Fast analysis of thiocyanate by ion-pair chromatography with direct conductivity detection on a monolithic column

Fast analysis of thiocyanate by ion-pair chromatography using a silica-based monolithic column and direct conductivity detection was carried out. Chromatographic separation was performed on a Chromolith Speed ROD RP-18e using tetrabutylammonium hydroxide （TBA）-phthalic acid-acetonitrile as eluent. The effects of eluent concentration, eluent pH value, column temperature and flow rate on retention time of thiocyanate were investigated. The optimized chromatographic conditions for the determination of thiocyanate were as follows： 0.25 mmol/L TBA-0.18 mmol/L phthalate-7% acetonitrile （pH 5.5） as eluent, column temperature of 30 ℃, and flow rate of 6.0 mL/min. Retention time of thiocyanate was less than 1 min under the conditions. Common anions （Cl^-, NO3 , SO42 and I^- ） did not interfere with the determination of thiocyanate. Detection limit （S/N = 3） of thiocyanate was 0.96 mg/L. Calibration graph between peak area and the concentration of thiocyanate was linear in the range of 2.0- 100.0 mg/L. Relative standard deviation （RSD） of chromatographic peak area was 1.4% （n = 5）. This method has been applied to the determination of thiocyanate in ionic liquids. Recoveries of thiocyanate after spiking were 100.5%.     

Determination of chlorogenic acid by flow injection irreversible biamperometry

A flow injection irreversible biamperometric method for the determination of chlorogenic acid is described.The proposedmethod is based on the electrochemical oxidation of chlorogenic acid at pretreated platinum electrode and the reduction ofpermanganate at another electrode to form an irreversible biamperometric detection system.Under the external potential difference(△E)of 0 V,in the 0.05 mol/L sulfuric acid,chlorogenic acid can be determined over the range 0.8-120 mg/L with a samplemeasurement frequency of 80 samples/h.The detection limit is 0.18 mg/L.The proposed method exhibits the satisfactoryreproducibility with a relative standard derivation(R.S.D.)of 2.21%for 19 successive determinations of 40 mg/L.     

Determination of phenolic whitening agents in cosmetics by micellar electrokinetic capillary chromatography with amperometric detection

A sensitive method for simultaneous determination of six phenolic whitening agents,including arbutin, phenol,resorcinol,hydroquinone,kojic acid,and salicylic acid in cosmetics has been developed using micellar electrokinetic capillary chromatography with amperometric detection（MECC-AD）.Effects of several factors,such as the pH value and concentration of running buffer,potential applied to the working electrode,separation voltage,and injection time were investigated to obtain optimum conditions for separation and detection.With a 75 cm long fused-silica capillary tube,well-defined separation of six phenolic compounds was achieved in 10mmol/L SDS/40 mmol/L H₃BO₃-Na₂B₄O₇ running buffer（pH 9.0）.Good linear relationship was obtained for each analyte over three orders of magnitude with correlation coefficients（r2） between 0.9985 and 0.9994,and the detection limit（S/N=3） ranged from 0.04μg/mL to 0.45μg/mL The proposed method has been successfully applied for the determination of phenolic whitening agents in real cosmetic samples with satisfactory results,providing an alternative monitoring method for cosmetics safety regulation.     

Chelatometric dispersive liquid-liquid microextraction followed by capillary electrophoresis for the analysis of total and water soluble copper in Rhizoma coptidis

A new method for the analysis of copper and its speciation in Rhizoma coptidis was proposed using chelatometric dispersive liquid-liquid microextraction(cDLLME) followed by capillary electrophoresis. Dithizone was used as a chelating agent for extraction and carbon tetrachloride and ethanol were used as extraction and dispersive solvent,respectively.The calibration curve was linear in the range of 0.5- 20.0μg/mL with a correlation coefficient of 0.9990(n = 6) and the average recovery was in the range of 88.26%-94.44%.The method was successfully used to determine the total and water soluble copper in Rhizoma coptidis herbal medicine.The results suggested that it would be reasonable to setting the criterion of heavy metals in an herbal medicine according to the dosage forms.     

