Determination of soil calcareous efficiency using flow system with pervaporative separation

A method is described for the conductimetric determination of CO2. The proposed system was constructed with a pervaporator chamber coupled to a flow system comprised of a sixway solenoid valve, a conductivity cell, a conductivimeter and a PC microcomputer for data acquisition and external controls. An amount of 2g of dry soil samples were directly weighted in the donor compartment of the pervaporation chamber. The CO2 was determined from an analytical curve within 5.0?10-3-5.0?10-2molkg-1 CaCO3. This curve was constructed with the matrix matching approach and presented a linear regression of y=13.58+584.77r (r= 0.9962). Soils with different lime amounts were analyzed by the proposed methodology and with the official method, that uses the calcium difference between the total, extracted with HCl 1moll-1 and exchangeable, extracted with the KCl 1moll-1. After paired t-test application, no significant difference between the methods was found at the 95% probability level. The proposed method presented sampling rate of 17h-1, detection limit of 8.0?10-4 molkg-1 CaCO3, and R.S.D.<3%. The use of the pervaporator allowed the in situ soil pretreatment for the residual lime determination.