Lecture 1.pdf

Analytical chemistry (Volumetric, Electrochemical analysis - Chromatographic Separation Techniques) Code: Chm 113 Dr. Wael Mortada  Lecture Introduction and Statistical Analysis Dr. Wael Mortada Assistant Professor of Analytical Chem...

Analytical chemistry (Volumetric, Electrochemical analysis - Chromatographic Separation Techniques) Code: Chm 113 Dr. Wael Mortada  Lecture Introduction and Statistical Analysis Dr. Wael Mortada Assistant Professor of Analytical Chemistry Contact details: Email: [email protected] Mobile: 01022772144 Dr. Wael Mortada  Definition of analytical chemistry. Some applications of qualitative chemical analysis. Classification of quantitative chemical analysis. Intended Measurements and Error Analysis: Learning accuracy vs precision. Outcomes (ILOs) Comparison between analytical methods: Student t test and F test. Confidence intervals and confidence limits. Types and sources of errors. Dr. Wael Mortada  What is the analytical chemistry: It is the branch of chemistry that deals with the composition and structure of the matter. In other words, it is the science of determining what matter is and how much of it exists. Some major applications of analytical chemistry are: Assuring the safety and quality of food, pharmaceuticals, and water. Assuring safety of the environmental. Help in diagnosis of some diseases by analysis of biological samples. In forensic medicine. Providing analysis required to trade and commerce Dr. Wael Mortada  Analytical methods Classical Instrumental methods methods Qualitative Quantitative methods methods Dr. Wael Mortada Applications of qualitative analysis: Iodine test: The test is used to detect the presence of starch. The starch, a plant carbohydrate, composed of two different polysaccharides of glucose. One is a linear polysaccharide termed as amylose and the other is the branched amylopectin (Fig 1.1. A). Aa aqueous solution of iodine (I2) and potassium iodide (KI) has a light orange-brown color. If it is added to a sample that contains starch, the color changes to a deep blue. Iodine-iodide mixture (I3-) interact with helical amylose forming a dark-blue complex as in Fig 1.1. (B). Dr. Wael Mortada  Applications of qualitative analysis: Flame test: - The test is used to identify some metal ions. The heating excites the electrons of the metal ions, causing them to emit characteristic visible light (emission spectra). Limitations of the Flame Test: 1) The test cannot detect low concentrations of most ions. 2) The brightness of the signal varies from one sample to another. 3) Impurities or contaminants affect the test results. 4) The test cannot differentiate between all elements. Several metal ions produce the same flame color. Some compounds do not change the color of the flame. Dr. Wael Mortada Quantitative Chemical Analysis It is a branch of analytical chemistry that deals with the determination of the concentration of one or more constituents of a sample. Depending on the property that is used in the determination, quantitative chemical analysis is classified into: Physical methods: They involve the measurement of a physical property that is related to the concentration of the analyte such as density, refractive index, absorption of light, magnetic susceptibility, …… etc. Chemical methods: They depend on a chemical reaction between the analyte and a reagent The reaction may be neutralization, precipitation, complexometric, oxidation-reduction. Generally, the reaction involves the formation of a new compound. The main classes of analytical chemical methods are: 1. Volumetric, or titrimetric, analysis. 2. Gravimetric analysis Dr. Wael Mortada Measurements and Error Analysis Many numerical calculations are 100% true. For example, two plus two equal 4, not 4.1. However, most measurements have some degree of errors (uncertainty) that may arise from different sources. The process of uncertainty analysis or error analysis is very important to ensure the accuracy and precision of the analytical method. Note: It is difficult to exactly know the true value in analytical chemistry. Therefore, we can replace the term “true value” by “accepted or reference value”. Dr. Wael Mortada Measurements and Error Analysis Many numerical calculations are 100% true. For example, two plus two equal 4, not 4.1. However, most measurements have some degree of errors (uncertainty) that may arise from different sources. The process of uncertainty analysis or error analysis is very important to ensure the accuracy and precision of the analytical method. Accuracy is the closeness between the measured value and the true “accepted” value. Precision is the closeness between independent measurements (without reference to a true value) of the same quantity. It is also called reproducibility or repeatability. Dr. Wael Mortada Dr. Wael Mortada The accuracy can be determined by one of the following scenarios: 1. Analysis of a standard reference material (SRM): a material that was analyzed by one or more technically valid procedure. There are many international institutions specialized in this matter. The most famous are The National Institute of Standards and Technology (NIST), National Metrology Institute of Japan (NMIJ), European Reference Materials (ERM). 1. Comparison with a standard analytical method: Dr. Wael Mortada How to express accuracy and precision? Accuracy is usually estimated quantitatively by calculating absolute error or relative error. Precision is usually tested quantitatively by calculating relative standard deviation (RSD). Dr. Wael Mortada Dr. Wael Mortada Dr. Wael Mortada Dr. Wael Mortada Dr. Wael Mortada Dr. Wael Mortada Dr. Wael Mortada Dr. Wael Mortada Dr. Wael Mortada Dr. Wael Mortada  Summary and wrap up - Two types of analytical chemistry (quantitative and qualitative). - Accuracy is a measure of trueness while precision determines the repeatability. - Systemic error is a constant error while random error is fluctuated. Dr. Wael Mortada Evaluation Dr. Wael Mortada Dr. Wael Mortada