• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    In situ modified screen printed and carbon paste ion selective electrodes for potentiometric determination of naphazoline hydrochloride in its formulation

    2013-12-23 06:14:58GehadMohamedNourElDienEmanFragMarwaElBadryMohamed
    Journal of Pharmaceutical Analysis 2013年5期

    Gehad G. Mohamed, F.A. Nour El-Dien, Eman Y.Z. Frag,Marwa El-Badry Mohamed

    Chemistry Department, Faculty of Science, Cairo University, Gamaa Str., 12613 Giza, Egypt

    1. Introduction

    Naphazoline hydrochloride (NPZ-HCl; Fig.1) is used for the temporary relief of redness of the eye associated with minor irritations such as those caused by colds, pollen related allergies,smog, dust, wind, wearing contact lenses, or swimming. It acts

    Fig.1 The structure of naphazoline hydrochloride.

    Neozoline (Eye/Nasal drops) was produced by Amoun Pharmaceutical Company,El-Obour City,Cairo,Egypt.Every 100 mL contains 50 mg NPZ-HCl.on alpha adrenergic receptors in the arterioles of the conjunctiva to cause vasoconstriction, resulting in decreased conjunctival congestion [1]. Some analytical procedures have been reported for the determination of NPZ in both pure and pharmaceutical preparations including high-performance liquid chromatographic (HPLC) [2],micellar electrokinetic chromatographic [3,4], spectrophotometric[5—9] and potentiometric methods [10,11].

    Potentiometry with ion selective electrodes (ISE) is one of the most important analytical tools capable of determining both organic and inorganic substances in medico-biological practice[12]. There is a constant progress in the number of electrodes capable of selectively identifying various drugs such as carbon paste electrodes (CPEs) [13—18]. Although the CPEs play an important role in the electrochemical analysis, the prepared pastes are soft and non-compactable and have to be packed into a special piston shaped holder with definite shape and size. However,shapes and designs of such electrodes are not suitable for every purpose as in the case of measurements in flowing streams or field monitoring with portable analyzers where the respective detection units need electrodes of special constructions [19].

    Screen printing technology has increasingly been used for the mass production of inexpensive, reproducible and sensitive disposable electrochemical sensors for the determination of trace levels of compounds in pharmaceutical, biomedical, and environmental samples [20].

    In this work, in situ modified screen printed electrodes (SPEs)and CPEs were characterized and optimized with regard to the main experimental parameters affecting the electrode responses,including the nature and content of modifier, pH, response time,temperature and interferences, which were investigated and discussed in detail, and were then applied for the determination of NPZ-HCl in pure form and pharmaceutical preparation (eye drop).

    2. Experimental

    2.1. Materials and reagents

    Analytical grade chemicals and reagents were used.They included NPZ-HCl provided by Misr Company for Pharmaceutical Industry,Egypt. Relative high molecular weight PVC and graphite powder(synthetic 1—2 μm) were supplied by Aldrich. Tricresylphosphate(TCP) was purchased from Alfa-Aesar. Ion pairing agents such as sodium tetraphenylborate (NaTPB) and ammonium reineckate(RN; [NH4(Cr(NH3)2(SCN)4)H2O]) were supplied by Fluka.Phosphotungstic acid (PTA; H3[PW12O40]) and phosphomolybdic acid (PMA; H3[PMo12O40]), were purchased from BDH. Silicotungstic acid (STA, H4SiW12O40) was purchased from Sigma.

    Nitric acid was supplied by Merck. Acetonitrile (AR) was supplied by Aldrich. Acetone, cyclohexanone and tetrahydrofuran were supplied by El-Nasr Company, Egypt.

    2.2. Solutions

    Stock drug solution(1.0×10—2M)was prepared by dissolving the appropriate amount of NPZ-HCl in bidistilled water. Other solutions (1.0×10-3—7.0×10—7M) were prepared by serial dilution from stock solution. NaTPB solution (1.0×10—2M) was prepared by dissolving an accurately weighed amount of the substance in warm water, adjusted to pH 9 by adding sodium hydroxide and made up to the desired volume with water. The resulting solution was standardized potentiometrically against standard thallium acetate solution (1.0×10—2M) [21]. Aqueous solutions of phosphotungstic acid, phosphomolybdic acid, silicotungstic acid and ammonium reineckate were prepared using the analytical grade chemicals and the exact concentrations of these solutions were determined by the appropriate recommended methods [22—24] and lower concentrated solutions were prepared by the appropriate dilutions.

    All solutions must be protected from light by keeping them in dark colored quickfit bottles during the whole work.The bidistilled water was used throughout the experiments.

    2.3. Equipment

    Laboratory potential measurements were performed using a HANNA 211 pH meter. Silver—silver chloride double-junction reference electrode (Metrohm 6.0222.100) in conjugation with different drug ion selective electrodes was used.pH measurements were done using a Jenway 3505 pH meter. A digital multimeter connected to a portable PC and Brand digital buret was used for the measurement of the drug under investigation.

    2.4. Procedures

    2.4.1. Preparation of the working electrodes

    2.4.1.1. Preparation of the SPEs. A manual screen printer was used to produce disposable SPEs. The used substrate which was not affected by the curing temperature or the ink solvent and was easily cut by scissors is a polyvinyl chloride flexible sheet(0.2 mm). The working electrodes were prepared using 6—30 mg ion pairing agent, PVC (8%, w/w), carbon powder (500 mg) and TCP as plasticizer.They were printed using homemade carbon ink and cured at 50°C for 30 min.The prepared electrodes were stored in the refrigerator at 4°C and can be used for measurements directly.

    2.4.1.2. Preparation of the CPEs. The CPEs were prepared by thoroughly mixing various amounts (3—20 mg) of ion pairing agents with carbon powder (250 mg) and TCP (100 μL) in the mortar until homogenization of this mixture was achieved. The resulting paste was then packed firmly into the hole of the electrode body. The surface of the resulting CPE was polished using a filter paper to obtain new working surface.

