Drying Samples in
Newborn Screening and DBS

DBS samples contain a mixture of blood components, solvents, and sometimes preservatives. Before analysis, it is often necessary to prepare these samples in a way that makes the target analytes (like metabolites or genetic markers) more accessible for detection. 

Here's how evaporators are used in this context:

Extraction of Analytes

- The dried blood spot is typically punched out from the filter paper.

- These punches are placed in a solution (the extraction solvent) to extract the analytes of interest from the blood matrix.

- The solvent commonly used for extraction is chosen based on the target analytes and the type of analysis to be performed.

Concentration and Drying 

- After extraction, the solution contains the analytes dissolved in the solvent.

- Evaporators are used to remove the solvent from this solution. This is usually done under controlled conditions (e.g., gentle heat and reduced pressure) to ensure the analytes are not degraded or lost.

- The purpose of using the evaporator is to concentrate the analytes and to remove the solvent completely, leaving behind a dry extract. This is crucial for achieving accurate and sensitive measurements.

Reconstitution in Mobile Phase 

- The dried extract is then reconstituted in a mobile phase compatible with the subsequent analytical method, such as liquid chromatography or mass spectrometry.

- The mobile phase is usually a solvent or a mixture of solvents that allows the analytes to be efficiently separated and detected during the analysis.

Several types of evaporators can be used in the preparation of DBS samples:

Centrifugal Evaporators

- These devices use centrifugal force along with controlled heat and vacuum to evaporate solvents. 

- They are suitable for handling multiple samples simultaneously, which is ideal for high-throughput screening.

Nitrogen Evaporators 

- These use a stream of nitrogen gas to blow over the surface of the liquid, facilitating solvent evaporation.

- They are simple and effective, especially for very small volumes.

→ Discover: Nitrogen Blowdown in Preparing Dried Blood Spot Samples in 96-Well Plates for Newborn Screening

Rotary Evaporators

- Though not as common for DBS due to their size and the nature of samples, rotary evaporators can be used for larger volume preparations.

- They use rotating flasks and vacuum to enhance solvent evaporation.

→ Discover: When nitrogen blowdown is preferred over centrifugal evaporation

🔵 Efficiency: Rapid removal of solvent to concentrate analytes without significant loss or degradation.

🔵 Precision: Better control over evaporation conditions (temperature, pressure), leading to consistent and reproducible results.

🔵 Compatibility: Facilitates the transfer of analytes into a compatible mobile phase for subsequent analytical procedures.

For instance, if a newborn screening test is looking for specific metabolic disorders, the following might occur:

- The DBS sample is punched and extracted with a methanol-water mixture. 

- The extract is evaporated to dryness using a blowdown microplate evaporator. 

- The dried residue is then reconstituted in a mobile phase (e.g., acetonitrile-water) for analysis by liquid chromatography-mass spectrometry (LC-MS).

In summary, evaporators are essential in preparing dried blood spot samples for newborn screening, ensuring that analytes are effectively concentrated and matched with the appropriate mobile phase for accurate and efficient detection.

→ Next: Nitrogen Blowdown in Preparing Dried Blood Spot Samples in 96-Well Plates for Newborn Screening