The Effect of Mechanical Mixing, Temperature and Citrate Concentration on the Calcium Oxalate Precipitation

Kalcijevi oksalati su kalcijeve soli oksalne kiseline i sastavni su dio gotovo svih bubrežnih kamenaca. Bubrežni kamenci posljedica su rasta kristala u urinarnom traktu, a gotovo 10% ljudi susretne se s tim problemom tijekom života. U medicinskom je rječniku proces nastajanja bubrežnih kamenaca poznatiji pod nazivom urolitijaza ili nefrolitijaza. Upravo se zbog te činjenice sve češće provode istraživanja kojima bi se u potpunosti objasnio mehanizam, uvjeti i moguća prevencija nastajanja bubrežnih kamenaca. Kalcijev oksalat kristalizira u tri hidratna oblika: termodinamički stabilan kalcijev oksalat monohidrat (vevelit, COM), metastabilan dihidrat (vedelit, COM) te trihidrat (kaoksit, COT) koji se rijetko pronalazi u kemijskom sastavu bubrežnih kamenaca. Eksperimentalno je pokazano da promjena temperature i koncentracije citrata može utjecati na taloženje kalcijeva oksalata te na morfologiju i veličinu nastalih kristala. Rezultati su obrađeni FTIR spektroskopijom, TG analizom i optičkom mikroskopijom.Calcium oxalates are calcium salts of oxalic acid and they are the most common constituents of kidney stones. Kidney stones are the result of a crystal growth in the urinary tract and almost 10% of population experience such problems during their lifetime. Medical term of this process is known as the urolithiasis or nefrolithiasis. There have been many studies conducted with the aim to understand and explain the mechanism, precipitation conditions and possible prevention of the stone formation. Calcium oxalate crystallizes in three hydrate forms: thermodynamically stable monohydrate (whewellite, COM), the metastable modification, dihydrate (weddellite, COD) and trihydrate (caoxite, COT) which is rarely found in the kidney stones. The experimental results showed that a temperature changes and a concentration of citrate can influence morphology and size of precipitated crystals. Calcium oxalate crystals were studied by the means of thermal analysis (TGA) and infrared (FT-IR) spectroscopy. The morphology of calcium oxalate crystals was studied using the optical microscope

Precipitation of Calcium Oxalate in Artificial Urine

U ovom diplomskom radu provedena su sustavna istraživanja spontanog taloženja kalcijeva oksalata u kompleksnom sustavu umjetnog urina u uvjetima hiperoksalurije. Taložni sustavi su optimizirani kako bi se ujedno imitirali fiziološki i patološki uvjeti ($\theta = 37^{\circ}C$, $pH_{i}$ = 5,0 i $pH_{i}$ = 9,0) u širem koncentracijskom području kalcija (2,0 mmol $dm^{-3}$ ≤ $c_{i}\left ( Ca^{2+} \right )$ ≤ 10,0 mmol $dm^{-3}$) te koncentracijskom području oksalata (0,6 mmol $dm^{-3}$ ≤ $c_{i}\left ( C_{2}{O_{4}}^{2-} \right )$ ≤ 8,0 mmol $dm^{-3}$) kako bi se zadovoljio uvjet hiperoksalurije. Glavni cilj istraživanja je ispitivanje utjecaja kompleksnosti i $pH_{i}$ sustava te početne koncentracije reaktanata na taloženje i morfologiju kalcijeva oksalata u patološkim uvjetima. U svim taložnim sustavima umjetnog urina dominantno taloži kalcijev oksalat monohidrat (COM), dok su značajne razlike uočene u sustavu umjetnog urina pri $pH_{i}$ = 9,0 u koncentracijskom području $c_{i}\left ( C_{2}{O_{4}}^{2-} \right )$ ≥ 6,0 mmol $dm^{-3}$ i $c_{i}\left ( Ca^{2+} \right )$ ≥ 7,5 mmol $dm^{-3}$ gdje taloži smjesa COM i kalcijeva oksalata dihidrata (COD). Također su uočene i morfološke razlike između taložnih sustava: u umjetnom urinu talože kristali nepravilnih oblika s tendencijom agregacije, što je posebno izraženo u sustavima više prezasićenosti.In this Thesis, systematic research of spontaneous precipitation of calcium oxalate in the artificial urine system with increased complexity mimicking the conditions of hyperoxaluria was conducted. The precipitation systems have been optimized in order to emulate physiological and pathological conditions ($\theta = 37^{\circ}C$, $pH_{i}$ = 5.0 and $pH_{i}$ = 9.0) over a wide range of initial reactant concentrations of calcium (2.0 mmol $dm^{-3}$ ≤ $c_{i}\left ( Ca^{2+} \right )$ ≤ 10.0 mmol $dm^{-3}$) and oxalate (0.6 mmol $dm^{-3}$ ≤ $c_{i}\left ( C_{2}{O_{4}}^{2-} \right )$ ≤ 8.0 mmol $dm^{-3}$) with the aim of establishing hyperoxaluria conditions. The main aim of this research is to investigate the effects of system complexity, initial $pH_{i}$ and reactant concentration on precipitation and morphology of calcium oxalate under pathological conditions. In all precipitation systems, dominant precipitation of calcium oxalate monohydrate (COM) was observed, except in the artificial urine system at $pH_{i}$ = 9.0, in the concentration range $c_{i}\left ( C_{2}{O_{4}}^{2-} \right )$ ≥ 6.0 mmol $dm^{-3}$ and $c_{i}\left ( Ca^{2+} \right )$≥ 7.5 mmol $dm^{-3}$ where a mixture of COM and calcium oxalate dihydrate (COD) precipitated. The significant difference in crystal morphology was observed: irregular crystals with pronounced aggregation tendency have precipitated in the artificial urine, particularly in the systems with increased supersaturation

