Origin of the Lag Phase of Continuous-Flow Analysis Curves

Physical and mathematical models are presented that account for the lag phase in the curves of transition between steady states in continuous-flow analysis. Experimental conditions are described that produce pure lag-phase curves, separated from the exponential phase with which they are combined in routine practice. The data quantitatively support the expectations from the models, and provide a means for measuring interslug transfer of fluid in bubbled streams. Others observed earlier that lag phase is associated with the bubbled stream and the dialyzer, whereas the exponential phase is associated with nonbubbled streams and debubbler [Clin. Chim. Acta 27, 421 (1960)]. Our theory and experiments confirm these earlier observations, and may provide deeper understanding of the processes involved in, and design requirements for, continuous-flow analysis.