Wyniki wyszukiwania - BazTech

1

Modelowanie matematyczne i badania fizykochemiczne równowag kwasowo-zasadowych w układach binarnych rozpuszczalników

Michałowski T., Pilarski B., Dobkowska A., Młodzianowski J.

Wiadomości Chemiczne

|

2010

|

[Z] 64, 1-2

123-154

EN

Conductometric titration (CT) is used as a complementary, non-specific technique against potentiometric (pH) titration (PT). The CT + PT procedure is applied to binary-solvent systems: HmL + Z/A + B (or HmL + Z/W + B) formed of a weak acid HmL and a pH-modifying agent Z (e.g. NaOH, NH3 or HCl), and totally miscible organic solvents A and B (or W = H2O and B) chosen as co-solvents, where acid-base equilibria are considered. The solvent composition in such systems is expressed by the mole fraction x of B. Concentrations of solutes: HmL and Z are the same in the solution titrated (titrand, D) and in titrant (T) and changes in pH value resulted only from differences in acid-base properties of solvents applied in D and T. On the basis of results obtained from PT and CT, the functional relationships related to the solutions of weak acids HmL (m = 1, 2, ...) were formulated, namely: (1) pKi = pKi(x) for acidity parameters; (2) Lp = Lp(x) for molar conductivities, related to the species formed by di- and triprotic acids. For this purpose, the Kohlrausch law on the independence of migrating ions has been applied. The pKi = pKi(x) relationships were formulated for diprotic and triprotic acids on the basis of enderson.Hasselbalch functions and modeled with use of polynomial functions. The pKi(1) and Lp(1) values were obtained by extrapolation. The approach suggested is the essential novelty in contemporary literature related to the subject in question. This way, the paper provides a new methodology, a new dimension (x-scale) to the problems known hitherto. In the experimental part, the pK1 = pK1(x) relationships were formulated for results of mutual pH titrations: HmL/B . HmL/W or HmL/B . HmL/A, obtained for the systems not involving Z. The systems were modeled with the use of Redlich.Kister (R.K) and orthogonal (normal, shifted) Legendre polynomials. Asymmetric functions by Myers.Scott (M.S) and by Michałowski were also suggested for this purpose. It was stated that all approximating functions fit the experimental data very well. The asymmetric functions are applicable for modeling of more bended relationships pK1 = pK1(x), particularly when referred to the limiting x-values in the interval < 0, 1 >. A software that enables to formulate the relationships pKi = pKi(x) according to different approximating functions after introducing the experimental data {(Vj, pHj) | j = 1, ..., N} obtained from PT, was also prepared, together with statistical evaluation of pKi(0) and pKi(1) values, obtained by extrapolation. The results thus obtained are presented in tables and figures. Some criteria of validity of the results obtained according to PT for pK1(0) and pK1(1) are also presented. The first criterion testifying about reversibility of indications of the measuring system is a position of the point of intersection of the plots obtained in the mutual titrations. The second criterion stems from comparison of results obtained from three pH titrations: (1) HmL/B Ť HmL/W, (2) HmL/B Ť HmL/A and (3) HmL/A Ť HmL/W. The convergence of the related plots at x = 0 and x = 1, where x = xB in (1) and (2) and x = xA in (3) testifies on account of the calibration procedure applied for glass electrode.

2

Conductometric titration studying on hollow microspheres preparation

Cheng J., Sun J., Lin H., Wei D.

Polimery

|

2006

|

T. 51, nr 9

643-647

EN

Hollow microspheres were prepared via osmotic swelling. In order to study preparation process, a series of latex particles with different core/shell weight ratio were prepared by seeded emulsion polymerization. The content of surface carboxyl groups in the latex particles obtained from conductometric titration curve was used to determine the threshold core/shell weight ratio for hollow microspheres. Additionally, the rheology and opacity were studied. The results showed that the optimal core/shell weight ratio obtained from the conductometric titration curve was in agreement with the ratio acquired from transmission electron microscopy (TEM) analysis, the rheology and opacity studies.

PL

Puste mikrokulki były otrzymane za pomocą pęcznienia osmotycznego. Metodą polimeryzacji emulsyjnej z zastosowaniem różnych stosunków wagowych składników typu rdzeń/powłoka otrzymano dwie serie cząstek różniących się ilością użytego lateksu (tabele 1-3). W celu określenia granicznej wartości stosunku wagowego rdzeń/powłoka zapewniającego otrzymanie pustych mikrokulek zaproponowano nową metodę miareczkowania konduktometrycznego. Porównawczo zastosowano typową metodę elektronowej mikroskopii transmisyjnej (TEM) uzyskując podobne wyniki. Dodatkowo zbadano lepkość (tabela 5) i współczynnik nieprzezroczystości (tabela 6) uzyskanych próbek.

3

Conductometric determination of phenothiazine derivatives by precipitation titration

Kowalczyk-Marzec A., Kurzawa M., Szydłowska-Czerniak A., Szłyk E.

Chemia Analityczna

|

2002

|

Vol. 47, No. 4

613-618

EN

Results of the conductometric titration of phenothiazine derivatives: trifluoperazine dihydro-chloride (TPE), triflupromazine hydrochloride (TFP) and prochlorperazine dimaleate (PCP) in aqueous and ethanol solutions, with ammonium molybdate(VI), sodium vanadate(V) and sodium arsenate(III) as the titrants, are reported. The method was found to be highly accurate, precise and having relative standard deviation of less then 1% (in 0.5 x 10(-3) to 1.0 x 10(-3) mol L(-1) analyte concentration range). The conductometric titration was applied for the determination of the studied compounds in the presence of NaCl and revealed a good accuracy.

PL

Przedstawiono wyniki miareczkowania konduktometrycznego pochodnych fenotiazyny: dichlorowodorku trifluoperazyny (TPE), chlorowodorku triflupromazyny (TFP) i dimalei-nianu proch lorperazyny (PCP) w wodnym i etanolowym roztworze z molibdenianem(VI) amonu, wanadanem(V) sodu i arsenianem(IIl) sodu jako titrantami. Metoda okazała się bardzo dokładna, precyzyjna, z odchyleniem standardowym mniejszym niż l % (w zakresie stężeń od (in 0,5 x 10(-3) do 1.0 x 10(-3) mol L(-1). W celu oznaczenia badanej substancji zastosowano miareczkowanie konduktometryczne w obecności NaCl, a uzyskane wyniki były zgodne z wynikami dla czystego leku.