Determination of tobramycin in human serum by capillary electrophoresis with contactless conductivity detection.
ABSTRACT A study on the determination of the antibiotic tobramycin by CE with capacitively coupled contactless conductivity detection is presented. This method enabled the direct quantification of the non-UV-absorbing species without incurring the disadvantages of the indirect approaches which would be needed for optical detection. The separation of tobramycin from inorganic cations present in serum samples was achieved by optimizing the composition of the acetic acid buffer. Field-amplified sample stacking was employed to enhance the sensitivity of the method and a detection limit of 50 microg/L (S/N = 3) was reached. The RSDs obtained for migration time and peak area using kanamycin B as internal standard were typically 0.12 and 4%, respectively. The newly developed method was validated by measuring the concentration of tobramycin in serum standards containing typical therapeutic concentrations of 2 and 10 mg/L. The recoveries were 96 and 97% for the two concentrations, respectively.
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ABSTRACT: Cell culture has replaced many in vivo studies because of ethical and regulatory measures as well as the possibility of increased throughput. Analytical assays to determine (bio)chemical changes are often based on end-point measurements rather than on a series of sequential determinations. The purpose of this work is to develop an analytical system for monitoring cell culture based on sequential injection-capillary electrophoresis (SI-CE) with capacitively coupled contactless conductivity detection (C(4)D). The system was applied for monitoring lactate production, an important metabolic indicator, during mammalian cell culture. Using a background electrolyte consisting of 25mM tris(hydroxymethyl)aminomethane, 35mM cyclohexyl-2-aminoethanesulfonic acid with 0.02% poly(ethyleneimine) (PEI) at pH 8.65 and a multilayer polymer coated capillary, lactate could be resolved from other compounds present in media with relative standard deviations 0.07% for intraday electrophoretic mobility and an analysis time of less than 10min. Using the human embryonic kidney cell line HEK293, lactate concentrations in the cell culture medium were measured every 20min over 3 days, requiring only 8.73μL of sample per run. Combining simplicity, portability, automation, high sample throughput, low limits of detection, low sample consumption and the ability to up- and outscale, this new methodology represents a promising technique for near real-time monitoring of chemical changes in diverse cell culture applications.Journal of Chromatography A 11/2013; · 4.61 Impact Factor
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ABSTRACT: Methods were developed to determine amikacin and urea in bronchial epithelial lining fluid of neonates. Urea was determined as ammonium by capillary electrophoresis in combination with capacitively coupled contactless conductivity detection (CE-C4D). The ammonium was produced by enzymatic conversion of urea with urease enzyme. The background electrolyte (BGE) contained 30 mM malic acid, adjusted to pH 4.1 by l-arginine, and 10 mM 18-Crown-6. Lithium was used as internal standard. A +30 kV was applied on a fused silica capillary with 75 μm internal diameter (ID) and total length of 65 cm (41 cm to C4D detector). The optimized separation was obtained in <3 min with good linearity (R 2 = 0.9998) for urea concentrations ranging from 0.6 to 24 mg L−1. It also shows a good repeatability expressed by the RSD which is 0.7 and 1.3 % for intraday and interday precision, respectively. The LOD and LOQ are 0.14 and 0.5 mg L−1 respectively. As the CE-C4D method was not sensitive enough for amikacin, the latter was determined using liquid chromatography combined with pulsed electrochemical detection (LC-PED). The LOQ for amikacin base was found to be 0.06 mg L−1. In addition, the linearity was good (R 2 > 0.995) as well as the repeatability (RSD = 0.1 %, n = 3). For both the CE and LC method, no interference of matrix components was observed and the recoveries were found to be close to 100 %.Chromatographia 75(13-14). · 1.37 Impact Factor
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ABSTRACT: In this study, we developed quartz crystal microbalance (QCM) nanosensor for the real-time detection of tobramycin (TOB). Firstly, the modification of gold surface of QCM chip was performed by self-assembling monolayer formation of allyl mercaptane to introduce polymerizable double bonds on the chip surface. Then, TOB imprinted poly(2-hydroxyethyl methacrylate–methacryloylamidoglutamic acid) [p(HEMA–MAGA)] film was generated on the gold surface. The nonmodified and TOB-imprinted p(HEMA–MAGA) surfaces were characterized by using atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy, ellipsometry and contact angle measurements. The proposed method was validated according to the ICH guideline. The linearity range and the detection limit (S/N=3) were obtained as 1.7×10−11–1.5×10−10 M and 5.7×10−12 M, respectively. The developed method was applied to pharmaceuticals, and food samples such as chicken egg white and milk extract for the determination of TOB. In addition, association kinetics analysis and isotherm models were applied to the data to explain the adsorption process that took place.Talanta 03/2014; 120:318–324. · 3.50 Impact Factor