Wyniki wyszukiwania - BazTech

1

Metody wyznaczania krytycznego stężenia micelarnego związków powierzchniowo czynnych

Grabowska Ola, Dywicki Paweł, Chmurzyński Lech

Wiadomości Chemiczne

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2020

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[Z] 74, 5-6

371--390

EN

Surface active agents, also known as surfactants, are a group of chemical compounds that are used in various products of the chemical industry. These compounds are components of medicines, detergents, motor oils and many others. The multitude of uses of surfactants makes it important to know their aggregation behaviour in solution. There are many methods used to analyse surfactants behaviour in liquid phase. The choice of a particular technique usually depends on the chemical structure of the surfactant. An example of a method that is used in studies of ionic surfactants is conductometry. This technique allows to study the dependence of specific conductivity on surfactant concentration, enabling determination of critical micellar concentration (CMC). Capillary electrophoresis is another example of the method used to determine the critical micellar concentration. It allows to make measurements in conditions where other methods fail, including conductometric method. Surfactant solutions differ in viscosity, which changes with the appearance of micelles in solution. Measurement of marker compound migration time through surfactant solutions of various concentrations allow to determine critical micellar concentration. Isothermal titration calorimetry (ITC) allows to study the thermal effects associated with the aggregation of surfactants into micelles. Based on the energy changes that occur during titration, the critical micellar concentration of surfactant can be precisely determined. ITC is very sensitive method, so basically it can be used to examine all types of surfactants. In addition, the ITC method allows to determine the thermodynamic parameters of the undergoing micellization process. The use of several measuring methods gives a more complete picture of the phenomena occurring in solutions. It allows to understand aggregation process more accurately. Therefore, CMC measurement are often made with the use of several complementary methods.

2

Efektywność filtracyjna i zmienność mineralizacji wody pitnej po filtracji wkładami Brita i Wessper

Wiercioch Jakub

Analit

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2020

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Nr 9

27--40

PL

W niniejszej pracy dokonano oceny jakości popularnych wkładów (zawierających jonity i węgiel aktywny) do dzbanków filtrujących w aspekcie osiąganego poziomu mineralizacji wody pitnej. Badania przeprowadzono dla dwóch rodzajów filtrów (Brita Maxtra+, Wessper Sport), oraz wody o różnym składzie chemicznym, tj. wody wodociągowej i butelkowanej: Żywiec Zdrój i Muszynianka. Mineralizację oceniano wykonując pomiary konduktometryczne przewodności właściwej oraz aktywności jonów sodu, potasu i wapnia w testowanych próbkach wód, przed i po przefiltrowaniu. Jako metodę analizy ilościowej interesujących pierwiastków zastosowano fotometrię płomieniową.

EN

In this study, the quality of popular cartridges (containing ion exchangers and activated carbon) for filter jugs was assessed in terms of the level of mineralization in drinking water. The research was carried out for two types of filters (Brita Maxtra +, Wessper Sport), and water of different chemical composition, i.e. tap and bottled water: Żywiec Zdrój and Muszynianka. The mineralization was assessed by conducting conductometric measurements of specific conductivity and the activity of sodium, potassium and calcium ions in the tested water samples, before and after filtering. Flame photometry was used as a method of quantitative analysis of the elements of interest.

3

The conductivity of the milk kefir model reduced by enzymatic hydrolysis of lactose content

Kaczyński Ł. K., Bierzuńska P., Cais-Sokolińska D.

Aparatura Badawcza i Dydaktyczna

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2016

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T. 21, nr 2

102--105

EN

Measurements of electrical values reflect the dynamics for development of lactic acid bacteria. They may be, in addition to pH measurement, a tool for a technologist to monitor the fermentation process and changes taking place in the finished product, in which the microflora is still active. It was stated that with lapse of fermentation time, the conductivity of each sample of milk that has undergone the souring process increased by 1.5 times. The values of direction coefficients for the linear distribution are consistent with the dynamics of pH changes for kefirs during their production. After 24 hours of fermentation, pH for samples of this milk was 4.42, and the conductivity – 7.213 Ωˉ³·cm¹. Measurement of conductivity of processed milk with the lactose content of 4.7% and less than 0.01% reflects the dynamics of the souring process.

