Simultaneous Spectrophotometric Determinations Research Articles

Selective separation and determination strategy for monitoring E100, E127, E129 and E133 in foodstuffs: Vortex assisted sequential-simultaneous liquid phase micro-extraction

A green, speedy and handy, vortex assisted sequential-simultaneous liquid phase micro-extraction procedure (VA-SS-LPME) was established first time without using any instrumental chromatographic techniques for separation, preconcentration and spectrophotometric determination of four important popularly and widely used food colorants, namely curcumin (E100), erythrosine (E127), allura red (E129) and brilliant blue (E133). Here, n-nonanol and n-nonanol based deep eutectic solvent were used as extraction solvents. The procedure has included two simultaneous and sequential separation steps by different extractants and two simultaneous UV–vis spectrophotometric determination steps. First, simultaneous separation of E100 and E127 from aqueous solution containing E129 and E133 was achieved and then simultaneous separation of E129 and E133 from aqueous solutions was applied and simultaneous spectrophotometric determinations were performed finally for binary mixture dyes (E100 and E127) and (E129 and E133). The parameters including pH, types and amounts of extractants, vortex time and rate, centrifugation time and rate were investigated in detail for sequential two steps separation and quantitative simultaneous extraction of the dyes. Interference effect of matrix ions, target and other dyes were examined. Possible envisaged extraction mechanisms were elucidated. Green analytical procedure index (GAPI) and analytical eco-scale (AES) parameters of the procedure were determined. As last, E100, E127, E129 and E133 contents of some foodstuffs and pharmaceuticals such as confectioneries, beverages, drugs and syrups were determined by applying optimized procedure. Colourful food additive concentrations of real samples were determined between 2.9 and 93.8 µg/g and 5.3–112.4 µg/mL for solid and liquid samples, respectively.

Matrix isolation with an ion transfer device for interference-free simultaneous spectrophotometric determinations of hexavalent and trivalent chromium in a flow-based system

Chromium speciation by spectrophotometric determination of hexavalent chromium (Cr(VI)) with diphenylcarbazide (DPC) has several problems. These include: (1) the inability to directly detect trivalent chromium (Cr(III)) with DPC, (2) positive interference in Cr(VI) determination by other metal cations and (3) negative interference by any reducing agent present in the sample. These are addressed with an ion transfer device (ITD) in a flow injection analysis system. We previously developed the ITD for electrodialytic separations. Here we separate oppositely charged Cr(III) and Cr(VI) species by the ITD into two different acceptor solutions within ~5 s. The acceptor solutions consist of buffered H2O2 to oxidize the Cr(III) to Cr(VI). Then DPC is added to either acceptor to measure Cr(III) and Cr(VI) spectrophotometrically. The system was optimized to provide the same response for Cr(VI) and Cr(III) with limits of detection (LODs, S/N=3) of 0.5 μg L-1 for each and a throughput rate of 30 samples h-1. The ITD separation was also effective for matrix isolation and reduction of interferences. Potential cationic interferences were not transferred into the anionic Cr(VI) acceptor stream. Much of the organic compounds in soil extracts were also eliminated as evidenced from standard addition and recovery studies.

English

The use of cyanidin (3, 31 41 5, 7 – pentahydroxyflavylium chloride) extracted from a tropical plant Hibiscus sabradiffa L. as a chelating reagent for simultaneous spectrophotometric determinations of ions of Pb, Hg, Cd, As and Ni in mixed aqueous solution is reported. The purified extract of the dried calyces of the Roselle plant was characterized and the results compared with literature values. Complexation of the metals ions with cyanidin and scanning through 200-700 nm in a UV –VIS spectrophotometer gave the wavelength of maximum absorption (λmax) of these metal complexes to be 389.6, 360.0, 357.8, 396.8 and 401.0 nm for Pb(II); As(II); Cd(II); Hg(II) and Ni(II) complexes respectively indicating appreciable bathochromic shifts compared to pure cyanidin absorption at 283.2 nm. The effect of pH on the determinations was studied and a pH value of 5 was found to be the optimal. Calibration curve plots of the complexes showed linearity between concentration of 0.1 to 5.0 ppm. This method offer cheap, simple, rapid, sensitive, and eco-friendly technique for simultaneous determination of trace heavy metals in mixed aqueous solutions and have potentials for environmental and biological samples.   Key words: Cyanidin, ultraviolet (UV) spectroscopy, simultaneous, chromogenic, eco friendly, trace metals.

