научный журнал по химии Журнал аналитической химии ISSN: 0044-4502

QING-ZHOU ZHAI, WEI-HUA HU, XUE-MING ZHANG — 2014 г.

In the medium of 0.45 M nitric acid IO oxidizes KBr to produce Br2, which oxidizes DBS-arsenazo (DBS-ASA) to decolour. Based on this principle, a new method for the determination of iodate has been developed. The KIO3 KBr (DBS-ASA) system presents a maximum absorption at 530 nm. At that wavelength, Beers law is obeyed over the range of 0.050 0.60 g/mL of IO presenting a linear relationship. The apparent molar absorptivity is 1.75 ? 105 L/mol cm and the detection limit is 0.048 g/mL. This method has been successfully applied to the determination of c IO ontent in the iodized table salt sample with good results.

SENA CAGLAR — 2014 г.

A novel, simple and rapid stability-indicating spectrofluorimetric method has been developed for the determination of valacyclovir hydrochloride in tablets and spiked plasma samples. Method based on the reaction between valacyclovir and fluorescamine in borate buffer solution of pH 9.0 to give highly fluorescent derivatives that were measured at 475 nm using an excitation wavelength of 390 nm. The method has linear relation with fluorescence intensity in the concentration range of 0.25 1.25 . The developed spectrofluorimetric method was validated with respect to linearity, precision, sensitivity, accuracy and selectivity. The degradation behavior of the drug was also investigated: the drug solution was subjected to neutral, acid and alkali hydrolysis, oxidation, thermal stress and exposure to the sunlight. The method proved to be selective and useful for the investigation of the stability of valacyclovir. Successful applications of the developed method for the drug determination in tablets and spiked plasma samples were also performed.

MEHTA P.J., PATEL D.C., PATEL N.R., SHERIKAR O.D. — 2014 г.

Three accurate, sensitive and reproducible methods are described for the quantitative determination of alprazolam (ALP) and propranolol hydrochloride (PNL) in their combined dosage form. The first method involves an RP–HPLC separation on the C18 column using acetonitrile – 25 mM ammonium acetate buffer and 0.2% triethylamine (pH of buffer adjusted to 4 with glacial acetic acid) in the ratio of 35 : 65 (v/v) as mobile phase. Symmetrical peaks with good separation, ALP at 9.3 min and PNL at 3.5 min, were achieved. Quantification was done with photo diode array detection at 255 nm over the concentration ranges of 0.5–50 and 10 250 g/mL for ALP and PNL, respectively. The second method is based on the separation of drugs by HPTLC using chloroform–methanol–ammonia 7 : 0.8 : 0.1 (v/v/v) as mobile phase. Quantification was achieved using UV detection at 248 nm over the concentration range of 100–600 ng/spot and 5 30 g/spot for ALP and PNL, respectively. The third method involves dual wavelength UV-visible spectrophotometric method. It is based on the determination of PNL at 319.4 nm using its absorptivity value and ALP at 258.2 nm after deduction of absorbance due to PNL. Quantification was achieved over the concentration range of 1–40 and 80 200 g/mL for ALP and PNL, respectively. All methods were validated according to ICH guidelines and successively applied to marketed pharmaceutical formulation, and the results of all three methods were compared statistically as well. No interference from the tablet excipients was found.

HASHEMI P., RAHIMI A. — 2014 г.

A dispersive liquid–liquid microextraction method based on solidification of a floating organic drop (DLLME-SFO) was developed for HPLC determination of -carotene in human serum. A narrow-neck glass tube was used for simple and rapid collection of the solidified organic phase from aqueous surface after its centrifugation and cooling in a water bath. Acetone and 2-decanol were used as the disperser and organic phases, respectively. Effects of salt concentration and phase volumes on the extraction of the analyte were optimized using a central composite design method. During the optimization, a spectrophotometric method was used for determinations. Under the optimized conditions, an extraction recovery of 99.0 ± 2.4% was obtained for five replicated analyses of -carotene with an enrichment factor of 40. A detection limit of 0.08 was achieved. The proposed method was successfully applied to the determination of -carotene in human serum samples.

ALANON MOLINA A., BORAS N., MURILLO PULGARIN J.A. — 2014 г.

