Luminometric label array for quantification of metal ions in drinking water – Comparison to human taste panel

A novel microtiter plate array for the quantification and identification of metal ions in drinking water was compared to human taste panel analysis. The array is based on nonspecific interactions between analyte metal ions and lanthanide chelates with non-antenna and antenna ligands, leading to a luminescence signal profile unique to sample components. The performance of the method was demonstrated in the detection of Cu2+ and Fe2+ ions in active coal filtered and nonfiltered household water. The sensitivity and objectiveness was compared to human taste panel analysis. Detection limits of <2 μg/L in both active coal filtered and nonfiltered household water for Cu2+ and 20 μg/L in active coal filtered and 30 μg/L in nonfiltered household water for Fe2+ were achieved with the developed array. The average coefficient of variation for replicates in the dynamic range was 6 and 4% for Cu2+ and Fe2+, respectively. High repeatability and objectiveness was shown, as the average coefficient of variation for the repetitions of the array with chosen modulators was 12%. Mass percentages of Cu2+ and Fe2+ ions were also determined when the total concentrations of analyte ions were known, showing the applicability of the array for mixture analysis. Sensory evaluation and discrimination testing of spiked Cu2+ and Fe2+ samples was applied to study the detection limit of human sense of taste. From total 39 subjects, 35% were sensitive enough in lowest concentrations (10 μg/L for Cu2+ and 5 μg/L for Fe2+) and able to separate taste stimuli from plain household water sample, but high variation between individual thresholds was observed. The results show that human individuals may be sensitive enough to detect excess Cu2+ and Fe2+ in household water, but sensitive instrumental methods are needed.