Exploitation of tandem streams for carry-over compensation in flow analysis I. Turbidimetric determination of potassium in fertilizers

Tandem flow is the essence of a novel modality of flow analysis. This unique stream initially comprises several neighboring slugs of miscible solutions that undergo fast mixing while flowing through the analytical path. When overlap of the slugs is partial, the identity of the initial slugs can be preserved although with some carry-over. If to each slug corresponds a processed sample zone, carry-over can be efficiently exploited. Carry-over exploitation as means to enhance sampling rate and/or reagent consumption is demonstrated in designing an improved turbidimetric determination of potassium in fertilizers using sodium tetraphenylboron. Sampling rate undergoes a remarkable increase and other favorable characteristics are maintained. Potentialities and limitations of the approach as well as dependence of measurement repeatability on the carry-over degree are discussed.