B Uslu

Publications (24)38.11 Total impact

• Article: Anodic behaviour of fulvestrant and its voltammetric determination in pharmaceuticals and human serum on highly boron-doped diamond electrode using differential pulse adsorptive stripping voltammetry

  B. Dogan-Topal, Dilek Kul, Sibel A. Ozkan, B. Uslu
  [show abstract] [hide abstract]
  ABSTRACT: The electrochemical oxidation of fulvestrant was made on highly boron-doped diamond electrode using differential pulse adsorptive stripping voltammetry. The highest current intensities were obtained by applying ?1.10 V during 150 s for boron-doped diamond electrode. For boron-doped diamond electrode, linear responses were obtained for the concentrations between 1 9 10-6 and 8 9 10-5 M in standard samples and between 1 9 10-6 and 4 9 10-5 M in serum samples. The repeatability of the method was 0.55 RSD% for differential pulse adsorptive stripping voltammetry. The analytical values of the method are demonstrated by quantitative determination of fulvestrant in pharmaceutical formulations and human serum, without the need for separation or complex sample preparation, since there was no interference from the excipients and endogenous substances. Selectivity, reproducibility, and accuracy of the developed methods were demonstrated by recovery studies.
  Journal of Applied Electrochemistry 09/2011; 41:1253-1260. · 1.75 Impact Factor
• Article: Anodic voltammetry of zolmitriptan at boron-doped diamond electrode and its analytical applications.

  B Uslu, D Canbaz
  [show abstract] [hide abstract]
  ABSTRACT: The electrooxidative behavior and determination of zolmitriptan at a boron-doped diamond electrode were investigated using cyclic, linear sweep, differential pulse and square wave voltammetric techniques. Zolmitriptan undergoes irreversible oxidation at a peak potential of about +0.9 V (vs Ag/AgCl/3 M KCl). DPV and SWV techniques are proposed for the determination of zolmitriptan in phosphate buffer at pH 3.03, which allows quantitation over the two different ranges (8 x 10(-7) - 8 x 10(-6) M and 1 x 10(-5) - 1 x 10(-4) M) in supporting electrolyte for both methods. A linear response was obtained in phosphate buffer over two different ranges (6 x 10(-7) - 8 x 10(-6) M and 1 x 10(-5) - 1 x 10(-4) M) for spiked serum samples at pH 3.03 for both techniques. The repeatability and reproducibility of the methods for all media were determined. The standard addition method was used in serum. Precision and accuracy were also checked in all media. No electroactive interferences from the excipients and endegenous substances were found in the pharmaceutical dosage form and the biological sample, respectively.
  Pharmazie 04/2010; 65(4):245-50. · 1.01 Impact Factor
• Article: Assessment of adrenal functions in patients with autosomal dominant polycystic kidney disease.

  F Tufan, B Uslu, B Cekrezi, M Uysal, N Alpay, K Turkmen, R Disci, N C Ozbey, T Ecder
  [show abstract] [hide abstract]
  ABSTRACT: Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary kidney disease and extrarenal manifestations may be observed in many organ systems. Hypothalamus-pituitary-adrenal axis was not evaluated extensively in patients with ADPKD. We aimed to evaluate this axis in these patients. Twenty two patients with ADPKD and 27 healthy subjects were enrolled. Basal dehydroepiandrosterone sulfate (DHEAS) levels and cortisol and DHEA responses to low dose short adrenocorticotropin stimulation test were assessed. Correlation analyses of these parameters with glomerular filtration rates (GFR), renal volumes and pain characteristics in patients with ADPKD were performed. Patients with ADPKD had higher basal cortisol levels (12.1 ± 3.4 vs. 9.6 ± 4.3 μg/dL, p=0.033), and higher basal cortisol/DHEAS ratios (0.073 ± 0.05 vs. 0.045 ± 0.02, p=0.015) compared to controls. None of the subjects had inadequate response to adrenocorticotropin stimulation. Patients with ADPKD had lower delta cortisol (absolute increase between peak and basal) levels (10.3 ± 2.8 vs. 12.6 ± 4.2 μg/dL, p=0.026) compared to controls. Subgroup analysis showed that significant differences existed only between female patients and female controls. There was no significant correlation between cortisol levels and renal volumes or GFR. A significant correlation was found only between delta cortisol and pain frequency in female patients. Patients with ADPKD had higher basal cortisol levels, higher basal cortisol/DHEAS ratios and lower delta cortisol levels compared to controls, indicating promptly stimulated zona fasciculata function. Further studies are needed to confirm these results and to investigate possible underlying mechanisms.
  Experimental and Clinical Endocrinology &amp Diabetes 02/2010; 118(10):741-6. · 1.69 Impact Factor
• Article: Simultaneous Determination of Abacavir, Efavirenz and Valganciclovir in Human Serum Samples by Isocratic HPLC-DAD Detection

