FORENSIC TOXICOLOGICAL EXAMINATION
Forensic toxicological examination is the scientific analysis of biological and non-biological samples to detect, identify, and quantify toxic substances (poisons, drugs, chemicals) for medico-legal purposes.
It combines:
Analytical chemistry
Toxicology
Legal interpretation
As described in your material, it involves identification, detection, estimation and interpretation of poisons in the body .
Scope of Examination
Detection of:
Interpretation of:
Stages of Forensic Toxicological Examination
Collection of Samples
Samples depend on case type:
Fatal Cases (Postmortem)
Stomach & contents
Intestine
Liver, kidney
Blood
Urine
Brain, spleen
Hair, nails
Non-Fatal Cases
Blood
Urine
Vomit
Gastric lavage
Food/drink samples
These are essential because poisons distribute differently in body tissues .
Preservation of Samples
Extraction of Poison
Analysis
Interpretation
Depends on:
Sample type
Concentration
Pharmacological effect
Postmortem toxicology determines cause and manner of death .
Significance of Forensic Toxicological Examination
Medico-Legal Importance
Establish cause of death
Identify poisoning
Differentiate:
Accidental
Suicidal
Homicidal
Criminal Investigation
Court Evidence
Scientific proof
Expert testimony
Legal admissibility
Public Health Importance
BRANCHES OF TOXICOLOGY
According to your PDF, toxicology is divided into multiple specialized branches :
Forensic Toxicology
Clinical Toxicology
Pharmacological Toxicology
Occupational Toxicology
Environmental Toxicology
Other Modern Divisions (Expanded Scope)
CLASSIFICATION OF POISONS
BASED ON ORIGIN
Plant Poisons
Aconite
Datura
Nux vomica
Cannabis
Animal Poisons
Snake venom
Scorpion venom
Cantharides
Mineral Poisons
Synthetic Poisons
Pesticides
Drugs
Industrial chemicals
BASED ON MODE OF ACTION
Corrosive Poisons
Irritant Poisons
Types
Neurotic Poisons
Affect nervous system:
Cerebral
Spinal
Peripheral
Cardiac Poisons
Affect heart function
Examples:
Asphyxiants
Cause oxygen deprivation
Examples:
Carbon monoxide
Carbon dioxide
BASED ON CHEMICAL NATURE
Inorganic Poisons
Organic Poisons
Alkaloids
Glycosides
Pesticides
Gaseous Poisons
BASED ON MEDICO-LEGAL CLASSIFICATION
Homicidal Poisons
Characteristics:
Colourless
Tasteless
Highly toxic
Difficult to detect
Examples:
Suicidal Poisons
Easily available
Rapid action
Examples:
Accidental Poisoning
Occurs due to:
Negligence
Occupational exposure
Overdose
Examples:
Carbon monoxide
Pesticides
Stupefying Poisons
Examples:
Datura
Cannabis
Chloral hydrate
Abortifacient Poisons
Examples:
Miscellaneous
Cattle poisoning
Food poisoning
Drug overdose
BASED ON DURATION OF EXPOSURE
Acute Poisoning
Single large dose
Rapid symptoms
Chronic Poisoning
Repeated exposure
Gradual effects
Subacute Poisoning
Fulminant Poisoning
IMPORTANT CONCEPT (DOSE–RESPONSE RELATION)
Key principle (Paracelsus):
Types of Dose
Therapeutic dose
Toxic dose
Lethal dose (LD₅₀)
Effective dose (ED₅₀)
FACTORS AFFECTING TOXICITY
Dose
Route of administration
Age
Health condition
Tolerance
Synergism
FORENSIC SIGNS & SYMPTOMS (IMPORTANT TABLE)
Symptom | Possible Poison |
Vomiting | Arsenic |
Convulsions | Cyanide |
Coma | Barbiturates |
Delirium | Datura |
Paralysis | Snake venom |
(Based on chart in your PDF page)
CORE UNDERSTANDING
Forensic toxicology is a bridge between chemistry and law, involving:
Poison classification is essential because it helps:
Poisoning in India represents a major medico-legal and public health concern, involving:
Agricultural chemicals
Household toxins
Drugs of abuse
Plant and animal poisons
From a forensic perspective, poisoning must be analyzed in terms of:
Type of poison
Clinical manifestations
Toxicological detection
Appropriate antidote
POISONS COMMONLY ENCOUNTERED IN INDIA
Agricultural Poisons (Most Common in India)
Organophosphorus Compounds (OPC)
Examples:
Parathion
Malathion
Chlorpyrifos
Carbamates
Organochlorines
Household & Industrial Poisons
Kerosene
Phenol
Acids (H₂SO₄, HNO₃, HCl)
Alkalis (NaOH, KOH)
Metallic Poisons
Plant Poisons
Datura
Aconite
Nux vomica
Oleander
Animal Poisons
Snake venom
Scorpion venom
Drug-related Poisoning
Barbiturates
Benzodiazepines
Opioids
Gaseous Poisons
Carbon monoxide
Hydrogen sulphide
PATTERN OF POISONING IN INDIA
Suicidal Poisoning
Most common
Typically:
Pesticides
Organophosphates
Accidental Poisoning
Homicidal Poisoning
Stupefying Poisoning
SIGNS AND SYMPTOMS OF POISONING
GENERAL SYMPTOMS
Nausea
Vomiting
Abdominal pain
Headache
Confusion
SYSTEM-WISE SYMPTOMS
Gastrointestinal System
Vomiting
Diarrhea
Burning sensation
Common Poisons:
Nervous System
Examples:
Datura → delirium
Cyanide → convulsions
Barbiturates → coma
Respiratory System
Difficulty breathing
Respiratory depression
Examples:
Cardiovascular System
Irregular heartbeat
Cardiac arrest
Examples:
Skin and Eye Effects
Examples:
Characteristic Clinical Signs
Sign | Poison |
Pinpoint pupils | Opioids |
Dilated pupils | Datura |
Garlic odor | Arsenic, phosphorus |
Bitter almond smell | Cyanide |
Cherry red skin | Carbon monoxide |
MECHANISM-BASED SYMPTOMS
Cholinergic Syndrome (OP Poisoning)
Salivation
Sweating
Lacrimation
Bronchospasm
CNS Depression
Neurotoxicity
ANTIDOTES (DETAILED)
Definition
An antidote is a substance that counteracts the effects of a poison.
