1. Separation of Fullerenes With Liquid Crystal Bonded Silica Phases in Micro Column High Performance Liquid Chromatography

8/3/2019 1. Separation of Fullerenes With Liquid Crystal Bonded Silica Phases in Micro Column High Performance Liquid Chromatography

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Separation of Fullerenes withLiquid Crystal Bonded SilicaPhases in Microcolumn High

Performance Liquid

ChromatographyYoshihiro Saito, Hatsuichi Ohta,Hideo Nagashima, Kenji Itoh,

and Kyokatsu Jinno

A report by

L. Lao, R. Lopez, K.M.P. Palmario, and S. Sibug


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What are Fullerenes?

third allotropic form of carbon material(after graphite and diamond)

molecules composed entirely of carbon,

in the form of a hollow sphere, ellipsoid,or tube

similar in structure to graphite, which iscomposed of a sheet of linked

hexagonal rings, but they containpentagonal (or sometimes heptagonal)rings that prevent the sheet from beingplanar

Also ver lar e PAHs


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Polycyclic AromaticHydrocarbons

Potent atmospheric pollutants thatconsist of fused aromatic rings anddo not contain heteroatoms or carry

substituents (example: naphthalene) Produced as by-products of fuel

burning; found in cooked food; found

in meteorites Lipophilic

Formed from incomplete combustionofcarbon-containing fuels


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Microcolumn HPLC

Advantages Lesser reagent and starting material Greatly enhanced sensitivity. Dramatic solvent savings, without altering

the resolution and retention values. Ideal for applications in which very small

quantities of samples are available foranalysis.

Favorite choice for applications in LC/MS. Better choice for applications in drug

discoveries and screening. Ideal for applications in genomics and

proteomics.


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Octadecylsilane-Bonded SilicaStationary Phases

Commonly used as stationary phasefor separation of fullerenes

May be monomeric or polymeric have different mol shape and sizerecognition capability

Retention

Resolution

Elution order


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Liquid Crystal Bonded SilicaPhases

Liquid crystals generally of HMW and lowvolatility; ordered fluid mesophase of a longchain molecule with both solid-like molec.

order and liquid-like character Intermediate between solid and true

isotropic liquid

Advantage: Reduces or eliminates column-

bleed


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Objectives of the Study

To be able to separate C60 and C70fullerenes using liquid crystal silicabonded phases in HPLC

To be able to perform micro-columnHPLC


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Methodology

Syntheses and basic characteristicsof the bonded phases. Determination of surface coverage values of

these bonded phase used specific area of theoriginal silica gel and carbon content of these

bonded phases.


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Methodology


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Methodology

Chromatographic measurements.

the synthesized bonded phases werepacked using a slurry method.

The mobile phases were prepared fromguaranteed reagent grade n hexane,toluene,and dichloromethane.

Chromatographic measurements weredone at least 5 times.


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Methodology

PAH sample

used for evaluationin this investigation

were commerciallyavailable. Except TBN and

PhPh.


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Results and Discussion

Separation ofC60and C70 with two

liquid crystal

bonded silicaphases

n-hexane as themobile phase for the

evaluation of thebasic separationperformance of theliquid crystal

phases.


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Results and Discussion


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Effect of mobile phase composition onfullerene Separation

Using n-hexane/dichloromethaneand n-hexane/toluene asmobile phase

Smaller capacity factorswith increasingdichloromethane andtoluene

Better peak shapes ofchromatogram observedusing n-hexane/toluene

Due to increased solubility

of C60 and C70 in themobile phase


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Effect of mobile phase composition onfullerene Separation

Liquid crystal phase anda mobile phase withtoluene up about to 42% Can be used to obtain

the same separation

factor as ODS-5 (1.84)

Advantageous feature Better solubility

greater sampleloadability

Other good solventshaving greaterdissolution power can beused as mobile phase


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Effect of columntemperature

PAHs:

- k decreases withincreasing temperature- Normal temperaturebehavior observed

fullerenes:- k increases withincreasing temperature

- Selectivity slightlydecreases with increasing

temperature


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Effect if columntemperature


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Effects of columntemperature

Values forenthalpy oftransfer suggestthat the PAHs and

fullerenes havedifferent retentionmechanisms


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Molecular shape recognition

Previous study (Saito, 1994)evaluated molecular shaperecognition capabilities of liquid

crystal bonded phase with PAHs assample probes

Results indicated:

Liquid crystal phase had better planarityand shape recognition power than ODS

Selectivity significantly decreased with

increasing temperature


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Results indicatedecrease inplanarrecognitioncapability ofliquid crystalphase 1 with

increasing


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Results indicate thatmore elongated PAHsshow larger decrease inretention with increasingtemperature


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At elevated column temperature,phase ordering of liquid crystalsreduced by their thermal mobility

slot-like structure (ligandinterval that is smaller thanmolecular sizes of fullerenes)

At elevated temperatures, slot-likestructure is lost


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Proposed interaction modelPlanar, rod-like

NonplanarFullerenes


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Conclusion

At low temp, planar rod-like PAHsinteract effectively with the bondedphases = ordered structure

Nonplanar molecules cannot interact aswell

Fullerenes C60 have longer retentionthan PAHs at higher temp

Ligand interval increases as tempincreases Interaction between C60 and bonded phase is

easier

Results indicate possible effective

Documents

1. Separation of Fullerenes With Liquid Crystal Bonded Silica Phases in Micro Column High Performance Liquid Chromatography