A fully integrated LC-MS system is classified as a whole according to its principal function or, if that cannot be determined, under the subheading that appears last in the tariff schedule. In practice, CBP has generally classified integrated LC-MS systems under the mass spectrometer subheading (902781) when the MS is the defining analytical component, but the specific configuration and manufacturer documentation matter. A binding ruling is advisable for high-value integrated systems.

Consumable HPLC columns are generally classified as parts or accessories of chromatographs under 902790 when they are identifiable as designed for instruments of this heading. However, some columns may be classified elsewhere if they are considered chemical preparations rather than instrument parts. Detector cells and flow cells designed for specific analytical instruments are more clearly parts under 902790. The article's design specificity and whether it is a consumable versus a durable component are the key factors.