  B. Dogan-Topal, S. A. Ozkan, B. Uslu
  [show abstract] [hide abstract]
  ABSTRACT: A rapid, sensitive, and specific reverse phase high performance liquid chromatography with diode array detection procedure for the simultaneous determination of abacavir, efavirenz and valganciclovir in spiked human serum is described. Separation was performed on a 5μm Waters Spherisorb column (250×4.6mm ID) with acetonitrile: methanol:KH2PO4 (at pH 5.00) (40:20:40 v/v/v) isocratic elution at a flow rate of 1.0mLmin−1. Calibration curves were constructed in the range of 50–30,000ngmL−1 for abacavir and efavirenz, and 10–30,000ngmL−1 for valganciclovir in serum samples. The limit of detection and limit of quantification concentrations of the HPLC method were 3.80 and 12.68ngmL−1 for abacavir, 2.61 and 8.69ngmL−1 for efavirenz, 1.30 and 4.32ngmL−1 for valganciclovir. The method has been applied, without any interference from excipients or endogenous substances, for the simultaneous determination of these three compounds in human serum.
  Chromatographia 08/2007; 66:25-30. · 1.20 Impact Factor
• Article: Vitamin E protects against the development of radiation-induced pulmonary fibrosis in rats.

  N S Bese, F Munzuroglu, B Uslu, S Arbak, G Yesiladali, N Sut, T Altug, A Ober
  [show abstract] [hide abstract]
  ABSTRACT: To investigate whether the application of vitamin E with or without pentoxifylline could modify the development of radiation-induced pulmonary fibrosis. Wistar albino rats were supplemented with either vitamin E or pentoxifylline or with both vitamin E and pentoxifylline after a single dose of 14 Gy thoracic irradiation. Supplementation was started the day after irradiation and continued until the rats were sacrificed. As a quantitative end point, the extent of fibrosis was evaluated with a scale from 0 (normal lung) to 8 (total fibrous obliteration of the field) at pathological examination of the lung tissue. A significant reduction in fibrosis was obtained in the group of rats supplemented with vitamin E with or without pentoxifylline, when compared with the group that had irradiation only. This experimental study showed that vitamin E supplementation immediately after irradiation protected rats against radiation-induced pulmonary fibrosis. The combination with pentoxifylline was more effective, although pentoxifylline itself had limited efficacy, which was not statistically significant.
  Clinical Oncology 06/2007; 19(4):260-4. · 2.07 Impact Factor
• Source

  Available from: dspace.ubvu.vu.nl

  Article: Determination of Abacavir, Lamivudine and Zidovudine in Pharmaceutical Tablets, Human Serum and in Drug Dissolution Studies by HPLC

  A. Savaşer, S. Goraler, A. Taşöz, B. Uslu, H. Lingeman, S. A. Özkan
  [show abstract] [hide abstract]
  ABSTRACT: A simple, accurate, precise and fully automated method for the simultaneous determination of abacavir, lamivudine and zidovudine in pharmaceutical tablets, human serum samples and drug dissolution studies has been developed. Separation was performed on a 5μm Zorbax® C18 column (150×4.6mm ID) with methanol:water:phosphate buffer at pH 5.65 (80:10:10; v/v/v) isocratic elution in less than 7min with a flow rate of 0.6mLmin−1.Good sensitivity for all analytes was observed with UV detection at 275nm. The method allowed quantitation over the 500–3,000ngmL−1 range for abacavir and 500–5,000ngmL−1 range for lamivudine and zidovudine. The method has been applied, without any interference from excipients or endogenous substances, for the simultaneous determination of these three compounds in tablets. Human serum and drug dissolution studies.
  Chromatographia 02/2007; 65(5):259-265. · 1.20 Impact Factor
• Article: Application of environmental impact quotient model to Kumluca region, Turkey to determine environmental impacts of pesticides.

