Tandem battery-operated on-site dithizone-functionalized C18 cartridge micro-solid phase extraction system and...

A tandem battery-operated on-site dithizone-functionalized C18 cartridge micro-solid phase extraction and ex-situ small-sized electrothermal vaporization capacitively coupled plasma optical emission spectrometry (μ-SPE-SSETV-μCCP-OES) was developed for river water processing and simultaneous determination of Cd(II), Cu(II), Pb(II) and Zn(II). The cartridge was characterized in terms of loading capacity, short-term stability during use in terms of dithizone oxidation and leaching in effluent and long-term storage until use and retention capacity of metals. A roll-up phenomenon and a decrease in the retention capacity of the cartridge for Zn(II) < Cd(II) < Pb(II) in the presence of Cu(II) were observed. The effects of parameters that influence the preconcentration/elution from cartridge were optimized and validated by ANOVA and Tukey's test (p < 0.05). The interelement and matrix effects caused by humic acid, ionic strength and Co, Ni, Hg traces contained in the natural waters on the preconcentration of metal ions were investigated. The μ-SPE system was on-site implemented for river water processing by powering from a photovoltaic-charged battery and involved the preconcentration of metals from 200 mL sample at 10 mL min^-1 and elution in 2 mL of 0.2 mol L^-1 thiourea in 1 mol L^-1 HNO₃ at 0.5 mL min^-1, followed by determination in eluate using the ex-situ battery-operated SSETV-μCCP-OES setup with recoveries of 91-108% and detection limits of 0.4-3.50 ng L^-1. The method exhibited a greenness of 60% and a redness/greenness/blueness/whiteness degrees of 92/68/91/84%, evaluated by AGREEprep and RGB 12 metrics, superior to conventional laboratory-based spectrometric methods.