Determination 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 fo rm, sulphate and organic sulphur compounds by using high performance ion ch romatography (IC) with inductively coupled plasma atomic emission spectroph otometry (ICP-AES) has been developed. An ICP-AES was operated as a detecto r of IC. To achieve a lower detection limit a hydraulic high-pressure nebul izer 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 aci d, adjusted with TRIS to pH=4.2, all of the organic sulphur forms were meas ured 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 app eared with retention time at 4.2 min. Other inorganic sulphur forms (sulphi de, sulphite, thiosulphate etc.) were not detectable in the water extracts from the examined plants. The sulphide and sulphite peaks were observed bet ween the organic sulphur and sulphate peaks, but the developed method was n ot optimised for their separation. The sulphur was detected on the polychro mator 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.