PL

Pomiary wielkości elektrycznych odzwierciedlają dynamikę rozwoju bakterii kwasu mlekowego. Stanowić mogą, obok pomiaru pH, narzędzie dla technologa w monitorowaniu procesu fermentacji i zmian zachodzących w gotowym produkcie, w którym mikroflora nadal pozostaje aktywna. Stwierdzono, że wraz z upływem czasu fermentacji konduktywność każdej z próbek mleka poddanego ukwaszeniu zwiększyła się 1,5-krotnie. Wartości współczynników kierunkowych rozkładu liniowego są zbieżne z dynamiką zmian pH kefirów podczas ich wytwarzania. Po 24 h fermentacji pH próbek tego mleka wyniosło 4,42, a konduktywność 7,213 Ωˉ³·cm¹. Pomiar konduktywności przerabianego mleka o zawartości laktozy 4,7% i mniej niż 0,01% stanowi odzwierciedlenie dynamiki procesu ukwaszania

4

Rozszerzona metoda konduktometryczna w badaniach procesu hydratacji cementu glinowego

Nowacka M., Pacewska B.

Cement Wapno Beton

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2015

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R. 20/82, nr 4

225--234

PL

Badano wpływ temperatury i współczynnika w/c na przebieg hydratacji dwóch rodzajów cementów glinowych (ciemno-szarego i białego), głównie w oparciu o pomiary konduktometryczne. W tym celu skonstruowane naczyńko pomiarowe, które pozwalało na jednoczesny pomiar przewodnictwa elektrycznego i temperatury zaczynu. Wykonano ponadto pomiary kalorymetryczne i oznaczono skład zaczynu metodą analizy termicznej. Uzyskanych wyniki wykazały, że temperatura, w której przebiega hydratacja, decyduje o długości okresu indukcji, podczas gdy stosunek w/c = 0,35 lub 0,5 nie ma wpływu na szybkość procesu. Duże ciepło hydratacji zwiększa temperaturę zaczynu, co może spowodować konwersję nietrwałych hydratów glinianu wapnia w fazę C3AH6.

EN

The effect of temperature and w/c ratio on the hydration of two types of calcium aluminate cement (dark grey and white) was examined, mainly by conductometric measurements. For this purpose a specific cell was designed to monitor the electrical conductivity simultaneously with the temperature of cement paste versus time. Moreover, the calorimetric measurement was performed and the composition of the hydrated pastes was examined by thermal analysis. The results were showing that the temperature at which the hydration occurs determines the duration of the induction period, while w/c ratio equal 0.35 or 0.5 has no effect on the rate of this process. Furthermore, the heat of hydration is increasing the temperature of cement paste, which can cause the conversion of metastable calcium aluminate hydrates to C3AH6 phase.

5

Zastosowanie metody konduktometrycznej do rozpoznania strefy uskoku brzezińskiego w zlikwidowanym obszarze górniczym Rozalia

Siwek S.

Przegląd Górniczy

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2014

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T. 70, nr 1

31--37

PL

Praca przedstawia wyniki eksperymentalnych badań geofizycznych mających na celu uściślenie rozpoznania strefy dyslokacji tektonicznej w przypowierzchniowej warstwie podłoża w północnej części Górnośląskiego Zagłębia Węglowego. Do zobrazowania struktury górotworu zastosowano metodę konduktometryczną (GCM) w postaci wielopoziomowego profilowania przy zmiennym ustawieniu dipola anten. Badania przeprowadzono na poligonie testowym w Brzezinach Śląskich. Praca zawiera teoretyczny opis metody badawczej oraz analizę wyników pomiarów na poligonie.

EN

This paper presents the results of geophysical surveying aimed at the identification of the fault zone structure in the northern part of Upper Silesia. In order to visualize the fault plane the conductivity method (GCM) in multilayer profile mode with change of dipole orientation was used. The measurements were conducted on a test site in Brzeziny Slaskie. The paper describes theoretical principles of GCM method and the measurement’s results.

6

Lokalizacja stref uskokowych metodą konduktometryczną na terenie GZW

Siwek S.

