COMPARATIVE STUDY BETWEEN NEAR-INFRARED(NIR) SPECTROMETERS IN THE
MEASUREMENT OF SUCROSE CONCENTRATION
INTRODUCTION
NIR Spectroscopy I
A spectroscopic method that uses the near-infrared region of the electromagnetic spectrum (from about 800 nm to 2500 nm).
NIR spectra have only a few significant peaks, but they are exceptionally information-rich due to the number of overlapping absorption bands.
NIR Spectroscopy II
NIR can typically penetrate much further into a sample than mid infrared radiation due to the low coefficient of absorbance.
NIR radiation has less energy/photon but does excite molecular vibrations.
NIR measurements are non-destructive and samples are not altered and can be reused.
The Importance of MeasuringSugar Concentration in Fruit I
Commonly used in the wide range of crops.
The important aspect to test the maturity of fruit and obtain the right time to harvest it.
The percentage of sugar (oBrix), indicates the sweetness of the fruit.
The Importance of MeasuringSugar Concentration in Fruit II
Contribute to the calculation of sugar-acid ratio which is one of the step needed to test the maturity of fruit.
One critical element of the ripening involves the conversion of starches to sugars.
The example of starch test is shown in Figure 1.
Objectives
1. To compare response analysis between lower and same range of NIR wavelength (Jaz and QE65000) spectrometer.
2. To identify response analysis of higher range of wavelength (NIRQuest) spectrometer.
3. To compare response analysis between lower and higher range of NIR wavelength spectrometer.
ProblemStatement
The NIR spectrometers are widely used in the spectroscopy field.
The calibration transfer between NIR spectrometers should be practiced in spectroscopy field to improve the efficiency in energy, time and work.
The comparative study between NIR spectrometers will give huge contribution to the calibration transfer.
MATERIALSAND
METHOD
Apparatus and Material Background I
The apparatus used in the experiment are: QE65000 Spectrometer (650 – 1100 nm), Figure 2. NIRQuest512-2.2 Spectrometer (900 – 2200 nm),
Figure 3. Handheld Refractometer, Figure 4.
The apparatus used in the reference taken: JAZ-COMBO Spectrometer (650 – 1100 nm), Figure 5.
*** The characteristics and properties of NIR spectrometers are shown in the Table 1.
Apparatus andMaterial Background II
The material used in the experiment is: Sucrose:
The molecule is a disaccharide sugar composed of the monosaccharides glucose and fructose with the molecular formula C12H22O11.
*** The skeletal formula for sucrose is shown in the Figure 6.
ExperimentSetup
The overall experimental setup was conducted using spectroscopic instrumentations from Ocean Optics.
The setup is illustrated in Figure 7.
The response was due to mixture between water with sucrose for different type of spectrometer.
The characteristics of sucrose sample used in the experiment are tabulated in Table 2.
Methodology
The flow chart of the experiment is shown in the Figure 8.
The experiment was conducted only for the calibration data.
RESULTS ANDDISCUSSIONS
Response Analysis betweenJaz and QE65000 Spectrometer I
Significant results were managed to be located at wavelength between approximately 940 and 985 nm.
Figure 9(a) and Figure 9(b) shows the resultant linear regression generated between absorbance and sucrose concentration by using Jaz and QE65000 spectrometer respectively.
Response Analysis betweenJaz and QE65000 Spectrometer II
λ = 959 nm managed to generate the highest coefficient of determination for sucrose by using:
Jaz spectrometer : R2 = 0.9794; RMSE = 1.43 QE65000 spectrometer : R2 = 0.956 ; RMSE = 2.15
The pattern behaviour of linear relationship between absorbance and the sucrose concentration against wavelengths for Jaz and QE65000 spectrometer are shown in Figure 10(a) and Figure 10(b) respectively.
Response Analysis betweenJaz and QE65000 Spectrometer III
It can be seen that the correlation between absorbance and sucrose concentration starts to loose its linearity once it has moved further than 960 nm.
Further analysis through the application of Multiple Linear Regression (MLR) has successfully improved the correlation for sucrose measurement.
