Photometric Titration Method Research Articles

Lead distribution in rice plant leaves planted in Sukawening Village, Jatinangor District, West Bandung Regency, West Java

Lead is harmful when its amounts in food are higher than the optimum. Plants with high levels of lead may trigger the generation of reactive oxygen species and eventually cell death. Our study aimed to assess lead distribution in rice plant leaves planted in Sukawening Village, Jatinangor District, West Bandung Regency, West Java. The rice plant leaves were collected each month until 4 months. The samples were dried and underwent wet destruction. Visible spectrophotometry with the addition of xylenol orange was employed to identify the lead metal in the samples, followed by a standard addition photometric titration method. Our results indicated that lead was identified in the samples since the plant was 1 month old as proven by the Pb-xylenol orange peak at 580 nm. The level of lead in the rice plant leaves were: 1st month (0.4118 mg/kg); 2nd month (0.5232 mg/kg); 3rd month (0.6206 mg/kg); and 4th month (0.5264 mg/kg). We concluded that the lead level in the rice plants is in the range of that required by the Verdict of the Director General of the National Agency of Drug and Food Control No. 03725/B/SK/89 about the Maximum Limit of Heavy Metal Contamination in Food.

Systematic measurements of charge transfer complexes caused from 1-phenyl-1,2,3,4-tetrahydroisoquinoline and 4-aminoacetanilide with series of π-acceptors (BQ, DDQ, TCNQ).

Molecular charge-transfer interaction of a series of electron π-acceptors of 1,4-benzoquinone (BQ), 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and Tetracyanoquinodimethane (TCNQ) with selected donors of 1-phenyl-1,2,3,4-tetrahydroisoquinoline (PTHIQ) and 4-aminoacetanilide (ACE) have been studied in methanol at room temperature. The stoichiometry of the complexes was determined by photometric titration method and was found to be 1:1, in all the cases. Spectro-kinetic interaction studies along with rate constants and observed formation constants (K) indicated that the strength of the complex formations is PTHIQ-BQ<PTHIQ-DDQ<PTHIQ-TCNQ. Also, Similar observations happened in ACE-BQ and<ACE-DDQ<ACE-TCNQ systems. FT-IR results indicated that the point of interaction was identifying in NH moiety of PTHIQ and NH2 moiety of ACE with series of π-acceptor complexes. The experimental results were compared with Ab initio DFT calculations at the B3LYP/6-31+G(d) level of theory. The increasing order of the experimentally measured formation constant of CT-complexes (PTHIQ and ACE with series of acceptors) was well supported by theoretical HOMO-LUMO energy gap and drastically changes in Mulliken charges of NH moiety of PTHIQ, NH2 moiety of ACE with complexation with acceptors.

INVESTIGATION OF INTERACTION OF BROMPHENOL SYNTHES WITH CATIONIC POLYACRYLAMIDES AND APPLICATION OF IT IN THE ANALYSIS

The aim of this work was to study the interaction of bromophenol blue with cationic polyacrylamides and the development on this basis of a simple, rapid and highly sensitive technique for determining the content of copolymers of acrylamide and the chloromethylated polymer in waters containing moderate amounts of strong electrolytes. The changes in the spectra are similar to those observed for the same dyes in the presence of cationic surfactant micelles. It is shown that two types of effects appear in the presence of polymers: the shift of the acid-base equilibrium caused by the formation of the ionic associate polymer-dye and the aggregation of the dye. Optimal conditions for the formation of the ion associate are established. The presence of salts in concentrations above the critical leads to a decrease in light absorption, the appearance of a negative systematic error. The application of the photometric titration method makes it possible to compensate to a certain extent the interfering effect of inorganic ions. In the presence of inorganic salts, the shape of the photometric titration curve near the end point of the titration is washed out, but its position remains practically unchanged, which makes it possible to determine the polymer flocculant in the presence of not very large concentrations of inorganic salts. Spectrophotometric methods for determining the content of CPAA FO in production solutions or natural waters with a low level of mineralization by methods of a calibration curve and photometric titration have been developed. Method of a calibration curve allow allows to determine polymer in the range of concentrations 0,12 –1,8 μg/L. The limit of determination of CPAA FO is 0.088 μg/L. The methods are tested on artificial mixtures and artesian water.