The Effect of Mechanical Mixing, Temperature and Citrate Concentration on the Calcium Oxalate Precipitation

Kalcijevi oksalati su kalcijeve soli oksalne kiseline i sastavni su dio gotovo svih bubrežnih kamenaca. Bubrežni kamenci posljedica su rasta kristala u urinarnom traktu, a gotovo 10% ljudi susretne se s tim problemom tijekom života. U medicinskom je rječniku proces nastajanja bubrežnih kamenaca poznatiji pod nazivom urolitijaza ili nefrolitijaza. Upravo se zbog te činjenice sve češće provode istraživanja kojima bi se u potpunosti objasnio mehanizam, uvjeti i moguća prevencija nastajanja bubrežnih kamenaca. Kalcijev oksalat kristalizira u tri hidratna oblika: termodinamički stabilan kalcijev oksalat monohidrat (vevelit, COM), metastabilan dihidrat (vedelit, COM) te trihidrat (kaoksit, COT) koji se rijetko pronalazi u kemijskom sastavu bubrežnih kamenaca. Eksperimentalno je pokazano da promjena temperature i koncentracije citrata može utjecati na taloženje kalcijeva oksalata te na morfologiju i veličinu nastalih kristala. Rezultati su obrađeni FTIR spektroskopijom, TG analizom i optičkom mikroskopijom.Calcium oxalates are calcium salts of oxalic acid and they are the most common constituents of kidney stones. Kidney stones are the result of a crystal growth in the urinary tract and almost 10% of population experience such problems during their lifetime. Medical term of this process is known as the urolithiasis or nefrolithiasis. There have been many studies conducted with the aim to understand and explain the mechanism, precipitation conditions and possible prevention of the stone formation. Calcium oxalate crystallizes in three hydrate forms: thermodynamically stable monohydrate (whewellite, COM), the metastable modification, dihydrate (weddellite, COD) and trihydrate (caoxite, COT) which is rarely found in the kidney stones. The experimental results showed that a temperature changes and a concentration of citrate can influence morphology and size of precipitated crystals. Calcium oxalate crystals were studied by the means of thermal analysis (TGA) and infrared (FT-IR) spectroscopy. The morphology of calcium oxalate crystals was studied using the optical microscope

Intensification of Polyphenols Extraction from Mandarin Peel by High Voltage Electric Discharge: Effect of Process Parameters and Optimisation

