Automation of Liquid–Liquid Extraction–Spectrophotometry Using Prolonged Pseudo-Liquid Drops and Handheld CCD for Speciation of Cr(VI) and Cr(III) in Water Samples

Abstract

A simple spectrophotometric system, based on a prolonged pseudo-liquid drop device as an optical cell and a handheld charge coupled device (CCD) as a detector, was constructed for automatic liquid-liquid extraction and spectrophotometric speciation of trace Cr(VI) and Cr(III) in water samples. A tungsten halogen lamp was used as the light source, and a laboratory-constructed T-tube with two open ends was used to form the prolonged pseudo-liquid drop inside the tube. In the medium of perchloric acid solution, Cr(VI) reacted with 1,5-diphenylcarbazide (DPC); the formed complex was automatically extracted into n-pentanol, with a preconcentration ratio of about 5. The organic phase with extracted chromium complex was then pumped through the optical cell for absorbance measurement at 548 nm. Under optimal conditions, the calibration curve was linear in the range of 7.5 -350 µg L -1 , with a correlation coefficient of 0.9993. The limit of detection (3σ) was 7.5 µg L -1 . That Cr(III) species cannot react with DPC, but can be oxidized to Cr(VI) prior to determination, is the basis of the speciation analysis. The proposed speciation analysis was sensitive, yet simple, laboreffective, and cost-effective. It has been preliminarily applied for the speciation of Cr(VI) and Cr(III) in spiked river and tap water samples. It can also be used for other automatic liquid-liquid extraction-spectrophotometric determinations.

Ultratrace Determination of Cr(VI) and Pb(II) by Microsample Injection System Flame Atomic Spectroscopy in Drinking Water and Treated and Untreated Industrial Effluents

“…The results showed that the extraction time for proposed DLLME is short (5–10 sec). The enrichment factors, LODs and %RSDs of DLLME, are comparable with those reported in the literature [22, 25–37]. The proposed methods (DLLME and CECP) coupled with MIS-FAAS are simple, most sensitive, and selective.…”

“…Ammonium pyrrolidine dithiocarbamate (APDC) has been used as a selective chelating agent for Cr(VI) and Pb(II) [22, 23]. The applicability of DLLME coupled with microsample injection system flame atomic absorption spectroscopy for Cr(VI) and Pb(II) preconcentration and separation was adopted as evaluated in our previous work [24].…”

Optimisation and application of the voltammetric technique for speciation of chromium in the Patos Lagoon Estuary—Brazil

“…Because of its importance, chromium chemical speciation analysis has been widely studied, and several analytical techniques has been suggested to do it, such as atomic absorption spectrometry with electrothermal atomisation (Zhu et al 2005;Krishna et al 2005;El-Shahawi et al 2005;Blas et al 2007), inductively coupled plasma mass spectrometry (Chen et al 2007;Krishna et al 2005), inductively coupled plasma optical emission spectrometry (Menegario et al 2005;Parodi et al 2005;Sumida et al 2005;Gil et al 2005) and fluorescence spectrometry (Chen et al 2005). However, the adsorptive cathodic stripping voltammetry (AdCSV) is a technique as sensitivity as versatile and can be applied to different environmental matrix, and it is also adequate to chemical speciation analysis.…”

Sorption of Cr(VI) by Amberlite XAD-7 resin impregnated with brilliant green and its determination by quercetin as a selective spectrophotometric reagent

“…Several methods have been described for the separation and determination of Cr(VI) ions including, solvent extraction [1], coprecipitation [2], and solid phase extraction [3][4][5][6]. Solid phase extraction is one of the wellknown preconcentration/separation techniques for this purpose [7][8][9][10].…”