<< Chapter < Page Chapter >> Page >

Columns

Different separation mechanisms were used based on different property of the stationary phase of the column. The major types include normal phase chromatography, reverse phase chromatography, ion exchange, size exclusion chromatography, and affinity chromatography.

Normal-phase chromatography

In this method the columns are packed with polar, inorganic particles and a nonpolar mobile phase is used to run through the stationary phase ( [link] ). Normal phase chromatography is mainly used for purification of crude samples, separation of very polar samples, or analytical separations by thin layer chromatography. One problem when using this method is that, water is a strong solvent for the normal-phase chromatography, traces of water in the mobile phase can markedly affect sample retention, and after changing the mobile phase, the column equilibration is very slow.

Mobile phase and stationary phase used for normal phase and reverse-phase chromatography
Stationary phase Mobile phase
Normal phase Polar Non polar
Reverse phase Non polar Polar

Reverse-phase chromatography

In reverse-phase (RP) chromatography the stationary phase has a hydrophobic character, while the mobile phase has a polar character. This is the reverse of the normal-phase chromatography ( [link] ). The interactions in RP-HPLC are considered to be the hydrophobic forces, and these forces are caused by the energies resulting from the disturbance of the dipolar structure of the solvent. The separation is typically based on the partition of the analyte between the stationary phase and the mobile phase. The solute molecules are in equilibrium between the hydrophobic stationary phase and partially polar mobile phase. The more hydrophobic molecule has a longer retention time while the ionized organic compounds, inorganic ions and polar metal molecules show little or no retention time.

Ion exchange chromatography

The ion exchange mechanism is based on electrostatic interactions between hydrated ions from a sample and oppositely charged functional groups on the stationary phase. Two types of mechanisms are used for the separation: in one mechanism, the elution uses a mobile phase that contains competing ions that would replace the analyte ions and push them off the column; another mechanism is to add a complexing reagent in the mobile phase and to change the sample species from their initial form. This modification on the molecules will lead them to elution. In addition to the exchange of ions, ion-exchange stationary phases are able to retain specific neutral molecules. This process is related to the retention based on the formation of complexes, and specific ions such as transition metals can be retained on a cation-exchange resin and can still accept lone-pair electrons from donor ligands. Thus neutral ligand molecules can be retained on resins treated with the transitional metal ions.

The modern ion exchange is capable of quantitative applications at rather low solute concentrations, and can be used in the analysis of aqueous samples for common inorganic anions (range 10 μg/L to 10 mg/L). Metal cations and inorganic anions are all separated predominantly by ionic interactions with the ion exchange resin. One of the largest industrial users of ion exchange is the food and beverage sector to determine the nitrogen-, sulfur-, and phosphorous- containing species as well as the halide ions. Also, ion exchange can be used to determine the dissolved inorganic and organic ions in natural and treated waters.

Questions & Answers

What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Good
advantages of NAA
Sai Reply
how I can reaction of mercury?
Sham Reply

Get the best Physical methods in ch... course in your pocket!





Source:  OpenStax, Physical methods in chemistry and nano science. OpenStax CNX. May 05, 2015 Download for free at http://legacy.cnx.org/content/col10699/1.21
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Physical methods in chemistry and nano science' conversation and receive update notifications?

Ask