Simultaneous Spectrophotometric Determination of Metformin Hydrochloride and Glibenclamide in Binary Mixtures Using Combined Discrete and Continuous Wavelet Transforms

In this work, a combined discrete and continuous wavelet transform analysis was developed for simultaneous spectrophotometric determinations of metformin hydrochloride and glibenclamide, two antidiabetic drugs, in binary mixtures without any chemical pretreatment. Absorption spectra were subjected to the 4-level db4 discrete wavelet transform (DWT) for signal de-noising. Selected continuous wavelet transform (CWT) families (rbio3.1 with scaling factor, a = 80, and gaus2, a = 60) were applied on these de-noised signals. Finally, a zero-crossing technique was used for the construction of calibration curves for both drugs. The proposed method was validated by analyzing synthetic mixtures of the investigated drugs with various concentrations. The amount of metformin hydrochloride and glibenclamide were determined by using CWT amplitudes in zero-crossing points. The mean recovery values of metformin hydrochloride and glibenclamide were found between 98.6-102.0 and 97.9-102.4% for rbio3 and 98.3-101.2 and 97.1-101.4% for gaus2 families, respectively. The obtained results showed that the developed method is a simple, rapid and precise procedure for the simultaneous determination of metformin hydrochloride and glibenclamide in binary mixtures.

Simultaneous Spectrophotometric Determination of Orthophosphate and Silicate Ions in River Water Using Ion-Exclusion Chromatography with an Ascorbate Solution as Both Eluent and Reducing Agent, Followed by Postcolumn Derivatization with Molybdate

Ion-exclusion chromatography was examined for the simultaneous spectrophotometric determinations of orthophosphate and silicate ions in river water using an ascorbate solution as both an eluent and a reducing agent, followed by postcolumn derivatization using molybdate. The detector responses for both ions increased with increased ascorbic acid concentration in the eluent, but peak tailing was observed for the orthophosphate ion. This suggests that the amounts of undissociated orthophosphate ions increased with decreased eluent pH, resulting in the penetration of the phosphate to the Donnan's membrane formed on the resin surface. Using a neutral sodium ascorbate solution as an eluent, the peak shape was improved. With optimized separation and derivatization conditions (eluent, 20 mM sodium ascorbate; color-forming reagent, 10 mM sodium molybdate-60 mM sulfuric acid; flow rates of eluent and color-forming reagent, 0.4 and 0.2 mL min(-1); coil length, 6 m), the detection limits of orthophosphate and silicate ions were 0.9 and 1.0 microg L(-1), respectively. This method was successfully applied to the determination of orthophosphate and silicate ions in Kurose River water and the quantitative evaluations of the effects of water intake to a reservoir and discharge from a biological sewage treatment plant on the fluxes of these ions in the river.

Comparison of multivariate calibration methods to determine simultaneously mebendazole–cambendazole and mebendazole–thiabendazole in pharmaceutical preparations by UV–visible spectrophotometry

Three multivariate calibration methods, Principal Component Regression (PCR), the K-matrix method and Q-mode factor analysis followed by varimax and Imbrie's oblique rotations were applied to the simultaneous spectrophotometric determinations of mebendazole (MBZ)–cambendazole (CBZ) and thiabendazole (TBZ)–mebendazole in commercial samples of Exelmin and Helmiben. The calibration set concentrations were selected to contain a ±10% variation in the quantity of active ingredients as declared by the manufacturer. The Q-mode factor analysis provides superior results for the two pharmaceutical formulations. The K-matrix method proved to be totally inadequate for these determinations. Almost all Q-mode results have relative errors much smaller than 5% of the active ingredient contents. This investigation shows that PCR and Q-mode factor analysis can be used to determine MBZ–CBZ and TBZ–MBZ in commercial drugs.

Flow-Injection Simultaneous Determination of Iodate and Periodate by Spectrophotometric and Spectrofluorometric Detection

