Dr Saleha Shamsudin

1.INTRODUCTION Topics to be covered: 1.1 INTRODUCTION TO METHODS IN ANALYTICAL CHEMISTRY 1.2 STEPS IN QUANTITATIVE ANALYSIS

1.INTRODUCTION Analytical chemistry deals with chemical characterization of matter on 2 questions: What is it?(qualitative) How much is it?(quantitative) Qualitative analysis-reveals the identity of the elements and compound in a sample Quantitative analysis-indicates the amount of each substance in a sample

1.1 INTRODUCTION TO METHODS IN ANALYTICAL CHEMISTRY Q1: How do you carry out tests for qualitative analysis? A: By performing selective chemical reactions or use instrumentation.

For example (by chemical reaction), AgNO 3 added to a dissolved sample, producing a white precipitate. This indicates the presence of chloride ions qualitatively. NaCl + AgNO 3 --> NaNO 3 + AgCl (white solid) Why? Because Ag + and Cl - reacts to form AgCl that produces the white precipitate

Q2: How do you carry out tests for quantitative analysis? A2: Nowadays, we use instrumentation. Because, the results are more accurate. For example, testing of banned substances at the Olympic Games. There are 3 phases in the analysis.

Phase 1: Fast screening phase Phase 2: Identification phase Phase 3: Possible quantification

Fast screening phase: Urine samples are tested rapidly for the presence of classes of compounds different from normal samples. Techniques use: gas chromatography (GC), liquid chromatography (LC). If samples have unknown compounds, that may or may not be prohibited, therefore further testing is needed for identification purpose.

Identification phase: Using techniques such as gas chromatography-mass spectrometry (GC-MS).

Q3: What happens during this procedure of using Gas Chromatography- Mass Spectrometry (GC-MS)? A3: Complex mixtures are separated by GC. Then, detetected by MS that gives molecular structural data on the compound.

Possible Quantification: Q4: Why need this step? A4: Some compounds must be quantified precisely. Meaning that, exact amount of compound must be determined. Therefore, we can verify whether the substance is present at low level or high level.

Thank you. Next class: Steps in analysis process & basic tools