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Online SPE for water analysis
Direct analysis of phenanthrene in tap water at 5 ppb and 50 ppt level using online SPE coupled with
HPLC. SPE column, TrapN; analytical column PromSil C18; sample volume, 40 mL; flow rate for
sample loading, 6 mL/min; detection wavelength, 252 nm.
In an offline approach, normally 500 to 1000 mL water need to be extracted. Further concentration and
solvent exchange are followed before the instrument analysis. Only a very small portion of the
concentrated sample is injected to the HPLC. To achieve similar detection limit of online SPE, 4-liters of
water need to be extracted. The processing time for one sample is above 1 hour.
Another advantage of online SPE over offline SPE is its good reproducibility. Since online SPE involves
fewer procedures than the offline approach and all these procedures are controlled by instrument, the
chance of error is much less. Even at 0.05 ppb level, the %RSD is only 2.5 (n=3).
Therefore, if the pollutant can be analyzed by HPLC, the online approach should be used.
The key for a successful application of online SPE is the selection of a suitable SPE column and the
analytical column. To simplify the method development, PromoChrom provides two method kits with
well matched SPE column and the analytical column. They also include the method parameters for most
common analysis. By slightly adjusting the parameters, users can easily development their own methods.