Types of Antidotes
Physical Antidotes
Activated charcoal
Adsorb poison
Chemical Antidotes
Physiological Antidotes
SPECIFIC ANTIDOTES FOR COMMON POISONS
Organophosphorus Compounds
Atropine
Pralidoxime (2-PAM)
Cyanide
Opioids
Barbiturates
No specific antidote
Supportive treatment
Benzodiazepines
Methanol
Carbon Monoxide
Heavy Metals
Arsenic
Lead
Mercury
GENERAL MANAGEMENT OF POISONING
Decontamination
Gastric lavage
Activated charcoal
Supportive Treatment
Airway management
Oxygen therapy
IV fluids
Elimination Enhancement
FORENSIC SIGNIFICANCE
Helps identify:
Type of poison
Mode of administration
Assists in:
IMPORTANT CONCEPT (FROM YOUR PDF)
LIMITATIONS
Symptoms may overlap
Mixed poisoning cases
Delayed detection
CORE UNDERSTANDING
Poisoning analysis requires integration of:
Antidotes work by:
Neutralizing poison
Blocking its action
Enhancing elimination
FACTORS AFFECTING THE INTENSITY (SEVERITY) OF POISONING
Concept
The intensity of poisoning depends on how a toxic substance interacts with the body, which is governed by:
This is rooted in the principle:
DOSE OF POISON
Definition
Amount of poison entering the body.
Types of Dose
Therapeutic dose → beneficial
Toxic dose → produces harmful effects
Lethal dose (LD₅₀) → causes death
Effect
ROUTE OF ADMINISTRATION
Common Routes
Oral
Inhalation
Injection
Dermal
Effect on Toxicity
Route | Effect |
Inhalation | Rapid action |
Injection | Immediate effect |
Oral | Slower (depends on absorption) |
Skin | Slow (unless lipid-soluble poison) |
PHYSICAL STATE OF POISON
CHEMICAL NATURE OF POISON
Solubility
Volatility
Stability
Examples
RATE OF ABSORPTION
Depends on:
Blood flow
Surface area
Presence of food
Example
DISTRIBUTION IN BODY
Poison | Target Organ |
Arsenic | Liver |
Lead | Bones |
Mercury | Brain |
METABOLISM (BIOTRANSFORMATION)
Example
EXCRETION
Effect
AGE
SEX
BODY WEIGHT AND HEALTH
TOLERANCE
Example
IDIOSYNCRASY
ALLERGY (HYPERSENSITIVITY)
COMBINATION OF POISONS (SYNERGISM)
Example
ENVIRONMENTAL FACTORS
Temperature
Humidity
Surrounding conditions
IMPORTANCE OF POST-MORTEM EXAMINATION IN POISONING CASES
Definition
Post-mortem examination (autopsy) is the systematic examination of a dead body to determine cause of death, including detection of poisoning.
OBJECTIVES IN POISONING CASES
Identify:
Poison involved
Cause of death
Determine:
Time since death
Mode of poisoning
ROLE OF POST-MORTEM IN POISON DETECTION
COLLECTION OF SPECIMENS
Viscera Collection
Stomach and contents
Intestine
Liver
Kidney
Blood
Urine
Special Samples
IDENTIFICATION OF POISON
Detection of:
Chemical toxins
Drugs
Metals
OBSERVATION OF MORPHOLOGICAL CHANGES
External Findings
Burns (acids/alkalis)
Cyanosis
Odor (almond, garlic)
Internal Findings
Corrosion of stomach
Organ damage
Congestion
CORRELATION WITH CLINICAL HISTORY
Symptoms before death
Medical treatment
DETERMINATION OF CAUSE OF DEATH
Poison vs natural cause
Direct vs indirect cause
ESTIMATION OF TIME SINCE DEATH
MEDICO-LEGAL SIGNIFICANCE
Provides:
Evidence in court
Expert opinion
PRESERVATION OF EVIDENCE
LIMITATIONS OF POST-MORTEM IN POISONING
FORENSIC SIGNIFICANCE (INTEGRATED VIEW)
CORE UNDERSTANDING
Intensity of poisoning depends on:
Post-mortem examination is essential because:
In suspected poisoning, the crime scene may include:
Residence, workplace, hotel room, vehicle, or open field
Food/drink sources, medicines, pesticides, or chemicals
The investigating officer (IO) must gather complete background information and ensure scientific handling of evidence so that toxicological results remain valid and legally admissible.
INFORMATION TO BE COLLECTED BY INVESTIGATING OFFICERS
Victim-Centered Information
Identity & demographics: age, sex, occupation
Medical history:
Ongoing illnesses (liver/kidney disease)
Current medications (prescription/OTC/herbal)
History of substance use (alcohol, drugs)
Symptoms before incident:
Vomiting, convulsions, delirium, coma
Time of onset and progression
Dietary history:
Psychosocial background:
Stress, depression, prior attempts
Recent disputes, threats, financial issues
Circumstantial Information
Time–place details:
Exact time of suspected exposure
Location(s) involved (home, field, factory)
Events timeline:
Access and opportunity:
Scene-Specific Information
Presence of potential toxic agents:
Food and drink items:
Signs of struggle or tampering:
Environmental context:
Witness statements:
Digital/communication evidence:
Medical/Clinical Information (from treating facility)
PRECAUTIONS DURING SCENE SEARCH (SAFETY & SCIENTIFIC APPROACH)
Personal Safety
Use personal protective equipment (PPE):
Beware of:
Ensure adequate ventilation before entry
Avoid eating, drinking, or touching face at scene
Scene Security
Cordon off the area; restrict entry
Maintain scene integrity; prevent disturbance
Establish a single entry/exit point with log
Systematic Search
Avoiding Contamination
Use clean tools for each sample
Change gloves between items
Do not mix samples; avoid cross-contact
Keep control (blank) samples from nearby uncontaminated areas
Handling Volatile Substances
EVIDENCE COLLECTION IN POISONING CASES
Types of Evidence
Biological Samples (if available at scene)
Non-Biological (Critical in poisoning)
Suspected poison containers (bottles, sachets)
Medicines (strips, vials, syringes)
Food and drink samples (solid/liquid)
Utensils, cups, glasses, spoons
Soil/water (environmental poisoning)
Packaging materials and labels
Collection Procedures
Packaging Guidelines
Liquids → airtight glass containers with tight caps
Volatile substances → hermetically sealed containers (headspace preserved)
Solids/powders → clean glass/plastic containers or paper packets (as appropriate)
Biological samples → sterile, leak-proof containers; refrigerate if required
Preservation
Documentation & Chain of Custody
Maintain complete documentation:
Seizure memo/panchnama
Sample inventory
Record every transfer with date, time, signatures
Ensure continuity from scene → storage → laboratory
SPECIAL CONSIDERATIONS
Food/Drink Poisoning
Gas/Volatile Poisoning
Suspected Homicide
COMMON ERRORS TO AVOID
Delayed collection → degradation/loss
Improper sealing → contamination/tampering
Mixing samples → loss of evidentiary value
Incomplete labeling → chain-of-custody breaks
Using wrong containers → chemical interaction or leakage
FORENSIC SIGNIFICANCE
CORE UNDERSTANDING
Effective investigation in poisoning cases depends on:
Comprehensive background information
Strict scene safety and contamination control
Methodical, well-documented evidence collection
Control over poisons and drugs in India is governed by a combination of statutes that regulate:
Import, manufacture, sale, possession and distribution
Licensing and record-keeping
Quality, safety, and misbranding/adulteration
Key legislations include:
Poisons Act, 1919
Drugs and Cosmetics Act, 1940 (with subsequent amendments and rules, notably 1945 Rules; later amendments such as 1964, 1982, 2008 etc.)
