GENERAL DESCRIPTION OF INSTRUMENTAL (PHYSICAL AND PHYSICAL-CHEMICAL)
METHODS OF ANALYSIS
Physical and physical-chemical methods of analysis are based on the dependence of measured physical properties of substances on their qualitative and quantitative composition. Since the physical properties of substances are measured using various equipment (''instruments''), these methods of analysis are also called instrumental methods.
Classification of physical and physical-chemical methods of analysis. This classification is based on recording the measured physical and physical-chemical properties of the substance or investigated system.
Optical methods are based on measuring the optical properties of substances.
Chromatographic methods are based on the ability of various substances for selective sorption.
Electrochemical methods are based on measuring the electrochemical properties of systems.
Radiometric methods are based on measuring the radioactive properties of substances.
Thermal methods are based on measuring the heating effects of corresponding processes.
Mass spectrometric methods are based on the analysis of ionized fragments of substances.
Other methods of analysis (ultrasonic, magnetochemical, pycnometric, etc.) are also used.
General advantages and disadvantages of physical and physical-chemical methods of analysis. The advantages of physical and physical-chemical methods of analysis include the following.
a) Low limit of detection (1-10-9 mcg) and low limit concentration (up to ~10-12 g/ml) of determined substance.
b) High sensitivity, formally determined by the tangent of angle slope of the corresponding calibration curve, which actually reflects the dependence of the measured physical parameter (usually plotted on the Y-axis) on concentration or amount of determined substance (usually plotted on the X-axis). The greater tangent of angle slope of the curve to the X-axis, the more sensitive the method, i.e., in order to obtain the same «response» (a change in the physical parameter), the lesser change in concentration or amount of the determined substance is required.