Alaa A. Salem

Spectrophotometric and fluorimetric determination of diazepam, bromazepam and clonazepam in pharmaceutical and urine samples

New spectrophotometric and fluorimetric methods have been developed to determine diazepam, bromazepam and clonazepam (1,4-benzodiazepines) in pure forms, pharmaceutical preparations and biological fluid. The new methods are based on measuring absorption or emission spectra in methanolic potassium hydroxide solution. Fluorimetric methods have proved selective with low detection limits, whereas photometric methods showed relatively high detection limits. Successive applications of developed methods for drugs determination in pharmaceutical preparations and urine samples were performed. Photometric methods gave linear calibration graphs in the ranges of 2.85-28.5, 0.316-3.16, and 0.316-3.16 microgml-1 with detection limits of 1.27, 0.08 and 0.13 microgml-1 for diazepam, bromazepam and clonazepam, respectively. Corresponding average errors of 2.60, 5.26 and 3.93 and relative standard deviations (R.S.D.s) of 2.79, 2.12 and 2.83, respectively, were obtained. Fluorimetric methods gave linear calibration graphs in the ranges of 0.03-0.34, 0.03-0.32 and 0.03-0.38 microgml-1 with detection limits of 7.13, 5.67 and 16.47 ngml-1 for diazepam, bromazepam and clonazepam, respectively. Corresponding average errors of 0.29, 4.33 and 5.42 and R.S.D.s of 1.27, 1.96 and 1.14 were obtained, respectively. Statistical Students t-test and F-test have been used and satisfactory results were obtained.

Trace determination of β-blockers and β2-agonists in distilled and waste-waters using liquid chromatography-tandem mass spectrometry and solid-phase extraction.

A highly sensitive method for simultaneous determinations of eleven β-blockers and β-agonists in distilled and waste-waters using liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS-MS) was developed, optimized and validated. The method was used for trace determinations of acebutolol, atenolol, metoprolol, propranolol, timolol, nadolol, labetalol, oxprenolol, pindolol, alprenolol and terbutaline. Oasis MCX and Clean Screen cartridges were used for solid phase extractions and an alkaline mixture of dichloromethane-propanol was used as mobile phase. Matrix effect was reduced by using methanol as a pre-eluant for removing co-extractives on the SPE cartridges and by applying the internal standard method for quantification. Using Oasis MCX-SPE cartridges, developed method gave average recoveries of 77.20-97.30% for drugs spiked at 150.00-500.00pg/ml. Intra-day precisions gave RSD of 3.367-12.489% while as inter-day precisions gave RSD of 6.425-19.768%. Detection limits of 0.11-6.74pg/ml and quantification limits of 0.14-22.88pg/ml were obtained. Signals suppression in the range of 4.50-24.50% was recorded due to the matrix effect. Drugs spiked in wastewater at 500.00pg/ml concentrations level and stored at 4°C for 6 days, showed insignificant degradation. Developed method was successfully applied to the analysis of pharmaceutical residues in effluents wastewaters. Five β-blockers and one β-agonists were detected in Al-Ain and Abu Dhabi wastewaters at average concentrations of 3.44-19.05pg/ml. Atenolol was detected at higher average concentration ranged in 125.60-234.28pg/ml. Results obtained suggest that adopted wastewater treatment processes are not enough to degrade these compounds.

Method validation and determinations of levofloxacin, metronidazole and sulfamethoxazole in an aqueous pharmaceutical, urine and blood plasma samples using quantitative nuclear magnetic resonance spectrometry

Selective, rapid and accurate quantitative proton nuclear magnetic resonance (qHNMR) method for the determination of levofloxacin, metronidazole benzoate and sulfamethoxazole in aqueous solutions was developed and validated. The method was successfully applied to the determinations of the drugs and their admixtures in pharmaceutical, urine and plasma samples. Maleic acid and sodium malate were used as internal standards. Effect of temperature on spectral measurements was evaluated. Linear dynamic ranges of 0.50-68.00, 0.13-11.30 and 0.24-21.00 mg per 0.60 mL solution were obtained for levofloxacin, metronidazole benzoate and sulfamethoxazole, respectively. Average recovery % in the range of 96.00-104.20 ± (0.17-2.91) was obtained for drugs in pure, pharmaceutical, plasma and urine samples. Inter and intra-day analyses gave average recoveries % in the ranges 96.10-98.40 ± (1.68-2.81) and 96.00-104.20 ± (0.17-2.91), respectively. Instrumental detection limits ≤0.03 mg per 0.6 mL were obtained for the three drugs. Developed method has demonstrated high performance characteristics for analyzing investigated drugs and their admixtures. Student t-test at 95% confidence level revealed insignificant bias between the real and measured contents of investigated drugs in pure, pharmaceutical, urine and plasma samples and its admixtures. Application of the statistical F-test revealed insignificant differences in precisions between the developed method and arbitrary selected reference methods.