  A Muhammetoglu, B Uslu
  [show abstract] [hide abstract]
  ABSTRACT: Besides the new developments in agricultural technology, intensive use of pesticides poses a great environmental hazard. The unthinking use of pesticides leads to contamination of air, water and soil. There are several pesticide risk indicator models available in the literature to assess pesticide impacts on the applicator and the ecosystem which is an important issue. This paper refers to an application of a pesticide risk indicator model, called Environmental Impact Quotient (EIQ) which was developed to measure the environmental impacts of pesticide active ingredients used in vegetable and fruit production. The application site is the Kumluca region of Turkey, which is well known for its intensive agricultural activities. As the first step in the model application, EIQ values have been calculated for 35 commonly used pesticides in Kumluca. EIO values were then turned into EIQ field use rating results based on the active ingredient percent and application rate. Furthermore, some pesticide management scenarios were evaluated to select the least detrimental pesticide by comparing EIO model results. The EIO model is an easily applied and very helpful tool for pest management practitioners and agricultural specialists. It can be used efficiently to compare different agricultural pest management strategies or programs.
  Water Science & Technology 02/2007; 56(1):139-45. · 1.12 Impact Factor
• Article: Development and Validation of an RP-HPLC Method for Determination of Valganciclovir in Human Serum and Tablets

  B. Dogan-Topal, B. Uslu, S. A. Ozkan
  [show abstract] [hide abstract]
  ABSTRACT: This paper describes the validation of an isocratic high-performance liquid chromatographic method for the assay of valganciclovir in raw materials, tablets and human serum samples. Valganciclovir and fluvastatin (internal standard) were well separated using a reversed phase column and a mobile phase consisting of a mixture of acetonitrile:methanol:KH2PO4 (0.02M) (40:20:40; v/v/v) (at pH 5.0). The mobile phase was pumped at 1.0mLmin−1 flow rate and valganciclovir was detected by diode-array detection at 255nm. The retention times for valganciclovir and fluvastatin were 3.41 and 5.60min, respectively. A linear response (r>0.999) was observed in the range of 10–30,000ngmL−1 in mobile phase and serum. The limit of detection and limit of quantification were found as 2.95 and 9.82ngmL−1 in mobile phase and 1.73 and 5.77ngmL−1 in human serum samples, respectively. Validation parameters as precision, accuracy, selectivity, reproducibility and system suitability tests were also determined. The method can be used for valganciclovir assay of tablets and human serum samples as the method separates valganciclovir from tablet excipients and endogenous substances.
  Chromatographia 01/2007; 66:97-101. · 1.20 Impact Factor
• Article: T-cell-rich B-cell lymphoma of the spleen presenting with severe hypersplenism.

  G Dincol, M Agan, O Dogan, R Diz-Kucukkaya, B Uslu
  [show abstract] [hide abstract]
  ABSTRACT: We report a 19-year-old woman who was presented with B-symptoms, massive splenomegaly, hepatomegaly and hypersplenism. She underwent diagnostic/therapeutic splenectomy. Microscopically, the spleen showed a vaguely micronodular and diffuse proliferation of lymphoid cells in the white pulp that also involved the red pulp. On immunohistochemical staining, this proliferation consisted predominantly of CD3(+), CD7(+) small T cells with the presence of a minor population of CD15(-),CD30(-), CD20(+) large atypical B cells. A liver biopsy also showed a similar morphology to that seen in the spleen. After splenectomy, only the pancytopenia improved. A combined immunochemotherapy regimen (rituximab, cyclophosphamide, doxorubicin, vincristine and prednisolone) was utilized, which resulted in a complete remission.
  Clinical & Laboratory Haematology 01/2007; 28(6):419-22. · 1.11 Impact Factor
• Article: Electrochemical methods for determination of the protease inhibitor indinavir sulfate in pharmaceuticals and human serum.

  B Dogan, D Canbaz, S A Ozkan, B Uslu
  [show abstract] [hide abstract]
  ABSTRACT: Indinavir sulfate is an inhibitor of the human immunodeficiency virus (HIV) protease. The aim of this study was to determine indinavir levels in serum and pharmaceuticals, by means of electrochemical methods using the hanging mercury drop electrode (HMDE). Indinavir exhibited irreversible cathodic waves over the pH range 2.00-12.00 in different supporting electrolytes. The current-concentration plot was rectilinear over the range from 8 x 10(-7) M to 8 x 10(-6) M with a correlation coefficient of 0.996 for differential pulse voltammetry (DPV) and 8 x 10(-7) M to 1 x 10(-5) M with correlation of 0.999 M for osteryoung square ware voltammetry (OSWV) in Britton-Robinson buffer at pH 10.00. The wave was characterized as being irreversible and diffusion-controlled. The proposed methods were fully validated and successfully applied to the determination of indinavir in capsules and spiked human serum samples with good recoveries. The repeatability and reproducibility of the methods as well as precision and accuracy (such as supporting electrolyte, serum samples) were determined. No electroactive interferences from the endogenous substances were found in serum samples.
  Pharmazie 06/2006; 61(5):409-13. · 1.01 Impact Factor
• Source

