Amperometric Titration Method Research Articles

Nanocarbon Based Chemiresistive Detection of Monochloramine in Water

The use of chloramine as a disinfectant in water treatment plants is becoming popular due to its lower reactivity and higher stability than free chlorine.1–3 Chloramines are produced by the reaction of free chlorine (HOCl, OCl-) with nitrogen compounds to form monochloramine (NH2Cl), dichloramine (NHCl2) or nitrogen trichloride (NCl3), depending on pH and N/Cl ratio.4 Dichloramine and nitrogen trichloride tend to create odour and taste problems in drinking water. Thus, only monochloramine is preferred for disinfection. Typically, 0.5-2 mg/L of monochloramine is maintained in the water distribution system.5 Maintaining the concentration level of monochloramine is crucial to prevent pathogen growth in the drinking water. Currently, there is no direct method to measure chloramine. However, U.S. EPA-approved amperometric titration and colorimetric methods are available which can be used to measure total and free chlorine in aqueous media.2 An amperometric titration method (SM 4500-Cl D) is capable of distinguishing 3 common forms of chlorine: Cl2 / HOCl / OCl-, NH2Cl, and NHCl2. However, it fails at concentrations greater than 2 mg/L (as Cl2).2,3 Even though this method is not affected by common oxidizing agents, temperature changes, turbidity, and colour, it does require a greater degree of skill. Operationally simpler, N,N-diethyl-p-phenylenediamine (DPD) methods (ferrous and colorimetric) are used to measure free and total chlorine and then their subtraction gives the concentration of monochloramine, assuming no NHCl2 and NCl3 are present. DPD methods are subjected to interferences like copper, manganese (oxidized), iodide and chromate.6 Additionally, the DPD method is not suitable for continuous monitoring of monochloramine which is essential in water distribution plants to maintain the appropriate concentration of disinfectant.2,3,7 Here we demonstrate a chemiresistive sensor array for the continuous monitoring of chloramine in the water. Chemiresistive sensors are cheap, robust and use low power. These sensors detect an analyte through changes in the electronic properties of the transducing element. A nanocarbon network was airbrushed onto the frosted side of a microscope glass slide as the transducing element between two pencil trace contact patches. Copper tapes were placed on top of the pencil patches and then covered with a dielectric. 10 mV voltage was applied for the measurements, and the changes in resistance were measured as the analyte interacted with the transducing element. The surface of the nanocarbon network is functionalized with suitable dopant molecules by submerging the sensor in the molecule solution. This array of molecules will be able to capture the parameters to be able to classify the type of chloramine present in water. Fresh chloramine solution is prepared before each experiment by adding NH4Cl and NaOCl in Phosphate Buffered Saline (PBS). Sensor responses are recorded as positive current change with increasing concentrations of monochloramine. Here the hole density of the inherently p-doped substrate increases when exposed to monochloramine, and thereby resulting in increasing current. Sensors can be reset with ascorbic acid or water. Sensors were tested with 0.054 ppm to 1.437 ppm of monochloramine in pH 7.5 and 8.5. Functionalized sensor devices showed a considerably higher response than the unfunctionalized ones. The tap water sample was tested with the calibrated devices. We have therefore demonstrated a robust sensor array capable of continuously monitoring chloramine in aqueous media.

AMPEROMETRIC DETERMINATION OF CERIUM (III) USING 2,7-DINITROZO-1,8- DIHYDROXYNAPHTHALENE-3,6-DISULFONIC ACID SOLUTION

Cerium and its compounds are widely used in the production of electronic devices and semiconductors, which is why these substances will enter the environment more often in the future. There is a need for effective express methods that can determine the trace amounts of cerium and other rare earth elements with high accuracy to control and study the possible negative impact of cerium compounds on the ecosystems. The objective of this research paper was to elaborate on an express method capable of producing accurate and reliable results on the content of cerium in wastewaters in the presence of other rare earth elements. The elaboration of the express method was carried out based on the amperometric titration method studying the effect of various buffer solutions on cerium determination. Moreover, the effect of strontium, lutetium, iron, yttrium, samarium, niobium, holmium, praseodymium, gadolinium, and erbium ions on acquisition accuracy of the cerium (III) ions in samples of process water was studied. The research results presented a method for the amperometric determination of cerium (III) applying 2,7-dinitroso-1,8-dihydroxynaphthalene-3,6-disulfonic acid on a rotating platinum disk microelectrode. The extraction-amperometric method of analysis was proposed for the analysis of process water. The optimal concentrations of background electrolytes and buffer mixtures and the voltage values, were determined; the stability constant of the complex was calculated; the lower limit of the determined cerium content was defined. No interfering influence of foreign ions on the determination of cerium (III) ions was observed. The developed method for determining cerium (III) has a simpler hardware design than the previously described method of pulsed direct current glow discharge mass spectrometry but has a higher detection limit.