    2.4.2. Calibration of the sensors

    The calibration of the ISPE and ICPE sensors under investigation was established by immersing the ISPE and ICPE working electrodes in conjunction with Ag—AgCl reference electrode in 50 mL beakers containing known aliquots of 1.0×10-7—1.0×10—2M NPZ-HCl standard solution.The potential reading was plotted against the negative logarithmic value of NPZ-HCl concentrations.The established calibration graph was used for subsequent determination of unknown naphazoline concentrations.

    2.4.3. Effect of foreign compounds on the electrode selectivity

    The potentiometric selectivity coefficients (KP°tA,B) were determined according to IUPAC guidelines using the separate solutions(SSM) and matched potential (MPM) methods [25,26].

    2.4.4. Analytical applications

    The proposed ISPE and ICPE sensors were found to be useful in the potentiometric determination of NPZ-HCl in pure solution and in pharmaceutical preparation by using the calibration, standard addition and potentiometric titration methods. Before the application of this potentiometric method,the neozoline eye drop solution was evaporated gently on water bath till dryness. The residue was then dissolved in methylene chloride depending on the fact that NPZ-HCl is insoluble in methylene chloride while chlorophenramine maleate is soluble in methylene chloride, so the residue was washed twice with methylene chloride to get rid of chlorophenramine maleate and the white residue containing NPZ-HCl was dissolved in a definite volume of distilled water and transferred quantitatively to a 50 mL beaker.

    In the calibration method the electromotive force (EMF) resulting from immersing the prepared electrodes in conjunction with Ag/AgCl as the reference electrode in the prepared solutions was determined,and then the concentration of NPZ-HCl was calculated from the calibration graph of the corresponding electrode.

    In the standard addition method, known increments of NPZHCl standard solution were added to constant volume of samples of different concentrations. The voltage was first measured in the pure sample, then the standard was added and the solutions were mixed well; a second reading was taken. From the change in potential readings for each increment the concentration of the unknown sample was calculated. In the potentiometric titration aliquots of the drug solution containing 0.5—6.0 mg were transferred to a 25 mL beaker.A standard solution of NaTPB was used as a titrant and the titration is monitored using ISPE and ICPE as indicator electrodes conjugated with Ag/AgCl as the reference electrode. The potential values were plotted against the volume of the titrant added and the end points were determined from the Sshaped curves using the first derivative plots. The obtained results were compared with that of British Pharmacopoeia.

    3. Results and discussion

    3.1. Electrode composition

    The electroanalytical performance and electrode potential of an ISE is dependent upon the selective extraction of the target ion which creates the electrochemical phase boundary potential due to thermodynamic equilibria at the sample/electrode interface. Using of a suitable ion pairing agent in the electrode matrix followed by soaking in the drug solution may lead to the formation of an ion exchanger at the electrode surface by adsorption of a counter ion(analyte) from the solution during the measurement itself and can be extracted by the plasticizer into the electrode bulk. Using of a suitable ion pairing agent in the electrode matrix has the advantage of reducing the time required for the electrode preparation where there is no need for ion pair (IP) preparation as well as expansion of the application of ion selective electrodes (ISEs) for the determination of drugs that cannot be precipitated as suitable IPs. Also the same prepared electrodes can be used in preparation of ISEs for many drugs by soaking these electrodes in the solution of the drug under investigation.

    In order to determine the suitable type and content of ion pairing agents (sodium tetraphenylborate, phosphotungstic acid,phosphomolybdic acid, silicotungstic acid and ammonium reineckate), several ISPEs and ICPEs were prepared containing 6—30 and 3—20 mg of ion pairing agents. CPE was soaked in 10—2M of NPZ-HCl solution. It was found that the most suitable ion pairing agent was TPB ion and its most suitable amount was 6 mg that gave the highest slope values of 59.7±0.6 and 59.2±0.2 mV decade-1for ISPE and ICPE, respectively, as shown in Table 1 and Fig.2. On the other hand, the lower concentration gave electrodes with lower slope while the higher content caused oversaturation and unsatisfactory performance due to steric hindrance effects at the interface.

    3.2. Electroanalytical performance characteristics of the sensors

    3.2.1. Calibration plots

    The results presented in Table 2 and Fig.2 showed that the prepared sensors can be successfully applied for the potentiometric determination of the drug under investigation with linear response in the concentration range of 7.0×10-7to 1.0×10—2M with slope values of 59.7±0.6 and 59.2±0.2 mV decade-1for ISPE and ICPE, respectively.

    3.2.2. Effect of pH

    To investigate pH effect on the electrode potential, the potential readings were recorded for two different concentrations (10—4or 10—2M) of NPZ-HCl at different pH values (pH 2—10). The potential changes as a function of pH are shown in Fig.3.This figure indicates that the electrodes response was independent of the pH within the range from 3.1 to 7.9 for ISPE and ICPE with NaTPB ion pairing agent, respectively. At lower pH values the decrease in mV readings may be attributed to the interference from hydronium ion, while at higher pH values the decrease in the mV readings may be due to base precipitates in the test solution and consequently, the concentration of unprotonated species gradually increased. As a result, lower EMF readings were recorded.

    3.2.3. Effect of temperature

    In order to determine the isothermal coefficient of the electrodes(dE°/dt), the standard electrode potentials (E°) were determined from the calibration graphs (the intercepts at p[NPZ]=0)of ISPE and ICPE carried out at different temperatures (10, 20,30, 40, 50 and 60°C) and plotted versus (t-25), where (t) is the temperature of the experiment in degree centigrade and according to the following equation [27]:

    A straight line is obtained and the slope of this line represents the isothermal coefficients of the electrodes which were found to be 0.0022 and 0.0008 V/°C for ISPE and ICPE modified with TPB, respectively. The obtained values of the isothermalcoefficient reveal that the electrodes under investigation had high thermal stability within the used range of temperature. The investigated electrode can be used up to 60°C without noticeable deviation from the Nernstian behavior.

    Table 1 Effect of the nature and content of ion pairing agents on the performance of ISPE and ICPE sensors.

    3.2.4. Interference studies

    As shown in Table 3 the results obtained show no significant interference and this reflects a very high selectivity of the electrodes under investigation toward NPZ-HCl. The results also indicate that there was no serious interference from glucose,sucrose, maltose, fructose, starch and lactose. The inorganic cations did not interfere due to the differences in their ionic size and hence their mobilities, polarities, and permeabilities as compared to those of NPZ+cation.