“Drugs Act 1940 and 1955” in exam syllabi usually refers to the Drugs & Cosmetics Act, 1940 along with its Rules (1945) and later amendments that strengthened control, quality standards, and enforcement.
POISONS ACT, 1919
Objective
To regulate the import, possession, and sale of poisons and prevent their misuse.
Scope
Key Provisions
Control of Sale (Section 3)
Possession of Poison
Labeling Requirements
Containers must carry:
Name of poison
Warning label
Seller details
Transport & Import
Powers of State Government
Penalties
Forensic Significance
Helps trace:
Source of poison
Purchase history
Crucial in:
DRUGS & COSMETICS ACT, 1940
Objective
To regulate:
Import, manufacture, distribution, and sale of drugs and cosmetics
Ensure safety, efficacy, and quality
Scope
Applies to:
Pharmaceuticals
Biological products
Cosmetics
Key Definitions
Drug
Includes:
Misbranded Drug
Adulterated Drug
Spurious Drug
IMPORTANT PROVISIONS
Import of Drugs
Prohibited if:
Misbranded
Adulterated
Spurious
Manufacture and Sale
Quality Control
Establishment of:
Standards defined under:
Drugs Technical Advisory Board (DTAB)
Drugs Consultative Committee (DCC)
DRUGS & COSMETICS RULES, 1945 (IMPORTANT)
Purpose
Key Features
Important Schedules (Exam-Oriented)
Schedule | Purpose |
Schedule H | Prescription drugs |
Schedule X | Narcotic/psychotropic drugs (strict control) |
Schedule G | Drugs requiring caution |
Schedule Y | Clinical trials |
IMPORTANT AMENDMENTS (OVERVIEW)
1964 Amendment
1982 Amendment
2008 Amendment
Recent Updates
Focus on:
Online drug regulation
Clinical trials
Pharmacovigilance
PENALTIES UNDER DRUGS & COSMETICS ACT
Manufacture/sale of:
Includes:
COMPARISON: POISONS ACT vs DRUGS & COSMETICS ACT
Feature | Poisons Act 1919 | Drugs & Cosmetics Act 1940 |
Focus | Poisons control | Drugs & cosmetics regulation |
Authority | State government | Central + State |
Scope | Sale & possession | Manufacture, import, sale |
Records | Mandatory for poisons | Licensing & standards |
Forensic Role | Trace poison source | Identify drug quality |
FORENSIC SIGNIFICANCE
Helps:
Supports:
Criminal investigation
Court evidence
Links:
LIMITATIONS
CORE UNDERSTANDING
Legal control of poisons and drugs ensures:
In forensic cases:
In forensic toxicology, a matrix is the medium in which a poison exists. It is not an inert carrier; rather, it actively influences:
A clear understanding of matrices is essential because the choice of matrix determines the success of extraction and identification.
Classification of Matrices
Biological Matrices
Biological matrices are materials obtained from the human or animal body. These are chemically complex systems composed of proteins, lipids, enzymes, and electrolytes, all of which can interact with toxic substances.
Blood
Blood is the most significant matrix in toxicology because it reflects the circulating concentration of a poison at a given time. It is directly related to pharmacological and toxic effects.
Blood contains binding proteins such as albumin, which can bind drugs and reduce their free concentration. This creates analytical challenges known as matrix effects, where components interfere with detection.
In postmortem cases, redistribution of drugs from organs like liver and lungs into blood may occur, altering concentration levels. Peripheral blood is generally more reliable than central blood.
Urine
Urine is an excretory matrix that contains metabolites of poisons rather than the original compound. It is useful for detecting exposure over a longer duration.
Because many substances are concentrated in urine, it provides higher sensitivity for screening. However, it does not reflect the actual level of intoxication at a given time.
Saliva
Saliva reflects the free fraction of a drug in blood, making it useful for understanding pharmacologically active concentration. It is easy to collect and non-invasive.
Hair
Hair provides a historical record of exposure. Drugs enter hair through blood supply and become trapped in the keratin structure.
Segmental analysis of hair can reveal exposure over time. However, external contamination and cosmetic treatments can complicate interpretation.
Nails
Nails are similar to hair in composition and accumulate toxins over time. They are particularly useful for detecting heavy metal exposure in chronic poisoning cases.
Vomit and Gastric Contents
These matrices contain unabsorbed poison and are highly useful in recent ingestion cases. The presence of intact poison may provide direct evidence of ingestion.
Non-Biological Matrices
Non-biological matrices originate from the environment or crime scene and often contain poison in its original or modified form.
Food and Beverages
Food matrices are chemically complex and may alter the poison due to cooking or storage. Uneven distribution of poison is common, making sampling critical.
Water and Soil
These matrices are relevant in environmental or accidental poisoning. They often require filtration and concentration before analysis.
Pharmaceutical Preparations
Tablets and capsules contain both active drugs and excipients such as starch and lactose. Extraction must separate the active component from these additives.
Containers and Surfaces
Residues found on bottles, utensils, or glassware can provide trace evidence linking poison to a suspect or source.
Clothing and Fabrics
Poisons may be absorbed through skin or spilled onto clothing. These matrices are important in dermal exposure cases.
Viscera
Viscera refers to internal organs collected during postmortem examination. These are crucial in forensic toxicology because they reflect distribution, metabolism, and accumulation of poison.
Stomach
The stomach is the primary site for ingested poisons. It may contain unabsorbed substances and helps estimate time since ingestion.
