Overview of Analytical Chemistry

Overview

• Analytical chemistry is a measurement science
• It consists of a set of powerful ideas and methods
• It is used in all fields of science and medicine

Example:

Analytical chemistry is used during NASA’s rover exploration in Mars on July 4, 1997 where the Sojourner returned rock and soil compositions where it was known that Mars was at one point warn and wet on the surface and atmosphere

In January 2004 Spirit and Opportunity arrive on Mars for a 3 month mission where Spirits X-ray and Mossbauer spectrometer found concentrated deposit of silica and carbonate. The Spirit continued to explore until 2010 while Opportunity continued until March 2012 and covered more than 21 miles with images of craters, small hills, and other features.

Curiosity arrived on August 6, 2012 with CHEMCAM LIBS + remote micro imager where it can determine elements with no sample preparation. It can also determine major, minor, trace elements and hydrated minerals. It also contains mass and laser spectrometer, gas chromatograph. It’s goal was to survey carbon, organic compounds, chemical and isotopic states, noble gas and light isotopes, and composition of Martian atmosphere.

Qualitative Analysis

reveals chemical identity of elements and compounds in a sample

Quantitative Analysis

determines the relative amounts of each substance in a sample

Analytes

components of a sample that are to be determined

Quantitative Analytical Methods

Gravimetric methods - determine the mass of analyte

Volumetric methods - use volume of solution containing sufficient reagent to reach with the analyte

Electroanalytical methods - measure electrical properties (potential, current, resistance)

Spectroscopic methods - based on the interaction of electromagnetic radiation with analyte atoms & molecules

Process of a Typical Quantitative Analysis

1. Choosing a Method: level of accuracy: investment time/money, number of samples and components in the samples
2. Acquiring the Sample: the same consistency of sample in bulk must be taken to avoid sampling errors
3. Processing the Sample: preparing laboratory sample, defining replicate samples, preparing solutions
4. Eliminating Interferences: reducing errors in the analysis as close to 0 as possible; matrix or sample matrix: collections of all components in the sample containing an analyte
5. Calibrating and Measuring Concentration: measurements of property is directly proportional (kX)
6. Calculating Results
7. Evaluating Results

Feedback Control System

it is a cycle of continuous measurement, comparison, and control; often called as feedback loop