Electrochemical and UV/VIS Study of L-Histidine and Its Complexes with Cobalt and Nickel

In this work oxido-reduction properties of L-histidine were studied by cyclic and differential pulse voltammetry in a pH range from pH 4–10. The results have shown that L-histidine is not electroactive in a pH range from pH 4 to pH 9, while oxidation peak of L-histidine’s imidazole ring at pH 10 was detected with differential pulse voltammetry. It has been found that the oxidation peak current of L-histidine increased with the increase of its concentration in a solution. Adsorption of oxidation product of L-histidine on a glassy carbon electrode surface was also detected. Voltammetric techniques (cyclic and differential pulse voltammetry) and UV/VIS spectroscopy were used to study formation of L-histidine complexes with transition metals. It has been found that L-histidine formed octahedral complex with metal ion (Co2+ and Ni2+) in a 1 : 1 ratio. This work is licensed under a Creative Commons Attribution 4.0 International License

Application of Spectrophotometric Fingerprint in Cluster Analysis for Starch Origin Determination

Botaničko podrijetlo škroba je od velike važnosti za primjenu u industriji i proizvodnji hrane jer može bitno utjecati na svojstva krajnjeg proizvoda. Trenutno dostupne mikroskopske metode za određivanje podrijetla škroba su dugotrajne. Škrob se sastoji od amiloze i amilopektina, čiji omjer ovisi o njegovom botaničkom podrijetlu. Trijodidni ioni se obično vežu za amilozu i amilopektin, a njihovo vezivanje ovisi o podrijetlu škroba. U ovom je istraživanju mjeren apsorpcijski spektar kompleksa škrob-trijodid različitih vrsta, kao što su pšenica, krumpir, kukuruz, raž, ječam, riža, tapioka i škrob nepoznatog podrijetla, te različitih sorata iste vrste. Svaki je uzorak škroba imao specifične parametre: maksimalnu valnu duljinu pika za kompleks škrob-trijodid (λmax/nm), maksimalnu promjenu apsorbancije pri λmax (ΔA) i pomak λmax prema uzorku škroba nepoznatog botaničkog podrijetla. Vidljivi je dio apsorpcijskog spektra (500-800 nm) za svaki uzorak škroba dao jedinstveni otisak, koji je zatim obrađen klaster analizom. Tom su analizom podaci razdvojeni u dva klastera, jedan klaster žitarica i drugi klaster krumpira, tapioke i riže. Unutar klastera škrobova žitarica u podklastere su se izrazito razdvojili škrobovi pšenice, ječma i raži od kukuruznih škrobova. Podaci o sortama dobro su se grupirali unutar istog podklastera. Predložena metoda, koja kombinira klaster analizu i podatke dobivene mjerenjem apsorbancije vidljivog dijela spektra kompleksa škrob-trijodid, uspješno je razvrstala škrobove na osnovi njihove pripadnosti vrstama te sortama unutar iste vrste. Metoda je jednostavnija i praktičnija za uporabu od standardnih dugotrajnih metoda.The botanical origin of starch is of importance in industrial applications and food processing because it may influence the properties of the final product. Current microscopic methods are time-consuming. Starch consists of an origin-dependent amylose/amylopectin ratio. Triiodide ions bind characteristically to the amylose and amylopectin depending on the botanical origin of the starch. The absorbance of the starch-triiodide complex was measured for wheat, potato, corn, rye, barley, rice, tapioca and unknown origin starch, and within the different cultivars. Each starch sample had specific parameters: starch-triiodide complex peak wavelength maximum (λmax/nm), maximum absorbance change at λmax (ΔA) and λmax shift towards the unknown origin starch sample values. The visible absorption spectra (500-800 nm) for each starch sample were used as a unique fingerprint, and then elaborated by cluster analysis. The cluster analysis managed to distinguish data of two clusters, a cereal type cluster and a potato/tapioca/rice starch cluster. The cereal subclusters extensively distinguished wheat/barley/rye starches from corn starches. Data for cultivars were mostly in good agreement within the same subclaster. The proposed method that combines cluster analysis and visible absorbance data for starch-triiodide complex was able to distinguish starch of different botanical origins and cultivars within the same species. This method is simpler and more convenient than standard time-consuming methods

