Pyrrolizidine alkaloids (PAs) are a chemically diverse group of plant-derived toxins whose quantification in botanical materials remains analytically challenging. This study integrates previously established nano zirconium silicate (NZS) enrichment with one-pot lithium aluminium hydride reduction/hydrolysis and LC–HRMS determination of the resulting necine-base response. The workflow targets retronecine- and heliotridine-type PAs and their N-oxides, with results expressed as retronecine equivalents. In Radix Primulae, three independent samples were spiked at each of 200, 250 and 300 µg/kg retronecine equivalents and processed through the complete analytical workflow. Mean recoveries were 83.0%, 94.2% and 92.5%, with between-preparation RSDs of 3.12%, 1.55% and 1.96%, respectively. Matrix-matched regression was evaluated using six calibration levels (10, 100, 200, 300, 400, 500; Day-1 R² = 0.99936). Calculated Day-1 LOD and LOQ estimates were 14.94 and 45.27 µg/L. Remeasurement of the same extracts after 24 h, using a separate daily calibration, gave paired concentration changes of −0.67% to +1.23%. Application to a naturally contaminated comfrey sample demonstrated the workflow’s applicability beyond spiked samples, with agreement between the conversion-based result and the summed intact-PA reference approach.