Design and characterization of a new dialysis chamber for investigating dissolved organic matter-organic complexes

Equilibrium dialysis is commonly used to measure the complex formed between dissolved organic matter (DOM) and pesticides such as napropamide [2(alpha-naphthoxy)-N,N-diethyl propionamide]. Currently the dialysis method most often used employs dialysis tubing that is clamped on both ends. Limitations of the dialysis tubing method include difficulty in sample addition to the dialysis tubing, dilution effects, and the need for large sample volumes. A new dialysis chamber constructed of Teflon and using fiat dialysis membranes is described and characterized using napropamide as a model compound. Using a dialysis membrane with a molecular weight cut off of 500 Daltons the system reached equilibrium across the membrane within 120 h. Significant sorption of napropamide to the membrane was observed. Napropamide sorption was linear, reversible, and dependant on the membrane used. Sample addition and removal from the chamber is possible without destroying the integrity of the membrane. The dialysis chamber allowed for fast and easy quantitative addition and removal of sample for dialysis without wasting sample. The small chamber made possible dialysis of very small samples (as little as 1.5 mL) while maintaining a large surface area for diffusion. The chamber also provided dialysis with a maximum dilution factor of two since the volume of dialysate needed is equal to the volume of sample introduced.