  Available from: Sibel A. Ozkan

  Article: Anodic voltammetric behavior of ascorbic acid and its selective determination in pharmaceutical dosage forms and some Rosa species of Turkey

  C. S. Erdurak-Kiliç, B. Uslu, B. Dogan, U. Ozgen, S. A. Ozkan, M. Coskun
  [show abstract] [hide abstract]
  ABSTRACT: Ascorbic acid is the most common electroactive biological compound found in some plant species (e.g., Citrus species, Rosa species). The electrochemical oxidation of ascorbic acid was investigated by cyclic, linear sweep, differential pulse (DPV), and square wave (SWV) voltammetry. For analytical purposes, a very well-resolved diffusion-controlled voltammetric peak was obtained in acetate buffer at pH 3.50 for DPV and SWV. The linear response was obtained in the range of 3.52–176.1 μg/mL with a detection limit of 0.88 μg/mL for DPV and 0.52 µg/mL for SWV. Based on this study, simple, rapid, selective, and sensitive voltammetric methods were developed for the determination of ascorbic acid in pharmaceutical dosage forms and Rosa species (R. dumalis ssp. boissieri var. boissieri, R. canina, R. pulverulenta, R. heckeliana ssp. vanheurckiana, and R. montana subsp. woronowii). The results obtained are compared with the HPLC data. The developed methods enable the extracts to be analyzed without the necessity of any time-consuming separation.
  Journal of Analytical Chemistry 01/2006; 61(11):1113-1120. · 0.75 Impact Factor
• Article: CE Determination of Droperidol in Tablets and Human Serum

  M. Tuncel, D. Dogrukol-Ak, D. Yeniceli, B. Uslu, B. Dogan
  [show abstract] [hide abstract]
  ABSTRACT: A capillary electrophoretic method was described for the determination of droperidol in pharmaceutical tablets and human serum. Droperidol and internal standard, lansoprazole, were separated on an uncoated fused-silica capillary using a run buffer containing borate (10 mM; pH 9.3) and aqueous methanol (20%, υ/υ). The signals were detected at 210 nm. The migration times for droperidol and internal standard were 2.1 and 2.9 min, respectively. The method has been validated in the range of 2.2 × 10−5 − 7.8 × 10−5 M and applied to both tablets and human serum with good repeatability and no interference.
  Chromatographia 01/2006; 63(9):507-511. · 1.20 Impact Factor
• Article: Anodic adsorptive stripping voltammetry of the antihypertensive drug candesartan cilexetil at a glassy carbon electrode.

  B Dogan, B Uslu, S A Ozkan
  [show abstract] [hide abstract]
  ABSTRACT: The electrochemical behaviour of candesartan cilexetil (CND) was investigated in an acetonitrile: supporting electrolyte mixture (30% acetonitrile) in the pH range 1.5-11.00 by cyclic, linear sweep, differential pulse (DPV), adsorptive stripping differential pulse (AdSDPV), square wave (SWV) and adsorptive stripping square wave (AdSSWV) voltammetric techniques. CND exhibited one wave and one peak to the anodic direction. The oxidation process was found to be irreversible and adsorption controlled. To obtain good sensitivity, the instrumental and accumulation variables were studied using DPV and SWV techniques. Two linear calibration plots were obtained for both techniques. The detection limits were 9.15 x 10(-7) M and 7.94 x 10(-6) M for AdSDPV and AdSSWV, respectively. The method was validated and successfully applied for the analysis of CND tablets.
  Pharmazie 12/2004; 59(11):840-4. · 1.01 Impact Factor
• Article: Validated RP-hPLC method for the assay of zalcitabine in drug substance, formulated products and human serum.

