Chapter 1: The Nature of Analytical Chemistry PDF

Chapter 1 The Nature of Analytical Chemistry?  Introduction What is chemistry ? Chemistry (kem'is tree): noun. The science in which substances are Structure examined to find out what they are made of, how they a...

Chapter 1 The Nature of Analytical Chemistry?  Introduction What is chemistry ? Chemistry (kem'is tree): noun. The science in which substances are Structure examined to find out what they are made of, how they act under different conditions, and how they are combined or Reactions separated to/from other substances. To paraphrase that, chemistry deals with finding what different substances are made of, what kind of transformations take place, and different chemically related facts about Properties a certain organism or substance. Introduction Fields of chemistry Physical chemistry Analytical chemistry Organic chemistry Inorganic chemistry Biological chemistry What is Analytical Chemistry ? - Analytical chemistry deals with separating, identifying, and quantifying the relative amounts of the components of an analyte. - Analyte = the thing to analyzed; the component(s) of a sample that are to be determined. What is analytical chemistry ? - Qualitative analysis : What is present ? determination of chemical identity of the species in the sample. - Quantitative analysis : How much present ? determination of the amount of species or analytes, in numerical terms. Hence, math is heavily involved. In order to perform quantitative analysis, typically one needs to complete qualitative analysis. One needs to know what it is and then select the means to determine the amount. - Instrumental analysis Several different areas of analytical chemistry: 1. Clinical analysis - blood, urine, feces, cellular fluids, etc., for use in diagnosis. 2. Pharmaceutical analysis - establish the physical properties, toxicity, metabolites, quality control, etc. 3. Environmental analysis - pollutants, soil and water analysis, pesticides. 4. Forensic analysis - analysis related to criminology; DNA finger printing, finger print detection; blood analysis. 5. Industrial quality control - required by most companies to control product quality. 6. Bioanalytical chemistry and analysis - detection and/or analysis of biological components (i.e., proteins, DNA, RNA, carbohydrates, metabolites, etc.). This often overlaps many areas. Develop new tools for basic and clinical research. Classification of Quantitative Methods of Analysis 1) Gravimetric Method: mass is measured. 2) Volumetric Method: volume is measured or used to determine amount of sample via concentration. 3) Instrumental Method: use an instrumental technique to assay the amount of sample: Such as: Electroanalytical based upon electron-transfer Spectroscopy including mass spectrometry Separation: GC, HPLC, CE Miscellaneous analytical methods 1. Mass spectrometry - mass-to-charge ratio of an analyte's decomposition products. 2. Radiochemical methods - measuring rates of radioactive decay by an analyte. 3. Kinetics - measuring reaction rates. 4. Thermal conductivity. 5. Optical activity - measuring the interactions of an analyte with plane- polarized light. 6. Refractometry / Refractive index.  ANALYTICAL CHEMISTRY Analytical Methods - Gravimetry (based on weight) - Titrimetry (based on volume) - Electrochemical (measurement of potential, current, charge, etc) - Spectral (the use of electromagnetic radiation) - Chromatography (separation of materials) - Chemometrics (statistical treatment of data) Methods of Detecting Analytes Physical means mass color refractive index thermal conductivity with electromagnetic radiation (Spectroscopy) absorption emission scattering by an electric charge electrochemistry mass spectrometry As you can see there are a limited number of ways to detect an analyte. However, in each of the above general categories there are a large multitude of specific analytical techniques.  Often from the literature Our resulting # is never absolutely CERTAIN. An example of an analysis problem Steps in a Typical Quantitative Analysis 1. Select a method: accuracy, reliability, time and cost, complexity of sample e.g., blood samples, pharmaceutical products. 2. Sampling: obtaining “a representative sample”, especially important for mass products. Select a small sample of composition that accurately represents the bulk 3. Sample preparation and handling a) Dissolution or digestion of samples Avoiding decomposition conditions. This is especially troublesome for biological samples. b) Preparation of solid samples : Solids are usually ground to a suitable particulate size to get a homogeneous sample. 4. Define replicate sample: accuracy, reliability and cost Interferences: species other than the 5. Eliminating interferences: blank control analyte that affect the measurement 6. Calibration and measurement CA= kX y = mX + b Calibration: process of determining the exact 7. Calculation and data reduction relationship between the property measured and the property sought for (Determination of k) 8. Evaluating results and estimating their reliability This requires appropriate use of statistics. An analytical result without an estimate of reliability is of no value. Specificity and Selectivity Techniques or reactions that work for only one analyte are said to be specific. Techniques or reactions that apply for only a few analytes are selective. Matrix The matrix or sample matrix is all of the components in the sample containing an analyte.