Near-infrared diffuse reflectance spectroscopy with sample spots and chemometrics for fast determination of bovine serum albumin in micro-volume samples

Near-infrared diffuse reflectance spectroscopy(NIRDRS) has attracted more and more attention in analyzing the components in samples with complex matrices.However,to apply this technique to micro-analysis,there are still some obstacles to overcome such as the low sensitivity and spectral overlapping associated with this approach.A method for fast determination of bovine serum albumin (BSA) in micro-volume samples was studied using NIRDRS with sample spots and chemometric techniques.10μL of sample spotted on a filter paper substrate was used for the spectral measurements. Quantitative analysis was obtained by partial least squares(PLS) regression with signal processing and variable selection.The results show that the correlation coefficient(R) between the predicted and the reference concentration is 0.9897 and the recoveries are in the range of 87.4%-114.4%for the validation samples in the concentration range of 0.61-8.10 mg/mL.These results suggest that the method has the potential to quickly measure proteins in micro-volume solutions.     

A new method for determination of antithrombotic activity of egg white protein hydrolysate by microplate reader

A new method for the determination of antithrombotic activity of egg white protein hydrolysate(EWPH)was developed using amicroplate reader.Reaction was carried out at 37℃ and pH 7.2 with fibrinogen concentration 0.1%.Microplate reading wasconducted at 405 nm.Inhibition rate of EWPH on thrombin activity showed linearity(R~2=0.9971),when the inhibition rate was inthe range of 10-90%.The lower limit of detection(LLD,at 99.7%probability)and the biological limit of detection(BLD,at 99.7%probability)of the method were 10.643 and 40 mg/mL,respectively.The repeatability standard deviation(R.S.D.)was 1.08%.Thestandard deviation of the method was 0.027 AT-U.     

Synthesis,characterization of palygorskite supported zero-valent iron and its application for methylene blue adsorption

In this work, natural palygorskite impregnated with zero-valent iron (ZVI) was prepared and characterized. The combination of ZVI particles on surface of fibrous palygorskite can help to overcome the disadvantage of ultra-fine powders which may have strong tendency to agglomerate into larger particles, resulting in an adverse effect on both effective surface area and catalyst performance. There is a significant increase of methylene blue (MB) decolourized efficiency on acid treated palygorskite with ZVI grafted, within 5 min, the concentration of MB in the solution was decreased from 94 mg/L to around 20 mg/L and the equilibration was reached at about 30–60 min with only around 10 mg/L MB remained in solution. Changes in the surface and structure of prepared materials were characterized using X-ray diffraction (XRD), infrared (IR) spectroscopy, surface analysing and scanning electron microscopy (SEM) with element analysis and mapping. Comparing with zero-valent iron and palygorskite, the presence of zero-valent iron reactive species on the palygorskite surface strongly increases the decolourization capacity for methylene blue, and it is significant for providing novel modified clay catalyst materials for the removal of organic contaminants from waste water.     

Multiwavelength spectrophotometric determination of acidity constants of 1-（2-thiazolylazo）-2-naphthol in methanol-water mixtures

The acid-base properties of 1-(2-thiazolylazo)-2-naphthol (TAN) in mixtures of methanol-water at 25℃and an ionic strength of 0.1 mol/L are studied by a multi-wavelength spectrophotometric method.The acidity constants of all related equilibria are estimated using the whole spectral fitting of the collected data to an established factor analysis model DATAN program was used for determination of acidity constants.The corresponding pK_a values in methanol-water mixtures were determined.There is a linear relationship between acidity constants and the mole fraction of methanol in the solvent mixtures.     

The Routes of Administration of Amikacin as Consideration in Reptile Therapy

The research was conducted to know the effect of amikacin administrations to the concentration of drug in reptile. The 16 sanca batik snakes (Broghammerus reticulatus) were adapted then divided into four groups of which each was administered5 mg · kg^–1 body weight of amikacin by posterior and anterior intravenous and intramuscular injection, respectively. The blood collection was done by cardio-puncture to each group at minute 1, 60 and 24, 48 h after drug injection and the drug concentration was analysed by High Performance Liquid Chromatography. The result showed that the drug by i.v. or i.m. administration routes (t1,t48) from posterior region had higher concentrations (81.90 ± 23.1) mg · mL^–1, (17.23 ± 5.29) mg · mL^–1) compared to the anterior injection (P < 0.01). The other concentration comparisons between regions resulted in no significant difference.     

