<< Chapter < Page Chapter >> Page >


Modifiers are added to the mobile phase to play with its properties. As mentioned a few times previously, CO 2 supercritical fluid lacks polarity. In order to add polarity to the fluid (without causing reactivity), a polar modifier will often be added. Modifiers usually raise the critical pressure and temperature of the mobile phase a little, but in return add polarity to the phase and result in a fully resolved sample. Unfortunately, with too much modifier, higher temperatures and pressures are needed and reactivity increases (which is dangerous and bad for the operator). Modifiers, such as ethanol or methanol, are used in small amounts as needed for the mobile phase in order to create a more polar fluid.

Advantages of supercritical fluid chromatography

Clearly, SFC possesses some extraordinary potential as far as chromatography techniques go. It has some incredible capabilities that allow efficient and accurate resolution of mixtures. Below is a summary of its advantages and disadvantages stacked against other conventional (competing) chromatography methods.

Advantages over hplc

  • Because supercritical fluids have low viscosities the analysis is faster, there is a much lower pressure drop across the column, and open tubular columns can be used.
  • Shorter column lengths are needed (10-20 m for SFC versus 15-60 m for HPLC) due to the high diffusivity of the supercritical fluid. More interactions can occur in a shorter span of time/distance.
  • Resolving power is much greater (5x) than HPLC due to the high diffusivity of the supercritical fluid. More interactions result in better separation of the components in a shorter amount of time.

Advantages over gc

  • Able to analyze many solutes with no derivatization since there is no need to convert most polar groups into nonpolar ones.
  • Can analyze thermally labile compounds more easily with high resolution since it can provide faster analysis at lower temperatures.
  • Can analyze solutes with high molecular weight due to their greater solubizing power.

General disadvantages

  • Cannot analyze extremely polar solutes due to relatively nonpolar mobile phase, CO 2 .


While the use of SFC has been mainly organic-oriented, there are still a few ways that inorganic compound mixtures are separated using the method. The two main ones, separation of chiral compounds (mainly metal-ligand complexes) and organometallics are discussed here.

Chiral compounds

For chiral molecules, the procedures and choice of column in SFC are very similar to those used in HPLC. Packed with cellulose type chiral stationary phase (or some other chiral stationary phase), the sample flows through the chiral compound and only molecules with a matching chirality will stick to the column. By running a pure CO 2 supercritical fluid mobile phase, the non-sticking enantiomer will elute first, followed eventually (but slowly) with the other one.

In the field of inorganic chemistry, a racemic mixture of Co(acac) 3 , both isomers shown in [link] , has been resolved using a cellulose-based chiral stationary phase. The SFC method was one of the best and most efficient instruments in analyzing the chiral compound. While SFC easily separates coordinate covalent compounds, it is not necessary to use such an extensive instrument to separate mixtures of it since there are many simpler techniques.

The two isomers of Co(acac) 3 in a racemic mixture which were resolved by SFC.


Many d-block organometallics are highly reactive and easily decompose in air. SFC offers a way to chromatograph mixtures of large, unusual organometallic compounds. Large cobalt and rhodium based organometallic compound mixtures have been separated using SFC ( [link] ) without exposing the compounds to air.

Examples of cobalt and rhodium based organometallic compound mixtures separated by SFC. Adapted from Compounds by I Bruheim, E Fooladi, E. Lundanes, T. Greibrokk, J. Microcolumn Sep. , 2001, 13 , 156.

By using a stationary phase of siloxanes, oxygen-linked silicon particles with different substituents attached, the organometallics were resolved based on size and charge. Thanks to the non-polar, highly diffusive, and high viscosity properties of a 100% CO 2 supercritical fluid, the mixture was resolved and analyzed with a flame ionization detector. It was determined that the method was sensitive enough to detect impurities of 1%. Because the efficiency of SFC is so impressive, the potential for it in the organometallic field is huge. Identifying impurities down to 1% shows promise for not only preliminary data in experiments, but quality control as well.


While it may have its drawbacks, SFC remains an untapped resource in the ways of chromatography. The advantages to using supercritical fluids as mobile phases demonstrate how resolution can be increased without sacrificing time or increasing column length. Nonetheless, it is still a well-utilized resource in the organic, biomedical, and pharmaceutical industries. SFC shows promise as a reliable way of separating and analyzing mixtures.


  • D. R. Gere, R. Board, and D. McManigill, Anal. Chem. , 1982, 54 , 736.
  • E. Klesper, A. H. Corwin, and D. A. Turner, Org. Chem. , 1962, 27 , 700.
  • M.N. Meyers, J. Giddings, Anal. Chem. , 1965, 37 , 1453.
  • K. Miyazawa, T. Ishiguro, and H. Oda, FPC production . Daicel Chemical Industries, LTD. Myoko, Japan (2007).
  • L. Toribio, C. Alonso, M. J. del Nozal, J. L. Bernal, and J. J. Jimnez, J. Sep. Sci. , 2006, 29 , 1363.
  • M. Caude and D. Thiebaut, Practical Supercritical Fluid Chromatography and Extraction , Harwood Academic Publishers, Amsterdam (1999).
  • M. D. Palmieri, J. Chem. Educ. , 1989, 66 , A141.
  • M. Saito, J. Biosci. Bioeng. , 2013, 115 , 590.
  • M. Yoshioka, S. Parvez, T. Miazaki, and H. Parvez, Supercritical Fluid Chromatography and Micro-HPLC , VNU Science Press, The Netherlands (1989).
  • R. M. Smith, Supercritical Fluid Chromatography , Royal Society of Chemistry (1988).
  • T. L. Chester and J. D. Pinkston, Anal. Chem. , 1990, 62 , 394R.

Questions & Answers

Do somebody tell me a best nano engineering book for beginners?
s. Reply
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
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.
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
what is system testing
what is the application of nanotechnology?
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
I'm interested in Nanotube
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
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
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?