A novel and simple method is presented for the determination of norfloxacin in human urine by matrix isopotential synchronous fluorescence spectrometry (MISF). This method is useful for the determination of compounds in samples with unknown background fluorescence, such as norfloxacin in urine, without the need for tedious sample pre-treatment. The method was performed in ethanol–water medium (10%, v/v), at an apparent pH of 4.8 provided by adding sodium acetate–acetic acid buffer solution. In the determination of norfloxacin in urine the fluorescent intensity varied linearly with its concentration from 20 to 200 ng/mL. An exhaustive statistical analysis has been developed to all calibration graphs, this treatment includes robust regression such as least median of squares, which also detects outliers and leverage points. The overall least-squares regression has been applied to find the more exact straight line that fits the experimental data. The error propagation has been considered to calculate the detection limit and the repeatability of the method. The method shows very low detection limits with acceptable recoveries and precisions. The applicability of the proposed method was illustrated in the determination of norfloxacin in human urine sample without sample pre-treatment.

ARVAND M., BOZORGZADEH E., SHARIATI SH., ZANJANCHI M.A. — 2014 г.

A new dispersive liquid–liquid microextraction (DLLME) method for preconcentration of trace quantities of Fe(II) and Cu(II) followed by their spectrophotometric determination has been developed. For the extraction, an appropriate mixture of ethanol (the disperser solvent) and carbon tetrachloride (the extraction solvent) was injected rapidly into the water sample containing Fe(II) and Cu(II) after formation of complexes with diethyldithiocarbamate. Mean centering (MC) of ratio spectra has been used for simultaneous determination of Fe(II) and Cu(II). Linear range of the method is 1.0–100 ng/mL for Fe(II) and 0.3–100 ng/mL for Cu(II), the detection limit is 0.53 and 0.14 ng/mL Cu(II), resp. The interference effect of some anions and cations is reported. The method was applied to the determination of Fe(II) and Cu(II) in well water samples.

ELGORASHE RAFEA E. E., IDRIS ABUBAKR M. — 2014 г.

Sequential injection chromatography (SIC) is based on a stopped-flow approach utilizing micro-scale low-pressure pump and selection valves coupled with micro-scale fiber optic spectrometric devices. In the current communication, a new method for the estimation of furosemide (FSD) and amiloride (AMD) in tablet formulation exploiting SIC is reported. The method was reverse-phase liquid chromatographic-based. The separation was carried out onto C18 monolithic column (4.6 ? 50 mm) with a mobile phase composition of 25 mM phosphate buffer (pH 4.0)–acetonitrile (65 : 35, v/v). Other conditions were: sample volume 30 L, flow rate 30 L/sec, UV detection at 283 nm. The SIC method is eco-friendly and cost-effective. The volume of consumed mobile phase was 3.25 mL. The sample frequency was 24 samples/h. The assay also exhibited linear dynamic ranges of 10 100 g/mL for FSD and 5 80 g/mL for AMD. Acceptable intra- and inter-day precision (the RSD values were less than 2.2%) and accuracy (the recovery range was 97.5–98.4%) were obtained for concentrations over the range of the standard curves. The procedure was established for the purpose of quality control at a pharmaceutical laboratory.

ENSAFI ALI A., MAHSA LOTFI — 2014 г.

A stable electroactive thin film of poly(4,5-dihydroxy-1,3-benzenedisulfonic acid) was electrochemically deposited at the surface of multiwall carbon nanotubes-glassy carbon electrode. The electrocatalytic oxidation of hydrazine has been studied at the surface of the modified electrode using cyclic voltammetry, chronoamperometry and linear sweep voltammetry as diagnostic techniques. The modified electrode exhibits good electrocatalytic activity for the oxidation of hydrazine with a good sensitivity. Linear calibration range was in the wide concentration range of 10 3540 M hydrazine with a detection limit of 1.8 M and a sensitivity of 85.3 nA M. A Tafel plot, derived from voltammograms, indicated a one-electron transfer process to be the rate-limiting step and the overall number of electrons involved in the catalytic oxidation of hydrazine was found to be four. The influences of potentially interfering substances were studied. The diffusion coefficient of hydrazine was also evaluated. Finally, the proposed modified electrode was used for the determination of hydrazine in spiked water samples.

BEHPOUR M., GHOREISHI S.M., MESHKI M., NAEMI H. — 2014 г.

