42 BIOTECHNOLOGY
Fig. 2. A new gripping tool had to be developed which even keeps bent cardboard cards stable and accurate in position.
them in a sample loop / trapping column and further evaluating them in a LC-MS system. In collaboration with partners we have successfully performed direct extraction/analysis of several thousand samples.
■ Wash station. Direct extraction parts are in contact with the actual blood spots and therefore possible carryover has to be observed carefully. An automatic wash station was constructed to control carryover. In all cases the desired carryover level of 10E-4 or around LOD has been reached. Te automation of all above-mentioned steps will significantly reduce uncontrolled effects originating from the extraction process of DBS-cards.
First tests confirmed that excellent reproducibility as well as minimal carryover can be achieved.
Te automation of the entire extraction process for up to 500 DBS-cards is a very welcome simplification for performing DBS analysis and contributes to the improvements in reproducibility and reliability.
Conclusions Our tests with semi-automated and automated DBS systems confirmed that with increasing automation of the DBS analysis the three factors addressed in this project gain in importance and should be considered as key issues:
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Fig. 3. Continuous handling tests with up to 1000 card transport cycles have been performed successfully.
■ In practice we observed positioning variations of the blood spots relative to the DBS card boundaries of up to 3mm due to the blood spotting procedure and card tolerances. An automated system which does not detect those variations will miss part of the spot in such a situation. Tis would be unacceptable in routine analysis and accurate spot localization seems to be a must.
■ All parts in contact with the DBS sample are potentially contributing to carryover. We experienced that for critical applications an automated wash system can be used to reduce or eliminate the remaining carryover after every sample.
■ Normalisation of data by an internal standard has been found to be one of the key issues. Furthermore the application of the internal standard to the DBS card after blood spotting but prior to extraction seems to be favoured logistically and will have the potential to correct for extraction efficiencies.
Enter 42 or ✔ at
www.scientistlive.com/eurolab Matthias Loppacher, Christoph
Fankhauser, Klaus Schetter and Urs Schranz are with CAMAG, Muttenz, Switzerland.
www.camag.com.
Manuel Altmeyer, Agathe Koller, Bettina Mueller and Silvio Walpen are with the Institute for Laboratory Technology, Rapperswil, Switzerland
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