Chromium Speciation in Water Samples by Loading a New Sulfide-Containing Biodegradable Polymer Adsorbent in Tip of the Syringe System

A new adsorbent poly-3-hydroxybutyrate-2-(dodecylthiocarbonothioylthio)-2-methylpropionate triester (PH-DTT-MPT) was first time loaded in a micropipette tip for speciation of chromium in different water samples. Total chromium (Cr), trivalent chromium (Cr^III), and hexavalent chromium (Cr^VI) in different natural water samples were determined by electrothermal atomic absorption spectrometry. Known concentration of Cr^III and Cr^VI was passed through a biodegradable polymer for investigation of the behavior of the newly used adsorbent. The newly used copolymer absorbed the Cr^III on surface of the PH-DTT-MPT at pH 7.0, while Cr^VI was not adsorbed in desired pH value. After passing the real and standard solutions through the micropipette, then 2.0 mol L⁻¹ HCl was used for elution of Cr^III from the biodegradable polymer. Total Cr was calculated after reducing Cr^VI into Cr^III by specific concentration of hydroxy ammonium chloride (HONH₂·HCl). The concentration of Cr^VI in different natural water samples was estimated after back calculation of Cr^III from total chromium. Effect of analytical parameters like adsorbent, pH, eluent, sample volume, flow rates, and interfering ions was also studied. The LOD, LOQ, RSD, and EF of the developed method were calculated as 6.1 ng L⁻¹, 20 ng L⁻¹, 1.17%, and 90, respectively. Validation of developed method was checked by certified reference materials and spiking addition method. The developed method was successfully applied for determination of total Cr, Cr^III, and Cr^VI in various natural water ecosystems.