Automatic amperometric titration method for quantitative determination of zinc oxide in ointments

Automatic amperometric titration method for quantitative determination of zinc oxide in ointments

The state of thioldisulphide system of patients with chronic diseases of upper respiratory tract with concomitant coeliac disease

The article presents the results of the study of thioldisulphide system by amperometric titration method in the patients with chronic diseases of the upper respiratory tract with the concomitant coeliac disease. The study involved 48 patients with genetically confirmed diagnosis of celiac disease, aged 19 to 45 years. We observed a significant reduction of thioldisulphide index (the ratio of the concentration of SH-and-SS-groups of blood serum), which indicates the resistance tissue disorder and the intensification of free radical oxidation in these patients. The change of TDI may serve as a diagnostic criterion of the efficacy of the therapy.

Investigation of the interaction of resveratrol with free radical diphenylpicrylhydrazyl at different pHs by cyclic voltammetry: Correlation between antioxidant activity and association complex constant

The association reaction between resveratrol (RSV) and free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH·) at different pH values has been firstly investigated by cyclic voltammetry. The voltammetric experiments showed that the main reductive signal of DPPH· gradually decreased with the increasing concentration of RSV. The stoichiometry of RSV-DPPH· complex was determined to be 1: 1 by means of amperometric titration method. Also, the association constants for this molecular complex at pHs of 4, 7.4 and 10 were calculated as 2.55 × 104, 4.96 × 104 and 7.28 × 104 M−1, respectively. At the same time, the antioxidant activities of RSV at different pHs were determined from its anodic peak potentials on cyclic voltammograms (CVs). According to the correlation between antioxidant activity and association complex constant of RSV, the association constants determined by voltammetric DPPH· assay can be used as a measurement of the antioxidant capability of RSV.

A-64 FACTS法による現場での浴槽水残留塩素濃度測定方法の検証 : (その2)電流滴定法を基準にした試験室実験での評価

A-64 FACTS法による現場での浴槽水残留塩素濃度測定方法の検証 : (その2)電流滴定法を基準にした試験室実験での評価

Determination of submillimolar concentration of ferrate(VI) in alkaline solutions by amperometric titration

Abstract A new amperometric titration method was developed for quantitative determination of ferrate(VI) (FeVIO42−) in the 7.06×10−5−5.73×10−3 M concentration range. Chromium(III) hydroxide solution was used as the titrant. The diffusion current (Id) had a linear relationship with the concentration of ferrate(VI) and slopes were dependent on the concentration of NaOH. The amperometric titration could detect a lower concentration of ferrate(VI) than could potentiometric and colorimetric titrations. The method was applied successfully to determine concentrations of ferrate(VI), generated electrochemically, in strong alkaline solutions.

Application of bismuth-film electrode for cathodic electroanalytical determination of sulfadiazine

A bismuth-film electrode for use in cathodic electrochemical detection was employed in order to quantify sulfadiazine in pharmaceutical formulations. The bismuth film was deposited ex situ onto a glassy carbon substrate. Analysis of two sulfa drugs was carried out by differential-pulse voltammetry in 0.05 mol L −1 Britton–Robinson pH 4.5 solution. Sulfadiazine reduction was observed at −0.74 V vs. Ag/AgCl in one well-resolved irreversible reduction peak. The analytical curve with two slopes was obtained in the concentration range of 3.2–97.0 μmol L −1. The detection limit was 2.1 μmol L −1 for concentrations of 3.2–20.0 μmol L −1 ( r = 0.9949) and 12.2 μmol L −1 for concentrations between 20.0 and 97.0 μmol L −1 ( r = 0.9951). Recovery studies carried out with both sulfadiazine samples gave values from 93.6 to 109.3%. The accuracy of the results supplied by the bismuth-film electrode was compared to those obtained by the standard amperometric titration method. The relative error between them was lower than 2.0%.

Sulfadiazine determination in pharmaceuticals by electrochemical reduction on a glassy carbon electrode

Sulfadiazine was quantified in two samples of pharmaceutical preparations by square-wave voltammetry. The analytical signal response was obtained by electrochemical reduction instead of oxidation of the sulfa drug at a glassy carbon electrode. The determination was carried out in 0.04 mol L-1 Britton-Robinson pH 6.8 buffer solution. Sulfadiazine reduction was observed at -1.49 V vs. Ag/AgCl in one well-resolved irreversible peak. The analytical curve was obtained in the concentration range of 62.7 to 340 µmol L-1 (r = 0.9986) with a detection limit of 10.9 µmol L-1. For one sample analyzed, recovery values were in the range of 94.9 to 101.1%, while for the other sample they were within 96.0 to 104.6%, indicating no matrix interference effects on the analytical results for both sulfadiazine samples. The accuracy of the electroanalytical method was compared to the standard amperometric titration method.

