Editors
     
02/18
 Topic
Fast HPLC analyses under highly aqueous conditions



Polar compounds, e.g. organic acids, water-soluble vitamins or metabolites of pesticides and pharmaceuticals, often require mobile phases with more than 95 vol% aqueous content. For this purpose, stationary phases with high stability in highly aqueous mobile phase systems based on fully porous silica gel were developed.
 
The introduction of core-shell particles significantly reduced analysis time in reversed phase chromatography. Meanwhile stationary phases suitable for 100 % aqueous eluents based on this technology are available, too.

  Stability of RP 18 phases in highly aqueous eluents
  Conventional octadecyl phases normally show poor performance with highly aqueous eluents due to a phenomenon also described in literature as "phase collapse" [Neue et al., Chromatographia 54 (2001), 169-177]. Recent studies argue that the wetting angle of the hydrophobic phase is unfavorable for interactions with analytes. By incorporation of a polar group, also called "embedded group", or by polar endcapping, the hydrophilicity and thus the stability in highly aqueous eluents of the otherwise hydrophobic RP 18 phase is increased.

Examples of "embedded group" phases are NUCLEODUR® PolarTec, Zorbax® Bonus-RP, SymmetryShieldTM RP 18 and SUPELCOSILTM LC-ABZ+. The polar endcapped phases, such as NUCLEODUR® C18 Pyramid, Synergi® Hydro-RP or Atlantis® dC18, exhibit low bleeding features, which is advantageous in LC/MS applications.

  Fast HPLC analysis by core-shell technology
  Core-shell phases consist of a solid core of silica surrounded by an outer porous shell of silica gel, which is assembled in a sol-gel process. The diffusion path of the mobile phase through the porous layer of the stationary phase is significantly shortened in comparison to the diffusion through completely porous particles with corresponding particle size. The short diffusion paths in the core-shell particles reduce the retention time of the solute molecules in the stationary phase, so that even at higher flow rates of the mobile phase, optimum separation results with maximum resolution are achieved. Beneficial side-effects are reduced column back pressure and shorter run times (see also Chroma-News 03/11).


  NUCLEOSHELL® Bluebird RP 18 for fast HPLC analysis under up to 100 % aqueous conditions
  The recently launched NUCLEOSHELL® Bluebird RP 18, combines the benefits of core-shell particles and the stability in highly aqueous eluents made possible by polar endcapping.

 


  Figure 1: HPLC-UV analysis of organic acids under 100 % aqueous conditions (sample details)


  In addition to the shown separation of nine organic acids, in the MN application database the successful separation of isomers of organic acids under purely aqueous conditions can be found, too.

Highly aqueous conditions are also advantageous in the analysis of water-soluble vitamins. Figure 2 shows the gradient method of the LC-MS/MS determination in a multivitamin supplement.

 


  Figure 2: HPLC-MS/MS analysis of water-soluble vitamins in a vitamin tablet
               (more details, see also analysis in multivitamin juice)


  Further applications with the aqueous stable core-shell phase in food analysis are:

For the determination of numerous pesticides, multimethods are often used. Figure 3 shows the LC-MS/MS analysis of over 190 pesticides in less than 6 minutes. The extraction from red grapes was carried out with CHROMABOND® QuEChERS mixes.

 


  Figure 3: Determination of pesticide residues (spiked) in red grapes after QuEChERS
               extraction (list of substances and further details)


With NUCLEOSHELL® Bluebird RP 18 columns, mixtures of different pharmaceuticals, sulfonic acid antibiotics and X-ray contrast media can be efficiently analyzed. The drug analysis of THC and its metabolites is started with a gradient of 100 % aqueous formic acid (0.1 %) and the eluent system is switched to 90 % acetonitrile with formic acid (0.1 %) within only 2.5 minutes, which requires an aqueous stable RP 18 phase.

  Conclusion
  The core shell phase NUCLEOSHELL® Bluebird RP 18 with polar endcapping allows rapid HPLC runs under highly aqueous conditions, as shown in the applications presented.


  Trademarks
  Atlantis® – Waters Corp. (USA)
NUCLEODUR® – MACHEREY-NAGEL GmbH & Co. KG (Germany)
NUCLEOSHELL® – MACHEREY-NAGEL GmbH & Co. KG (Germany)
SUPELCOSILTM – Sigma-Aldrich Co. (USA)
SymmetryShieldTM – Waters Corp. (USA)
Synergi® – Phenomenex Inc. (USA)
Zorbax® – Agilent Technologies Inc. (USA)
 
Image credits
© New Dawn Photography – www. fotolia.com
 
Contact the author – Please click here!
 
  More information – PDF download of Bluebird RP 18 brochure
 

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 MN Special Offer

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 MN Application Highlight

TLC separation of flavonoids on "High Definition" phase


Natural products, such as the flavonoids (phytochemicals), are ideally separated by thin-layer chromatography (TLC). Matrix effects are less problematic for the robust TLC than for e.g. HPLC methods.

In order to evaluate results better, a good visibility of the spots is important. The excellent staining properties and the brilliant luminosity (under UV light) of SIL HD TLC glass plates provide improved visibility.

The presented TLC application shows the high brilliance of the new "High Definition" phase SIL HD.


View FULL APPLICATION MN Appl. No. 403760 – Please click here!

You can find more TLC applications in the MN application database!


 MN Product Highlight

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 MN Literature Recommendation

NUCLEOSHELL® Bluebird RP 18 brochure
All important information at a glance


 

In this brochure you will find technical information as well as numerous valuable applications with our latest HPLC phase NUCLEOSHELL® Bluebird RP 18 – especially developed for MS methods.


Content of brochure
  • Product description and technical data
  • Typical applications from various fields
  • Ordering information
  More INFORMATION about NUCLEOSHELL® Bluebird RP 18!

Order a HARDCOPY – Please click here!

DOWNLOAD of PDF version!
 


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