Sensitive lactate determination based on acclimated mixed bacteria and palygorskite co-modified oxygen electrode

A sensitive bacteria biosensor was prepared for the detection of trace lactate. The sensitive bioelement, Lactobacillus bulgaricus and Streptococcus thermophilus mixed cultrue, and palygorskite, a perfect matrix for bacteria, was co-immobilized on the surface of oxygen electrode. The biosensor possesses fine selective specificity, good sensitivity and longer operational life time, which were due to the mutual help relationship of symbiotic bacteria and 240 days acclimation with lactate as the carbon source. Hydrodynamic amperometry, an advanced electrochemical method, is suitable for on-line monitoring the concentration change of dissolved oxygen that is closely accompanied with the metabolism of lactate. Electrochemical data show that the current is very sensitive to the changes of the concentration of lactate. The response current was linear with lactic acid concentration in the range from 0 to 300 μmol L^? 1, where the response time is no more than 240 s (R = 0.9952), and the sensitivity was 1.87 mA mol^? 1 L. Experiments show the biosensor is also very useful for long time on-line monitoring of lactate, such as fermentation progress.     

Study on the effects of cefotaxime on intracellular Ca^2＋ in human peripheral lymphocytes by fluoremetry

Characteristic of Fura-2-Ca~(2 )interaction was studied based on the fluorescence technique.The apparent dissociation constants(K_d)of the Fura-2-Ca~(2 )complex were determined at different temperature.The effect of cefotaxime(CEFA)on intracellular Ca~(2 )concentration([Ca~(2 )]_i)was discussed by using a ratiometric fluorescence dye Fura-2 as a probe.The basal[Ca~(2 )]_i in resting humanperipheral lymphocytes was 100 7 nmol/L but after treatment with cefotaxime,the changes of[Ca~(2 )]_i were observed in differentconditions.In the concentration range of 1-30 μmol/L of cefotaxime[Ca~(2 )]_i increased,as a result of releasing intracellular Ca2 stores.Higher concentration of cefotaxime(50-500 μmol/L)stimulated to decrease of[Ca~(2 )]_i.     

TiO2/polyaniline composites： An efficient photocatalyst for the degradation of methylene blue under natural light

Polyaniline (PAn) sensitized nanocrystalline TiO_2 composites (TiO_2/PAn) were successfully prepared and used as an efficient photocatalyst for the degradation of dye methylene blue (MB).The results showed that PAn was able to sensitize TiO_2 efficiently and the composite photocatalyst could be activated by absorbing both the ultraviolet and visible light (λ:190～800nm),whereas pure TiO_2 absorbed ultraviolet light only (λ<380nm).Under the irradiation of natural light,MB could be degraded more efficiently on the TiO_2/PAn composites than on the TiO_2.Furthermore,it could be easily separated from the solution by simple sedimentation.     

Simultaneous determination of seven prohibited substances in cosmetic products by liquid chromatography-tandem mass spectrometry

In this paper,we developed and validated a simple,sensitive,and selective high-performance liquid chromatography-tandem mass spectrometry(HPLC-MS/MS) method to identify and measure the following prohibited substances that may be found in cosmetic products:minoxidil,hydrocortisone, spironolactone,estrone,canrenone,triamcinolone acetonide and progesterone.Chromatographic separation was performed on a Waters Symmetry C18(100 mm×2.1 mm,3.5μm particle size) with a gradient elution system composed of 0.2%(v/v) formic acid aqueous solution and methanol containing 0.2%(v/v) formic acid at a flow rate of 0.3 mL/min.The substances were detected using a triple quadrupole mass spectrometer in the multiple reaction monitoring mode with an electrospray ionization source.All of the calibration curves showed good linearity(r > 0.999) within the tested concentration ranges.The limit of detection was <25 pg.The relative standard deviations for intraday precision for each of the prohibited substances were <3.5%at two concentration levels(2μg/g,10μg/g). The relative recovery rate for each of the prohibited substances ranged from 91.8%to 111%at three concentration levels(0.1μg/g,2μg/g,10μg/g),including the limit of quantification.In conclusion,we have developed and validated a method that can identify seven prohibited substances in cosmetic products.     

