Analytical Chemistry Lecture Notes PDF

‫جامعة سومر كلية الطب‬ ‫كيمياء طبية –مرحلة اولى‬ Introduction to Analytical Chemistry ,Definition, Scope and Classification M.S.C.Hussein Flayyih Hassan 2024- 2025 1 Analytical chemistry is...

‫جامعة سومر كلية الطب‬ ‫كيمياء طبية –مرحلة اولى‬ Introduction to Analytical Chemistry ,Definition, Scope and Classification M.S.C.Hussein Flayyih Hassan 2024- 2025 1 Analytical chemistry is the branch of chemistry that deals with the analysis of different substances, and it involves the separation, identification, and the quantification of matter. by using of classical methods along with modern scientific instruments to achieve all these purposes. Analytical chemistry is often described as the area of chemistry responsible for: 1. Characterizing the composition of matter, both qualitatively and quantitatively. 2. Improving established analytical methods. 3. Extending existing analytical methods to new types of samples. 4. Developing new analytical methods for measuring chemical phenomena. sample is anything that comes to mind in the air, water, soil, food and living organisms such as a piece of rock or a piece of meat or some water from the tank of the house or from a river or a lack or a sea or some tissue or blood from humans or animals or some vegetables.... etc. The sample is taken to the laboratory and analyzed for its substances ( analytes ) after pretreatment and the final step is the calculations of the percentage of each substance in the sample. An analyte is a constituent of a sample that is analyzed for , and its concentration is determined. The scope of analytical chemistry: The science seeks ever-improved means of measuring the chemical composition of natural and artificial materials by using techniques to identify the substances that may be present in a material and to determine the exact amounts of the identified substance. Analytical chemistry involves the analysis of matter to determine its composition and the quantity of each kind of matter that is present. Analytical chemists detect traces of toxic chemicals in water and air. A detection of the component in qualitative analysis can be the basis of the method or the procedure of its quantitative analysis. The reaction may be incomplete in qualitative analysis, while in quantitative analysis the reaction should be complete and give clear and known products. 2 Analytical chemistry consists of: (A) Qualitative analysis: which deals with the identification of elements, ions, or compounds present in a sample (tells us what chemicals are present in a sample). (B) Quantitative analysis: which is dealing with the determination of how much of one or more constituents is present (tells how much amounts of chemicals are present in a sample). This analysis can be divided into three types: (1) Volumetric analysis (Titrimetric analysis): is measured the volume of a solution containing sufficient reagent to react completely with the analyte. (2) Gravimetric analysis: Gravimetric methods, determine the mass of the analyte or some compound chemically related to it. (3) Instrumental analysis: These methods are based on the measurement of physical or chemical properties using special instruments. These properties are related to the concentrations or amounts of the components in the sample. These methods are compared directly or indirectly with typical standard methods. These methods consist of: a) Spectroscopic methods: are based on measurement of the interaction between electromagnetic radiation and analyte atoms or molecules or on the production of such radiation by analytes (ultraviolet, visible, or infrared), fluorimetry, atomic spectroscopy (absorption, emission), mass spectrometry, nuclear magnetic resonance spectrometry (NMR), X-ray spectroscopy (absorption, fluorescence). b) Electroanalytical methods: involve the measurement of such electrical properties that wanted to be determined, such as pH measurements, electrodeposition, voltametry, thermal analysis, potential, current, resistance, and quantity of electrical charge. 3 c) Separation methods: They mean the isolation of one component or more from a mixture of components in solid, liquid and gas cases. These methods are included with instrumental methods since the instruments and equipment's are used in separation processes. These methods involve precipitation, volatilization, ion exchange, extraction with solvent and various chromatographic methods. Modern analytical chemistry Modern analytical chemistry is dominated by instrumental analysis. There are so many different types of instruments today that it can seem like a confusing array of acronyms rather than a unified field of study. Many analytical chemists focus on a single type of instrument. Academics tend to either focus on new applications and discoveries or on new methods of analysis. The discovery of a chemical present in blood that increases the risk of cancer would be a discovery that an analytical chemist might be involved in. An effort to develop a new method might involve the use of a tunable laser to increase the 4 specificity and sensitivity of a spectrometric method. Many methods, once developed, are kept purposely static so that data can be compared over long periods of time. This is particularly true in industrial quality assurance (QA), forensic and environmental applications. Analytical chemistry plays an increasingly important role in the pharmaceutical industry where, aside from QA, it is used in discovery of new drug candidates and in clinical applications where understanding the interactions between the drug and the patient are critical. Types Traditionally, analytical chemistry has been split into two main types, qualitative and quantitative: Qualitative  Qualitative inorganic analysis seeks to establish the presence of a given element or inorganic compound in a sample.  