Combination analytical instruments are classified according to their principal function or, where that cannot be determined, under the HTS heading that appears last in numerical order among the applicable headings. For LC-MS systems, the classification outcome can differ depending on whether the mass spectrometer or the chromatograph is considered the primary analytical component. Importers should seek a CBP binding ruling for high-value combination systems to avoid reclassification risk.

FDA jurisdiction over analytical instruments depends on intended use: instruments marketed for clinical diagnostic purposes (e.g., in vitro diagnostic devices) are regulated as medical devices and require premarket clearance or approval. Research-use-only (RUO) instruments sold without diagnostic claims generally fall outside FDA's device regulatory framework, though labeling must clearly reflect the RUO designation to avoid regulatory scrutiny at entry.