Ebooks

Preface Analysis of any constituents qualitatively and quantitatively is important to any scientific field. Analytical chemistry is a collection of analytical methods. It is an approach to study chemical problems. It is the ideal place in the undergraduate curriculum in science for explaining topics such as common laboratory tools and apparatus, volumetric, gravimetric and instrumental methods. Analytical methods may come and go but the practice for designing and validating analytical methods are universal. Our goal in preparing this text book is to find a more appropriate balance between classical and modern analytical methods. Therefore in order to understand the basic analytical principles, various analytical methods such as volumetry, gravimetry and instrumental methods this book has been written in simple and lucid manner to meet out the requirements of students at undergraduate level. We hope that the students find this text book as a valuable valuable resource throughout their career.

Analytical Chemistry The science involving the determination of the constituents in terms of elements and compounds is called Analytical Chemistry. It is used to identify the substances found in a material and to quantify the exact amount of substances in them. The basic principles involved in Analytical Chemistry are changes takes place in the substances by the process of combination, decomposition, replacement and double decomposition.

Laboratory analysis is an important part in any branch of chemistry and analytical chemistry in particular. To undertake the analysis, both apparatus and equipments are needed.

Standard solutions Standard solutions are solutions of accurately known concentration Different standard solutions are

Volumetric Analysis Measurement of volume of reagents required for the completion of reactions Also called titrimetry – most widely used techniques of chemical analysis Rapid, accurate, convenient and inexpensive

Secondary standard solution Solution of chemicals which lack one (or) all the properties for a primary standard A solution standardised by titrating a primary standard Less accurate than a primary standard

Indicator A substance which indicates the end point on completion of the reaction. Helps in the visual determination of the completion of titration.

Volumetry / Titrimetry Process of determining the volume of solution of known concentration required to complete reaction with a solution of unknown concentration (test solution) by titration.

Gravimetric analysis Techniques – analyte is determined by quantitative isolation of substance by precipitation and weighing the precipitate

Precipitation An ionic phenomena wherein the product of the ionic concentrations of a substance in a solution exceeds the solubility product Precipitate is often ignited before weighing to convert it into substance of definite chemical composition and chemical stability Compound precipitated –– precipitated form Example: Magnesium ammonium phosphate

I. Filtration Filtration is a process of separation of precipitate from solution. Filtration is used to remove impurities from a solution (or) to isolate a solid.

Potentiometry Potentiometry is based on measurement of potential of an electrode system Principle When a metal electrode is immersed in a solution containing its own ions, the metal atom pass into the solution in the form of metal ions and a potential difference is established between the metal and the solution. This potential is called as electrode potential. Potential on an electrode depends on the ions present in solution and their concentration which can be determined by using electrochemical cells and expressed by Nernst equation

Colorimetry is the quantitative analysis of a coloured constituent. It is determined by measuring the relative amount of absorption of light passing through a solution of a constituent. When a monochromatic light is passed through a homogeneous medium, a part of the incident light is absorbed and part of the light is reflected and part could be transmitted. This can be mathematically expressed as

Absorption and Emission Absorption techniques – It measures the absorption of abundance of light due to electrons going to a higher energy level. Emission techniques - It measures the intensity of light that is emitted as electrons return to the lower energy levels.

Chromatography is the set of laboratory techniques used for the separation of molecular mixtures by developing chromatograms. Chromatogram is a collection of different bands on the chromatographic column. The mixture is dissolved in a fluid called the “mobile phase”, which carries with it another material called the “stationary phase”. The various constituents of the mixture travel at different speeds, causing them to separate. Chroma (colour) and graph in (to write) contribute to the word chromatography, as coined by Mikhail Tswett (1903). Solute moves only when it is in stationary phase. In chromatography, the mobile phase flowing into the column is called eluent, the solution emerging from the column is elute, and the process by which solutes moves and separate is called elution. This method employs the differences in absorbability of components of mixtures and the differences in the mobility rate. The molecules of a substance which interact strongly with the fixed phase will move slowly through the column whereas substances which do not interact strongly are carried through more rapidly. It is used to separate different substances having similar chemical properties.

Radiation Chemistry is a branch of nuclear chemistry that deals with the study of chemical effects of radiation on matter. Radio activity is the process by which an atomic nucleus of an unstable atom loses energy by emitting ionizing radiations (a, b, g radiations). It may be of

Radiation emitted from the radioactive isotopes can be detected and quantified by using several equipments and the details are furnished below: A. Radiation Detection Devices 1. Electroscope The electroscope is a simple device comprised of a metal rod with two thin leaves attached to one end. If the electroscope is given a negative charge, the metal leaves will separate from each other. It is the characteristic that makes the electroscope useful as a detection device. A negatively charged electroscope will discharge when ions in the air remove electrons from it, and consequently, a positively charged electroscope will discharge when it takes electrons from the air around it. The rate of discharge of the electroscope is a measure of ions in the air and can be used as a basis of measurement and detection.

Stable isotopes are chemical isotopes that may or may not be radioactive,but if radioactive, have half-lives too long to be measured. These isotopes decay into stable products. Eg. 14C having 6protons and electrons with 8 neutrons. Most elements of biological interest (including C, H, O, N, and S) have two or more stable isotopes. Among the stable isotopes, the most useful as biological tracers are the heavy isotopes of carbon and nitrogen.

1. Neutron activation analysis This technique is used in qualitative and quantitative analysis. If an element present in a sample is to be identified by neutron activation analysis, the sample will be bombarded with slow neutrons or other charged particles and converted into radioisotope. It is one of the most sensitive and specific methods available for the determination of trace quantities of a wide range of elements. From the half life measurement, it is possible to identify the element from which the radioisotope has resulted. Also the quantity of element present in a given sample can be calculated by this technique.