Simultaneous determination of amylose content & unit chain distribution of amylopectins of cassava starches by fluorescent labeling/HPSEC

The fluorescent labeling of debranched starch/high-performance size-exclusion chromatography equipped with one column of Shodex OHpak SB-803HQ and two columns of SB-802.5HQ was proposed for simultaneous determination of amylose content and unit chain distribution of amylopectin of starch samples from four cassava varieties. Chromatograms obtained by refractive index (RI) response detection revealed that peaks of amylose and amylopectin fractions were completely separated, whereas only a peak of amylopectin was observed by fluorescent response detection. The amylose contents of cassava starch samples calculated from the RI response chromatograms were comparable to those determined by amperometric titration method and by overlaying the amylopectin profile on the profile of the starch isoamylolyzate. The values obtained for each starch sample were highly reproducible for duplicate analyses with standard deviations less than 0.6%. Distribution profiles of amylopectins from the starch isoamylolyzate were very similar to those obtained from fractionated amylopectins. Molar- and weight-based unit-chain fraction and ratio of A+B1/B2+B3 were close to those derived from profiles of fractionated amylopectins. Differences of mole fraction of A, B1 and B2+B3 chains and ratio of A+B1/B2+B3 determined from starch and fractionated amylopectin chromatograms of all four cassava starches were less than 2.7, 2.7, 0.15 and 0.12%, respectively.

ソテツ幹澱粉の二，三の性質について

Some chemical and physical properties of starch prepared from trunks of sotetsu (Cycas revoluta Thunb.) (sotetsu A) were compared with starches prepared from seeds of sotetsu (Sotetsu B) and ginkgo (Ginkgo biloba L.) seeds. The results obtained were as follows 1) The mean particle size of sotetsu A, sotetsu B and ginkgo starches were 13.2pm, 9.5 pm and 12.4 pm, respectively. 2) The susceptibility of sotetsu A starch granules to hog pancreatin was similar to that of sweet potato starch granules having relatively high susceptibility. By scanning electron microscopy (SEM), the appearance on the surface of sotetsu A starch granules attacked by pancreatin was quite similar to the case of normal maize starch granules, for which the enzymatic attack usually started with small pits on the surface of the granules and then the pits increased in number and in size during the subsequent enzyme attack. 3) The initiation temperature for gelatinization of sotetsu A starch, by photopastegraphy and differential scanning calorimetry (DSC) were 58.5 and 63. it, respectively. The enthalpy change, 4H, determined by DSC was 3.7 cal/g, which was relatively lower than that of the other two starches. The maximum viscosity and breakdown of sotetsu A, determined by Brabender's amylography (6%), were 460 BU and 30 BU, respectively. Breakdown was low like sotetsu B and ginkgo starches. 4) The amylose contents of sotetsu A starch, determined by amperometric titration and enzyme-chromatographic method, were 25.2, 23.2%, respectively. 5) Texture of 6% starch gels was determined by curdmeter and a Rheoner; sotetsu A formed gel having low hardness and breaking force and relatively high cohesiveness.

Comparison of three methods for measuring residual chlorine

Three EPA-approved residual chlorine detection methods were compared using standard solutions and water collected from the Savannah River which is used to cool reactors at the Savannah River Site (SRS) near Aiken, S.C. The testing was part of an experimental program to develop baseline data for the design of a proposed cooling tower for the K-reactor at the SRS. A series of total residual chlorine (TRC) measurements made simultaneously by three methods revealed that for the river water samples, the DPD method (Hach DR-100 kit) and the amperometric titration method produced statistically similar results while an ion-selective electrode method, standardized according to the manufacturer's instructions, provided significantly lower values. The DPD method (utilizing a Hach DR-100 kit) was the recommended method for future monitoring of the water evaluated because this method is simple, provides quick results, measures both total residual chlorine (TRC) and free residual chlorine (FRC) and is equally suitable for measurements in the field and laboratory.