Response Analysis betweenJaz and QE65000 Spectrometer IV
The highest efficiency algorithm has been identified by using different wavelengths:
Jaz spectrometer: 730, 830, 915, and 960 nm QE65000 spectrometer: 909 and 960 nm
Response Analysis betweenJaz and QE65000 Spectrometer V
The calibration algorithm, R2, and RMSE for calibration (RMSEC) for both spectrometers are as follows:
Jaz spectrometer:
Sucrose concentration (°Brix) = 122 + 1375ƛ730 - 942ƛ830 + 855ƛ915 - 736ƛ960
(R2= 0.992; RMSEC = 0.907 °Brix);
Response Analysis betweenJaz and QE65000 Spectrometer VI
QE65000 spectrometer:
Sucrose concentration (°Brix) = 135 + 777ƛ909 - 824ƛ960
(R2= 0.995; RMSEC = 0.760 °Brix)
The linearity of the calculated model are illustrated in Figure 11(a) and Figure 11(b) for Jaz spectrometer and QE65000 spectrometer respectively.
Response Analysis ofNIRQuest Spectrometer I
Significant result is managed to be located at wavelength between approximately 980 and 1700 nm.
Figure 12 shows the resultant linear regression generated between absorbance and sucrose concentration by using NIRQuest spectrometer.
Response Analysis ofNIRQuest Spectrometer II
λ = 1363 nm managed to generate the highest coefficient of determination and lowest RMSE for sucrose by using:
NIRQuest spectrometer : R2 = 0.813; RMSE = 4.64
The pattern behaviour of linear relationship between absorbance and the sucrose concentration against wavelengths for NIRQuest spectrometer is shown in Figure 13.
Response Analysis ofNIRQuest Spectrometer III
The correlation between absorbance and sucrose concentration starts to loose its linearity once it has moved further than 1400 nm.
Further analysis through the application of Multiple Linear Regression (MLR) has successfully improved the correlation for sucrose measurement.
Response Analysis ofNIRQuest Spectrometer IV
The highest efficiency algorithm has been identified by using different wavelengths:
NIRQuest spectrometer : 980, 1156, 1163, 1195, 1337, 1350, 1395, 1606, 1670, 1676, and 1682 nm.
Response Analysis ofNIRQuest Spectrometer V
The following are the calibration algorithm, R2, and RMSEfor calibration (RMSEC):
NIRQuest spectrometer
Sucrose concentration (°Brix) = 171 + 79ƛ980 + 2909ƛ1156 - 1550ƛ1163 - 422ƛ1195 + 445ƛ1337 - 1783ƛ1350 + 310ƛ1395 – 41.8ƛ1606 + 298ƛ1670 - 298ƛ1676 + 195ƛ1682
(R2 = 0.982; RMSEC = 1.613 °Brix)
The linearity of the calculated model is illustrated by Figure 14.
Response Analysis betweenNIR Spectrometers I
By comparing the three spectrometers, all of them show the same properties :
The absorption of a specific range of NIR wavelength decreases linearly with the increases of sucrose concentration.
Further analysis through MLR has successfully improved the correlation for sucrose measurement.
Response Analysis betweenNIR Spectrometers II
The ascending order of highest coefficient determination produced are by using NIRQuest, Jaz, and QE65000 spectrometers.
CONCLUSIONSAND
RECOMMENDATIONS
Conclusions I
Wavelength that generate the highest coefficient of determination :
Jaz spectrometer: 959 nm (R2 = 0.9794; RMSE = 1.43)
QE65000 spectrometer : 959 nm (R2 = 0.956 ; RMSE = 2.15)
NIRQuest spectrometer : 1363 nm (R2 = 0.813; RMSE = 4.64)
Conclusions II
Combination of NIR wavelength that produce the highest coefficient of determination:
Jaz spectrometer : ƛ=730, 830, 915, and 960 nm(R2= 0.992; RMSEC = 0.907)
QE65000 spectrometer : ƛ=909 and 960 nm(R2= 0.995; RMSEC = 0.760)
Conclusions III
NIRQuest spectrometer : ƛ=980, 1156, 1163, 1195, 1337, 1350, 1395, 1606, 1670, 1676, and 1682 nm(R2 = 0.982; RMSEC = 1.613)
These wavelengths exert an important combination in development of calibration algorithm for individual spectrometer measurement.
Recommendations
For future experiment :
record the validation data as well in order to confirm the prediction.
conduct the experiment by using the sugar content in fruit to obtain the real experience on how to improve the intrinsic quality of fruit.
