LECTURE Reagent & Solution
REAGENT
• is a compound or mixture added to a system to cause a
chemical reaction
• It may be used to tell whether or not a specific chemical
substance is present by causing a reaction o occur with it.
• Analyte- a substance or sample being analysed
• Bulk System- a term for the material under investigation (group)
• Sample- representative portion of the bulk system
• The analytical laboratory technician analyzes these samples by
subjecting them to certain rigorous laboratory operations that
ultimately result in the identity or quantity of the analyte in
question
• The key is that the sample must possess all the characteristics
of the entire bulk system with respect to the analyte and the
analyte concentration in the system
• In other words, it must be a representative sample- it must truly
represent the bulk system
CHEMICALS
ANALYTICAL REAGENT (AR)- high standard of impurity
• Suitable for use in most analytic laboratory procedures
• the American Chemical Society established specifications for
AR grade chemicals
• Labels on reagents state the actual impurities for each chemical
lot or list the maximum allowable impurities
ULTRAPURE- extremely pure chemicals
• Ultrapure chemicals have been put through additional
purification steps for use in specific procedures such as
chromatography, atomic absorption, immunoassays, molecular
diagnostics, standardization, or other techniques that require
extremely pure chemicals.
USP(U.S. Pharmacopeial Convention)/NF(National Formulary)
• Chemicals that are used to manufacture drugs, may be
pure enough for use in most chemical procedures
CHEMICALLY PURE / PURE GRADE
• These designations indicate that the impurity limitations are not
stated and that preparation of these chemicals is not uniform
TECHNICAL/COMMERCIAL GRADE- hindi ginagamit sa
paggawa ng food
WATER SPECIFICATIONS
• DISTILLED WATER • DEIONIZED WATER • RO WATER
• ULTRAFILTERED WATER
• REAGENT GRADE WATER – CLRW/SRW
Distilled Water has been purified to remove almost all organic
materials, using distillation process in which water is boiled and
vaporized. Ex. Absolute, Nature’s Spring, Wilkins
Deionized Water or Tripple Distilled Water has some or all ions
removed, usually done from previously treated water, such as
prefiltered or distilled water. Ex. Used in preparation of agar
RO Water or Reverse osmosis is a process that uses pressure
to force water through a semipermeable membrane, producing
water that reflects a filtered product of the original water
Ultrafiltered Water - Produced from the process of
ultrafiltration, which removes particulate matter,
microorganisms, and any pyrogens or endotoxins. Fever Injusing
Substances
Reagent grade water can be obtained by initially filtering it
toremove particulate matter, followed by reverse osmosis,
deionization, and a 0.2 mm filter or more restrictive filtration
process.
Type I Water - Used for test methods requiring minimum
interference, such as trace metal, iron and enzyme analyses
Type II Water - is used for general laboratory applications and is
acceptable for most analytic requirements, including reagent,
quality control and standard preparation
Type III Water - is acceptable for glassware washing and filling
autoclaves, but not for analysis or reagent preparation
SOLUTIONS
• CONCENTRATION
• COLLIGATIVE PROPERTIES
Solution - is a homogenous mixture of two or more substances
with each substance retaining its own chemical identity
Solvent - is the component of solution that is present in the
greatest amount, the medium in which the other substances
present are dissolved
Solute is a component of a solution that is present in a lesser
amount relative to that of the solvent.
Dilution is the process in which more solvent is added to a
solution in order to lower its concentration
Dilute Solution - is one in which there is relatively little solute or
one which has been made to a lower solute concentration per
volume of solvent as when making a
dilution.
Concentrated Solution has a large quantity of solute in solution
Saturated Solution is a solution in which there is an excess of
undissolved solute particles
Supersaturated Solution has an even greater concentration
of undissolved solute particles than a saturated solution of the same
substance
LABORATORY Methods of Separation
Centrifugation - is a process in which centrifugal force is used
to separate solid matter from a liquid suspension. Ex. Benchtop,
Swinging Bucket Rotor, Fixhead Rotor they are all used to separate
serum particles (Urinalysis, Bloodbanking)
Decantation - is the process of pouring a liquid gently so as to
not disturb a solid in the bottom of the container. Sediments natitira.
(Urinalysis, Bloodbanking)
Filtration - can be used instead of centrifugation for the separation
of solids from liquids
•When the filter paper is placed inside the funnel, the solution
slowly drains through the filter paper within the funnel and into a
receiving vessel. The liquid that passes through the filter paper is
called the filtrate and residue naman yung naiiwan a filter paper.
Analytical separations - Used in Chemistry Lab only
•Modern-day chemical analysis can involve very complicated
material samples-complicated in the sense that there can be many
substances present in the sample
Interference
• Species other than the analyte that affect the final measurement
are called interferences, or interferents
• substances other than the analyte generate an instrumental
readout similar to the analyte, such that the interference adds to the
readout of the analyte
• an interference can also suppress the readout for the analyte (e.g.,
by reacting with the analyte)
Recrystallization is a purification technique for a solid, usually
organic. The separation is based on the solid’s solubility in a liquid
solvent
The key to the procedure is to use a minimum amount of solvent,
such that the solid will just dissolve at the elevated temperature
(usually the boiling point, if the solid is stable at that temperature).
While maintaining this elevated temperature, any impurity that has
not dissolved can be filtered out. The insoluble impurities are thus
removed.
Soluble impurities, however, are still present in the hot filtrate.
Theseare removed by cooling the filtrate. Cooling the filtrate causes
the solid being purified to crystallize
If the solubilities of the soluble impurities have not been exceeded
during the cooling step, they will stay dissolved and be separated
during the second filtering
Distillation is a method of purification of liquids contaminated with
either dissolved solids or miscible liquids
This method consist of boiling and evaporating the mixture
recondensation of the vapors in a condenser
The separation is based on the fact that the contaminants have
different boiling points than the liquid to be purified
The substances with lower boiling points are therefore separated
from substances that have high boiling points.
Simple distillation is used to separate a liquid from a solid if we
want to keep the liquid. Simple distillation works, First we
evaporate the liquid by heating, We then condense the vapour by
the cooling.
Fractional distillation allows us to separate two different liquids,
involves repeated evaporation-condensation steps before the
distillate is actually collected. These liquids must have different
boiling points
• These repeated steps occur in a fractionating column (tube) na
