| Author/Editor | Kovačevič, Miroslav; Kač, Milica | |
| Title | Uporaba prečiščenega toluena za določevanje vsebnosti alfa-kislin v hmelju | |
| Translated title | Use of recycled toluene for determination of alpha-acid content in hops | |
| Type | članek | |
| Source | Hmelj Bilt | |
| Vol. and No. | Letnik 6 | |
| Publication year | 1999 | |
| Volume | str. 59-64 | |
| Language | slo | |
| Abstract | Content of alpha-acids in hops is an important criterion for the evaluation of hop quality. Several methods are available to determine this parameter. Four most commonly used are: determination of lead conductance value, modified Wollmer analysis, high performance liquid chromatography and spectrofotometric method. From all listed, the first one is most frequently used on Institute of Hop Research and Brewing Žalec. This is a conductometric titration. It consists of extraction of hop sample with toluene, dilution of aliquot with methanol and titration with lead acetate. Equivalent point is detected by monitoring of conductivity. A lot of waste toluene is obtained during the procedure. On the Department of agrochemistry a method to recycle the toluene from the hop extract has been intoduced. The method is based on its distillation and liquid-liquid extraction with lead acetate water solution. Comparison tests proved that recycled toluene is suitable for determination of hop alpha-acids. | |
| Summary | Količina alfa-kislin v hmelju je pomemben kriterij za njegovo kvaliteto. Vsebnost alfa-kislin lahko določamo na več načinov. Štiri najpogosteje uporabljene metode so: določevanje konduktometrične vrednosti, modificirana Wollmerjeva analiza, tekočinska kromatografija visoke ločljivosti in spektrofotometrična metoda. Od vseh naštetih se v praksi na In{titutu za hmeljarstvo in pivovarstvo največ uporablja prva. To je konduktometrična titracija, pri kateri gre za ekstrakcijo alfa-kislin iz vzorca hmelja s toluenom, redčenje alikvota z metanolom in titracijo s svinčevim acetatom. Ekvivalentno točko določimo konduktometrično. Pri postopku izluževanja s toluenom dobimo večjo količino odpadne kemikalije. Na Oddelku za agrokemijo smo vpeljali postopek, s katerim odpadni toluen očistimo do te mere, da je zopet uporaben za ekstrakcijo hmelja. Hmeljni ekstrakt destiliramo in destilat ekstrahiramo z vodno raztopino svinčevega acetata. S primerjalnimi poskusi smo ugotovili, da je prečiščen toluen primeren za določevanje alfa-kislin v hmelju s konduktometrično metodo. | |
| Descriptors | CROPS, AGRICULTURAL TOLUENE BENZENE DERIVATIVES CONDUCTOMETRY |