    3.2.5. Response time

    The response time is an important factor which characterizes ISEs.It can be defined as the time taken by the electrodes to reach steady potential values of 90% of the final equilibrium values, after successive immersions in a series of solutions, each having a 10-fold concentration difference [31—35]. The dynamic response time of the sensors under study was determined for the concentration range from 1.0×10—6to 1.0×10—3M. Fig.4 illustrates a representative plot of the potential changes versus time for electrodes under study. The proposed sensors have very short response time of 4—7 s and 5—8 s for ISPE and ICPE,respectively.

    3.2.6. Effect of soaking time

    As shown in Fig.5, it was found that the optimum soaking time for the ICPE electrode was 15 min and longer soaking time affects negatively on the response of the electrode.This may be due to the leaching of the active ingredients (ion-pairing agent and plasticizer) to the bathing solution [36—38].

    3.2.7. Lifetime

    Fig.2 Effect of NaTPB on the performance of(A)ISPE and(B)ICPE sensors.

    The lifetime of the investigated sensors was studied by periodically constructing the calibration graphs under optimum conditions on different days.For sensors under investigation it was found that ISPE has a life time of 28 days while ICPE has 30 days. A shiny new surface is obtained every time for measurement using ICPE by squeezing out a small portion of the paste and polishing it on a filter paper.After preparation of ISPEs,they were kept at 4°C and directly used for potentiometric measurements.

    3.2.8. Analytical application

    Fig.3 Effect of pH on(A)ISPE and(B)ICPE modified with NaTPB ion pairing agent.

    Table 2 Response characteristics of ISPE and ICPE sensors.

    Table 3 Selectivity coefficients values for ISPE and ICPE sensors.

    The optimized sensors under investigation have been successfully used for the potentiometric determination of NPZ-HCl by using the standard addition, calibration and potentiometric titration methods, and the results are summarized in Table 4. In order to estimate the quality of the results, recovery values were also determined and are presented in the same table. The obtained results in Table 4 using the proposed sensors were in good agreement with those obtained using the official method [39].

    3.3. Method validation

    Electroanalytical method validation is the process used to confirm that the determination procedure employed for a specific test is suitable for its intended use like other analytical methods [40].Accuracy,precision,linearity,specificity, limits of detection(LOD)and quantification(LOQ)were achieved using a standard NPZ-HCl stock solution.

    3.3.1. Accuracy

    Accuracy is an important requirement of electroanalytical methods.It can be defined as the closeness between the true or accepted reference value and the obtained value [40]. The accuracy of the proposed method using in situ SPE and CPE was investigated by the determination of NPZ-HCl in spiked samples prepared from serial concentrations of NPZ-HCl reference standards. The results summarized in Table 5 show high accuracy of the proposed method, as indicated by the percentage recovery values. The statistical analysis of the results using student's t-test and F-test showed no significant differences between them regarding accuracy and precision (Table 4).

    3.3.2. Precision

    Precision is a measure of how close results are to one another.Precision is also expressed as the closeness of agreement between independent test results obtained under stipulated conditions.Precision is usually expressed as standard or relative standard deviations of the replicate analysis[40].Hence the precision of the proposed potentiometric method using the sensors under investigation was measured as percentage relative standard deviation (RSD %). Intra-day and inter-day precisions were assessed using three concentrations and five replicates of each concentration. The relative standard deviations were found to be very small indicating reasonable repeatability and reproducibility of the proposed method as shown in Table 5.

    Fig.4 The dynamic response time of (A) ISPE and (B) ICPE potentiometric sensors modified with NaTPB ion pairing agent.

    Fig.5 Effect of soaking time on the ICPE.

    3.3.3. Linearity

    Linearity of an electroanalytical technique can be defined as a measure of how well the calibration plot of electroanalytical response versus concentration approximates a straight line [40].The standard calibration graph was established using five concentrations of standard NPZ-HCl. It was found that a linear relationship is present between the electrode potential (mV) and the log[NPZ-HCl]. The regression data, correlation coefficients(r)and other statistical parameter are presented in Table 2.

    Table 4 Determination of NPZ-HCl in pharmaceutical formulation (Neozoline) using ISPE and ICPE.

    Table 5 Evaluation of accuracy and precision (intra- and inter-day) of the ISPE and ICPE sensors.

    3.3.4. Specificity

    The specificity of the method was examined by observing any interference caused by the common excipients of the pharmaceutical formulation. It was found that these compounds did not interfere with the results of the proposed method as shown in Table 3.

    3.3.5. LOD and LOQ

    LOD is the lowest quantity of the investigated compound in a sample that can be detected,but not necessarily quantified with an acceptable uncertainly. LOD of an electroanalytical method is an important factor if quantitative measurements are to be made at concentrations close to it. Especially, LOD is necessary for the trace analysis of drug active components in pharmaceuticals and/or biological samples [40]. The values of LOD that are presented in Table 2 indicate that the sensors under investigation are highly sensitive, selective and can be applied in determination of small amounts of NPZ-HCl.

    LOQ is the lowest amount of compound that can be measured in the sample matrix at an acceptable level of accuracy and precision. For many pharmaceutical and biological applications,the LOQ is generally a more useful factor than LOD. The LOQ was determined by establishing the least concentration that can be measured according to ICH Q2(R1)recommendations [41], below which the calibration range is non-linear, and was found to be 1.9×10—6and 1.9×10—6M for ISPE and ICPE, respectively.

    4. Conclusion

    The present work involves the preparation of screen printed and carbon paste electrodes with in situ mode of modification for the determination of NPZ-HCl drug. The screen printed electrodes were characterized and optimized with respect to the main experimental parameters affecting the electrode performance,including composition, pH, temperature, response time and interferences in comparison to carbon paste electrodes. The electrodes showed good selectivity for NPZ-HCl with respect to some inorganic cations, sugars and glycine. The developed electrodes have been successfully used for the determination of NPZ-HCl in pharmaceutical preparation using the standard addition, potentiometric titration and calibration methods.The obtained results were in good agreement with those obtained using the official method.According to the results obtained, the potentiometric sensors can be successfully applied for the routine analysis of this drug.

