Chromatographic behavior of cadmium in an ion-pair reversed-phase micro HPLC system and its application to the determination of bio-available cadmium in soil samples

Abstract

A novel reversed phase ion-pair micro HPLC system with on-line fluorescence detection has been developed systematically and studied for the determination of cadmium in its bio-available fractions of soil samples. In this system, a micro ODS column of 1.0 mm i.d.x150 mm length and a mobile phase containing 6 mmol L(-1) 8-hydroxyquinoline 5-sulphonic acid (HQS), 3 mmol L(-1) cetyltrimethylammonium bromide (CTMABr), 10 mmol L(-1) acetic acid-acetate buffer (pH 5.1) as well as 50% acetonitrile at 50 microL min(-1) flow rate were employed to determine cadmium with a 2 microL flow cell through its fluorescence at 518 nm under 338 nm excitation. Furthermore, the composition of Cd-HQS chelate formed on the column was confirmed to be [Cd(HQS)(2)](2-) through a log-log plot method, and then combined with the ion-pair reagent by the electrostatic force under the chromatographic condition proposed. With such a method, the detection limit of cadmium was 8.48 ng mL(-1) (3sigma) with 1 microL sample injection, and the linear range for the determination of cadmium was 30-800 ng mL(-1) (R(2)=0.992). This method has been successfully applied to determination of cadmium in its bio-available fractions of BCR-483 and soil samples without interference from other coexistent metal ions. The RSD (n=6) was less than 7.3%. The results were in agreement with the indicative value for BCR-483 and those for the soil samples obtained by ICP-MS with a pretreatment of bis(1,1,3,3-tetramethylbutyl) phosphinic acid extraction.

Bioaccumulation and transformation of cadmium by Phaeodactylum tricornutum

“…The concentration of free metal ions depends on the total concentration of dissolved metal, as well as the type and concentration of the concurrent ligands in the environment [19] . According to the complex stability constants between Cd and EDTA and/or Cys, one can calculate the concentration of Cd 2+ under different concentrations of EDTA and Cys [20] . The distribution coefficients and concentrations of free Cd 2+ under different molar ratios of EDTA and/or Cys to Cd, with the Cd T at 500 μg/mL or 10 mg/L, are listed in Table 1.…”