Effects of QMix and ethylenediaminetetraacetic acid on decalcification and erosion of root canal dentin.

The aim of this study was to evaluate the effect of initial NaOCl on the decalcification and erosion ability of EDTA and QMix. Sixty-maxillary-incisors were bisected longitudinally and the tooth-halves were used. The experiment was conducted in two-sets. In set-I, 80-tooth halves were treated in the presence or absence of initial NaOCl and EDTA. In set-II, 40-tooth halves were immersed in NaOCl and QMix. After each treatment, calcium-ion release was determined with flame photometry. The erosion was imaged using SEM. Initial NaOCl led to concentration- and time-dependent increase in calcium removal effect of 17% EDTA (p < .05). The rate of calcium removal and root canal wall erosion was considerably more severe with the use of 5% NaOCl for 3 min (p < .05). QMix as a final solution showed less decalcification and erosion than 17% EDTA when used 5% NaOCl as an initial irrigant (p < .05). Optimizing the concentration and application time of NaOCl can decrease the decalcification effect of chelating agents.

A new, fast and sensitive method for the determination of trace amounts of nitrite using differential pulse polarography.

Nitrite salts of sodium or potassium are being used for the protection of meat products. They provide color and taste of meat and they protect against clostridia. On the other hand, nitrite ions can interact with amines to form nitrosamines which are known as carcinogenic substances. They may also react with hemoglobin and reduce its oxygen carrying capacity. Thus, its concentration in food-stuff has to be controlled carefully by highly sensitive methods. A new DP polarographic method is established for the determination of nitrite. Nitrite cannot be determined directly with any analytical methods. Long and tedious procedures are necessary for many of them. In this polarographic method arsenite, As(III), ion is used for the reduction of nitrite. The nitrite is determined from the As(III) quantity left over after the reaction with nitrite. The peak of arsenite has been used since it is sharp and responds well for the standard addition of arsenite. The optimum conditions for the quantitative reaction between nitrite and arsenite have been studied. It was found that the pH for the reaction medium has to be 5-7, since nitrite is decomposed at lower pH values. The reaction medium has to be stirred for about 5 min with nitrogen gas in order to expel the NO gas formed and thus to shift the equilibrium to products side. The limit of detection, LOD, was found to be as 2 × 10(-7) M. No interference was observed from most common ions.

Preparation and properties of a new solid state arsenate As(V) ion selective electrode and its application.

In this study a new solid-state ion selective electrode which is easy to prepare and sensitive to arsenate ion concentration is prepared. The solid salts used in the electrode composition were Cu2S, Ag3AsO4 and Ag2S. The principal component of the electrode was Ag3AsO4. The measurements were made in constant ionic strength using 0.1M NaNO3 and at room temperature. The potentiometric response of electrodes prepared in various compositions was investigated against arsenate ion concentration. The highest slope was obtained with 40% Ag3AsO4, 30% Cu2S and 30% Ag2S. This electrode showed linear response for arsenate ion in the 10(-5)-10(-1) M concentration range. An analytically useful potential change occurred, from 1×10(-6) to 1×10(-1) M arsenate. The slope of the linear portion was about 19±2 mV/10-fold change in arsenate concentration. The lifetime of the electrode was more than two years, when used at least 4-5 times a day, and the response time was about 20-30s depending on the concentration changes. The interference of most common ions and the effect of pH (6-10) have been investigated. This electrode has been used for the determination of arsenate ion in beer sample.

Preparation and properties of a new solid state borate ion selective electrode and its application.

A new borate ion selective electrode using solid salts of Ag(3)BO(3), Ag(2)S and Cu(2)S has been developed. Detailed information is provided concerning the composition, working pH and conditioning of the electrode. An analytically useful potential change occurred from 1×10(-6) to 1×10(-1) M borate ion. The slope of the linear portion was 31±2 mV/10-fold changes in borate concentration. The measurements were made at constant ionic strength (0.1 M NaNO(3)) and at room temperature. The effect of Cl(-), Br(-), NO(3)(-), SO(=)(4), H(2)PO(4)(-) anions and K(+), Na(+), Cu(2+), Ag(+), Ca(2+) cations on borate response is evaluated and it was found that only Ag(+) had a small interference effect. The lifetime of the electrode was more than two years, when used at least 4-5 times a day, and the response time was about 20-30s. Borate content in waste water of borax factory, tap water of a town situated near to the borax factory and city tap water far from these mines were also determined. The validation was made with differential pulse polarography for the same water sample, and high consistency was obtained.