Spectroscopic studies and molecular orbital calculations on the charge transfer reaction between DDQ and 2-aminopyridine

Charge transfer complex formation between 2-aminopyridine (donor, 2AP) with 2,3-dichloro-5,6-dicyano-p-benzoquinone (acceptor, DDQ) has been studied spectrophotometrically in acetonitrile (CH3CN). The newly formed CT-complex has reddish brown color and is characterized by the appearance of new absorption bands in the 375–650nm regions where acceptor and donor do not have any absorption. Maximum and constant absorbance of the complex was obtained after 10min at 20°C with 1mL 5×10−3M DDQ in CH3CN. Based on photometric titration method, the stoichiometry of the formed CT-complex was found to be 1:1 [(2AP)(DDQ)]. Minimum–maximum absorbances method has been applied to estimate the formation constant of the complex where it recorded large value confirming its high stability. Molecular orbital calculations utilizing GAMESS computations were carried out in order to record changes in the electronic structure and molecular geometry of the formed CT-complex. In addition, the infrared vibrational frequencies of the complex were computed and compared with experimental results.

Photometric Titration Method to Determine Bromination of Red and Yellow Dyes in Crackers

The change in absorbance of a solution may be used to follow the change in concentration of a radiation-absorbing constituent during a titration. The absorbance is directly proportional to the concentration of the absorbing constituent. This method might be useful to determine bromination reaction in colorful crackers, which are favourite food of children and adults in our country, Indonesia. In this work, we determined red and yellow dyes in unregistered crackers sold at Jatinangor, West Java, Indonesia. The dyes were isolated by extraction using a mixture of 2% of ammonia in 70% ethanol continued by preparative thin layer chromatography on GF254 silica gel plate and were separated and analyzed by using FTIR-8400 Shimadzu infrared spectrophotometer. Bromination reaction was measured by using photometric titration method. Thin layer chromatograms showed that the dyes were not either rhodamine B or tartrazine (Rf of the red and yellow dyes were 0.714 and 0.652, respectively, while those of rhodamine B and tartrazine were 0.591 and 0.673). Infrared spectroscopy showed characteristic peaks of the red dye at 3390.6 cm-1(O-H stretch), 2927.7 cm-1(C-H stretch of alkyl), 1404.1 cm-1 (O-H bend), 1616.2 cm-1(C=C stretch), and 1315 cm-1 (C-O stretch). The peaks of yellow dye occured at 3413.8 cm-1, (O-H stretch), 3213.2 cm-1 (C-H stretch of alkene), 2927.7 cm-1(C-H stretch of alkyl), 1400.2 cm-1(O-H bend), 1624.0 cm-1 (C=C stretch). Visible spectroscopy showed maximum wavelengths at 551 nm (red dye) and 432 nm (yellow dye). Photometric titration to determine bromination reaction in the dyes showed a decreasing in absorbance due to the conversion of colored analytes to colorless products. This fact indicated that bromination reaction was occured in the red and yellow dyes molecules via electrophilic addition reaction on its double bond.

Determinação de ferro (III) em produtos farmacêuticos por titulação fotométrica

This paper describes a simple, precise and low-cost photometric titration method for iron (III) determination in pharmaceutical preparations. The photometric titration system was constructed using the peristaltic pump of a conventional spectrophotometer. The method is based on titration of iron (III) with EDTA using salicylic acid as indicator. The absorption of the iron (III)-salicylic acid complex was monitored spectrophotometrically at 525 nm. The limit of quantification was 5 µg of iron (III). The photometric titration procedure was applied for the determination of iron (III) in samples of ferrous sulfate and ferric hydroxide polymaltose complex. The procedure showed sensibility, reproducibility and accuracy for use as a method for the routine analysis of iron (III) in pharmaceutical formulations.

