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A coupled-column system, consisting of a combination of a molecularly imprinted polymer (MIP) and a C(18)-silica column, was used for selective triazine detection in the HPLC mode. Complex aqueous samples, spiked with triazines, were selectively extracted by the MIP followed by subsequent identification by analytical reversed-phase chromatography. The MIP showed good performance for selectively discriminating triazines from humic acid, whereas urine and apple extract had some tendency to be retained by the MIP. Enrichment was observed in all cases, and triazine-enrichment factors of up to 100 could be recorded, with good extraction efficiency (74-77%). The results indicate that the high selectivity of MIPs can be favorably used for selective sample enrichment in conjunction with reversed-phase HPLC.

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Supported liquid membrane extraction is a powerful analytical methodology for continuous extraction and enrichment of ionizable organic pollutants from aqueous environmental samples. Sample workup with this technique can be hampered by low enrichment factors due to incomplete trapping in the stagnant acceptor solution for weak basic compounds. The different parameters, such as acceptor pH and ionic strength of both the donor and acceptor solutions, related to this problem were studied theoretically and experimentally. A simple equation for the maximum enrichment factor was developed. Results showed that the ionic strengths of the two aqueous phases in the system have an effect on the maximum enrichment factor, which can be increased by increasing the ionic strength of the donor phase. For chloro-s-triazines, a satisfactory agreement was obtained between the experimental measurements and theoretical estimations. This study defines the practical analytical applications and limitations of the system where the analytes are partially ionized in the acceptor solution.

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The antioxidant activity of the leaves and flowers of the Moringa oleifera plant were investigated and the results were compared to those of selected vegetables (cabbage, spinach, broccoli, cauliflower and peas). Antioxidant activity was determined by analysing the total phenolics content, total flavonoids content, reducing power and radical scavenging activity using the 2,2-diphenyl-1-picrylhydrazyl free radical method. The total phenolics content of moringa was almost twice that of the vegetables and the total flavonoids content was three times that of the selected vegetables. The reducing power of moringa was higher than that of the vegetables and the percentage of free radicals remaining was lower compared with the vegetables. These results combined show that moringa is a good source of antioxidants. This finding also explains why moringa forms part of the diet of people in many developing countries, especially in the southern hemisphere.

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