Quantitative determination of poly(vinylpyrrolidone) by "on-line" pyrolysis coupled to gas chromatography

Abstract

"On-line" pyrolysis coupled with gas chromatography (GC) was performed for quantitative determination of poly(vinylpyrrolidone) (PVP) in wastewater sample. Gas chromatography-mass spectrometry (GC-MS) showed that the main product of pyrolysis of PVP, at high temperatures, is N-vinylpyrrolidone (NVP). After that, different amounts of commercial PVP were pyrolyzed in order to establish correlation between the amount of generated NVP (its GC peak area) and the initial mass of pyrolyzed PVP. GC-FID analysis was used for construction of calibration curve and for quantitative determination of PVP. Very good linear correlation was obtained between the area of NVP peak, generated during pyrolysis, and the initial mass of PVP (r2 = 0.998). Further, solutions of known concentration of PVP were prepared in destilled water ("spiked samples"). Spiked samples were preextracted with diethyl ether and n-hexane, and after that, the water-layer was evaporated and dissolved again in methanol. Analysis of pyrolysates of preextracted spiked samples showed that the "recovery" of PVP was above 96 mas%. This finding suggested that pre-extraction could be applied to reduce the concentration of organic substances that could also be pyrolyzed, and thus hinder identification and quantitative determination of PVP, without significant loss of polymer. The sample of an industrial wastewater from Pancevo, Serbia was investigated in the last part of this work. The sample was preextracted in the same way as the spiked samples and than pyrolyzed. NVP was identified by GC-MS in obtained pyrolysate, which was the evidence that PVP was present in the wastewater sample. NVP was quantified on the basis of the peak area in GC-FID chromatogram, and than the concentration of PVP in wastewater sample was calculated based on calibration curve. Concentration of PVP in industrial wastewater amounted 2.5 mg/L.