    [1] 〈http://www.drugs.com/mmx/naphazoline-hydrochloride.html〉,2000—2013.

    [2] P. Chocholou?, D. ?atínsky, P. Solich, Fast simultaneous spectrophotometric determination of naphazoline nitrate and methylparaben by sequential injection chromatography, Talanta 70 (2) (2006)408—413.

    [3] J.M.L. Gallego, J.P. Arroyo, Determination of prednisolone and the most important associated compounds in ocular and cutaneous pharmaceutical preparations by micellar electrokinetic capillary chromatography, J. Chromatogr, B: Anal. Technol. Biomed. Life Sci.784 (1) (2003) 39—47.

    [4] J.M.L.Gallego,J.P.Arroyo,Determination of prednisolone,naphazoline, and phenylephrine in local pharmaceutical preparations by micellar electrokinetic chromatography, J. Sep. Sci. 26 (9—10)(2003) 947—952.

    [5] E. Souri, M. Amanlou, H. Farsam, et al., A rapid derivative spectrophotometric method for simultaneous determination of naphazoline and antazoline in eye drops, Chem. Pharm. Bull. 54 (1) (2006) 119—122.

    [6] H.C. Goicoechea, M.S. Collado, M.S. Satuf, et al., Complementary use of partial least-squares and artificial neural networks for the nonlinear spectrophotometric analysis of pharmaceutical samples, Anal.Bioanal. Chem. 376 (3) (2003) 460—465.

    [7] J.J. Charles, M. Bertucat, Simultaneous determination of naphazoline nitrate and tetramethylthionine base in eye drops by first-derivative UV spectrophotometry, Anal. Lett. 32 (2) (1999) 373—382.

    [8] S.O. Hman, Direct determination of antazoline and naphazoline in mixtures, Drug Dev. Ind. Pharm. 13 (7) (1987) 1257—1265.

    [9] S.Belal,M.A.Elsayed,M.E.Abdel-Hamid,et al.,Utility of chloranil in assay of naphazoline, clemizole, penicillin G sodium, and piperazine, J. Pharm. Sci. 70 (1) (2006) 127—130.

    [10] S.M.Ghoreishi,M.Behpour,M.Nabi,A novel naphazoline-selective membrane sensor and its pharmaceutical applications,Sens.Actuators B 113 (2) (2006) 963—969.

    [11] E.Y.Z. Frag, G.G.Mohamed,F.A.Nour El-Dien,et al., Construction and performance characterization of screen printed and carbon paste ion selective electrodes for potentiometric determination of naphazoline hydrochloride in pharmaceutical preparations, Analyst 136 (2) (2011) 332—339.

    [12] G. Baiulescu, V. Cosofret, Ion-Selective Membrane Electrodes.Applications of Organic Analysis, Wiley, New York, 1977.

    [13] E. Khaled, H.N.A Hassan, G.G. Mohamed, et al., Carbon paste and PVC electrodes for the flow injection potentiometric determination of dextromethorphan, Talanta 81 (2010) 510—515.

    [14] E. Khaled, H.N.A Hassan, G.G. Mohamed, et al., β-Cyclodextrin-based potentiometric sensors for flow-injection determination of acetylcholines,Int. J. Electrochem. Sci. 5 (2010) 448—458.

    [15] E.Y.Z. Frag, G.G. Mohamed, H.M.S. Alelaiwi, Electroanalytical determination of sildenafil in Viagra tablets using screen-printed and conventional carbon paste electrodes, J. Electroanal. Chem. 659(2011) 121—127.

    [16] E.Y.Z. Frag, A.M.K. Mohamed, G.G. Mohamed, et al., Construction and performance characterization of ion selective electrodes for potentiometric determination of ranitidine hydrochloride in pharmaceutical preparations and biological fluids, Int. J. Electrochem. Sci. 6(2011) 3508—3524.

    [17] E.Y.Z. Frag, G.G. Mohamed, M.M. Khalil, et al., Potentiometric determination of ketotifen fumarate in pharmaceutical preparations and urine using carbon paste and PVC membrane selective electrodes,Int. J. Anal. Chem. 2011 (2011) 1—7.

    [18] F.A. Nour El-Dien, G.G. Mohamed, E.Y.Z. Frag, et al., Modified screen printed and carbon paste ion selective electrodes for potentiometric determination of naphazoline hydrochloride in pure and pharmaceutical preparations, Int. J. Electrochem. Sci. 7 (2012)10266—10281.

    [19] I Svancara, P. Kotzian, M. Bartos, et al., Groove electrodes: a new alternative of using carbon pastes in electroanalysis, Electrochem.Commun. 7 (2005) 657—662.

    [20] P.F. Boladoa, D.H. Santosa, P.J.L. Ardisanaa, et al., Electrochemical characterization of screen-printed and conventional carbon paste electrodes, Electrochim. Acta 53 (10) (2008) 3635—3642.

    [21] K. Vytras, Potentiometric titrations based on ion-pair formation, Ion-Sel. Electrodes Rev. 7 (1985) 77—164.

    [22] H. Hayashi, J.B. Moffat, Determination of phosphorus and tungsten in heteropoly acids by EDTA-titration, Talanta 29 (11) (1982) 943—945.

    [23] T.G. Towns, Determination of aqueous phosphate by ascorbic acid reduction of phosphomolybdic acid, Anal. Chem. 58 (1) (1986)223—229.

    [24] W. Selig, Potentiometric titration of thallium(I) with sodium tetraphenylborate, using ion-selective electrodes, Talanta 27 (11) (1980)914—916.

    [25] Y. Umezawa, P. Buhlmann, K. Umezawa, et al., Potentiometric selectivity coefficients of ion-selective electrodes. Part I. Inorganic cations (Technical Report), Pure Appl. Chem. 72 (10) (2000) 1851—2082.

    [26] IUPAC, Pure Appl. Chem. 72 (2000) 1852.

