丝网印刷选择离子电极测定药物试剂中的氢溴酸西酞普兰

2014-10-24TamerAwadAli等

分析化学 2014年4期

TamerAwadAli等

2Experimental

2.1Apparatus and reagents

Laboratory potential measurements were performed using HANNA 211 pH meter. An Ag/AgCl doublejunction reference electrode （Metrohm 6.0726.100） was used in conjugation with different ion selective electrodes. Digital burette was used for the field measurement of drugs under investigation.

Elemental analysis for carbon， hydrogen， nitrogen， and sulphur were carried out at the Microanalytical centers， Cairo University， using a PerkinElmer CHN 2400 Elemental Analyzer.

All chemicals used in the experiment were of analytical reagent grade unless otherwise stated and doubly distilled water was used. CPB was purchased from Western pharmaceutical industries， Egypt. Depaway 40 （sample 1）， cipram 20 （sample 2） were purchased from Memphis， Egypt and multi pharma/lundbeek， Denmark. Sodium tetraphenylborate （NaTPB） and phosphotungstic acid （PTA） were purchased from SigmaAldrich and Fluka， respectively. Tricresylphosphate （TCP） from Alfa Aesar was used for the preparation of the sensors. Other types of plasticizers， namely dioctylphthalate （DOP）， dibutylphthalate （DBP） and dioctylsebacate （DOS） were purchased from Sigma， Merck and Merck， respectively. Relative high molecular weight polyvinylchloride （PVC）（Aldrich）， potassium tetrakis（pchlorophenyl） borate （KTpClPB）（Aldrich） and graphite powder （synthetic 1-2 μm）（Aldrich） were used for the fabrication of different electrodes.

3.4.5Reproducibility and stability of electrodes

The reproducibility and stability of the screenprinted electrodes were evaluated by repeated calibration of the electrodes inCPB solutions. The repeated monitoring of potentials and calibration， using the same electrodes， over several days gave good slope reproducibility；

almost over a period of five weeks， with standard deviation （SD） of slope ≤0.5 mV/decade. For 10 successive replicate measurements at 0.01 mol/L CPB concentrations， the SD was 0.92 mV. The specifications and general characteristic performance of the proposed CPB sensors are given in Table 2.

3.5Selectivity of electrodes

The interference effect of different organic and inorganic cations on the electrodes response was evaluated. The interference of these compounds was assessed by measuring the selectivitycoefficient Kpotdrug， jusing the separate solutions and matched potential methods[19-21] with 1 mmol/L concentration of both the standard CPB and the interference. Results obtained were given in Table 4. Selectivity of the electrodes was observed in presence of some interferents. In most cases， no significant influence on the electrode performance was observed.

3.6Quantification， accuracy and precision

The proposed potentiometric method was used for direct determination of the investigated drug where its concentration was calculated from calibration graph. Results obtained were compared with the official method[22] （Table 5）. The data in Table 5 indicate that the results obtained by the two reported methods are in good agreement. In addition， the proposed methods were used for determination of the studied drug in pharmaceutical preparations （Table 5）.

3.7Analysis of urine and human serum

Citalopram can be determined in urine and human serum by using potentiometric determinations and the results obtained are summarized in Table 6.

The accuracy of the proposed potentiometric method as investigated by the determination of CPB in spiked citalopram samples prepared from serial concentrations of CPB reference standards was reported. The proposed method can therefore be applied to the determination of CPB alone and in pharmaceutical preparations or in biological fluids without fear of interferences caused by the excipients expected to be present in tablets or the constituents of body fluids.

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