Current Analytical Chemistry - Volume 11, Issue 3, 2015

Certified reference materials (CRMs) play vital roles in method validation and quality assurance of assessment measurements. In this paper, a new CRM for sulfamethoxazole (SMZ) was prepared. Purity determination and uncertainty evaluation methods were developed using mass balance (MB) and differential scanning calorimetry (DSC) methods. Impurities including moisture, volatile components, and inorganic components were accounted for and deducted from 100% using the MB method. Results were consistent between DSC and MB. Certied value of SMZ was 991.6 ± 4.6 mg g-1 (k = 2, P = 0.95). This new CRM can be used to validate analytical methods, improve the accuracy and comparability of measurement data, establish metrological traceability of analytical results, and control the quality of SMZ in relevant pharmaceutical formulations.

In recent years, material characterization with functional properties has been a focus of interest to be used in devices like biosensors; in this work a photochromic material was used as an (essential) main component of an optical transducer. The goal of this article was to develop an experimental protocol for building an optical transducer based on a spiropyran, in recognition of properties (features) they manifest for binding molecules to different charges, to prove this binding the enzyme glucose oxidase was immobilized to the modified matrix. A functionalized glass slide that acts as this matrix was activated using carbodimide as a coupling agent. Each stage including the cleaning, the silanization, the coupling product from the matrix with spiropyran and the enzyme immobilization was analyzed by applying UV/Vis and Infrared spectroscopy, together with X-ray Photoelectron Spectroscopy and Atomic Force Microscopy.

L-glutathione decorated Mn doped ZnS QDs (GSH-Mn: ZnS QDs) were synthesized in aqueous solution. The characterization of as-prepared QDs was carried out through fluorescence, ultraviolet-visible absorption (UV-vis), TEM and Fourier transform infrared spectroscopy (FTIR). Pb2+ had obvious quenching effect on the fluorescence intensity of GSH-Mn: ZnS QDs. Under optimal factors, a nice linear relationship between the fluorescence response and the concentration of Pb2+ was established from 0.025µM to 15.5µM range with a correlation coefficient of 0.9981 and the detection limit is 0.018µ. This probe was triumphantly made use of the detecting of Pb2+ in tap and pond water. At the same time, it was preliminary inferred that the fluorescence quenching way of Pb2+ to QDs was dynamic quenching. The present study provides a simple, low-cost route toward production of GSH-Mn: ZnS QDs for chemo/bio sensing and other adhibition.

Background: Tadalafil is an oral drug that is used for treating erectile dysfunction (impotence) and pulmonary arterial hypertension. It relaxes muscles and increases blood flow to particular areas of the body. Objective: The present study was aimed to investigate the different pharmacokinetic parameters of the two different formulations of Tadalafil (CAS no. 171596-29-5), one is conventional tablet dosage formulation and other is ODS (Orally Disintegrating Strips) each of which contains 20 mg of tadalafil. Materials and Methods: A simple, rapid bio-analytical LC-MS/MS method with appropriate sensitivity, selectivity, accuracy and precision was developed and validated to quantify tadalafil in human plasma. Sildenafil was used as Internal Standards (IS). Electrospray ionization (ESI) MS–MS was used to analyze tadalafil. A high proportion of organic solvent Methanol: 10mM Ammonium Acetate in water (pH 6.38):: 9:1 (v/v) had been found best to coelute both substances with a flow rate of 0.5 mL/min using Phenomenex Gemini C18 coloumn (4.6 mmx50 mm, 5 µm). Results: The pharmacokinetic data of tadalafil in healthy human subjects of two different formulations show that the new ODS (Orally Disintegrating Strips) formulation is bioequivalent with the conventional tablet dosage formulation. Both the formulations were well tolerated with no observed adverse reactions.

In this research, greener chromatography employing a more eco-friendly microemulsion mobile phase was utilized for the analysis of rosiglitazone (ROS) and glimepiride (GLM) in rat sera. ROS, GLM, and darfenacin (an internal standard) were detected using UV wavelength of 237 nm. HPLC analysis by using a monolithic column was performed by directly injecting the sample after appropriate dilution with the mobile phase. The chromatographic behavior of these compounds was studied to demonstrate their chromatographic efficiency, retention, and peak symmetry. Regression analyses showed excellent linearity (r = 0.999) over concentrations ranging from 100 to 5000 ng mL-1for both ROS and GLM. The developed method by using rat sera had limits of detection of 40.0 ng mL-1for both drugs. The assay was statistically validated for linearity, accuracy, precision and specificity according to ICH guidelines. The intra- and inter-assay precisions were satisfactory and the accuracy of the method was proved. This assay was successfully applied in a pharmacokinetic study.

Anatase nano titanium oxide was used as a sorbent for the separation and preconcentration of selenium(IV) from liquor. The selenium was determined by hydride generation-atomic fluorescence spectrometry (HG-AFS) with KBH4-HCl. The results showed that the adsorption percentage of selenium( IV) was 92% at pH 4-6, and the elution by NaOH reached 95%. The adsorption equilibrium accorded with the Langmuir isotherm model and the maximum adsorption capacity was 32.17 mg g-1 at 293 K. The detection limit of selenium(IV) (3σ, n = 11) was 0.57 µg L-1 and the relative standard deviation was 7.48%. The process has been successfully applied to the contents determination of trace selenium(IV) in some natural water samples with satisfactory results.

