Simultaneous enrichment & on-line detection of low-concentration Copper, Cobalt, & Nickel Ions in Water by Near-Infrared diffuse reflectance spectroscopy combined with chemometrics

Sensitive detection of heavy metal ions in water is of great importance considering the effects that heavy metals have on public health. A developed fluidized bed enrichment technique was used to concentrate and detect low concentrations of Cu²⁺, Co²⁺, and Ni²⁺ in water samples by near-IR diffuse reflectance (NIDR) spectroscopy (NIDRS) directly without using any chemicals or reagents. The NIDR spectra of adsorbent were measured on-line, and quantitative detection was achieved by applying a built partial least-squares chemometric model. Sensitivity and accuracy was improved significantly because large-volume mixture solutions were used in the enrichment process. Root mean square error of cross-validation values for Cu²⁺, Co²⁺, and Ni²⁺ were 0.29, 0.41, and 0.35 μg/mL, respectively, with mean relative error values in the acceptable range of 6.56-10.27%. This study confirms the potential application of fluidized bed enrichment combined with NIDRS and chemometrics for the simultaneous detection of trace heavy metal ions in water, with low relative error.