Mahmure Üstün Özgür

Third order derivative spectrophotometric determination of ascorbic acid in fruits and vegetables

Ascorbic acid (AA) has been determined in kiwi, parsley and grapefruit by third order derivative spectrophotometry without using any separation or background correction techniques and reagents. The method is based on the measurement of the distances between two extremum values (peak-to-peak amplitudes) in the third order derivative spectra of the extracts. A metaphosphoric acid (3% w/v)-acetic acid (8% v/v) mixture was found to be the most suitable extraction solution. In the third order derivative spectrum, the extrema of 259.4 nm and 276.2 nm were used for the quantitative determination of AA in kiwi, and the extrema of 227 nm and 237 nm were used for the quantitative determination of AA in parsley and grapefruit. Calibration curves were constructed for the 2.0-10.0 mug ml(-1) concentration range. Relative standard deviations were calculated from the assay results of 14 samples. They were found to be in the ranges of 0.53-2.45% and 0.50-1.41% for the proposed method and the Association of Official Analytical Chemists (AOAC) method, respectively. The obtained results were statistically compared with those of the official method of AOAC using the F test. There was no significant difference between the precisions at a 95% confidence level.

Validated Spectrophotometric Methods for Simultaneous Determination of Food Colorants and Sweeteners

Two simple spectrophotometric methods have been proposed for simultaneous determination of two colorants (Indigotin and Brilliant Blue) and two sweeteners (Acesulfame-K and Aspartame) in synthetic mixtures and chewing gums without any prior separation or purification. The first method, derivative spectrophotometry (ZCDS), is based on recording the first derivative curves (for Indigotin, Brillant Blue, and Acesulfame-K) and third-derivative curve (for Aspartame) and determining each component using the zero-crossing technique. The other method, ratio derivative spectrophotometry (RDS), depends on application ratio spectra of first- and third-derivative spectrophotometry to resolve the interference due to spectral overlapping. Both colorants and sweeteners showed good linearity, with regression coefficients of 0.9992–0.9999. The LOD and LOQ values ranged from 0.05 to 0.33 μgmL−1 and from 0.06 to 0.47 μgmL−1, respectively. The intraday and interday precision tests produced good RSD% values (<0.81%); recoveries ranged from 99.78% to 100.67% for all two methods. The accuracy and precision of the methods have been determined, and the methods have been validated by analyzing synthetic mixtures containing colorants and sweeteners. Two methods were applied for the above combination, and satisfactory results were obtained. The results obtained by applying the ZCDS method were statistically compared with those obtained by the RDS method.

Sumac Leaves as a Novel Low-Cost Adsorbent for Removal of Basic Dye from Aqueous Solution

Sumac Leaves (SL) (Rhus Coriaria L. ) were investigated as an inexpensive and effective adsorbent for the adsorption of methylene blue (MB) from aqueous solution. The effects of initial dye concentration, initial solution pH, phases contact time, and adsorbent dose on the adsorption of MB on SL were investigated. The amount of dye adsorbed was found to vary with initial solution pH, Sumac Leaves dose, MB concentration, and phases contact time. The Langmuir and Freundlich adsorption models were evaluated using the experimental data and the experimental results showed that the Langmuir model fits better than the Freundlich model. The maximum adsorption capacity was found to be 151.69 mg/g from the Langmuir isotherm model at 25°C. The value of the monolayer saturation capacity of SL was comparable to the adsorption capacities of some other adsorbent materials for MB. The adsorption rate data were analyzed according to the pseudo-first order kinetic and pseudo-second order kinetic models and intraparticle diffusion model. It was found that kinetic followed a pseudo-second order model.

A SPECTROPHOTOMETRIC METHOD FOR THE DETERMINATION OF PRAZOSIN HYDROCHLORIDE IN TABLETS

A rapid and sensitive analytical method was developed for the spectrophotometric assay of prazosin hydrochloride. The method is based on the formation of a coloured derivative between the drug and 1,2-naphthoquinone-4- sulphonic acid sodium salt (NQS). The reaction proceeds quantitatively at pH 4.5 and 70°C for 40 min. After the extraction of the derivative with chloroform: n-butanol (3:1), the absorbance was measured at 400 nm. The method was applied to commercially available tablets and the results were statistically compared with those obtained by ultraviolet spectrophotometric and differential pulse polarographic methods using t- and F-tests.

Four Derivative Spectrophotometric Methods for the Simultaneous Determination of Carmoisine and Ponceau 4R in Drinks and Comparison with High Performance Liquid Chromatography

Four simple, rapid, and accurate spectrophotometric methods were developed for the simultaneous determination of two food colorants, Carmoisine (E122) and Ponceau 4R (E124), in their binary mixtures and soft drinks. The first method is based on recording the first derivative curves and determining each component using the zero-crossing technique. The second method uses the first derivative of ratio spectra. The ratio spectra are obtained by dividing the absorption spectra of the binary mixture by that of one of the components. The third method, derivative differential procedure, is based on the measurement of difference absorptivities derivatized in first order of solution of drink samples in 0,1 N NaOH relative to that of an equimolar solution in 0,1 N HCl at wavelengths of 366 and 451 nm for Carmoisine and Ponceau 4R, respectively. The last method, based on the compensation method is presented for derivative spectrophotometric determination of E122 and E124 mixtures with overlapping spectra. By using ratios of the derivative maxima, the exact compensation of either component in the mixture can be achieved, followed by its determination. These proposed methods have been successfully applied to the binary mixtures and soft drinks and the results were statistically compared with the reference HPLC method (NMKL 130).

