INSTRUMENTAL METHODS OF ANALYSIS

SPECTROSCOPY

Spectroscopy deals with the transitions induced in a chemical species by its interactions with photos of
the electromagnetic radiations.

Spectroscopic methods are generally used to measure the energy difference between various molecular
energy levels and to determine the atomic and molecular structures.

ELECTROMAGNETIC RADIATION

Electromagnetic radiation is a form of energy that is transmitted through space at enormous velocities.
An electromagnetic radiation is said to have a dual nature, exhibiting both wave and particle nature. This
dual nature is useful for the quantitative description of many phenomenon.

PROPERTIES OF ELECTROMAGNETIC RADIATION

An electromagnetic radiation has an alternating electrical and associated magnetic field in space. Thus it
has electric component and magnetic component which oscillate in planes perpendicular to each other.

An electromagnetic wave is characterized by the following parameters

(i). Wavelength: It is the distance between two successive maxima on an electromagnetic wave. It is
denoted by ‘λ’. The units of wavelength are m, cm, mm, μm, nm and Å.

The beam carrying radiation of only one discrete wavelength is said to be monochromatic, otherwise
called polychromatic.

(ii). Frequency: The number of wavelength units passing through a given point in unit time is called the
frequency of radiation. It is denoted by ‘ν’.
It is generally expressed in cycles per second or Hz.

(iii). Wavenumber: It is defined as the number of waves per centimeter in vacuum. It is denoted by ‘ῡ’.
1
ῡ=
𝜆
(iv). Velocity: the product of wavelength and frequency is equal to the velocity of the wave in the medium.
∴𝑣= 𝜈 × 𝜆
Units of velocity is cm.s-1 or m.s-1

PARTICLE PROPERTIES OF ELECTROMAGNETIC RADIATION

Electromagnetic radiation consists of a stream of discrete packets of pure energy, called photons or
quanta.

The energy of photon is proportional to the frequency of radiation and is given by

𝐸 = ℎ. 𝜈
E is the energy of photon, ν is the frequency of electromagnetic radiation and h is the Planck’s constant.

RELATIONSHIP BETWEEN WAVELENGTH AND PARTICLE PROPERTIES OF ELECTROMAGNETIC RADIATION

The relationship between wavelength and particle properties of electromagnetic radiation is given by
ℎ. 𝑐
𝐸 = ℎ. 𝜈 = ℎ. 𝑐. ῡ =
𝜆
ELECTROMAGNETIC SPECTRUM

Electromagnetic waves can be classified and arranged according to their various wavelengths or
frequencies; this classification is known as the electromagnetic spectrum. The following table shows us
this spectrum, which consists of all the types of electromagnetic radiation that exist in our universe.
Light that we can see with our eyes—makes up only a small fraction of the different types of radiation
that exist. Radio waves have the longest wavelength, and gamma rays have the shortest wavelength.

DISPERSION OF LIGHT

The dispersion of light is the phenomenon of splitting of a beam of white light into its seven constituent
colours when passed through a transparent medium. A beam of sunlight through a glass prism. The glass
prism split the light into a band of seven colours, known as spectrum.

Thus the spectrum is a band of seven colours which is obtained by splitting of white light by a glass prism.
The order of colours from the lower end of spectrum is violet (V), indigo (I), blue (B), green (G), yellow (Y),
orange (O), and red (R). The sequence of the 7 colours so obtained in a spectrum can be remembered by
using the acronym ‘VIBGYOR’.
INTERACTION OF ELECTROMAGNETIC RADIATION WITH MATTER

When electromagnetic radiation passes through matter, a variety of phenomenon may occur.

(i). If the photons of radiation possess the appropriate energies, they may be absorbed by the matter and
result in electronic transitions, vibrational or rotational changes or combination of all. After absorption,
atoms or molecules excite and quickly give out energy in the form of heat or electromagnetic radiation.

(ii). The energy may be not be absorbed completely, but may be scattered or reflected.

(iii). Electromagnetic radiation may bring a change in orientation or polarization.

(iv). In some cases they may brought about the phenomenon of fluorescence or phosphorescence.

ABSORPTION AND EMISSION SPECTRA

Consider two molecular energy levels having energies E1 and E2 respectively. If a photon of frequency ν
falls on the molecule in the ground state and its energy hν is exactly equal to the difference of energies of
the two levels (∆E = E2 - E1).

