Oxidation State-Differentiated Measurement of Aqueous Inorganic Arsenic by Continuous Flow Electrochemical Arsine Generation Coupled to Gas-Phase Chemiluminescence Detection

Abstract

The electrochemical reduction of inorganic As on a graphite cathode depends on the current density. We observed that while only inorganic As(III) is reduced to AsH(3) at low current densities, at high current densities both forms of inorganic As are reduced. We describe a unique electrochemical reactor in which the cylindrical anode compartment is isolated from the outer concentric cathode compartment by a Nafion tube in which a hole is deliberately made and the entire anode compartment is inside the cylindrical cavity of a small volume (∼115 μL) cathode chamber. The evolved arsine is then quantitated by gas-phase chemiluminescence (GPCL) reaction with ozone; the latter is generated from oxygen formed during electrolysis. For the dimensions used, inorganic As(III) can be selectively determined at a current of 0.1 A while total inorganic As (both As(III) and As(V)) respond equally at an applied electrolysis current at 0.85 A, without any sample treatment. For a 1-mL sample, the system provides a limit of detection (LOD, S/N = 3) of 0.09 μg/L for total As (i = 0.85 A) and an LOD of 0.76 μg/L for As(III) (i = 0.10 A); As(V) is obtained by difference. Comparison of ICP-MS results for total As in groundwater samples that span a large range of concentration and total inorganic As determined by the present method showed a high correlation (r(2) = 0.9975) and a near unity slope. The basic electrochemical arsine generation technique and current-differentiated oxidation state speciation should be applicable as the front end to many other arsenic measurements techniques, including atomic spectrometry.

Electrochemical generation of arsenic volatile species using a gold/mercury amalgam cathode. Determination of arsenic by atomic absorption spectrometry

“…High hydrogen over-voltage cathode materials are more prone to interferences but are more efficient and more versatile in regards to hydride formation. Unfortunately, some of these cathodes present low mechanical stability and therefore must be periodically replaced [19].The search for a convenient cathode material for EcHG with high hydrogen over-voltage, acceptable freedom from interference and sufficient mechanical stability, is still on. Electrochemical arsine generation is well documented in the literature [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37].…”

Gas-phase chemiluminescence of reactive negative ions evolved through corona discharge in air and O2 atmospheres

“…9 Among the different CL systems, acting as a classic and convenient strategy, gas-phase CL (especially ozone-based CL) has recently been a rapidly growing eld. 10,11 However, no articles have reported the CL effect of negative ions, which remains a great challenge. Here, the emissive performance of negative ions evolved in air and O 2 atmospheres was investigated through gas-phase CL detection.…”

“…Such an oxidizing agent would inevitably consume negative oxygen ions by the electron transfer reaction 27 (reaction (7)). Meanwhile, it also acted as the quencher of 1 (10)). It could be deduced that on the one hand, corona discharge in pure O 3 atmosphere resulted in a negligible CL performance (Fig.…”

A paper based microfluidic device for the detection of arsenic using a gold nanosensor

“…1,2 Much effort through optical and electrochemical pathways has been invested in the detection of arsenic ions below 10 ppb, but certain limitations such as cost effectiveness and easy accessibility of the specic instrument made those approaches non-suitable specically for onsite real-time analysis of arsenic. [3][4][5][6] Lab-based techniques like Atomic Absorption Spectrometry (AAS), Atomic Fluorescence Spectrometry (AFS), and Inductively Coupled Plasma with Mass Spectrometry (ICP-MS) could provide the accurate detection of arsenic, but they are neither cost-effective nor capable of on-site analysis of sample. 4,5 Electrochemical method for arsenic detection has been proved as an affordable, accurate determination technique with low detection limit, but it still requires a lab setting with bulk electrodes in an electrochemical cell and also suffers from the interferences by the co-deposition of other metals, especially copper if present along with arsenic in water sample.…”

“…4,5 Electrochemical method for arsenic detection has been proved as an affordable, accurate determination technique with low detection limit, but it still requires a lab setting with bulk electrodes in an electrochemical cell and also suffers from the interferences by the co-deposition of other metals, especially copper if present along with arsenic in water sample. 3,6 Another reliable approach, i.e. colorimetric method is simple, inexpensive and show good detection limit.…”