Pesticide Residue Analysis | Sample Preparation | Extraction and Cleanup | USEPA 3620C

Summary

This video provides a detailed guide on the sample preparation process for pesticide residue analysis in vegetables, specifically using tomatoes. It covers the extraction of pesticide residues, column setup and conditioning, and the cleanup of the extract. The procedure involves using various laboratory equipment such as a rotary evaporator, separating funnel, and a fluorescence column. It also highlights the use of ethyl ether and hexane mixtures for elution, and the importance of proper pressure control during evaporation. The final extract is filtered and prepared for analysis via GC for pesticide quantification.

Takeaways

• 😀 The pesticide residue analysis process is crucial worldwide, particularly for fruits and vegetables, and involves sample preparation, extraction, column setup, conditioning, and cleanup of the extract.
• 😀 Tomato is used as the sample vegetable for pesticide residue analysis in this script.
• 😀 The first step in sample preparation is to chop the vegetable into small pieces using a clean knife and then blend it to form a paste.
• 😀 A separating funnel is used to separate the hexane layer after shaking the sample for two minutes. The upper hexane layer is then collected using a pipette.
• 😀 The extraction process involves repeating the shaking and separation three times to ensure thorough collection of the hexane layer.
• 😀 The concentrated sample extract is reduced to a volume of 10 to 20 ml using a rotary evaporator under controlled vacuum pressure.
• 😀 The rotary evaporator setup includes a vacuum pump, vacuum controller, and rotary evaporator unit, all necessary for concentrating the sample extract without loss.
• 😀 After concentration, the sample extract undergoes cleanup using the USPR3620C fluorescele method, which includes preparing a column for cleanup.
• 😀 Sodium sulfate and fluorescele are used for the column's conditioning and cleaning, with the mixture being heated to remove moisture content.
• 😀 The cleanup process involves eluting the sample extract through the prepared column with different mixtures of hexane and ethyl ether to purify the extract.
• 😀 The final extract is dissolved in 9 ml of hexane and then diluted to a volume of 10 ml in a volumetric flask. The solution is filtered and prepared for GC analysis.
• 😀 The result of the analysis is multiplied by a factor of 2 to account for the dilution factor during preparation before quantifying pesticide residues using GC.

Q & A

What is the purpose of this video?

The video demonstrates the sample preparation process for pesticide residue analysis in vegetables, specifically using a tomato sample.

What are the three main steps involved in the pesticide residue sample preparation process?

The three main steps are pesticide residue extraction, column setup and conditioning, and cleanup of the extract.

Which equipment is required for this pesticide residue analysis process?

The equipment required includes a balance machine, hot air oven, rotary evaporator, blender, vortex mixer, glass column, separating funnel, desiccator, chopping board, beakers, conical flasks, glass dishes, sodium sulfate anhydrous, activated fluorescel, and various solvents.

What is the first step in preparing the tomato sample for pesticide residue analysis?

The first step is to chop the tomato sample into small pieces using a clean knife, then blend it to form a paste.

How is the pesticide residue extracted from the tomato sample?

The tomato paste is transferred to a separating funnel, mixed with hexane, and shaken for 2 minutes. After allowing the funnel to stand for 10 minutes, the upper hexane layer is collected and repeated for two more rounds.

What role does the rotary evaporator play in the pesticide residue analysis?

The rotary evaporator is used to concentrate the pesticide extract by reducing its volume to 10-20 mL through evaporation under controlled vacuum pressure.

Why is proper pressure control important when using the rotary evaporator?

Proper pressure control is essential to prevent the loss of the extract and ensure the sample is concentrated without bumping, which could cause unwanted loss of analytes.

What is the purpose of the column setup and conditioning step?

The column setup and conditioning step is used to prepare a column with fluorescel and sodium sulfate to clean up the pesticide extract by removing moisture and other impurities.

How is the column used for cleanup during the pesticide residue analysis?

The extract is transferred into the prepared column, and it is eluted with various solvent mixtures (hexane, ethyl ether) to separate the pesticide residues from impurities.

What is the final step after cleaning the pesticide extract in the column?

The final step is to evaporate the solvent from the cleaned extract using a rotary evaporator, dissolve the residue in hexane, and filter the final extract before injecting it into a GC system for analysis.