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If the fraction from this step contains the analyte: Make this adjustment for optimum analyte recovery



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If the fraction from this step contains the analyte: Make this adjustment for optimum analyte recovery:
Load (4c)
The Oasis HLB sorbent has been found to retain ionized analytes more strongly than silica-based reversed-phase sorbents. However, recoveries maybe enhanced when analyte ionization is suppressed. For acidic analytes, adjust the sample pH to at least two pH units below the pKa of the acid. For basic analytes, adjust the pH to at least two pH units above the pKa of the conjugate acid.
Wash (4d)
Recoveries of very polar analytes can be increased by using only water (not 5% methanol in water) as the wash solution. First Elution (4e)
If an acceptable recovery of analyte(s) is obtained in this fraction (usually > 90%), no adjustments are necessary.
Second Elution
(4e repeated)
For very non-polar analytes, methanol may not have adequate elution strength. Stronger solvents such as acetonitrile or ethyl acetate maybe substituted, or used in sequence. In addition, for ionizable analytes, methanol may need to be modified with the addition of 2% acid or 2% base, as appropriate. If solvents stronger than methanol or acetonitrile are used for the elution, then a preliminary conditioning step (see step a) should be performed prior to the methanol conditioning step. For example, if ethyl acetate is to be used as an eluent, condition the cartridge with ethyl acetate, followed by methanol (a) and then water (4b).


[ Care and Use ManUal Waters Corporation
34 Maple Street Milford, MA 01757 USA. T 1 508 478 2000 F 1 508 872 1990 www.waters.com
Oasis HLB Disks Waters Corporation. Waters, The Science of What’s Possible, and Oasis are trademarks of Waters Corporation.
November 2008 EN Rev. A KK-PDF
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