Przegląd Górniczy

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2014

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T. 70, nr 7

61--68

PL

Metoda konduktometryczna (GCM) w postaci wielopoziomowego profilowania przy zmiennym ustawieniu dipola anten jest często wykorzystywaną metodą geofizyczną w lokalizacji stref dyslokacji tektonicznych. W artykule przedstawiono wyniki badań przeprowadzonych w warunkach przeobrażonego działalnością człowieka górotworu na terenach północnej części Górnośląskiego Zagłębia Węglowego. Miały one na celu rozpoznanie charakterystyki wybranych stref dyslokacji tektonicznych w przypowierzchniowej warstwie podłoża. Praca zawiera opis przeprowadzonych badań oraz analizę uzyskanych wyników w odniesieniu do danych geologiczno-górniczych.

EN

The ground conductivity method (GCM) in multilevel profile mode with changeable dipole mode is often used in the location of fault zones and examination of their structure. This paper presents the results of measurements carried out in test sites where natural geological conditions are transformed by exploitation (northern part of the Upper Silesia Coal Basin). The aim of the test measurements was to assess the possibilities of the method to identify such elements of fault zone structure as main fault plane and fault zone borders. This result was obtained only in one out of five cases tested.

7

Modyfikacja metody skalowania konduktometru

Dziczkowski L., Buchacz A.

Eksploatacja i Niezawodność

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2011

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nr 4

35-40

EN

The paper presents an innovative and improved method for doubled calibration of an eddy-current conductometer. Implementation of the proposed method makes it possible to achieve independence of the instrument indications on surface condition of the examined parts. The calibrating function is determined on-line when the measurements are in progress on the basis of parameters that are assigned to the contact probe coil and calculated with use of general mathematic equations. The calculated correction parameter can be considered as a measure of the surface roughness. Application of the modification as described in this paper can contribute to efficiency improvement of operational examinations for components made of non-ferrous materials during their lifetime.

PL

Zaproponowano oryginalną, ulepszoną metodę podwójnego skalowania konduktometru wiroprądowego. Realizując tę metodę można uzyskać niezależność wskazań przyrządu od stanu powierzchni badanych elementów. Funkcja skalująca konduktometr jest wyznaczana dynamicznie w czasie trwania pomiaru na podstawie parametrów przypisanych eksperymentalnie sondzie-cewce stykowej oraz uniwersalnych równań matematycznych. Obliczona poprawka może być traktowana jako miara chropowatości powierzchni. Stosując opisaną modyfikację można znacznie usprawnić badania eksploatacyjne elementów wykonanych z metali nieżelaznych.

8

Badanie elementów chropowatych metodą prądów wirowych

Dziczkowski L., Buchacz A.

Zeszyty Naukowe / Wyższa Szkoła Oficerska Wojsk Lądowych im. gen. T. Kościuszki

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2010

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Nr 4

84-99

PL

Jeśli istnieje zależność między niektórymi parametrami materiałów a ich przewodnością elektryczną, to można, w sposób nieniszczący metodą prądów wirowych, mierzyć konduktywność materiału i wnioskować o szukanych własnościach materiału, ciągłości jego struktury czy niektórych wymiarach geometrycznych. Poważną wadą metod wiroprądowych jest wyraźny wpływ stanu powierzchni na wynik testu. Zaproponowano oryginalną metodę kompensacji chropowatości powierzchni badanych elementów na wynik pomiaru konduktywności. Prezentowaną metodę oparto na podwójnym procesie skalowania zestawu konduktometr – sonda pomiarowa. Porównano skuteczność proponowanej metody z metodą powszechnie stosowaną.

EN

As the relationship between some important parameters of materials and their electric conductivity really exists, it makes it possible to use the eddy current method to measure conductivity of material in a non-destructive manner and then infer about the desired properties of materials, their continuous or non-continuous structure or some geometrical parameters. However, the substantial impact of surface condition demonstrated by examined materials onto test results is a significant drawback of the eddy current method. This is why, a new and innovative method for compensation of material surface roughness onto results of conductance measurements is proposed. The presented method is based on the double calibration process applied to the measuring kit of the conductometer and the measuring probe.

9

Zastosowanie pomiarów konduktometrycznych do śledzenia postępu reakcji w syntezie żywic fenolowo-formaldehydowych z udziałem zasadowych katalizatorów

Szemień M., Kałędkowski B., Skórka T., Napiórkowski S.

