Arsine generation is the gateway
for several sensitive and selective
methods of As determination. An electrochemical arsine generator (EAG)
is especially green: we report here the use of two electrode materials,
aluminum and highly oriented (ordered) pyrolytic graphite (HOPG) never
before used for this purpose. The first is operated on a novel constant
voltage mode: current flows only when the sample, deliberately made
highly conductive with acid, is injected. As a result, the cathode,
despite being a highly active metal that will self-corrode in acid,
lasts a long time. This EAG can be made to respond to As(III) and
As(V) in an equivalent fashion and is fabricated with two readily
available chromatographic T-fittings. It permits the use of a wire
roll as the cathode, permitting rapid renewal of the electrode. The
HOPG-based EAG is easily constructed from ion chromatography suppressor
shells and can convert As(III) to AsH<sub>3</sub> quantitatively but
has significantly lower response to As(V); this difference can be
exploited for speciation. The success of Al, an active metal, also
dispels the maxim that metals with high hydrogen overpotential are
best for electrochemical hydride generation. We report construction,
operation, and performance details of these EAGs. Using gas phase
chemiluminescence (GPCL) with ozone as a complementary green analytical
technique, we demonstrate attractive limits of detection (LODs) (S/N
= 3) of 1.9 and 1.0 μg/L As(V) and As(III) for the HOPG-based
EAG and 1.4 μg/L As(V) or As(III) for the Al-based EAG, respectively.
Precision at the ∼20 μg/L As(V) level was 2.4% and 2.1%
relative standard deviation (RSD) for HOPG- and Al-based EAGs, respectively.
Both HOPG- and Al-based EAGs permitted a sample throughput of 12/h.
For groundwater samples from West Texas and West Bengal, India, very
comparable results were obtained with parallel measurements by induction
coupled plasma-mass spectrometry