Waters Oasis Mixed-Mode Ion-Exchange Cartridges and 96-Well Plates - Manual (Page 2)

II. SAMPLE P RE-T REATMENT
a. Biological Samples
This section contains recommendations for preparing your
biological samples (plasma, serum, urine, etc.) prior to solid-
phase extraction.
1. Prepare acidified or basified water diluents.
Note: (To prepare 4% phosphoric acid, Dilute 4.7 mL of 85%
phosphoric acid (the most common available formulation) to
100 mL final volume with water. Or 11.76 mL to 250 mL). To
prepare 5% concentrated ammonia, dilute 5 mL of concentrated
ammonia solution to 100 mL with water. Users will need to
prepare large volumes 100 -250 mL) of pretreatement buffer to
accomodate multiple samples and ensure consistency in the
buffer composition.)
2. Dilute plasma or urine, 1:1 with acidified or basified water.
Add 10 to 50 μL of internal standard.
Note: Final concentration should be no more than 10% organic
otherwise protein precipitation will occur. If necessary, clarify
samples by centrifugation at 8,000 x g for 10-30 minutes.
b. Solid Samples: Soil, Whole foods, Tissue
1. Homogenize the sample with an appropriate solvent to obtain
an aqueous based or an organic solvent based extract of the
sample. Initial extraction conditions are chosen to maximize
analyte recovery, while minimizing matrix interference. In
many cases, it may be beneficial to add buffers, dispersive
salts, or co-solvents to improve extraction efficiency.
2. Adjust the initial extract to optimize analyte retention onto
the SPE sorbent. This can include pH adjustment, solvent
adjustment, or solvent exchange through evaporation and
reconstitution (refer to Sections IV and V). It may be necessary
to centrifuge or filter the sample prior to loading.
c. Aqueous Samples: Water, Beverages
Adjust pH to maximize analyte retention on the SPE sorbent. Buffer
salts and dispersive agents may be used to increase partitioning
onto the SPE sorbent. Pretreatment to remove suspended matter
prior to SPE treatment may include filtration or centrifugation.
d. Non-Aqueous Liquid
When appropriate the sample may be diluted with aqueous buffers
and organic co-solvents for reversed-phased or mix-mode SPE. If
sufficient dilution has occurred, the sample may be treated in a
manner similar to an aqueous sample.
Note: If necessary, filter samples for suspended solids
(Ex. Environmental/Waste water/Water analysis/Food, etc.)
III. SOLID PHASE EX T RACTION FOR BASIC
COMPOUNDS USING OASIS MCX AND
ST RONGLY ACIDIC COMPOUNDS USING
OASIS WAX
1. Place Oasis MCX or Oasis WAX Cartridge or Plate on the
vacuum manifold and set the vacuum to 5” Hg.
2. Condition with Methanol.
3. Equilibrate with Water
a. In each case (conditioning and equilibration) add the
solvent before applying vacuum.
4. Switch off the vacuum pump or stop vacuum by closing the
valve (before switching off the vacuum pump, please reduce
the vacuum to the lowest possible).
5. Load your diluted sample.
6. Switch on or open valve at lowest possible vacuum and
gradually increase as needed in order to load the entire
sample onto the sorbent bed.
7. Switch off the vacuum pump or stop vacuum by closing the valve.
8. Apply 2% fromic acid in water or other suitable acid (such as
0.1 N HCL) as wash solvent.
9. Switch on vacuum to 5”Hg (adjust/increase as needed).
10. Pull vacuum for another 30 sec to a minute to eliminate
residual wash solvent.
11. Switch off the vacuum pump or stop vacuum by closing the
valve. (before switching off the vacuum pump, please reduce
the vacuum to the lowest possible).
12. Apply 100% organic elution solvent and let it flow through
by gravity before switching on the vacuum pump.
13. Switch on vacuum to 5”Hg (adjust/increase as needed).
14. Pull vacuum for another 30 sec to a minute to eliminate
residual wash solvent.
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Oasis Mixed-Mode Ion-Exchange Cartridges and 96-Well Plates