Analytical Chemistry (Units & Measurements) PDF

Analytical Chemistry (Units & Measurements)  Analytical Chemistry Is the science of obtaining, processing and communicating information about the composition and structure of matter. In other words, it is the art and science of determining what matter is and how much of...

Analytical Chemistry (Units & Measurements)  Analytical Chemistry Is the science of obtaining, processing and communicating information about the composition and structure of matter. In other words, it is the art and science of determining what matter is and how much of it exists  Analytical Chemistry and Other Fields 1- Medicine; analytical chemistry is the basis for clinical laboratory tests which help physicians diagnose disease. 2-Industry; analytical chemistry provides the means of testing raw material. For ex., fuels and clothes. 3- Environmental quality; the air in the cities must be analyzed for carbon monoxide. 4- The nutritional value of food is determined by chemical analysis for major components such as protein and carbohydrates.  Analytical Chemistry Deals with the separation, identification, quantification, and statistical treatment of the components of matter Two Areas of Analytical Chemistry. 1) Qualitative Analysis: Deals with the identification of materials in a given sample (establishes the presence of a given substance).  Analytical Chemistry 2) Quantitative Analysis: Deals with the quantity (amount) of material (establishes the amount of a substance in a sample) - Some analytical methods offer both types of information (GC/MS). Determining how much of material is present in a sample. The most reaction which is used in qualitative analysis can be used as a principle for quantitative analysis with some changes. The most important thing in quantitative analysis was purity…… Always qualitative analysis must be done before quantitative analysis Analytical Chemistry Deals with development of new methods and techniques for the separation and determination of the analyte qualitatively and quantitatively. Total analysis process consists of the following steps: 1-Sampling The most important conditions for sampling are a) The sample must be representative (reflect entire body from which it came). b) b) The sample must be homogeneous (having the composition everywhere) c) Transportation, from the field (sample place) to the laboratory without altering sample. 2- Method The analytical chemist must decide which of the numerous analytical methods available will be appropriate for the problem at hand. Factors that the analyst may have to consider Accuracy and precision Sensitivity Selectivity Speed Cost Legality  3- Separation It involves the removing of the effect of interferences and increases the selectivity of the method toward the analyte with necessary accuracy and precision. 4- Quantitation Involves quantititative measurement of the analyte 5- Evaluation The statistical analysis is an important evaluative tool for analytical chemist. It can be used to determine the accuracy and precision required of the analytical technique. Chemical Methods This method depends on making a chemical reaction for the analyte and this reaction must be having some conditions. 1-Spontaneous and fast reaction 2- Irreversible reaction, and completely reacted 3- Equilibrated reaction 4- No side reaction 5- Clear equivalent point 6- Using indicators for measuring the equivalence point Solutions Solutions are homogeneous mixtures. The major component is called solvent, and the minor components are called solute. When gas or solid material dissolve in a liquid, the gas or solid material is called the solute.  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) Types of Method of determination of samples Gravimetric method: a quantitative method which the amount which the amount of the analyte is determined by the measurement of the mass of pure substance containing the analyte. Volumetric method: a quantitative method which the amount of the analyte is determined by the measurement of the volume. Instrumental method: methods of determine a constituents by measuring some physical property with an instrument are called instrumental method or is a field of analytical chemistry that investigates analytes using scientific instruments.  BASIC TOOLS AND OPERATIONS OF ANALYTICAL CHEMISTRY 1. The Laboratory Notebook—Your Critical Record First of all, there is a saving of time in not having to reorganize and rewrite the data. There is probably an additional saving of time since you will be more organized in carrying out the operations of the analysis if you have trained yourself to put the data down in an orderly fashion. Chances for a mistake are reduced. Second, if you make an immediate record, you will be able to detect possible errors in measurements or calculations. Data will not be lost or transferred incorrectly if they are recorded directly in a notebook instead of collected on scraps of paper.  BASIC TOOLS AND OPERATIONS OF ANALYTICAL CHEMISTRY 2. Laboratory Materials and Reagents  Primary standard chemicals are generally at least 99.95% pure. They are analyzed and the results are printed on the label.  They are more expensive than reagent-grade chemicals and are used only for the preparation of standard solutions or for the standardization of a solution by reaction (titration) with it. There are special grades of solvents for special purposes, for example, spectroscopy or liquid chromatography/mass spectrometry grades. These are specifically purified to remove impurities that might interfere in the particular application.  BASIC TOOLS AND OPERATIONS OF ANALYTICAL CHEMISTRY 3. The Analytical Balance—The Indispensible Tool  In analytical chemistry we deal with rather small weights, on the order of a few grams to a few milligrams or less.  