An automated turbidimetric method for total sulfur in plant tissue and sulfate sulfur in soils

Abstract

An automated turbidimetric method has been developed for the rapid and accurate determination of sulfate. The method is practical and useful for accurately measuring total sulfur in plant tissues, and extractable sulfate in soils. The principle of intermittent reagent addition is used which eliminates drift and sensitivity changes caused by coating of BaSO 4 on tubing and cell walls. Also, the appropriate chemistry is used to minimize interactions of the wash with the sample at a sampling rate of 30/H. The sensitivity of the method is excellent with a working range of 0 to 15 ppm sulfur for soils. For plant digests the sample solutions are diluted to 0-35 ppm S. The precision as determined by repeated analysis of a soil sample extract was 0.58% RSD with a mean of 9.26 pg/g extractable SO = 4 -S. On another soil sample using a different extractant and extraction procedure the RSD was 0.64%, mean of 9.26 μg/g. Multiple automated sulfur analyses on a plant tissue digest resulted in an RSD of 0.41% for a sample containing 0.21% S. The automated turbidimetric method for sulfate has excellent precision and sensitivity in plant tissue and soil analyses where gravimetric BaSO 4 assays are not practical. INTRODUCTIONIn the last few years there has been an increasing demand for sulfur analyses in agronomic investigations involving plant nutrition and soil fertility. Also, the analysis for sulfur has become increasingly important in the evaluation of the effects of industrial and power generation effluents on the environment. Our concern was directed toward the important need for a reliable, accurate, and sensitive method for the analysis of total sulfur in plant tissues and extractable sulfate in soils. Their exists a great need for a good method to rapidly analyze soils and plant materials because of the large numbers of samples involved and the low levels of sulfur present.A number of new instrumental techniques have been proposed for sulfur determinations. The reported techniques include the

Effect of season, soil type and fertilizer on the biomass production and chemical composition of five tropical shrub legumes with forage potential

“…In detail, exchangeable Al (extracted with 1 m KCl and determined by titration with NaOH 0·1 m ); available B (colorimetrically with Azometin after hot water extraction; Mahler et al. , 1984); total C (colorimetrically after potassium dichromate–sulphuric acid oxidation); exchangeable K, Na, Ca, Mg, Mn, Zn, Cu and Fe (extracted with neutral 1 m NH 4 ‐acetate and determined by atomic absorption spectrometry, Model 5000; Perkin Elmer, Norton, OH, USA), total N [determined by autoanalyser (Skalar Autoanalyzer; San Plus; Skalar Analytical, Breda, The Netherlands) following Kjeldahl digestion]; available P (Bray II) and sulphate‐S (calcium phosphate extraction and turbidimetric measurement with barium chloride; Wall et al. , 1980) were analysed.…”

“…Contents of Ca, Mg, K and Cu were determined with atomic absorption spectroscopy (Perkin Elmer) after nitric‐perchloric digestion (Benton and Jones, 1989). Sulphur was analysed after extraction with calcium phosphate via turbidimetric measurement with barium chloride (Wall et al. , 1980).…”

The effect of nitrogen fertilization and no‐till duration on soil nitrogen supply power and post–spring thaw greenhouse‐gas emissions

“…Organic N was calculated from the difference between total N and inorganic N. Extractable K was determined using 1.0M NH 4 OAc (Hendershot et al, 2008a) and analyzed using atomic emission (Varian Spectra 220 AAS; Varian Inc., Palo Alto, CA, USA). Extractable S was determined using 0.01M CaCl 2 (Hu et al, 2005) and analyzed using automated turbidimetry (Wall et al, 1980). Total soil C was measured using a LECO C632 Carbon Analyzer Leco (Corporation, St. Joseph, MI, USA).…”

Use of dialysis to limit interferences in the Turbidimetric determination of sulfate

“…Some baseline drift and sensitivity loss as a result of BaSO4 precipitation within the flow cell was noted, however, the effects were' slight and could be controlled by weekly flushing with an alkaline EDTA solution (Wall et al, 1980). Spiked samples produced recovery values ranging from 94 to 103% (data not presented).…”