In this work, a simple, economic, and miniaturized flow-based analyzer based on solenoid micropumps is
presented. It was applied to determine two parameters of high environmental interest: ammonium and
total inorganic carbon (TIC) in natural waters. The method is based on gas diffusion (GD) of CO2 and NH3
through a hydrophobic gas permeable membrane from an acidic or alkaline donor stream, respectively.
The analytes are trapped in an acceptor solution, being slightly alkaline for CO2 and slightly acidic for
NH3. The analytes are quantified using a homemade stainless steel conductimetric cell. The proposed
system required five solenoid micro-pumps, one for each reagent and sample. Two especially made air
bubble traps were placed down-stream of the solendoid pumps, which provided the acceptor solutions,
by this increasing the method's reproducibility. Values of RSD lower than 1% were obtained. Achieved
limits of detection were 0.27 mmol L1 for NH4
þ and 50 mmol L1 for TIC. Add-recovery tests were used
to prove the trueness of the method and recoveries of 99.577.5% were obtained for both analytes. The
proposed system proved to be adequate for monitoring purpose of TIC and NH4
þ due to its high sample
throughput and repeatability.