TOOLS OF ANALYTICAL CHEMISTRY LABORATORY EQUIMENTS AND REAGENTS Topic Outline • Types of Glasswares • Types of Plasticwares • Pipettes and Different Classification of Pipettes • Other Laboratory Equipments • Equipments used in Measuring Mass • Reagents used in Analytical Chemistry • Handling of Reagents LABORATORY MATERIALS COREX has been strengthened chemically than thermally; 6x stronger than borosilicate VOLUMETRIC FLASK Volumetric flasks are calibrated to contain an accurate volume. ©Gary Christian, Analytical Chemistry, 6th Ed. (Wiley) BURET A laboratory apparatus used in quantitative chemical analysis to measure the volume of a liquid or a gas. It consists of a graduated glass tube with a stopcock (turning plug, or spigot) at one end. ©Gary Christian, Analytical Chemistry, 6th Ed. (Wiley) Position the black field just below the meniscus. Avoid parallax error by reading at eye level. LOWER MENISCUS-CLEAR LIQUIDS UPPER MENISCUS- DARK-COLORED LIQUIDS Fig. 2.14. Meniscus illuminator. ©Gary Christian, Analytical Chemistry, 6th Ed. (Wiley) Place the flask on a white background. Place the buret tip in the neck of the flask while your swirl. ©Gary Christian, Analytical Chemistry, 6th Ed. (Wiley) Fig. 2.15. Proper technique for titration. Use these for acid digestions. They are tilted while heating to avoid losses from “bumping”. Kjeld ahl Flask ©Gary Christian, Analytical Chemistry, 6th Ed. (Wiley) TRIPLE BEAM BALANCE ANALYTICAL BALANCE The triple beam balance is a measuring instrument comprising a beam supported on a fulcrum. On one side of this beam, is a pan on which the object to be measured is placed, while on the other side, the beam is split into three parallel beams, each carrying a known weight and together culminating into a pointer pointing to a fixed scale. The weights are slid on their respective beams until zero reading is obtained and a state of balance is achieved. Function: To determine Mass of objects Weighing bottles Weighing bottles are used for drying samples. Hygroscopic samples are weighed by difference, keeping the bottle capped except when removing the sample. ©Gary Christian, Analytical Chemistry, 6th Ed. (Wiley) Weighing dish A weighing dish or boat is used for direct weighing of samples. ©Gary Christian, Analytical Chemistry, 6th Ed. (Wiley) OTHER LABORATORY EQUIMENTS Desiccator and desiccator plate Use a desiccator to cool a dried or ignited sample. Cool a red hot vessel before placing in the desiccator. Do not stopper a hot weighing bottlle (creates a partial vacuum on cooling). ©Gary Christian, Analytical Chemistry, 6th Ed. (Wiley) Muffl e furna ce ©Gary Christian, Analytical Chemistry, 6th Ed. (Wiley) Used to ignite samples at high temperatures, e.g., to dry ash organic matter. DRYI NG OVE N ©Gary Christian, Analytical Chemistry, 6th Ed. (Wiley) Used to dry samples before weighing. Usually 110o C used. Use these for quantitative transfer of precipitates and solutions, and for washing precipitates. Wash bottles: (a) polyethylene, squeeze type; (b) glass, blow type. ©Gary Christian, Analytical Chemistry, 6th Ed. (Wiley) Use for filtering non-gelatinous precipitates. Filtering crucibles: (a) Gooch crucible; (b) sintered-glass crucible; (c) porcelain filter crucible. ©Gary Christian, Analytical Chemistry, 6th Ed. (Wiley) Crucible holders Mount the filtering crucible in a crucible holder and connect the filtering flask to a water aspirator. ©Gary Christian, Analytical Chemistry, 6th Ed. (Wiley) ANALYTICAL REAGENTS WATER It is the most frequently used reagent in the laboratory. Tap water- unsuitable for laboratory applications. Water • 1.Distilled water- purified to remove almost all organic materials • 2.Deionized water- some or all ions are removed, although oraganic materials may still be present, so it is neither pure nor sterile. It is purified from previously treated water, such as prefiltered or distilled water. It is produced using either an anion or cation exchange resin, followed by replacement of the removed particles with hydroxyl or hydrogen ions. Water • 3.Reverse Osmosis- a process that uses pressure to force water through semipermeable membrane, producing water that reflects a filtered product of the original water. It does not remove dissolved gases and may be used as a pretreatment of water. Water • 4.Ultrafiltration- excellent in removing particulate matter, microorganisms a)Ultraviolet oxidationremoves some trace organic materials b)Sterilization processuses specific wavelengths c)Ozone treatment Reagent grade water Reagent grade water It can be obtained by initially removing particulate matter, followed by reverse osmosis, deionization and restrictive filtration. Type I Water- used for methods requiring minimum interference, such as trace metal, iron and enzyme analyses. Type II Water-acceptable for most analytic requirements, including reagents, quality control, and standard preparation. Type III Water- acceptable for glassware washing but not for analysis or reagent preparation. Concentrated Acids This are strong inorganic acids that are often used in analytical determinations. Non-oxidizing acids- HCl, dilute H2SO4, and dilute HClO4 (concentrated H2SO4, and HClO4 act as oxidizing agents at elevated temperatures) Oxiding acids- HNO3 CLASSIFYING CHEMICALS • A.Technical/ Commercial Grade- relatively low purity and are thus used only in the preparation of cleansing solutions. • B.USP and NF Grade- follow the standards set by US Pharmacopeia and National Formulary, these chemicals contain impurities and are used for precised analytical purposes. Theses type of chemicals are encountered often in the medical, pharmaceutical and food additive fields. • C.Chemically Pure and analyzed grades- packed as analyzed grade and labels contain an assay of the major constituents. This type of chemical is usually preferred by most chemist. • D.Primary Standard Grade- highest degree of purity. it is used to standardized solutions to high degree of accuracy and are labelled “conforms to ACS specifications” Handling of Reagents HANDLING OF REAGENTS • 1. Stock bottles or reagents should always be covered either by a glass or rubber stopper to avoid contamination. • 2. To remove the stopper from a reagent bottle, hold the stopper with the first portion between the index and second finger and with the plug projecting from the back of the hand. Stoppers are placed with the flat top inverted on the glasswatch. • 3. Liquids are transferred quantitatively into another container with the use of pipet or with the aid of a stirring rod firmly against the side tip of the vessel. • 4. Excess reagents should be flushed down with plenty of water and should never be returned to the reagent bottle. • 5. Solids are spooned out with a perfectly clean and dry spatula to avoid contamination. The mouth of the reagent bottle should be titled slightly downward to give a fine flow of the chemical. • 6. Acid solutions are prepared by pouring acid to water; alkaline solutions are prepared by pouring the alkali to water. THANK YOU! PREPARE FOR A QUIZ