Konzumacija svježih citrusa, ali i njihova prerada generiraju nusproizvode, kao što su kora, sjemenke, pulpa, kao i otpadne vode. Cilj ovog istraživanja je valorizacija agroindustrijskih nusproizvoda (kore citrusa) kao vrijedne sirovine za ekstrakciju polifenola primjenom inovativne netermalne metode ekstrakcije sa zelenim otapalom (voda). U ekstraktima je kvantificirano i identificirano ukupno šest fenolnih spojeva. Pri tome je promatran utjecaj vremena (od 5 do 15 min), frekvencije (od 40 do 100 Hz) i omjera kapljevito/kruto (od 200 do 400 ml g–1) na efikasnost procesa ekstrakcije (iskorištenje) i udio dominantnih fenolnih spojeva (hesperidina i narirutina). Uz pomoć metode odzivnih površina definirani su optimalni parametri promatranog procesa ekstrakcije za svaki od istraživanih odziva, i to za iskorištenje (285,93 ml g–1, 73,38 Hz i 14,84 min), za hesperidin (366,19 ml g–1, 97,56 Hz i 5,1 min) te za narirutin (200 ml g–1, 70 Hz i 15 min). Ekstrakcija potpomognuta visokonaponskim električnim pražnjenjem (HVED ekstrakcija) pokazala se pogodnom za ekstrakciju fenolnih spojeva, pri čemu je izbjegnuta uporaba organskih otapala.The peel of the Okitsu variety of mandarin is created as a by-product of the fruit’s growth and processing. The primary goal of this research was to use a unique nonthermal extraction method (high-voltage electric discharge assisted) with green solvent (water) to valorise citrus peel as a valuable raw material. In October 2020, samples (citrus peel) were collected from the farm of Mr. Dalibor Ujević (Opuzen, Hrvatska). Samples were washed, freeze-dried, and sieved before extraction. The effects of extraction process parameters, such as treatment duration (5–15 min), frequency (40–100 Hz), and liquid to solid ratio (200–400 ml g–1) on the extraction yield and content of hesperidin and narirutin were studied. Spectrophotometric methods were used to assess the antiradical activity and total phenolic content of the extracts. Individual phenolic components were identified and quantified using HPLC method. The extraction process parameters were optimised with a commercial softer tool (Design Expert®) using experimental data gathered using the Box-Behnken experimental design. Experiments were conducted as shown in Tables 1 and 2. The extraction yield was ranked from 359.23 to 463.20, the total phenol values ranged from 96.23 to 275.46 mg GAE l–1, DPPH values ranged from 87.08 to 94.93 %. Total phenol content and antiradical activity decreased with increasing extraction time, as shown in Fig. 1. Six phenolic compounds were identified and quantified, predominated by hesperidin and narirutin (Table 3). The regression models for all tested HVED extraction responses were significant (p-value under 0.05) based on the acquired data, and the quality of the models produced was evaluated based on the coefficients of determination (R2) and Lack of Fit value. The obtained R2 values for all models developed were 0.911; 0.844, and 0.845 with a nonsignificant lack of fit, indicating an adequate relationship between input parameters (extraction conditions) and observed variable, in this case, extraction efficiency, hesperidin and narirutin content (Table 4). The obtained data was utilised to create three-dimensional (3D) response surface graphs, as shown in Figs. 2–4. The regression models within this study were predicted by Eqs. (1)–(3). With response surface methodology (RSM), optimal parameters of HVED extraction process were defined, as follows: extraction yield (285.93 ml g–1, 73.38 Hz and 14.84 min), hesperidin content (366.19 ml g–1, 97.56 Hz, and 5.1 min), and narirutin content (200 ml g–1, 70 Hz, and 15 min), as presented in Table 5, together with predicted and experimentally verified values

ELECTROCHEMICAL DETECTION OF VITAMIN C IN REAL SAMPLES

Electrochemical properties of vitamin C (also known as L-ascorbic acid) have been studied by cyclic and differential pulse voltammetry in the model systems in order to develop simple and suitable method for vitamin C detection in real samples. The results indicated that vitamin C oxidation is a quasi-reversible and diffusion-controlled process, as well that the oxidation product of ascorbic acid, dehydroascorbic acid is adsorbed on the glassy carbon electrode surface. Calibration curve was constructed and the linear response was obtained in a concentration range from 0.0025 mol dm-3 to 1.0 mol dm-3. Vitamin C was successfully determined in real samples (fruit juices and food supplement) with cyclic voltammetry within concentration range from 0.034 mol dm-3 to 0.340 mol dm-3. In addition, antioxidant activity of vitamin C in real samples was determined using DPPH assay with a good linear correlation obtained between the cyclic voltammetry results and the results evaluated by DPPH assay of the samples

