloride and citrate salts, then concentrated the extract by about 100 times under a gentle nitrogen stream. A dispersive solid-phase extraction clean-up step was tested but excluded because it did not improve performance and could add interfering compounds.¹

Detection employed triple-quadrupole mass spectrometry in multiple reaction monitoring mode, tracking 2 transitions for every pesticide. Because low-pressure chromatography produces faster elution and narrower peaks, the researchers scheduled compound-specific acquisition at 14 Hz to obtain sufficient measurements across each peak without sacrificing sensitivity.¹

Analytical performance

The method generally met performance expectations applied to routine European pesticide monitoring. Quantification limits ranged from 2.1 to 74.4 μg kg⁻¹ and were at or below the relevant maximum residue limits. Intra-day precision was below 15% for the tested compounds, and the mean coefficient of variation was about 6%.¹

Accuracy was 73–125% at 0.01 mg kg⁻¹, 85–118% at 0.05 mg kg⁻¹ and 89–107% at 0.1 mg kg⁻¹. Recoveries were lower and more variable, averaging about 56% at 0.01 mg kg⁻¹ and 42% at 0.1 mg kg⁻¹, although their precision remained within commonly used criteria.¹

Why individual enantiomers matter

Zoccali cited a commercial wine sample in which 1 fipronil enantiomer exceeded the applicable maximum residue limit while the other stayed below it. He said a total-residue measurement alone could therefore provide a less detailed account of contamination and exposure.¹

The researchers did not propose immediately replacing existing residue rules. They presented the method as a way to generate occurrence data and support future assessments of individual-enantiomer risks, potentially contributing evidence for a more detailed regulatory framework.¹

Potential use and remaining work

If confirmed beyond the initial study, the approach could allow testing laboratories to process more wine samples in less time and give wineries and food-safety authorities a more precise view of contamination profiles than conventional multiresidue analysis. This could be useful in routine surveillance, where obtaining chiral information has traditionally required substantially more time.¹

The authors considered the method better suited to high-throughput monitoring than traditional chiral gas-chromatography workflows, but said broader interlaboratory validation is necessary before full routine regulatory use. They also called for further testing in other wine types and food matrices.¹

The paper’s authors were Giorgia Rinaldi, Mariosimone Zoccali, Peter Q. Tranchida and Luigi Mondello. Zoccali said their aim extended beyond reducing run times: the team sought to make enantioselective pesticide analysis practical for monitoring laboratories that require both speed and selectivity.¹