High-throughput automatic flow method for determination of trace concentrations of aluminum in dialysis concentrate solutions using salicylaldehyde picolinoylhydrazone as a turn-on fluorescent probe

• Aroylhydrazone turn-on fluorescent probe for Al(III) in saline solutions.
• Hybrid flow system for high throughput analysis of dialysis concentrates.
• High sensitivity for Al(III) detection without prior sample preconcentration.
• Quantification limit below the maximum allowed concentration of Al(III) in dialysis concentrates.

A simple and expedient flow-based assembly capitalizing on programmable flow is herein proposed for reliable determination of trace level concentrations of aluminum as a potential contaminant in dialysis concentrate solutions without any prior sample clean-up/preconcentration procedure. Using salicylaldehyde picolinoylhydrazone in weakly acidic media as a turn-on fluorescent probe, the manifold is devised to handle three samples concurrently in stopped-flow reaction mode for simultaneous improvement of the analytical sensitivity and sample throughput.Analytical parameters influencing the sensitivity and repeatability of the assays, namely, probe concentration, reaction temperature and reaction time were investigated using a multivariate optimization protocol composed of a full factorial screening design followed by a Doehlert matrix model. The analysis of the Pareto chart and surface response revealed that the reaction time and amount of fluorescent probe were critical parameters for reliable assays of aluminum at the low ng mL−1 level.Under the optimized chemical and physical variables, a detection limit of 1.1 ng mL−1 Al(III) at the 3sblank level, relative standard deviations better than 1.0%, a dynamic linear range of 5.0–80 ng mL−1 and a sample throughput up to 25 h−1 were obtained with no need for either sample preconcentration or the use of organized supramolecular systems. Demonstrated with the analysis of hemodialysis and peritoneal concentrate solutions, and dialysis waters, the flow-through method copes with the requirements of regulatory bodies (e.g., European Pharmacopeia) for quality control of aluminum in high salinity containing dialysis concentrates.

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