Person: TEKKELİ, ŞERİFE EVRİM
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Publication Metadata only ANALYTICAL METHODS FOR THE DETERMINATION OF POLYBROMINATED DIPHENYL ETHERS IN HUMAN MILK(2020-03-01T00:00:00Z) ASRAM SAĞIROĞLU, ALİ; Onal, Cem; DİNCEL, DEMET; Onal, Armagan; ASRAM SAĞIROĞLU, ALİ; TEKKELİ, ŞERİFE EVRİM; DİNCEL, DEMETPolybrominated diphenyl ethers (PBDEs), which are used as flame retardants, are widely used additives so many different kind of materials that are consumed by public. Current researches reveal a significant increase in the levels of PBDEs in human biological fluids all around the world. According to International Agency for Research on Cancer (IARC), PBDEs are declarated as carcinogenic agents and additionally a considerable risks have been shown in animal studies such as liver damage, alteration of thyroid hormone levels, neurotoxicity and hazardous effects on development of fetus. Due to the simplicity of human exposure routes such as ingestion, inhalation or dermal contact, it gains high importance to quantify PBDEs in biological fluids. The exposure to PBDEs is critic aspecially during pregnancy, fetus development and infancy. Excretion of PBDEs in human milk is the focus area for researchers in recent years.Publication Metadata only High performance liquid chromatographic analysis of lercanidipine in human breast milk(2019-01-01) Tekkeli, Evrim Kepekci; GAZİOĞLU, IŞIL; TIRIS, GİZEM; Onal, Cem; TEKKELİ, ŞERİFE EVRİM; GAZİOĞLU, IŞIL; TIRIS, GİZEMA simple, rapid, precise and accurate isocratic reversed phase HPLC method was developed and validated for the determination of lercanidipine hydrochloride in pharmaceutical tablets and spiked human breast milk. The chromatographic separation was achieved on C18 (250x4.6 mmx5 mu m) column using a mobile phase consisting of acetonitrile and phospate buffer (pH=4) (55:45, v/v) at a flow rate of 1.1 mL/min and UV detection at 237 nm. The linearity of the proposed method was investigated in the range of 1.0-40 mu g/mL (r(2)=0.9990). The method was validated in terms of accuracy, precision, reproducibility, specificity, robustness, and detection and quantification limits, in accordance with ICH guidelines. The proposed method is found as suitable for routine quantification of lercanidipine in human breast milk.Publication Metadata only Development of An HPLC Method for the Determination of Mesalazine in Human Plasma by Fluorimetric Derivatization and Application to A Prototype Pharmacokinetic Study(2021-11-01T00:00:00Z) Ceylan, Burhan; Tekkeli, Evrim Kepekci; Onal, Cem; TEKKELİ, ŞERİFE EVRİMIn this study, a new, fast and sensitive HPLC method with fluorometric detection was developed for the determination of mesalazine in human plasma and applied to a pharmacokinetic study. Mesalazine was precolumn derivatized with NBD-Cl and the fluorescent derivative was separated on a C18 (150 x 4.6 mm x 2.6 mu m) analytical column at 30 oC using a mobile phase composed of acetonitrile-0.1% o-phosphoric acid in water (70:30, v/v) by isocratic elution with flow rate of 1.0 mL min(-1). The method was based on the measurement of the derivative using fluorescence detection (lambda(ex) = 280 nm, lambda(em) = 325 nm). The retention time of mesalazine is 3.08 +/- 0.06 min. Nortriptiline was used as internal standard. This currently developed method was validated according to ICH criteria by evaluating the specificity, linearity, precision, accuracy and robustness. The method was determined to be linear in a concentration range of 0.25-1.5 mu g mL(-1) with the correlation coefficient of 0.9997. LOD and LOQ were found to be 0.075 and 0.25 mu g mL(-1), respectively. Intraday and interday RSD values were less than 5.92%. The plasma concentration-time profile and pharmacokinetic parameters such as AUC(0-t), AUC(0-infinity), C-max, t(max), t(1/2), were calculated according to the assays. The presented method can certainly be used for bioequivalence and bioavailability investigations and routine analysis of the drug in plasma.Publication Metadata only Spectrofluorimetric analysis of ticagrelor in pharmaceutical formulations and spiked human plasma using 1-dimethylaminonaphthalene-5-sulphonyl chloride reagent(2020-01-01T00:00:00Z) TEKKELİ, ŞERİFE