The molecule undergoes a transition from the lower energy level to the higher energy level with the
absorption of energy. The spectrum thus obtained is called absorption spectrum.

If the molecule falls from the excited state to the ground state with the emission of a photon of energy
hν, the spectrum obtained is called emission spectrum.

THEORIES OF ABSORPTION

When light is incident upon a homogeneous medium, a part of the light is reflected, a part light is absorbed
by the medium and the remaining is allowed to transmit as such.

If 𝐼0 denotes the incident light, 𝐼𝑟 is the reflected light, 𝐼𝑎 is the absorbed light and 𝐼𝑡 is the transmitted
light. Then

𝐼0 = 𝐼𝑟 + 𝐼𝑎 + 𝐼𝑡
If a comparison cell is used, then intensity of reflected light becomes very small and can be eliminated.
Hence,

𝐼0 = 𝐼𝑎 + 𝐼𝑡
LAMBERT’S LAW

“When a beam of light is allowed to pass through a transparent medium, the rate of decrease of intensity
with the thickness of medium is directly proportional to the intensity of the incident light”.

Mathematically,
𝑑𝐼
− ∝𝐼
𝑑𝑡
𝑑𝐼
⇒− = 𝑘𝐼
𝑑𝑡
Where I denotes the intensity of incident wavelength λ, t denotes the thickness of the medium and k
denotes the proportionality constant. On integrating the above equation in between the limits I = I0 to It
and t = 0 to t,
𝐼0
𝑙𝑛 = 𝑘𝑡
𝐼𝑡

⇒ 𝐼𝑡 = 𝐼0 𝑒 −𝑘𝑡
Where 𝐼0 denotes the intensity of the incident light, 𝐼𝑡 denotes the intensity of the transmitted light and
k is a constant which depends upon the wavelength and absorbing medium used.

∴ 𝐼𝑡 = 𝐼0 10−0.4343𝑘𝑡
Where K = k/2.303, known as absorption coefficient.

Absorption coefficient is defined as “It is the reciprocal of thickness which is required to reduce the light
to 1 / 10 of its intensity”.
𝐼𝑡 1
∴ = 0.1 = 10−𝑘𝑡 ⇒ 𝐾𝑡 = 1 𝑜𝑟 𝐾 ∝
𝐼0 𝑡
𝐼0 𝐼𝑡
The ratio is termed as transmittance, T and the ratio 𝑙𝑜𝑔 is termed as absorbance, A of the medium.
𝐼𝑡 𝐼0

Hence
𝐼0
𝐴 = 𝑙𝑜𝑔
𝐼𝑡
BEER’S LAW

“The intensity of a beam of monochromatic light decreases exponentially with the increase in
concentration of the absorbing substance arithmetically”.
′𝑐
𝐼𝑡 = 𝐼0 𝑒 −𝑘
′𝑐 ′𝑐
= 𝐼0 10−0.4343 𝑘 = 𝐼0 10−𝐾
Where 𝑘 ′ and 𝐾 ′ are constants and c is the concentration of the absorbing substance. On combining
Lambert’s law and beer’s law, we get
 𝐼𝑡 = 𝐼0 10−𝑎𝑐𝑡
𝐼0
𝑙𝑜𝑔 =𝑎𝑐𝑡
𝐼𝑡
The above equation is termed as mathematical statement for Beer – lambert’s law. This is also the
fundamental equation for Spectrophotometry and colorimetry.

The value of ‘a’ depends on the unit of concentration. If ‘c’ is expressed in molarity and t in centimeters,
then ‘a’ is replaced by the symbol ‘ε’ and is termed as molar absorption coefficient or molar absorptivity.

The relationship between the absorbance A, the transmittance T and molar absorption coefficient ‘ε’
𝐼0 1
𝐴 = 𝜀 𝑐 𝑡 = 𝑙𝑜𝑔 = 𝑙𝑜𝑔 = − log 𝑇
𝐼𝑡 𝑇
LIMITATIONS OF BEER’S LAW

Beer’s law indicates that absorptivity is constant and does not depend upon concentration, path length
and intensity if incident radiation. The law gives no idea about the effect of temperature, nature of the
solvent or the wavelength.

DEVIATIONS FROM BEER’S LAW

According to beer’s law, a straight line passing through origin is obtained, when a graph is plotted between
absorbance A and concentration. But there is always a deviation from the linear relationship between
absorbance and concentration.

