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4 Results Rinsing of new consumables Rinsing of a new RO cartridge (first water purification system) When installing a new reverse osmosis cartridge in a water purification system, or when changing purification media of a polishing system, it is mandatory to allow all preservative solutions and possible leachables from materials to be rinsed out. This is why most pieces of modern equipment have an automatic rinsing and flushing time after each maintenance operation. To study the influence of this RO membrane on water quality, RO water from reject and permeate was collected at different times during the regular RO rinse cycle. The water produced during this cleaning cycle is automatically discarded by the system itself and does not go through further purification stages. Additional chromatographic profiles were obtained after 2 days and 13 days of system use. Chromatograms are those indicated in Figure 6. UV absorbance (A.U.) UV absorbance (A.U.) 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 %CH 3CN 0.00 0 2 4 6 8 10 12 14 16 0.10 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 RO reject RO permeate Time (minutes) 100 % 0.00 0 2 4 6 8 10 12 14 16 Time (minutes) Figure 6: RO reject and RO permeate water profiles. 30 min 1 h 30 The amount of organics released during the first 30 minutes of the RO rinse is quite significant and justifies the automatic rinsing function of a new RO cartridge. The RO reject profiles also give a good indication of the best efficiency time. The amount of organic preservative solution coming off the membrane after a 2 hour rinse does not represent an amount which could impair further purification processes. The R&D Notebook: From tap to ultrapure water: tracking organic contaminants 2 h 3 h 30 4 h 30 min 2 h 2 h 30 4 h 2 days 13 days Rinsing of new purification media (final polishing system) The organic quality of the ultrapure water was checked over time during the installation procedure of a new polishing cartridge. When installing a new purification cartridge, it is mandatory to produce water for 5 minutes to the drain. Then, it is recommended to leave the system in standby mode for 6 hours. A 5 minute recirculation per hour during this period allows good hydration and final rinsing of the new purification media. After these 6 hours, water is again produced to the drain for 5 minutes. This installation procedure allows any remaining trace contamination and air present in the purification cartridge to be removed and ensures reproducible excellent baselines at 254 nm as well as 214 nm. Chromatograms shown in figure 7 highlight this high quality water suitable for high sensitivity HPLC organic analyses. The four first chromatograms show the efficiency of the installation procedure of a new polishing cartridge. The last chromatogram is an example of the baseline that can be achieved with ultrapure water suitable for organic trace analysis at 254 or 214 nm UV detection. UV absorbance UV absorbance UV absorbance 0.050 0.040 0.030 0.020 0.010 0.050 0.040 0.030 0.020 0.010 Milli-Q system water, 1 min air purge 214NM 254NM 0.000 0.00 4.00 8.00 12.00 16.00 Gradient Time (minutes) 0.050 0.040 0.030 0.020 0.010 Milli-Q system water, 4 min air purge 214NM 254NM 0.000 0.00 4.00 8.00 12.00 16.00 Gradient Time (minutes) Milli-Q system water, 1 min after 6 hours 214NM 254NM 0.000 0.00 4.00 8.00 12.00 16.00 Gradient Time (minutes) Figure 7: Ultrapure water baselines at 254 nm and 214 nm.
UV absorbance UV absorbance From tap to ultrapure water Using the water purification chain described previously, the various sampling points enable the organic decrease through the different water purification processes to be traced. The change in organic nature during water treatment does not allow direct contaminant identification. However, chromatogram profiles obtained, and especially at 214 nm, the more sensitive wavelength, highlight organic contamination removal through the purification stages (see Figure 8). This shows the importance of having a combination of technologies when producing ultrapure water from potable water. Conclusion 0.050 0.040 0.030 0.020 0.010 Milli-Q system water, 6 min after 6 hours 0.000 0.00 4.00 8.00 12.00 16.00 Gradient Time (minutes) 0.050 0.040 0.030 0.020 0.010 214NM 254NM Milli-Q system water, day 20 214NM 254NM 0.000 0.00 4.00 8.00 12.00 16.00 Gradient Time (minutes) Figure 7: Ultrapure water baselines at 254 nm and 214 nm. The presence of impurities in the mobile phase, and especially in the purified water used for HPLC studies raises several issues: - These contaminants create peaks during gradient runs. This leads to problems with peak identification and peak quantitation. - The impurities contaminate and “kill” columns. - When solutions of standards are prepared with impurities contained in ultrapure water, inaccurate results are obtained for sample identification and quantitation. - Moreover, when preparative chromatography is performed, impurities in mobile phase and/or samples prepared, can contribute to contaminated fractions. A significant number of studies have shown the importance of water quality during HPLC analysis. Storage of high purity water is inadequate and inappropriate to obtain high quality baselines 11 . A.U. (254 nm) A.U. at 214 nm 0.035 0.030 0.025 0.020 0.015 0.010 0.005 0.000 0.00 5.00 10.00 15.00 20.00 0.035 0.030 0.025 0.020 0.015 0.010 0.005 Time (minutes) Figure 8: From tap to ultrapure water, chromatographic profiles at 254 nm (top) and 214 nm (bottom) (1 ml injected (Tap and RO) or 50 ml accumulated (EDI, reservoir and Milli-Q) on the C18 column). More and more sensitive detection methods are being coupled to HPLC in order to improve detection limits 12,13,14 . The mobile phase in RP-HPLC generally contains a “buffer” component, an organic modifier and, often, an ion pairing agent added to the mobile phase to influence selectivity. All solvents, buffering salts, ion pairing agents, as well as the water used to prepare the mobile phases, must be of high chemical purity. A water purification chain combining multiple technologies such as electrodeionization pretreatment, UV photooxidation and high quality purification media, and ensuring easy maintenance with automatic rinsing and flushing capabilities, delivers ultrapure water suitable for high sensitivity organic analyses. Additionally, the use of an ultrapure water system with on line TOC (Total Organic Carbon) analysis is the best way to monitor these organic contaminants at the point-of-use 15 . Tap RO EDI Reservoir Milli-Q 0.000 0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 Time (minutes) Tap RO EDI Reservoir Milli-Q The R&D Notebook: From tap to ultrapure water: tracking organic contaminants 5
Page 1 and 2: The R&D Notebook From tap to ultrap
Page 3: Experimental Water Purification Sys

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