The selection of elution flow rate is very important, because elution flow rate not only affects the nebulizer efficiency, but also control the efficiency of desorption of REEs from the P507 extraction resin.
Due to the above reasons, the analytes signal intensity became low with the increase of elution flow rate.
In the elution step, the valve was in injection position and a flow of 2 mol/l HCl was introduced by Pump B into the micro-column from the other end of the column to elute samarium and europium and carried it to ICP-MS system for detection.
By running a gradient elution where good solvent is gradually added to the mobile phase, solvent strength increases until finally reaches the capability of dissolving the sample that elutes from the column at a retention time that is function of the solvent gradient employed and of the sample chemical structure.
1 how the baseline changes, after the above delay time, when a gradient elution hexane/THF 70/30, to 60/40 in 1 min, and to 35/65 in 19 min, is employed.
To increase separation a gradient with steeper initial change was attempted, with the aim of obtaining earlier elution of styrene-rich samples, and slower dissolution rate of ethyl acrylate-rich ones.
The difference between the two gradients is such that there is a crossover composition at [approximately]15 min analysis time [ILLUSTRATION FOR FIGURE 4a OMITTED], which corresponds to the elution of copolymers having roughly 50% ethyl acrylate content.
Calibrations curves of retention times against copolymer compositions were drawn with the data obtained under different elution conditions.
The methods used for simultaneous separation of Cr compounds and adenine nucleotides generally include two types of protocols: (1) isocratic elution of these compounds in an organic solvent-free buffer followed by stepwise switch to another buffer contaning acetonitrile or methanol and (2) typical gradient elution method where Cr derivatives are eluted in isocratic conditions and adenine nucleotides by organic solvent gradient elution.
Table 1) and nucleotides by gradient elution in high ionic strength phosphate buffer, which has a moderate acetonitrile concentration at a very low TBA concentration.
The samples were run in isocratic mode in a low ionic strength Na phosphate buffer and moderate TBA concentration (3 mM) followed by gradient elution in a high ionic strength buffer solution containing a low TBA concentration (0.3 mM) and acetonitrile in 10 min as described in Materials and Methods.