Waters Oasis On-Line Columns SPE Columns For LC/MS/MS - Manual (Page 2)

Oasis On-Line Columns SPE Columns for LC/MS/MS 2
[ Care and Use ManUal ]
a. Oasis Patented Chemistries for Oasis On-line Columns
There are five available Oasis sorbent chemistries which are designed
to meet just about all of your on-line LC/MS/MS needs. They are
all built upon unique water-wettable Oasis HLB copolymer and
provide exceptional results. The sulfonated and Quanternary amine
derivatives Oasis MCX and MAX are designed for selective
retention of basic and acidic compounds respectively. Oasis WAX and
WCX are the derivatives of Oasis HLB. These sorbents are specifically
designed to offer the same benefits and features as the HLB with the
ability to retain and release strong acids (e.g. sulfonates) and strong
bases (e.g. quaternary amines), respectively.
Oasis HLB
Hydrophilic-Lipophilic Balance reversed-phase sorbent
Oasis MCX
Mixed-mode: Cation-eXchange and reversed-phase sorbent
Oasis MAX
Mixed-mode: Anion-eXchange and reversed-phase sorbent
Oasis WCX
Mixed-mode: Weak Cation-eXchange and reversed-phase sorbent
Oasis WAX
Mixed-mode: Weak Anion-eXchange and reversed-phase sorbent
b. Oasis On-line Column Configuration
There are three Oasis on-line column configurations to fit your
specific needs:
1. The Oasis cartridge column fits into a Sentry™ holder that
features a hand-tighten fitting for fast and convenient
cartridge replacement.
2. The direct connect column can be screwed directly into the
switchingvalve or connect to fittings like a conventional
HPLC column.
3. The Oasis column features traditional HPLC column fittings
and hardware.
All of these formats are available with the five Oasis sorbents and a
choice of particle sizes. The enclosed Certificate of Analysis (C.O.A.)
displays results from stringent quality control tests on the batch of
polymer sorbent.
The analysis is typically carried out using two pumps. The first is an
isocratic pump used as a standalone (no need for additional software
control) and the second is a binary pump used for elution. Generally,
the extraction of a drug is carried out on a stationary phase with
large particle (e.g. >25 μm) at high aqueous flow rate (4 mL/min).
This technique separates the large molecules (i.e. proteins and other
endogenous interferences), while the principal analyte is trapped on
the reversed phase. A mass spectrometer in the multiple reaction
monitoring (MRM) mode maximizes selectivity and sensitivity.
It is recommend to add a simple protein precipitation step prior
to injection. The Oasis on-line columns can give lifetime well over
100 injections.
II. sample preparatIon
The plasma sample is prepared by mixing equal volumes of plasma
with acetonitrile. Additives such as formic acid or ammonium
hydroxide may be added at 2 % V/V to release the protein binding
effect of plasma. An internal standard may also be added during
this step at the appropriate concentration. The samples are vortexed
and centrifuged at 3000 RPM for less than 30 minutes. This will
force the precipitate transferred into a clean 96-well collection plate
or vial, to the bottom of the collection vessel. Alternatively, with
the assistance of a robotic liquid handler, the supernatant can be
transferred to 96-well plates or vials.
III. equIpment
An HPLC system with minimum gradient mixing volume, and a
sample management system with low carry over characteristics such
as the Waters Alliance
® HT system, is essential for rapid throughput.
A switching valve is needed to divert interferences to a waste line.
While the stand alone pump loads the cartridge at 4 mL/min, the
binary pump keeps a constant and optimized 0.4 mL/min flow
through the analytical column and the electrospray interface. There is
no need to use a flow splitter.
NOTE: The maximum operational backpressure for these columns is
6,000 psi. Should you need to work at a higher pressure, please refer
to the Oasis Direct Connect HP 2.1 x 30 mm Column for Automated
Sample Preparation with Waters UPLC.