Xây dựng của học sinh bằng văn bản và các kỹ năng nói, kỹ lưỡng theo các bước hoạt động phát triển kỹ năng Khuyến khích tự học bằng cách sử dụng tài liệu tham khảo rộng rãi bao gồm vật liệu thi, ngữ pháp, văn bản và chức năng Thi nhiệm vụ theo phong cách trong suốt quá trình tích hợp với lời khuyên và chiến lược làm quen sinh viên với các định dạng thi. Sách Tài nguyên sinh viên nâng cao chuyên gia CAE với Key có sẵn bằng tiếng Anh | 236 Nutrient Control by the carrier thus in sulfamic acid only nitrate is reduced and in water nitrate and nitrite. Photoreduction has been also used with biamperometric detection Gil-Torro et al. 1998 detecting the triiodide formed by reaction between iodide and nitrite. As previously mentioned two measurements should be performed with and without irradiation in order to achieve speciation. Exclusive detection of nitrate is uncommon however methods with electrochemical detection have been proposed for this purpose. Thus for example the coulometric determination of nitrate by reduction over a glassy carbon electrode without interference of oxygen or nitrite Nakata et al. 1990 has been proposed or the potentiometric determination by means of photocured coated-wire electrodes in the flow injection potentiometric mode Alexander et al. 1998 . However it should be mentioned that only the potentiometric determination has been applied in the analysis of wastewater samples. In Table the analytical characteristics of some of the above-mentioned methods can be also observed. Organic and total nitrogen For organic nitrogen determination sample digestion is required to transform the organic compounds containing nitrogen into nitrogen inorganic species. From the mineralized sample the total nitrogen content can be determined and by subtraction the organic nitrogen content. Sample digestion is the most tiresome and slowest step of the analysis process of these parameters and hence has deserved greater attention as far as researchers are concerned with the aim to achieve its automation. This digestion can be carried out in different ways namely Kjeldahl method photochemical oxidation alkaline oxidation with persulfate or combustion at high temperature. The Kjeldahl method is the recommended manual standard method and provides a parameter widely used in water characterization the so-called Kjeldahl nitrogen. Although several flow methods may be found in the literature based
