Analytical Chemistry Concepts

Study Notes

Analytical chemistry is the characterization of matter.
Analytical chemistry answers two questions: what is in the system (composition) and what are the characteristics of the system (nature).
There are two types of information:
- Qualitative
- Quantitative

Quantitative information is used to determine the amount of a particular component in a sample.
Two types of quantitative methods:
- Absolute methods
- Relative methods

Absolute methods are based on reaction stoichiometry.
They involve measuring the mass or volume of a substance that reacts with the analyte of interest.
Absolute methods can be classified as:
- Gravimetric: Based on mass data
- Volumetric: Based on volume data
Both gravimetric and volumetric methods are considered classical methods.

Relative methods are based on comparing a property of the analyte to a standard. They are considered instrumental methods.
Relative methods include:
- Optical methods
- Electrochemical methods
- Chromatographic methods
There are also miscellaneous methods:
- Mass spectrometry: Measures the mass-to-charge ratio
- Nuclear Magnetic Resonance (NMR) spectrometry: Measures the resonance frequency and the chemical shift
- Neutron Activation and isotope dilution methods: Utilize radioactivity
- Kinetic methods: Measured by the rate of reaction
- Thermal Conductivity and enthalpy methods: Measure thermal properties

Instrumental methods give advantages:
- They can be used to measure very low analyte concentrations.
- They can be used to analyze very small samples.
- They can be used to analyze multiple analytes simultaneously.
- They are rapid methods with short measurement times, enabling high analysis throughput.
- They require less personnel.
- They are computer compatible, allowing automatic data acquisition, large data storage, and automatic process control.
Instrumental methods also have limitations:
- They may have low measurement precision.
- They may have a large initial financial outlay.