The deviations from the beer’s law may be due to

interaction of the solute molecules with each other or
with the solvent or may be due to internal factors.

a). Chemical deviations: the deviation from beer’s law

may change with concentration due hydrolysis,
association, polymerization, ionization, hydrogen
bonding etc.

b). At higher concentrations, the substance absorbs

more readily that that expected on the basis of beer’s
law. The real limitation of the law is that beer’s law is
successful in describing the absorption behavior of dilute solutions only.

c). Instrumental deviations: deviation from beer’s law is observed if polychromatic radiations are
used. When Illumination is not monochromatic, negative deviations will occur.
UV – VISIBLE SPECTROSCOPY

Ultraviolet-visible spectroscopy is considered an important tool in analytical chemistry. In fact, this is one
of the most commonly used techniques in clinical as well as chemical laboratories. This tool is used for the
qualitative analysis and identification of chemicals. However, its main use is for the quantitative
determination of different organic and inorganic compounds in solution.

Basically, spectroscopy is related to the interaction of light with matter. As light is absorbed by matter,
the result is an increase in the energy content of the atoms or molecules. The absorption of visible light
or ultraviolet light by a chemical compound will produce a distinct spectrum.

When ultraviolet radiations are absorbed, this results in the excitation of the electrons from the ground
state towards a higher energy state. The theory revolving around this concept states that the energy from
the absorbed ultraviolet radiation is actually equal to the energy difference between the higher energy
state and the ground state.

The Basic Principle of UV Spectroscopy:

UV spectrophotometer principle follows the Beer-Lambert Law. This law states that whenever a beam of
monochromatic light is passed through a solution with an absorbing substance, the decreasing rate of the
radiation intensity along with the thickness of the absorbing solution is actually proportional to the
concentration of the solution and the incident radiation.

Basing from the Beer-Lambert law, it has been established that the greater the number of the molecules
that are capable of absorbing light at a certain wavelength, the greater the extent of the absorption of
light and this is given by

𝐴=𝜀𝑐𝑡
Where A is absorbance, c is concentration of analyte, t is path length and ε is molar absorptivity or molar
extinction coefficient.

INSTRUMENTATION

The components of UV – Visible spectrophotometer are

a). Source

b). Monochromator

c). Sample holder

d). Detector

e). Amplifier and Readout.

LIGHT SOURCE

The following are the requirements of a radiation source.

It must be stable. It must of sufficient intensity for transmitted radiation to be detected and it must be
continuous in entire wavelength.

Commonly used sources are tungsten lamp (for visible region) and Hydrogen or deuterium lamp (for UV
region).

MONOCHROMATOR

The function of the monochromator is to break the polychromatic radiation into component wavelengths
or bands of wavelengths. The essential components of a monochromator are Entrance slit, Collimating
device, a prism or grating, a focusing lens and an exit slit.

SAMPLE HOLDER

Samples to be studied in UV – Visible spectroscopy are usually put in cells called cuvettes. These cuvettes
are made up of glass (for Visible) or Quartz (for UV). These cuvettes are available in path lengths ranging
from 1mm to 10cm.

DETECTOR

After the light passed through the sample, the transmitted light has to be detected and measured. These
detectors take the energy from the light and convert into an electrical signal that can be amplified and
recorded. These detectors work on the principle of photoelectric effect.

Commonly used detectors are photocells, phototubes and photomultiplier tubes.

AMPLIFIER AND READOUT

The electrical signal detected by the detector are translated into a form that is easy to interpret. This can
be done by amplifiers, ammeters, potentiometers and photometric recorders.

APPLICATIONS

1. It is a technique that allows the determination of concentration of substances and therefore

enabling to study the rate of reactions and to determine the rate equation. It is extensively used
in quantitative analysis of all the species that absorb UV and Visible radiations.
2. In clinical chemistry, it is extensively used to study the enzyme kinetics.
3. It is used in dissolution testing of tablets and products in the pharmaceutical industry.
4. It is used in the quantification of DNA and Proteins / Enzymes activity in fields of genetics and
biochemistry.
5. Used in the quality control in development and production of dyes, inks and paint industry.
6. Used in quantification of organic materials and heavy metals in fresh and agricultural waters in
environmental and agricultural fields.
INFRA RED SPCTROSCOPY

Infrared spectroscopy is a powerful technique which uses electromagnetic radiations in the infrared
region for the determination and identification of molecular structure as well as having various
quantitative applications in analytical chemistry.