Qualitative organic analysis seeks to establish the presence of a given functional group or organic compound in a sample. Quantitative  Quantitative analysis seeks to establish the amount of a given element or compound in a sample. Traditional analytical techniques Although modern analytical chemistry is dominated by sophisticated instrumentation, the roots of analytical chemistry and some of the principles used in modern instruments are from traditional techniques many of which are still used today. These techniques also tend to form the backbone of most undergraduate analytical chemistry educational labs. Examples include: 5 Titration Titration involves the addition of a reactant to a solution being analyzed until some equivalence point is reached. Often the amount of material in the solution being analyzed may be determined. like the acid-base titration involving a color changing indicator. There are many other types of titrations, for example potentiometric titrations. Gravimetry Gravimetric analysis involves determining the amount of material present by weighing the sample before and/or after some transformation. A common example used in undergraduate education is the determination of the amount of water in a hydrate by heating the sample to remove the water such that the difference in weight is due to the water lost. Instrumental Analysis Spectroscopy Spectroscopy measures the interaction of the molecules with electromagnetic radiation. Spectroscopy consists of many different applications such as atomic absorption spectroscopy, atomic emission spectroscopy, ultraviolet-visible spectroscopy, infrared spectroscopy, Raman spectroscopy, nuclear magnetic resonance spectroscopy, photoemission spectroscopy. Mass Spectrometry Mass spectrometry measures mass-to-charge ratio of molecules using electric and magnetic fields. There are several ionization methods: electron impact, chemical ionization, electrospray, matrix assisted laser desorption ionization, and others. 6 Also, mass spectrometry is categorized by approaches of mass analyzers: magnetic-sector, quadrupole mass analyzer, quadrupole ion trap, Time-of-flight, Fourier transform ion cyclotron resonance. Crystallography Crystallography is a technique that characterizes the chemical structure of materials at the atomic level by analyzing the diffraction patterns of usually x rays that have been deflected by atoms in the material. From the raw data the relative placement of atoms in space may be determined. Electrochemical Analysis Electrochemistry measures the interaction of the material with an electric field. Thermal Analysis Calorimetry and thermogravimetric analysis measure the interaction of a material and heat. Separation Separation processes are used to decrease the complexity of material mixtures. Chromatography and electrophoresis are representative of this field. 7 Hybrid Techniques Combinations of the above techniques produce "hybrid" or "hyphenated" techniques. Several examples are in popular use today and new hybrid techniques are under development. For example, Gas chromatography-mass spectrometry. Microscopy The visualization of single molecules, single cells, biological tissues and nano- micro materials is very important and attractive approach in analytical science. Also, hybridization with other traditional analytical tools is revolutionizing analytical science. Microscopy can be categorized into three different fields: optical microscopy, electron microscopy, and scanning probe microscopy. Recently, this field is rapidly progressing because of the rapid development of computer and camera industries. 8 Lab-on-a-chip Miniaturized analytical instrumentation, which is also called as microfluidics or micro total analysis system (μTAS). The beauty of lab-on-a-chip system is that a whole device can be visualized under a microscope. Methods and data analysis Standard Curve A standard method for analysis of concentration involves the creation of a calibration curve. This allows for determination of the amount of a chemical in a material by comparing the results of unknown sample to those of a series known standards.If the concentration of element or compound in a sample is too high for the detection range of the technique, it can simply be diluted in a pure solvent. If the amount in the sample is below an instrument's range of measurement, the method of addition can be used. In this method a known quantity of the element or compound under study is added, and the difference between the concentration added, and the concentration observed is the amount actually in the sample. 9 Solutions Solution: Homogeneous mixture of two or more substance produce from dissolved (disappeared) solute particle (ions, atoms, molecules) (lesser amount) between solvent particle (larger amount). Solute (lesser amount) + Solvent (larger amount) Solution Concentrated Solution has a large amount of solute. Dilute Solution has a small amount of solute. Classification of solutions according to amount of solute: (1) Unsaturated solutions: if the amount of solute dissolved is less than the solubility limit, or if the amount of solute is less than capacity of solvent. 