A structure-based analysis of the vibrational spectra of nitrosyl ligands in transition-metal coordination complexes and clusters

The vibrational spectra of nitrogen monoxide or nitric oxide (NO) bonded to one or to several transition-metal (M) atom(s) in coordination and cluster compounds are analyzed in relation to the various types of such structures identified by diffraction methods. These structures are classified in: (a) terminal (linear and bent) nitrosyls, [M(σ-NO)] or [M(NO)]; (b) twofold nitrosyl bridges, [M₂(μ₂-NO)]; (c) threefold nitrosyl bridges, [M₃(μ₃-NO)]; (d) σ/π-dihaptonitrosyls or “side-on” nitrosyls; and (e) isonitrosyls (oxygen-bonded nitrosyls).Typical ranges for the values of internuclear N–O and M–N bond-distances and M–N–O bond-angles for linear nitrosyls are: 1.14–1.20 Å/1.60–1.90 Å/180–160° and for bent nitrosyls are 1.16–1.22 Å/1.80–2.00 Å/140–110°. The [M₂(μ₂-NO)] bridges have been divided into those that contain one or several metal–metal bonds and those without a formal metal/metal bond (M?M). Typical ranges for the M–M, N–O, M–N bond distances and M–N–M bond angles for the normal twofold NO bridges are: 2.30–3.00 Å/1.18–1.22 Å/1.80–2.00 Å/90–70°, whereas for the analogous ranges of the long twofold NO bridges these are 3.10–3.40 Å/1.20–1.24 Å/1.90–2.10 Å/130–110°. In both situations the N–O vector is approximately at right angle to the M–M (or M?M) vector within the experimental error; i.e. the NO group is symmetrical bonded to the two metal atoms. In contrast the threefold NO bridges can be symmetrically or unsymmetrically bonded to an M₃-plane of a cluster compound. Characteristic values for the N–O and M–N bond-distances of these NO bridges are: 1.24–1.28 Å/1.80–1.90 Å, respectively. As few dihaptonitrosyl and isonitrosyl complexes are known, the structural features of these are discussed on an individual basis.The very extensive vibrational spectroscopy literature considered gives emphasis to the data from linearly bonded NO ligands in stable closed-shell metal complexes; i.e. those which are consistent with the “effective atomic number (EAN)” or “18-electron” rule. In the paucity of enough vibrational spectroscopic data from complexes with only nitrosyl ligands, it turned out to be very advantageous to use wavenumbers from the spectra of uncharged and saturated nitrosyl/carbonyl metal complexes as references, because the presence of a carbonyl ligand was found to be neutral in its effect on the ν(NO)-values. The wide wavenumber range found for the ν(NO) values of linear MNO complexes are then presented in terms of the estimated effects of net ionic charges, or of electron-withdrawing or electron-donating ligands bonded to the same metal atom. Using this approach we have found that: (a) the effect for a unit positive charge is [plus 100 cm^?1] whereas for a unit negative charge it is [minus 145 cm^?1]. (b) For electron-withdrawing co-ligands the estimated effects are: terminal CN [plus 50 cm^?1]; terminal halogens [plus 30 cm^?1]; bridging or quasi-bridging halogens [plus 15 cm^?1]. (c) For electro donating co-ligands they are: PF₃ [plus 10 cm^?1]; P(OPh)₃ [?30 cm^?1]; P(OR)₃ (R = alkyl group) [?40 cm^?1]; PPh₃ [?55 cm^?1]; PR₃ (R = alkyl group) [?70 cm^?1]; and η⁵-C₅H₅ [?60 cm^?1]; η⁵-C₅H₄Me [?70 cm^?1]; η⁵-C₅Me₅ [?80 cm^?1]. These values were mostly derived from the spectra of nitrosyl complexes that have been corrected for the presence of only a single electronically-active co-ligand. After making allowance for ionic charges or strongly-perturbing ligands on the same metal atom, the adjusted ‘neutral-co-ligand’ ν(NO)*-values (in cm^?1) are for linear nitrosyl complexes with transition metals of Period 4 of the Periodic Table, i.e. those with atomic orbitals (…4s3d4p): [ca. 1750, Cr(NO)]; [1775,Mn(NO)]; [1796,Fe(NO)]; [1817,Co(NO)]; [ca. 1840, Ni(NO)]. Period 5 (…5s4d5p): [1730 Mo(NO)]; [—, Tc(NO)]; [1745,Ru(NO)]; [1790,Rh(NO)]; [ca. 1845, Pd(NO)]. Period 6 (…6s4f5d6p), [1720,W(NO)]; [1730,Re(NO)]; [1738,Os(NO)]; [1760,Ir(NO)]; [—, Pt] respectively. Environmental differences to these values, e.g. data taken in polar solutions or in the crystalline state, can cause ν(NO)* variations (mostly reductions) of up to ca. 30 cm^?1.Three spectroscopic criteria are used to distinguish between linear and bent NO groups. These are: (i) the values of ν(¹⁴NO) themselves, and (ii) the isotopic band shift – (IBS) – parameter which is defined as [ν(¹⁴NO)–ν(¹⁵NO)], and, (iii) the isotopic band ratio – (IBR) – given by [ν(¹⁵NO/ν¹⁴NO)]. The former is illustrated with the ν(¹⁴NO)-data from trigonal bipyramidal (TBP) and tetragonal pyramidal (TP) structures of [M(NO(L)₄] complexes (where M = Fe, Co, Ru, Rh, Os, Ir and L = ligand). These values indicate that linear (180–170°) and strongly bent (130–120°) NO groups in these compounds absorb over the 1862–1690 cm^?1 and 1720–1525 cm^?1-regions, respectively. As was explicitly demonstrated for the linear nitrosyls, these extensive regions reflect the presence in different complexes of a very wide range of co-ligands or ionic charges associated with the metal atom of the nitrosyl group. A plot of the IBS parameter against M–N–O bond-angle for compounds with general formulae [M(NO)(L)_y] (y = 4, 5, 6) reveals that the IBS-values are clustered between 45 and 30 cm^?1 or between 37 and 25 cm^?1 for linear or bent NO groups, respectively. A plot of IBR shows a less well defined pattern. Overall it is suggested that bent nitrosyls absorb ca. 60–100 cm^?1 below, and have smaller co-ligand band-shifts, than their linear counterparts.Spectroscopic ν(NO) data of the bridging or other types of NO ligands are comparatively few and therefore it has not been possible to give other than general ranges for ‘neutral co-ligand’ values. Moreover the bridging species data often depend on corrections for the effects of electronically-active co-ligands such as cyclopentadienyl-like groups. The derived neutral co-ligand estimates, ν(NO)*, are: (a) twofold bridged nitrosyls with a metal–metal bond order of one, or greater than one, absorb at ca. 1610–1490 cm^?1; (b) twofold bridged nitrosyl ligands with a longer non-bonding M?M distance, ca. 1520–1490 cm^?1; (c) threefold bridged nitrosyls, ca. 1470–1410 cm^?1; (d) σ/π dihaptonitrosyl, [M(η²-NO)], where M = Cr, Mn and Ni; ca. 1490–1440 cm^?1. Isonitrosyls, from few examples, appear to absorb below ca. 1100 cm^?1.To be published DFT calculations of the infrared and Raman spectra of complexes with formulae [M(NO)_4?n(CO)_n] (M = Cr, Mn, Fe, Co, Ni, and n = 0, 1, 2, 3, 4, respectively) are used as models for the assignments of the ν(MN) and δ(MNO) bands from more complex metal nitrosyls.     