Liver
The liver is the most important organ in toxicology because it is the site of metabolism. Many poisons are found in higher concentration here due to biotransformation processes.
Kidney
The kidney is involved in excretion and is useful for detecting water-soluble toxins.
Brain
The brain accumulates lipid-soluble substances and is important in cases involving central nervous system depressants or stimulants.
General Distribution Insight
Different poisons preferentially accumulate in different organs. Understanding this distribution is essential for selecting the correct matrix.
Volatile Poisons
Definition
Volatile poisons are substances that easily vaporize at room temperature or slightly elevated temperatures. Their detection is challenging because they can be lost during handling.
Organic Volatile Poisons
These include:
These compounds are generally lipophilic and distribute rapidly in the body.
Inorganic Volatile Poisons
These include:
hydrogen cyanide
carbon monoxide
hydrogen sulphide
They often act rapidly and are highly toxic even at low concentrations.
Principles of Extraction of Volatile Poisons
Extraction of volatile poisons requires careful handling because:
Important considerations include:
Methods of Extraction
Distillation
Distillation is based on differences in boiling points and vapour pressure. It is the most fundamental technique for extracting volatile poisons.
Simple Distillation
In this method, the sample is heated and volatile components vaporize. These vapours are then condensed and collected.
This method is suitable for relatively stable compounds such as alcohols but may cause decomposition of heat-sensitive substances.
Steam Distillation
Steam distillation allows volatile compounds to evaporate at temperatures lower than their normal boiling point. This is possible because the total vapour pressure is the sum of the vapour pressures of water and the compound.
This method is particularly useful for:
It prevents thermal decomposition and preserves chemical integrity.
Fractional Distillation
Fractional distillation separates mixtures of volatile substances based on small differences in boiling points. It uses a fractionating column to achieve better separation.
Headspace Analysis
Headspace analysis is based on the distribution of volatile compounds between the liquid phase and the gas phase above it.
When a sealed sample is heated, volatile compounds move into the gas phase. This gas is then analyzed.
This method is widely used for:
alcohol analysis
solvent detection
It minimizes contamination and preserves the sample.
Purge and Trap Technique
In this method, an inert gas is passed through the sample, carrying volatile compounds. These are trapped on an adsorbent material and later released for analysis.
This technique is highly sensitive and suitable for trace-level detection.
Solid Phase Microextraction (SPME)
A coated fibre absorbs volatile compounds directly from the sample or headspace. The compounds are then desorbed into an analytical instrument.
This method is:
Extraction of Inorganic Volatile Poisons
Cyanide
Cyanide is converted into hydrogen cyanide gas under acidic conditions. The gas is then trapped in an alkaline solution for analysis.
Carbon Monoxide
Carbon monoxide binds with hemoglobin to form carboxyhemoglobin. Detection is carried out using spectrophotometric methods rather than extraction.
Hydrogen Sulphide
Hydrogen sulphide can be liberated as gas and absorbed in suitable solutions for detection.
Integrated Understanding
The success of toxicological analysis depends on the relationship between:
Biological matrices introduce complexity due to metabolism and binding. Non-biological matrices may preserve the poison in its original form. Viscera provides insight into distribution and accumulation.
Volatile poisons require specialized handling because they can be lost easily. Methods such as headspace analysis and steam distillation are preferred because they preserve the integrity of these compounds.
SOLVENT EXTRACTION
Principle
Based on partition of a compound between two immiscible phases (usually aqueous and organic). The poison distributes according to its partition coefficient.
Chemical Basis
K= C organic / C aqueous
Where K depends on:
Polarity
pH
Ionization of compound
Process
Sample (blood, urine, viscera homogenate) is prepared
Adjust pH depending on drug nature:
Add organic solvent:
Ether
Chloroform
Dichloromethane
Shake thoroughly
Allow phase separation
Collect organic layer
Evaporate solvent to obtain residue
Applications
Alkaloids
Barbiturates
Benzodiazepines
Organic poisons
Advantages
Limitations
DISTILLATION
Principle
Separation based on difference in boiling points and volatility.
Process
Sample placed in distillation flask
Heated gradually
Volatile poison vaporizes
Vapours condensed using condenser
Collected in receiver
Applications
Alcohol
Acetone
Volatile solvents
Limitations
STEAM DISTILLATION
Principle
Volatile substances co-distill with steam at lower temperature than their boiling point.
Chemical Concept
P (total ) =P water+P compound
Process
Applications
Essential oils
Organic volatile poisons
Phenolic compounds
Advantages
MICRODIFFUSION
Principle
Based on diffusion of volatile substances across a semi-permeable barrier from one compartment to another.
Process
Sample placed in outer chamber
Reagent placed in inner chamber
Poison diffuses as gas
Reacts with reagent forming detectable product
Example
Applications
Cyanide
Ammonia
Volatile toxic gases
Advantages
DIALYSIS
Principle
Separation based on diffusion of small molecules through a semi-permeable membrane.
Mechanism
Process
Applications
Removal of:
Proteins
Interfering substances
Used before:
Advantages
Limitations
DRY ASHING
Principle
Organic matter is destroyed by heating at high temperature, leaving inorganic residue.
Process
Sample placed in crucible
Heated in furnace (400–600°C)
Organic material burns off
Residue dissolved in acid
Applications
Advantages
Limitations
Loss of volatile metals
Time-consuming
WET DIGESTION
Principle
Organic matter is destroyed using strong acids and oxidizing agents.
Reagents
Nitric acid
Sulphuric acid
Perchloric acid
Process
Sample mixed with acids
Heated gently
Organic matter oxidized
Clear solution obtained
Used for analysis
Applications
Heavy metals
Inorganic poisons
Advantages
Limitations
COMPARATIVE SUMMARY
Method | Principle | Used For |
Solvent extraction | Partition | Organic drugs |
Distillation | Boiling point | Volatile liquids |
Steam distillation | Co-distillation | Heat-sensitive volatiles |
Microdiffusion | Gas diffusion | Cyanide |
Dialysis | Membrane diffusion | Protein removal |
Dry ashing | Thermal destruction | Metals |
Wet digestion | Acid oxidation | Metals |
MATRIX–METHOD RELATION
Matrix | Suitable Method |
Blood | Solvent extraction |
Urine | Dialysis + extraction |
Viscera | Digestion + extraction |
Food | Solvent extraction |
Metals | Wet digestion / dry ashing |
FORENSIC SIGNIFICANCE
Correct method ensures:
Improper method may:
Destroy poison
Lead to false results
CORE UNDERSTANDING
Each extraction method is selected based on:
Forensic toxicology requires:
Modified Stas–Otto Method & Ammonium Sulphate Method — Detailed Forensic Toxicology Notes
These classical extraction methods are designed for isolating organic poisons (especially alkaloids and many drugs) from complex matrices such as viscera, blood, and food. They rely on acid–base chemistry, solubility, and protein removal.
