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| 01/12 |
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Innovative SPE phases with large and
small particles
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In recent years polymer phases have been established as a
standard in SPE. Besides widely
applicable, nonpolar, hydrophobic RP phases, polar ionic mixed-mode phases
based on polymers are also used for many applications.
Initially, these innovative SPE phases were offered with
standard particle sizes (average 85 µm). Enhancements of these phases with
smaller particle sizes increase the efficiency with respect to elution characteristics
and breakthrough behavior.
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Polymeric reversed and mixed-mode phases
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Polymeric RP phases (e.g.,
LiChrolut® EN – Merck, CHROMABOND® HR-P –
MACHEREY-NAGEL), based on polystyrene-divinylbenzene copolymers (PS/DVB) have
been commercially offered since the end of the 1980s. They rapidly convinced
for multi-methods, like those used in the field of environmental analysis. Later
on, further polymeric RP phases with hydrophilic-lipophilic balance (Oasis®
HLB – Waters) or phases based on a polar bifunctional PS/DVB copolymer (CHROMABOND®
Easy – MACHEREY-NAGEL) were developed.
CHROMABOND® HR-Xpert feature an innovative concept including
five polymer-based RP and mixed-mode phases. The phases are based on a modern,
spherical polymer with different particle sizes of 85 µm and 45 µm. The phases
show ideal flow characteristics due to the spherical material. An optimized
pore structure and a high specific surface facilitate high loadability and good
elution properties, decreasing the solvent consumption and eventually affording
a rapid and economical analysis.
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Phase overview CHROMABOND® HR-Xpert
| Phase |
Material |
Application |
HR-X
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spherical, hydrophobic RP phase
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neutral compounds
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| HR-XC |
strong mixed-mode cation exchanger
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basic compounds
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| HR-XCW |
weak mixed-mode cation exchanger |
strong bases
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| HR-XA |
strong mixed-mode anion exchanger |
acidic compounds |
| HR-XAW |
weak mixed-mode anion exchanger |
strong acids
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CHROMABOND® HR-X is a
spherical, hydrophobic PS/DVB phase, which can be universally applied for
extraction of neutral, nonpolar and polar compounds in the fields of
environmental (e.g., 33 pesticides from water), food (e.g., catecholamines from green tea) and pharmaceutical analysis (e.g., antiinflammatory drugs).
The mixed-mode phases (ion
exchange polymers based on PS/DVB) feature distinct ion exchange and reversed
phase properties. They are suitable for extraction of polar or ionic analytes
from complex matrices (e.g., urine, plasma, serum, pharmaceuticals, food). The
strong cation exchanger CHROMABOND®
HR-XC is recommended for
extraction of basic compounds (e.g., codeine or methadone from serum or urine, fungicides from juice); the weak cation exchanger HR-XCW can be used for strong
bases (e.g., paraquat/diquat from water). Accordingly, the strong or weak anion
exchangers HR-XA and HR-XAW are used for an enrichment of acidic compounds
(e.g., allantoin in cosmetic products) or for strong acids (e.g. perfluorated surfactants from water).
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Chemical structures CHROMABOND® HR-Xpert
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Optimal sample preparation by means of polymer phases with
different particle sizes
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To meet the demands of manifold specific applications polymer
phases are offered with different particle sizes.
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Particle sizes of commercial polymer phases
| Manufacturer |
Phase
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Particle sizes
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Waters
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Oasis® HLB
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30 µm
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60 µm
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| Phenomenex |
StrataTM X
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33 µm
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StrataTM XL |
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100 µm
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| Agilent |
Plexa |
45 µm
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NEXUS |
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70 µm
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ENV |
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125 µm
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MACHEREY-NAGEL
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CHROMABOND® HR-Xpert
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45 µm
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85 µm
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The phases of the CHROMABOND® HR-Xpert concept are available with particle
sizes of 45 µm and 85 µm. 45 µm particles are recommended for columns with
small sorbent amounts and for applications with small sample volumes, as well
as with low elution volumes. For columns with larger sorbent amounts and for voluminous, viscous or heavily matrix-contaminated
samples, as well as for operation without vacuum (e.g., for volatile analytes),
85 µm are recommended.
