Instrumental Chemistry Chapter 1 Introduction

Classical Methods Early years of chemistry  Separation of analytes by precipitation, extraction, or distillation. Qualitative analysis by reaction of analytes with reagents that yielded products that could be recognized by their colors, boiling or melting points, solubilities, optical activities, or refractive indexes. Quantitative analysis by gravimetric or by titrimetric techniques.

Instrumental Methods Measurement of physical properties of analytes - such as conductivity, electrode potential, light absorption or emission, mass-to-charge ratio, and fluorescence-began to be employed for quantitative analysis of inorganic, organic, and biochemical analytes. Efficient chromatographic separation techniques are used for the separation of components of complex mixtures. Instrumental Methods of analysis (collective name for newer methods for separation and determination of chemical species.)

Bias Bias provides a measure of the systematic, or determinate, error of an analytical method. bias = g – xt Where: g is the population mean for the concentration of analyte in a sample that has a true concentration of xt

Sensitivity Ability to discriminate between small differences is analyte concentration. calibration sensitivity, S = MC + Sbi S = measured signal c = concentration of analyte Sbi = instrument signal for a blan M = slope of the straight line

Applicable Concentration Range The figure below illustrates the definition of the useful range of an analytical method, which is from the lowest concentration at which the quantitative measurements can be made (limit of quantitation LOQ) to the concentration at which the calibration curve departs from linearit (limit of linearity LOL)

Applicable Concentration Range

American Chemical Society: Chemical Abstracts Service: Chemical Center Home Page: (maintained by ACS) Science Magazine: Useful Websites Dealing With Instrumental Analysis