Thermodynamics study of the dimerization equilibria of rhodamine B and 6G in different ionic strengths by photometric titration and chemometrics method

The dimerization constants of rhodamine B and 6G have been determined by studying the dependence of their absorption spectra on the temperature in the range 20–80 °C at different total concentrations of rhodamine B (5.89 × 10 −6 to 2.36 × 10 −4 M) and rhodamine 6G (2.34 × 10 −5 to 5.89 × 10 −4 M) and in different concentrations of LiCl, NaCl and KCl salts as supporting electrolytes. The monomer–dimer equilibrium of rhodamine B and 6G have been determined by chemometrics refinement of the absorption spectra obtained by thermometric titrations performed at different ionic strengths. The quantitative analysis of the data of undefined mixtures, was carried out by simultaneous resolution of the overlapping spectral bands in the whole set of absorption spectra. The dimerization constants are varied by changing the ionic strength and the degree of dimerization are decreased by increasing of the ionic strength of the medium. The enthalpy and entropy of the dimerization reactions were determined from the dependence of the equilibrium constants on the temperature (van’t Hoff equation). From the thermodynamic results the TΔ S°–Δ H° plot was sketched. It shows a fairly good positive correlation which indicates the enthalpy–entropy compensation in the dimerization reactions (compensation effect).

Determination of Cationic Surfactants by a Photometric Titration Method with Crystal Violet as a Color Indicator

The cationic dye, crystal violet, is applied to the indicator for the determination of cationic surfactants such as benzyldimethyltetradecylammonium chloride by photometric titration, using a potassium poly(vinyl sulfate) (PVSK) solution as a titrant. Before the titrant is added to the sample solution containing crystal violet, the absorbance of the crystal violet itself is observed because the crystal violet does not react with the cationic surfactants in the sample solution. Before the equivalence point, the absorbance of the sample solution decreased slightly as the amount of added titrant increases. The decreased absorbance may be due to that the cationic surfactant in the sample solution, preferentially forms ion associate with the titrant and, hence, the sample solution is diluted with the titrant. After the end‐point, the absorbance of the sample solution decreases abruptly by abrupt decrease of the concentration of crystal violet caused by the association reaction between the crystal violet and the titrant. The end‐point of the titration is detected as the break point of the titration curve. The linear relationships between the concentration of cationic surfactants and the end‐point volume of the titrant existed in the concentration range from 0 to 2.5 × 10−5 M for benzyldimethyltetradecylammonium chloride, cetylpyridinium chloride (CPC), and stearyltrimethylammonium chloride (STA).

Development and validation of a photometric titration method for the quantitation of sodium chondroitin sulfate (bovine) in Cosequin® DS chewable tablet

A photometric titration method was developed and validated to quantitate sodium chondroitin sulfate in raw materials and Cosequin® DS chewable tablet 1 1 Cosequin® DS chewable tablet contains glucosamine HCl, sodium chondroitin sulfate, manganese ascorbate, and flavoring agents. . About 0.1% (w/v) cetylpyridinium chloride was used to titrate sodium chondroitin sulfate with photometric indication at wavelengh 420 nm. The standard curves for sodium chondroitin sulfate showed linearity ( r≥0.99) over the selected concentration range from 0.6 to 1.4 mg/ml. The chewable tablet was ground to fine powder and extracted with water and the resulting solutions filtered through a 0.45 μm membrane filter. Recovery between 97 and 103%,. The intra- and inter- day precision as indicated by the relative standard deviation (R.S.D.) were not greater than 0.33 and 0.78%, respectively. The method was found to be specific and with excellent linearity, accuracy and precision and is well suited for the quantitation of sodium chondroitin sulfate in raw material and Cosequin® DS chewable tablet.

A New Spectrophotometric Method for the Determination of Dithianon in Commercial Formulations and Its Residues in Foodstuffs

A new, simple, and rapid spectrophotometric method for the microdetermination of dithianon, on the basis of its reaction with a dithiocarbamate, is described. The red color, which develops instantaneously when mixing the fungicide with the reagent in acetonitrile, is stable for at least 1 h and is measured at 520 nm. Beer's law is applicable up to 12 micrograms/mL dithianon concentration. The method has been successfully adapted to the analysis of the fungicide in commercial formulations and its residues on grains and apple (fruit and leaves). A photometric titration method for formulation analysis of the fungicide has also been developed.