    [27] L.I. Antropov,Theoretical Electrochemistry, Mir Publisher,Moscow,1977.

    [28] K. Tohda, D. Dragoe, M. Shibata, et al., Studies on the matched potential method for determining the selectivity coefficients of ionselective electrodes based on neutral ionophore, Anal. Sci. 17 (2001)733—743.

    [29] R.P. Buck, E. Lindner, Recommendations for nomenclature of ionselective electrodes. (IUPAC Recommendation 1994), Pure Appl.Chem. 66 (1994) 2527—2536.

    [30] Y. Umezawa, K. Umezawa, H. Sato, Selectivity coefficients for ionselective electrodes (Technical Report), Pure Appl. Chem. 67 (3)(1995) 507—510.

    [31] M.R. Ganjali, Z. Memari, F. Faridbod,et al., Samarium microsensor:an asymmetric potentiometric membrane sensor, Int. J. Electrochem.Sci. 3 (2008) 1169—1179.

    [32] V.K.Gupta,S.Chandra,R.Mangla,Magnesium-selective electrodes,Sens. Actuators B 86 (2—3) (2002) 235—241.

    [33] V.K. Gupta, R. Prasad, A. Kumar, Magnesium—tetrazaporphyrin incorporated PVC matrix as a new material for fabrication of Mg2+selective potentiometric sensor, Talanta 63 (4) (2004) 1027—1033.

    [34] H.A. Zamani,G. Rajabzadeh, M.R. Ganjali, Highly selective and sensitive chromium(III) membrane sensors based on 4-amino-3-hydrazino-6-methyl-1,2,4-triazin-5-one as a new neutral ionophore.Sens. Actuators B 119(1) (2006) 41—46.

    [35] A.K. Jain, V.K. Gupta, S. Radi, et al., A comparative study of Pb2+selective sensors based on derivatized tetrapyrazole and calix[4]arene receptors, Electrochim. Acta 51 (12) (2006) 2547—2553.

    [36] E. Linder, K. Toth, E. Pungor, Dynamic Characteristics of Ion-Selective Electrodes, CRC Press, Boca Raton, FL, 1988.

    [37] E.Y.Z. Frag, M.A. Zayed, M.M. Omar, et al., Potentiometric determination of chlorpromazine HCl using carbon paste electrode in pure and pharmaceutical preparations, Int. J. Electrochem. Sci. 7(2012) 650—662.

    [38] E.Y.Z.Frag,T.A Ali,G.G.Mohamed,et al.,Construction of different types of ion-selective electrodes. Characteristic performances and validation for direct potentiometric determination of orphenadrine citrate, Int. J. Electrochem. Sci. 7 (2012) 4443—4464.

    [39] British Pharmacopoeia, Stationary Office London, vol. 1517, 2008.

    [40] M. Gumustas, A.S. Ozkan, The role of and the place of method validation in drug analysis using electroanalytical techniques, Open Anal. Chem. J. 5 (2011) 1—21.

    [41] ICH Harmonized Tripartite Guideline: Validation of Analytical Procedures. Text and Methodology, Q2(R1), 2005.