Przemysł Chemiczny

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2010

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T. 89, nr 1

45-49

10

Hindrances associated with examination of two-layer structures with use of the eddy current method

Dziczkowski L., Dziczkowska M.

Archives of Materials Science and Engineering

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2009

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Vol. 35, nr 1

39-46

EN

Purpose: Determination and description of essential phenomena that occur during examination of two-layer structures with use of the eddy-current method. Development of guidelines to establish procedures that make it possible to find out optimum frequencies of eddy currents, for which measurements of the outer film covering the examined structure exhibit best performance. Estimation of errors that occur when measurements of both geometrical and electrical parameters of the upper film within the two-layer structures are carried out simultaneously. Design/methodology/approach: During the design and scalling of the devices based on phenomenon of eddy currents implying changes of contact coil impedance components, significant influence of the electromagnetic field frequency on measurement results was observed. Additionally, some other phenomena can be observed which causes invalid interpretation of devices indications. Basing on a mathematical model of a contact coil located above a conductive non-ferromagnetic two-layer plate, the sensitivities to the measured parameters are determined. The developed mathematical model serves and the basis to calculate theoretical values of errors when all parameters of the outer film on the examined structure are measured simultaneously. Findings: Depending on specific applications, recommendations enabling proper choice of the electromagnetic field frequency are formulated. Practical implications: Describred phenomena and calculations are useful for the designers of the devices utilising the phenomenon of eddy currents, and also for the users of flaw detectors and conductometers. Remarks included in this paper can be useful for proper interpretation of the observed results and phenomena. Originality/value: Determination of impact coefficients that define how parameters of the two-layer structure are vulnerable to impedance components of the measuring contact coil.

11

Selection of the frequency of eddy currents in non-destructive testing of non-ferromagnetic plates

Dziczkowski L.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

|

Vol. 27, nr 1

43-46

EN

Purpose: To determine the optimal frequency of the electromagnetic field exciting eddy currents during the search for surface defects in non-ferromagnetic materials or at the time of conductivity measurements by means of eddy currents methods. Design/methodology/approach: On the grounds of a mathematical model of a contact coil located above a conductive non-ferromagnetic plate, the sensitivities to the measured parameters were designated. Furthermore, a new definition of eddy currents penetration depth was proposed. Findings: Recommendations facilitating proper selection of the electromagnetic field frequency were formulated, depending on specific applications. Practical implications: The discussed phenomena and calculations are useful not only to constructors of the devices utilising the phenomenon of eddy currents, but also to users of flaw detectors and conductometers. Originality/value: A modified definition of the actual penetration depth of eddy currents is proposed in the paper, which differs from the classical approach based on the 1/e level. The new definition may be very convenient and useful for operators utilising eddy current devices. The described sensitivity model facilitates setting up the devices for a specific task involved in a given process technology.

12

Conductometric determination of some important carboxylic acid derivatives and hydrochlorides in pharmaceutical formulations

Elazazy M. S., El-Mammli M. Y., Shalaby A., Ayad M. M.

Chemia Analityczna

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2008

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Vol. 53, No. 5

725-736

EN

A simplc and sensilivc clcclroanalylical mcthod for dctcrmination of four compounds of pharmaceutical interest: flunarizine hydrochloride (F-HC1), ramipril (RAM), terbinafine hydrochloride (T-HC1), and tranexamic acid (TRĄ) has been developed. The method was based on the titration of these compounds either with sodium hydroxide or tetrabutylammo-nium hydroxide (TBA). Alternatively. silvernitrate was used for titration of flunarizine and terbinafine hydrochlorides. End point was detected conductometrically. The method allowed for determination of the studied drugs in the rangę 0.5-30 mg. Mean percentage recoyeries ranged from (98.96 š 1.034) to (100.83 š 0.528). The proposed method was successfully applied to the determination of the studied compounds in dosage forms. 'ITie results were in good agreement with those obtained applying official or reference methods. The proposed method could be also applied to the simultaneous analysis of a mixture of ramipril and hydrochlorothiazide (HCT) in tablet dosage forms.