INFRARED REGIONS

Infrared spectroscopy can be rationalized as the spectroscopy that deals with electromagnetic radiation
of infrared frequency. There are three well defined infrared regions; each of them has the potential to
provide different information

Near infrared (12820-4000 cm-1): Poor in specific absorptions, consists of overtones and combination
bands resulting from vibrations in the mid-infrared region of the spectrum.

Mid-infrared (4000-400 cm-1): Provides structural information for most organic molecules.

Far Infrared (400-33 cm-1): Has been less investigated than the other two regions; however, it has been
used with inorganic molecules.

The low energies, typically encountered within the infrared region, are not sufficient to cause electronic
transitions; however, they are large enough to cause changes in the frequency and amplitude of molecular
vibrations.

PRINCIPLE

When the energy in the infrared region is absorbed by the matter, it causes a vibration between the atoms
of the molecules when the frequency of the applied radiation is equal to the natural frequency of the
molecule. Then the absorption of IR radiation takes place. The absorption of IR radiations will bring a
change in the dipole moment of the molecule. This increase the amplitude and frequency of vibrations.
The absorbance value is recorded.

Different functional groups absorb characteristic frequencies of IR radiation. Hence it gives characteristic
peak value. Therefore IR spectrum of a chemical substance is a finger print of a molecule for its
identification.

The IR spectrum is a graph plotted by taking wavenumber on x-axis and corresponding absorbance value
on y – axis.

INSTRUMENTATION

The basic components of an IR spectrometer include

Source, monochromator, sample holder, detector and readout.

SOURCE

The common IR sources used are

Nernst glower: It employs a hollow rod of zirconium and yttrium heated up to 1500°C, emit the IR
radiations in the range 0.4 to 20 μm.

Globar source: It consists a silicon carbide rod heated at 1200°C, emit radiation in the range 1 – 40 μm.

Globar source is more stable than the Nernst glower.

MONOCHROMATOR

As the sample in IR spectroscopy absorbs in certain frequencies, it is necessary to select desired

frequencies from the radiation source. This can be achieved by two monochromators namely prism
monochromator and grating monochromator.

SAMPLE HOLDER

Solids, liquids and gases can be characterized using this technique. Gases are analyzed by tubes made up
of glass. Liquids are analyzed as films or solutions in NaCl or KCl tubes. Solids are analyzed as KBr pressed
discs or as suspensions.

DETECTOR

Two types of detectors are used in Infra-red spectrophotometers.

a). Thermal detectors: Thermocouple or bolometer

b). Photo conducting detectors or Pyroelectric detectors

AMPLIFIER AND READOUT

Radiation detectors generate electronic signals which are proportional to the transmitted light. These
signals are transformed to IR spectra using a personal computer capable of handling Fourier
transformations.

APPLICATIONS

1. Used in the identification of functional group and structural elucidation of an organic compound.
2. IR spectroscopy is used to establish whether a given sample of an organic substance is identical
with another or not.
3. Progress of chemical reaction can be determined by examining the small portion of the reaction
mixture withdrawn from time to time.
4. IR spectrum of the test sample to be determined is compared with the standard compound. If any
additional peaks are observed in the IR spectrum, then it is due to impurities present in the
compound.
5. The quantity of the substance can be determined either in pure form or as a mixure of two or
more compounds.
NUCLEAR MAGNEITC RESONANCE SPECTROSCOPY

PRINCIPLE

NMR phenomenon is based on the fact that nuclei of atoms having magnetic properties can be utilized to
yield chemical information. Quantum mechanically, the protons, electrons and neutrons in a nucleus have
spin. In some atoms (like 12C, 16O) these spins are paired and cancel each other. However, in many atoms
like (1H, 13C, 31P, 9F) the nucleus does possess an overall spin and behave like a tiny magnet.

If an external magnetic field is applied, the tiny magnets are either aligned in the direction or in opposite
direction of the magnetic field. The energy difference between the two orientations is small and depends
on the strength of the applied magnetic field. When an external electromagnetic radiation in the radio
frequency region is applied, causes the spin to flip and the nuclei are said to be in resonance. The tiny
magnets go to the higher energy state and comes back to the ground state emitting the energy in radio
frequency region. The emitted radiation is captured and the spectrum is recorded.

