1 Introduction to Analytical Chemistry

• Analytical chemistry is a branch of science that deals with the separation, identification and determination of the components in a sample.
• Analytical chemistry is particularly concerned with the questions of "what chemicals are present, what are their characteristics and in what quantities are they present?"
• Accuracy in analytical chemistry pertains to agreement of an experimental result with the true value, and is near to the true value.
• Precision in analytical chemistry is the measure of reproducibility of data within a series of results, and the results are near each other and near the true value.
• The ultimate goal in analytical chemistry is to have an accurate and precise final answer.
• In every experiment, you can encounter not just positive, but negative results (rejecting the hypothesis).
• 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 element s using a very small amount of sample.
• The 1st group of anions consists of CO 3 2 - , HCO 3 - , CH 3 COO - , S 2 - , SO 3 2 - , S 2 O 3 2 - and NO 2 -.
• Qualitative inorganic analysis is now used only as a pedagogical tool.
• The group reagent for Group 1 anion is HCL(dil) or H 2 SO 4
• Nitrates can be reduced to ammonia.
• All non-zero are significant in significant figures.
• All zeros to the left of the expressed decimal point and to the right of a non-zero digit are not significant in significant figures.
• All zeros to the left of an implied decimal point and to the right of a non-zero digit are significant in significant figures.
• When the numbers follow a unit, bar or scientific notation, all zeros to the right of a decimal point and to the right of a non-zero digit are significant in significant figures.
• Qualitative analysis is a method of analytical chemistry which seeks to find elemental composition of inorganic compounds and the functional group of organic compounds.
• Quantitative analysis is the measurements of quantities of substances produced in reactions.
• Qualitative chemistry involves identification, composition determination, and ascertainment of impurities.
• Total anti-oxidant in a malunggay leaf can be determined through Ultimate Analysis, which involves the amount of a specific constituent or a single chemical species present in the sample.
• Neutralization is a chemical reaction where a base and acid react to form a salt.
• Instrumental Method, which is more accurate and based on specific physical or chemical properties of the analyte, includes Spectrometry, polarimetry, and chromatography.
• Precipitation is a process in which a solid is separated from a suspension or solution.
• Volumetric Analysis is an analysis involving the measurement of volume of a solution of known concentration required to react with the desired constituent.
• Gravimetric Analysis is an 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.
• Complexometry is a form of volumetric analysis in which the formation of a colored complex is used to indicate the end point of a titration.
• Physico-chemical Methods are 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, and fluorometer.
• Miscellaneous or Special Method involves the crude drugs and other natural products, such as PCR Testing.
• Classical Method, also known as general/ chemical/ wet/ stoichiometric method, includes titrimetric analysis and gravimetric analysis.
• Oxidation-reduction reactions include permanganate, ceric sulfate, iodometry, iodimetry, bromine, potassium iodate, and diazotization assay with nitrite.
• Quantitative chemistry involves determination of the proportion of components in a substance, based on computations such as stoichiometry, instrumental methods, etc.
• Analysis can be classified based on sample size, extent of determination, nature of methods, and materials used.
• Sample size in analysis can be analyzed by ultramicroanalysis (< 1 mg), microanalysis (1 mg – 10 mg), semi-microanalysis (10 mg – 100 mg), and macroanalysis (100 mg – 1 g).
• Extent of determination in analysis can be classified as proximate analysis (total amount of a class or a group of active plant principles in a given sample).
• Concentration of the reagents may affect the result, so follow the procedure to analyze well.
• Halides are precipitated by silver nitrate; they can be further identified by color.
• 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.
• The reagents are similar to those of the 2nd group, but separation is conducted at pH of 8 – 9.
• Acids beside HCl are rarely used.
• Cations which are left after carefully separating previous groups are considered to be in the fifth analytical group.
• Caution should be taken to properly separate all lower analytical groups beforehand, as many of cations in previous groups also form insoluble carbonates.