Extraction - Extraction is a commonly used process for sample preparation. Extractions can be performed as liquid-liquid or liquid-solid phases. The use of solid phase extraction, also known as SPE, is common in many laboratories.
Applications	Sample preparation prior to HPLC or HPLC/MS analysis Sample preparation prior to high throughput screening

Zinsser platforms such as the Sophas can be used for liquid-liquid extractions. The pipettor can deliver the required solvents to sample vials or plates, and vortexing with heating or cooling can be applied prior to withdrawal of the separated phase.

For SPE, Zinsser offers the Speedy, a robotic platform that is optimized for automated solid phase extraction.

The Zinsser Analytic Speedy is an automated Solid Phase Extraction system that can operate with 96-well format filter plates or with 1-5 ml cartridges. The SPEEDY can operate with either a vacuum-based SPE system or a positive pressure system that addresses the inherent drawbacks of the 96-well format that is traditionally run with vacuum.

The Speedy platform is configured with four variable-spacing probes and a robotic gripper. The gripper is shown here holding a vacuum manifold with a filter plate in preparation for placement on the vacuum box. The gripper can remove the manifold, store it temporarily, place the collection plate on the vacuum box, then return the manifold for the final extraction step. Pulsed vacuum is then applied via the WinLissy software.

Performing vacuum-driven SPE with 96-well format filter plates is a suitable method if all samples are of uniform consistency, however this method can present some inherent problems that can be difficult to overcome with tough samples such as plasma or other biofluids. These problems are mainly due to the mechanism of attempting to pull a uniform vacuum through all 96 positions.

• Requires the use of an entire filter plate even if less than 96 samples need to be run. Even if only a few rows or columns of the filter are used, the change in flow dynamics in those wells after the extraction process will make it difficult to re-use the plate for the unused positions, resulting in extra expense.
• If one well clears (all liquid is pulled out) before the others due to varying flow dynamics, the extraction efficiency for the entire plate will be compromised. This is due to the fact that the vacuum will tend to expend itself through the path of least resistance, which will be through the cleared well, resulting in greatly reduced vacuum to all other wells.
• Cross-contamination can occur at the collection plate due to vortexing effects near the bottom tips of the filter plate.

These problems can lead to low recoveries and variable results when using vacuum-based SPE filtration methods.

Speedy can overcome these problems by using positive pressure applied from the top instead of vacuum. The system is configured with 2-channel probes that can be used to deliver either liquid or gas (usually nitrogen). The probes pick up special cartridge adaptors or pressure spots that are then placed directly on top of the SPE cartridge. The system can work with 1, 3, or 5 ml SPE cartridges in this manner. The cartridge adaptor forms a seal within the SPE cartridge allowing the probe to pressurize the internal environment. The positive pressure technique provides the additional benefit of keeping the sample in an inert environment, which is particularly useful for samples that are sensitive to oxidation.

Speedy enhances the positive pressure technique by using digital pressure control and independent active monitoring of the pressure within each cartridge. The initial applied pressure is kept lower so that splashing does not occur within the cartridge. The pressure is then increased to a steady level for the extraction phase. The software will recognize the pressure drop that occurs when the cartridge is cleared of liquid and can shut down pressure independently for each cartridge, preventing unnecessary compression of the filter be and drying-out of samples.

With the positive pressure system optimal and reproducible extraction conditions for each sample are assured, regardless of the sample viscosity, filter variations, or other variable conditions.

The result is finally an automated SPE system that can produce large numbers of SPE extractions without operator intervention, removing the tedium of manual SPE lab work.

Typical vacuum SPE: Recommended collection height places cartridge tips above the wells of the receiving plate.	Typical vacuum SPE: Cross-contamination can occur during vacuum application due to localized splashing near top of receiver plate wells.	Speedy: Tight seal of cartridge adaptor to the SPE cartridge allows positive pressurization via the probe and eliminates cross-contamination between samples.