First experience with a fully automated extraction system for simultaneous on-line direct tandem mass spectrometric analysis of amino acids and (acyl-)carnitines in a newborn screening setting.

RATIONALE: For Newborn Screening (NBS) programs all over the world whole blood dried on filter paper, also referred to as dried blood spots (DBS), has been the standard specimen for decades. In recent years DBS have attracted the attention of pharmaceutical companies, mostly due to the low volume of collected sample and simplified, therefore more cost-efficient, transportation requirements. However, the classical NBS workflow did not totally fulfil the needs of their studies, especially with respect to high-throughput unassisted sample processing for tandem mass spectrometric (MS/MS) analysis. Automated on-line extraction systems for direct analysis have already been tested and proved to be suitable for these pharmaceutical applications.

METHODS: The suitability of the automated CAMAG DBS-MS 500 interface for simultaneous detection of amino acids and (acyl-)carnitines has been tested together with an Acquity TQD tandem mass spectrometer from Waters and MassChrom stable isotope labelled internal standards from Chromsystems. No chromatographic sample treatment was applied; instead, the extract was directly injected into the MS/MS instrument. The feasibility of the instrumental setting for the routine newborn screening was tested on original samples coming from previously diagnosed patients.

RESULTS: The performance of the automated extraction technique and its application in preliminary quantitative screening for amino acids and (acyl-)carnitines for NBS showed very promising results. Several samples from patients, each diagnosed with one of four different inborn errors of metabolism (IEM), were tested and the correlation with the conventional punch-and-elute approach was very good.

CONCLUSIONS: Although the presented method still needs further optimization, our study clearly shows the possibility to use direct on-line analysis in the NBS setting. Our report on direct on-line analysis of newborn samples is a first approach in the development of a fully automated screening method for NBS analysis. With regard to the chemical properties of the analytes, the study resulted in a readily applicable screening method.