Current Analytical Chemistry - Volume 7, Issue 2, 2011

Carbon nanotubes paste electrodes (CNTPE) were prepared using carbon nanotube and mineral oil at different compositions. The carbon nanotubes/mineral oil content in the paste electrode was evaluated using cyclic voltammetry which was 60% (w/w) carbon nanotube. This electrode was characterized by SEM and EIS. The SEM results showed that CNTS structure is not modified by maceration process. From EIS analysis it is possible to observe that the electron transfer reaction is faster in the CNTs presence compared to graphite carbon. CNTPE with 60% (w/w) was used in the determination of rutin in pharmaceutical formulations. Using the differential pulse voltammetric (DPV) procedure, a linear analytical curve was observed in the 1.99x10-7- 9.99x10-6 mol L-1 range with detection limit of 3.39x10-8 mol L-1. The determination of rutin in pharmaceutical formulations showed to be in agreement with the standard spectrophotometric method, AOAC Method, with 95% confidence level and recoveries between 99.2 and 100.5%. The excellent results obtained suggest that the CNTPE 60% (w/w) is suitable for the determination of rutin in pharmaceutical formulations.

Feedstock recycling of plastics wastes by pyrolysis is adequate for obtaining valuable oil. However, thermal decomposition products of the halogen containing components of the plastics are contaminating the pyrolysis oil. In this work, pyrolysis-gas chromatography-mass spectrometry combined with online catalytic conversion has been applied to study the activity of Na-zeolite catalysts for dehalogenation of chloro- and bromo-hydrocarbons in pyrolysis oil of poly(vinylbenzyl chloride), polychloroprene, polychlorostyrene and polybromostyrene. GC-MS analysis of the products helped to recognize catalytic reactions of halogenated alkyl, alkenyl and aromatic hydrocarbons over three sodium zeolites, two of faujasite (X and Y) and one of beta structure. It was concluded that chlorine is completely eliminated from alkyl and alkenyl chloride compounds over all the three investigated zeolites. However, chlorine and bromine substituent of aromatic rings split off only partially: 6, 15 and 17% dechlorination and 14, 31 and 29% debromination of chloro- and bromobenzenes have been observed over X, Y and β zeolite, respectively.

Anti-diuretic peptides are widely used for the control of body water balance. With the growing concerns on their pharmacological characteristics and clinical safety, there is an increasing request of sensitive, selective and robust analytical assays for the determination of anti-diuretics in biological samples. This article provides a perspective review of various methodologies developed and validated in the past, including immunoassay (IA), high performance liquid chromatography (HPLC) and capillary electrophoresis (CE), with detections of radio, UV, fluorescence and mass spectrometry. Systematic description of each technique was given and emphasis was laid on the problems encountered with each assay. Despite the infrequent application of mass spectrometry in anti-diuretics quantitative analysis, it was highlighted here for its remarkable sensitivity and selectivity. The ultimate aim of this review is to demonstrate the analytical options of peptide determination and promote the quantification of peptide-like drugs and biomarkers in respect to fast-expanding peptide market and therapeutics.

An electroanalytical method was developed for the direct quantitative determination of Acyclovir (Acy) in spiked human urine base on its oxidation behavior. The electrochemical oxidation and determination of Acy were easily carried out on ultra trace graphite electrode (UTGE) and glassy carbon electrode (GCE) using a variety of voltammetric techniques. The electrochemical measurements were carried out on these electrodes in various buffer solutions in the pH range of 3.66 to 9.08 by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The best results for the quantitative determination of Acy were obtained by DPV technique in 0.2 M acetate buffer (pH= 4.66). In this acidic medium, one irreversible anodic peak was observed. The anodic peak current and peak potential depend on pH and scan rate were studied. The diffusion controlled nature of the peak was established. Acy was determined in the concentration range from 4×10-6 to 7×10-5 molL-1 for UTGE and 2.0×10-6 to 1.0×10-4 molL-1 for GCE by the applied electroanalytical procedure. Limit of detection (LOD) and limit of quantification (LOQ) were obtained as 1.0×10-6 and 3.3×10-6 molL-1 on UTGE and 3.5×10-7 and 1.2×10-6 molL-1 on GCE, respectively. Repeatability, precision and accuracy of the developed technique were checked by recovery studies in spiked urine.

A solid state silver selective poly (vinyl chloride) (PVC) membrane electrode was developed by using recently synthesized [N, N'-ethylenebis-(3-methoxy salicylaldimine)] as an active component of the membrane. The best sensitivity and selectivity for Ag+ ions were obtained for the electrode membrane containing ionophore-NPOE-PVC and KTpClTB in composition of 4:62:33:1 (w/w). The proposed electrode had a Nernstian response (56.0 mV/decade) to Ag+ within the concentration range 1.0 ×10-6 to 1.0×x10-1 mol L-1and with a detection limit of 8.3×10-7 mol L-1. The electrode worked well between pH 3.0 and 8.0 and had a fast response time of 15 s. The electrode was used along 3 months without any significant change in its sensitivity. Potentiometric performance of the electrode in partially non-aqueous medium (up to 10 % (v/v) alcohol) was found satisfactory. The electrode was successfully used in the potentiometric titration of silver ions with standard solution of potassium iodide, and in the direct determination of silver ion in spiked waste water and photographic film developing solutions.

A solid phase preconcentration procedure is described by using Penicillium digitatum loaded on pumice stone for the determination of Co(II), Fe(III) and Ni(II) in water and vegetables samples by flame atomic absorption spectrometry (FAAS). Experimental variables, including pH, amount of solid-phase, eluent type and flow rate of sample solution were optimized for quantitative recovery of the analytes. The effect of interfering ions on the recoveries was also investigated. Under the optimum conditions, recoveries for Co(II), Fe(III) and Ni(II) were 100±2%, 98±2% and 99±2%, respectively, at 95% confidence level, for spiked water samples. The analytical detection limits were 1.38, 1.88 and 1.56 ng mL-1 for Co(II), Fe(III) and Ni(II), respectively. The accuracy of the method was verified by the analysis of certified reference material (Tea leaves powder, GBW-07605) and spiked samples. The method was successfully applied to the determination of analytes in parsley, carrot, thermal water and tap water samples.

Numerous biologically active compounds are intuitively produced by humans and are present in the environment. Their fate and the occurrence of their metabolites still remain a great challenge for environmental analysts and risk assessors. There are a lot of different analytical approaches leading to the determination of residues of pharmaceuticals used both by humans and for veterinary purposes. However, the majority of known analytical approaches are based on the application of indirect methods where proper sample preparation (isolation/preconcentration of analytes prior to final determination of analytes) plays a vital role. The attention of analysts is oriented towards the direct methods when a special pretreatment of handled samples and during analysis is not needed. These procedures are fulfilling the requirement of sustainable development and can be classified as “green” analytical procedures. Immunoanalytics can be treated as a typical example of this approach. This paper presents a review of one of the most versatile and direct method of analysis, immunoassaying, focused on the application and determination of pharmaceuticals and their residues' concentration/presence in different environmental compartments.