ANALYTICAL CHEMISTRY Flashcards
Type of analysis according to technique
Classical
instrumental
combined/coupled
Macro
> 100mg and > 100microLitre
Semi micro
10-100 mg
50-100 microL
micro
1-10 mg
<50 micro L
Ultra micro
<1 mg
Types of analysis according to extent
proximate
complete
ultimate
Technique used to measure weight of pure analyte or compound of known stoichiometry
Gravimetry
Technique used to measure the volume of standard reagent solution reacting with the analyte
Titrimetry
Technique used to measure wavelength and intensity of radation emitted or absorbed by the analyte
Atomic and molecular spectroscopy
Measures mass of analyte or fragments of it
mass spectrometry
measures various physico-chemical properties of separated analytes
Chromatography and electrophoresis
Measures electrical properties of the analytenin solution
electrochemical analysis
component of interest in the sample
analyte
collection of all the components in the sample
matrix
set of written instructions on how to apply a method to a particular sample
procedure
set of written guidelines for the analysis of a sample specified by an agency
protocol
process of collecting a small amount of a material whose composition represents the bulk of the material being sampled
sampling
portion of a solution subjected to analysis
aliquot
sample that contains all the components of the matrix except the analyte
blank
experimental measurement that is proportional to analyte concn
signal
Chemicals that do not have established standards for purity levels or for products with <90% purity
Technical grade
high purity chemicals for which no established specs exist. They are often solutions or dilutions of ACS Reagent materials
Reagent
Chemicals manufactured under current Good Manufacturing Practices. Meets the requirements of the US Parmacopeia
USP
Chemicals suitable for laboratory and general use.
AR (Analytical Reagent)
Reagents that meets the requirements of the american chemical society committe on analytical reagent
AR (ACS) reagent
Chemicals of this grade meets the specs of ACS. These are analytical regents found in most lab
ACS
Analytical reagent of exceptional purity that is soecially manufactured for standardizing volumetric solutions and preparing reference standards
Primary Standard
Excellent source for primary standards
National Institute of Standards and Technology
Chemicals that have been prepared for specific applications
Special Purpose
Middle result in a set of data that has been arranged in numerical order
Median
Indication of the reproducibility (repeatability) of a measurement. i
Precision
Measure of the agreement between an experimental result and an expected or true value
Accuracy
This type of error causes data to be more scattered more or less symmetrically around the mean
Random or indeterminate error
Error that causes rhe mean of a set of data to differ from the accepted values
Systematic or determinate
Errors that are often large and may cause a result to be either high or low
Gross errors
Random errors can be minimized by
Increasing number of measurements
Signal is a mass of precipitate
Precipitation gravimetry
Signal is mass of an electrodeposit on the cathode or anode in an electrochemical cell
Electrogravimetry
Siganl is a loss of volatile species
Volatlization Gravimetry
Mass of a sample is measured overntime as temp changes
Thermogravimetry
Occurs when the precipitant is generated in situ by chemical reaction
Homogeneous precipitation
According to this relation, particle size is inversely proportional to relative supersaturation
Von Weimarn ratio
To promote particle growth instead of further nucleation, Von weimarn ratio must be
kept low
Solids formed by precipitation that consist of tiny particles with diamteres of 10^-7 to 10^-4 cm
Colliodal suspensions
Composed of particles with diameters larger than 10^-4 cm
Crystalline suspensions
Involves dissolution of small particles and reprecipitation on larger ones resulting in particle growth and better particle characteristic (Ostwald Ripening)
Digestion
One form of contamination of gravimetric precipitates
Coprecipitation
Interfering ipn occupies a lattice site in the precipitate
Inclusion
Impurity is trapped within the precipitate as it forms
Occlusion
Impurity adsorbs to the surface of a precipitate
Surface Adsorption
Substances that taste sour, turns blue litmus red and corrodes metals producing H2 gas
Acids
Taste bitter, turns red litmus blue and have a slippery feel
Bases
Define an acid as a substance that produces H+ ions and base as a substance that producesbOH- ions
Svante Arrhenius
Acid- donate H+
Base- accept H+
Bronsted Lowry
Substances that act as both an acid and base
Amphoteric
Other amphoteric substances
Bicarbonate
Bisulfate
Biphosphate
An acid is any species that acts as an electron pair acceptior and a base as an electron pair donor
Lewis definition
Acids that yield more than one H3O+ ion
Polyprotic acids
Process where water reacts with itself
Auto-ionization
At 50C, the ion product constant of water is
5.5 x10^-14
Combination of a weak acid and its conjugate base ( or weak base and its conjugate acid)
buffer
During titration of a weak acid or base, maximum buffering capacity is achieved when titration is at
half neutralization or half equivalence point
Primary standards for standardization of acidic titrants
Sodium Carbonate (Na2CO3)
Sodium tetraborate
(Na2B4O7•10H2O)
Tris-(hydroxymethyl)aminomethane
For standardization of basic titrants
Benzoic acid
Potassium hydrogen diiodate
Potassium hydrogen phthalate
Measure of the acid neutralizing capacity of a water sample
Alkalinity
Bromocresol green endpoint
ph 4.5
Phenolphthalein endpoint
8.3
Direct titration
Warder method
Indirect titration
Winkler method
Ligand that attaches to a metal ion through more than one ligand atom
Multidentate or chelating ligand
Ability of multidentate ligands to form more stable metal complexes
chelate effect
Synthetic chelating agents
Aminocarboxylic acids
NTA, DCTA, DTPA and EDTA
Most widely used chelator
EDTA
EDTA binding sites
4 carboxylate groups, 2 amino acids
Form of EDTA that is commonly used
Disodium salt
Second ligand that is used to prevent the metal ion from precipitating as metal hydroxide that form at high pH
Auxiliary complexing agent
Widely used complexometric titration using a monodentate ligand
Liebig method
In this method, silver nitrate is added to a solution of alkali cyanide until the formation of the complex (dicyanoargentate) is complete
Liebig method
Soft water contains how much CaCO3
less than 60 ppm
Hard water contains ____ ppm CaCO3
270
Involve the use of AgNO3 as precipitating agent
Argentometric titrations
He described a method using ferric alum as indicator in titrations involving AgNO3
Jacob Volhard
In this method, K2CrO4 is used as an indicator with standard AgNO3
Mohr Method
In this method, DCF or dichlorofluorescein can be used an indicator
Fajans Method
Measure value minus true value
Absolute error
measured-true value divided by true value times 100
relative error,%
highest value - lowest value
range or spread
Species that contain one or more electron pair donor groups that tend to form bonds with metal ions
ligand
Cyclic complex consisting of metal ion and a reagent that contains two or more electron donor groups
Chelate
molecule that containe four pair of donor electrons located in such positions that they all can bond to a metal ion
tetradentatr chelating agent
Titrations based on the formation of precipitates with standard solution of silver nitrate
Argentometric titration
Equilibrium constant for the rxn between a metal ion and a complexing agent
conditional formation constant