MODIFIED STAS–OTTO METHOD
Concept and Scope
The Stas–Otto method is a systematic acid–base extraction technique developed to isolate a wide range of organic poisons. The modified version improves:
It is particularly useful for:
alkaloids (morphine, strychnine, atropine)
many acidic, basic, and neutral drugs
plant poisons
Chemical Basis
Acidification converts basic drugs (alkaloids) into water-soluble salts
Basification converts them back into free bases, which are organic-solvent soluble
Sequential extraction allows fractionation into acidic, basic, and neutral components
Detailed Process
Sample Preparation
Purpose:
Acidification
Effect:
Filtration
Removal of Organic Impurities
Purpose:
Removes fats, pigments, neutral impurities
Leaves alkaloids in aqueous acidic phase
Basification
Effect:
Extraction of Alkaloids
Extract with organic solvents:
Shake and separate layers
Organic layer now contains alkaloids
Evaporation
Further Purification
Fractionation Approach (Advanced Understanding)
The method can separate compounds into:
Acidic fraction → extracted at acidic pH
Basic fraction → extracted after basification
Neutral fraction → extracted initially
Applications
Morphine
Strychnine
Atropine
Nicotine
Many plant alkaloids
Advantages
Limitations
AMMONIUM SULPHATE METHOD
Concept and Scope
This method is based on protein precipitation (“salting out”) using ammonium sulphate, followed by extraction of poisons.
It is particularly useful for:
Chemical Principle
Ammonium sulphate:
reduces solubility of proteins
causes precipitation of proteins
releases bound drugs into solution
Mechanism (Salting Out)
Detailed Process
Sample Preparation
Addition of Ammonium Sulphate
Effect:
Filtration or Centrifugation
Extraction
Evaporation
Organic layer evaporated
Residue contains poison
Further Analysis
Applications
Advantages
Efficient protein removal
Improves extraction efficiency
Suitable for biological fluids
Limitations
COMPARATIVE UNDERSTANDING
Feature | Modified Stas–Otto | Ammonium Sulphate Method |
Principle | Acid–base extraction | Protein precipitation |
Target compounds | Alkaloids, organic poisons | Protein-bound drugs |
Matrix | Viscera, food | Blood, serum |
Key step | pH manipulation | Salting out |
Complexity | High | Moderate |
INTEGRATED FORENSIC INTERPRETATION
CRITICAL INSIGHT
CORE UNDERSTANDING
Extraction in forensic toxicology is not just a procedure but a chemical strategy:
Only after proper extraction can:
Identification
Quantification
Legal interpretation
be reliably performed.
After a poison/drug is extracted from a matrix, it still contains:
Therefore, isolation and clean-up are essential before chromatographic analysis to:
ISOLATION AND CLEAN-UP PROCEDURES
Concept
Isolation refers to separating the analyte (poison/drug) from interfering substances, while clean-up refers to removal of unwanted matrix components.
ROLE IN FORENSIC TOXICOLOGY
Prevents:
matrix interference
false results
Improves:
MAJOR CLEAN-UP TECHNIQUES
Protein Precipitation
Principle
Proteins are denatured using:
Process
Application
Liquid–Liquid Extraction (LLE)
Principle
Partition of analyte between:
aqueous phase
organic phase
Process
Clean-Up Role
Removes polar impurities
Concentrates analyte
Solid Phase Extraction (SPE)
Principle
Analyte is retained on a solid adsorbent and impurities are washed away.
Mechanism
Types of SPE Sorbents
C18 (non-polar)
Ion exchange
Mixed-mode
Advantages
High purity extract
Automation possible
High reproducibility
Filtration and Centrifugation
Purpose
Application
Derivatization (Advanced Clean-Up)
Principle
Chemical modification of analyte to:
increase volatility
improve detectability
Application
SEPARATION OF POISONS AND DRUGS USING CHROMATOGRAPHY
THIN LAYER CHROMATOGRAPHY (TLC)
Principle
Separation based on:
Mechanism
Stationary phase: silica gel
Mobile phase: solvent system
Components move at different rates
Procedure
Detection
Output
Application
Preliminary screening
Multiple drug separation
HIGH PERFORMANCE THIN LAYER CHROMATOGRAPHY (HPTLC)
Advancement over TLC
Detection
GAS CHROMATOGRAPHY (GC)
Principle
Separation based on:
Mechanism
Sample vaporized
Carried by inert gas
Separated in column
Detector
Applications
Volatile drugs
Organic solvents
HIGH PERFORMANCE LIQUID CHROMATOGRAPHY (HPLC)
Principle
Separation based on:
Mechanism
Types
Detection
UV detector
Diode array detector
Applications
GAS CHROMATOGRAPHY–MASS SPECTROMETRY (GC–MS)
Principle
GC separates compounds
MS identifies them
Mechanism
Ionization
Fragmentation
Detection
Output
Application
LIQUID CHROMATOGRAPHY–MASS SPECTROMETRY (LC–MS)
Principle
Mechanism
Application
Benzodiazepines
Barbiturates
Designer drugs
ION CHROMATOGRAPHY (SPECIALIZED)
Principle
Separation of ionic compounds
Application
Inorganic poisons
Cyanide
Fluoride
KEY PARAMETERS IN CHROMATOGRAPHY
Retention Time
Resolution
Selectivity
Sensitivity
INTEGRATED WORKFLOW
FORENSIC SIGNIFICANCE
LIMITATIONS
Matrix interference
Co-elution of compounds
Instrumental cost
CORE UNDERSTANDING
Isolation and clean-up are essential because:
Chromatography works by:
Accurate forensic analysis requires:
After extraction and clean-up, the next critical stage in forensic toxicology is:
This is achieved using spectrophotometric and advanced instrumental techniques, which provide:
sensitivity
specificity
reproducibility
legal reliability
SPECTROPHOTOMETRIC METHODS
Ultraviolet–Visible (UV–Vis) Spectrophotometry
Principle
Molecules absorb UV or visible light due to electronic transitions:
The amount of light absorbed is directly proportional to concentration.
Beer–Lambert Law
A=εclA = \varepsilon c lA=εcl
εεε
ccc
lll
Process
Applications
Barbiturates
Benzodiazepines
Alkaloids
Phenolic compounds
Advantages
Limitations
Low specificity
Interference from matrix
Colorimetric Methods
Principle
Formation of coloured complexes between poison and reagent.