    欧美精品啪啪一区二区三区| 天堂中文最新版在线下载| 久久久久国内视频| 久久ye,这里只有精品| 午夜福利视频精品| 欧美成人午夜精品| 80岁老熟妇乱子伦牲交| 免费看十八禁软件| 一级毛片电影观看| 9热在线视频观看99| 无遮挡黄片免费观看| videosex国产| 亚洲伊人久久精品综合| 美国免费a级毛片| 国产精品久久久久久精品古装| 国产av一区二区精品久久| 久久99一区二区三区| 国产成人免费观看mmmm| 亚洲午夜理论影院| 国产日韩欧美亚洲二区| 老司机影院毛片| 国产熟女午夜一区二区三区| 黄色毛片三级朝国网站| 自线自在国产av| 亚洲精品粉嫩美女一区| 欧美乱妇无乱码| 久久影院123| 国产精品国产高清国产av | 新久久久久国产一级毛片| 国产精品.久久久| tocl精华| 国产免费视频播放在线视频| av线在线观看网站| 亚洲九九香蕉| 91麻豆av在线| 97人妻天天添夜夜摸| 午夜福利欧美成人| 又大又爽又粗| 久久久久久久久免费视频了| 中文字幕制服av| 亚洲精品美女久久久久99蜜臀| 大香蕉久久成人网| 精品国产乱子伦一区二区三区| 亚洲中文字幕日韩| 欧美黄色片欧美黄色片| 美女主播在线视频| 亚洲国产欧美网| 999久久久精品免费观看国产| tube8黄色片| 午夜福利欧美成人| 日韩人妻精品一区2区三区| 欧美精品人与动牲交sv欧美| 电影成人av| 精品熟女少妇八av免费久了| 亚洲人成伊人成综合网2020| 老司机福利观看| 最近最新中文字幕大全电影3 | 在线观看免费视频网站a站| 黑丝袜美女国产一区| 欧美在线一区亚洲| 精品国产乱码久久久久久小说| 国产精品欧美亚洲77777| 日日夜夜操网爽| 一边摸一边抽搐一进一出视频| 国产成人欧美| 日韩欧美一区视频在线观看| 一进一出好大好爽视频| 免费高清在线观看日韩| 久久精品成人免费网站| 亚洲熟女精品中文字幕| 国产精品欧美亚洲77777| 成人精品一区二区免费| 香蕉久久夜色| 亚洲精品成人av观看孕妇| 亚洲精品国产区一区二| www.自偷自拍.com| videos熟女内射| 欧美黑人精品巨大| 国产免费现黄频在线看| 一个人免费在线观看的高清视频| 免费观看av网站的网址| 中亚洲国语对白在线视频| 麻豆国产av国片精品| 精品午夜福利视频在线观看一区 | 欧美日韩黄片免| 他把我摸到了高潮在线观看 | 丝瓜视频免费看黄片| 人人妻人人澡人人爽人人夜夜| 午夜老司机福利片| 不卡av一区二区三区| 少妇精品久久久久久久| 中国美女看黄片| 国产精品一区二区在线不卡| 亚洲精品在线美女| 国产精品九九99| 精品一区二区三区四区五区乱码| 亚洲va日本ⅴa欧美va伊人久久| 欧美在线黄色| 色精品久久人妻99蜜桃| 中文字幕最新亚洲高清| 超碰97精品在线观看| 在线天堂中文资源库| 人人妻人人澡人人看| 9191精品国产免费久久| 无遮挡黄片免费观看| 久久99一区二区三区| 色尼玛亚洲综合影院| 国产精品亚洲一级av第二区| 国产在线视频一区二区| 久久精品国产99精品国产亚洲性色 | 欧美激情 高清一区二区三区| 婷婷成人精品国产| 午夜激情av网站| 在线观看66精品国产| 一级a爱视频在线免费观看| 男人舔女人的私密视频| av在线播放免费不卡| 亚洲精品国产精品久久久不卡| 亚洲av欧美aⅴ国产| 国产精品美女特级片免费视频播放器 | 精品免费久久久久久久清纯 | av网站在线播放免费| 国产精品免费视频内射| 五月开心婷婷网| 亚洲精品乱久久久久久| 精品少妇一区二区三区视频日本电影| 成人免费观看视频高清| 国产亚洲欧美精品永久| 美女视频免费永久观看网站| 在线观看一区二区三区激情| 午夜福利乱码中文字幕| 国产精品久久久久久人妻精品电影 | 黑人欧美特级aaaaaa片| 老司机亚洲免费影院| 亚洲av成人不卡在线观看播放网| 日本精品一区二区三区蜜桃| 国产在线免费精品| cao死你这个sao货| 99香蕉大伊视频| 久久久精品94久久精品| 窝窝影院91人妻| 成年版毛片免费区| 少妇粗大呻吟视频| 国产精品香港三级国产av潘金莲| 久久久水蜜桃国产精品网| 一夜夜www| 久久久国产成人免费| av一本久久久久| 热99国产精品久久久久久7| 日韩制服丝袜自拍偷拍| 俄罗斯特黄特色一大片| 欧美大码av| 蜜桃国产av成人99| 99国产综合亚洲精品| 高清av免费在线| 丰满饥渴人妻一区二区三| 国产精品九九99| 日韩中文字幕视频在线看片| 黄网站色视频无遮挡免费观看| 女性生殖器流出的白浆| 欧美成人免费av一区二区三区 | 成人国产一区最新在线观看| 国产精品 国内视频| 人人妻人人添人人爽欧美一区卜| 国产一区有黄有色的免费视频| 麻豆av在线久日| 窝窝影院91人妻| 欧美精品高潮呻吟av久久| 一边摸一边抽搐一进一小说 | 亚洲av成人不卡在线观看播放网| 久久久久国内视频| 国产在视频线精品| 中文字幕人妻丝袜一区二区| 日韩中文字幕视频在线看片| 午夜视频精品福利| 电影成人av| 99精品在免费线老司机午夜| 国产又色又爽无遮挡免费看| 后天国语完整版免费观看| 午夜91福利影院| 99国产极品粉嫩在线观看| 一二三四社区在线视频社区8| 夜夜夜夜夜久久久久| 窝窝影院91人妻| 999久久久国产精品视频| 久久人妻熟女aⅴ| 欧美精品av麻豆av| 91成人精品电影| 又大又爽又粗| 欧美人与性动交α欧美软件| 中文字幕人妻丝袜一区二区| 亚洲avbb在线观看| 国产深夜福利视频在线观看| 超色免费av| 精品卡一卡二卡四卡免费| 国产一区有黄有色的免费视频| 国产黄频视频在线观看| 精品卡一卡二卡四卡免费| 考比视频在线观看| 亚洲成国产人片在线观看| 亚洲三区欧美一区| 亚洲精品中文字幕一二三四区 | 久久人妻福利社区极品人妻图片| xxxhd国产人妻xxx| 少妇精品久久久久久久| 亚洲人成电影免费在线| 建设人人有责人人尽责人人享有的| 一个人免费在线观看的高清视频| 