Common Analytical Techniques

Question 1

Composition

Answer 1

proportion of different constituents or species that comprise a population or mixture, describing the general makeup of a stream

Question 2

Concentration

Answer 2

refers to the relative abundance of a specific constituent or species in a mixture (without any reference to other species present in the mixture).

Question 3

Separation techniques

Answer 3

isolate analytes

Question 4

Qualitative techniques

Answer 4

to identify analytes

Question 5

Quantitative techniques

Answer 5

to quantify analyte concentration

Question 6

Titrimetry

Answer 6

-used to determine the concentration of an analyte
* Start with a certain volume of a chemical reagent, called
the titrant, typically a solution of known composition.
* Allow the titrant to react with a sample of the analyte,
called the titrand, of known concentration and volume.
* Add an indicator to detect end‐point of neutralization.
* The volume of titrant that reacted with the analyte, at the
point of neutralization, is called the titration volume.

Question 7

Acid–Base Titrations

Answer 7

are used in the analysis of: biodiesel fuel, in the Kjeldahl method (to measure nitrogen in organic wastes), acid value (to determine free fatty acids), saponification value (to determine chain lengths of fatty acids), amine value (to determine amine content), hydroxyl value (to determine hydroxyl group content)

Question 8

Redox Titrations

Answer 8

are used for the Winkler test for dissolved oxygen, to determine Vitamin C content, in Benedict’s reagent (for glucose concentration in urine), to determine Bromine and Iodine numbers, etc.

Question 9

Karl Fischer Titration

Answer 9

is a special method used commonly to measure trace amounts of water in organic liquids (such as crude oils)

Question 10

The precipitation method (gravimetric analytical methods)

Answer 10

is used for the amount of a solute, which is converted into an insoluble precipitant by adding an excess amount of a reagent, followed by collecting, drying and weighing the precipitant.

Question 11

Gravimetric Analytical Methods

Answer 11

These methods are for the quantitative determination of an analyte based on its mass.

Question 12

The Volatilization method (gravimetric analytical methods)

Answer 12

involves separation of the analyte by heating or chemically decomposing the sample at a suitable temperature.

Question 13

Do gravimetric analytical methods need calibration?

Answer 13

A gravimetric analysis provides precise results and does not require any calibration with standards. These are based typically on direct
mass (and/or volume) measurements. Hence, such
methods are used for calibrating other techniques and
instruments.

Question 14

Chromatography

Answer 14

is a physical method of separation that distributes components between two phases, namely, a stationary phase and a mobile phase

Question 15

Chromatograph

Answer 15

equipment for separating the species

Question 16

Chromatogram

Answer 16

visual output from the instrument

Question 17

Analyte or eluite

Answer 17

substance to be separated

Question 18

Eluate or effluent

Answer 18

mobile phase leaving the column

Question 19

Eluent

Answer 19

solvent that carries the analyte

Question 20

Immobilized phase

Answer 20

coats the adsorbing particles in a packed bed or the inner wall of the column or tube

Question 21

Mobile phase

Answer 21

consists of the analyte and the eluent.

Question 22

Retention time

Answer 22

time it takes for an analyte to pass through the system

Question 23

Column chromatography

Answer 23

packed column

Question 24

Planar chromatography

Answer 24

classified into 2D, Paper and Thin layer chromatography (high school experiment)

Question 25

Displacement chromatography

Answer 25

in which a molecule with higher affinity displaces all molecules with lesser affinities

Question 26

High Performance Liquid Chromatography (HPLC)

Answer 26

Liquid chromatography with small adsorbing particles and high pressure.
HPLC has two sub classes:
-Normal Phase Liquid Chromatography (NPLC)
-Reversed Phase Liquid Chromatography (RPLC).

Question 27

Supercritical Fluid Chromatography (SFC)

Answer 27

use of a supercritical fluid (at T>Tc, P >Pc) as the mobile phase.

Question 28

Separation techniques chromatography methods

Answer 28

• Many specialized techniques:
  o Ion exchange chromatography (IEC)
  o Size exclusion chromatography (SEC)
  o Expanded bed adsorption chromatography
  o Reversed phase chromatography
  o Hydrophobic interaction chromatography
  o Fast protein liquid chromatography, etc.

Question 29

Spectroscopy

Answer 29

deals with the interaction between matter and electro‐magnetic radiation energy as a function of wavelength or frequency
-acquired data can be represented by an emission spectrum, which is a plot of the response as a function of wavelength or frequency

Question 30

How is spectroscopy classified

Answer 30

Spectroscopy can be classified by the wavelength or frequency of radiative energy involved in the interaction, such as microwave, infrared, visible, ultraviolet, x‐ray, and gamma‐ray, etc.

Question 31

Atomic absorption spectroscopy (AAS)

Answer 31

is a common technique, which involves visible light radiation, for mostly 1st & 2nd group of elements

Question 32

Fourier‐transform infrared spectroscopy (FTIR)

Answer 32

measures infrared light absorption by a sample to determine its
chemical composition

Question 33

X‐ray diffraction spectroscopy (XRD)

Answer 33

is a non‐destructive technique (for solids) that uses X‐rays

Question 34

Spectrophotometer

Answer 34

measures the intensity of a beam as a function of its colour (i.e., frequency or wavelength)
-It deals with visible light, near‐ultraviolet, and near‐
infrared wavelengths.
-Spectrophotometers require calibration with a
reference substance(s)

Question 35

Sequence of activities in a Spectrophotometer

Answer 35

-The light is shone on the sample and focused into a slit,
-The transmitted light is refracted with the reflection grating,
-The resulting light strikes the photodetector and compared
with the standard,
- %transmission reading is converted into concentration

Question 36

Electro‐analytical methods

Answer 36

several techniques to study an analyte by measuring the potential (in Volts) and/or current (in Amperes) in an electrochemical cell
containing the analyte.

Question 37

Potentiometry

Answer 37

in which the difference in electrode potentials is measured (Electro‐analytical)

Question 38

Coulometry

Answer 38

in which the cell’s current is measured over time (Electro‐analytical)

Question 39

Voltammetry

Answer 39

in which the cell’s current is measured while the cell’s potential is altered
-Chemically modified electrodes are employed for the analysis of organic and inorganic samples

Question 40

Potentiometry - details

Answer 40

-One electrode is the reference electrode with a constant potential, while the other is an indicator electrode, whose potential changes with the sample composition
-The potential difference between the two electrodes provides information about the sample composition
-The time for establishing equilibrium with the solution
can affect the measurement sensitivity and accuracy.
-Platinum is often used, although electrodes made from other metals have also been used

Question 41

Coulometry - details

Answer 41

-uses applied current or potential to completely convert an analyte from one oxidation state to another
-The electrical current is measured directly or indirectly
to determine the number of electrons.