A novel platform based on gold nanoparticles chemically impregnated polyurethane foam sorbent coupled ion chromatography for selective separation and trace determination of phosphate ions in water

Per aqueous liquid chromatography of Radix hedysari polysaccharides and Au nanoparticles co-functionalized stationary phase and its application in the determination of iridoids and phenylethanols

BACKGROUND

Hydrophilic Interaction Liquid Chromatography (HILIC) is an outstanding strategy for the challenging analysis of hydrophilic and polar components. Nevertheless, analysis under HILIC mode typically consumes 70%-95 % acetonitrile with the disadvantage of high analytical costs, being environmentally unfriendly and causing biohazards, which is not in line with the concept of green chromatography. Research has shown that Per Aqueous Liquid Chromatography (PALC) simultaneously emphasizes efficient analytical performance for hydrophilic analytes and green analytical concepts. The development of new PALC stationary phases with superior performance is necessary.

RESULTS

In this paper, silanized silica was sequentially subjected to esterification reaction, polymerization reaction and covalent bonding through five steps to obtain SiO2-RHP-AuNPs material, which was prepared as a novel stationary phase for PALC. Comprehensive characterization of the materials by means of Fourier transform infrared spectroscopy, Transmission scanning electron microscope, Elemental analysis and Thermogravimetric analysis showed the successful bonding of the functionalized groups on the original silica. The polymeric stationary phase based on Radix hedysari polysaccharide and Au nanoparticles had higher density of hydroxyl and ester functionalized groups. The Au nanoparticles upgraded their mesoporous structure and thermal stability, providing exceptional chromatographic performance and selectivity for chromatographic analysis. The influence of mobile phase water content, salt concentration, pH and column temperature on the retention behavior was evaluated. The novel Column was found to exhibit a dual mechanism of hydrophobic interactions/ion exchange interactions in a mobile phase with high water content.

SIGNIFICANCE AND NOVELTY

The separation efficiency and selectivity of SiO2-RHP-AuNPs columns for synthetic pigments and organic acids in PALC mode were superior to those of commercial HILIC and C18 columns. In addition, a method for the determination of seven active ingredients in Fructus Ligustri Lucidi by SiO2-RHP-AuNPs column in PALC mode was developed. The method had good stability, reproducibility and accuracy, which was capable of realizing the quality evaluation of Chinese Materia Medicas.

Determination of phosphate in food based on molybdenum yellow derivatization coupled with resonance Rayleigh scattering method

This paper proposed a rapid, selective and sensitive molybdenum yellow derivatization coupled with Resonance Rayleigh scattering (MYD-RRS) method for detection of phosphate. Under the acidic condition, phosphate can be selectively transformed to Keggin type of phosphomolybdic acid (PMA, i.e., PMo12O403-) through molybdenum yellow derivatization reaction prior to RRS detection. The PMA can further react with cationic methyl violet (MV) to form larger PMA-MV ion association complexes, generating significant RRS signal. The concentration of phosphate was linearly related to the RRS signal in the range of 8-200 ng/mL, with the determining coefficient (R2) of 0.9973 and the detection limit of 4 ng/mL. The analytical procedure can be completed within 10 min and the RRS signal intensity can remain stable more than 4 h. The method showed good stability toward temperature and time, and good anti-interference capability. The method was applied to the determination of phosphate in real food samples with the recovery of 85-117% and RSD of 1-5.2%. With the advantages of rapidness, high sensitivity and good selectivity, the MYD-RRS method exhibits great potential to the determination of phosphate in food. It also provides an instructive strategy for detection of analytes with weak RRS signal.

Innovative Sol-gel functionalized polyurethane foam for sustainable water purification and analytical advances