青青草视频在线视频观看| 色在线成人网| 欧美日韩福利视频一区二区| 亚洲专区国产一区二区| 国产av精品麻豆| 国产人伦9x9x在线观看| av线在线观看网站| 制服诱惑二区| 变态另类成人亚洲欧美熟女 | 久久国产精品影院| 一夜夜www| 日本av手机在线免费观看| 欧美av亚洲av综合av国产av| 免费在线观看黄色视频的| 水蜜桃什么品种好| 老汉色av国产亚洲站长工具| svipshipincom国产片| 大型黄色视频在线免费观看| 高清毛片免费观看视频网站 | 首页视频小说图片口味搜索| 天堂俺去俺来也www色官网| 亚洲九九香蕉| 久久 成人 亚洲| 国产精品久久久人人做人人爽| 久久这里只有精品19| 亚洲欧美日韩另类电影网站| 天天添夜夜摸| 一级毛片精品| 亚洲成av片中文字幕在线观看| 亚洲成国产人片在线观看| 黄色 视频免费看| 狠狠狠狠99中文字幕| 免费在线观看日本一区| 黄色视频在线播放观看不卡| 91精品三级在线观看| 久久久久国产一级毛片高清牌| 12—13女人毛片做爰片一| 大陆偷拍与自拍| 国产精品一区二区免费欧美| 少妇被粗大的猛进出69影院| 可以免费在线观看a视频的电影网站| 另类精品久久| 国产精品 国内视频| 黑人操中国人逼视频| 亚洲,欧美精品.| 婷婷丁香在线五月| 极品少妇高潮喷水抽搐| 午夜福利在线观看吧| 香蕉久久夜色| 精品久久久久久久毛片微露脸| 亚洲精品国产色婷婷电影| 国产一区有黄有色的免费视频| 欧美日韩一级在线毛片| 精品国产亚洲在线| 久久精品91无色码中文字幕| 老熟妇乱子伦视频在线观看| 老司机影院毛片| 淫妇啪啪啪对白视频| 国产淫语在线视频| 一本色道久久久久久精品综合| 欧美亚洲日本最大视频资源| 18在线观看网站| 99国产精品一区二区三区| 岛国毛片在线播放| 黄色怎么调成土黄色| 久久久精品免费免费高清| 在线av久久热| 国产野战对白在线观看| 亚洲人成电影免费在线| 欧美乱码精品一区二区三区| 久久人人97超碰香蕉20202| 日本精品一区二区三区蜜桃| 国产成人影院久久av| 一级毛片电影观看| 成人国产一区最新在线观看| 欧美人与性动交α欧美精品济南到| 午夜激情av网站| 中文字幕人妻丝袜制服| 丰满少妇做爰视频| 色94色欧美一区二区| 国产日韩一区二区三区精品不卡| 考比视频在线观看| 国产精品欧美亚洲77777| 丁香欧美五月| 可以免费在线观看a视频的电影网站| 久久人人97超碰香蕉20202| 久久精品亚洲av国产电影网| 亚洲五月色婷婷综合| 国产成人精品久久二区二区91| 午夜91福利影院| 国产在线免费精品| 亚洲精品av麻豆狂野| 国产伦理片在线播放av一区| 国产aⅴ精品一区二区三区波| 国产不卡一卡二| 在线av久久热| tube8黄色片| 亚洲国产av新网站| 99国产极品粉嫩在线观看| 亚洲一卡2卡3卡4卡5卡精品中文| 国产无遮挡羞羞视频在线观看| 久久免费观看电影| 九色亚洲精品在线播放| 日韩人妻精品一区2区三区| 欧美国产精品va在线观看不卡| 国产精品一区二区在线观看99| 我的亚洲天堂| 精品人妻熟女毛片av久久网站| 搡老乐熟女国产| av欧美777| 成人国语在线视频| 国产亚洲精品第一综合不卡| 亚洲免费av在线视频| 国产高清视频在线播放一区| 别揉我奶头~嗯~啊~动态视频| 日本黄色视频三级网站网址 | 91成人精品电影| 午夜老司机福利片| 99久久人妻综合| 免费在线观看黄色视频的| 久久婷婷成人综合色麻豆| 大香蕉久久成人网| 999久久久精品免费观看国产| 一边摸一边抽搐一进一小说 | 国产欧美日韩一区二区三| 欧美另类亚洲清纯唯美| 日韩精品免费视频一区二区三区| www.精华液| av在线播放免费不卡| av又黄又爽大尺度在线免费看| 丁香六月天网| 大码成人一级视频| 啦啦啦免费观看视频1| 亚洲成a人片在线一区二区| 国产深夜福利视频在线观看| 日本撒尿小便嘘嘘汇集6| 久久人人97超碰香蕉20202| 精品国产乱码久久久久久小说| 免费在线观看影片大全网站| 欧美日韩福利视频一区二区| 成人国产一区最新在线观看| 性少妇av在线| 91成人精品电影| 国产区一区二久久| 在线观看一区二区三区激情| 亚洲综合色网址| 99re在线观看精品视频| 欧美另类亚洲清纯唯美| 国产av一区二区精品久久| 夫妻午夜视频| 热99久久久久精品小说推荐| 国产日韩一区二区三区精品不卡| www.999成人在线观看| 50天的宝宝边吃奶边哭怎么回事| 老汉色av国产亚洲站长工具| 午夜成年电影在线免费观看| 日韩欧美国产一区二区入口| 免费黄频网站在线观看国产| 极品少妇高潮喷水抽搐| 男女之事视频高清在线观看| 久久久久精品国产欧美久久久| 999精品在线视频| 精品国产一区二区三区久久久樱花| 50天的宝宝边吃奶边哭怎么回事| 日韩免费av在线播放| 久久人妻福利社区极品人妻图片| 国产人伦9x9x在线观看| 每晚都被弄得嗷嗷叫到高潮| 久久人妻熟女aⅴ| 淫妇啪啪啪对白视频| 天天影视国产精品| 别揉我奶头~嗯~啊~动态视频| 欧美激情久久久久久爽电影 | 男女床上黄色一级片免费看| 麻豆国产av国片精品| 女同久久另类99精品国产91| 国产一区二区三区在线臀色熟女 | 国产在线免费精品| svipshipincom国产片| 男女午夜视频在线观看| 中文字幕人妻熟女乱码| 久热爱精品视频在线9| 热99久久久久精品小说推荐| 国产97色在线日韩免费| 黑人巨大精品欧美一区二区mp4| 欧美日韩亚洲综合一区二区三区_| 最新美女视频免费是黄的| 国产在线观看jvid| 精品国产乱码久久久久久小说| 欧美成人午夜精品| 人成视频在线观看免费观看| 两性午夜刺激爽爽歪歪视频在线观看 | 久久精品aⅴ一区二区三区四区| 久9热在线精品视频| 成人特级黄色片久久久久久久 | 黄色 视频免费看| 一夜夜www| 成人精品一区二区免费| 亚洲精品一二三| 国产成人欧美在线观看 | 99九九在线精品视频| 欧美黑人精品巨大| 