Modern electronic balances offer convenience in weighing and are subject to fewer errors or mechanical failures than are mechanical balances, which have become largely obsolete..  BASIC TOOLS AND OPERATIONS OF ANALYTICAL CHEMISTRY 4. Volumetric Glassware 1- VOLUMETRIC FLASKS Volumetric flasks are used for the dilution of solutions to a certain volume. 2- PIPETS The pipet is used to transfer a particular volume of solution. As such, it is often used to deliver a certain fraction (aliquot) of a solution.  BASIC TOOLS AND OPERATIONS OF ANALYTICAL CHEMISTRY 5 Handling and Treating Samples 1- BLOOD SAMPLES Syringes/needles are used to collect blood samples typically into evacuated glass vials, (Vacutainers). The tube may contain an anti-coagulating agent to prevent clotting of the blood if plasma or whole blood samples are to be analyzed. A finger puncture, instead of a venipuncture, is used when small quantities of blood are to be collected for micro procedures.  BASIC TOOLS AND OPERATIONS OF ANALYTICAL CHEMISTRY 2- DESICCATORS A desiccator is used to keep samples dry while they are cooling and before they are weighed and, in some cases, to dry a wet sample. Dried or ignited samples and vessels are cooled in the desiccator.  BASIC TOOLS AND OPERATIONS OF ANALYTICAL CHEMISTRY 3- OVENS A muffle furnace: is used to ignite samples to high temperatures, either to convert precipitates to a weighable form or to burn organic materials prior to inorganic analysis. A drying oven is used to dry samples prior to weighing. These ovens are well ventilated for uniform heating. The usual drying temperature is about 110◦C A fume hood is used when chemicals or solutions are to be evaporated. When perchloric acid or acid solutions of perchlorates are to be evaporated, the fumes should be collected, or the evaporation should be carried out in fume hoods specially designed for perchloric acid work  BASIC TOOLS AND OPERATIONS OF ANALYTICAL CHEMISTRY 4- WASH BOTTLES A wash bottle of some sort should be handy in any analytical laboratory, to be used for quantitative transfer of precipitates and solutions and to wash precipitates. 5- CENTRIFUGES AND FILTERS A centrifuge has many useful applications, particularly in the clinical laboratory, where blood may have to be separated into fractions such as serum or plasma, and proteins may have to be separated by precipitation followed by centrifuging. Filters for filtering precipitates (e.g., in gravimetric analysis) are of various types.  General Steps in Chemical Analysis 1. Formulating the question (to be answered through chemical measurements) 2. Selecting techniques (find appropriate analytical procedures) 3. Sampling (select representative material to be analyzed) 4. Sample preparation (convert representative material into a suitable form for analysis) General Steps in Chemical Analysis 5- Analysis (measure the concentration of analyte in several identical portions) (multiple samples: identically prepared from another source) (replicate samples: splits of sample from the same source) 6- Reporting and interpretation (provide a complete report of results) 7- Conclusion (draw conclusions that are consistent with data from results)  Q: What is the difference between solvent and solution? Solution: is a uniform mixture of two or more substance. Solvent: The medium in to which the other substance is mixed or dissolve. Solute: is any substance dissolved by the solvent. Solubility: is the amount of solute need to make a saturated solution is a given quantity of solvent at a specific temperature. Q: What is the difference between solvent and solution? FUNDAMENTAL SI UNITS DERIVED SI UNITS METRIC UNITS UNIT CONVERSIONS  The Mole A mole is a fundamental unit describing the amount of chemical substance. It is always, associated with the chemical formula and represents Avogadro's number of the atoms or molecule or ions and electrons. Na = 6.022x 1023 N of molecule= (number of mole x number of Avogadros) N= n NA (n= m (g)/ Mw g/mol)  1- Molarity :M The number of moles for solute divides by the number of liters for the solution containing the solute. Also, express the amount in millimoles and the volume in millilitres Moles= Molarity x Liters Millimoles= Molarity x Milliliters Mmoles= M X ml  2- Normality : N A one-normal solution, 1N, contains one equivalent of species per liter. An equivalent 'represents the mass of material providing Avogadro's number of reacting units. A reacting unit is a proton (H+) or an electron The number of equivalents = # moles X # reacting units per molecule or atom The equivalent weight is the formula weight divided by the number of reacting units.  2- Normality : N The Number of equivalents of solute divided by the number of liters of solution containing the solute and milliliters.  3- Formality: F (F) is the number of formula weight of a solute dissolved in 1 L solution. F= n. f.wt/L OR F= m f.wt./ml  F- is numerically the same as M molarity  F is used for ionic salts that don,t exist as molecules in the solid or in the solution.  Formality=Molarity numerically (F) is used for total analytical concentration  (M) Is used for equilibrium concentration.  3- Formality: F Exactly 5.00g NaCl dissolved in 100 ml distilled water. Calculate the formality of this solution F.wt=58.44 5.00g/58.44g/f.wt=0.0856 F= 0.0856/100x10-3=0.856 g/f.wt/L  4- Molality, m The concentration in the mole in 1000 g of solvent. It is used in physicochemical studies, freezing point. Molal solutions are not temperature dependent like molarity & normality solutions (solvent volume is temperature dependent that solvent weight is not (m) Molal= mole/ 1000 g solvent. Molality= n1/m2 x1000