Optimisation of a Flow Injection System with a Piezoelectric Quartz Crystal Detector for the Determination of Inorganic Mercury

ABSTRACT

A new method combining flow injection methodology with quartz crystal microbalance (QCM) detection is proposed for inorganic mercury analysis. A modified simplex method is used in order to maximise the observed analytical signals (crystal frequency decrease). Six parameters were optimised: the concentration of the acidic carrier solution, the lengths of the sample loop and mixing coil, and the flow rates of the sample carrier, the reductant stream (SnCl₂), and the carrier of the mercury vapour (N₂). An increase of 18% in the signal of the centroid of the calibration line was achieved, as well as an increase in the sensitivity from 290 Hz μg⁻ to 313 Hz μg⁻. Following the proposed procedure, detection limits of 47 μg L⁻ of inorganic mercury were found for sample volumes of 0.5 mL.

Keywords::

• Quartz crystal microbalance
• Piezoelectric crystals
• Mercury
• Simplex method