Determination of Lanthanides, Thorium, Uranium and Plutonium in Irradiated (Th, Pu)O2 by Liquid Chromatography Using α-Hydroxyiso Butyric Acid (α-HIBA)

Abstract

An HPLC method is presented for the separation and determination of lanthanides (Lns), thorium (Th), uranium (U) and plutonium (Pu) from irradiated (Th, Pu)O 2 . Individual separation of Lns, Th, U and Pu is a challenging task because of 1) lanthanides having similar physical and chemical properties, 2) presence of complex matrix like irradiated fuel and 3) the co-existence of multiple oxidation states of Pu. Different procedures were developed for separation of individual lanthanides and actinides. The individual lanthanides were separated on a dynamically modified reversed phase (RP) column using n-octane sulfonic acid as an ion interaction reagent and employing dual gradient (pH and concentration) of α-hydroxyisobutyric acid (HIBA). In order to improve the precision on the determination of Lns, terbium (Tb) was used as an internal standard. The method was validated employing simulated high level liquid waste. Concentrations of lanthanides viz. lanthanum (La) and neodymium (Nd) in the dissolver solution were determined based on their peak areas. Th, U and Pu were separated on a RP column using mobile phase containing HIBA and methanol. Since Pu is prone to exist in multiple oxidation states, all the oxidation states were converted into Pu (IV) using H 2 O 2 in 3 M HNO 3 . Under the optimized conditions, Pu(IV) eluted first followed by Th and U. The concentrations of Th, U and Pu were determined by standard addition method and were found to be 1.10 ± 0.02 mg/g, 5.3 ± 0.3 µg/g and 27 ± 1 µg/g, respectively, in the dissolver solution of irradiated fuel. These values were in good agreement with the concentration of Th determined by biamperometry and those of U and Pu by isotope dilution thermal ionization mass spectrometry.

HPLC Method for Determination of Th, U and Pu in Irradiated (Th,Pu)O2 using Mandelic Acid as an Eluent

“…The data obtained were in agreement with those obtained by isotope dilution-thermal ionisation mass spectrometry [20].…”

“…It is seen that baseline separation was achieved using isocratic mode when mandelic acid is employed as the eluent. It may be noted that in the previous study employing HIBA as the eluent, a gradient of both the eluent and MeOH was required to achieve the base line separation [20]. Figure 5 shows the calibration curves obtained for Th, U(VI) and Pu(IV) using aliquots taken from solutions prepared by the dilution of the synthetic mixture in the concentration range 1 ppm to 50 ppm, under the optimised conditions as shown in Figure 4.…”

“…HPLC using chelating agents as eluents combines selective complexation, separation and specific detection for the determination of actinide elements [18]. For example, the chelating agent -hydroxy isobutyric acid (HIBA) has been reported for the separation of Th, U(VI) and Pu(IV) [19,20]. However, when HIBA is used as the chelating agent, the elution order was found to be Pu(IV), Th and U(VI).…”

“…The methods offering reduced analysis time, less generation of liquid waste and minimum dose to operator would have an edge in such applications. HPLC methods are reported for the separation and determination of Th and U in different matrices due to Brought to you by | New York University Bobst Library Technical Services Authenticated Download Date | 6/1/15 1:15 PM their ability to provide rapid and high performance separations [19,20]. HPLC using chelating agents as eluents combines selective complexation, separation and specific detection for the determination of actinide elements [18].…”

Elution profiles of lanthanides with α‐hydroxyisobutyric acid by ion exchange chromatography using fine resin

“…The effect of concentration of eluent HIBA on the elution of lanthanide has been investigated and it is reported that with increase in concentration of HIBA, the number of undissociated HIBA molecules in the mobile phase increases which results in increased complexation of metal ion, thereby decreasing the retention time of metal ion in the resin phase. However, the optimum concentration for an effective separation of lanthanides is reported to be 0.25 M .…”