Abstract: Endpoint error (E_t) represents a critical concept in analytical chemistry education. Conventionally, the difference (E_In) between an indicator's theoretical color transition point and the stoichiometric point has been regarded as the exclusive source of endpoint error. This study introduces an additional source of endpoint error—E_ld, arising from the last drop of titrant during practical titration operations. This systematic error exhibits positive values with inherent uncertainty within a defined range. We comprehensively analyze the impact of this error on overall endpoint error and re-examine the interrelationships among titration jumps, endpoint error, and indicator transition points. These findings provide enhanced theoretical guidance for optimizing titration conditions and improving measurement accuracy.

Key words: Titration analysis, Endpoint error, The last drop, Titration jump, Error analysis