PL

Opracowano prostą i czułą metodę elektrochemicznego oznaczania czterech substancji farmaceutycznych: chlorowodorku flunaryzyny (F-HC1), ramiprylu (RAM), chlorowodorku terbinafiny (T-HC1) i kwasu traneksamowego (TRĄ). Metoda jest oparta na miareczkowaniu badanych związków wodorotlenkiem sodu lub wodorotlenkiem tetrabutyloamoniowym (TBA). Alternatywnie, do miareczkowania chlorowodorków flunaryzyny i terbinafiny stosowano azotan srebra. Koniec miareczkowania wyznaczano konduktometrycznie. Opracowana metoda pozwala na oznaczanie badanych leków w zakresie 0,5-30 mg. Średni odzysk procentowy wynosił od 98,96 š 1,034 do 100,83 š 0,528. Metodę zastosowano z powodzeniem do oznaczania badanych związków w formach farmaceutycznych. Otrzymane wyniki były w zgodności z wynikami otrzymanymi metodami referencyjnymi. Proponowana metoda może być również użyta do równoczesnego oznaczania ramiprylu i hydrochlorotiazydu w tabletkach.

13

Effect of eddy current frequency on measuring properties of devices used in non-destructive measurements of non-ferromagnetic metal plates

Dziczkowski L.

Archives of Materials Science and Engineering

|

2008

|

Vol. 32, nr 2

77-84

EN

Purpose: To determine optimal frequency of the electromagnetic field that raises eddy currents during the search for surface defects in non-ferromagnetic materials or conductivity measurements by means of eddy currents methods. The frequency choice takes into consideration sensitivity of measuring device, depth of the eddy currents penetration and elimination of undesirable phenomena that affects result of the exploration. Design/methodology/approach: During the design and scalling of the devices based on phenomenon of eddy currents implying changes of contact coil impedance components, significant influence of the electromagnetic field frequency on measurement results was observed. Additionally, some other phenomena can be observed which causes invalid interpretation of devices indications. Basing on a mathematical model of a contact coil located above a conductive non-ferromagnetic plate, the sensitivities to the measured parameters are determined. Furthermore, a novel definition of the eddy currents penetration depth is proposed. Findings: Depending on specific applications, recommendations enabling proper choice of the electromagnetic field frequency are formulated. Practical implications: Describred phenomena and calculations are useful for the designers of the devices utilising the phenomenon of eddy currents, and also for the users of flaw detectors and conductometers. Remarks included in this paper can be useful for proper interpretation of the observed results and phenomena. Originality/value: A modified definition of the actual penetration depth of eddy currents proposed in the paper differs from the classical approach based on the 1/e level. This definition may be especially convenient and useful for operators utilising eddy current devices. Described sensitivity model facilitates setting up the devices for a specific task involved in a different technological process.

14

Synthesis of New Thia-Derivative Salens, Their Complexes with Copper(II) and Analytical Application for Potentiometric Sensors

Saghatforoush L. A., Ershad S., Karim-nezhad G., Aminkhani A., Kabiri R.

Polish Journal of Chemistry

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2007

|

Vol. 81, nr 12

2069-2069

EN

Three new salen derivative ligands (L1, L2 and L3), containing mixed-ligand donor sets of NSNO, have been synthesized. The thermodynamics of complexation reaction between new synthesized salens and copper(II) ion in acetonitrile solution was studied by conductometric method. Formation constants of the resulting 1:1 complex was determined from the conductance-moleratio data. The results have shown that the new salens, as a neutral chelating agent formed selective and stable complex with Cu(II) ion. Thus, the L1 new salen compound was used as neutral ion carrier in the construction of a Cu2+-PVC membrane electrode. The influence of some exper i mental parameters such as membrane composition, nature and amount of plasticizer, additive and concentration of internal solution on the potential response of the Cu2+-sensor were investigated. The electrode exhibits a Nernstian response for Cu2+-over wide concentration range (5.0×10-6-1.0×10-1 M) with a slope 29.7š0.5 mV/decade and detection limit 1.0×10-6 M. It could be used in a pH range of 4.0-8.0. The electroe shows excellent discriminating ability to wards Cu2+ ion with regard to several alkaliand alkaline earth metal ions. It has a fast response time of about 20 s. The proposed sensor as an indicator electrode was used success fully in the potentiometric titra tion of Cu2+-ions with EDTA.