Determination of neomycin in water samples by high performance anion chromatography with pulsed amperometric detection

A simple, fast and reliable method, using high performance anion chromatography with pulsed amperometric detection, had been developed for the analysis of neomycin in water samples. The elution and separation were carried out with an isocratic mobile phase, containing 10 mmol/L NaOH. The influence of the concentration and pH of the mobile phase on the separation and detection was investigated. A quadruple-potential waveform used for the detection was optimized. The detection limit of neomycin was down to 0.027μg/mL. The linearity of neomycin calibration curve ranged from 0.050 to 0.505μg/mL with correlation coefficient of 0.9997. R.S.D. (n = 11) was 4.0%.     

Utility of oxidation–reduction reaction for the spectrophotometric determination of amlodipine besylate

A simple, rapid, accurate, precise and sensitive spectrophotometric method for the determination of amlodipine besylate (ADB) in bulk sample and in dosage forms is described. The method is based on oxidation of the drug by potassium permanganate in acidic medium and determine the unreacted oxidant by measuring the decrease in absorbance for five different dyes; methylene blue (MB), acid blue 74 (AB), acid red 73 (AR), amaranth dye (AM) and acid orange 7 (AO) at a suitable λ_max 663, 609, 511, 520, and 484 nm, respectively. Regression analysis of Beer's law plots showed good correlation in the concentration ranges 1.0–24, 0.9–22, 1.2–26, 0.9–12.8 and 1.0–14 μg ml^?1, respectively. The apparent molar absorptivity, Sandell sensitivity, detection and quantitation limits were calculated. For more accurate results, Ringbom optimum concentration ranges were 1.2–22.4, 1.1–20, 1.4–24.5, 1.0–12.3 and 1.3–13.2 μg ml^?1, respectively. Statistical treatment of the results reflects that the proposed procedures are precise, accurate and easily applicable for the determination of amlodipine besylate in pure form and in pharmaceutical preparations.     