  B Uslu, A Savaşer, S A Ozkan, Y Ozkan
  [show abstract] [hide abstract]
  ABSTRACT: A HPLC method for zalcitabine determination in bulk form, pharmaceutical dosage forms and human serum has been developed and validated. The proposed method was conducted using a reverse phase technique, and UV monitoring at 265 nm. The mobile phase consisted of methanol: 0.01 M NaH2PO4 (85:15; v/v) adjusted to pH 4.62 with 1 M NaOH. The detector response was linear in the range of 0.015-50 microg mL(-1). The limit of detection and the limit of quantification of the procedure were 0.0066 microg mL(-1) and 0.022 microg mL(-1), respectively. The retention time was 2.5 min for zalcitabine and 3.5 min for the internal standard. No interferences from tablet additives were observed and analysing tablets containing zalcitabine proved the applicability of the method. This method was also applied for the determination of zalcitabine in spiked human serum samples.
  Pharmazie 09/2004; 59(8):604-7. · 1.01 Impact Factor
• Article: Differential pulse and square wave voltammetric determination of cisapride in tablet dosage form.

  E Satana, B Uslu, S A Ozkan
  Pharmazie 08/2002; 57(7):501-3. · 1.01 Impact Factor
• Article: Simultaneous determination of melatonin and pyridoxine in tablet formulations by differential pulse voltammetry.

  B Uslu, B T Demircigil, S A Ozkan, Z Sentürk, H Y Aboul-Enein
  [show abstract] [hide abstract]
  ABSTRACT: A method has been developed for the simultaneous determination of melatonin (MT) and pyridoxine hydrochloride (PY) in pharmaceutical dosage forms by differential pulse voltammetry, based on the oxidation of both drugs at a glassy carbon electrode. Cyclic and linear scan voltammetry were used to examine the influence of pH, nature of the buffer, scan rate and concentration. The results in 0.5 M H2SO4 with 20% methanol allowed a method to be developed for the determination of MT and PY simultaneously and in the presence of each other in the ranges 2 x 10(-5)-8 x 10(-5) and 2 x 10(-5)-4 x 10(-4) M, with the detection limits of 5.86 x 10(-6) and 2.45 x 10(-6) M, respectively. The proposed method was successfully applied to the commercial tablets containing this drug combination without any interference by the excipients.
  Pharmazie 01/2002; 56(12):938-42. · 1.01 Impact Factor
• Article: Determination of olsalazine sodium in pharmaceuticals by differential pulse voltammetry.

  B Uslu, S Yilmaz, S A Ozkan
  [show abstract] [hide abstract]
  ABSTRACT: The electrochemical oxidation of olsalazine sodium was investigated by cyclic, linear sweep, differential pulse and square wave voltammetry using glassy carbon disc electrode in different buffer systems. Best results were obtained for the determination of olsalazine using the differential pulse voltammetric technique in phosphate buffer at pH 7.0. The electroactive species exhibits a diffusion-controlled voltammetric wave and its differential pulse peak current shows a linear dependence on olsalazine concentration in the range between 2 x 10(-6) M and 2 x 10(-4) M. This relationship has been applied to the determination of olsalazine in commercial capsule dosage forms. The recovery study shows good accuracy and precision for the assay developed. A UV spectrophotometric assay is also reported for comparison.
  Pharmazie 09/2001; 56(8):629-32. · 1.01 Impact Factor
• Article: Study on electrooxidation of cefadroxil monohydrate and its determination by differential pulse voltammetry.

  S A Ozkan, N Erk, B Uslu, N Yilmaz, I Biryol
  [show abstract] [hide abstract]
  ABSTRACT: In this work electrooxidation of cefadroxil monohydrate was investigated using a glassy carbon electrode depending on pH and supporting electrolyte. It was shown that the direct determination of the substance from capsules and in oral suspension could be made by differential pulse voltammetry (DPV). UV and first derivative UV spectrophotometric methods are also proposed as comparative methods.
  Journal of Pharmaceutical and Biomedical Analysis 09/2000; 23(2-3):263-73. · 2.97 Impact Factor
• Article: The study of the voltammetric behaviour of flunarizine.

  B Uslu, N Yílmaz, N Erk, S A Ozkan, Z Sentürk, I Biryol
  Journal of Pharmaceutical and Biomedical Analysis 11/1999; 21(1):215-20. · 2.97 Impact Factor
• Article: Voltammetric determination of amoxicillin using a poly (N-vinyl imidazole) modified carbon paste electrode.

  B Uslu, I Biryol
  Journal of Pharmaceutical and Biomedical Analysis 08/1999; 20(3):591-8. · 2.97 Impact Factor