Metabolism and Chemical Examination of Insecticides & Pesticides: UGC NET Forensic Science

UGC NET Forensic Science: Metabolism and Chemical Examination of Insecticides & Pesticides

Comprehensive notes and question pattern analysis for UGC NET Forensic Science aspirants, focusing on insecticides and pesticides in forensic toxicology.

Part 1: Notes on Metabolism and Chemical Examination of Insecticides & Pesticides

1. Introduction to Insecticides & Pesticides

Insecticides and pesticides are chemical agents used to control pests. In forensic science, they are analyzed in cases of poisoning, environmental contamination, and occupational exposure.

Key Concepts

• Insecticides: Target insects (e.g., organophosphates, carbamates).
• Pesticides: Include insecticides, herbicides, fungicides, rodenticides.
• Forensic Relevance: Detection in blood, urine, viscera, or environmental samples.

2. Metabolism of Insecticides & Pesticides

Metabolism transforms pesticides in the body, primarily in the liver, affecting toxicity and detection.

2.1. Phases of Metabolism

• Phase I: Oxidation, reduction, hydrolysis (e.g., parathion to paraoxon).
• Phase II: Conjugation with glucuronide or sulfate.
• Phase III: Excretion via urine, feces, or bile.

2.2. Metabolic Pathways by Class

Class	Metabolism	Key Metabolites	Forensic Notes
Organochlorines	Slow; stored in fat	DDE (DDT)	Persistent; detected in adipose tissue.
Organophosphates	Rapid; CYP450, esterases	Paraoxon, malaoxon	Inhibits acetylcholinesterase.
Carbamates	Hydrolysis, conjugation	Hydroxylated carbaryl	Reversible inhibition.
Pyrethroids	Oxidation, ester cleavage	3-Phenoxybenzoic acid	Low toxicity; rapid excretion.

3. Chemical Examination

3.1. Sample Collection and Preservation

• Biological: Blood, urine, viscera.
• Environmental: Soil, water.
• Preservation: Store at 4°C or -20°C; use sodium fluoride for blood.

3.2. Extraction Methods

• Solvent Extraction: Hexane, dichloromethane.
• Solid-Phase Extraction (SPE): For polar metabolites.
• Liquid-Liquid Extraction (LLE): For carbamates.

3.3. Presumptive Tests

• Zimmerman Test: Organophosphates (red-purple).
• Fujiwara Test: Organochlorines (pink).
• TLC: Separates compounds by Rf values.

3.4. Confirmatory Tests

• GC-MS: Volatile compounds (e.g., DDT).
• LC-MS/MS: Non-volatile metabolites.
• HPLC: Polar compounds (e.g., neonicotinoids).

Part 2: Deep Analysis of NTA-UGC NET Forensic Science Question Pattern

1. Overview of UGC NET Forensic Science Exam

The exam consists of Paper 1 (general aptitude) and Paper 2 (Forensic Science, Code 82), with 100 MCQs in Paper 2 (200 marks).

2. Question Pattern Analysis for Insecticides & Pesticides

2.1. Frequency and Weightage

2–4 questions per cycle (4–8 marks), focusing on classification, metabolism, and analytical techniques.

2.2. Types of Questions

• Factual: “Which is an organophosphate insecticide?”
• Application: “Which test detects organochlorines?”
• Analytical: “Which technique identifies malathion?”
• Case-Based: “Victim shows salivation. Which pesticide?”

2.3. Difficulty Level

• Easy: Common pesticides, symptoms.
• Moderate: Metabolism, presumptive tests.
• Difficult: Extraction, emerging pesticides.

Sample Questions

Which insecticide is an acetylcholinesterase inhibitor?

A) DDT

B) Malathion

C) Permethrin

D) Imidacloprid

Answer: B) Malathion
Explanation: Malathion, an organophosphate, inhibits acetylcholinesterase.

Which technique confirms DDT in adipose tissue?

A) UV-Vis

B) GC-MS

C) FTIR

D) NMR

Answer: B) GC-MS
Explanation: GC-MS is ideal for volatile organochlorines like DDT.

Preparation Tips

• Memorize pesticide classes and examples.
• Understand metabolic pathways and enzymes.
• Practice analytical techniques (GC-MS, LC-MS).
• Solve previous years’ papers (2019–2025).