15

Discussion on the Complexing Ability of Macrocyclic Ligand, 12-Crown-4 with Li+ Cation in Some Binary Mixed Non-aqueous Solvents

Rounaghi G., Sanavi R.

Polish Journal of Chemistry

|

2006

|

Vol. 80, nr 5

719-727

EN

The complexation reaction of Li+ cation with 12-crown-4 (12C4) was studied in acetonitrile (AN)-methanol (MeOH), nitromethane (NM)-dimethylformamide (DMF) and propylencarbonate (PC)-dimethylformamide (DMF) binary mixtures and in neat tetrahydrofuran (THF) at different temperatures using the conductometric method. The conductance data show that in all solvent systems, the stoichiometry of the complex formed between 12-crown-4 and Li+ cation is 1:1. The stability of (12C4-Li)+ complex is sensitive to the solvent composition. The stability order of the complex in pure non-aqueous solvents was found to be: AN > MeOH > PC > THF > DMF. The values of thermodynamic parameters (deltaH deltaS c 0 c 0 , ) for formation of (12C4-Li)+ complex were obtained from temperature dependence of the stability constants and the results show that the thermodynamics of complexation reaction is affected by the nature and composition of the mixed solvents. A non-linear behaviour is observed between the thermodynamic parameters and the composition of the mixed solvents.

16

Study of Complex Formation of n-Alkylammonium Cations by Dibenzo-18-crown-6, Dibenzo-21-crown-7, and Dibenzo-24-crown-8 in Acetonitrile, Nitromethane and Nitrobenzene Solvents and Their Binary Mixtures Using Conductometric Method

Sadeghi S., Valavi

Polish Journal of Chemistry

|

2003

|

Vol. 77 / nr 9

1175-1184

EN

The complex formation of ammonium and four n-alkylammonium perchlorate salts with dibenzo-18-crown-6 (DB18C6), dibenzo-21-crown-7 (DB21C7) and dibenzo-24-crown-8 (DB24C8) was studied by conductometry in acetonitrile (AN), nitrobenzene (NB) and nitromethane (NM) solvents at different temperatures and their binary mixtures at 25°C. The stability constants of the resulting 1:1 complexes were determined and found to decrease in the order: DB21C7 > DB18C6 > DB24C8. Number of hydrogen atoms on the ammonium group available for bonding to the crown ethers was the most important factor in determining complex stability constant.The influence of other factors such as the size of the macrocyclic cavity, steric effect of the alkyl group attached to the + NH3 group, and the Gutmann donicity of the solvents on stability of the complexes were studied. In all cases, the stability constants of the resulted complexes in solvents used varied in the order: NB > NM> AN. Standard enthalpies and entropies of the complex formation were obtained from the temperature dependence of the stability constants. Obtained thermodynamic parameters were sensitive to the type of solvent. The enthalpy - entropy compensation effect was investigated in general complexation of cations with crown ethers.

17

Thermodynamics of Substituted Pyrazolone : VI. Potentiometric and Conductometric Studies of Complexes of Some Transition Metals with 4-(4-Acetophenyl)hydrazono-3-methyl-1-phenyl-2-pyrazolin-5-one

El-Bindary A., El-Sonbati A., Kera H.

Polish Journal of Chemistry

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2000

|

Vol. 74, nr 2

239-244

EN

The dissociation constant of 4-(4-acetophenyl)hydrazono-3-methyl-1-phenyl-2-pyrazolin-5-one (AHMPP) has been determined potentiometrically in 0.1 M KCl and 50% (v/v) ethanol-water mixture. Also, the stepwise stability constants of the formed complexes of Mn2+, Co2+, Ni2+, Cu2+, Zn2+, La3+, Ce3+, UO2+2 and Th4+ with AHMPP have been determined. The stability of the formed complexes follow the sequence: Th4+ UO2+2 Ce3+ La3+ Mn2+ Co2+ Ni2+ Cu2+ Zn2+ The thermodynamic parameters (deltaG, delta H and deltaS) for AHPP and its complexes were evaluated and discussed. The dissociation process is nonspontaneous, endothermic and entropically unfavourable. The formation of the metal complexes has been found to be spontaneous, exothermic or endothermic (depends on the metal) and entropically favourable. The stoichiometries of these complexes were determined conductometrically indicating the formation of 1:1 and 1:2 (etal:ligand) complexes.

