Comprehensive instrumental analysis methods

Thanks to the introduction of highly sensitive ion trap and TOF mass analysers in GC/MS and LC/MS full-scan positive and negative ion data of the residues and contaminants in a particular sample of interest can be easily obtained, provided that the analytes are effectively extracted and survived the clean-up step, the injection, chromatographic separation and ionization. Then the sky is the limit and hundreds of residues and contaminants can be searched for. QA/ QC considerations will require the co-analysis of control samples, and then particularly the preparation of a non-compliant control sample having a known concentration of all analytes of interest will be a huge task. The co-analysis of such a control sample will be crucial for the assessment of false compliant results, especially because in the end automated raw data processing and evaluation will be the only option to handle the screening for hundreds of residues and contaminants. It should be noted that state-of-the-art raw data processing and evaluation software will function quite well in academic standards but most often fail in real samples at residue or contaminant level.

Considering validation of the total analysis including data processing it might be questioned whether the immense efforts of a full validation for all these hundreds of analytes in all sample matrices of interest is really required. In analogy with Section 6.1 a set of a limited number of representatives might be chosen for an initial in-house validation covering a range of physicochemical analyte characteristics and/or contaminant (sub)groups. Ideally, the choice of these representatives should be validated by performing at least a within-day replicate analysis experiment of blanks and control samples containing all analytes of interest. Additional contaminants of interest might be added to the control sample during routine operation thus providing a continuous extension of the scope of the method.

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