Chemical composition and larvicidal activity of Algerian Foeniculum vulgare seed essential oil

A laboratory study was conducted to determine the effect of three extraction parameters (soaking time, extraction time and the ratio of solid to liquid) on the yield and chemical composition of Foeniculum vulgare seeds essential oils. The bioactivity of the essential oil extracted for the optimum extraction parameters was assessed against Culex pipiens mosquito. F. vulgare essential oil composition included large amounts of phenylpropanoids. Through an extraction time of 6 h and a ratio solid to liquid of 300 g/L we can get over than 72% of trans-anethol without soaking the seeds. With bioassays, essential oils showed different activities on C. pipiens larvae and pupae. Results show that a concentration at 40 mg/L was sufficient to register 50% mortality for the second instars larvae and this, after 2 h exposition time. Moreover, concentration at 60 mg/L ensured after 4 h exposition time 90% mortality for the fourth instars larvae. However, pupae needed 24 h exposition time to show promising mortalities when using concentration at 200 mg/L. Even if laboratory bioassays are only the first step towards the use of essential oils in practical applications, these substances represent a potential alternative to chemical insecticides in some markets.     

Synthesis of an antimetastatic tetrasaccharide β-D-Gal-(1→4)-β-d-GlcpNAc-(1→6)-α-D-Manp-(1→6)-β-D-Manp-OMe

An antimetastatic tetrasaccharide T₁,β-D-Gal-（1→4）-β-D-GlcpNAc-（1→6）-α-D-Manp-（1→6）-β-D-Manp-OMe,was synthesized with two approaches.The first approach was a conventional method employing thioglycoside and Koenigs-Knorr glycosylation reaction in 24%overall yield.The second one was a novel route through the azidoiodo-glycosylation strategy by using 2-iodo-2-deoxylactosyl azide as the donor in 36%overall yield.     

Multi-walled carbon nanotube as a solid phase extraction adsorbent for analysis of indole-3-butyric acid and 1-naphthylacetic acid in plant samples

In this work,a new sample pretreatment method prior to HPLC separations was developed for the determination of auxins in plant samples.Owing to its large surface area and high adsorption capacity, multi-walled carbon nanotube(MWCNT) was chosen as the adsorbent for the extraction of auxins from plant samples.In this study,two important auxins were selected as model analytes,namely indole-3-butyric acid(IRA) and 1-naphthylacetic acid(NAA).They could be extracted and concentrated due to theirπ-πstacking interactions with MWCNT.Then HPLC-UV was introduced to detect IBA and NAA after sample pretreatment.Factors that may affect the enrichment efficiency were investigated and optimized.Comparative studies showed that MWCNT was superior to C18 for the extraction of the two analytes.Validation experiments showed that the optimized method had good linearity(0.9998 and 0.9960),high recovery(81.4%-85.4%),and low detection limits(0.0030 mg/L and 0.0012 mg/L).The results indicated that the novel method had advantages of convenience,good sensitivity,high efficiency, and it was feasible for the determination of auxins in plant samples.     

Potentiometric determination of diclofenac in pharmaceutical formulation by membrane electrode based on ion associate with base dye

The characteristics,performance and application of membrane electrode based on ion associate of diclofenac with base dye Safranine T are described.The electrode response to diclofenac has the sensitivity of 47±1.0 mV decade~(-1)over the range of 5×10~(-5)to 5×10~(-2)mol/L at pH 6-12,and the detection limit of 3.2×10~(-5)mol/L.The electrode is easy assembled at a relatively low cost has fast response time(2-4 s)and can be used for a period up to 3.5 months without any considerable divergence in potential.The proposed sensor displayed good selectivity for diclofenac in the presence of different substances.It was used to determine diclofenac in pharmaceuticals by means of the standard addition method.