Potentiometric determination of some 1,4-benzodiazepines in pharmaceutical preparations and biological samples

Abstract New, simple, low cost and sensitive ion-selective electrodes are described for the determination of some 1,4-benzodiazepines in their pharmaceutical preparations as well as in biological fluids. Drug-tetraphenylborate and drug-phosphotungstate ion pairs have been prepared and used as electroactive materials. Poly(vinyl chloride) (PVC), and poly(esterurethane)s (UPCLs, UPBA, and UPDEGA) are used as the matrix. The proposed sensors give rapid Nernstian responses for 10−4–10−6 M of the abovementioned drugs in a pH range of 3–7. The membranes developed have potential stability for up to 4 weeks and show high selectivity for the investigated drugs over many interfering ions. The electrodes are used for determining trace amounts of bromazepam, clonazepam and diazepam in their pharmaceutical preparations as well as in biological fluids. For pharmaceutical preparations, the relative standard deviation (RSD) values were in the range, 1.37–4.1, 0.7–2.52 and 0.3–1.2% for bromazepam, clonazepam and diazepam, respectively using the PVC based electrodes, while for the UPBA based electrodes, the (RSD) values were in the range 0.6–3.35, 0.7–2.45 and 0.6–2.41%. For biological samples, the RSD values were 0.64–1.88, 0.37–1.8 and 1.36–3.57% for bromazepam, clonazepam and diazepam, respectively. Comparison of the results obtained using the proposed electrodes with those found using a (HPLC) reference method showed that the ion-selective electrode technique is sensitive, reliable and can be used with very good accuracy and high % recovery without pretreatment procedures of the samples to minimize interfering matrix effects.

New spectrophotometric method for determining nitrogen dioxide in air using 2,2-azino-bis(3-ethyl benzothiazoline)-6-sulfonic acid-diammonium salt and passive sampling.

A new simple and highly sensitive spectrophotometric method for determining nitrogen dioxide in air was developed. The method is based on converting atmospheric nitrogen dioxide to nitrite ions within the IVL passive samplers used for samples collection. Acidifying nitrite ions with concentrated HCl produced the peroxynitrous acid oxidizing agent which was measured using 2, 2-azino-bis(3-ethyl benzothiazoline)-6-sulfonic acid-diammonium salt (ABTS) as reducing coloring agent. A parallel series of collected samples were measured for its nitrite content using a validated ion chromatographic method. The results obtained using both methods were compared in terms of their sensitivity and accuracy. Developed spectrophotometric method was shown to be one order of magnitude higher in sensitivity compared to the ion chromatographic method. Quantitation limits of 0.05 ppm and 0.55 μg/m3 were obtained for nitrite ion and nitrogen dioxid, respectively. Standard deviations in the ranges of 0.05–0.59 and 0.63–7.92 with averages of 0.27 and 3.11 were obtained for determining nitrite and nitrogen dioxide, respectively. Student-t test revealed t-values less than 6.93 and 4.40 for nitrite ions and nitrogen dioxide, respectively. These values indicated insignificant difference between the averages of the newly developed method and the values obtained by ion chromatography at 95% confidence level. Compared to continuous monitoring techniques, the newly developed method has shown simple, accurate, sensitive, inexpensive and reliable for long term monitoring of nitrogen dioxide in ambient air.

Synthesis and antimicrobial activity of 4-trifluoromethylpyridine nucleosides

Abstract 4-Trifluoromethylpyridine derivatives 4–8 represent good candidates for the discovery of new antibacterial agents. Fluorinated pyridine nucleosides 4–7 and non-nucleoside analogues 8a,b were synthesized and evaluated for their antibacterial activities against Staphylococcus aureus, Bacillus infantis, Escherichia coli and Stenotrophomonas maltophilia. The minimum inhibitory concentrations (MICs) of the new nucleosides 4–7 range from 1.3 to 4.9 μg/mL and MICs of fluoroaryl derivatives 8a,b are in the range of 1.8–5.5 μg/mL. Activity of amoxicillin, the reference drug, is 1.0–2.0 μg/mL under similar conditions.

Synthesis and in vitro biological evaluation of new pyrimidines as glucagon-like peptide-1 receptor agonists

The therapeutic success of peptide glucagon-like peptide-1 (GLP-1) receptor agonists for the treatment of type 2 diabetes mellitus has inspired discovery efforts aimed at developing orally available small-molecule GLP-1 receptor agonists. In this study, two series of new pyrimidine derivatives were designed and synthesized using an efficient route, and were evaluated in terms of GLP-1 receptor agonist activity. In the first series, novel pyrimidines substituted at positions 2 and 4 with groups varying in size and electronic properties were synthesized in a good yield (78-90%). In the second series, the designed pyrimidine templates included both urea and Schiff base linkers, and these compounds were successfully produced with yields of 77-84%. In vitro experiments with cultured cells showed that compounds 3a and 10a (10-15-10-9M) significantly increased insulin secretion compared to that of the control cells in both the absence and presence of 2.8mM glucose; compound 8b only demonstrated significance in the absence of glucose. These findings represent a valuable starting point for the design and discovery of small-molecule GLP-1 receptor agonists that can be administered orally.