EVRİM; TEKKELİ, ŞERİFE EVRİMA sensitive method is presented for the determination of the ticagrelor (TCG) in human plasma and pharmaceutical preparations using 5-(dimethylamino)naphthalene-1-sulfonyl chloride (dansyl chloride). Ticagrelor contains a secondary amino group which reacts with dansyl chloride in the presence of 0.5 M sodium bicarbonate (pH 10) to yield a highly fluorescent derivative that is measured at 445 nm after excitation at 340 nm. Different experimental parameters affecting the fluorescence intensities were carefully studied and optimized. The proposed method was also validated according to ICH guidelines. The fluorescence concentration plot was rectilinear over the range of 20.0-200.0 ng mL(-1), with a coefficient of determination of 0.9999 with a limit of detection (LOD) of 0.14 ng mL(-1) and the limit of quantitation (LOQ) of 0.46 ng mL(-1). The proposed method was applied successfully to the analysis of TCG in spiked human plasma and pharmaceutical dosage forms with good accuracy and precision.Publication Metadata only Ultra-fast liquid chromatography method for the determination of ticagrelor in pharmaceutical formulations and spiked plasma samples(2019-07-01T00:00:00Z) Onal, Cem; TEKKELİ, ŞERİFE EVRİM; TEKKELİ, ŞERİFE EVRİMThis article aims to present a sensitive, and precise stability-indicating ultra fast liquid chromatographic method, which was developed to determine ticagrelor (TCG) in pharmaceutical formulations and spiked plasma samples. Chromatographic separation was achieved under isocratic elution by using a C18 column (100 x 4mm, 3 mu m) and a mixture of acetonitrile and phosphoric acid solution (adjusted to pH 3.0 using triethylamine) (55:45, v/v) at a flow rate of 0.7 mL per minute. The analyte was detected at a wavelength of 254 nm, using a photodiode array detector (PDA). The retention time for TCG was found out to be about 3.5 min. As required by the International Conference on Harmonization guidelines, the drug was exposed to different stress conditions; including hydrolysis (acid, alkaline), oxidation, photolysis and thermal degradation. This currently developed method was validated by evaluating the specificity, linearity, precision, accuracy, robustness, and system suitability. The method was determined to be linear in a drug concentration range of 0.5-200 mu g/mL with the correlation coefficient of 0.9996. The proposed method was applied successfully to the analysis of TCG in spiked human plasma with good recovery. The method can successfully applied for determination of TCG in pharmaceutical formulation and spiked plasma samples.Publication Metadata only LIQUID CHROMATOGRAPHIC ANALYSIS OF CAROTENOIDS IN FOODS(2019-06-01) Tekkeli, Serife Evrim Kepekci; DİNCEL, DEMET; Onal, Cem; Onal, Armagan; Sagirli, Olcay; DİNCEL, DEMET; TEKKELİ, ŞERİFE EVRİMCurrent scientific studies indicate that carotenoids (CRTDs) are beneficial for maintaining health and lowering the risk of different pathologies. Considering the increasing role of carotenoids in healthcare, determination of carotenoid content of foods become important. Mostly, the analytical procedures that are used for this aim, are based on extraction techniques followed by different analytical procedures, especially high performance liquid chromatography. In this publication, a review of various analytical techniques developed for the determination of carotenoids in different food commodities starting from 2006 up to now, has been presented.Publication Metadata only Spectrofluorimetric determination of benidipine in pharmaceutical preparation and spiked plasma samples using 7-fluoro-4-nitrobenzo-2-oxa-1,3-diazole(2019-01-01T00:00:00Z) TEKKELİ, ŞERİFE EVRİM; Onal, Cem; TEKKELİ, ŞERİFE EVRİMA new spectrofluorimetric technique was produced for the analysis of benidipine (BDP) in tablets and spiked plasma samples. The developed method was based on coupling between Benidipine, (a secondary amine group), and 7-fluoro-4-nitrobenzo-2-oxa-1,3-diazole (NBD-F) forming fluorescent dervatived as a NBD-Benidipine. The reaction was occured by using pH 8.5 buffer solution to form fluorescent derivatives that are measured lambda(em): 550 nm and lambda(ex): 465 nm. A variable parameters effecting on the