INSTRUMENTATION

The basic instrumentation of NMR spectrometer include the following components.

a). Magnet having strong magnetic field

b). RF generator

c). Sweep Generator

d). Detector

e). Readout

Sample holder: Glass tube with 8.5 cm long, 0.3 cm in diameter.

Permanent Magnet: It provides homogeneous magnetic field at 60-100 MHz

Magnetic coils: These coils induce magnetic field when current flows through them.

Sweep Generator: To produce the equal amount of magnetic field pass through the sample.

Radio Frequency Transmitter: A radio transmitter coil transmitter that produces a short powerful pulse
of radio waves.

Radio frequency receiver: A radio receiver coil that detects radio frequencies emitted as nuclei relax to a
lower energy level.

Read Out: A computer that analyses and record the data.

APPLICATIONS

NMR spectroscopy is the use of the NMR phenomenon to study physical, chemical and biological
properties of matter.

 It is an analytical chemistry technique used in quality control.

 It is used in research for determining the content and purity of a sample as well as its molecular
structure. For example, NMR can quantitatively analyze mixtures containing known compounds.

 NMR spectroscopy is routinely used by chemists to study chemical structure using simple one-
dimensional techniques. Two-dimensional techniques are used to determine the structure of
more complicated molecules.

 These techniques are replacing x-ray crystallography for the determination of protein structure.

 Time domain NMR spectroscopy techniques are used to probe molecular dynamics in solution.

 Solid state NMR spectroscopy is used to determine the molecular structure of solids.

 Other scientists have developed NMR methods-of measuring diffusion coefficients

MAGNETIC RESONANCE IMAGING (MRI)

Magnetic Resonance Imaging (MRI) is one way for healthcare professionals to look inside your body and
see what is going on inside it without having to cut open your body. MRIs produce far more detailed
images of the structure of a patient’s blood vessels, nerves, bones, and organs.

Working of MRI

Human body is pretty much entirely made of water. Blood vessels, lymph nodes, and even solid bones are
soaked with water molecules, each of which contains two hydrogen atoms and an oxygen atom. This can
be visualized as a tiny magnet.

The water in the tissues absorb the electromagnetic radiation coming in their way and emit the radiations.
An MRI is just a device that first excites water molecules into releasing waves, and then records the
locations of those emitted waves with high accuracy.
Because different places in the body contain different amounts of water, MRI detects the electromagnetic
fields of the atoms in water molecules and uses this to determine differences in the density and shape of
tissues throughout the body.

Some bodily processes actually change tissues in ways that are noticeable on an MRI. For example, when
tissues stretch or swell, the distribution of protons in that part of the body can change enough that a
detectable change will occur in the MRI signal coming from that part of the body.

Hence, MRI is extensively used by medical professionals to detect the abnormalities present in the body
and tissues in the human body.
BASICS OF CHROMATOGRAPHY

Chromatography is relatively a new technique which was first invented by M. Tswett, a botanist in 1906
in Warsaw. He was successful in the separation of chlorophyll, xanthophyll and several other colored
substances by percolating vegetable extracts through a column of calcium carbonate.

Tswett termed this system of colored bands as the chromatogram and the method as chromatography
after the Greek words Chroma and graphos meaning “color” and “writing” respectively. However, in the
majority of chromatographic procedures no colored products are formed and the term is a misnomer.

Chromatography is one of the most important single analytical technique used today for separation of
compounds.

DEFINITION OF CHROMATOGRAPHY

Chromatography may be defined as a method of separating a mixture of components into individual

components through equilibrium distribution between two phases.

BASIC CHROMATOGRAPHIC TERMINOLOGY

Chromatograph: Instrument employed for a chromatography.

Stationary phase: Phase that stays in place inside the column. Can be a particular solid or gel-based
packing (LC) or a highly viscous liquid coated on the inside of the column (GC).

Mobile phase: Solvent moving through the column, either a liquid in LC or gas in GC.

Eluent: Fluid entering a column.

Eluate: Fluid exiting the column.

Elution: The process of passing the mobile phase through the column.

Chromatogram: Graph showing detector response as a function of a time.

Essentially, the technique of chromatography is based on the differences in the rate at which the
components of a mixture move through a stationary phase under the influence of some solvent or gas
called moving phase.

