Overview of Analytical Chemistry

Analytical Chemistry Overview

• Analytical chemistry is the science of obtaining, processing, and communicating information about the composition and structure of matter.
• It involves determining what substances are present and how much of each exists.

Branches of Chemistry

• Chemistry has several branches, including inorganic, organic, physical, and analytical chemistry.
• Analytical chemistry is connected to these other branches.

Analytical Chemistry Subdivisions

• Qualitative analysis identifies the components of a sample.
• Quantitative analysis determines the amount of each component.
• Analytical methods often offer both types of information (e.g., GC/MS).

Analytical Chemistry Steps

• 1. Sampling: The sample must be representative and homogeneous, and transported to the lab without alteration.
• 2. Method Selection: The analyst considers factors like accuracy, precision, sensitivity, selectivity, speed, cost, and legality when choosing the analytical method.
• 3. Separation: The method removes interferences and increases selectivity towards the analyte.
• 4. Quantitation: The method determines the amount of the analyte.
• 5. Evaluation: Statistical analysis of the results is crucial to determine precision and accuracy.

Classification of Analytical Chemistry

• Quantitative analysis includes modern methods (instrumental methods, nanotechnology, chromatography, electro analysis, optical methods) and classical methods (volumetric methods, gravimetric methods).
• Qualitative analysis methods include apparatuses, chemical reactions, and senses.

Chemical Methods

• Chemical methods depend on making a chemical reaction. That reaction must fulfill certain conditions, like spontaneity, irreversibility, and the lack of side reactions.
• The reaction must have a clear equivalence point.
• Indicators are used to measure this equivalence point.

Solutions

• Solutions are homogeneous mixtures.
• The major component is called the solvent.
• The minor component(s) is/are called the solute.
• When a gas or solid dissolves in a liquid, the gas or solid is the solute and the liquid is the solvent.

Analytical Methods

• Gravimetry: based on weight.
• Titrimetry: based on volume.
• Electrochemical: measures potential, current, charge.
• Spectral: uses electromagnetic radiation.
• Chromatography: separates materials.
• Chemometrics: statistically treats data.

Types of Analytical Methods for Samples

• Gravimetric method: measures the mass of pure substance containing the analyte to determine its amount.
• Volumetric method: measures the volume to determine the analyte's amount.
• Instrumental method: measures physical properties to determine the constituents of a sample.

Basic Tools and Operations in Analytical Chemistry

• 1. Laboratory Notebook: Use it to record data in an orderly way to save time and reduce the chance of mistakes. An immediate record helps detect errors.
• 2. Laboratory Materials and Reagents: Primary standard chemicals are highly pure, expensive, and used for preparing and standardizing solutions. Special grades of solvents exist for specific applications like spectroscopy, and liquid chromatography/mass spectrometry (LC/MS) to remove impurities.
• 3. Analytical Balance: Modern electronic balances are used due to their convenience and reduced errors compared to mechanical balances.
• 4. Volumetric Glassware: Volumetric flasks are for diluting solutions to specific volumes. Pipets deliver specific volumes of solutions (aliquots).
• 5. Handling and Treating Samples: Syringes/needles are used for collecting blood samples (in vials with anticoagulants). Finger punctures may be used for smaller blood quantities. Desiccators keep samples dry for weighing.
• 6. Ovens: Muffle furnaces ignite samples to high temperatures (converting precipitates, burning organic materials). Drying ovens dry samples before weighing generally at ~110°C. Fume hoods are used for evaporating chemicals like perchloric acid.
• 7. Wash Bottles: Used for washing precipitates and solutions.
• 8. Centrifuges and Filters: Used for separating mixtures (like blood serum and plasma or precipitates). Filters are various types.

General Steps of Chemical Analysis

• Formulate the question.
• Select techniques.
• Sample.
• Prepare the sample.
• Analyze the sample. (measure the concentration of components in identical portions of the sample)
• Present and interpret data.
• Draw conclusions

Units and Measurements

• Fundamental SI Units: These include kilogram (kg), meter (m), second (s), Kelvin (K), mole (mol), ampere (A), and candela (cd).
• Derived SI Units: Units like Newton (N), Pascal (Pa), Joule (J), Watt (W), and Hertz (Hz) are derived from fundamental units.

The Mole

• A mole is a unit of amount of substance.
• A mole of a substance contains Avogadro's number of atoms, molecules, ions, or other entities.
• In relation to mass: number of moles = (mass in grams) / (molar mass)

Molarity (M)

• Molarity is the number of moles of solute per liter of solution.
• Moles = Molarity x Liters
• Millimoles = Molarity x Milliliters.

Normality (N)

• Normality is the number of equivalents of solute per liter of solution.
• The normality is related to the reacting units per molecule of solute.
• Equivalents = moles x reacting units/molecule.
• Equivalent mass = formula mass / # reacting units.

Formality(F)

• Formality is the number of formula weights of solute per liter of solution.
• Formality may be numerically the same as molarity for some substances.
• Formality is used for the total analytical concentration of a substance.
• Molarity is used in equilibrium calculations.

Molality (m)

• Molality is the number of moles of solute per kilogram of solvent.
• Molality = moles / kg solvent