THE END
Figure 1 : The Example of Starch Test
Figure 2 : QE65000 Spectrometer
Figure 3 : NIRQuest512-2.2 Spectrometer
Figure 4 : Handheld Refractometer
Figure 5 : Jaz Spectrometer
Table 1 :The characteristics and properties of NIR spectrometers.
Jaz QE65000 NIRQuest
Characteristics -Modular, stackable and autonomous components-Czemy-Turner optical bench-On-board microprocessor and OLED display-Replaceable slits and gratings-Ethemet and memory module-Battery and external memory module
-200-1100 nm spectral range-grating dependent-Resolution 0.14-7.7 nm (FWHM)-Peak quantum efficiency 90%-Back thinned 2DCCD detector-Thermoelectric cooling-6 slit options-14 grating option
-900-2050 nm spectral range-Less than 1 nm optical resolution FWHM-15000:1 signal to noise-On board thermoelectric cooling-16 bit USB A/D converter-Crossed czemy-Turner optical bench-Various trigger modest grating options
Application -Fluorescence-Biotechnology-Raman spectroscopy-DNA sequencing-Remote sensing-Dosimetry
-Spectroscopy-Medical-Biomedical imaging analysis-Fluorescence-Luminescence detection
-Luminescence detection-Spectroscopy of emission and absorption lines spectroscopy
Figure 6 : Skeletal Formula for Sucrose
Figure 7 : Experiment Setup for NIR Measurement (Top view)
Table 2 :The Sample Characteristics.
Spectrometer Range of Sucrose
(°Brix)
Mean n
(Calibration)
Jaz 0.9-35.0 17.1 50
QE65000 0.1-39.1 8.8 50
NIRQuest512-2.2 0.2-38.8 18.8 50
Figure 8 : Flow Chart of Experiment
Apparatus setup
Sample preparation
Collect reference spectrum
Reduce concentration of sucrose until 50
data
Save data obtained
Repeat experiment with other
spectrometer
Data analysis
Figure 9(a) : Linear relationship between absorbance and concentration of aqueous
sucrose at λ = 959 nm by using Jaz spectrometer
Sucrose Concentration (Brix)
Abs
orba
nce
403020100
0.12
0.11
0.10
0.09
0.08
0.07
y = -0.001394x + 0.1193; R-Sq = 0.9794
Figure 9(b) : Linear relationship between
absorbance and concentration of aqueous sucrose at λ = 959 nm by using QE65000
spectrometer
Sugars concentration (Brix)
Abs
orba
nce
403020100
0.165
0.160
0.155
0.150
0.145
0.140
0.135
0.130
y = - 0.000714x + 0.1645
Figure 10(a) : Coefficient of determination generated at different wavelength for aqueous
sucrose concentration by using Jaz spectrometer
Wavelength (nm)
Coe
ffici
ent of
Det
erm
inat
ion
10101000990980970960950940930920
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
Figure 10(b) : Coefficient of determination generated at different wavelength for aqueous
sucrose concentration by using QE65000 spectrometer
Wavelength (nm)
Coe
ffici
ent of
Det
erm
inat
ion
10101000990980970960950940930920
1.0
0.8
0.6
0.4
0.2
0.0
Figure 11(a) : Calculated VS actual concentrations of sucrose by using Jaz spectrometer.
Actual Concentration (Brix)
Cal
cula
ted
Con
cent
rati
on (
Bri
x)
35302520151050
35
30
25
20
15
10
5
0
Figure 11(b) : Calculated VS actual concentrations of sucrose by using QE65000 spectrometer.
Actual Concentration (Brix)
Cal
cula
ted
Con
cent
ration
(B
rix)
4035302520151050
40
35
30
25
20
15
10
5
0
Figure 12 : Linear relationship between absorbance and concentration of aqueous sucrose at λ = 1363 nm by
using NIRQuest spectrometer.
Sucrose Concentration (Brix)
Abs
orba
nce
403020100
1.30
1.25
1.20
1.15
1.10
1.05
y = - 0.006183x + 1.300
Figure 13 : Coefficient of determination generated at different wavelengths for aqueous sucrose
concentration by using NIRQuest spectrometer.
Wavelength (nm)
Coe
ffici
ent of
Det
erm
inat
ion
1600150014001300120011001000
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
Figure 14 : Calculated VS actual concentrations of sucrose by using NIRQuestspectrometer.
Actual Concentration (Brix)
Cal
cula
ted
Con
cent
ration
(B
rix)
403020100
40
30
20
10
0
