Punching is still used in many laboratories (especially in the field of newborn screening) nowadays. Thereby, the DBS are punched out and extracted in micro centrifuge tubes. As soon as the disc is punched, there is no more connection between the sample and the label. Discs need to be handled carefully, as they can get electrostatically charged and jump in-between wells. The extraction process can be varied in terms of solvent, time, and treatment. The extracts are centrifuged and either analyzed directly or dried and reconstituted in the mobile phase. The punching of blood spots and the offline extraction is time-consuming and labor-intensive. Additionally, there is a high waste of consumables and it is not suitable for high throughput applications.
The manual DBS process involves several steps: First all vials need to be labeled according to the sample information, also this information needs to be entered the sample list on the LCMS. Then, discs are punched and transferred into a vial. The extraction takes usually 30 minutes to 4 hours (4 h; e.g. PEth). Afterwards, the supernatant is transferred into a HPLC vial and loaded into the autosampler. Besides pipettes, the manual processes need many tools such as a shaker, a centrifuge, and an evaporators.
Example of a DBS after the extraction with the CAMAG DBS-MS 500 (spot 1-3, 6 mm head) and after punching (spot 4). With the automation, the connection between the card and the extracted area remains intact. Due to individual barcodes printed on the cards and photographic documentation, a sample mix-up is not possible. DBS are always extracted from the center of the blood spot.