亚洲人成电影免费在线| 激情在线观看视频在线高清 | 久久久欧美国产精品| 亚洲人成电影免费在线| 一级毛片女人18水好多| 日韩制服丝袜自拍偷拍| 中国美女看黄片| 老司机在亚洲福利影院| 国产伦人伦偷精品视频| 啦啦啦视频在线资源免费观看| 国产伦理片在线播放av一区| 精品午夜福利视频在线观看一区 | 国产午夜精品久久久久久| 91老司机精品| 考比视频在线观看| 久久久久国产一级毛片高清牌| 欧美+亚洲+日韩+国产| 久久久久国内视频| 一边摸一边抽搐一进一出视频| 精品久久久久久久毛片微露脸| 亚洲欧洲精品一区二区精品久久久| 亚洲精品在线观看二区| 欧美精品一区二区免费开放| 建设人人有责人人尽责人人享有的| 国产精品av久久久久免费| 亚洲av片天天在线观看| 捣出白浆h1v1| 国产精品一区二区免费欧美| 欧美黑人精品巨大| 成人国产av品久久久| 亚洲国产精品一区二区三区在线| 搡老乐熟女国产| 一本大道久久a久久精品| 十八禁网站免费在线| 国产男女内射视频| 巨乳人妻的诱惑在线观看| 日本撒尿小便嘘嘘汇集6| 悠悠久久av| 久久天躁狠狠躁夜夜2o2o| 欧美日韩国产mv在线观看视频| 国产精品久久久av美女十八| 香蕉国产在线看| 亚洲欧美一区二区三区久久| 一区二区日韩欧美中文字幕| 国产成人免费观看mmmm| 亚洲欧美精品综合一区二区三区| 久久国产精品大桥未久av| 精品第一国产精品| 国产精品久久久av美女十八| 一区二区av电影网| 一二三四在线观看免费中文在| 久久中文字幕人妻熟女| 免费在线观看日本一区| 他把我摸到了高潮在线观看 | 亚洲美女黄片视频| 国产精品秋霞免费鲁丝片| 超碰97精品在线观看| 欧美亚洲 丝袜 人妻 在线| 水蜜桃什么品种好| 99国产精品一区二区蜜桃av | 在线观看66精品国产| 老鸭窝网址在线观看| 9191精品国产免费久久| 91精品三级在线观看| 丰满迷人的少妇在线观看| 一区福利在线观看| 日韩大片免费观看网站| 日韩免费av在线播放| 最新的欧美精品一区二区| 一本大道久久a久久精品| 久久精品人人爽人人爽视色| 50天的宝宝边吃奶边哭怎么回事| 国产又色又爽无遮挡免费看| 大码成人一级视频| 久久久国产欧美日韩av| 亚洲成a人片在线一区二区| 亚洲av成人不卡在线观看播放网| 亚洲人成电影免费在线| 亚洲国产欧美日韩在线播放| 免费人妻精品一区二区三区视频| 亚洲五月色婷婷综合| 最近最新免费中文字幕在线| 亚洲va日本ⅴa欧美va伊人久久| 少妇裸体淫交视频免费看高清 | 国产精品免费一区二区三区在线 | 亚洲精品一卡2卡三卡4卡5卡| 久9热在线精品视频| 一个人免费看片子| 亚洲情色 制服丝袜| 亚洲人成77777在线视频| 黄色视频在线播放观看不卡| 亚洲人成电影免费在线| 国产又色又爽无遮挡免费看| 免费在线观看日本一区| 狠狠狠狠99中文字幕| 欧美日韩av久久| 久久香蕉激情| 日韩视频在线欧美| 啦啦啦中文免费视频观看日本| 免费观看av网站的网址| 亚洲精品在线美女| 久久久久视频综合| 99国产精品免费福利视频| 一本大道久久a久久精品| 高清毛片免费观看视频网站 | 亚洲国产欧美网| 电影成人av| 91字幕亚洲| 午夜成年电影在线免费观看| 成人免费观看视频高清| 黄色视频在线播放观看不卡| 99久久国产精品久久久| 国产免费av片在线观看野外av| 免费一级毛片在线播放高清视频 | 久久久久久久大尺度免费视频| 国产区一区二久久| 亚洲男人天堂网一区| 在线观看舔阴道视频| a级毛片在线看网站| 91字幕亚洲| 法律面前人人平等表现在哪些方面| 国产午夜精品久久久久久| a级毛片黄视频| 别揉我奶头~嗯~啊~动态视频| 欧美在线黄色| 啦啦啦在线免费观看视频4| 69av精品久久久久久 | 亚洲综合色网址| 欧美日本中文国产一区发布| 在线 av 中文字幕| 免费在线观看黄色视频的| 久久亚洲精品不卡| 国产成人免费无遮挡视频| 免费女性裸体啪啪无遮挡网站| 亚洲中文字幕日韩| 久久久久视频综合| 成年人免费黄色播放视频| 亚洲午夜精品一区,二区,三区| 亚洲人成电影免费在线| 一区二区日韩欧美中文字幕| 色综合婷婷激情| 国产黄色免费在线视频| 丁香六月天网| 无遮挡黄片免费观看| 国产一区二区 视频在线| 黄频高清免费视频| 亚洲精品国产区一区二| 久久久国产一区二区| 国产午夜精品久久久久久| 97人妻天天添夜夜摸| 亚洲国产av影院在线观看| 18禁国产床啪视频网站| 老司机深夜福利视频在线观看| 两性夫妻黄色片| 国产xxxxx性猛交| 脱女人内裤的视频| 交换朋友夫妻互换小说| 嫩草影视91久久| 搡老乐熟女国产| 狠狠婷婷综合久久久久久88av| 欧美亚洲日本最大视频资源| 欧美另类亚洲清纯唯美| 91成年电影在线观看| 亚洲熟女毛片儿| 可以免费在线观看a视频的电影网站| 国产欧美日韩精品亚洲av| 成年人午夜在线观看视频| 女警被强在线播放| 国产一卡二卡三卡精品| 老司机深夜福利视频在线观看| 别揉我奶头~嗯~啊~动态视频| 久热这里只有精品99| 天天躁日日躁夜夜躁夜夜| 青草久久国产| 久久狼人影院| 丝袜美足系列| 欧美乱妇无乱码| avwww免费| 亚洲成人手机| 黄片大片在线免费观看| 国产精品麻豆人妻色哟哟久久| 啦啦啦在线免费观看视频4| 亚洲精品自拍成人| 精品亚洲成国产av| 啦啦啦中文免费视频观看日本| 久久免费观看电影| 丝袜喷水一区| 久久 成人 亚洲| 高清毛片免费观看视频网站 | 国产精品98久久久久久宅男小说| 99久久精品国产亚洲精品| 天堂动漫精品| 国产精品1区2区在线观看. | 久久国产精品人妻蜜桃| 最近最新中文字幕大全免费视频| 黑人巨大精品欧美一区二区蜜桃| 国产精品一区二区在线不卡| 亚洲av日韩在线播放| 乱人伦中国视频| 黄色怎么调成土黄色| 一级,二级,三级黄色视频| 欧美av亚洲av综合av国产av| 国产免费视频播放在线视频| 国产黄频视频在线观看| 久久亚洲精品不卡|