Nanomaterial combined polymeric membranes such as polyurethane foams (PUFs) have garnered enormous attention in the field of water purification due to their ease of management and surface modification, cost-effectiveness, and mechanical, chemical, and thermal properties. Thus, this study reports the use of novel Sol-gel impregnated polyurethane foams (Sol-gel/PUFs) as new dispersive solid phase microextractors (d- µ SPME) for the efficient separation and subsequent spectrophotometric detection of Eosin Y (EY) textile dye in an aqueous solution with a pH of 3-3.8. The Sol gel, PUFs, and Sol gel-impregnated PUFs were characterized using scanning electron microscopy (SEM), goniometry measurements, dynamic light scattering (DLS), energy dispersive spectroscopy (EDS), UV-Visible, and FTIR spectra. Batch experiment results displayed a remarkable removal percentage (96% ± 5.4%) of the EY from the aqueous solution, with the total sorption time not exceeding 60 min. These data indicate rate-limited sorption via diffusion and/or surface complex ion associate formations after the rapid initial sorption steps. A pseudo-second order kinetic model thoroughly explained the sorption kinetics, providing a sorption capacity (qe) of 37.64 mg g-1, a half-life time (t1/2) of 0.8 ± 0.01 min, and intrinsic penetration control dye retention. The thermodynamic results revealed a negative value for ΔG⁰ (-78.07 kJ mol-1 at 293 K), clearly signifying that the dye uptake was spontaneous, as well as a negative value for ΔH⁰ (-69.58 kJ mol-1) and a positive value for ΔS⁰ (147.65 J mol-1 K-1), making clear the exothermic nature of EY adsorption onto the sorbent, with a growth in randomness at the molecular level. A ternary retention mechanism is proposed, involving the "weak base anion exchanger" of {(-CH2-OH+ -CH2-) (Dye anion)-}Sol-gel/PUF and/or {(-NH2 + -COO-) (Dye anion)-}Sol-gel/PUF via solvent extraction and "surface adsorption" of the dye anion on/in the Sol-gel/PUFs membranes in addition to H-bonding, including surface complexation and electrostatic π-π interaction, between the dye and the silicon/zirconium oxide (Si-O-Zr) and siloxane (Si-O-Si) groups on the sorbent. Complete extraction and recovery (93.65 ± 0.2, -102.28 ± 2.01) of EY dye with NaOH (0.5 M) as a proper eluting agent was achieved using a sorbent-packed mini column. In addition, the established extractor displayed excellent reusability and does not require organic solvents for EY enrichment in water samples, making it a talented nominee as a novel sorbent for EY sorption from wastewater. This study is of great consequence for expanding the applicatio1n of Sol-gel/PUFs in developing innovative spectrophotometric sensing strategies for dye determination. In view of this, it would also be remarkable to perform future studies to explore the analytical implications of this extractor regarding safety and environmental and public health issues associated to the pollutant.

Preconcentration of phosphate ions on graphene oxide decorated with lanthanum oxide from waters followed by energy dispersive X-ray fluorescence spectrometric determination

A method for energy dispersive X-ray fluorescence spectrometric (EDXRF) determination of phosphate ions via the PKα line in diverse types of water samples is described. The method is based on ultrasonically assisted dispersive micro-solid phase extraction (USA-DMSPE) using lanthanum oxide supported on graphene oxide (La2O3-GO) as a solid adsorbent. Under optimal preconcentration conditions, i.e. sample pH = 5, sample volume 50 mL, adsorbent dose 0.8 mg, sonication time 30 min, a linear response was obtained between the phosphate concentration and the measured analytical signal in the range of 2-300 ng mL-1 with a correlation coefficient of 0.9995. The developed procedure is characterized by good detection and quantification limits of 0.4 and 1.32 ng mL-1. The inter-day and infra-day precision of the method tested at analyte ion concentrations of 5, 50, and 200 ng mL-1 ranges from 1.1 to 4.4% and 1.2-4.7%, respectively. The accuracy of the method was verified by the standard addition method and the inductively coupled plasma atomic emission spectrometry (ICP-OES) comparative technique. The method was implemented for the analysis of various water samples, including artificial seawater. The phosphate content in studied water samples ranges from 23.8 to 121 ng mL-1. Recoveries in samples enriched with phosphates with a known concentration of 94-102%, as well as a relative difference of 1.5-3.8% between results obtained by USA-DMSPE/EDXRF and ICP-OES indicate the usefulness of the method for the quantitative determination of phosphate ions in natural waters. Moreover, the mechanism of chemisorption in the tested system was discussed and the maximum adsorption capacity of La2O3-GO towards phosphate ions (90.1 mg g-1) was determined.

Polyurethane Foam as a Novel Material for Ochratoxin A Removal in Tea and Herbal Infusions-A Quantitative Approach

A novel solid-phase extraction methodology followed by UHPLC-MS/MS has been developed for Ochratoxin A (OTA) analysis in herbal infusions. For this purpose, a commercial polyurethane foam (PUF) was used as sorbent, and the experimental conditions were fully optimized. The strategy was satisfactory for reducing the matrix effect and allowed for OTA quantification in black tea and herbal infusions, with suitable recoveries and quantitation limits in agreement with those required by the maximum levels allowed by current regulations. The achieved results demonstrated the unprecedented use of polyurethane foam as an effective alternative for OTA retention and quantification in herbal infusions with the advantages of simple preparation, time saving, sustainability, and low cost for routine analysis.

Colorimetric assay for the sensitive detection of phosphate in water based on metal–organic framework nanospheres possessing catalytic activity

For the first time, the inhibition of the catalytic activity of Cu-MOF caused by phosphate was used for phosphate detection.