Analytical methods and quality assurance:bDetermination of Sulphur in Plant Extracts by Ion Chromatograph - Hydraulic High-Pressure Nebulizer - Inductively Coupled Plasma Atomic Emission Spectrometer (IC/HHPN/ICP-AES)

The method for speciation and quantitative analysis of inorganic sulphur form, sulphate and organic sulphur compounds by using high performance ion chromatography (IC) with inductively coupled plasma atomic emission spectrophotometry (ICP-AES) has been developed. An ICP-AES was operated as a detector of IC. To achieve a lower detection limit a hydraulic high-pressure nebulizer was used for connection between IC and ICP. This hyphenated system was used for the separation and determination of organic sulphur compounds and sulphate ions. By using an anion exchange column, with 2.5 mM phthalic acid, adjusted with TRIS to pH=4.2, all of the organic sulphur forms were measured together as a first (pseudo) peak (Nieto and Frankenberger, 1985) at 2.0 min., while the sulphate ion was retained on the column and its peak appeared with retention time at 4.2 min. Other inorganic sulphur forms (sulphide, sulphite, thiosulphate etc.) were not detectable in the water extracts from the examined plants. The sulphide and sulphite peaks were observed between the organic sulphur and sulphate peaks, but the developed method was not optimised for their separation. The sulphur was detected on the polychromator of ICP-AES on 180.734 nm. The detection limits were 0.023 mg L -1 and 0.085 mg L -1 of sulphate-sulphur and of organic-sulphur respectively. Water extracts of standard wheat straw and grain samples were analysed.