Calibration vs verification

You said you don't do outside calibrations. As a testing laboratory however, you need external calibration by competent parties to ensure metrological traceability. For example, the analytical balances.

You asked why the adjustment of instruments is not included in clause 7.4. Note that clause 7.4 deals with handling of test or calibration item (after the sampling step) and is applicable for laboratories handling items to be tested (testing laboratories) or calibrated (calibration laboratories).

It is clause 6.4 which deals with the requirements for equipment, including calibration of any equipment which can influence the validity or results generated (whether a test or calibration result). Here clause 6.4 requirements must be met for all equipment in the process, which in includes for example the components of the ICP, the standard used for the calibration curve and volumetric measuring devices used.

For more information and links to resources, see my reply to the question Equipment qualification at https://community.advisera.com/topic/equipment-qualification/