Resolution of the enantiomers of racemic atenolol, metoprolol, propranolol, and labetalol, commonly used β-blockers, has been achieved by TLC on silica gel plates using vancomycin as chiral impregnating reagent or as chiral mobile phase additive. With vancomycin as impregnating agent, successful resolution of the enantiomers of atenolol, metoprolol, propranolol, and labetalol was achieved by use of the mobile phases acetonitrile-methanol-water-dichloromethane 7:1:1:1 (
), acetonitrile-methanol-water 6:1:1 (
), acetonitrile-methanol-water-dichloromethane-glacial acetic acid 7:1:1:1:0.5 (
), and acetonitrile-methanol-water 15:1:1 (
), respectively. With vancomycin as mobile phase additive, successful resolution of the enantiomers of metoprolol, propranolol, and labetalol was achieved by use of the mobile phases acetonitrile-methanol-0.56 mM aqueous vancomycin (pH 5.5) 6:1:1 (
), acetonitrile-methanol-0.56 mM aqueous vancomycin (pH 5.5) 15:1:2 (
), and acetonitrile-methanol-0.56 mM aqueous vancomycin (pH 5.5)-dichloromethane 9:1:1.5:1 (
), respectively. Spots were detected by use of iodine vapor. The detection limits were 1.3, 1.2, 1.5, and 1.4 μg for each enantiomer of atenolol, metoprolol, propranolol, and labetalol, respectively.
The retention behavior of selected macrocyclic antibiotics (erythromycin, troleandomycin, tylosin, vancomycin, rifamycin B, and rifampicin) has been examined on LiChrospher Si 60 F
HPTLC plates as stationary phase. A wide range of mixtures of alcohols and ketones with hexamethyldisiloxane (HMDSO) in proportions from 0 to 100% (
) and with dimethyl sulfoxide (DMSO) in proportions from 0 to 50% (
) were used as mobile phases. Chromatographic retention data and a possible retention mechanism are discussed.
Authors:Irena Baranowska, Piotr Markowski, Andrzej Wilczek, Magdalena Szostek, and Marlena Stadniczuk
Simple, rapid and selective NP-TLC and RP-TLC methods are described for analysis of l
-arginine, its primary metabolites (l
-arginine, agmatine, putrescine, spermidine, spermine, and creatine) and selected drugs (dexamethasone, prednisolone, furosemide, vancomycin, amikacin, fluconazole, digoxin, captopril, dipyrone, metoprolol, and sildenafil), in different therapeutic groups, in model solutions and in spiked human urine. NP-TLC and RP-TLC methods have been used to study the retention of the substances. A variety of mobile phase systems were evaluated for separation of ARG and its metabolites — methanol-50% acetic acid 3:1 (
) on silica gel and 5% acetic acid-methanol-acetonitrile 50:35:15 (
) on RP-18 — and for separation of the drugs — acetonitrile-water 2:3 (
) on silica gel. The effects on selectivity of the polar modifier of mobile phases were also studied.
Authors:F. Yurt Lambrecht, O. Yilmaz, K. Durkan, P. Unak, and E. Bayrak
Linezolid is the first of new class of antibiotics, the oxazolidinones, and exhibits activity against many gram-positive organisms,
including vancomycin-resistant Enterococcusfaecium, methicillin-resistant Staphylococcusaureus, and penicillin-resistant Streptococcuspneumoniae. Aim of the study: Linezolid was to label with I-131 and potential of the radiolabeled antibiotic was to investigate in inflamed
rats with S. aureus (S.aureus) and sterile inflamed rats with turpentine oil. Linezolid was labeled with I-131 by iodogen method. Biodistribution of [131I]linezolid was carried out in bacterial inflamed and sterile inflamed rats. Radiolabeling yield of [131I]linezolid was determined as 85 ± 1% at pH 2. After injecting of [131I]linezolid into bacterial inflamed and sterile inflamed rats, radiolabeled linezolid was rapidly removed from the circulation
via the kidneys. Binding of [131I]linezolid to bacterial inflamed muscle (T/NT = 77.48 at 30 min) was five times higher than binding to sterile inflamed muscle
(T/NT = 14.87 at 30 min) of rats. [131I]linezolid showed good localization in bacterial inflamed tissue. It was demonstrated that [131I]linezolid can be used to detect S.aureus inflammation in rats.
Graft copolymers of 2-(dimethylamino)ethylmethacrylate (DMAEMA) and acrylic acid (AAc) onto polypropylene films were investigated
for obtaining a pH- and thermo-sensitive material. DMAEMA and AAc were grafted by direct irradiation and pre-irradiation methods,
respectively, using a 60Co γ-source. Due to the acidic and basic nature of the monomers, this novel copolymer corresponds to the class of polyzwitterions.
Their behavior was studied in presence of different buffer solutions from pH 2 to 12 for different grafting percentages (from
9 to 362%) of AAc and keeping the DMAEMA grafting percentage constant. These modified films showed the same critical pH point
at 7.6 in a range of temperatures from 23 to 37 °C. The swelling percentage showed a dependence on AAc content and pH. The
lower critical solution temperature was observed at 36 °C when AAc content was less than 30% of grafting. The grafted films
were characterized by swelling behavior, FTIR-ATR and UV–Vis spectrometry for study of loading and release of vancomycin as
a model drug at room temperature.
Authors:F. Benaskar, A. Ben-Abdelmoumen, N. G. Patil, E. V. Rebrov, J. Meuldijk, L. A. Hulshof, V. Hessel, U. Krtschil, and J. C. Schouten
An extended cost study consisting of 14 process scenarios was carried out to envisage the cost impact of microprocessing and microwaves separately or in combination for two liquid-phase model reactions in fine-chemicals synthesis: (1) Ullmann C–O cross-coupling reaction and (2) the aspirin synthesis. The former, a Cu-catalyzed substitution reaction, was based on an experimental investigation, whereas the latter, a noncatalyzed aromatic esterification reaction, was based on literature data. The cost of 4-phenoxypyridine production, as a pharmaceutical intermediate in the synthesis of vancomycin or vancocin, was compared with that of the synthesis of aspirin, a key example of large-scale fine-chemical production plants. The operating costs in the Ullmann synthesis were found to be related to material-based process (reactant excess, pretreatment, and catalyst synthesis), whereas those in the aspirin synthesis appeared to be related to downstream-based process (workup, waste treatment). The impact of an integrated microwave heating and microprocessing system on profitability was demonstrated with respect to operational cost and chemical productivity. Different modes of microwave heating and catalyst supply were studied and compared with conventional oil-bath-heated systems in batch and continuous processes. The overall costs including profitability breakthrough for a competitive market price of product were obtained from various combinations of heating and processing. In case of the Ullmann synthesis, the CAPEX (capital expenditure) was negligible compared to the OPEX (operational expenditure), whereas in the aspirin synthesis, the CAPEX was found around 40%, both at a production scales of 1–10 kg/day using proposed upscale methods. The source of the catalyst strongly determined the profitability of a continuously operated Ullmann process due to its effect on the chemical performance. Higher energy efficiencies could be attained using single-mode microwave irradiation; however, the energy contribution to the overall cost was found to be negligible. Different scenarios provided a cost-feasible and profitable process; nevertheless, an integrated microwave heating and microflow processing led to a cost-efficient system using a micropacked-bed reactor in comparison to wall-coated microreactor, showing a profit margin of 20%.