Examples
Application
Preliminary estimation
Screening
INFRARED SPECTROSCOPY (FTIR)
Principle
Absorption of IR radiation leads to vibrational transitions of chemical bonds.
Mechanism
Each functional group absorbs at a specific frequency, producing a fingerprint spectrum.
Applications
Advantages
Non-destructive
Highly specific
Limitations
RAMAN SPECTROSCOPY
Principle
Based on inelastic scattering of light (Raman effect).
Mechanism
Laser light interacts with molecules → scattered light shows energy shift → molecular fingerprint.
Applications
Advantages
Limitations
ATOMIC ABSORPTION SPECTROSCOPY (AAS)
Principle
Atoms absorb light at characteristic wavelengths.
Mechanism
Applications
Advantages
High sensitivity
Element-specific
INDUCTIVELY COUPLED PLASMA (ICP) TECHNIQUES
ICP-OES / ICP-MS
Principle
Applications
Trace metal analysis
Multi-element detection
CHROMATOGRAPHIC INSTRUMENTAL METHODS
Gas Chromatography (GC)
Principle
Separation based on:
Applications
Alcohol
Organic solvents
Volatile drugs
High Performance Liquid Chromatography (HPLC)
Principle
Separation based on:
Applications
Non-volatile drugs
Barbiturates
Benzodiazepines
GC–Mass Spectrometry (GC–MS)
Principle
GC separates
MS identifies
Mechanism
Ionization
Fragmentation
Detection of m/z ratio
Output
Applications
Confirmatory analysis
Drug identification
LC–Mass Spectrometry (LC–MS)
Principle
Applications
Thermally unstable drugs
Designer drugs
Toxic compounds
OTHER IMPORTANT TECHNIQUES
Fluorescence Spectroscopy
Principle
Emission of light after excitation
Applications
Electrochemical Methods
Principle
Measurement of:
Applications
IDENTIFICATION VS ESTIMATION
Identification
Determines:
Based on:
spectra
retention time
fragmentation pattern
Estimation
Determines:
Based on:
calibration curves
peak area
SIGNIFICANCE OF ANALYTICAL STUDIES IN FORENSIC EXAMINATION
Establishing Cause of Death
Legal Evidence
Linking Evidence
Connects:
poison → source
victim → exposure
Differentiation of Cases
Accidental
Suicidal
Homicidal
Drug Abuse Monitoring
Identification of:
illicit drugs
designer substances
Quality and Reliability
Ensures:
reproducibility
accuracy
validity
LIMITATIONS
Matrix interference
Need for standards
Instrumental cost
Expertise required
CORE UNDERSTANDING
Spectrophotometric and instrumental methods are the backbone of modern forensic toxicology.
They allow:
Analytical studies are significant because they:
Forensic analysis of poisons is guided by:
Chemical nature of substance
Matrix (blood, viscera, environment)
Stability (volatile vs non-volatile)
The analytical strategy typically involves:
ANALYSIS OF GASES AND VOLATILE POISONS
Concept
Gases and volatile poisons are:
Carbon Monoxide (CO)
Toxic Mechanism
Sample
Analysis
Spectrophotometry
CO-Oximetry
Observation
Hydrogen Cyanide (HCN)
Toxic Mechanism
Extraction
Tests
Prussian Blue Test
Pyridine–Barbituric Acid Test
Instrumental Methods
Hydrogen Sulphide (H₂S)
Mechanism
Detection
Alcohols (Ethanol, Methanol)
Analysis
Headspace Gas Chromatography
Screening
Other Volatile Poisons
Chloroform, Ether
ANALYSIS OF TOXIC METALS
Common Toxic Metals
Arsenic
Lead
Mercury
Cadmium
Sample Preparation
Classical Tests
Arsenic
Marsh Test
Gutzeit Test
Lead
Mercury
Instrumental Analysis
Atomic Absorption Spectroscopy (AAS)
ICP-MS / ICP-OES
Multi-element detection
Highly sensitive
X-Ray Fluorescence (XRF)
ANALYSIS OF TOXIC ANIONS
Common Anions
Cyanide (CN⁻)
Fluoride (F⁻)
Nitrate (NO₃⁻)
Sulphate (SO₄²⁻)
Detection Methods
Cyanide
Prussian blue test
Spectrophotometry
Fluoride
Nitrate
Sulphate
Instrumental Methods
Ion Chromatography
Spectrophotometry
ANALYSIS OF PESTICIDES
Classification
Organophosphorus Compounds
Organochlorines
Carbamates
Pyrethroids
Extraction
Solvent extraction
Clean-up using SPE
Screening Tests
Cholinesterase Inhibition Test
Colour Tests
Chromatographic Analysis
Gas Chromatography (GC)
Preferred for:
Organochlorines
Organophosphates
HPLC
Used for:
Carbamates
Non-volatile pesticides
Confirmatory Techniques
GC–MS
LC–MS
Residue Analysis
Food
Water
Soil
Biological samples
FORENSIC SIGNIFICANCE
LIMITATIONS
CORE UNDERSTANDING
Different classes of poisons require:
Gases → indirect or headspace analysis
Metals → digestion + atomic spectroscopy
Anions → ion-specific detection
Pesticides → chromatography + mass spectrometry
Accurate forensic interpretation depends on:
Pesticides encountered in forensic cases are typically:
lipophilic or semi-polar organic compounds
present in complex matrices (viscera, blood, food, soil)
Analytical approach involves:
extraction and clean-up
screening (colour/enzymatic tests)
chromatographic separation
confirmatory instrumental analysis
ORGANOCHLORINATED PESTICIDES
Examples and Common Names
Chemical Nature
Toxic Action
Extraction
Screening Tests
Chromatographic Analysis
Confirmatory Methods
ORGANOPHOSPHORUS PESTICIDES
Examples
Parathion
Malathion
Chlorpyrifos
Diazinon
Chemical Nature
Toxic Mechanism
Extraction
SCREENING TESTS
Cholinesterase Inhibition Test
p-Nitrophenol Formation Test
Chromatographic Analysis
Confirmatory Methods
CARBAMATES
Examples
Carbaryl
Carbofuran
Aldicarb
Chemical Nature
Toxic Mechanism
Extraction
SCREENING TESTS
Cholinesterase Inhibition Test
Colour Tests
Chromatographic Analysis
Confirmatory Methods
PYRETHROIDS
Examples
Permethrin
Cypermethrin
Deltamethrin
Chemical Nature
Toxic Mechanism
Extraction
SCREENING
Chromatographic Analysis
Confirmatory Methods
ALUMINIUM PHOSPHIDE
Common Name
Chemical Nature
Toxic Mechanism
Extraction
SCREENING TESTS
Silver Nitrate Test
Mercuric Chloride Paper Test
Ammonium Molybdate Test
Instrumental Methods
Gas chromatography
Spectrophotometry
ZINC PHOSPHIDE
Common Use
Chemical Nature
Extraction
SCREENING TESTS
Confirmatory Methods
COMPARATIVE UNDERSTANDING
Class | Mechanism | Key Test | Instrument |
Organochlorine | CNS toxicity | GC-ECD | GC-MS |
Organophosphate | AChE inhibition | Cholinesterase test | GC-MS |
Carbamates | Reversible AChE inhibition | Enzyme test | HPLC |
Pyrethroids | Sodium channel effect | Instrumental | GC-MS |
Aluminium phosphide | PH₃ release | Silver nitrate | GC |
Zinc phosphide | PH₃ release | Silver nitrate | GC |
FORENSIC SIGNIFICANCE
Common in:
Detection helps:
Establish cause of death
Identify source
Link suspect to poison
LIMITATIONS
CORE UNDERSTANDING
Each pesticide class has:
Distinct chemical structure
Specific mechanism of toxicity
Characteristic analytical approach
Accurate analysis requires:
In forensic toxicology, organic drugs and poisons are broadly grouped based on acid–base properties:
This classification is crucial because:
It determines extraction method
Controls solubility and ionization
Guides chromatographic and instrumental analysis
CHEMICAL BASIS OF CLASSIFICATION
Ionization Concept
Acidic drugs → donate proton (exist as anions at high pH)
Basic drugs → accept proton (exist as cations at low pH)
Neutral drugs → do not ionize significantly
pH–Partition Principle
This principle is the basis of acid–base extraction techniques.
