Until recently, commercial near-infrared spectrometers (NIR) have been either high-performance, with high resolution and broad spectral range for laboratory use or portable and with low performance. Galaxy Scientific offers a new, high-performance, portable NIR solution with both the analytical performance and portability required for today’s applications The QuasIR™ series analyzer is a Fourier-transform near-infrared spectrometer (FT-NIR ) that weighs less than 8.5 kg, occupies 45x24x14 cm3, and is battery-operated. It is portable and, at the same time, delivers high performance. In this study, we examine the spectra collected on a high-performance benchtop FT-NIR instrument with spectra collected on our portable FT-NIR instrument to validate spectra compatibility and qualitative/quantitative model transferability and predict application performance.
The QuasIR™ 2000 and 3000 portable FT-NIR systems (Figures 1 and 2) were used to collect spectra for comparison with spectra collected using a benchtop instrument from a competing manufacturer.
Figure 1. QuasIR™ 2000 portable FT-NIR spectrometer
Figure 2. QuasIR™ 3000 portable FT-NIR spectrometer
In the fiber system study, an erythromycin (ethyl succinate) tablet (125 mg) , a coated oblong Advil tablet, and a doxycycline hyclate capsule (50 mg) were measured using the QuasIR™ 2000 equipped with a Galaxy Scientific solid probe (GS Probe) and Bruker’s Matrix-F equipped with either the Bruker lab solid probe or the GS probe. All spectra were collected over the same (approx.) period using 8 cm-1 resolution . For the erythromycin, tablet, established qualitative analysis Ident method and quantitative Quant PLS model were used to analyze the data . Spectra obtained for the tablets using both instruments were compared using a correlation coefficient method.
In the integrating sphere system study, four poly(ethylene -co-vinyl acetate) polymer beads, with approximate vinyl acetate concentrations of 12%, 18%, 25%, and 40%, were measured with the Matrix-I (four samples) and QuasIR™ 3000 (nine samples) using the same resolution and measurement times. Spinners were used to enlarge sampling quantity. The established quant model was used to predict the vinyl acetate concentration.
Result and Discussion
Erythromycin tablet (125 mg)
Figures 3 and 4 display, respectively, the original and 1st derivative spectra measured using the QuasIR™ 2000 and Matrix-F.
Figure 3. Original spectra of erythromycin tablet measured with QuasIR™ 2000 (red) and Matrix-F (blue)
After removing baseline differences between the two instruments using the 1st derivative, the spectra match well with each other, with the exception of moisture bands due to different moisture levels within the instruments.
Figure 4. 1st derivative spectra of erythromycin tablet measured with QuasIR™ 2000 (red) and Matrix-F (blue)
The same erythromycin tablet was measured using three Bruker Matrix-F systems (Bruker 1-3) and QuasIR™ 2000 systems (New 1–4). The resulting spectra were compared with the reference spectra in the established original Bruker Ident method. The Ident method produces a number representing how well the collected spectrum matches a stored reference spectrum. A lower hit quality number is a better match. All collected samples passed the test’s threshold; furthermore, the hit qualities of the QuasIR™ spectra were smaller on average than that of the Bruker spectra.
Table 1. Evaluation result with established Ident method
The resulting spectra were also analyzed using an erythromycin PLS model developed from data from multiple Matrix-F systems and multiple batches of tablets. The root mean square error of prediction (RMSEP) of the PLS model is 2.26%. The average predicted value of spectra measured on the Bruker Matrix-F is 64.3%, with STD of 0.36%. The average predicted value of spectra measured on the QuasIR™ analyzer is 64.5%, with STD of 0.34%.
These results show that methods developed using the Bruker FT-NIR can be directly used to analyze spectra collected using the QuasIR™ FT-NIR.
Coated Advil tablet
The oblong coated Advil tablet was measured using the Matrix-F and Bruker probe and the average spectrum of five measurements was used as the reference. The Galaxy Scientific probe (GS probe) was hooked to the Matrix-F and five spectra collected followed by five measurements with the same probe hooked up with QuasIR™ 2000. The original and 1st derivative spectra are presented in Figures 5 and 6, respectively.
Figure 5. Original spectra of coated Advil tablet measured using the QuasIR™ 2000 and Matrix-F
Figure 6. 1st derivative spectra of coated Advil tablet measured using the QuasIR™ 2000 and Matrix-F
Spectra collected on the two instruments were overlaid after using the 1st derivative to remove the baseline shift. When comparing spectra measured with a QuasIR™ 2000 spectrometer and those measured on a Bruker Matrix-F using a Galaxy probe to an average spectrum measured with Matrix-F using a Bruker probe , all correlation coefficients are very high (>99.8%) as shown in Table 2. There were no statistically significant differences between spectra measured using the Bruker or Galaxy FT-NIR spectrometers.
Table 2. Advil spectra comparison result
Doxycycline hyclate capsule (50 mg)
Five measurements of the doxycycline hyclate capsule were collected with the Matrix-F and Bruker probe and the average spectrum was used as the reference. These measurements were repeated with the Matrix-F and GS probe followed by the QuasIR™ 2000 and GS probe. Those 10 spectra were then compared with the reference spectrum. The correlation coefficient values are listed in Table 3.
Table 3. Doxycycline Hyclate Caps Spectra Comparison Result
The correlation coefficients are all higher than 0.97, which is very good. Due to the nature of capsules, the reproducibility of the measurement of the same capsule is not as good as with the tablet.
Poly(ethylene-co-vinyl acetate) samples with approximate vinyl acetate concentrations of 12%, 18%, 25%, and 40% were measured using the Matrix-I, Vector 22N-I, and QuasIR™ 3000 FT-NIRs equipped with an integrating sphere and sample spinner. In this study, samples were measured with a Vector 22N-I (one sample), Matrix-I (four samples), and QuasIR™ 3000 (nine samples). Vinyl acetate predictions were obtained from a third party using their established calibration. The original spectra are displayed in Figure 7 and 1st derivative spectra in Figure 8.
Figure 7. Original spectra of co-polymer sample with 12% vinyl acetate
Figure 8. 1st derivative spectra of co-polymer sample with 12% vinyl acetate
Each sample was measured three times on each instrument and the average predicted vinyl acetate results are presented in Table 4.
Table 4. Vinyl acetate prediction
|Matrix-I Ave (5)
|Matrix-I Std (5)
|QuaslR 3000 Ave (9)
|QuasIR 3000 STD (9)
|V22N-I Ave (1)
|V22N-I Std (1)
If we use average predictions from the Matrix-I systems as “true” values and use the average predictions from the QuasIR™ 3000 systems as predicted values, then we have an RMSEP of 0.688% and bias value of 0.630%. After simple bias correction, the PLS model developed with spectra obtained from Matrix-I can be directly used to predict spectra from QuasIR™ 3000 with a Standard Error of Prediction (SEP) of 0.319%, which is within the method error of 0.4%.
This study demonstrates that spectra obtained using two leading FT-NIR instruments can match well with each other. Qualitative methods can be directly transferred from one vendor to the other. Quantitative methods depend on sample nature and method of calibration used (accuracy, coverage of sample variation, coverage of instrument variation, etc.). The calibration can either be directly transferred or transferred with simple bias correction.
This information has been sourced, reviewed and adapted from materials provided by Galaxy Scientific Inc.
For more information on this source, please visit Galaxy Scientific Inc.