A carbon paste electrode, modified with N,N-bis-(2-hydroxy-1-naphthalidene)ethylenediamine and multi-walled carbon nanotubes (HNED–MWCNPE), was used for the determination of acetaminophen (ACOP) and propranolol (PP). Cyclic voltammetry (CV), chronocoulometry, chronoamperometry and differential pulse voltammetry (DPV) techniques were employed to study electro-oxidation of ACOP. The results revealed that the modified electrode showed an electrocatalytic activity toward the anodic oxidation of acetaminophen by a marked enhancement in the current response in buffered solution at pH 8.0. Some kinetic parameters such as the electron transfer coefficient ( ) were also determined for the ACOP oxidation. The linear concentration range of 1 ? 10-3 1 ? 10-6 M with a detection limit of 4.6 ? 10-8 M (n = 16) for ACOP was obtained using DPV (pH 8.0). The modified electrode shows good sensitivity, selectivity and stability. The prepared electrode was also applied for the determination of ACOP in human blood serum.

AYSEGUL GOLCU, BURCU DOGAN-TOPAL, DERYA TARINC, OZKAN SIBEL A. — 2014 г.

A voltammetric study of the oxidation of Ceftazidime (CEFT) has been carried out at the glassy carbon electrode by cyclic, differential pulse (DPV) and square wave (SWV) voltammetry. The oxidation of CEFT was irreversible and exhibited diffusion controlled process depending on pH. The oxidation mechanism was proposed and discussed. According to the linear relationship between the peak current and concentration, DPV and SWV voltammetric methods for CEFT assay in pharmaceutical dosage forms and human urine were developed. For analytical purposes, a well resolved diffusion controlled voltammetric peak was obtained in 0.1 M H2SO4 at 1.00 and 1.02 V for differential pulse and square wave voltammetric techniques, respectively. The linear response was obtained within the range of 4 ? 10-6 8 ? 10-5 M with a detection limit of 6 ? 10-7 M for differential pulse and 4 ? 10-6 2 ? 10-4 M with a detection limit of 1 ? 10-6 M for square wave voltammetric technique. The determination of CEFT in 0.1 M H2SO4 was possible over the 2 ? 10-6 1 ? 10-4 M range in urine sample for both techniques. The standard addition method was used for the recovery studies.

ARTHOBA NAIK Y., BASAVANNA S., CHETHANA B.K. — 2014 г.

The electrochemical behaviour of lawsone at glassy carbon electrode (GCE) was investigated by using cyclic and differential pulse anodic stripping voltammetric (DPASV) techniques. Cyclic voltammetry was used to study the influence of pH on the peak current and peak potential. The Mcllavnies buffer of pH 3.0 was selected as a suitable analytical medium in which lawsone exhibited sensitive diffusion controlled redox peaks (vs. Ag/AgCl). The peak current varied linearly with lawsone concentration in the range between 0.60 and 1.40 M with a detection limit of 6 nM. The applicability of the proposed method was illustrated by the determination of lawsone present in real samples. A mean recovery of lawsone in the leaf of Lawsonia inermis was 99.5% with a relative standard deviation of 1.15%.

HAMIDI A.S., KAZEMI S.Y., LAKOURAJ M.M., ZOLGHARNEIN J. — 2014 г.

The performance of a new membrane sensor based on polyvinyl chloride (PVC) for Tl(I) assay was investigated using the statistical design as an optimization strategy. The Plackett–Burman and Box–Behnken designs, respectively, were utilized to find out the influencing variables and optimization of conditions. In order to evaluate the relationship between the responses of electrode (slope) and significant variables along with their interactions, a mathematical model was presented. The interactions between significant variables were intuitively illustrated according to the response surface plots. Apart from that, the optimum conditions as a result of response surface methodology for both membrane ingredients and measuring conditions such as pH, PVC, internal solution concentration, calix[6]arene, 2-nitrophenyloctylether, potassium tetrakis-(p-chlorophenyl)borate and time conditioning, respectively, were found to be: 6, 0.028 g, 0.001 M, 0.0035 g, 0.065 g, 0.0015 g and 20 h. The optimized sensor exhibits a Nernstian response for thallium(I) over a wide linear range from 2.0 ? 10-6 to 2.0 ? 10-2 M and the slope of 57.9 ± 0.1 mV/decade of the activity and limit of detection (LOD) 1.9 ? 10-6 M. The relative standard deviations (RSD) for six replicates of the measurement at 1 ? 10-5 and 1 ? 10-4 M of Tl(I) were 2.7 and 3.0%, respectively. The favorable results were given through the direct determination of Tl(I) in spiked wastewater and artificial spiked urine sample with Tl(I). The electrode was also successfully applied to the titration of a Tl(I) solution with KI.

MARUTOIU C., SORAN M.L., STAN M. — 2014 г.