Preparation of a new solid state fluoride ion selective electrode and application.

A new solid state fluoride ion selective electrode composed of 70% Ag(2)S, 10% Cu(2)S and 20% CaF(2) has been developed. An analytically useful potential change occurred, from 1x10(-6) to 1x10(-1)M fluoride ion. The slope of the linear portion (1x10(-1)-1x10(-5)M) was about 26+/-2mV/10-fold concentration changes in fluoride. It was found that pH change between 1 and 8 had no effect on the potential of the electrode. There was no interference of most common cations such as K(+,) Na(+), Ca(2+) and Mg(2+) and anions such as Cl(-), NO(3)(-), SO(4)(2-) and PO(4)(3-). The lifetime of the electrode was more than 2 years, when used at least 4-5 times a day, and the response time was about 60s. The measurements were made at constant ionic strength (0.1M NaNO(3)) and at room temperature. This electrode has been used for the determination of fluoride ion in Ankara city tap water and in bottled spring water using standard addition method. The validation of the electrode has been made with a commercial fluoride ion selective electrode (Orion) and high consistency was obtained.

Direct and indirect methods for the determination of vitamin K3 using differential pulse polarography and application to pharmaceuticals.

Two methods for the determination of vitamin K(3) have been developed. Vitamin K(3) in its oxidized form is determined by direct and indirect methods. Its standard solution was prepared by the indirect method using Ti(III) as reducing agent. For this purpose vitamin K(3) (menadion) in a clinical injection solution, which is in its hydroquinone form in the presence of sulfite, is oxidized with oxygen. In 0.2 M HAc and 0.02 M HCl electrolyte vitamin K(3) and Ti(IV) have reduction peaks at -0.58 V at -0.82 V respectively. The reaction between Ti(III) and vitamin takes place quantitatively in a medium of 0.2 M HAc and 0.002 M HCl. After the reduction, the reaction product Ti(IV) is followed from its polarographic peak at about -0.82 V. The most important result in this work is that, with this method vitamin K(3) can be standardized and after standardization this solution can be used for the direct determination in routine analysis with a very simple and fast method, using only the peak at -0.71 V in 0.2 M HAc medium. Both direct and indirect methods have been used for the determination of Vitamin K(3) in a clinical injection solution. The limit of quantification (LOQ) was 1.5x10(-6) M and in both methods the detection limit found was 7x10(-7) M.

Determination of trace sulfite by direct and indirect methods using differential pulse polarography.

Sulfite determination plays an important role since it is used in some food stuff as protecting agent. The objective of this study was to develop a new and simple method for the determination of sulfite so that it can be used in routine food analysis. A differential pulse polarographic (DPP) method has been used for this purpose since the results obtained with this method are very reproducible and the instrument used is not expensive. Various acids and pH values have been studied such as 4 M, 1.0 M, 0.1 M HCl and HClO4, and HAc-NaAc electrolyte. The best medium was pH 3-5 acetate medium, where the reduction peak of sulfite at about -0.6 V was used. At lower pH values sulfite was escaping as SO2 while nitrogen gas was passing. At higher pH values, on the other hand, the peak was too small for the accurate determination. Interference of most common elements such as Fe, Cu, Pb and Cd was investigated and it was found that only Cd had an overlapping peak. This interaction could be eliminated using EDTA. The detection limit found was 2x10(-6) M in acetate buffer. An indirect method was developed also where the reaction between selenite and sulfite has been used. In this method a known amount of selenite was added and the selenite after reaction has been determined. The detection limit (7x10(-7) M) was lower than direct method. The quantity of sulfite present in dried apricots was found between 1.5 and 1.7 g kg(-1) of dried fruit.

Nucleophilic attack by bromide ions as a first step of conversion of Se(VI) to Se(IV).