derivatization process were studied. The calibration graph was linear in the range of 10-200 ng mL(-1). LOD and LOQ values were a 0.445 ng mL(-1) and 1.348 ng mL(-1), respectivelly. The developed method was applied to BDP in commercially available film tablets. An average recovery was found as 99.80% without interference from the available excipients. Besides, the fluorimetric technique was also succesfully applied to spiked human plasma.Publication Metadata only Stability-indicating ultra-fast liquid chromatographic analysis of maprotiline in pharmaceutical formulations(2019-07-01T00:00:00Z) TEKKELİ, ŞERİFE EVRİM; Onal, Cem; TEKKELİ, ŞERİFE EVRİMThis current study aimed to develop a simple, fast, and reproducible isocratic reverse-phase ultra-fast liquid chromatographic (RP-UFLC) method to detect and quantify maprotiline hydrochloride (MAP) in bulk drug and pharmaceutical formulations. Chromatographic separation was accomplished on a C18 column (100 x 4mm, 3 mu m) under isocratic elution with the use of a binary solution of acetonitrile and phosphate buffer at a pH of 7 (75 : 25, v/v) and a flow rate of 0.4 mL per minute at 215 nm. The linearity was excellent in the concentration range of MAP from 0.1 to 1.5 mu g/mL with a regression coefficient of 0.9996. The proposed method was validated with the respective ICH guidelines. The drug was subjected to hydrolytic, acidic, basic, thermal, photolytic, and oxidative stress conditions as required by the ICH regulation. The method was found to be suitable for use in routine practice to analyze MAP in the pharmaceutical dosage form.Publication Metadata only A Review of Current Methods for the Determination of Acrylamide in Food Products(2012-02-01) Tekkeli, Serife Evrim Kepekci; Onal, Cem; Onal, Armagan; TEKKELİ, ŞERİFE EVRİMAcrylamide (AA) is a potentially carcinogenic substance which is formed during heating of food products containing carbohydrates and asparagine. It was first detected in food products in 2002. Since that time, several analytical methods have been made available for the quantification of AA in various foods. Starting from the announcement in 2002, occurrence, formation, chemistry, toxicology, and potential health risk in the human diet have been investigated and methods of analysis have been reviewed in many articles. In this paper, current information and analytical methods for the determination of AA have been reviewed.Publication Metadata only Ultra fast liquid chromatographic analysis of nonsteroidal anti-inflammatory drugs with fluorimetric detection in tap water, urine, and pharmaceutical samples(2022-06-01T00:00:00Z) Onal, Cem; TIRIS, GİZEM; Tekkeli, Evrim Kepekci; Onal, Armagan; TIRIS, GİZEM; TEKKELİ, ŞERİFE EVRİMA novel analytical method based on ultra-fast liquid chromatography using fluorimetric detector was developed and validated for determination of non-steroidal anti-inflammatory drugs (NSAIDs) (ibuprofen (IBP), etodolac (ETD), dexketoprofen (DKP), sodium diclofenac (SDCF), and naproxen (NPX) in tap water, urine and pharmaceutical samples. Precolumn derivatisation of targeted NSAIDs was carried out with 4-bromomethyl-7-methoxy coumarin (BrMmC) using dibenzo-18-crown-6-ether as reaction catalyst leading to the formation of a fluorescent compound. The obtained fluorescent compound of NSAIDs were measured at excitation wavelength as 325 nm, and emission wavelength of 395 nm. Optimum analytical conditions were carefully studied and improved. C18 column, with the dimensions of 4.0 x 100 mm and 3 mu m particle size, was used. Gradient elution with methanol: water 40:60; v/v (eluent A) and acetonitrile 100% (eluent B) were used as mobile phase and flow rate of 0.4 mL/min. The linearity range of the analytes were between 0.01-10.0 mu g mL(-1). Recovery values obtained from pharmaceutical preparations were found as 100.04%, 99.99%, 100.09%, 99.98% and 100.47% for IBP, ETO, DKP, SDCF, NPX, respectively. LOD values were found to vary between 0.00009 mu g mL(-1) and 0.00048 mu g mL(-1) in tap water, urine and pharmaceutical samples. The optimised technique was successfully applied for the determination of NSAIDs in tap water, urine, and pharmaceutical specimen. The specified NSAIDs were not found in real tap water samples.