69 UV light at 215 nm was used as detector. Transgenomic Model ORH801 column
was used for organic acid determination with 0.01 N H
2
SO
4
as mobile phase. Refractive index was used as detector. Degradation product determination was
performed by the comparison of sample with the standard compound. Qualitative analysis was based on the retention time of each compound in the chromatogram,
while quantitative analysis was based on the calibration curve prepared using standard compound. The details of the calibration curves for different compounds tested are
presented in Table 3.3 and the plots of concentration vs. area are presented in Figure 1, 2, 3, and 4 of Appendix.
Table 3. 3 The correlation constants for the calibration curves for MDEA and organic acids.
Compound Column name
Calibration curve R
2
Remark
MDEA YMC-Pack PolymerC18
[MDEA] = 0.5354Area 0.9998 Figure A1 of
Appendix A Oxalic Acid
YMC-Pack PolymerC18 [Oxalic Acid] = 0.8558Area
0.9994 Figure A2 of Appendix A
Formic Acid Transgenomic-ORH801
[Formic Acid] = 0.0236Area 0.9999 Figure A3 of
Appendix A Acetic Acid
Transgenomic-ORH801 [Acetic Acid] = 0.0177Area
0.9999 Figure A4 of Appendix A
3.3.6 Nitrate NO
3 -
and Nitrite NO
2 -
Determination
The profiles of the nitrate NO
3 -
and nitrite NO
2 -
were evaluated by using ion chromatography Metrohm-761 Compact IC, which was equipped with Metrosep A
Supp 5-150 column. Mixture of 1.0 mM of NaHCO
3
and 3.2 mM of Na
2
CO
3
in one liter deionized water was used as mobile phase. Meanwhile, a conductivity meter was
used as detector. The concentrations of both nitrate NO
3 -
and nitrite NO
2 -
were determined based on the calibration curves listed in Table 3.4, and the plots of
concentration vs. area are shown in Figure 5 and 6 of Appendix 1, respectively.
70
Table 3. 4 The correlation constants for the calibration curves for nitrate NO
3 -
and nitrite.
Compound Column name
Calibration curve R
2
Remark
Nitrate NO
3 -
Metrosep A Supp 5-150 [NO
3 -
] = 0.1347 Area 0.9998
Figure A5 of Appendix A
Nitrite NO
2 -
Metrosep A Supp 5-150 [NO
2 -
] = 0.1356 Area 0.9949
Figure A6 of Appendix A
3.3.7 Estimation of Ammonium NH
4 +
The estimation of NH
4 +
was made using Nessler’s reagent [127 – 128] according to
Method 8038 Nitrogen HACH [125]. A sample of 25 ml was required for this measurement. The NH
4 +
concentration was measured using spectrophotometer DR 2000 HACH based on the intensity of color formed.
3.3.8 Un-reacted H
2
O
2
Determination
The determination of un-reacted H
2
O
2
during the UVH
2
O
2
process was performed by titration method using 0.062 N KMnO
4
solution. Titration of acidified sample from UVH
2
O
2
process was conducted. The end point was the change in color of the solution from colorless to light pink. Sodium oxalate was used to standardize the
KMnO
4
solution [124].
3.3.9 pH
The pH measurements were made using pH meter HACH sension 1. The pH meter was calibrated and standardized regularly. Measurement of pH during oxidation
process was conducted to monitor the change in pH condition during the oxidation process in the reactor.
71
3.3.10 Measurement of UV Intensity
