Chem 2_Lesson 1.1-1.1b.pdf

Chem 2 ANALYTICAL CHEMISTRY (Lecture) Instructor: Michael John G. Bation  MODULE 1: INTRODUCTION TO ANALYTICAL CHEMISTRY LESSON 1.1a: The Nature of Analytical Chemistry Instructor: Michael John G. Bation Introduction to Chemical Analysis Chemical analysis includes any aspect of the...

Chem 2 ANALYTICAL CHEMISTRY (Lecture) Instructor: Michael John G. Bation  MODULE 1: INTRODUCTION TO ANALYTICAL CHEMISTRY LESSON 1.1a: The Nature of Analytical Chemistry Instructor: Michael John G. Bation Introduction to Chemical Analysis Chemical analysis includes any aspect of the chemical characterization of a sample material. Analytical Chemistry? “Science of Chemical Measurements” Analytical Chemistry provides the methods and tools needed for insight into our material world. What? Where? How much? What arrangement, structure or form? The Nature of Analytical Chemistry Analytical Chemistry deals with methods for determining the chemical composition of samples. Qualitative Analysis (identification) provides information about the identity of species or functional groups in the sample (an analyte can be identified). Quantitative Analysis provides numerical information of analyte (quantitate the exact amount or concentration). The Nature of Analytical Chemistry Qualitative Analysis (identification) provides information about the identity of species or functional groups in the sample (an analyte can be identified). The Nature of Analytical Chemistry Quantitative Analysis provides numerical information of analyte (quantitate the exact amount or concentration). The Nature of Analytical Chemistry Qualitative analysis is what. Quantitative analysis is how much. The Nature of Analytical Chemistry Analyte - are components of a sample that are to be determined. Matrix - other components in the sample which are not of interest Analytical Methods Classical Methods: Wet chemical methods such as precipitation, extraction, distillation, boiling or melting points, gravimetric and titrimetric measurements. Analytical Methods: Classical Gravimetric methods – determine the mass of analyte Analytical Methods: Classical Volumetric method – volume of reagent needed to completely react with analyte Analytical Methods: Instrumental Instrumental Methods: Analytical measurements (conductivity, electrode potential, light absorption or emission, mass-to-charge ratio, fluorescence etc.) are made using instrumentation. Analytical Methods: Instrumental Electroanalytical analysis - a collection of techniques that use electrical stimulation to analyze the chemical reactivity of a sample surface or a solution. Analytical Methods: Instrumental Spectroscopic methods- interaction between electromagnetic radiation and analyte Analytical Methods: Chromatographic Chromatographic Methods- separation is based on the interaction of the analyte in the mobile phase and the stationary phase Analytical Methods: Miscellaneous Mass spectrometry - an analytical tool useful for measuring the mass-to- charge ratio (m/z) of one or more molecules present in a sample. THANK YOU!  MODULE 1: INTRODUCTION TO ANALYTICAL CHEMISTRY LESSON 1.1b: Steps in Quantitative Analysis Instructor: Michael John G. Bation QUANTITATIVE ANALYSIS provides numerical information of analyte (quantitate the exact amount or concentration). Qualitative analysis is what. Quantitative analysis is how much. a. Choosing a method is sometimes difficult and requires experience as well as intuition b. In the selection process the level of accuracy required must be considered But high reliability nearly always requires a large investment of time c. Selected method usually represents a compromise between the accuracy required and the time and money available for the analysis. d. Next consideration is the number of samples that will be analyzed If there are many samples, we can afford to spend a significant amount of time in preliminary operations such as assembling and calibrating instruments and equipment and preparing standard solutions e. Finally, the complexity of the sample and the number of components in the sample always influence the choice of method to some degre a. An analysis must be performed on a sample that has the same composition as the bulk of material from which it was taken b. When the bulk is large and heterogeneous, great effort is required to get a representative sample A material is heterogeneous if its constituent parts can be distinguished visually or with the aid of a microscope c. An assay is the process of determining how much of a given sample is the material by its indicated name For example, a zinc alloy is assayed for its zinc content, and its assay is a particular numerical value. Assayed d. Sampling is the process of collecting a small mass of a material whose composition accurately represents the bulk of the material being sampled We analyze samples, and we determine substances sampling samples e. The collection of specimens from biological sources represents a second type of sampling problem e.g Sampling of human blood for the determination of blood gases illustrates the difficulty of acquiring a representative sample from a complex biological system sampling e. The collection of specimens from biological sources represents a second type of sampling problem e.g Sampling of human blood for the determination of blood gases illustrates the difficulty of acquiring a representative sample from a complex biological system sampling a. Under certain circumstances, no sample processing is required prior to the measurement step b. Under most circumstances, the sample is processed in one of the several different ways. a. A solid laboratory sample is ground to decrease particle size, mixed to ensure homogeneity, and stored for various lengths of time before analysis begins Grinding/ Homogenuous Milling Sample b. Liquid samples be placed in closed containers so the solvent does not evaporate and change the concentration of the analyte Liquid Sample Sampling c. If the analyte is a gas dissolved in a liquid, the sample container must be kept inside a second sealed container Sampling a. Most chemical analyses are performed on replicate samples whose masses or volumes have been determined by careful measurements b..Replicates are portions of a material of approximately the same size that are carried through an analytical procedure at the same time and in the same way a. Ideally, the solvent should dissolve the entire sample, including the analyte, rapidly and completely Unfortunately, many materials that must be analyzed are insoluble in common solvents b. Converting the analyte in such materials into a soluble form is often the most difficult and time-consuming task in the analytical process. c. The sample may require heating with aqueous solutions of strong acids, bases, oxidizing and reducing agents etc. d. It may be necessary to ignite the sample in air or oxygen or to perform a high-temperature fusion of the sample in the presence of various fluxes. A flux is a material, often an alkali metal salt, that is mixed with the sample and heated to form a fused salt. a. An interference or interferent is a species that causes an error in an analysis by enhancing or attenuating (making smaller) the quantity being measured. b. Most demanding aspect of an analysis a. Techniques or reactions that work for only one analyte are said to be specific b. Techniques or reactions that apply to only a few analytes are selective. Dimethylglyoxime Dimethylglyoxime- Ni2+ complex a. All analytical results depend on a final measurement X of a physical or chemical property of the analyte b. Ideally, the measurement of the property is directly proportional to the concentration, that is: k is a proportionality constant c. The process of determining k is thus an important step in most analyses; this step is called a calibration a. Calibration is the process of determining the proportionality between analyte concentration and a measured quantity a. Computing analyte concentrations from experimentaldata by utilizing the generated calibration curve b. Computations are based on the raw experimental data collected, the characteristics of the measurement instruments, and the stoichiometry of the analytical reaction Limit of detection, LOD is the lowest concentration that can be measured (detected) with statistical significance by means of a given analytical procedure.  Limit of quantification, LOQ is the lowest concentration of a substance by means of a given analytical procedure with the established accuracy, precision, and uncertainty. Limit of linearity (LOL) – is the concentration at which the calibration curve departs from linearity Dynamic range - range of concentrations an instrument can read, from the minimum to the maximum detectable a. An analytical result without an estimate of reliability is of no value. b. Statistical analysis are often performed. THANK YOU!