Due to the about half radius of the 45 µm particle compared to
a 85 µm particle, an eightfold particle number per sorbent volume (approx.
equivalent sorbent amount) in the column is possible. Hence, the freely
accessible external surface is much larger for the 45 µm sorbent, with the same
specific surface for both particle sizes. A more compact sorbent package of the
45 µm particles additionally enhances an intensive interaction of the analytes
with the sorbent. Thus, better extraction results are achieved.
The following experiment shows the advantages of a faster
elution with a lower elution volume needed for the 45 µm phase: After column
conditioning (5 mL methanol, then 5 mL water) 1 mL of a standard solution of 1
mg hexobarbital per mL water is applied each on a column CHROMABOND®
HR-X, 1 mL, 30 mg with 45 µm and with 85 µm particles. After washing (5 mL
water) and drying the columns are stepwise eluted in portions of 100 µL with
methanol and the recovery rates are determined.
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Elution characteristics of 45 µm and 85 µm polymer phases
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For 45 µm particles a part of approx. 55 % was already
recovered after 200 µL elution solvent, whereas for 85 µm only approx. 25 %
analyte were eluted. After 400 µL the elution for the smaller particle size is
already complete.
A further experiment investigates the breakthrough behavior
for the enrichment of hexobarbital. After conditioning (5 mL methanol, then 5
mL water) portions of 1 mL standard solution of 250 µg analyte in 1 mL water each
are stepwise applied on a column CHROMABOND® HR-X, 1 mL, 15 mg with
45 µm and on a further column with 85 µm particles. The eluates are collected
and before HPLC analysis, filled up to 1 mL each for compensation of the
elution solvent.
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Breakthrough behavior of 45 µm and 85 µm polymer phases
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For the 45 µm polymer phase the analyte is completely
retained up to the fraction 10, whereas small amounts even break through at
fraction 4 for 85 µm. 45 µm particles features a better breakthrough behavior for
small sorbent amounts. When using larger sorbent amounts this effect is less
distinct, because in this case for 85 µm particles a sufficient contact of
analyte and sorbent is given.
45 µm phases are ideal for small sample and elution volumes,
due to better elution characteristics and breakthrough behavior with small
sorbent amounts. Phases with 85 µm particels should be preferred for low
amounts of sample and sorbent, because they show better flow characteristics.
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Conclusion
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The polymeric reversed
and mixed-mode phases of the CHROMABOND® HR-Xpert concept can be successfully used for the enrichment of
neutral, acidic and basic compounds in many fields of application.
Due to the availability of these
phases with particle sizes of 45 µm and 85 µm, they can be selected specifically
in relation to sample size and properties. Thus, an optimal sample preparation
is made possible.
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Contact to the author - Please click here!
Please find previous editions of this news-letter on various topics in our Chroma-News Archive!
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| MN Special Offer |
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50 % Discount on
CHROMABOND®
HR-Xpert development kits
Try our new CHROMABOND® HR-Xpert development kits and receive 50 % introductory discount
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MACHEREY-NAGEL offers exclusively for our
Chroma-News readers a special promotion discount of 50 % on CHROMABOND® HR-Xpert development kits – comprising five innovative
polymer-based RP- and mixed-mode ion exchanger phases for SPE:
- CHROMABOND® HR-X: hydrophobic PS/DVB copolymer
- CHROMABOND® HR-XC: strong mixed-mode cation exchanger
- CHROMABOND® HR-XA: strong mixed-mode anion exchanger
- CHROMABOND® HR-XCW: weak mixed-mode cation exchanger
- CHROMABOND® HR-XAW: weak mixed-mode anion exchanger
These five phases build the innovative CHROMABOND® HR-Xpert concept for cleaner samples – all phases are based on pure and spherical polymeric resin and provide:
- excellent recovery rates
- reliable and cost-efficient analyses
- highest reproducibility
- robust retention mechanism even for aggressive washing procedures
- low limits of detection also for critical matrices
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Just contact MN by referring to promotion code “HR-Xpert” and we will arrange all necessity with your local MN distributor.
To take advantage of this SPECIAL OFFER – Please click here!
This offer is valid until April 30th, 2012 and exclusive for listed Chroma-News recipients – not valid for distributors – while stocks last!
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