Naizhong Song

Preconcentration procedures for the determination of chromium using atomic spectrometric techniques: A review

Chromium is one of the regulated toxic metals in the environment. Naturally, this element exists mainly in two oxidation: Cr(III) and Cr(VI). In general, Cr(VI) is more toxic than Cr(III). Cr(VI) affects human physiology, accumulates in the food chain and causes severe health problems ranging from simple skin irritation to lung carcinoma. Hence, the determination of chromium traces as well as its speciation in environmental samples is a very important task. In recent years, several preconcentration methods such as coprecipitation, liquid-liquid extraction, dispersive liquid-liquid microextraction, cloud point extraction, and solid phase extraction have been developed and widely used. The aim of this study is to review the recent literature (mainly last 5 years) on the preconcentration technologies those have been used in chromium removal before the determination step by atomic spectrometric techniques. Their advantages and limitations in application are also evaluated.

Highly selective enrichment of phosphopeptides by on-chip indium oxide functionalized magnetic nanoparticles coupled with MALDI-TOF MS

Selective and efficient preconcentration is indispensable for low concentration of phosphopeptides in phosphorylated protein‐related samples prior to MS‐based analysis. Herein, an on‐chip system coupled magnetic SPE with MALDI‐TOF MS was designed. A metal oxide affinity chromatography material, indium oxide, was coated on the surface of Fe3O4 magnetic nanoparticles to prepare the adsorbent, spatially confined with an applied magnetic field. The adsorbent exhibited high selectivity for phosphopeptides in tryptic digests of the mixture of β‐casein and BSA (1:1000) and the mixture of β‐casein, BSA, and ovalbumin (1:100:100). Thanking to the enrichment ability and specificity for phosphopeptides with the adsorbent, the on‐chip magnetic SPE‐MALDI‐TOF MS approach showed high sensitivity with a low detection limit of 4 fmol. In addition, the developed approach was used to analyze phosphopetides in non‐fat milk digests and human serum successfully.

Application of cloud point methodology to the determination of nitroanilines in natural water

We developed a methodology based on cloud point extraction (CPE) for the determination of three nitroanilines, p-nitroaniline (PNAL), m-nitroaniline (MNAL), and o-nitroaniline (ONAL). The CPE methodology was coupled with high performance liquid chromatography determinations. Tergitol 15-S-7, an environmentally friendly nonionic surfactant, was employed as the surfactant. To obtain the optimum extraction efficiency, several experimental factors were investigated, including sample pH, salt concentration, surfactant concentration, equilibration temperature, and incubation time. Under the optimized experimental conditions, the linear ranges were 0.06–1, 0.03–1, and 0.01–1 μg mL−1 for PNAL, MNAL, and ONAL, respectively. The limits of detection (LOD) for PNAL, MNAL, and ONAL were 0.013, 0.005, and 0.002 μg mL−1 with the intraday and interday relative standard deviations less than 3.1% and 6.5%. The present method proved to be simple, green, rapid, sensitive, and competitive when used for the determination of nitroanilines in water samples, and the accuracy was assessed through recovery experiments.

Cobalt Phthalocyanine Tetracarboxylic Acid Functionalized Polymer Monolith for Selective Enrichment of Glycopeptides and Glycans

In this study, poly(glycidyl methacrylate‐ethyleneglycol dimethacrylate) monolith functionalized with cobalt phthalocyanine tetracarboxylic acid is prepared. The polymer monolithic material is used for glycopeptides enrichment coupled with MALDI–TOF MS. By taking advantage of cobalt phthalocyanine including hydrogen bonds between isoindole subunits of phthalocyanine and glycans, coordination interaction between cobalt and glycopeptides, the monolithic material is successfully applied to the enrichment of glycopeptides efficiently and selectively. With IgG and horse radish peroxidase as the model glycoproteins, 28 and 17 glycopeptides could be identified respectively after enrichment with the monolith, only four and three glycopeptides could be obtained for direct analysis. The monolith is also employed to the digests mixture of BSA and IgG (50:1, m/m), indicating the high enrichment selectivity of glycopeptides even in the presence of a large interference ratio. The detection limit is determined to be 6.7 fmol, implying that the present method had great potential for trace sample analysis. In addition, the monolith was successfully applied to the enrichment of N‐linked glycans in human serum samples, demonstrating its great potential for the analysis of glycoproteins.

Preparation of carboxylatocalix[4]arene functionalized magnetic polyionic liquid hybrid material for the pre-concentration of phthalate esters

In this work, we designed a novel hybrid material based on the polymerization of an ionic liquid on a magnetic core and further functionalized with carboxylatocalix[4]arene. Scanning electron microscope, transmission electron microscope, Fourier transform infrared spectroscopy, thermal gravimetric-derivative thermogravimetric analysis, energy dispersive X-ray spectroscopy, X-ray diffractometer, and vibrating sample magnetometer were utilized to examine the physicochemical properties of the hybrid material obtained. The material was used as the adsorbent for magnetic solid-phase extraction of phthalate esters. To obtain the maximum pre-concentration efficiency, a series of parameters influencing the extraction efficiency, including sample pH, adsorbent amount, adsorption time, eluent type as well as salt addition, was examined systematically. Under the optimum conditions, a fast and feasible pre-concentration protocol for phthalate esters was established with satisfactory enrichment factors between 158.7 and 191.3. The limits of detection from high-performance liquid chromatographic analysis for the target analytes were in the range of 0.02-0.31 ng mL-1. The wide linear ranges varying from 0.1 to 100 ng mL-1 were achieved with correlation coefficients greater than 0.9977. To evaluate the feasibility of this method, it was successfully applied to analyse phthalate esters in multiple kinds of real samples including tap water, lake water, drinks, tonic lotions, and human serum samples. The results obtained demonstrated that the synthesized magnetic material had potential as a candidate in the pre-concentration field for phthalate esters due to the special properties stemming from its structure and components.

Extraction of bismuth with mixing systems of sec-octylphenoxy acetic acid and 1,10-phenanthroline

ABSTRACT sec-Octylphenoxy acetic acid and 1,10-phenanthroline were employed for the extraction of bismuth from chloride medium, showing evident synergistic effects on bismuth extraction. Stoichiometry of the synergistic extraction was determined, giving a logarithm value of equilibrium constant of 6.75, which was much higher than those obtained by single sec-octylphenoxy acetic acid or 1,10-phenanthroline. Thermodynamic studies indicated that the synergistic extraction was an endothermic and spontaneous process. Moreover, antagonistic effects were found when the mixture was employed for lead extraction, demonstrating its potential to be applied to the separation of bismuth and lead at low mole fractions of sec-octylphenoxy acetic acid.