A simple and accurate procedure for simultaneous spectrophotometric and spectrofluorometric determinations of iodate and periodate in aqueous media has been developed. The determination of periodate is based on the selective oxidation of Alizarin Navy Blue to produce a fluorescent compound, that can be found by flow-through spectrofluorometric detection (λex=370 nm, λem=516 nm). On the other hand, periodate and iodate react with iodide to produce iodine, which is determined by spectrophotometric detection at 349 nm. The injected sample was split into two streams, one of which was directly treated with Alizarin Navy Blue and passed to the flow cell of the spectrofluorometer. A fluorescence signal at 516 nm was due to periodate. The other stream was treated with iodide and sulfuric acid and then passed through the flow cell of the spectrophotometer. The increase in absorbance at 349 nm was due to periodate and iodate. The influences of the acid concentration, reagent concentration and manifold variables were studied. The effect of diverse ions on the determination of periodate and iodate by the proposed method was also investigated. Periodate and iodate can be determined in the range of 1.0×10-5 - 2.2×10-4 M and 1.0×10-5 - 2.0×10-4 M, respectively. Within the 3σ detection limit was 3.5×10-6 M for periodate and 1.0×10-6 M for iodate, respectively. Applying this method to the analysis of iodate and periodate in artificial fresh-water samples was successfully carried out.

Simultaneous spectrophotometric and volumetric determinations of amoxycillin, ampicillin and cloxacillin in drug formulations: reaction mechanism in the base catalysed hydrolysis followed by oxidation with iodate in dilute acid solution

A method for the analysis of degraded products of amoxycillin, ampicillin and cloxacillin in drug formulations, obtained as a result of their base hydrolysis is described. Simultaneous spectrophotometric and volumetric determinations of the antibiotic is based on the neutralization of the degraded product by dilute hydrochloric acid to get a pH ∼2 to be conducive for redox titration using potassium iodate as titrant. A red purple colour is developed in carbon tetrachloride at the end point. Spectrophotometry is done after separating the organic layer and measuring the absorbance of red-purple colour at λ max 520 nm. The pathways of different degraded products and their oxidation mechanism is described on IR, TLC and UV spectroscopic studies.

Simultaneous spectrophotometric determinations of cobalt, nickel and copper using partial least squares based on singular value decomposition

The partial least squares modeling based on singular value decomposition was applied for the simultaneous spectrophotometric determination of Co(II), Ni(II) and Cu(II) as their ammonium 2-amino-1-cyclohexan-1-dithiocarbamate complexes. The latent variable calculation in this partial least squares modeling is not an iterative technique. The detection limits for Co(II), Ni(II) and Cu(II) were 0.072, 0.021 and 0.063 μg/ml, respectively. The application of the method was confirmed by analysis of these metals in sample alloys.

Continuous flow analysis: Simultaneous spectrophotometric determinations of metals

Methods for the simultaneous determination of aluminium and manganese, aluminium and iron(III), and calcium and magnesium, based on the use of dual spectrophotometric detection in segmented flow analysis, were developed. Ligand-exchange reactions or reactions at different rates were used. The methods were tested on both synthetic and real samples (soil extracts, sedimentary rock). Up to 32 samples per hour can be analyzed. A rapid flow analyzer with double-beam spectrophotometer was used for the analyses. Relative standard deviations were 1.0–6.5%.

Criteria for selecting analytical wavelengths for multicomponent mixtures by the CPA matrix method and simultaneous spectrophotometric determination of niobium and tantalum

The reversed matrix representation of the Lambert-Beer law (CPA matrix method) is applied in simultaneous spectrophotometric determinations. Restrictions on the selection of analytical wavelengths in applying the CPA matrix method are investigated experimentally and theoretically. Four criteria for selecting suitable wavelengths are described. A spectrophotometric procedure for niobium and tantalum with salicylfluorone and cetyltrimethylammonium bromide in the presence of tartaric acid was developed and used for the simultaneous determination of niobium and tantalum by the CPA matrix method. The absorption maxima were at 520 and 513 nm, respectively. Measurements at six wavelengths in the range 500–530 nm provided data from which niobium (0.04–0.4 μm ml −1) and tantalum (0.08–0.8 μg ml −1) were evaluated, with relative standard deviations of <2.

Simultaneous spectrophotometric determinations of cobalt, nickel, and iron

2,2′-Dipyridylketone-2-pyridylhydrazone (DPPH) was used for the simultaneous determination of cobalt (0.6–6 ppm) and iron (1–12 ppm). Interferences from nickel, copper, zinc, and manganese were avoided by controlling the pH at 3.5. Isoquinoline-3-aldehyde-2-pyridylhydrazone (IAPH) was used for the simultaneous spectrophotometric determination of cobalt, nickel, and iron. Interferences from copper, zinc, and manganese were avoided by use of EDTA and ammonia.

Selection of wavelengths for optimum precision in simultaneous spectrophotometric determinations

A general method for the selection of wavelengths for optimum precision in simultaneous determinations employing absorption spectrophotometry.