On-site analysis of gold, palladium, or platinum in acidic aqueous matrix using liquid electrode plasma-optical emission spectrometry combined with ion-selective preconcentration

A technique for the concurrent on-site quantitative analysis of gold (Au), palladium (Pd), or platinum (Pt) in the aqueous acidic matrix has been proposed. The Au, Pd, or Pt in the matrix was selectively concentrated in macrocycle-equipped solid-phase extraction (SPE) system, followed by analysis of the concentrates in a portable liquid electrode plasma-optical emission spectrometer (LEP-OES). The SPE-retention or recovery behavior towards Au, Pd, or Pt has been optimized for solution pH, sample-loading flow-rates, eluent-type or eluent-volume, and matrix components. The SPE-assisted pre-treatment minimized interfering impacts due to the competing ions in solution and limitations in LEP-OES sensitivity at low Au, Pd, or Pt content in the matrix. The preconcentration factor was 250 for Au, Pd, or Pt. The LEP-OES operating variables such as applied voltage, on-time, off-time, and pulse count for applied voltage have been optimized to obtain distinct peaks in spectra for Au (λmax, 274.826 nm), Pd (λmax, 267.958 nm), and Pt (λmax, 270.240 nm). The limit of detection (3σ) for Au, Pd, Pt determination using the technique were found, respectively, as 0.8, 3.1, 57.3 ng mL−1. The proposed method was applied to the analysis of Au, Pd, or Pt contents in the European Commission Joint Research Center certified reference material of wastewaters (ERM-CA713; recovery by the standard addition method, >96%), and real aqueous waste from the plating process (recovery, >95%). A relative standard deviation of ≤ 5% indicated a good precision in Au, Pd, or Pt analysis using the technique. The LEP-OES data-sets were also comparable with those obtained from the inductively coupled plasma optical emission spectrometric measurements for the same matrix.