# Online Determination of Boron Isotope Ratio in Boron Trifluoride by Infrared Spectroscopy
## 3 Results and Discussion  
### Calculation and Correction of the Isotope Ratio  
Figure 4 shows the comparison of the IR spectrograms in the 2v\({}_{3}\) regions between natural abundance BF\({}_{3}\) and enriched \({}^{11}\)BF\({}_{3}\). The peaks at these regions are more complex than peaks in the v\({}_{3}\) regions. Fortunately, the peak changes had no significant overlap of the two bands. By contrast, the absorption band of 2v\({}_{3}\) for \({}^{10}\)BF\({}_{3}\) (the range being about 3270-3170 cm\({}^{-1}\)) was significantly reduced, which proved that this absorption band is influenced by the amount of \({}^{10}\)BF\({}_{3}\) that is present. In contrast, the absorption peaks in the 2v\({}_{3}\) band for \({}^{11}\)BF\({}_{3}\) (the range being about 3170-3070 cm\({}^{-1}\)) varied regularly with changing concentrations of \({}^{11}\)BF\({}_{3}\). Thus, it was feasible to calculate the isotope ratio based on comparing the peak areas of these two absorption bands. The NIST SRM 951a boric acid standard sample was used to investigate the accuracy of the ICP-MS. Before testing by ICP-MS, the standard boric acid sample was dissolved and diluted to a solution containing 0.1 \(\upmu\)g/mL of boron with ultrapure water. The relative error between the result from the ICP-MS and the standard value is shown in Table 2. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Item** & **Parameter** & **Item** & **Parameter** \\ \hline Nebulizer & Microconcentric & Sensitivity/s\({}^{-1}\) & 1.759 \(\times\) 10\({}^{6}\) CPS \\ Spray chamber temperature/\({}^{\circ}\)C & 3 & Scanning mode & Peak-jump \\ Nebulizer gas flow/L-min\({}^{-1}\) & 0.93 & Dwell time/ms & 10 \\ Auxiliary gas flow/L-min\({}^{-1}\) & 0.9 & Acquisition degree & 10 \\ Cool gas flow/L-min\({}^{-1}\) & 10 & Acquisition time/s & 20 \\ Plasma power/W & 1250 & Channels per AMU & 3 \\ Resolution & Standard & Runs/replicates & 3 \\ Sample uptake rate/mL-min\({}^{-1}\) & 1 & Sample depth/mm & 104 \\ Ionization lens parameters & L1 3.8; L2 31.8; L3 189.8 & - & - \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Experimental conditions and parameters of inductively coupled plasma mass spectrometry (ICP-MS). Counts per Second (CPS); Atomic Mass Unit (AMU). Figure 4: Comparison of the IR spectrograms. (**A**) Natural abundance BF\({}_{3}\); (**B**) Enriched \({}^{11}\)BF\({}_{3}\). The relative error between the experimental result from the ICP-MS and the isotopic ratio of the standard material was less than 0.16%. This result indicated that the ICP-MS, which was used to determine the boron isotope ratio in solution has a high accuracy, and could be used to calibrate the isotope ratio of boron in BF\({}_{3}\). In Figure 4, the isotopic ratio values of the samples were calibrated by ICP-MS. The \({}^{10}\)B/\({}^{11}\)B ratios of the natural abundance BF\({}_{3}\) and enriched \({}^{11}\)BF\({}_{3}\) samples were 0.2473 \(\pm\) 0.0009 and 0.0526 \(\pm\) 0.0011, respectively. \({}^{10}\)BF\({}_{3}\) and \({}^{11}\)BF\({}_{3}\) could be regarded as two distinct forms of matter. As is shown in Figure 5, the graph shape of \(A_{10}\) represents peaks of 2v\({}_{3}\) of \({}^{10}\)BF\({}_{3}\). Similarly, \(A_{11}\) represents 2v\({}_{3}\) peaks for \({}^{10}\)BF\({}_{3}\). The baselines of the spectrograms were adjusted to zero before calculation. The experiments were processed at room temperature (25 \(\pm\) 3 \({}^{\circ}\)C). It is obvious that the difference in the peak integration value is significant between the \(A_{10}\)/\(A_{11}\) and the true value of \({}^{10}\)B/\({}^{11}\)B, and this is most likely due to \({}^{10}\)BF\({}_{3}\) and \({}^{11}\)BF\({}_{3}\) having different molar absorption coefficients at the 2v\({}_{3}\) band. According to Lambert-Beer theory:  
\[\lg(I_{0}/I)=\varepsilon\times b\times c \tag{1}\]  
where, \(\varepsilon\) is the molar absorption coefficient, \(c\) is the molarity of the substance (mol/L), \(b\) is the optical length (cm), and \(\lg(I_{0}/I)\) is the absorbance at the specific wavenumber.