Separation of several isomer groups, i.e. diastereomers such as quinine and quinidine, cinchonine and cinchonidine, R,S-1-(1-naphthyl)-ethanol, R,S-1-(2-naphthyl)-ethanol, and R,S-1,1’- binaphthyl-2,2’-diamine racemates by means of high-performance thin layer chromatography (HPTLC) as well as pressurized planar electrochromatography (PPEC) techniques and carried out with the use of HPTLC RP-2, HPTLC RP-8 and HPTLC RP-18W plates as well as the acetonitrile - buffer mobile phase with hydroxypropyl-β-cyclodextrin (HP- β-CD) or hydroxypropyl-γ-cyclodextrin (HP-γ- CD) as additives in the mobile phase is presented. The influence of such variables as HP-β-CD concentration in the mobile phase, type of the used adsorbent and dimension of cyclodextrin interior (HP-β-CD and HP-γ-CD) on the migration distance of the solute zones is investigated. It has been observed that an increase in the HP-β-CD concentration brings about an opposite effect in the compared techniques and retention of the solutes diminishes in HPTLC, whereas the migration distances of the majority of isomers decrease in PPEC. The type of applied HP-cyclodextrin has a stronger effect on the separation selectivity of compounds in the PPEC system in comparison with the HPTLC system. Since the isomer differentiation mechanism in the PPEC technique is possible due to the two effects (partition and electrophoresis), whereas the HPTLC system employs only partition, changes in the separation selectivity of solutes in both investigated systems are expected and the former system turns out to be better at distinguishing between enantiomers in the R,S-1-(1-naphthyl)-ethanol and R,S-1-(2-naphthyl)-ethanol mixtures in comparison with the HPTLC-system.

In this study, multi-walled carbon nanotubes (MWCNTs) and vitamin B12 (VB12) were fabricated on the surface of glassy carbon electrode (GCE). This modified electrode (MWCNTs/VB12/GCE) was designed to determine p-hydroxyacetophenone (p-HYD) by square wave voltammetry. The MWCNTs/VB12 film was characterized by Electrochemical impedance spectroscopy and Fourier transform infrared spectroscopy, which exhibited excellent electrocatalytic activity toward p-HYD by using square wave voltammetry. The peak current was linear with the concentration of p-HYD over the range of 0.5 - 250 µM with the detection limit of 0. 15 µM (S/N = 3). Furthermore, this proposed sensor has also demonstrated good reproducibility, high stability and excellent anti-interference ability.

In this study the analytical determination of gold and palladium in jewelry alloys was achieved by means of one shot potentiometric titration. The practical aspects of this procedure were investigated and discussed in order to define the optimal conditions for the simultaneous quantitative determination of the two elements using commercially-available equipment (Mettler-Toledo DL-50 automatic titrator and DS500 electrode). The accuracy and precision of the method was tested on several commercial alloys containing large and small amounts of Au and Pd, their content being determined down to 7‰ (Au) and 50‰ (Pd). The relative error of the potentiometric titrations was found to be consistent with the limits accepted for the standard analytical methods (0.5 ‰ Au and 10 ‰ Pd). It is demonstrated that the proposed method can be used as a robust and affordable alternative procedure in the routine analysis of both low and high grade Pd- and Au-bearing alloys.

The flavone C-glycosides in Viola yedoensis have been reported as the major active antiinflammatory, anti-cancer, and antioxidant components. However, due to the difficulty in obtaining standard compounds, little work has been done on the quantitative analysis of the multiple major flavone C-glycosides in V. yedoensis. In this study, a microwave-assisted extraction (MAE) and high performance liquid chromatography-electrospray ionization-mass spectrometry/mass spectrometry (HPLC-ESI-MS/MS) method in the selected reaction-monitoring (SRM) mode was developed and validated for the simultaneous separation and quantification of three major active flavone di-Cglycosides (apigenin 6,8-di-C-β-D-glucoside, apigenin 6-C-β-D-glucosyl-8-C-α-L-arabinoside, and apigenin 6,8-di-C-α-L-arabinoside) in V. yedoensis. The MAE conditions were optimized using an orthogonal design L9 (34). The extraction yields by MAE were the same or even higher than traditional extraction methods. All calibration curves showed good linearity (r2 > 0.9986) over their corresponding test ranges. The LOD ranged from 17 to 34 ng/mL and LOQ ranged from 34 to 68 ng/mL. The intra- and inter-day precisions (%RSD) were within 2.64% for the three analytes. The recovery of the assay was in the range of 97.67-98.93% with RSD values less than 2.54%. The developed HPLC-MS/MS method was used to quantitatively analyze the three di-C-glycosides in 14 batches of V. yedoensis samples. This newly developed HPLC-MS/MS method coupled with MAE is sensitive and accurate for simultaneous determination of multiple flavone C-glycosides in V. yedoensis.