Ultrasound-Assisted Extraction of Anthocyanins from Red Rose Petals and New Spectrophotometric Methods for the Determination of Total Monomeric Anthocyanins

In this study, four extraction technologies for the extraction of anthocyanins (Acyns) from red rose petals (RRPs) were investigated and compared, including ultrasound-assisted extraction (UAE), reflux extraction, Soxhlet extraction, and marinated extraction. UAE was the most suitable for the extraction of Acyns from RRPs because of its high extraction efficiency and short extraction time. The results showed that the best conditions for UAE are an extraction solution of ethanol-0.1 N HCl (80 + 20, v/v), a solid-to-liquid ratio of 1:40 g/mL, a temperature of 30°C, and an extraction time of 15 min performed three times. Using such conditions, 320.4 mg Acyns/100 g RRPs was extracted. UAE was followed by two new difference spectrophotometric (DS) methods, which were developed for the fast and simple determination of Acyns in RRPs. Under the optimum experimental conditions, a linear response was observed for Acyns in the range of 12.5-62.5 μg/mL for the two proposed methods, with correlation coefficients (r) ranging from 0.9988 to 0.9995. The mean recovery values of Acyns for the DS methods were in the range of 99.8-101.5%, and the RSD was 0.5%. The respective LOD and the LOQ values were 1.4 and 4.8 for DS1 and 1.1 and 3.6 μg/mL for DS2. The stability of Acyns was also studied.

Removal of amitraz from aqueous solutions on clay by adsorption technique at industrial scale

Abstract Amitraz (AZ) that is used as acaricide was extracted by using clay adsorbent. The experimental data were modeled via Langmuir and Freundlich isotherms in which adsorption data fit well. The monolayer adsorption capacity was found as 28.53 mg × g−1 at a temperature of 30 °C. The effects of the phases contact time, the initial solution pH value and the initial pesticide concentration were investigated regarding the points of adsorption equilibrium and yield. The adsorption kinetics were investigated by applying pseudo-first-order, pseudo-second-order and intra-particle diffusion laws. Adsorption of AZ was found to be best fitted by the pseudo-second-order model. The intra-particle diffusion also plays an important role in adsorption phenomenon. This adsorption is a physical and spontaneous phenomenon. The pesticide removal by adsorption technique was successfully applied in industrial plants.

Sorption of Zn(II) and Pb(II) Ions by a New Resin Synthesized from Sumac Tannin and Gelatin

Recently, the interest on biomaterials and especially in tannins was growing and some attractive results were obtained in the adsorption of some metals by tannin adsorbents. Tannins are widely distributed in nature and have multiple adjacent polyhydroxyphenyl groups in their chemical structure which have extremely high affinity for heavy metal ions. This study will describe how tannin can be used as an effective zinc and lead sorbent by the use of tannin resins. Batch method was used in the experiments in which pH profile, adsorption time, adsorbent/liquid ratios, initial concentration of metal ions, adsorbent amount and temperature were investigated to determine binding properties of adsorbent for the Zn(II) and Pb(II) ions.

Sorption of Pb(II) and Zn(II) Ions from Aqueous Solution by Tannin Resins

Recently, the interest on biomaterials and especially in tannins was growing and some attractive results were obtained in the adsorption of some metals by tannin adsorbents. Tannins are widely distributed in nature and have multiple adjacent poly- hydroxyphenyl groups in their chemical structure which have extremely high affinity for heavy metal ions. This study will describe how tannin can be used as an effective zinc and lead sorbent by the use of tannin resins. Batch method was used in the experiments in which pH profile, adsorption time, adsorbent/liquid ratios, initial concentration of metal ions, adsorbent amount and temperature were investigated to determine binding properties of adsorbent for the Zn(II) and Pb(II) ions.

Simultaneous Spectrophotometric Determination of Food Additives (Benzoic Acid, Caffeine, Aspartame and Acesulfame-K) in Cola Drinks by PLS Multivariate Calibration Method

Aspartame (Apt), Acesulfame-K (Ace-K) low-calorie, high-potency artificial sweeteners are currently used in beverages and dietary food and drinks. Their increased application in food and drink products has given a new impetus to develop fast and accurate methods for their determination. Absorption spectra of Asp, Caf, Ace-K and BA strongly overlap. Therefore a direct determination of these analytes in quaternary mixture is impossible without a separation step. In order to overcome this difficulty partial least squares (PLS) method has been proposed. A spectrophotometric method for the routine, rapid end simultaneous determination of Ace-K, Caf, Aspt and BA in cola drinks was investigated. A calibration set contain- ing between 3 - 5 μ g mL -1 of Ace-K, Caf, and BA, 5 - 7 μ g mL -1 of Aspt was used. The method involves the use of 27 standard mixtures of the four compounds assayed, considered at three concentration levels and measured of samples in a 0.1 N H 3 PO 4 . The designed and optimized training set of calibration was applied to the determination of four food additives in several synthetic mixtures. Three com- mercial cola drinks (coca-cola, pepsi-cola, cola-turka) that contained the four addi- tives were also satisfactorily analyzed without separation step.