Extraction of Bioactive Compounds from Tobacco Waste using Deep Eutectic Solvents

Duhanski otpad je kruti otpad, a njegove vrste međusobno se razlikuju po granulaciji i mjestu izdvajanja u procesu proizvodnje. Cilj ovog rada bio je istražiti učinkovitost eutektičkih otapala u ekstrakciji bioaktivnih komponenti iz duhanskog industrijskog otpada (refabrikat, rebro i prašina). Ispitan je utjecaj procesnih parametara (vrijeme miješanja, temperatura i udio vode u otapalu) na svojstva samog ekstrakta (ukupne fenole, antiradikalnu aktivnost, udio klorogenske kiseline i rutina). Metodom odzivne površine određeni su optimalni parametri ekstrakcije (30 min, 70 °C, 29,99 % vode). Provedeno istraživanje ogleda se u maksimalnom iskorištavanju nusproizvoda duhanske industrije, a rezultira visokovrijednim ekstraktima koji se mogu implementirati u druge procese i proizvode. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna.Tobacco waste is a solid waste highly diverse in granulation and point of separation in the manufacturing process. The objective of this study was to investigate the efficacy of eutectic solvents in the extraction of bioactive compounds from tobacco waste. Influence of extraction parameters on the properties of the obtained extracts (total phenol, antioxidant activity, chlorogenic acid, and rutin) has been determined. Using response surface methodology, optimal parameters were defined (30 min, 70 °C, 29.99 % water). The meaning of the proposed research is reflected in the maximum utilization of the tobacco by-product in order to obtain extracts that can be implemented in other products and processes. This work is licensed under a Creative Commons Attribution 4.0 International License

Mechanochemical synthesis of calcium oxalate

Ova studija prikazuje mehanokemijsku sintezu kalcijeva oksalata u planetarnom kugličnom mlinu, bez i uz prisutnost otapala. Dosadašnja istraživanja su uglavnom bila usmjerena na otopinsku sintezu kalcijeva oksalata. U ovom radu opisujemo drugačiji pristup, koji će donijeti nova saznanja o sintezi kristala kalcijeva oksalata, a koje su uzrokovane utjecajem mehaničke energije. Cilj istraživanja je sinteza, identifikacija i karakterizacija pojedine oksalatne hidratne faze sintetizirane iz kalcijevih soli (klorida, nitrata i sulfata). Ispitivan je utjecaj brzine mljevenja i praćena je reakcija u ovisnosti o vremenu sinteze. Strukturalna i termička svojstva uzoraka ispitana su FTIR spektroskopijom i termogravimetrijskom analizom (TGA). Morfološke karakteristike kalcijeva oksalata te raspodjela veličine čestica određene su optičkom mikroskopijom i dinamičkim raspršenjem svjetlosti (DLS)

Calcium oxalate and gallic acid: structural characterization and process optimization toward obtaining high contents of calcium oxalate monohydrate and dihydrate

The search for an efficient drug or inhibitor in the formation process of kidney stones has been a promising research topic towards reducing the risks of the formation of disease. However, several challenges have been faced in investigating the most common constituents of kidney stones, calcium oxalate and its hydrate forms (COM, COD and COT). This study focuses on the preparation and structural characterization (TG, XRD, FTIR, SEM) of calcium oxalate hydrates in the presence of gallic acid (GA) and by varying operating parameters such as temperature (25 °C, 36.5 °C and 48 °C), pH (5.6, 6.5 and 7.5) and amount of added GA (ranging from 100 mg to 1000 mg). Response surface methodology was applied in order to evaluate the effects of operating parameters in the formation of COM and COD, and for the process optimization towards maximizing their content in samples. The results indicated that GA inhibited the formation of COM (0–100%) and promoted the formation of COD (0 ≤ 99%), while a medium pH and the amount of added GA showed a significant effect in the process of COD formation. In order to investigate the interactions established in the formation process and the possible adsorption between GA and the formed crystals, electrochemical measurements were performed