Three sample preparation methods (wet grinding followed by centrifugation, ultrasonic-assisted extraction and microwave-assisted solvent extraction) for extracting ascorbic acid (AA) from parsley, dill and celery were evaluated. AA was extracted into 8% aqueous solutions of acetic acid, metaphosphoric acid and trichloroacetic acid, respectively. An efficient and precise high-performance liquid chromatography method was used for detecting AA. The best extraction technique was ultrasonic-assisted extraction, and acetic acid was the best extractant. A new and original pulse microwave-extraction procedure for AA extraction was also developed. Ascorbate from the plant extracts obtained was quantified and the linearity, precision, recovery, limit of detection (LOD) and limit of quantification (LOQ) were studied. LOD and LOQ were 0.2 and 0.22 mg/L for the established method, respectively. The mean recovery ranged from 90.7 to 102.3% with higher variation in the case of celery. Parsley contains the highest amount of ascorbic acid (264 mg AA/100 g of fresh plant), followed by dill (121 mg AA/100 g of fresh plant), and celery (103 mg AA/100 g of fresh plant).

KOSTOVA D. — 2014 г.

The optimum conditions for extraction of microquantities of chromium(VI) as an ion-association complex with blue tetrazolium chloride (BTC) and tetranitrotetrazolium blue chloride (TNBT) has been determined. The extracted species was a 1 : 2 of the BTC and TNBT cation and the chlorochromate anion. Beers law was obeyed in the range of 0.04 0.8 g/mL Cr(VI) for BTC and 0.1 1.6 g/mL Cr(VI) for TNBT. The molar absorptivities were = 7.77 ? 104 L/(mol cm) (for BTC) and = 2.04 ? 104 L/(mol cm) (for TNBT). Sandells sensitivity of the systems were found to be 6.69 ? 10-4 g/cm2 (for BTC) and 2.55 ? 10-3 g/cm2 (for TNBT). Limit of detection (LOD) is 8.55 ng/mL and limit of quantitation (LOQ) is 0.028 g/mL Cr(VI) for BTC. For TNBT, LOD is 0.031 g/mL and LOQ is 0.103 g/mL. The characteristic values for the extraction equilibrium and the equilibrium in the aqueous phase have been determined. A sensitive method for determination of trace of chromium(VI) in plants has been developed.

AGRAHARI S.K., KUMAR S.D., SRIVASTAVA A.K. — 2014 г.

Development of a composite multiwalled carbon nanotube (MWNT) polyvinyl chloride (PVC) with benzo-15-crown-5 (B15C5) as ionophore sensor responsive to uranyl ion is described. The composite MWNT-PVC membrane containing the active ingredients was casted on the surface of a graphite rod. The sensor incorporates B15C5 as electroactive material, ortho-nitrophenyl octyl ether (o-NPOE) as a plasticizer and sodium tetraphenyl borate (NaTPB) as an ion discriminator. The sensor displays a rapid and linear response over the concentration range of 1 ? 10-1 to 1 ? 10-7 M UO with a slope of 29.9 ± 0.4 mV per decade. The detection limit of this electrode was found to be 5.4 ? 10-8 M and the working pH range is from 2.5 to 4.5. Interference from many inorganic cations viz. Na+, K+, Sr2+, Zn2+ and Fe3+ is negligible for the sensor. Application to the determination of uranium in ores and effluent samples gives results with good correlation which are comparable with data obtained by inductively coupled plasma atomic emission spectrometry. The electrode has been characterized using surface techniques.

MEHDI HOSSEINI, NASSER DALALI, SARA MOGHADDASIFAR — 2014 г.

A novel homogeneous liquid–liquid microextraction technique based on use of ionic liquids (ILs), termed in situ solvent formation microextraction (ISFME) is developed for separation/preconcentration of Co(II) ions. In this method, small amount of sodium hexafluorophosphate (NaPF6, as an ion-pairing agent) was added to the sample solution containing very small amount of 1-hexyl-3-methylimidazolium tetrafluoroborate ([Hmim][BF4], as hydrophilic IL). A cloudy solution was formed as a result of formation of fine droplets of 1-hexyl-3-methylimidazolium hexafluorophosphate [Hmim][PF6]. After centrifuging, the fine droplets of the extractant phase settled to the bottom of the conical-bottom glass centrifuge tube. ISFME is a simple and rapid method for extraction and preconcentration of cobalt ions from water samples that can be applied for the sample solutions containing very high concentrations of salt. Furthermore, this technique is much safer in comparison with the organic solvent extraction. Reliability of the introduced methodology was evaluated by analyzing water reference material. ISFME was successfully applied to determining cobalt(II) in real water samples. Schiff base ligand, 3,3-(1E,1E)-(propane-1,2-diylbis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene)bis(4-bromophenol) (L) was chosen as a complexing agent. Analysis was carried out using atomic absorption spectrometry. Type and amount of IL, pH and the other parameters were optimized. Under the optimum conditions, the limit of detection (LOD) was 0.06 ng/mL and the relative standard deviation (RSD) was 1.8% for 10 ng/mL cobalt.

