Analytical Chemistry: Introduction Analytical Chemistry • Branch of science that deals with the __________________________________ ______of the components in a sample 27 Jun 2021 2 Analytical Chemistry • Analytical chemistry is particularly concerned with the questions of “___________________, ___________ and _____________________?" 27 Jun 2021 3 Analytical Chemistry Biology Botany Genetics Microbiology Molecular Biology Zoology Chemistry Biochemistry Inorganic Chemistry Organic Chemistry Physical Chemistry Physics Astrophysics Astronomy Biophysics Engineering Civil Chemical Electrical Mechanical Geology Geophysics Paleontology Paleobiology Analytical Chemistry Medicine Clinical Chemistry Medicinal Chemistry Pharmacy Toxicology Environmental Sciences Ecology Meteorology Oceanography Agriculture Agronomy Animal Science Crop Science Food Science Horticulture Soil Science 27 Jun 2021 Social Sciences Archeology Anthropology Forensics Materials Science Metallurgy Polymers Solid State 4 Accuracy and precision • Accuracy pertains to agreement of an experimental results with true value • Precision is the measure of reproducibility of data within a series of results. Accuracy and Precision Types of Analytical Chemistry • _________________ – is a method of analytical chemistry which seeks to find elemental composition of inorganic compounds and the functional group of organic compounds. • ________________ – in analytical chemistry, the measurements of quantities of substances produced in reactions rather than simply noting the nature of the reactions 27 Jun 2021 7 1. Qualitative Chemistry • What is in the sample? Identification Composition determination Ascertainment of impurities 2. Quantitative chemistry • How much is in the sample? determination of the proportion of components in a substance Classification of Analysis I. Based on ______________ II. Based on _________________ III. Based on ___________________ IV. Based on ________________ I. Based on sample size • • • • Ultramicroanalysis Microanalysis Semi-microanalysis Macroanalysis ________ ___________ ____________ ___________ II. Based on the extent of determination • __________________ total amount of a class or a group of active plant principles in a given sample. • __________________ Amount of a specific constituent or a single chemical species present in the sample III. Based on the nature of methods A. Classical method B. Instrumental method C. Miscellaneous or special method III. Based on the nature of methods A. Classical method – also known as _________________ method – example : titrimetric analysis gravimetric analysis III. Based on the nature of methods B. Instrumental method – more accurate – based on _______________________ – Examples: spectrometry polarimetry chromatography III. Based on the nature of methods C. Miscellaneous or special method – Involves the __________________ – Examples: Acid value Ash content Water content IV. Based on materials used • Chemical = ________________ • Physical = _________________ • Biological = _________________ Types of Quantitative Analysis A. _________________ B. _________________ C. _________________ D. _________________ Types of Quantitative Analysis A. Volumetric Analysis analysis involving the measurement of volume of a solution of known concentration required to react with the desired constituent. Types of Quantitative Analysis Divisions of volumetric analysis: I. Neutralization II. Precipitation III. Compleximetry IV. Oxidation-reduction permanganate ceric sulfate iodometry iodimetry bromine potassium iodate diazotization assay with nitrite Types of Quantitative Analysis B. Gravimetric Analysis Analysis involving the accurate measurement of weight of substance being determined which may be isolated in pure form or converted to another substance of known composition by making it react quantitatively with another substance usually a precipitant. Types of Quantitative Analysis C. Special Methods analysis which require a distinct type of technique such as analysis of crude drugs, assay of fats and fixed oils, assay of volatile oils and assay of alkaloids. Types of Quantitative Analysis D. Physico-Chemical Methods Analysis based on some specific physical or chemical property or properties of the substance being analyzed with the use of instruments such as: spectrophotometer, chromatograph units, polarographer, polarimeter, flourometer. Specialized Analytical Methods and Equipment • ___________ -determination of alcohol, protein components, volatile component, alkaloids • ___________ – physical characterization • ___________ – rotatory power • ___________ – purity of substance • ___________ – moisture content Specialized Analytical Methods and Equipment • _____________ – moisture content • _____________ – moisture content • _____________ – identity and quantity of component • _____________ – identity and purity • _____________ – quality and quantity of components • _____________ – determination of amounts required to produce the desired, definite effect Qualitative Inorganic Analysis • Detecting Cations – According to their properties, cations are usually classified into five groups. – Each group has a common reagent which can be used to separate them from the solution. The separation must be done in the sequence specified, otherwise, some ions of 1st group can also react with 2nd group reagent, so that the solution must not have any ions left from previous groups to obtain meaningful results. 