Surfactants: Methods for determination and removal of surfactants in environment

Površinski aktivne tvari ili tenzidi su tvari koje smanjuju površinsku napetost tekućina. Iako je danas većina tenzida biorazgradiva i ekološki prihvatljiva važno ih je kvantificirati jer lako dospijevaju u okoliš i zbog svojih svojstava imaju toksično djelovanje na organizme, sprječavaju razmjenu kisika na površini, te se akumuliraju u mikroorganizmima, biljkama, životinjama, sedimentu i tlu. Analitičke metode kojima se određuju tenzidi mogu se podijeliti u nekoliko skupina: titracijske (vizualne, potenciometrijske, tenzidimetrijske, turbidimetrijske), spektrofotometrijske (MBAS-metoda), kromatografske (tekućinska kromatografija visoke djelotvornosti-HPLC, tankoslojna kromatografija, plinska), analiza injektiranjem u protok i dr. Uklanjanje površinski aktivnih tvari iz vode provodi se na uređajima za pročišćavanje otpadnih voda fizikalno-kemijskim i biološkim postupcima dok se u kanalizacijskom sustavu i okolišu odvija se biorazgradnja tenzida.Surfactants reduce the surface tension of liquids. Surfactants are mostily biodegradable and environmentally friendly, it is still important to quantify them because they can easily reach the environment and couse toxic effects in organisms, they are a barier for surface oxygene exchange, and they accumulate in microorganisms, plants, animals, sediment and soil. Analytical methods usualy used for surfactant analysis are: titrations (visual, potentiometric, tensidimetric, turbidimetric), spectrophotometric (MBAS-method), chromatographic (high performance liquid chromatography-HPLC, thin layer chromatography), flow-injection methods, etc. Removal of surfactants from waters is carried out on wastewater treatment plants by physico-chemical and biological processes and trough the biodegradation in the sawage system and in environment

Utjecaj površinski aktivnih tvari na okoliš

Površinski aktivne tvari ili tenzidi su tvari koje smanjuju površinsku napetost tekućine. Sastoje se od hidrofilnoga i hidrofobnoga dijela i upravo zbog toga imaju tendenciju skupljanja na granici dviju faza. Velika primjena površinski aktivnih tvari u različitim granama industrije i kućanstvu potaknula je pitanje o utjecaju tenzida na okoliš, ali i na ljudsko zdravlje. Zbog sve veće primjene tenzida raste i njihova potreba za proizvodnjom pa godišnja svjetska proizvodnja tenzida iznosi oko 23 milijuna tona. Prema hidrofilnim skupinama unutar strukture tenzida dijele se na: anionske, kationske, neionske i amfolitske. Iako je danas većina tenzida biorazgradiva i ekološki prihvatljiva važno ih je kvantificirati jer svojim svojstvima lako dospijevaju u okoliš. Njihov najveći problem je toksično djelovanje, akumulacija u mikroorganizmima, biljkama, životinjama, sedimentu i tlu. Muljem i tekućinama dospijevaju u tla, a nepoznatim putem u atmosferu

Potentiometric Surfactant Sensor Based on 1,3-Dihexadecyl-1H-benzo[d]imidazol-3-ium for Anionic Surfactants in Detergents and Household Care Products

A 1, 3-dihexadecyl-1H-benzo[d]imidazol-3-ium- tetraphenylborate (DHBI-TPB) ion-pair implemented in DHBI-TPB surfactant sensor was used for the potentiometric quantification of anionic surfactants in detergents and commercial household care products. The DHBI-TPB ion-pair was characterized by FTIR spectroscopy and computational analysis which revealed a crucial contribution of the C–H∙∙∙π contacts for the optimal complex formation. The DHBI-TPB sensor potentiometric response showed excellent analytical properties and Nernstian slope for SDS (60.1 mV/decade) with LOD 3.2 × 10−7 M ; and DBS (58.4 mV/decade) with LOD 6.1 × 10−7 M was obtained. The sensor possesses exceptional resistance to different organic and inorganic interferences in broad pH (2–10) range. DMIC used as a titrant demonstrated superior analytical performances for potentiometric titrations of SDS, compared to other tested cationic surfactants (DMIC > CTAB > CPC > Hyamine 1622). The combination of DHBI-TPB sensor and DMIC was successfully employed to perform titrations of the highly soluble alkane sulfonate homologues. Nonionic surfactants (increased concentration and number of EO groups) had a negative impact on anionic surfactant titration curves and a signal change. The DHBI-TPB sensor was effectively employed for the determination of technical grade anionic surfactants presenting the recoveries from 99.5 to 101.3%. The sensor was applied on twelve powered samples as well as liquid-gel and handwashing home care detergents containing anionic surfactants. The obtained results showed good agreement compared to the outcomes measured by ISE surfactant sensor and a two-phase titration method. The developed DHBI-TPB surfactant sensor could be used for quality control in industry and has great potential in environmental monitoring

Water for all : Proceedings of the 7th international scientific and professional conference Water for all

