Instrumental Analysis CHEM - 4400
Intro to Instrumental AnalysisChapter 1 • Classification of Analytical Methods • Qualitative instrumental analysis is that measured property indicates presence of analyte in matrix. • Quantitative instrumental analysis is the magnitude of measured property is proportional to concentration of analyte in matrix.
Another Classification • Classical Methods • Titrations • Gravimetric analysis • Instrumental Methods • Based on measurements of properties of analyte • Phenomena known for years • Recent growth due to electronics and computers
Characteristic PropertyInstrumental Method • Emission of radiation fluorescence, phosphorescence, X-ray • Adsorption of radiation NMR, EPR, UV-vis, IR • Scattering of radiation Raman, turbidimetry • Refraction of radiation Refractometry • Diffraction of radiation X-ray (XRPD) • Rotation of radiation Polarimetry, optical rotary dispersion • Electrical potential Potentiometry • Electrical charge Coulometry • Electrical current Amperometry, polarography • Electrical resistance Conductometry • Rate of reaction Kinetic methods • Mass-to-charge ratio Mass spectrometry
Precision – A measure of the reproducibility of a measurement. Accuracy – A measure of how close a measured value is to the “true value” Sensitivity – Ability to discriminate between small differences in analyte concentration Calibration sensitivity – Slope of calibration curve at concentration of interest Analytical sensitivity () – m/ss (slope/STDEV of measurement)
Detection Limit – minimum concentration of analyte that can be detected at a know confidence level. Signal Detection Limit – minimum signal that can be distinguished from the blank.