27 Jun 2021 26 1st analytical group of cations • 1st analytical group of cations consists of ions that form ______________. • As such, the group reagent to separate them is _____________, usually used at a concentration of _____. Concentrated HCl must not be used, because it forms a soluble complex ion ([PbCl4]2-) with Pb2+. Consequently the Pb2+ ion would go undetected. 27 Jun 2021 27 1st analytical group of cations • The most important cations in 1st group are ___, _____, and _____. The chlorides of these elements cannot be distinguished from each other by their colour - they are all white solid compounds. • PbCl2 is soluble in hot water, and can therefore be differentiated easily. 27 Jun 2021 28 1st analytical group of cations • Ammonia is used as a reagent to distinguish between the other two. While AgCl dissolves in ammonia (due to the formation of the complex ion [Ag(NH3)2]+), Hg2Cl2 gives a black precipitate consisting of a mixture of chloro-mercuric amide and elemental mercury. Furthermore, AgCl is reduced to silver under light, which gives samples a violet colour. 27 Jun 2021 29 1st analytical group of cations • PbCl2 is far more soluble than the chlorides of the other two ions, especially in hot water. • Therefore, HCl in concentrations which completely precipitate Hg22+ and Ag+, may not be sufficient to do the same to Pb2+. • Higher concentrations of Cl- cannot be used for the aforementioned reasons. • Thus, a filtrate obtained after first group analysis of Pb2+ contains an appreciable concentration of this cation, enough to give the test of the second group, viz. formation of an insoluble sulfide. • For this reason, Pb2+ is usually also included in the 2nd analytical group. 27 Jun 2021 30 2nd analytical group of cations • The 2nd analytical group of cations consists of ions that forms ____________. • Cations in the 2nd group include: ____, ____, ____, ____, ____, _____, ____, ____, ____ and ____. • Pb2+ is usually also included here in addition to the first group. 27 Jun 2021 31 2nd analytical group of cations • The reagent can be any substance that gives S2ions in such solutions; most commonly used are ____________, CH3CSNH2 (_________/ATK)(at 0.3-0.6 M). • The test with the sulfide ion must be conducted in the presence of dilute HCl. • Its purpose is to keep the sulfide ion concentration at a required minimum, so as to allow the precipitation of 2nd group cations alone. 27 Jun 2021 32 2nd analytical group of cations • If dilute acid is not used, the early precipitation of 4th group cations (if present in solution) may occur, thus leading to misleading results. • Acids beside HCl are rarely used. Sulfuric acid may lead to the precipitation of the 4th group cations, while nitric acid directly reacts with the sulfide ion (reagent), forming colloidal sulfur. 27 Jun 2021 33 2nd analytical group of cations • The precipitates of these cations are almost indistinguishable, except for CdS which is yellow. • All the precipitates, except for HgS, are soluble in dilute mineral acids. HgS is soluble only in aqua regia, which can be used to separate it from the rest. 27 Jun 2021 34 2nd analytical group of cations • The action of ammonia is also useful in differentiating the cations. • CuS dissolves in ammonia forming an intense blue solution, while CdS dissolves forming a colourless solution. • The sulfides of As3+, As5+, Sb3+, Sb5+, Sn2+, Sn4+ are soluble in yellow ammonium sulfide, where they form polysulfide complexes. 27 Jun 2021 35 3rd analytical group of cations • 3rd analytical group of cations includes ions that form ___________________. • The reagents are similar to these of the 2nd group, but separation is conducted at pH of ______. Occasionally, a buffer solution is used to ensure this pH. • Cations in the 3rd group are, among others: ____, ____, ____, ____, ____, ____, ____, and ____. 27 Jun 2021 36 4th analytical group of cations • Ions in 4th analytical group of cations form _________________. • The reagent usually used is (NH4)2CO3 (at around 0.2 M), the pH should be neutral or slightly basic. • Caution should be taken to properly separate all lower analytical groups beforehand, as many of cations in previous groups also form insoluble carbonates. 27 Jun 2021 37 4th analytical group of cations • Most important ions in the 4th group: ____, ____, and ____. After separation, the easiest way to distinguish these ions is by testing flame colour: barium gives a yellow-green flame, calcium orange-red and strontium deep red. 27 Jun 2021 38 5th analytical group of cations • Cations which are left after carefully separating previous groups are considered to be in the fifth analytical group. • The most important ones are ____, ____, ____, ___ and ____. 27 Jun 2021 39 Qualitative Inorganic Analysis • Detecting Anions – Halides are precipitated by silver nitrate; they can be further identified by color. – Sulfates can be precipitated by barium chloride. – Nitrates can be reduced to ammonia. 27 Jun 2021 40 1st analytical group of anions • The 1st group of anions consist of CO32-, HCO3-, CH3COO-, S2-, SO32-, S2O32- and NO2-. • The group reagent for Group 1 anion is ______ or _______. 27 Jun 2021 41 Modern techniques • Qualitative inorganic analysis is now used only as a pedagogical tool. • Modern techniques such as atomic absorption spectroscopy and ICP-MS (Inductively coupled plasma mass spectrometry) are able to quickly detect the presence and concentrations of elements using a very small amount of sample. 27 Jun 2021 42