GENERAL ANALYTICAL APPROACH
Sample preparation (viscera, blood, urine)
Acid–base extraction
Fractionation:
acidic fraction
neutral fraction
basic fraction
Clean-up
Chromatographic separation
Instrumental confirmation
ANALYSIS OF ACIDIC DRUGS AND POISONS
Examples
Barbiturates
Salicylates (aspirin)
Phenolic compounds
Some herbicides
Chemical Nature
Extraction Method
Acidic Medium Extraction
Sample acidified (low pH)
Acidic drugs remain non-ionized
Extracted into organic solvent:
Back Extraction (Optional)
SCREENING TESTS
Ferric Chloride Test
UV–Vis Spectrophotometry
Chromatographic Methods
Confirmatory Techniques
ANALYSIS OF BASIC (ALKALINE) DRUGS AND POISONS
Examples
Alkaloids:
Morphine
Strychnine
Atropine
Amphetamines
Cocaine
Nicotine
Chemical Nature
Weak bases
Contain nitrogen atoms
Extraction Method
Acidic Extraction
Basification
Organic Extraction
SCREENING TESTS
Dragendorff’s Test
Mayer’s Test
Wagner’s Test
Chromatographic Methods
Confirmatory Techniques
ANALYSIS OF NEUTRAL DRUGS AND POISONS
Examples
Steroids
Some pesticides
Chloral hydrate
Organic solvents
Chemical Nature
Extraction Method
Direct Solvent Extraction
SCREENING
Chromatographic Methods
Confirmatory Techniques
FRACTIONATION SCHEME (INTEGRATED METHOD)
Stepwise Separation
Step 1: Acidify Sample
Step 2: Basify Residue
Step 3: Separate Fractions
Acidic fraction
Neutral fraction
Basic fraction
INSTRUMENTAL ANALYSIS (COMMON FOR ALL)
TLC
HPLC
GC
GC–MS
LC–MS
UV–Vis
COMPARATIVE UNDERSTANDING
Property | Acidic Drugs | Basic Drugs | Neutral Drugs |
Ionization | Low pH | High pH | No ionization |
Extraction | Acidic medium | Acid → base extraction | Direct |
Examples | Barbiturates | Alkaloids | Solvents |
Solvent | Ether | Chloroform | Hexane |
FORENSIC SIGNIFICANCE
Enables:
Helps in:
Provides:
LIMITATIONS
Overlapping solubility
Matrix interference
Incomplete separation
CORE UNDERSTANDING
Acid–base properties govern:
Extraction
Separation
Detection
Forensic toxicology relies on:
Converting compounds into suitable forms
Isolating them efficiently
Identifying them using advanced techniques
Accurate analysis requires integration of:
chemistry
instrumentation
forensic interpretation
In forensic toxicology, “systematic extraction” means a stepwise, logical separation of poisons from complex biological matrices such as:
The goal is to:
isolate poisons without loss
separate different classes (acidic, basic, neutral, inorganic)
prepare them for accurate detection
NATURE OF BIOLOGICAL MATRIX
Biological samples are complex due to:
Hence, extraction requires:
protein removal
pH control
phase separation
SYSTEMATIC EXTRACTION OF ORGANIC POISONS
GENERAL PRINCIPLE
Based on:
STEPWISE EXTRACTION SCHEME
Sample Preparation
Tissue is:
Mixed with:
Purpose:
release bound poison
denature proteins
Acidification Stage
Effect:
Removal of Neutral and Fatty Impurities
Removes:
fats
pigments
neutral impurities
Extraction of Neutral Compounds
Neutral compounds move into organic phase
Basification Stage
Effect:
Extraction of Basic Drugs
Organic layer contains:
Extraction of Acidic Compounds
Concentration
Evaporate solvent
Obtain residue
FRACTIONATION RESULT
Neutral fraction
Basic fraction
Acidic fraction
SPECIAL METHODS FOR ORGANIC POISONS
Modified Stas–Otto Method
Ammonium Sulphate Method
Protein precipitation
Used for:
blood samples
protein-bound drugs
DETECTION OF ORGANIC POISONS
Preliminary Tests
Colour tests
Microcrystalline tests
Chromatographic Methods
TLC → screening
HPLC → quantitative
GC → volatile compounds
Confirmatory Methods
SYSTEMATIC EXTRACTION OF INORGANIC POISONS
GENERAL PRINCIPLE
METHODS
WET DIGESTION
Principle
Oxidation of organic matter using strong acids
Process
Applications
DRY ASHING
Principle
High-temperature combustion
Process
Heat sample in furnace
Organic matter burns
Ash dissolved in acid
Applications
SPECIAL EXTRACTION METHODS
Cyanide
Principle
Process
Add acid
Liberate HCN
Absorb in alkali
Heavy Metals
DETECTION OF INORGANIC POISONS
CLASSICAL TESTS
Arsenic
Lead
Mercury
INSTRUMENTAL METHODS
Atomic Absorption Spectroscopy (AAS)
ICP-MS / ICP-OES
Multi-element analysis
High sensitivity
Ion Chromatography
INTEGRATED EXTRACTION–DETECTION FLOW
Sample collection
Homogenization
Extraction:
Clean-up
Separation
Detection
Confirmation
FORENSIC SIGNIFICANCE
LIMITATIONS
Loss of volatile poisons
Decomposition
Matrix interference
Incomplete extraction
CORE UNDERSTANDING
Systematic extraction is a strategic chemical process, not just a technique. It ensures:
In forensic toxicology, identification establishes the nature of the substance, while quantitation determines its amount. Reliable conclusions are reached by combining:
Presumptive techniques → rapid screening
Separation techniques → isolate components