熱帯産澱粉のアミロペクチンの鎖長分布について

The distribution of a-1, 4 chains in amylopectins from 4 kinds of tropical starches, i. e., from edible canna, arrowroot, cassava and sago, were examined. Potato and corn starches were used as controls. Each starch was debranched with isoamylase and then chromatographed on a Sephadex G-75 column. The eluates were fractionated into 3 peaks by measuring the reducing and total sugars and the iodine color reaction. Fraction I is thought to have been derived from amylose, and the content of fraction I agreed with the content of amylose by the amperometric iodine titration method except edible canna and corn starches. Fractions U and IQ are thought to have been derived from the long and short chains of amylopectin, and the average chain lengths of the combined II and Ilt fraction of potato and edible canna starches were approximately 18, while the values for the other four starches were approximately 16. The weight% values of fraction II of the potato and edible canna starches were 38.1 and 35.1%, respectively, and the mol% values were 16.2 and 14.8%. The weight% values of fraction II of the other four starches were 23.6-27.9% and the mol% values were 9.1-11.1% (refer to Table 2). These results show that potato and edible canna starches have more long chain branches than the other four starches. It is also shown that the edible canna, sago and corn starches were rich in branches, the chain length of which was longer than 10 and shorter than 20. In contrast, the potato and arrowroot starches were rich in short chains, with a chain length shorter than 10. The potato and edible canna starches showed X-ray diffraction patterns of the B type, while cassava, arrowroot, and corn starches were of A type, and sago starch of C type close to A. The relationship between the crystalline type and the average chain length of the amylopectins showed the tendency for the A type to have a shorter chain length than the B type.

Specificity of the DPD and Amperometric Titration Methods for Free Available Chlorine: A Review

Both the DPD and amperometric titration methods for measuring free available chlorine (FAC) are subject to interference from monochloramine and organic chloramines. The measured FAC concentration in the presence of chloramines is often significantly larger than the true FAC residual. Interference in the DPD method can be reduced by rapid titrations. Interference in the amperometric titration method can be minimized by maintaining a 200‐mV positive potential on the platinum electrode.

Evaluation of electrode methods for determining total residual chlorine in various water matrices

Abstract Five electrode systems and procedures that are widely marketed for routine determination of total residual chlorine have been evaluated in a variety of water matrices. The performance, in terms of accuracy, precision, and sensitivity, has been determined for the Orion 97–70 Residual Chlorine Electrode, Chlortect Monitor, Lazar 136A Chlorine Electrode, the forward amperometric titration method, and the back amperometric titration method. Response times for the former too systems were comparable and ranged from 20–100 seconds for chlorine concentrations ranging from 0.3–7 ppm in all water matrices. The Lazar electrode had considerably longer response times. The Chlortect Monitor and the forward amperometric titration method gave the highest sensitivity, with values of + 0.005 and .01 ppm, respectively, at the 1 ppm level. However, the Lazar Electrode could not be completely evaluated because of inconsistencies in the marketed procedures. Each system and method gave a higher precision in chlorine de...

Certification Corner

Questions in this month's “Certification Corner” cover carrying capacity of water mains, use of activated carbon, characteristics of “strong” and “weak” acids, the amperometric titration method, calcium hypochlorite, water horsepower calculation, distribution system pressure, and liquid and gaseous chlorine equivalents.

Metal complexes with chloramphenicol Part I. Polarographic investigation of copper-chloramphenicol complexes

Polarographic investigations of copper-chloramphenicol (Hf) complex were performed in 1 M NaCl which was used as the supporting electrolyte, at pH values from 11 to 13. Amperometric titration method was used to determine the composition of the complex compound. The molar ratio Cu to Hf varies with pH value of solution but not with relative KOH to Hf ratio. At pH values 12–12.5 amperometric curves indicate formation of complex compound with Cu to Hf molar ratio equal 1:2. It was found that a two-electron irreversible process takes place on the DME. The value of diffusion coefficient of the reducible species D =9.25×10 −7 cm 2 s −2 was found.

Metal complexes with chloramphenicol: Part I. Polarographic investigation of copper-chloramphenicol complexes

Polarographic investigations of copper-chloramphenicol (Hf) complex were performed in 1 M NaCl which was used as the supporting electrolyte, at pH values from 11 to 13. Amperometric titration method was used to determine the composition of the complex compound. The molar ratio Cu to Hf varies with pH value of solution but not with relative KOH to Hf ratio. At pH values 12–12.5 amperometric curves indicate formation of complex compound with Cu to Hf molar ratio equal 1:2. It was found that a two-electron irreversible process takes place on the DME. The value of diffusion coefficient of the reducible species D=9.25×10 −7 cm 2 s −2 was found.

Certification Corner

This month's “Certification Corner” contains questions on a variety of topics such as groundwater, pipe friction, purification and disinfection, cavitation, strong acid and weak acid, pump damage, and the amperometric titration method.

Polarographic behavior of copper ion in solution of o-carboxyphenylazo-acetylacetone

Copper acetate at pH 6.0 in dioxane-water solvent 25% gives with o-carboxyphenylazo-acetylacetone only one complex of composition 1:1. This complex is reduced at the dropping mercury electrode in solutions of 0.1 M sodium sulphate giving a single irreversible diffusion controlled wave corresponding to two-electron reduction. The half-wave potential of this wave is pH dependent, both in non-buffered and in acetate buffer solutions, and shifts to more negative values by increasing the pH of the solution. The relation between copper concentration and the height of the wave of the complex is linear. An amperometric titration method was given for determining the concentration of copper ion in solution.