Lesson 1: Nature of Analytical Chemistry

Analytical Chemistry

• Science of Chemical Methods and Experiments (characterization)

• Methods, instruments, and strategies to obtain information

• Metrological discipline

Purity of Golden crown

Archimedes checked this based on a story

Robert Boyle

• Coined the term analyst

• First modern chemist

Antoine Lavosier

Father of analytical chemistry

Izaak Maurits Kolthoff

Father of modern analytical chemistry

Carl Remiguis Fresenius

German analytical chemist. Found the first journal in analytical chemistry.

Wilhelm Ostwald

First to acknowledge the foundation of analytical chemistry.

Analyte

Constituent of interest in a sample. One that is being sought out in an analysis and it is unknown.

Matrix

Comprises all other constituents in a sample except the analyte.

Classification of Analyte

• Major constituent

• Minor constituent

• Trace constituent

• Ultra-trace constituent

4 types of classification of analyte

• Based on the method

• Based on extent of analysis

• Based a sample size

• Based on purpose of determination

Major constituent

Constituent is 1-100%

Minor Constituent

Constituent is 0.01-1%

Trace Constituent

Constituent is 0.001-0.01% (1ppb to 1ppm)

Ultra-trace Constituent

Constituent is < 0.001% (< 1ppb)

Physical - Based on method

Observable and uses senses (organoleptic). Comparison of the unknown against a standard.

Chemical - Based on method

Usage and observation of chemical reaction. Has two types, volumetry and gravimetry.

Volumetry - chemical

Quantitative method based in measuring the volume.

Gravimetry - chemical

Quantitative method based on determining the mass of a compound.

Instrumental - Based on method

Usage of instruments.

Spectroscopy - instrumental

Based on the interaction of electromagnetic radiation with matter

Chromatography - instrumental

Components of a mixture is separated.

COA Based on Method

• Physical

• Chemical

• Instrumental

COA Based on the extent of analysis

• Complete/exact

• Partial/proximate

• Ultimate

Complete/exact - Based on extent of analysis

Amount of each constituent is determined

Partial/Proximate - Based on extent of analysis

Selected amount is determined.

Ultimate - Based on extent of analysis

Amount of all element present is determined.

COA Based on Sample Size

• Macro analysis

• Semi-micro analysis

• Microanalysis

• Ultra-micro analysis

Macro analysis - Based on sample size

Mass is >100mg

Volume is >100 microliter

Semi-micro analysis - Based on sample size

Mass is 10-100mg

Volume is 50-100 microliters

Micro analysis - Based on sample size

Mass is 1-10mg

Volume is <50 microliters

Ultra-micro analysis - Based on sample size

Mass is <1 mg

Volume is xxx

COA Based on Purpose of Determination

• Characterization

• Qualitative

• Quantitative

• Fundamental

Characterization - based on purpose of determination

Structure

Qualitative - based on purpose of determination

Presence is checked

Quantitative - based on purpose of determination

Amount is checked

Fundamental - based on purpose of determination

Procedure or method is checked or included

Typical steps in analysis

1. Selecting a method

2. Sampling

3. Sample preparation

4. Analysis

5. Interpretation

Selecting a method

• Technique

• Method

• Procedure

• Protocol

Technique - selecting a method

Chemical or physical principle to analyze a sample.

Method - selecting a method

Means for analyzing a sample for a specific analyte

Procedure - selecting a method

Set of written directions

Protocol - selecting a method

Set of written guidelines

Sampling

A process of obtaining a portion of a material.

• gross

• Laboratory

• Aliquot

Gross sample - sampling

Consists of several portions of the material

Laboratory sample - sampling

Small portion of the material

Aliquot - sampling

Measured portion of the volume.

Sampling plan

• Random

• Selective

• Convenience

• Systematic

• Stratified

• Systematic-judgemental

Random - sampling plan

Any portion of material has an equal and known chance of being choosen,

Selective - sampling plan

Sample is deliberately chosen.

Convenience - sampling plan

Selected using a criteria.

Systematic - sampling plan

Taken according to previously arranged regular intervals.

Stratified - sampling plan

Lot is subdivided.

Systematic-judgemental - sampling plan

Based on prior knowledge.

Representative

Is known as the parent material.

Types of sample

• Heterogeneous

• Homogeneous

• Static system

• Dynamic system

• Grab

• Composite

• In situ

Heterogeneous - type of sample

More than one phase

Homogenous - type of sample

One phase

Static system - type of sample

Just there and not moving

Dynamic - type of sample

Changing with respect to time

Grab - type of sample

Collected at a specific time or location.

Composite - type of sample

Combination of more than one portion

In situ - type of sample

Usage of instrument on the sampling site.

Sample preparation

Process of converting the sample into a form suitable for analysis. Usually involves removing of fragments.

Analysis

Provides chemical or physical description. Has two types

• Determination

• Measurement

Determination - analysis

Analysis of sample to find the identity, concentration, or properties of the analyte.

Measurement - analysis

Experimental determination of an analyte’s chemical or physical properties.

Analytical approaches

1. Identify and define problem

2. Design experimental procedure

3. Conduct experiment and gather data

4. Analyze experimental data

5. Propose solution to problem

Interpretation

Last step in steps in analysis