Search

Dalmatian pyrethrum (Tanacetum cinerariifolium /Trevir./ Sch. Bip.) synthesizes secondary metabolite pyrethrin, known for its potent insecticidal and repellent activity. The present study was aimed at optimizing the maceration extraction parameters that improve the efficiency of pyrethrin extraction from the dried Dalmatian pyrethrum flower heads. Extraction efficiencies under several conditions were investigated: different solvent types, extraction time, the rotational speed of the stirrer, and the solvent volume. The highest recovery values were obtained with 5 mL of acetone, at the rotational speed of 400 rpm, and the extraction time of three hours. In addition, the extraction efficiency of maceration was compared to that of ultrasound-assisted and matrix solid phase dispersion extraction, both previously optimized for pyrethrin extraction. The extractions were carried out on samples of three natural Dalmatian pyrethrum populations (Krk, Mt. Kozjak, and Senj). Both the total pyrethrin content and the HPLC profile varied between different extraction techniques. Across applied methods, the highest efficiency was observed with matrix solid phase dispersion extraction. Evaluation of the differences between data obtained using different extraction techniques was performed by the Bland-Altman analysis, revealing good agreement between the three methods.

Dalmatian pyrethrum (Tanacetum cinerariifolium /Trevir./ Sch. Bip.) synthesizes secondary metabolite pyrethrin, known for its potent insecticidal and repellent activity. The present study was aimed at optimizing the maceration extraction parameters that improve the efficiency of pyrethrin extraction from the dried Dalmatian pyrethrum flower heads. Extraction efficiencies under several conditions were investigated: different solvent types, extraction time, the rotational speed of the stirrer, and the solvent volume. The highest recovery values were obtained with 5 mL of acetone, at the rotational speed of 400 rpm, and the extraction time of three hours. In addition, the extraction efficiency of maceration was compared to that of ultrasound-assisted and matrix solid phase dispersion extraction, both previously optimized for pyrethrin extraction. The extractions were carried out on samples of three natural Dalmatian pyrethrum populations (Krk, Mt. Kozjak, and Senj). Both the total pyrethrin content and the HPLC profile varied between different extraction techniques. Across applied methods, the highest efficiency was observed with matrix solid phase dispersion extraction. Evaluation of the differences between data obtained using different extraction techniques was performed by the Bland-Altman analysis, revealing good agreement between the three methods.

U ovom tekstu razmatra se kako odabrati pufer ovisno o svrsi i kako ga pripraviti, pri čemu je navedeno nekoliko načina pripremanja puferskih otopina. Uz naglašeno nužno razumijevanje konstanti disocijacije kiselina, čitateljima se nastoji približiti ispravan način pripremanja željenih puferskih otopina. To se ponajprije odnosi na uzimanje u obzir svih faktora koji mogu utjecati na neki puferski sustav. U tekstu se zato obrađuju važni pojmovi i povezuju s njihovim primjenama u znanstvenom i inženjerskom svijetu. Također, pojašnjava se pojam kapaciteta pufera i njegova uloga, pojam ionske jakosti te na što ona utječe. Navedena su bitna svojstva koja pufer treba imati te kako produljiti trajanje puferskih otopina. Na kraju se može provjeriti što su zapravo puferi te su dani zadatci s ciljem samostalne provjere usvojenosti rješavanja računskih zadataka. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna., The text discusses how to choose buffers depending on the purpose, and how to prepare them in several ways. With the necessary understanding of acid dissociation constants and buffer mechanisms, it is meant to give the readers the correct approach when preparing desired buffer solutions by taking into account all factors that may affect the buffer system. Therefore, the text covers important concepts, and links them with their applications in the world of science and engineering. It also explains buffer capacity and its role, as well as the concept of ionic strength and how it affects the pH. At the end, explanations of buffers are summarized and some numerical problems are given to enable self-evaluation of the comprehension of the given subject. This work is licensed under a Creative Commons Attribution 4.0 International License.

Puferi su važni za mjerenje i održavanje vrijednosti pH koje je ključno u mnogobrojnim svakodnevnim znanstvenim i industrijskim djelatnostima. Stoga, cilj ovoga teksta je razjasniti fizikalno-kemijske parametre na kojima počivaju puferi. Obrađeno je kako se i zašto provodi umjeravanje članka za mjerenje pH. Navedeno je koji se problemi mogu pojaviti tijekom mjerenja pH i kako te probleme riješiti. Rad se bavi primjenom stečenog znanja u nastavi, kao i njihovom provjerom kroz primjere i računske zadatke. Navedenim praktičnim primjerima olakšano je usvajanje temeljnih pojmova vezanih uz pH i pufere. Tako je obrađeno kako pravilno definirati pH, što je Henderson-Hasselbalchova jednadžba i koja su joj ograničenja, kako vizualno provjeriti djelovanje pufera, koja je povezanost Le Chatelirova načela i pufera, o čemu treba voditi računa prilikom mjerenja pH. Među ostalim, navedena je i važnost utjecaja temperature kod umjeravanja pH-članka, mjerenja pH uzorka, ali i iskazivanja vrijednosti pH. Na kraju, navedeno je kako unaprijediti stečena znanja i vještine kroz pitanja povezana s vrijednostima pH i puferima. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna., Buffers are of high importance for pH measurement and control, which is crucial in many everyday scientific and industrial activities. The aim of this article was to elucidate the physicochemical parameters of buffers. Explained are the process and background of pH electrode calibration, as are described the problems that may arise in pH measurement, and their solutions. The focus of this article is the application and assessment of this knowledge in education through examples and numerical problems. The practical examples facilitate the learning of basic concepts related to pH and buffers. We clarify the correct definition of pH value, the Henderson-Hasselbalch equation and its limitations, the use of visual indicators with buffers, the connection between Le Chatelier’s principle and buffers, and what is important in pH measurement. A special mention is given to the influence of temperature in pH electrode calibration, pH measurement, and expressing the pH value. Finally, we suggest how to further improve the students’ knowledge and skills through questions on problems related to pH value and buffers. This work is licensed under a Creative Commons Attribution 4.0 International License.