Volume 31, Issue 3-4

Ion mobility spectrometry is a well-known technique used to analyze trace gases in ambient air. Typically, it works by employing a radioactive source to provide electrons with high energy to ionize the analytes in a series of chemical reactions. During the past ten years non-radioactive sources have been one of the subjects of interest in ion mobility spectrometry, initially in order to replace radioactive sources as a result of general security and regulatory concerns. Among these non-radioactive sources especially pulsed sources have recently been shown to additionally improve the analytic information provided by ion mobility spectrometers. In this review we will describe the progress regarding the application of pulsed non-radioactive electron sources in ion mobility spectrometry and show the recent analytical advances that have been achieved by using pulsed electron beams.

Because of their high surface-to-volume ratio, easy surface modification, and simple synthesis methods, gold nanoparticles (AuNPs) are becoming an attractive material as an alternative to conventional solvent extraction and solid-phase extraction column for the selective extraction and enrichment of target analytes from a large sample volume. Through covalent bond formation (Au-S bonds), electrostatic attraction, hydrophobic adsorption, and molecular recognition, AuNPs have been applied successfully to the extraction/removal of a variety of compounds from biological fluids and environment waters, including thiol-containing compounds, peptides, proteins, heavy metal ions, polycyclic aromatic hydrocarbons, and melamine. This review summarizes the recent advances in properties, synthesis, and surface modification of AuNPs for the preconcentration of biomolecules and environmental pollutants.

Owing to the small size, high surface-to-volume ratio, and good biocompatibility, silica nanoparticles (SiNPs) have become the normally used carrier for biomolecule immobilization. Label-based detection techniques have been used extensively for a wide range of applications in biological analysis. Organic dye, enzyme, electroactive species, and quantum dots (QDs) with unique optical and electrochemical performances have been used as probes for chemical and biological analysis. The common problem is that only a limited amount of probes can be linked to a biomolecule, which limited the extensive use of these probes in trace amounts of analyte detection. New technologies can provide efficient means to carry them with SiNPs, which possess a three-dimensional network suitable for load or encapsulating a large amount of probes. As a result, composite SiNPs can improve the detection sensitivity significantly because they carry a large amount of probes, which is beneficial for trace analysis. Also, SiNPs are nontoxic, highly water soluble, suitable for many biomolecules to conjugate, and increase the chemical and physical stability of the probes, which is very important for biological analysis. The goal of this review is to describe recent progress in the methods that SiNPs are used as a carrier of dyes, QDs, and enzyme and their application in biological analysis. Among these, SiNPs as a biolabel reagent for signal amplification in immunoassay, DNA, protein, and small molecule detection are the main topic in this review. We focus on two types of methods of carrying signal probes with SiNPs. One is to modify probes on the outer surface of the SiNPs and another is to encapsulate signal probes into the SiNPs. Particular attention is paid to update reported advances since 2009.

Poly(dimethylsiloxane) (PDMS)-based microfluidic systems have been gaining popularity in various applications, particularly for biological analyses because of their non-toxicity, easy fabrication, practical scalability, optical transparency, and low cost. However, because of the inherent hydrophobicity of PDMS-based material, biological samples easily and strongly interact with PDMS surfaces in biological environments, which prevents the immediate use of PDMS-based microfluidics without any surface processing. To date, various surface modification methods and different materials have been utilized to improve the repelling properties of the PDMS surface and to introduce new functional groups. Based on the recent advances in this field, we outline the main strategies utilized in PDMS surface modification in this review. We also present several applications of modified PDMS surfaces in biological analysis, such as biomolecule separation, immunoassay, cell culture, and DNA hybridization.

The new specific metal sensors for copper, zinc, nickel, cobalt, iron, arsenic, antimony, bismuth, vanadium, molybdenum, selenium, and lead were synthesized by using N -phenyl[1,2 methane fullerene C60]C61 complexes. The metal sensors were characterized by pH range, electrode response, response time, and associated metals. The limit of detection of the sensors was found to range between 3×10 -7 and 5×10 -7 , with lifetime between 6 and 8 months. These metal sensors were used for the detection and quantitative determination of trace metal impurities in drugs and pharmaceuticals.

A simple, sensitive and selective spectrophotometric method is proposed for rapid and direct determination of nitrate in small volumes of natural surface waters (maximum 2.0 ml), and optimal experimental conditions, along with other analytical parameters, have been evaluated. The method is based on the reaction between nitrate and chromotropic acid, in concentrated sulfuric acid media (95%), when a yellow colored product is obtained. The visible spectra of this reaction product, recorded against a blank solution, show a maximum at 412 nm, and the absorbance remains stable for at least 24 h. The method allows the nitrate determination over the range 0.50–11.00 mg l -1 , with a molar absorptivity of 3.837×10 4 l mol -1 cm -1 and a detection limit of 0.12 ppm. The interferences caused by several common ions (K + , NH 4 + , Na + , Ca 2+ , Mg 2+ , Al 3+ , Cl - , NO 2 - , HCO 3 - , CO 3 2- , H 2 PO 4 - , HPO 4 2- ) which are present in most natural surface waters were determined. The validation of the spectrophotometric method was done by comparing the nitrate content obtained by the proposed method with those obtained by using the standard method with sulphosalicylic acid, for all studied types of waters (drinking water, tap water, river water and sea water). The results show that the proposed method can be successfully used for direct determination of nitrate in small volumes of natural surface waters (maximum 2.0 ml). The main advantage of this method is that the colored reaction product appears immediately after mixing the reagents; other intermediary steps are not necessary.