Introduction

Analytical chemistry is the branch of chemistry devoted to investigating the chemical composition of substances. It relies on instruments and methods that separate, identify and quantify the matter in a sample, and the outcome of that work is chemical or physical information about the sample under study. Analysis divides into two broad kinds. Qualitative analysis answers the question 'what is present?' — it detects the presence or absence of particular elements in a compound or in a mixture of compounds, without saying how much of each is there. Quantitative analysis answers the question 'how much is present?' — it determines the relative proportions of the elements that make up a compound or a mixture of compounds. The two kinds of analysis are complementary: a chemist typically establishes what a sample contains (qualitative analysis) before measuring how much of each constituent it contains (quantitative analysis), and both together give a complete picture of a sample's chemical make-up.