SAMPLE PROCESSING continued
chamber that limits the liquid volume. After a minute, the fi lter sandwich is removed and discarded with the excess blood. Analytes (proteins and drug metabolites) are adsorbed on the disk surface. The small volume dries quickly. Intercard %CV is better than 2% by LC-MS/MS.
New phases for selective SPE
Extraction of toxins Patulin is a toxin indicating spoilage, particularly in apples and some grains. Food safety concerns may lead to the need to extract the toxin from matrices. Supelco (Bellefonte, PA;
www.sigmaaldrich.com) has developed a molecularly imprinted polymer SPE phase that selectively attracts and captures patulin, thus improving the detection limits of the assay. This phase is particularly significant, since few successful applica- tions of molecularly imprinted polymers have been reported after 30 years of intense development.
Biotage’s (Charlotte, NC;
www.biotage.com) ISOLUTE MYCO is for extract- ing mycotoxins from food, particularly grains. It also works for concentrating patulin from apple juice. ISOLUTE SLE+ is now available in 400-μL cartridges for supported liquid extraction (SLE).
Selective extraction of phospholipids The presence of phospholipids in blood and plasma samples can lead to ion suppression in LC-MS/MS, which aff ects detection sensitivity and produces
an irreproducible response. The two solutions are to use very low fl ow rate to MS or selectively extract the phospholipids prior to separation. Supelco chose to address the latter by introducing the HybridSPE-Phospholipid extraction cartridge packed with zirconia-silica particles. Some may recall that zirconia has strong avidity for phosphates.
Bonna-Agela Technologies introduced Cleanert® MAS for the selective removal of phospholipids. MAS uses a specially prepared diatomaceous earth in SPE cartridges or multiple-well plates for quick and easy removal of phospholipids. The workfl ow usually uses a protein crash followed by MAS extraction, then MAS. Side-by-side comparison with SPE, supported liquid extraction, and protein crash alone show that MAS treatment improves MS detection signifi cantly.
Biotage is a recognized leader in solid phase extraction and supported liquid extraction, commonly used to remove assay interferences and for analyte concentration. This year Biotage introduced the ISOLUTE® PLD+, Protein and Phospholipid Removal Plates. These are generally used for removing proteins and phospholipids from blood samples. Extraction effi ciency is greater than 99% and the format is automation compatible. Just dispense an appropriate amount of crash solvent, usually ACN, into each well and add the blood or plasma samples. Allow the protein to precipitate out. Then apply a vacuum or positive pressure, moving the sample through the packing bed. Proteins and phospholipids are retained
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