Key Concepts in Analytical Chemistry

Analytical Chemistry

The science of obtaining, separating, identifying, and quantifying matter. It involves improving established methods, extending methods to new samples, and developing new methods for measuring chemical phenomena.

Sample

The substance or material to be analyzed.

Analyte

The component of the sample that is to be determined or detected.

Matrix

The remainder of the sample is other than the analyte.

Characterization Analysis

Evaluates a sample's chemical or physical properties. It can be qualitative (identifying species) or quantitative (determining amounts of species).

Qualitative Analysis

Establishes the chemical identity of species in the sample (detection/identification).

Quantitative Analysis

Determines the relative amounts of different species in numerical terms (determination).

Fundamental Analysis

Directed toward improving the capabilities of analytical methods, such as extending theory, studying limitations, and designing new methods.

Clinical Chemistry

Application of analytical chemistry in medicine, such as determining concentrations of substances in urine or blood to diagnose and treat illnesses.

Material Science

Application of analytical chemistry in analyzing materials like steel, germanium, and silicon to control properties such as strength, hardness, and impurity levels.

Food Science

Application of analytical chemistry in determining the nutritional value of foods and controlling harmful preservatives and additives.

Environmental Chemistry

Application of analytical chemistry in monitoring pollutants in the environment, such as hydrocarbons in automobile exhaust or heavy metals in rivers.

Technique

A chemical or physical principle used to analyze a sample (e.g., atomic absorption spectroscopy).

Method

The application of a technique for determining a specific analyte in a specific matrix.

Procedure

A set of written directions detailing how to apply a method to a particular sample, including sampling, handling interferents, and validating results.

Protocol

A set of stringent written guidelines detailing the procedure that must be followed for an agency to accept the results of the analysis.

Classical Methods

Also known as wet methods or batch analysis, involving the measurement of weight or volume. Calculations are often derived from the stoichiometry of a chemical reaction.

Gravimetry

A classical method that determines the mass of the analyte or a related compound. It involves precipitation, filtration, drying, and weighing the precipitate.

Titrimetry

Also known as volumetric analysis, it measures the volume of a solution containing sufficient reagent to react completely with the analyte. A burette is commonly used.

Instrumental Methods

Methods that use instrumentation to measure physical properties of an analyte, such as current, potential, or absorption/emission of light.

Spectroscopic Methods

Based on measurements of the interaction between electromagnetic radiation and analyte atoms or molecules, or the production of such radiation by analytes.

Spectroscopy

The study of the interaction of radiation and matter.

Spectrophotometry

The measurement of the emission or absorption of radiation from matter.

Spectrophotometer

An instrument used to measure the emission or absorption of radiation from matter.

Spectrum

The output of a spectrophotometer, showing the interaction of radiation with matter.

UV-Visible Spectrophotometry

Uses radiation in the UV and visible regions to cause electronic excitation in molecules.

UV-Visible Spectrophotometry

Uses radiation in the UV and visible regions to cause electronic excitation in molecules. Often used for analyzing colored or conjugated analytes.

Infrared Spectrophotometry

Uses infrared radiation to cause vibrational excitation in molecules. Used for analyzing molecular structure and functional groups.

NMR Spectrophotometry

Uses radio waves to align the nuclei of atoms in molecules. Applied in determining molecular structure.

Electroanalytical Methods

Involve the measurement of properties such as potential difference, current, resistance, and conductivity. Electrodes are commonly used.

Potentiometry

Measures the difference in electrode potentials.

Amperometry

Measures the electric current.

Coulometry

Records the charge passed during a certain time.

Voltammetry

Measures the current while actively altering the potential.

Chromatographic Methods

Involves the separation of components of a mixture based on differences in the rates at which they are carried through a stationary phase by a gaseous or liquid mobile phase.

High-Performance Liquid Chromatography (HPLC)

Uses a liquid mobile phase, and the sample must be soluble in a selected solvent.

Gas Chromatography (GC)

Uses a gaseous mobile phase, and the sample must be gaseous, volatile, or convertible into a volatile derivative.

Detector

A device used in chromatography to quantify the separated analytes, often coupled with spectroscopic or electroanalytical methods.

Volumetric titration

Titrant's volume is being measured.

Gravimetric titration

Mass is being measured for titration.

Titration

Progressive addition of a standard solution to a solution with which it reacts.

Internal indicator

Added to a system.

External indicator

Indicator is allowed to react in a separate container with a few drops of the solution being titrated.

Standardization

The process of determining the concentration of a standard solution.

Direct Standardization

Dissolving a weighed amount of pure dry chemical and diluting the solution to an exactly measured volume.

Primary standard

A pure dry solid substance of known chemical composition and purity.

Direct titration

The standard solution is titrated directly with the sample in question.

Indirect titration

An excess reagent is added to the sample in question and the excess reagent is titrated with another standard solution.

Neutralization methods

Uses the reaction between an acid and a base.

Akalimetry

An acid is titrated with a standard solution of a base.

Acidimetry

A base is titrated with a standard solution of an acid.

Redox methods

Utilizes redox reaction between an oxidizing agent and a reducing agent. The titrant is often oxidizing agents.

Permangonometry

Uses standard solution of potassium permanganate (KMnO4) as titrant. The titrant is its own indicator.

Dichrometry

Uses standard solution of potassium permanganate (KMnO4) as titrant.

Cerimetry

Uses standard solution of ceric sulfate (Ce(SO4)2) as titrant.

Iodimetry

Uses standard iodine solution (I2) to titrate reducing agent.

Iodometry

A solution of iodide ions is added to a solution containing an oxidizing agent and the iodine produced is titrated with a standard sodium thiosulfate solution (Na2S2O3).

Precipitimetry

Utilizes precipitation reactions and differences in Ksp.

Complexometric method

Utilizes EDTA as titrant, used for metal analysis.