18

Synthesis of a New triazine Derived Macrocycle and a Thermodynamic Study of Its Complexes with Some Transition and heavy Metal Ions in Acetonitrile Solution

Pourghobadi Z., Seyyed F., Daghighi-Asli M.

Polish Journal of Chemistry

|

2000

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Vol. 74, nr 6

837-846

EN

A synthetic procedure has been developed for the preparation of a new triazine derived macrocycle (13,29-diphenyl-4,7,20,23-tetraoxa-1,10,12,14,16,17,26,28,30,32-decaza-[10,10](2,6)triazinophane). The formation of some transition and heavy etal complexes with the macrocycle was investigated in acetonitrile solution conductometrically at different temperatures. The formation constants of the resulting 1:1 complexes were determined from the molar conductance-mole ratio data and found to vary in the sequence Hg2+ Pb2+ Cd2+ - Ag+ Cu2+ Tl+ Co2+ Ni2+ Zn2+. The enthalpy and entropy of complexation reactions were determined fro the temperature dependence of the formation constants. In all cases, the complexes were found to be enthalpy stabilized but entropy destabilized.

19

Coil-to-helix transition of anionic polysaccharides: comparisond of voltammetric and conductometric results for kappa-carrageenan

Ciszkowska M., Guillaume M. D., Kotlyar I.

Chemia Analityczna

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2000

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Vol. 45, No. 2

167-174

EN

Two electroanalytical techniques, steady-state voltammetry and conductance measurements were utilized to study the conformational coil to double helix transition of an ionic polysaccharide /cappa-carrageenan, K-car, in solutions of low ionic strengths as effected by temperature and concentration of the polyion. The interactions betweep counterions, Na+, or electroactive probe ions, Tl+, and polyanions during such transition were quantified by the ratio of the diffusion coefficient of Na+ or Tl+ ions in the polyelectrolyte solution (K-car sodium salt) to that in the solution without polyelectrolyte (NaCl or NaClO4). The results for native counterions, Na+, from conductance measurements were very close to those obtained by voltammetry of Tl+ probe ions. The conformational transition was a reversible coil-to-double helix process resulting from temperature decrease. This process did not depend on the concentration of K-car for the concentration range from 10 to 40 mmol 1-1. The charge spacing in K-car conformers was determined by employing Manning's theory for polyelectrolytes. The average charge spacing calculated from the conductivity and voltammetric results was 0.39 nm and 0.90 nm for the double helix and the coil form of K-car, respectively.

PL

Badano przejście konformacyjne jonowego polisacharydu (kappa-carrageenan, K-car) w funkcji temperatury, mocy jonowej i polijonu używając stacjonarnej woltamperometrii i konduktometrii. Oddziaływanie między polijonem i kontrjonami Na+ oraz sondującymi jonami Ti+ można było określić ilościowo ze zmian współczynników dyfuzji tych jonów. Przejście ze struktury spirali do podwójnej helisy było odwracalne i nie zależało od stężenia K-car w zakresie 10-40 mmol T1. Odległość między ładunkami obliczono używając teorii Manning'a. Otrzymano wielkości 0.39 i 0.90 nm odpowiednio dla form K-car - podwójnej helisy i spirali.

20

The influence of the ionic strengths of polyacrylamide and xanthan gum

Gampert B., Wilkes C.

Applied Mechanics and Engineering

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1999

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Vol. 4, no spec.

283-288

EN

Polyelectrolytes are macromolecules which carry a large quantity of ionizable groups along their chains. By dissolving them in suitable solvents, for example water, these groups dissociate in highly charged macroions and an equivalent quantity of low molecular counter ions. Through the bonding of polymer and electrolyte properties this class of materials obtains its peculiar characteristic behaviour. For the characterization of phenomenological effects of polyelectrolyte solutions, viscometric and conductometric methods will be applied for this paper. There, the viscosity measurements will be carried out using highly dilute polymer concentrations where the intermolecular interactions play a role. The experiments undertaken here were carried out using a commercial, anionic polyacrylamide and xanthan gum with different hydrolysis factors and molecular weights. The reduced viscosity increases strongly with the decrease of polymer concentration for low cp values. It reaches a maximum and then decreases again.