CHENMING XUE, OZGUL BIREL, SECIL CELIK-ERBAS, VEDIA NUKET TIRTOM — 2014 г.

Responses of organic uorophore, perylenediimide derivative N,N-di[3-[2-(3-thienyl)ethyl]phenyl]perylene-3,4,9,10-bis-(dicarboxyimide) (PDI1) was investigated in polymer matrix of polyvinyl chloride (PVC) by emission spectrometry. Its response to Fe(III) ions was evaluated in terms of the effect of pH. The properties of time dependent response, reversibility, limit of detection, linear concentration range for the metal ion and repeatability characteristics of the sensing element also have been studied. The offered sensor exhibited remarkable uorescence intensity quenching at pH 6.0 in the concentration range of 1 ? 10-6 to 2.5 ? 10-3 M Fe(III) ions. The reproducibility of the sensor membrane was investigated by alternately changing the solution between 1 ? 10-4 M Fe(III) in Na2HPO4 (4 ? 10-2 M) and NaH2PO4 buffer (2 ? 10-3 M).

FARNOUSH FARIDBOD, HASSAN ALI ZAMANI — 2014 г.

Solution studies showed a selective interaction between the new synthesized ionophore, 2-[(thiophen-2-yl)methyleneamino]isoindoline-1,3-dione (TMID) and Fe(III) ion. Therefore, TMID was used as an iron selective ion-carrier in a plasticized liquid membrane sensor. The linear response range of the proposed electrode was 1.0 ? 10-6 1.0 ? 10-2 M. The Nernstian slope of 20.1 ± 0.3 mV/decade, and a detection limit of 4.6 ? 10-7 M was obtained. The sensor could be used in the pH range of 2.3–4.8, and the response time was about 10 s. The lifetime of the electrode was at least 7 weeks. The sensor accuracy was investigated in two ways: (i) with the potentiometric titration of a Fe3+ solution with EDTA and (ii) with Fe(III) monitoring in some cationic mixtures. Finally, the newly fabricated electrode was effectively applied as an indicator electrode for the direct Fe3+ determination in real samples.

HASSAN J. — 2014 г.

The application of miniaturized homogeneous liquid–liquid extraction (MHLLE) technique as a simple, inexpensive, quick and efficiency clean up method has been evaluated for determination of diazinon, alachlor, chlorpyrifos and butachlor in cow milk samples. Methanol was used as extraction solvent for the extraction of analytes from cow milk samples and then, methanol phase was extracted and cleaned up by MHLLE method. In this method, butyl acetate was added to methanol phase and after addition of water, butyl acetate was separated from methanol phase and injected to the GC/TSD instrument. The concentration ranges were from 1.0–1000.0 ng/mL for diazinon and chlorpyrifos and from 5.0–1000.0 ng/mL for alachlor and butachlor. The limits of detection were 0.4, 1.6, 0.3 and 1.4 ng/mL for diazinon, alachlor, chlorpyrifos and butachlor, respectively. Finally, the extraction method was successfully applied to the analysis of raw cow milk samples.

ATHANASELIS S., KARAMPELA S., PAPOUTSIS I., PISTOS C., SPILIOPOULOU CH., VARDAKOU I. — 2014 г.

The potential deleterious effects of extractables/leachables in pharmaceutical products and the need to preserve product safety throughout its shelf life have led the three major pharmacopoeias (USP, EP, JP) to require extractable and toxicity testing of container/closure systems. To that, a HPLC/UV method was developed and validated for the detection of zinc dibutyl dithiocarbamate (ZDBC) as potential extractable from pharmaceutical container closure system of eye drops solutions. The method consists of direct extraction of the analyte with chloroform; the lower layer was evaporated to dryness and further reconstituted with acetonitrile. The chromatographic separation was performed on a Nova-Pak C18 column using as mobile phase a mixture of acetonitrile:water. Calibration curves were linear and relative standard deviation was sufficient. Detection limit of ZDBC was found to be 0.015 g/mL. The HPLC method was further applied in seven currently marketed eye drops solutions, confirming its applicability for monitoring dithiocarbamates migration from container closure systems into the eye drops solutions.