Analytical Chemistry: Ma'am Luzviminda Ranay Flashcards
Qualitative
determination of identity of the chemical species
Quantitative
determination of the relative amount of the chemical
specie in each amount of sample
Macro analysis
amount of analyte is more than 0.10 grams (100 mg)
❏ Suspected pollutant in a 1-gram soil sample
Semimicro analysis
amount of analyte is between 0.010 – 0.10 grams
❏ Amount of drug in a 5-mg sample of powder, determination of glucose in a blood sample
Micro analysis
amount of analyte is 10-4 to 10-2 grams
❏ Determination of creatinine in a urine sample
Ultramicro analysis
amount of analyte is less than 10-4 grams
❏ Determination of arsenic, boron, nickel or silicon in the body through urine test
Reagent Grade
Confirms to the minimum standards set forth by the Reagent Chemical Committee
of the American Chemical Society (ACS)
Primary-Standard Grade
Chemicals with extraordinary purity prepared by National Institute of Standards and
Technology (NIST)
Special-Purpose Grade
Chemicals prepared for a particular or specific applications
Handling Reagents and Solutions
❏ Select the best grade of chemical available for analytical work. Whenever possible, pick
the smallest bottle that is sufficient to do the job.
❏ Replace the top of every container immediately after removing reagent. Do not rely on
someone else to do.
❏ Hold the stoppers of reagent bottles between your fingers. Never set a stopper on a
desktop.
❏ Never return any excess reagents to a bottle.
❏ Never insert spatulas, spoons, or knives into a bottle that contains a solid chemical.
❏ Keep the reagent shelf and the laboratory balance clean and neat.
❏ Follow local regulations concerning the disposal of surplus reagents and solutions.
E. Cleaning and Labelling Glass wares
❏ Wash properly apparatuses before using by washing with a liquid detergent (preferably
as it will not leave solid residues in the glass)
❏ Wash it with tap water then several small portions of distilled water (usually with the use
of wash bottle). Properly cleaned water will show uniform and unbroken film of water.
❏ Drying is usually a waste of time and is always a potential source of contamination. So,
unless you instructed to do so, drying is not necessary.
❏ Rinsing with acetone may help for drying and removing grease films.
F. Evaporating Liquids
❏ Some procedures will tell you to reduce volumes
of your samples containing nonvolatile solutes by
evaporation. This is to evaporate some unwanted
substances like:
❏ chlorides and nitrates can be evaporated by adding sulfuric
acid
❏ nitrate ion and nitrogen oxides by adding urea
❏ Ammonium chloride by adding conc. Nitric acid
❏ Place the sample in an evaporating dish and heat
over in a water bath
❏ If it is a test tube, you may use beaker filled with
water.
G. Removal of Supernatant Liquid
❏ Supernatant Liquid is the resulting liquid after a mixture of liquid and solid has been left
to settle out or centrifuged to separate the two
❏ you will have two layers solid on the bottom and supernatant on the top
❏ medical definition: referred to as centrifugate
Centrifugate
❏ To remove the supernatant, carefully pour or pipette the
solution away from the solid. If the solid becomes re-suspended
as the supernatant is removed, centrifuge the sample again.
❏ clear centrifugate is usually transferred to another test tube
H. Washing Precipitates
❏ The purpose of washing precipitates is to ensure that all interfering ions will be washed
away from the sample.
❏ Technique is to add just enough distilled water (as water may dissolved some
precipitates), mixed with stirring rod thoroughly so to dissolve all interfering ions.
❏ Then centrifuge and discard washings.
Centrifuge
Centrifuge is a device by which a centrifugal force produced by an electric motor
speeds up the rate of setting of a precipitate.
