CHEMISTRY ANALYTICAL CHEMISTRY Fall Lecture 1

What is Analytical Chemistry? –“ Science of Chemical Measurements ” It provides the methods and tools needed for insight into our material world … for answering four basic questions about a material sample? What? ( What is the identity of the substance in the sample? ) Where? ( Does the sample contain substance X? ) How much? ( How much of substance X is in the sample? ) What arrangement, structure or form?

Analytical chemistry further classification Bioanalytical chemistry Material analysis Chemical analysis Environmental analysis Forensics Techniques Spectroscopy Mass Spectrometry Spectrophotometry Chromatography and Electrophoresis Crystallography Microscopy Electrochemistry

Areas of Chemical Analysis Chemical analysis includes any aspect of the chemical characterization of a sample material, such as separation: –How can the species of interest be separated from the sample matrix for better quantitation and identification? Qualitative analysis is what. Quantitative analysis is how much. Qualitative analysis is what. Quantitative analysis is how much.

What Do Chemical Analysts Do? Analyst: Applies known measurement techniques to well defined compositional or characterization questions. Research Analytical Chemist Creates and /or investigates novel techniques or principles for chemical measurements. –or Conducts fundamental studies of chemical/physical phenomena underlying chemical measurements. –or Develops new measurement methods on existing principles to solve new analysis problems.

0-1 The analytical Chemist’s job Sampling Sample preparation The chemical analysis Calibration curves Interpreting the results

Sampling: Procuring a representative sample

Procuring a representative sample

Project 1: How to measure the caffeine content of a chocolate bar?

Theobromine Biochemical precursor of Caffeine Caffeine A central nervous system stimulant

1.Weighting 2.Removing fat with organic solvent Step 1: Sample Preparation --transforming a sample into a state that is suitable for analysis

3. Extracting caffeine and theobromine (analytes) with water

Step 2: Performing analysis with liquid chromatography

Principles of liquid chromatography

Step 3: Preparing calibration curves A graph of detector response as a function of analyte concentration is called a calibration curve or a standard curve. Standard solution: containing known concentrations of analytes.

Step 4: Analyzing the results

0-2 General steps in a chemical analysis An analysis involves several steps and operations which depend on: the particular problem your expertise the apparatus or equipment available. The analyst should be involved in every step. An analysis involves several steps and operations which depend on: the particular problem your expertise the apparatus or equipment available. The analyst should be involved in every step.

Exercise 1: The steps in a chemical analysis are (a) 1. Formulate the question. 2. Select the analytical procedure. 3. Sample. 4. Prepare the sample. 5. Make replicate measurements of the sample. (b) 1. Select the analytical procedure 2. Sample. 3. Prepare the sample. 4. Make replicate measurements of the sample. 5. Make a clear and complete written report of your findings. (c) 1. Formulate the question. 2. Select the analytical procedure. 3. Sample. 4. Prepare the sample. 5. Make replicate measurements of the sample. 6. Make a clear and complete written report of your findings.

Exercise 2: When performing an analysis a chemist often uses a standard solution. What is a standard solution? (a) A solution that complies with standards established by the Environmental Protection Agency. (b) A solution that has a concentration of a chemical that is known to a high degree of certainty. (c) A solution that is prepared from a chemical that has been designated as a primary standard. Exercise 3: In a random heterogeneous material, (a) differences in composition occur randomly and on a fine scale. (b) large regions have obviously different compositions. (c) samples are collected by taking portions from the desired number of segments chosen at random.