The chromatography method of separation, in general, involves the following

1. Adsorption or retention of a substance in the stationery phase

2. Separation of the adsorbed substances by the mobile phase.

3. Recovery of the separated substances by a continuous flow of the mobile phase, the method being
called elution.

4. Qualitative and quantities analysis of the eluted substances.

CLASSIFICATION OF CHROMATOGRAPHIC TECHNIQUES

In all types of chromatography, separation of components of a mixture results either by adsorption or

partition for the column material. Binding of compound to the surface of solid phase take place in
adsorption while in case of partition, a compound gets distributed into two liquid phases. The
chromatographic methods are classified as;

PRINCIPLES INVOLVED IN CHROMATOGRAPHY:

The basic principles involved in chromatographic separation involve adsorption and partition.

Adsorption is defined as a process in which the solid or liquid or gas particles will be attracted retained
on a surface and will displace from the surface when an external force is applied.

Partition is the phenomenon observed when a solute distributes itself between two completely
immiscible or partially miscible liquids/ solvents, based on the nature of the component and the two
liquids/ solvents the solute will completely extracted into one of the solvents.

Other principles in the chromatographic processes include ion exchange, exclusion.

APPLICATIONS OF CHROMATOGRAPHY

 Chromatography plays an important role in many pharmaceutical, chemical and food industries.
 Environmental testing laboratories generally use this technique to identify very small quantities
of contaminants in waste oil, and pesticides.
 The Environmental Protection Agency makes the method of chromatography to test drinking
water and to monitor air quality.
 Pharmaceutical industries use this method both to prepare huge quantities of extremely pure
materials, and also to analyze the purified compounds for trace contaminants.
 These separation techniques like chromatography gain importance in different kinds of
companies, different departments like Fuel Industry, biotechnology, biochemical processes, and
forensic science.
 Chromatography is used for quality analyses and checker in the food industry, by identifying and
separating, analyzing additives, vitamins, preservatives, proteins, and amino acids.
 Chromatography like HPLC is used in DNA fingerprinting and bioinformatics.
In the present topic, ion-exchange chromatography is specifically focused in separation of ions from
water.

ION EXCHANGE CHROMATOGRAPHY

Ion exchange chromatography definition (or ion chromatography) is a process that allows the separation
of ions and polar molecules based on their affinity to the ion exchanger. It can be used for almost any kind
of charged molecule including large proteins, small nucleotides and amino acids, water.

Principle:

In Ion Exchange chromatography, exchange of ions is the basic principle in this type of Chromatography.
In this process two types of exchangers i.e., cationic and anionic exchangers can be used.

Cationic exchangers possess negatively charged group, and these will attract positively charged cations.
These exchangers are also called “Acidic ion exchange” materials, because their negative charges result
from the ionization of acidic group.

Anionic exchangers have positively charged groups that will attract negatively charged anions. These are
also called “Basic ion exchange” materials.
SOFTENING OF HARD WATER

This requires the removal of cations as well as anions. For their removal, the water is first passed through
acidic cation exchanger when the metallic cations (Na+, Ca2+, Mg2+ etc.,) are exchanged by hydrogen ions.
The water obtained from cation exchanger is then passed through a basic anion exchanger when the
anions commonly present in water (Cl-, NO2-, SO42- etc.) are exchanged by hydroxyl ions of the exchanger.
The hydrogen ions and the hydroxyl ions which pass into solution in exchange for cations and anions
respectively combine to form unionized water. Generally sulphonic acid resin is employed as the cation
exchanger while a strong basic resin containing quaternary ammonium groups is employed as the anion
exchanger.

Waste water treatment

Wastewater is a dynamic system containing organic and inorganic compounds, dissolved compounds, and
insoluble substances. Moreover, the composition of samples can change dramatically during or after the
sampling.

Therefore, analyses require available, reliable, and fully-automatic methods for simultaneous
determinations of several analytes.

Ion chromatography offers several advantages over the classic wet methods for determinations of
inorganic and organic ions in wastewater, such as:

Short time of analysis (≈10–15 min);

High sensitivity and selectivity in samples with complex matrices (e.g., if the ratio of Na+:NH4+ or Cl−:NO2−
is 10,000:1);

Simple sample pre-treatment (usually filtration with a filter with a 0.45-µm pore of is enough); possibilities
of simultaneous separation and determination of anions and cations;

Species analysis (e.g., NO2−/NO3−/NH4+ or Cr3+/Cr6+); use of different detection modes (e.g., conductivity,
UV-VIS, amperometry); and

Safe, cheap, and environmentally friendly chemicals (e.g., diluted water solution of Na2CO3/NaHCO3 or
HCl, HNO3).