Confirmatory techniques → molecular-level identification
Quantitative techniques → concentration measurement
COLOUR TESTS
Principle
Chemical reagents react with functional groups of drugs to produce characteristic colours due to formation of:
conjugated systems
coordination complexes
oxidation products
Process
Small sample treated with specific reagent
Colour development observed
Compared with standard reference
Examples
Marquis → opioids, amphetamines
Dille–Koppanyi → barbiturates
Ferric chloride → phenols
Dragendorff’s → alkaloids
Identification
Quantitation
Limitations
THIN LAYER CHROMATOGRAPHY (TLC)
Principle
Separation based on:
adsorption
polarity differences
Process
Detection
UV light
Chemical spray reagents
Identification
Quantitation
Advantages
HIGH PERFORMANCE THIN LAYER CHROMATOGRAPHY (HPTLC)
Advancement
Automated application
Controlled development
Densitometric scanning
Identification
Quantitation
Peak area measurement
Calibration curve
Advantages
Higher sensitivity
Reproducible
HIGH PERFORMANCE LIQUID CHROMATOGRAPHY (HPLC)
Principle
Separation based on partitioning between mobile and stationary phases.
Process
Detection
Identification
Retention time
UV spectrum
Quantitation
Applications
Barbiturates
Benzodiazepines
Pesticides
GAS LIQUID CHROMATOGRAPHY (GLC / GC)
Principle
Separation of volatile compounds based on:
Process
Sample vaporized
Carried by inert gas
Separated in column
Detection
Identification
Quantitation
Applications
Alcohol
Solvents
Volatile drugs
UV–VISIBLE SPECTROPHOTOMETRY
Principle
Absorption of UV/visible light due to electronic transitions.
Quantitative Basis
A=εclA = \varepsilon c lA=εcl
εεε
ccc
lll
Process
Identification
Quantitation
Applications
FOURIER TRANSFORM INFRARED (FTIR)
Principle
Molecules absorb IR radiation → vibrational transitions.
Process
Sample exposed to IR
Spectrum recorded
Identification
Quantitation
Advantages
Highly specific
Non-destructive
MASS SPECTROMETRY
Principle
Molecules are:
Process
Ionization (EI, ESI)
Fragmentation
Detection
Identification
Quantitation
Applications
Confirmatory analysis
Trace-level detection
COMBINED TECHNIQUES
GC–MS
GC separates
MS identifies
LC–MS
COMPARATIVE UNDERSTANDING
Technique | Identification | Quantitation | Nature |
Colour test | Low specificity | Limited | Screening |
TLC | Moderate | Semi | Screening |
HPTLC | Good | Good | Advanced TLC |
HPLC | High | High | Non-volatile |
GLC | High | High | Volatile |
UV–Vis | Moderate | High | Spectroscopic |
FTIR | Very high | Limited | Structural |
MS | Very high | Very high | Confirmatory |
FORENSIC SIGNIFICANCE
LIMITATIONS
CORE UNDERSTANDING
Reliable forensic toxicology requires:
Each technique contributes uniquely:
Colour tests → rapid indication
Chromatography → separation
Spectroscopy → structure
Mass spectrometry → definitive proof
SAMPLE PREPARATION (CRITICAL STEP)
Purpose
Methods
Wet digestion → nitric/sulphuric acid
Microwave digestion → rapid and efficient
Dry ashing → high-temperature oxidation
Outcome
ATOMIC ABSORPTION SPECTROSCOPY (AAS)
Principle
Free atoms absorb light at characteristic wavelengths specific to each element.
Mechanism
Quantitative Basis
A=εclA = \varepsilon c lA=εcl
εεε
ccc
lll
Types
Flame AAS
Moderate sensitivity
Used for:
Graphite Furnace AAS
Qualitative Analysis
Quantitative Analysis
Applications
Arsenic
Lead
Mercury
Cadmium
Advantages
High specificity
Good sensitivity
Limitations
Single element analysis
Matrix interference
INDUCTIVELY COUPLED PLASMA (ICP)
Types
Principle
Sample introduced into plasma (~6000–10000 K):
ICP-OES
Mechanism
Qualitative Analysis
Quantitative Analysis
ICP-MS
Mechanism
Qualitative Analysis
Quantitative Analysis
Applications
Multi-element detection
Heavy metals in:
Advantages
Limitations
ION CHROMATOGRAPHY (IC)
Principle
Separation of ions based on:
Mechanism
Qualitative Analysis
Quantitative Analysis
Applications
Anions
Cyanide
Fluoride
Nitrate
Sulphate
Cations
Advantages
Limitations
COMPARATIVE UNDERSTANDING
Technique | Type | Best For | Detection |
AAS | Atomic absorption | Single metal | Absorbance |
ICP-OES | Emission | Multiple metals | Emission intensity |
ICP-MS | Mass spectrometry | Trace metals | m/z ratio |
Ion Chromatography | Separation | Anions/cations | Conductivity |
QUALITATIVE VS QUANTITATIVE ANALYSIS
Qualitative Analysis
Identifies:
Based on:
wavelength
retention time
spectral pattern
Quantitative Analysis
Determines:
Based on:
calibration curves
peak area or intensity
FORENSIC SIGNIFICANCE
LIMITATIONS
Matrix interference
Sample contamination
Instrumental cost
CORE UNDERSTANDING
Analysis of inorganic poisons requires:
AAS → single element detection
ICP → multi-element high sensitivity
Ion chromatography → ionic species
Reliable forensic interpretation depends on:
