Direct determination of total carbonate salts in soil samples by continuous-flow piezoelectric detection

Two new methods for the determination of total carbonate salts, as CaCO3, in soil by continuous-flow piezoelectric (PZ) detection are proposed. Both use a piezoelectric flow cell and a manifold including a dynamic gas extraction device to purge gaseous CO2 released by the sample solution upon acidification. One of the methods involves monitoring the pressure generated by the CO2 produced upon addition of hydrochloric acid; in the other, the CO2 is quantified by using a quartz crystal coated with tetramethylammonium fluoride tetrahydrate (TMAF). The precision of both methods is compared with that of the officially endorsed method. The proposed methods allow calcium carbonate amounts over the ranges 10–100 mg and 2–15 mg, respectively, to be determined. Both were applied to the determination of CaCO3 in soil samples. The standard deviation and throughput achieved were 2.7% and 30 samples per hour, respectively, with the pressure-based method; and 6.0% and six samples per hour, respectively, with the mass-based method.