Photometric titration of small amounts of cationic surfactants in an aqueous medium

A photometric titration method for cationic surfactants with tetrabromophenolphthalein ethyl ester (TBPE) as an indicator was developed. In the presence of a non-ionic surfactant (Triton X-100), TBPE was dissolved in an acidic aqueous medium, giving a yellow colour in the acidic form (TBPE·H). When a bulky cation (Q+) was added, TBPE·H reacted with Q+ to form an ion associate (Q+·TBPE–), and the colour changed from yellow to blue. This colour reaction was used for the detection of the end-point. Direct and indirect titration methods for the determination of cationic surfactants were examined. Dodecylbenzenesulfonate ion (DBS–) was used as a titrant for cationic surfactants in the direct titration. The colour changed from blue to yellow at pH 3.6, and absorbance changes were monitored with a fibre-optic sensor with a 630 nm interference filter. Benzyldimethyltetradecylammonium (zephiramine) ion was found to be the preferred titrant in the indirect titration. The titrant was added to a solution of cationic surfactant containing a known excess amount of anionic surfactant DBS– at pH 3.6. Cationic surfactants at concentrations from 5 × 10–6 to 1 × 10–3 mol dm–3 could be determined.

Determination of anionic surfactants in an aqueous medium by differential photometric titration method.

Determination of anionic surfactants in an aqueous medium by differential photometric titration method.

Novel indicator system for the photometric titration of ionic surfactants in an aqueous medium. Determination of anionic surfactants with distearyldimethylammonium chloride as titrant and tetrabromophenolphthalein ethyl ester as indicator

A photometric titration method for anionic surfactants with tetrabromophenolphthalein ethyl ester (TBPE) as indicator was examined. In the presence of a non-ionic surfactant (Triton X-100), TBPE was dissolved in an acidic aqueous medium giving a yellow colour in the acidic form (TBPE·H). When a bulky cation (Q+) was added, TBPE·H reacted with Q+ to form an ion associate (Q+·TBPE–), and the colour changed from yellow to blue. Distearyldimethylammonium ion was the preferred titrant. The titrant was added to a solution of anionic surfactant at pH 3.2, and absorbance changes were monitored with a fibre-optic sensor with a 640 nm interference filter. Anionic surfactants at concentrations from 5 × 10–6 to 2 × 10–4 mol dm–3 could be determined, and the standard deviations and the relative standard deviations for ten replicate titrations of 25 cm3 of 2 × 10–4 mol dm–3 of various anionic surfactants were 0.03–0.15 cm3 and 0.03–1.65%, respectively.

Direct photometric titration of tellurium

A direct photometric titration method has been developed for the determination of tellurium. Tellurium(IV) is titrated with potassium dichromate in 2–6 M nitric acid (or 1–4 M perchloric acid) at 380–430 nm (blue-violet filter). Selenium(IV) does not interfere.

The spectrophotometric and titrimetric determination of gold with ferroin as reagent

A spectrophotometric and a photometric titration method in a two-phase system for the determination of gold with ferroin is reported. Both methods are rapid and reproducible with an accuracy of ±1%. In the spectrophotometric determination Co2+, Cu2+, Ni2+ , Fe3+, Zn2+, Mn2+ and Cr3+ do not interfere with the determination of gold and Pt4+, Pd2+, Hg2+, Ir4+ and Os4+ can be tolerated up to a ratio of 1:1. The titrations can also be carried out in the presence of a number of diverse ions, e.g. Ni2+, Cu2+, Co2+, Fe3+, Zn2+, Cr3+, Mn2+, without interference; the platinum metals and Hg2+ cause interference but, by the use of the spectrophotometric procedure, this can be reduced.

Photometric microtitrations. I

A photometric titration method for the microdetermination of lead with dithizone as metallochromic indicator is described. The optimal conditions for the titration were derived from a spectrophotometric study. In a 50% (by volume) ethanolic solution buffered with hexamethylenetetramine to pH 5, the method permits an accurate titration of microgram concentrations of lead. The absorbance was followed spectrophotometrically at 590 nm. In the range of 2–20μg of lead per 10 ml the relative error can be kept easily within limits of ± 1–3%.

Studies on the analysis of pharmaceuticals by photometric titration method. X. Determination of vitamin C by potassium ferricyanide

Studies on the analysis of pharmaceuticals by photometric titration method. X. Determination of vitamin C by potassium ferricyanide

光度滴定法による薬品分析法の研究 (第1報)

光度滴定法による薬品分析法の研究 (第1報)

Photometric titration of phenols

Abstract A photometric titration method for the determination of phenols has been developed which is applicable to concentrations of phenols of 10 −3 molar or greater with an average deviation of about 1 %. Phenols with aqueous p K A values ranging from 5 to approximately 11 were titrated without difficulty. Also, differentiating titrations of phenol mixtures were successfully performed.