Numerous commonly used analytical methods allow only determination of a total amount of selenium in a given sample. Electroanalytical methods as well as those based on hydride generation or on formation of piazselenol allow only determination of Se(IV). To determine Se(VI) by these procedures, present alone or in mixtures with Se(IV), it is first necessary to convert Se(VI) to Se(IV). Such conversion is effective in the presence of excess of halides in acidic media or by photoreduction. In the often used conversion of Se(VI) in the presence of chlorides or less frequently of that of bromides, it has been assumed that the halide ion acts as a reducing agent. Kinetic studies of conversion of Se(VI) in acidic solutions containing an excess of bromide ions indicated that the rate determining first step of the reaction with Se(VI) is a nucleophilic substitution of the OH(2)(+) group in the protonated form of H(2)SeO(4) by bromide ions. For the overall reaction with rate -d[Se(VI)]/dt=k(1)[H(+)][Br(-)](1.15)[Se(IV)] the rate constant 1 x 10(-3)L(2)mol(-2)s(-1) was found. The following formation of Se(IV) from the bromo derivative is a fast reaction probably resulting in elimination of HBrO.

Preparation and application of a new glucose sensor based on iodide ion selective electrode.

An electrode for glucose has been prepared by using an iodide selective electrode with the glucose oxidase enzyme. The iodide selective electrode used was prepared from 10% TDMAI and PVC according our previous study. The enzyme was immobilized on the iodide electrode by holding it at pH 7 phosphate buffer for 10min at room temperature. The H(2)O(2) formed from the reaction of glucose was determined from the decrease of iodide concentration that was present in the reaction cell. The iodide concentration was followed from the change of potential of iodide selective electrode. The potential change was linear in the 4x10(-4) to 4x10(-3)M glucose concentration (75-650mg glucose/100ml blood) range. The slope of the linear portion was about 79mV per decade change in glucose concentration. Glucose contents of some blood samples were determined with the new electrode and consistency was obtained with a colorimetric method. The effects of pH, iodide concentration, the amount of enzyme immobilized and the operating temperature were studied. No interference of ascorbic acid, uric acid, iron(III) and Cu(II) was observed. Since the iodide electrode used was not an AgI-Ag(2)S electrode, there was no interference of common ions such as chloride present in biological fluids. The slope of the electrode did not change for about 65 days when used 3 times a day.

Interference between selenium and some trace elements during polarographic studies and its elimination.

When selenite was added into solutions of some ions such as copper, lead, cadmium, zinc, chromium and arsenic their DPP peak decreased. This kind of interference was observed in all acids and in wide range of pH values, causing at least 50% error when both ions (the ion present and selenite) were in similar quantities. It was found that this interference was not taking place at pH 8.5 in the presence of large amounts of selenite. A synthetic sample containing these elements in 10(-5)M in the presence of 50 times selenite has been analyzed at pH 8.5 without any interference. The detection limit in this medium was 3 x 10(-7)M for cadmium and lead, 1 x 10(-6)M for copper and zinc and it was 3 x 10(-7)M for selenite.

A new and direct method for the trace element determination in cauliflower by differential pulse polarography.

Using the DPP polarograms of wet digested cauliflower sample in acetate buffer at pH values of 2, 4 and 6, Fe, Zn, Mo, Se, Cr, Cd, Pb, Ti and Cu quantities were determined. The best separation and determination conditions for Zn, Se and Mo was pH 2; for Cr, Zn, Mo and As was pH 4; for Pb pH 6, for Ti, Cu and Fe was pH 6-7 EDTA, for Cd pH 2 EDTA and for lead pH 6, all in acetate buffer. The trace element ranges for cauliflowers from two different seasons were (first figure for winter, the second for summer) for Se 120-250mugg(-1), Fe 70-85mugg(-1), Cu 320-150mugg(-1), Ti 90-120mugg(-1), Cr 130-630mugg(-1), Zn 90-550mugg(-1), Mo 170-230mugg(-1), Cd 20mugg(-1) (in winter) and Pb 130-300mugg(-1) in dry sample. Cd was under the detection limit in summer. The length of digestion time had no effect on the recovery of copper, iron, molybdenum and zinc between 15 and 3h of digestion.