Liquid Chromatography Analysis of Reactive Oxoammonium Cations

This study presents the first liquid chromatography method for the quantitative and qualitative analysis of highly reactive oxoammonium cations based on a simple derivatization reaction. Rapid 1,2-electrophilic addition reactions with olefins were used to transform these reactive species into analyzable derivates. Three model substances were chosen to represent each of the main application fields of oxoammonium cations and to demonstrate the versatility of the method. The measuring protocol was validated according to the ICH and USP guidelines. The method revealed an excellent linearity (R2 = 0.9980–0.9990) with a low limit of detection (0.16–0.14 mmol L−1) and a low limit of quantification (0.55–0.43 mmol L−1). The protocol was finally used to determine the oxoammonium cations in the presence of their corresponding radical, showing a robustness against impurity concentration of up to approx. 30%.

Analysis of neurotransmitter catecholamines and related amines in human urine and serum by chromatography and capillary electrophoresis with 1, 3, 5, 7-tetramethyl-8-(N-hydroxysuccinimidyl propionic ester)-difluoro-boradiaza-s-indacene

Two sensitive and effective methods were developed for the detection of catecholamines and related biogenic amines (dopamine, epinephrine, norepinephrine, serotonin, levodopa and tyramine) using high performance liquid chromatography with fluorescence detection and capillary electrophoresis with laser-induced fluorescence detection. A BODIPY fluorescent dye, 1, 3, 5, 7-tetramethyl-8-(N-hydroxysuccinimidyl propionic ester)-difluoroboradiaza- s-indacene was used as pre-column derivatization reagent. The separation and derivatization conditions were optimized in detail. In high performance liquid chromatography with fluorescence detection method, the derivatization reaction was completed at 35 °C for 20 min. At the wavelength of λex/λem = 493 nm/513 nm, dopamine, epinephrine, norepinephrine, and levodopa derivatives achieved baseline separation within 15 min. The limits of detection (S/N = 3) were 1.0, 2.0, 5.0, and 0.5 nmol/L, respectively. In capillary electrophoresis with laser-induced fluorescence detection method, the derivatization reaction was completed at 25 °C for 20 min. Serotonin, tyramine and dopamine derivatives reached baseline separation within 10 min at the wavelength of λex = 473 nm. The limits of detection (S/N = 3) for serotonin, tyramine, and dopamine were 0.3, 0.02, and 0.2 nmol/L, respectively. The amino compounds in human serum and urine samples were detected successfully, and the recoveries were 93.3%–106.7% and 91.0%–103.1%, respectively.

Determination of Lisinopril in Pure and Tablet form by Using 2-Hydroxynaphthaldehyde as Derivatizing Reagent

An easy, sensitive and accurate spectrophotometric method has been developed for the determination of Lisinopril (LNP) in pure and tablet formulations based on derivatization reaction with 2-hydroxynaphthaldehyde (2HNA). The derivatization reaction was carried out in methanol solvent at pH-5.5 at 95±2C for 15 min. The linear calibration curve was obtained that obeyed the Beer’s law within the concentration range 5-50 μgmL-1 of LNP at 433 nm with a coefficient of determination R²=0.996. The recovery was in the range from 98.25-101.82 with molar absorptivity of drug 9×103 mole-1cm-1. The method was accurate and precise (intra-day variation 0.05-0.97% and inter-day 0.07-1.6%), with limit of detection (LOD) and limit of quantification (LOQ) 0.264 μgmL-1 and 0.8 μgmL-1, respectively. No interferences from the excipients were detected. The method was applied for the rapid analysis of LNP in pharmaceutical products.

Evaluation of Different Brands of Cefixime Available in Pakistan by Newly Developed Spectrophotometric Method

A fast, simple and valued method is developed to observe the quality and quantity of different pharmaceutical brands of cefixime. A spectrophotometric method has been developed for analysis of cefixime (CFX) by reacting with 4-dimethylamino benzaldehyde (DAB) as derivatizing agent. The molar absorptivity of CFX-DAB, newly synthesized derivative was calculated as 3.2 x 105 L.mole-1cm-1 and λ maximum was 393 nm. The calibration curve was developed in range of 5-25 µg.mL-1as this concentration followed beers law. The derivatization reaction is stable and didn’t show any difference in absorbance with radiation interaction for up to one day. The percentage recovery of CFX was checked and calculated in different pharmaceuticals was within 95 to 99.5% with RSD value calculated in between RSD 0.69-0.96% (n=3), respectively. This newly developed and validated procedure was proved to be accurate and precise for the analysis of CFX. This method was successfully applied to check amount of CFX from 7 different brands of pharmaceutical preparations commercially available in Pakistan.

