Solid Phase Extraction (SPE)

SPEC® Solid Phase Extraction Products

Development of a Robust and Sensitive Analytical Method for the Measurement of Pharmaceutical Compounds in Serum using LC/MS. 2004 ASMS Poster (960kB, .pdf)

Rapid, Low Volume... Trouble-Free SPE

Varian's SPEC Solid Phase Extraction products are manufactured with "ultra-clean" polypropylene plastic and bonded-silica impregnated on a glass fiber disc. SPEC disc SPE products provide exceptionally high recovery, concentrated samples eluted in miniscule volumes, fewer matrix interferences, and headache-free operation.

No Interferences and Reduced Ion Suppression

SPEC's low bed mass, raw material purity, and optimized selectivity result in extracted samples which are free of contaminating peaks and matrix interferences. That means SPEC provides reduced ion-suppression and increased sensitivity.

Figure 1

(click on image for larger view)

Figure 1 is an HPLC chromatogram of a plasma sample spiked with two analytes. Note the cleanliness of the chromatogram, which is due to the cleanliness of SPEC materials and the selective extraction of the SPEC disc. GC-FID shows no leaching of contaminants from SPEC and significant leaching from a popular packed-bed SPE product.

If the extraction tools aren't clean, the extractions aren't clean.

Figure 2

Blue = Standard Green = SPEC Red = Leading Competitor

Figure 2 is a comparison of LC-MS ion-suppression by area counts. The blue column is a reference standard, the green column is an extract from SPEC C18AR, and the red column is an extract from a leading "polymeric" SPE product. Note the increased sensitivity provided by SPEC as compared to the "leading" competitive brand.

Varian's proprietary SPEC technology yields a highly efficient, small bed mass of just 15 mg. The major advantages of this strategy are faster processing and lower costs. A typical SPEC extraction has just four or five steps (condition, apply sample, wash, and elute) and uses only 1.5 mL or less of total solvents! This means that your lab's costs per extraction decrease while your productivity increases.

Figure 3

Green = SPEC Red = Packed Bed

Figure 3 shows a customer's comparison of a SPEC competitor's "Packed Bed" product. The data shows a dramatic reduction in extraction steps and solvents used to process the same sample using SPEC. The increase in productivity by the reduction in extraction steps and solvent use becomes even more apparent when SPEC is used on automated platforms.

Improved Disc technology

Figure 4

Y axis = Flow Rate X and Z axes = Well Positions

SPEC® solid phase extraction disks are a significant advance in disk-based SPE. Problems associated with channeling (e.g. non-uniform flow through the extraction bed) and poor reproducibility (Figure 4) are eliminated by SPEC products.

Click on image for an enlarged view and details of the data

Better flow properties

Figure 5

Y axis = Flow Rate X and Z axes = Well Positions

Owing to the uniform flow properties (Figure 5) and excellent mass transfer characteristics of SPEC, large volumes of dilute samples (e.g. environmental samples) or highly viscous, particle-laden samples (e.g. plasma) can be processed quickly without clogging the SPEC disk. SPEC allows plasma flow rates of up to ten times faster than the competition.

Smaller processing volumes

Analytes are adsorbed and desorbed with remarkably small quantities of solvents. Analytes can be collected in a fraction of the volume of packed-bed SPE products, and solvent use overall is greatly reduced.

SPEC extraction disks are composed of glass microfiber disks densely impregnated with modified silica. Compared with standard packed-bed SPE columns and Teflon®-based disks, SPEC disks contain much smaller particles which, though densely packed, allow greatly improved flow. Dense particle loading and highly uniform particle distribution throughout the membrane result in highly efficient mass transfer compared with packed-bed SPE columns. Since the particles are smaller and packed more densely, there is much less void volume and less solvent is used in sample processing (see table which compares THC metabolite preparation on standard packed-bed SPE and SPEC ).

The improved flow properties of SPEC disks greatly improves column-to-column reproducibility and simplifies automation. SPEC contains a double-layer glass-fiber prefiltration system on top of the actual extraction disk. This filtration system is so efficient that particle-laden samples such as wastewater, plasma, serum, saliva, and urine can be loaded directly onto the column without precentrifugation or filtration and without clogging.

SPEC products are available with all of the conventional bonded-phase chemistries used in SPE, in four different formats: standard syringe-barrel columns, 96-well plates, 47mm and 90mm disks, and a unique design which incorporates SPEC disks and pre-filters into a standard pipette tip. The pipette tip design, known as SPEC® PLUS PT, lends itself to easy automation and completely eliminates the vexing problem of cross contamination.

SPEC columns are compatible with most automated SPE systems, including Gilson's ASPEC®, Hamilton's MicroLab®, Tecan U.S.'s MegaFlex®, and Zymark's Benchmate®.