外文翻譯----植物、土壤和肥料中硅的分析方法（英文）

1、?9 2001 Elsevier Science B.V. All rights reserved. Silicon in Agriculture L.E. Datnoff G.H. Snyder and G.H. Kornd6rfer (Editors) 185 Chapter 11 Methods for silicon analysis in plants, soils, and fertilizers G. H. Snyde

2、r University of Florida, Everglades Research and Education Center, P.O. Box 8003, Belle Glade, FL 33430 USA The classical method for determining total silicon (Si) content of various materials has been conversion of ins

3、oluble silicates into sodium silicate through high temperature fusion with sodium hydroxide, or other sodic bases. The Si can then be determined by a variety of methods, including gravimetric, colorimetric, and absorpt

4、ion/emission spectrometry. Silicon also has been determined gravimetrically in plant tissue as the residue after acid digestion. We have developed a simple, inexpensive, and rapid method for solublizing Si in plant tis

5、sue that facilitates analysis of a large number of samples. When analyzing soils and fertilizers, a method for gauging the plant-available Si, rather than total Si, generally is desired. A number of soil-test methods

6、have been developed. Some require extended incubation periods, field- moist soil, or other procedures that inhibit adoption by routine soil-testing laboratories. Silicon extracted by acetic acid has been correlated to

7、Si uptake by rice (Oryza sativa L.) and rice grain yield. Using this method, the Everglades Soil Testing Laboratory analyses nearly five thousand samples annually. Since Si fertilizer sources differ in Si content and S

8、i solubility, analytical methods have been developed for predicting their relative ability to provide plant-available Si. We use a column leaching method based on Si elution in Tris buffer (pH 7) for the evaluation of

9、 potential Si soil amendments. However, greenhouse and field evaluations are essential for making final determinations. 11.1. INTRODUCTION Although the compound SiO 2 was isolated from various plant tissues in the late

10、 18 th century, the pure element Si was first isolated by Berzelius in 1823. He obtained it by combining potassium fluorosilicate with potassium (Urry, 1983), i.e., K2SiF6 + 4Kmet,~ = 6KF + Simeta t. Many procedures f

11、or determining the Si content of a wide variety of materials have been developed since that time. Nevertheless, although there are a few compendia of methods for examining mineral silicates, i.e., Jackson et al. (1986),

12、 there are virtually none that also review methods for chemically and physically analyzing plant materials for Si, and for determining total as well as plant-available Si in soils and fertilizers. An attempt is made to

13、 provide such comprehensive information on Si analysis in this paper. However, procedures are not presented in detail when they can be referenced in English-language journal publications that are widely available. 187

14、polyethylene tubes, and an autoclave as specialized equipment. The AID procedure is well adapted to handling batches of 40 or more samples at a time. The procedure uses the autoclave to develop pressure, rather than de

15、veloping pressure in sealed digestion vessels. Bell and Simmons (1997) found no significant difference between Si analyses of a National Institutes Standards Technology (NIST) pine needle standard (no. 1575) by a varie

16、ty of methods and that by the AID procedure. Recognizing the unavailability of NIST standards for Si, they used the AID procedure to determine Si in several other NIST plant sample standards as well. Nonozamsky et al.

17、(1984) also described a “rapid“ technique for extracting Si from plant tissue. By their method, ground plant material was shaken overnight at room temperature in a solution of HC1 and HF, and remaining plant debris was

18、removed by filtration. Methods for preventing formation of less soluble fluorosilicates were discussed. 11.2.2.2. Spectrometric analysis of dissolved silicon Although dissolved Si can be determined by atomic absorption

19、spectrometry (AAS) using a nitrous oxide-acetylene flame (Eaton et al., 1995) or by inductively coupled atomic plasma spectrometry (ICP, ICAP) (Jones and Dreher. 1996), it is probably most often determined by either ma

20、nual or automated colorimetry because of the lower cost of the instrumentation, and the lower detection limits. Silicon is determined colorimetrically (light absorption spectrometry) either by the yellow silicomolybdic

21、acid procedure or by the blue silicomolybdous acid procedure. The latter generally is preferred because of its greater sensitivity. The two methods are similar, except that the blue color is developed through the addit

22、ion of a reducing solution. The sample containing dissolved Si is reacted with ammonium molybdate (Kilmer, 1965; Hallmark et al., 1982). Tartaric acid is added to minimize interference by P in the form of a phosphomol

23、ybdate complex. After reduction with a solution containing sodium sulfite, sodium bisulfite, and 1-amino-2-naphthol-4-sulfonic acid, the intensity of the blue color that develops is measured at 650 rag. This method wil

24、l detect as little as 0.02 mg Si L -1 (Bunting, 1944). Both the yellow silicomolybdic acid method and the blue silicomolybdous acid procedure are presented in Standard Methods (Eaton et al., 1995) as method 4500-Si D a

25、nd 4500-Si E, respectively. The latter can be conducted with automated colorimetry analytical instruments (Method 4500-Si F in Eaton et al., 1995), which is useful for large sample numbers. 11.2.2.3. Non-destructive s

26、pectrometric methods for determining total silicon Several modern techniques have been used to determine the total Si content of soils, plants, and fertilizers without pre-analysis solubilization of tile matrix. X-ray fl

27、uorescence spectroscopy (XRFS), which also is known as X-ray emission spectrography or X-ray spectrochemical analysis, assesses the presence and concentration of Si in soil and plant materials by measuring the charact

28、eristic secondary radiation emitted from a sample that has been excited with an x-ray source (Karathanasis and Hajek, 1996). Although certain limitations exist, excellent equipment has been developed in recent years, m

29、aking it possible to rapidly analyze a great variety of samples. Near infra-red spectroscopy (NIRS) also has been used to non-destructively determine Si in various materials. There is a sound chemistry basis for using t

30、his method for determining the content of water and nitrogen in samples, but for other elements and constituents the basis is less clear. Statistical associations between NIRS spectra of standard samples and unknowns