Rt. Gettar et al., Eriochrome Black T as a post-column reagent for the ion chromatographic determination of rare earths, J CHROMAT A, 855(1), 1999, pp. 111-119
The use of Eriochrome Black T in an alkaline, 40% methanol solution was fou
nd to be appropriate as post-column reagent for the determination of rare e
arths by ion chromatography. Detection of individual lanthanides and lantha
num was carried out at 512 nm and 650 nm after separation by dynamic cation
exchange chromatography with gradient elution on C-18 column and employing
a solution containing alpha-hydroxyisobutiric acid/sodium octanesulfonate
at pH 3.8 as eluent. The effect of the presence of micelles in the post-col
umn reagent was studied. Sensitivities obtained by the addition of the cati
onic surfactants cetylpyridinium chloride (CPC) and hexadecyltrimethylammon
ium bromide (CTAB) were lower than those measured without surfactant additi
on. In some cases, the signal was totally suppressed. No change in sensitiv
ity was observed with non-ionic (Triton X-100) or anionic (sodium dodecylsu
lphate, SDS) surfactants but a slight improvement in the baseline noise was
observed with the SDS. An evaluation of the influence of chemical and oper
ational variables on the post column reaction (PCR) reagent was carried out
either by spectrophotometric tests or by chromatographic experiments. A co
mparison was performed between three PCR reagents: Eriochrome Black T and x
ylenol orange in the presence of a cationic surfactant and arsenate III. Ca
libration response was linear up to an analyte concentration of 5.0 mu g ml
(-1). Absolute detection limits lower than 7 and 17 ng were obtained at the
detection wavelengths of 650 nm and 512 nm respectively, for all the natur
al lanthanides and lanthanum. (C) 1999 Elsevier Science B.V. All rights res
erved.