10 Classification of solutions according to amount of solute: (1) Unsaturated solutions: if the amount of solute dissolved is less than the solubility limit, or if the amount of solute is less than capacity of solvent. 4 (2) Saturated solutions: is one in which no more solute can dissolve in a given amount of solvent at a given temperature, or if the amount of solute equal to capacity of solvent. (3) Super saturated solutions: solution that contains a dissolved amount of solute that exceeds the normal solubility limit (saturated solution). Or a solution contains a larger amount of solute than capacity of solvent. This it's occurs when the solution is heated to a high temperature. Classification of solution based on solute particle size: (1) True solution: A homogeneous mixture of two or more substance in which substance (solute) has a particle size less than 1 nm dissolved in solvent. Particles of true solution cannot be filtered through filter paper and are not visible to naked eye (NaCl in water). (2) Suspension solution: heterogeneous mixtures which settles on standing and its components can be separated by filtrating (Amoxcycilline Antibiotics), particle of solute visible to naked eye. (3) Colloidal solution: homogeneous mixture which does not settle on standing, nor are their components filterable, solute particle visible with electron microscope (milk). Stoichiometric Calculations Gram atomic weight: (gAw some time Awt): Is the weight of a specified number of atoms of that element (contains exactly the same number of atoms of that element as there are carbon atoms in exactly 12g of carbon 12 (this number is Avogadro’s number = 6.0221023 atoms). Gram molecular weight: (gMw some times M.wt): Defined as the sum of the atomic weight of the atoms that make up a molecular compound. Or the weight of Avogadro's number of molecules of any compound. 11 Gram formula weight: (gFw some time F.wt): The sum of the atomic weight of the atoms that make up an ionic formula. (is the more accurate description for substances that do not exist as molecules but exist as ionic compounds e.q strong electrolytes-acids, bases, salts). Sometimes use the term molar mass (Molecular weight, M.wt) in place of gram formula weight, gFw). Example (1):- Calculate the number of grams in one mole of CaSO4.7H2O (calculate gram molecular or formula weight). Solution: One mole is the formula weight expressed in grams. The formula weight is (Ca=40.08, S=32.06, O=16.00, H=1.01) [ ] Mwt of CaSO4.7H2O = Ca ×1 = 40.08×1 = 40.08 S × 1 = 32.06 ×1 = 32.06 O × 4 = 16 × 4 = 64.00 H ×14 = 1.01 × 14 = 14.14 O × 7 = 16 × 7 = 112.00 --------- 262.28 (gm/mol) Mole Concept: Mole which is Avogadro’s number (6.0221023) of atoms, molecules, ions or other species. Numerically: it is the atomic, molecular, or formula weight of a substance expressed in grams. Where formula weight represents the atomic or molecular weight of the substance. Example (2):-Calculate the number of moles in 500 mg Na2WO4. 12 Example (4):-How many milligrams are in 0.250 mmole Fe2O3 (ferric oxide). Solution: (A.wt O= 16 g/mole , Fe = 56.85 g/mole) Example (5):- Calculate the number of mole of NaCl required to prepare 1Kg of AgCl according to the equation: ( Na=23, Cl=35.5, N=14 , Ag =107.86, O = 16 g/mole) 13 according to the balance equation the mole ratio between NaCl & AgCl equal 1:1 therefore we need 6.98 mol of NaCl. Example (6 ):Calculate the number of mole of Ca(HCO3)2 required to prepare 1.5 mol of CO2 according to the equation. How do we express concentrations of solutions 14 1-The Molarity Concentration: - Also called (Molarity, amount of concentration or substances concentration) is a measure of the concentration of a chemical species in a particular of a solute in a solution, in terms of amount of substance per unit volume of solution. In chemistry, the most commonly used unit for molarity is the number of moles per litre, having the unit symbol (mol./L). A solution with a concentration of 1 mol./L is said to be 1 Molar, commonly designated as 1M. Example (8):-A solution is prepared by dissolving 1.26 gm AgNO3 in a 250 mL volumetric flask and diluting to volume. Calculate the molarity of the silver nitrate solution. How many millimoles AgNO3 were dissolved? 15 16 17 18 Diluting Solutions We often must prepare dilute solutions from more concentrated stock solutions. For example, we may prepare a dilute HCL solution from concentrated HCL to be used for titration.Or, we may have a stock standard solution from which we wish to prepare a series of more dilute standards. The millimoles of stock solution taken for dilution will be identical to the millimoles in the final diluted solution Example (14):-You wish to prepare a calibration curve for the spectrophotometric determination of permanganate. You have a stock 0.100 M solution of KMnO4 and a series of 100 mL volumetric flasks. What volumes of the stock solution will you have to pipet into the flasks to prepare standards of 1.00, 2.00, 5.00, and 10.0x10-3 M KMnO4 solutions? Normal concentration Normality (N): Number of equivalent solute in solution volume in litre 19 Example (25):- Calculate the normality of the solutions containing the following: (a) 5.300gm/L Na2CO3 (when the CO3-2 reacts with two protons), (b) 5.267 gm/L K2Cr2O7 (the Cr6+ is reduced to Cr3+). 20 Example (26):- How many millilitres of a 0.25M solution of H2SO4 will react with 10mL of a 0.25M solution of NaOH. 21