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Analytical Chemistry. CHEM 2310 Prof. Monzir S. Abdel-Latif. Areas of Chemical Analysis and Questions They Answer. Quantitation: How much of substance X is in the sample? Detection: Does the sample contain substance X? Identification: What is the identity of the substance in the sample?
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Analytical Chemistry CHEM 2310 Prof. Monzir S. Abdel-Latif
Areas of Chemical Analysis and Questions They Answer Quantitation: How much of substance X is in the sample? Detection: Does the sample contain substance X? Identification: What is the identity of the substance in the sample? Separation: How can the species of interest be separated from the sample matrix for better quantitation and identification?
Chapter 1: Introduction This course is a quantitative course where you have seen some qualitative analysis in general Chemistry Lab and will also encounter the topic in other classes. In addition, Analytical Chemistry can be classified as Instrumental or Classical (wet Chemistry).
In this course, we will cover the classical methods of Chemical Analysis. However, it should not be implied that the term classical means something old, which is studied like history, but rather the term means understanding the basics of Chemical Analysis that were eventually laid down long time ago. Some of the classical methods still serve as the standard methods of analysis, till now.
The analytical process involves a sequence of logical events including: 1. Defining the problem This means that the analyst should know what information is required, the type and amount of sample, the sensitivity and accuracy of the results, the analytical method which can be used to achieve these results, etc...
2. Obtaining a representative sample It is very important to collect a representative sample for analysis. This could be appreciated if, for example, an ore is to be analyzed to decide whether the ore concentration in a mine or mountain can be economically produced. One should take several samples from different locations and depths, mix them well and then take a sample for analysis.
3. Preparing the sample for analysis Most analytical methods require a solution of the sample rather than the solid. Therefore, samples should be dissolved quantitatively and may be diluted to the concentration range of the method. 4. Chemical separations The sample may contain solutes which interfere with the determination of the analyte. If this is the case, analytes should be separated from the sample matrix by an accepted procedure.
5. Performing the measurement This implies conducting the analytical procedure and collecting the required data. 6. Calculations The final event in the analytical process is to perform the calculations and present the results in an acceptable manner.
RANGE The size of the sample can be used to describe the class of a method where a method can be described as meso if the sample size is above 100 mg or 100 microliters. A semimicro method describes a sample size from 10 to 100 mg or 50 to 100 microliters. When the sample size is in the 1 to 10 mg or less than 50 microliters, the method is said to be a micro method while a sample size less than 1 mg denotes an ultramicro method.
The sample size dictates what measurement techniques can be used.
An analyte in a sample can be classified as a major constituent if it constitutes more than 1% of the sample or a minor in the range from 0.1 to 1.0 %. It is classified as trace if it constitutes less than 0.1%. Analyze versus Determine These terms are sometimes misused. Always use the term ‘analyze’ with the sample while use the term ‘determine’ with specific analyte. Therefore, a sample is “analyzed”, while an analyte is “determined”.
