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Mohd Sani Sarjadi & Mohd Marsin SanagiFrom Table 1, it is apparent that, the PS-DVB heptadecyl ketone has the highestbreakthrough volumes for both analytes compared to those for commercial PS-DVB and modifiedsorbents used in this study. PS-DVB heptadecyl ketone having the highest capacity in trapping theanalytes i.e 0.15 mg of nitrobenzene and 0.02 mg of 2-chlorophenol per 150 mg of sorbent. PS-DVB octadecoxy methyl sorbent capacity was lowest compared to other modified sorbents (Table2). This may be due to the presence of the polar carbonyl groups on PS-DVB heptadecyl ketonesurface, which improved the efficiency of the adsorbent by increasing the ability to undergo polarinteractions with the polar analytes. In addition, the presence of polar groups also caused thesorbent to be wetted easily and have an intimate contact with aqueous solution, therefore theanalyte can easily be extracted from the solution. Another reason could be that better interactionsoccurred between solutes (polar and non-polar) and PS-DVB heptadecyl ketone sorbent owing tohigher surface area of the sorbent (the home-made PS-DVB have been synthesized using 8% ofcrosslinker whereas the commercial PS-DVB only 4%).Table 2. Sorbent capacity of ODS-silica, unmodified PS-DVB and modified PS-DVB sorbentsusing nitrobenzene and 2-chlorophenol as analytes.Sorbent (150mg)Nitrobenzene4 ppm2-Chlorophenol4 ppmSorbentcapacity (mg)RSD(%)Sorbentcapacity (mg)RSD(%)ODS-silica0.171.310.088.56PS-DVB commercial1.24x10-38.890.4x10-315.80PS-DVB heptadecyl ketone0.152.690.0221.52PS-DVB Chloromethyl1.24x10-35.100.64x10-37.65PS-DVB Octadecoxy methyl0.48x10-317.680.40x10-315.81The breakthrough volume for nitrobenzene and 2-chlorophenol were 0.30 mL and 0.10mL respectively. Figure 3 shows the breakthrough curve of nitrobenzene and 2-chlorophenolusing commercial PS-DVB. Based on the results obtained, the analytes were poorly retained onthe said sorbent. The nature of analytes plays an important role in retention mechanisms on thePS-DVB which involves the ππ - interactions between the analyte and sorbent. PS-DVBpossesses exceptionally strong π-electrondonating-accepting ability, which causes retention ofcompounds that contain aromatic π-systems or functional groups with lone electron pairs suchas carbonyl and nitro groups. Even though the mentioned factors are favorable for the retentionsof analytes, the observed breakthrough volumes were small which could be caused by the smallcapacity of the sorbent.32
Determination Of On-line Breakthrough <strong>Volume</strong> And Percentage Recovery Of Modified Polystyrene-divinylbenzene (PS-DVB) As Chromatography AdsorbentFigure 3. Breakthrough volume curve of (a) nitrobenzene and(b) 2-chlorophenol using PS-DVB as the adsorbent.Figure 4 shows the breakthrough curve of nitrobenzene and 2-chlorophenol using PS-DVB heptadecyl ketone. Higher breakthrough volume was observed for both analytescompared to other modified PS-DVB. The breakthrough volumes for nitrobenzene was highercompared to 2-chlorophenol on PS-DVB heptadecyl ketone sorbent.33
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