Which feature characterizes GC-MS confirmation in comparison to immunoassay screening?

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GC-MS confirmation relies on definitive, instrument-specific criteria to identify a compound: the retention time must match that of an authentic standard under the same chromatographic conditions, and the mass spectrum must show a characteristic set of fragment ions. This combination provides a highly specific fingerprint that confirms the substance, not just indicates its possible presence. Immunoassay screening, on the other hand, depends on antibody–antigen interactions and can be affected by cross-reactivity, leading to possible false positives and no definitive identity. Because confirmation requires comparing both retention time and the actual fragmentation pattern to verified standards, standards are essential in GC-MS to establish accurate reference points. The idea that no standards are needed for confirmation is therefore incorrect. In short, the hallmark of GC-MS confirmation is using retention times plus instrument-specific fragment ion information to definitively identify compounds, offering far greater specificity than screening immunoassays.