tailieunhanh - Soil and Environmental Analysis: Modern Instrumental Techniques - Chapter 6

Việc sử dụng các công cụ phòng thí nghiệm tự động để xác định tổng số carbon, C, và nitơ, N, bằng cách đốt cháy khô đã trở thành cũng được thành lập trong những năm gần đây. Điều này đã trở thành có thể thông qua sự phát triển của các thủ tục quá trình đốt cháy đơn giản và nhanh chóng và bằng cách nối chúng với hệ thống phân tích khí highsensitivity hiện đại trong các công cụ tích hợp duy nhất. Làm công cụ trở nên tinh vi hơn, khả năng đo đồng thời lưu huỳnh,. | 6 Automated Instruments for the Determination of Total Carbon Hydrogen Nitrogen Sulfur and OXygen Keith A. Smith The University of Edinburgh Edinburgh Scotland M. Ali Tabatabai Iowa State University Ames Iowa . I. INTRODUCTION The use of automated laboratory instruments for the determination of total carbon C and nitrogen N by dry combustion has become well established in recent years. This has become possible through the development of simple and rapid combustion procedures and by coupling them with modern high-sensitivity gas analysis systems in single integrated instruments. As instruments have become more sophisticated the capability of simultaneous measurement of sulfur S and or hydrogen H along with the C and N determinations has been added to some commercially available systems. Yet another optional add-on is the capacity to determine oxygen O in the same samples. Prior to such developments the techniques available for dry combustion systems were complicated and time-consuming and manual wet oxidation methods were generally preferred for analysis of soils plants and other environmental materials. However the balance now lies in the opposite direction. This chapter describes the principles on which automated dry combustion instruments and automated analyzers dedicated to the to Copyright n 2004 by Marcel Dekker Inc. All Rights Reserved. determination of dissolved organic C are based. It examines the particular features available with a selection of different commercial systems and reviews recent information from the scientific literature concerning the application of these instruments to the analysis of soils plants waters and other environmental materials. This chapter is an updated and extended version of that on dry combustion analyzers in the previous edition Tabatabai and Bremner 1991 to which reference should be made for information on evaluations of earlier commercial instruments for soil analysis. II. DRY COMBUSTION SYSTEMS A. Dumas Systems for C