Optimization of species stability and interconversion during the complexing reaction for chromium speciation by high-performance liquid chromatography with inductively coupled plasma mass spectrometry

Abstract

High-performance liquid chromatography coupled with inductively coupled plasma mass spectrometry was employed for the determination of chromium species. For simultaneous separation of both chromium species by an anion-exchange column, ethylenediaminetetraacetic acid was induced to form negatively charged complex with Cr(III) normally. Cr(III) chelating reactions are known to be slow, so a high temperature and long reaction time are needed to ensure the completion of the complexing reaction. However, the stability and interconversion of chromium species during the complexing reaction have not been studied earlier. The main aim of this work was to optimize and investigate complexing reaction conditions between ethylenediaminetetraacetic acid and Cr(III). Through optimizing conditions, the reaction will be finished completely in 15 min at pH 7 and 70°C without any obvious interconversion between Cr(VI) and Cr(III). By compromising analysis time, chromatographic resolution, and sensitivity, 60 mM NH4 NO3 as competing ion concentration and 1.2 mL/min as flow rate have been selected for real-sample application. Detection limits for Cr(VI) and Cr(III) were 0.051 and 0.078 μg/L, respectively. The proposed method was used for the determination of chromium species in tap and surface water samples with an acceptable range of spiked recoveries of 95-109%.

Design and synthesis of a novel chromium(III) selective fluorescent chemosensor bearing a thiodiacetamide moiety and two rhodamine B fluorophores

“…Many traditional analytical techniques, such as solid-phase extraction [22], high-performance liquid chromatography (HPLC) [23] and inductively coupled plasma atomic emission spectrometry (ICP-AES) [24], have been reported for the determination of Cr 3+ ions in various media. However, the major disadvantages of these methods include the demand for expensive and complex apparatus along with complicated sample pretreatments in these time-consuming processes [25,26].…”

Simultaneous speciation and determination of arsenic, chromium and cadmium in water samples by high performance liquid chromatography with inductively coupled plasma mass spectrometry

“…As a strong chelating agent, EDTA is able to form complexes with many major and trace ions present in environmental water, including Al(III), Ba(II), Ca(II), Cd(II), Co(II), Cr(III), Cu(II), Fe(II), Fe(III), Mg(II), Mn(II), Ni(II), Pb(II), Sr(II) and Zn(II). 23 The complexation of cations with EDTA for standard solutions was achieved by adding the appropriate amounts of Cr(III), Cd(II), EDTA and phosphate buffer pH adjusted to 7 into a 15 mL glass tube, then incubating in a water bath set to at 70ºC for 15 min to ensure the formation of metal-EDTA complex with the great efficiency. Normally, the concentration of potentially competing ions is subject to a wide natural variability.…”

“…21,26 And some of the complexes have high stability constants, which will interfere in complexation of target ions. 22,23 26 Therefore, excess EDTA is needed for the treatment of real samples to ensure complete complexation of Cd(II) and Cr(III) in surface and drinking waters and enable metal-EDTA complexes to remain stable during chromatographic separation.…”

“…Cadmium exposure may result in bioaccumulation in the kidneys and liver 11 and has a close association with the development of diabetes and diabetes-related kidney diseases. [21][22][23] There are few reports on the simultaneous speciation and detection of metal(loid)s and metal-EDTA complexes using HPLC-ICP-MS 21 . 13 High performance liquid chromatography (HPLC) coupled to elemental specific detectors, such as inductively coupled plasma mass spectrometry (ICP-MS), has been much used in simultaneous detection and speciation of different elements because of the separation versatility, high sensitivity, element specificity and ease for online coupling.…”

Atomic Spectrometry Update: review of advances in elemental speciation

“…This implies that baseline noise increased aer elution of the Cr-EDTA complex as the sensitivity (signal to analyte amount) increased for the Cr 2 O 7 2À ion. 102 To achieve this, Cr III present in the samples was complexed with EDTA, 2 mmol L À1 , at pH 7.0 and 70 C to form an anionic species. Method trueness was assessed by spiking experiments of up to 2 mg L À1 added Cr, as no suitable species specic CRM was available, and spike recoveries ranged from 93 to 115%.…”