The 7th International Scientific and Professional Conference Water for all is organized to honour the World Water Day by the Josip Juraj Strossmayer University of Osijek, European Hygienic Engineering & Design Group (EHEDG), Danube Parks, Croatian Food Agency, Croatian Water, Faculty of Food Technology Osijek, Faculty of Agriculture in Osijek, Faculty of Civil Engineering Osijek, Josip Juraj Strossmayer University of Osijek Department of Biology, Josip Juraj Strossmayer University of Osijek Department of Chemistry, Nature Park “Kopački rit”, Osijek- Baranja County, Public Health Institute of the Osijek- Baranja County and „Vodovod-Osijek“ -water supply company in Osijek. The topic of World Water Day 2017 was "Wastewater" emphasizing the importance and influence of wastewater treatments on global environment. The international scientific and professional conference Water for all is a gathering of scientists and experts in the field of water management, including chemists, biologists, civil and agriculture engineers, with a goal to remind people about the significance of fresh water and to promote an interdisciplinary approach and sustainability for fresh water resource management. The Conference has been held since 2011. About 300 scientists and engineers submitted 95 abstracts to the 7th International Scientific and Professional Conference Water for all, out of which 33 was presented orally and 62 as posters. 47 full papers were accepted by the Scientific Committee. 38 full papers became the part of the this Proceedings while 9 papers were accepted for publication in Croatian Journal of Food Science and Technology and Electronic Journal of the Faculty of Civil Engineering Osijek - e-GFOS

Utjecaj površinski aktivnih tvari na okoliš

Površinski aktivne tvari ili tenzidi su tvari koje smanjuju površinsku napetost tekućine. Sastoje se od hidrofilnoga i hidrofobnoga dijela i upravo zbog toga imaju tendenciju skupljanja na granici dviju faza. Velika primjena površinski aktivnih tvari u različitim granama industrije i kućanstvu potaknula je pitanje o utjecaju tenzida na okoliš, ali i na ljudsko zdravlje. Zbog sve veće primjene tenzida raste i njihova potreba za proizvodnjom pa godišnja svjetska proizvodnja tenzida iznosi oko 23 milijuna tona. Prema hidrofilnim skupinama unutar strukture tenzida dijele se na: anionske, kationske, neionske i amfolitske. Iako je danas većina tenzida biorazgradiva i ekološki prihvatljiva važno ih je kvantificirati jer svojim svojstvima lako dospijevaju u okoliš. Njihov najveći problem je toksično djelovanje, akumulacija u mikroorganizmima, biljkama, životinjama, sedimentu i tlu. Muljem i tekućinama dospijevaju u tla, a nepoznatim putem u atmosferu

Efficacy of long-term ultrasonography in follow-up of patients with papillary thyroid carcinoma: a case of neck metastasis developed 19 years following primary treatment

The cases of relapse in papillary thyroid cancer patients who were initially considered low-risk and for many years were without signs of the disease are extremely rare, but exist. This is supported by the clinical case of a patient who underwent a total thyroidectomy due to papillary thyroid cancer and 19 years later metastasis with extracapsular spreading in a presumed thyroid place was revealed. Due to such cases, the importance of long-term ultrasound monitoring is emphasized

The Influence of Plasticizers on the Response Characteristics of the Surfactant Sensor for Cationic Surfactant Determination in Disinfectants and Antiseptics

Surfactant liquid-membrane type sensors are usually made of a PVC, ionophore and a plasticizer. Plasticizers soften the PVC. Due to their lipophilicity, they influence the ion exchange across the membrane, ionophore solubility, membrane resistance and, consequently, the analytical signal. We used the DMI-TPB as an ionophore, six different plasticizers [2-nitrophenyl-octyl-ether (P1), bis(2-ethylhexyl) phthalate (P2), bis(2-ethylhexyl) sebacate (P3), 2-nitrophenyl phenyl ether (P4), dibutyl phthalate (P5) and dibutyl sebacate (P6)] and a PVC to produce ionic surfactant sensors. Sensor formulation with P1 showed the best potentiometric response to four usually used cationic surfactant, with the lowest LOD, 7 × 10−7 M; and potentiometric titration curves with well-defined and sharp inflexion points. The sensor with P6 showed the lowest analytical performances. Surfactant sensor with P1 was selected for quantification of cationic surfactant in model solutions and commercial samples of disinfectants and antiseptics. It showed high accuracy and precision in all determinations, with recovery from 98.2 to 99.6, and good agreement with the results obtained with surfactant sensor used as a referent one, and a standard two-phase titration method. RDS values were lower than 0.5% for all determinations

A New, MWCNT-Based, Solid-State Thiabendazole-Selective Sensor

Direct potentiometric measurements using solid-state sensors have a great potential for thiabendazole (TBZ) determination, considering simplicity, accuracy, and low cost. Modifying the sensing material of the sensor with multi-walled carbon nanotubes (MWCNTs) leads to improved analytical properties of the sensor. In this study, a new potentiometric solid-state sensor for TBZ determination, based on MWCNTs modified with a sulfate group, and TBZ ion as sensing material was developed. The sensor exhibited a Nernstian response for TBZ (60.4 mV/decade of activity) in a working range between 8.6 × 10−7 and 1.0 × 10−3 M. The detection limit for TBZ was 6.2 × 10−7 M. The response time of the sensor for TBZ was 8 s, and its signal drift was only 1.7 mV/h. The new sensor is applicable for direct potentiometric determination of TBZ in complex real samples, such as fruit peel. The accuracy of TBZ determination is confirmed using the standard addition method