Abstract
Potentially toxic elements are non-biodegradable and soluble under various environmental
conditions with possible interconversion of less harmful species to most toxic species. The
environmental prevalence of the species of arsenic (As), chromium (Cr), and lead (Pb) is
trivalent As (As(III)), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA),
pentavalent As (As(V)), arsenobetaine (AsB), arsenocholine (AsC), arsenosugars, trivalent Cr
(Cr(III)), hexavalent Cr (Cr(VI)) and bivalent Pb (Pb(II)). Multi-elemental quantitative
speciation analysis of As and Cr in water and sediments was conducted using high-performance
liquid chromatography – inductively coupled plasma – mass spectrometry (HPLC-ICP-MS) in
a single analytical sequence. Extraction of analytes in sediments was conducted using the
factorial design technique to optimise the extraction procedure. A 15 mL of 0.375 M
(NH4)2HPO4, 50 mM EDTA at neutral pH and temperature of 150 oC were found to be the
optimum extraction conditions for synchronous quantitative speciation analysis of As and Cr
in river sediments. The ammonium salts (NH4H2PO4 and NH4NO3) were examined as mobile
phases at different pH and compositions for suitability in gradient mode of elution. The
optimised chromatographic conditions achieved a baseline and peak resolution of As(III),
DMA, MMA, As(V), and Cr(VI) in the total separation time of 18 minutes. The polyatomic
ion interferences are likely to occur when ICP-MS is a detector for HPLC in elemental
speciation analysis experiments. The interferences were identified and eliminated by an interelement
correction (IEC) method using mathematical equations. A discovered percentage error
of 6.93 to 43.2% identified as potential ion interferences overlapping with MMA, As(III), and
Cr(VI) for water and sediments analysis were eliminated by deploying the IEC correction
method. Analytical figures of merits were assessed for multi-elemental speciation analysis of
both water and sediment’s proposed methods...