Synthesis, Properties, and Derivatization of Poly(dihydrogermane): A Germanium-based Polyethylene Analogue

<div> <div> <div> <p>Polygermanes are germanium-based analogues of polyolefins and possess polymer backbones made up catenated Ge atoms. In the present contribution we report the preparation of a stable germanium polyethylene analogue – polydihydrogermane (i.e., (GeH2)n) – via two straightforward approaches that involve topotactic deintercalation of the CaGe Zintl phase. The resulting (GeH2)n possess morphologically dependent chemical and electronic properties and thermally decompose to yield amorphous hydrogenated Ge. We also show that the resulting (GeH2)n provide a platform from which functionalized polygermanes can be prepared via thermally-induced hydrogermylation-mediated pendant group substitution. This facile one-step derivatization reaction exploits Ge–H reactivity and opens the door to a wide array of tailored functional polygermanes. </p> </div> </div> </div>

Synthesis, Properties, and Derivatization of Poly(dihydrogermane): A Germanium-based Polyethylene Analogue

<div> <div> <div> <p>Polygermanes are germanium-based analogues of polyolefins and possess polymer backbones made up catenated Ge atoms. In the present contribution we report the preparation of a stable germanium polyethylene analogue – polydihydrogermane (i.e., (GeH2)n) – via two straightforward approaches that involve topotactic deintercalation of the CaGe Zintl phase. The resulting (GeH2)n possess morphologically dependent chemical and electronic properties and thermally decompose to yield amorphous hydrogenated Ge. We also show that the resulting (GeH2)n provide a platform from which functionalized polygermanes can be prepared via thermally-induced hydrogermylation-mediated pendant group substitution. This facile one-step derivatization reaction exploits Ge–H reactivity and opens the door to a wide array of tailored functional polygermanes. </p> </div> </div> </div>

Synthesis, Properties, and Derivatization of Poly(dihydrogermane): A Gemanium-based Polyethylene Analogue

<div> <div> <div> <p>Polygermanes are germanium-based analogues of polyolefins and possess polymer backbones made up catenated Ge atoms. In the present contribution we report the preparation of a stable germanium polyethylene analogue – polydihydrogermane (i.e., (GeH2)n) – via two straightforward approaches that involve topotactic deintercalation of the CaGe Zintl phase. The resulting (GeH2)n possess morphologically dependent chemical and electronic properties and thermally decompose to yield amorphous hydrogenated Ge. We also show that the resulting (GeH2)n provide a platform from which functionalized polygermanes can be prepared via thermally-induced hydrogermylation-mediated pendant group substitution. This facile one-step derivatization reaction exploits Ge–H reactivity and opens the door to a wide array of tailored functional polygermanes. </p> </div> </div> </div>

Sensitive and Fast Determination of Ceftiofur in Honey and Veterinary Formulation by HPLC-UV Method with Pre-column Derivatization

A novel, sensitive and rapid high performance liquid chromatography (HPLC) method for the determination of ceftiofur by pre-column derivatization with 1,2-naphthoquinone-4-sulfonate. Analysis was performed within 5 min on a Kinetex C18 column based on core-shell technology. The mobile phase composed of acetonitrile-water (50:50, v/v) pumped isocratically at a flow rate of 1.0 mL/min under UV detection at 254 nm. The factors affecting the derivatization reaction and separation conditions were carefully evaluated and optimized. The method was linear over the concentration range of 45–450 ng/mL with a limit of detection of 3.29 ng/mL and limit of quantitation of 10.97 ng/mL. The new method was successfully applied for the analysis of ceftiofur in the veterinary formulation and honey with average recoveries of 100.78% and 98. 83%, respectively. The present method is suitable and favorable for the analysis of ceftiofur on account of its sensitivity, rapidity and cost-effectiveness. In addition, it could have significant application for the determination of ceftiofur in other food products.