ABSTRACT
Studies were carried out to develop an HPLC method for the determination of lanthanides, in presence of Th and U, without involving any pre-separation procedure for the matrix elements (Th, U). The effect of concentration of the ion interaction reagent on the retention pattern of lanthanides, thorium and uranium was studied using a reversed-phase C18 column. The chromatographic parameters were optimized for maximizing the capacity of the column to hold thorium. Dual gradient elution was used for the separation of lanthanides from a mixture of thorium and uranium present in large proportion. The method facilitates the use of a minor fission product as an internal standard for the accurate and precise quantification of lanthanides by HPLC. The developed methodology was validated by using synthetically prepared samples with different proportions of lanthanides. Studies were also carried out for the separation and determination of U and Th on a reversed-phase column. A gradient of methanol and alpha-hydroxy isobutyric acid was employed for the separation and determination of uranium in presence of large amounts of thorium.
Subject(s)
Chromatography, High Pressure Liquid/methods , Lanthanoid Series Elements/isolation & purification , Butyrates/chemistry , Chromatography, High Pressure Liquid/instrumentation , Hydrogen-Ion Concentration , Isobutyrates , Lanthanoid Series Elements/analysis , Methanol/chemistry , Reproducibility of Results , Thorium/analysis , Thorium/isolation & purification , Uranium/analysis , Uranium/isolation & purificationABSTRACT
Separation and determination of lanthanides, Th and U is of great relevance in different fields of science and technology. Reversed-phase high-performance liquid chromatography (RP-HPLC) using alpha-hydroxy isobutyric acid (alpha-HIBA) as an eluent on reversed-phase column modified to cation exchanger has been reported to achieve the separation. However, under those conditions, Th and U are eluted amongst lanthanides, making their quantification difficult due to overlapping with some of the lanthanides peaks. In this work, different chromatographic parameters (concentrations of eluent and ion interaction reagent, pH, etc.) were studied systematically to arrive at optimum chromatographic conditions. Using the dual (concentration and pH) gradient conditions, lanthanides, Th and U could be separated in 11 min by RP-HPLC with sequential elution of Th and U after the elution of all the lanthanides. The separation methodology was tested using SY-3 rock sample for the separation and determination of lanthanides, Th and U. The method allows an accurate determination of these elements in a single run using a single column. Also, the method is fast and cost-effective compared to the reported methods.
Subject(s)
Chromatography, High Pressure Liquid/methods , Lanthanoid Series Elements/isolation & purification , Thorium/isolation & purification , Uranium/isolation & purification , Butyrates/chemistry , Hydrogen-Ion Concentration , Isobutyrates , Lanthanoid Series Elements/analysis , Thorium/analysis , Uranium/analysisABSTRACT
The resolution for the three homologues of alpha-hydroxycarboxylic acids viz. lactic acid, alpha-hydroxyisobutyric acid (alpha-HIBA) and alpha-hydroxy-alpha-methylbutyric acid (alpha-H-alpha-MBA), was compared for the individual separation of 14 lanthanide elements under identical experimental conditions. Alpha-HIBA was found to be the best for separation of heavier lanthanides (Tb to Lu) while alpha-H-alpha-MBA led to a better separation for lighter lanthanides (La to Eu). All the 14 lanthanides were separated by gradient HPLC employing both alpha-HIBA and alpha-H-alpha-MBA so that there was reasonable resolution among all the peaks and the separation was completed in a short time.
