How to find out Multi- Pesticides Residue on Lettuce

On one hand the green leafy lettuce is having multi health benefits but on the other hand the pesticides residue on the same also creates many health problems. The producer  farmer has to use these pesticides, fungicides and herbicides for the benefit of the growth of the green leafy substance. But the judicious use of these and the multi residue analysis of lettuce is also necessary.

Campinas State University, Brazil has come out with the new analytical method to determine the multi-residue level of 16 multi-class pesticides used on lettuces. They used ultra-high performance liquid chromatography and tandem mass spectrometry with a triple quadrupole mass analyser and positive-mode electro-spray ionisation. It's a quick, safe and inexpensive way to prepare samples.

Lettuce health benefits includes inducing sleep, fighting inflammation, fighting bacterias and fungal, keeping you hydrated, helps improve memory retention, preserve cognitive function, helps control anxiety, a rich source of omega 3 fatty acids, promotes muscle development, support weight loss, offers skin care benefits and support pregnancy development.

The word Lettuce is derived from the Roman ‘lactuca sativa’; however, it did not originate in Rome, but rather in Egypt. Ancient Egyptians were the first to cultivate lettuce for its oil-rich seeds. The vegetable was revered by Egyptians, Greeks, and Romans for its religious and medicinal significance.

Today, lettuce is cultivated as a leaf vegetable in nearly all parts of the world. It is an annual plant, which can only be harvested 65 to 130 days after sowing. Lettuce belongs to the daisy family, Asteraceae. The leafy vegetable is often eaten raw as a salad, or used as a food wrap.

The processing factors of six pesticides during the preparation of fresh-cut lettuce was done to assess the risk of ingestion of pesticide residues associated with the consumption of the same. A field study was carried out on the dissipation of three insecticides (imidacloprid, tebufenozide, cypermethrin) and three fungicides (metalaxyl, tebuconazole, azoxystrobin) during treatment conditions simulating those used for commercial fresh-cut lettuce.

A simultaneous residue analysis method is validated using QuEChERS extraction with acetonitrile and CG-MS and LC-MS/MS analysis. The residues detected after field application never exceed the established Maximum Residue Limits. The processing factors were generally less than 1 (between 0.34 for tebufenozide and 0.53 for imidacloprid), indicating that the process, as a whole, considerably reduces residue levels in processed lettuce compared to fresh lettuce. It is confirmed that cutting, followed by washing and drying, considerably reduces the residues.

The study, which followed SANTE/11945/2015 guidelines, showed that the method is selective, accurate and precise providing recoveries between 70 and 120 percent  with standard deviations ≤ 20 percent  and quantification limits from 3 μg/kg. The method was compared with one based on high-performance liquid chromatography with tandem mass spectrometry in terms of chromatographic performance, detectability and matrix effect on five lettuce varieties.

The new method provided a 50 percent  reduction in the time for chromatographic analysis (from 30 to 15 minutes) with a lower mobile phase flow rate (0.147 mL/min) thus reducing the consumption of the mobile phase by 25 percent  and the injection of smaller sample amounts (1.7 μL). 

Lower quantification limits were obtained for almost all pesticides studied for green-lead lettuce. However, in relation to the matrix effect, four of the five types of lettuce studied presented higher matrix effects.


Chander Mohan

Krishi Jagran/New Delhi

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