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Hydrogen peroxide is a key reagent in many analytical assays. At the same time, it is rather unstable and prone to evaporation. For these reasons, its application in sensors requiring reagents in solid state, for example in paper-based microfluidics, is hindered. Usually in paper-based analytical devices reagents are stored in a dried form within paper matrix until the device is used. This approach is not feasible in case of hydrogen peroxide. Here, hydrogen peroxide stabilization on paper with the aid of silica xerogel was studied and optimized to create long-term stable systems which rapidly deliver hydrogen peroxide. The variables affecting hydrogen peroxide stability such as gelation time, silica to H 2 O 2 ratio, type of solid support and storage conditions were optimized to find the combination of variables providing stable H 2 O 2 concentration for the longest time possible. Such paper-silica-H 2 O 2 composites allow to maintain steady hydrogen peroxide concentration for at least 27 days in the optimal conditions. Hydrogen peroxide is rapidly released from silica-paper matrix within a few minutes upon contact with water, without any byproducts. The obtained systems were characterized using scanning electron microscopy with energy dispersive spectroscopy and infrared spectroscopy, revealing that silica is present as a thin film covering cellulose fibers. Finally, to test the developed hydrogen peroxide stabilization method in real sensing scenario, a proof-of-concept paper-based sensor was created for phenolic content determination in fruits and wine. The outcome of this research will open new avenues in the development of user-friendly, long-term stable paper-based analytical devices which utilize hydrogen peroxide as one of reagents. Owing to the fact, that silica matrix is insoluble in water, the proposed H 2 O 2 stabilization method is compatible with most detection schemes without the risk of interfering with the assay. [Display omitted] • Hydrogen peroxide stabilization on paper with silica xerogel was studied. • Factors affecting hydrogen peroxide stability were optimized. • H 2 O 2 -silica-paper composites retain a stable H 2 O 2 amount for at least 27 days. • Paper-based analytical device for phenolic content determination was developed. [ABSTRACT FROM AUTHOR]

The increased production and use of chiral pesticides will enhance their exposure in the environment. Chiral pesticides typically exhibit varied biological effects among these enantiomers. Therefore, it is very essential to develop and validate chiral analytical methods to investigate their potential ecological risks from a stereoselective perspective. Current separation of pesticides enantiomers relies extensively on chiral stationary phases (CSPs), while the development of β-Cyclodextrin derivatives CSPs become the research focus due to their great modifiability and excellent chiral recognition capabilities. A novel chiral stationary phase, 3,5-dichlorophenylaminomethyl-6-phenylenediamine-β-cyclodextrin chemically bonded silica gel (MPDCDA), was successfully prepared. Based on that, a stereoselective HPLC-MS/MS method was developed and validated for the determination of tebuconazole enantiomers in Rana nigromaculata tadpoles. After extraction by QuEChERS, the tebuconazole enantiomers were completely separated with the resolutions of 1.63 using the mobile phase of methanol-water (70/30, v/v). Good linearity (r > 0.9990) for both enantiomers over a concentration range of 0.20–500.0 ng/mL was obtained with the accuracy ranged from 6.7 % to 9.3 % and the intra-day and inter-day precisions below 6.2 % at three quality control levels. The proposed method was successfully applied in evaluating the enantioselective bioaccumulation and elimination profiles of tebuconazole in tadpoles. At the tested conditions, there was no significantly enantioselective difference in the bioaccumulation process for S - tebuconazole and R -tebuconazole. However, the elimination process of tebuconazole enantiomers was enantioselective with R -tebuconazole preferentially degraded. This work provided an accurate risk assessment of chiral pesticides to non-target aquatic organisms from a stereoselective perspective. These findings would deepen our understanding of the potential ecological risks of chiral pesticides on aquatic organisms and provide scientific support for the protection of aquatic organisms and their ecological environments, as well as sustainable development. [Display omitted] • A novel β -cyclodextrin derivative chiral stationary phase with excellent chiral separation ability was constructed. • A reliable LC-MS/MS method for the determination of tebuconazole enantiomers in Rana nigromaculata tadpoles was established. • Enantioselectivity of tebuconazole bioaccumulation and elimination in R ana nigromaculata tadpoles was firstly investigated. [ABSTRACT FROM AUTHOR]

Immobilized proteins hold promise as the basic units that have enabled a broad range of analytical applications within chemical measurement science. As yet, the co-immobilization of diverse proteins at precise ratio and whether they give rise to improved analytical performance remain challengeable. Herein, we utilized a circularly permuted HaloTag (cpHaloTag) to achieve the co-immobilization of two proteins at precise ratio, which was applied in developing a chromatographic method with improved specificity for pursuing dual-target compounds. The methodology involved the fusion 3A and 2C at N- and C-terminuses of cpHaloTag, the immobilization of the fusion protein onto silica gel through bioorthogonal reaction, the morphological and functional characterization, the application in finding dual-target compounds. Expression of the fusion protein in E. coli system showed a yield of milligram level with the presence of 3A and 2C domains. Immobilization of the protein was achieved in 10 min with a reaction efficiency more than 88.5 %. Immobilized 3A-cpHalo-2C exhibited higher specificity and better retentions of canonical compounds of the two enzymes in comparison with the column containing immobilized 3A or 2C alone. In real sample application, screening analysis found that hyperoside, cymaroside, and baicalin were dual-target compounds in concert with 3A and 2C in Shuanghuanglian extract. Taking 3A and 2C as probe, we proposed a simple method for direct co-immobilization of diverse proteins from cell lysates and demonstrated an affinity chromatographic-based dual-target compound screening platform. The implications of these methodology are possible to insight the de novo design of multi-target surface for fabricating new bioanalytical methods with improved performance. [Display omitted] • Proposed a strategy for co-immobilizing of 3A and 2C proteins at precise ratio. • Co-immobilized fusion protein by cpHaloTag improved chromatographic specificity. • Highly selective screening of dual-target compounds in natural products. [ABSTRACT FROM AUTHOR]

In reversed-phase liquid chromatography, the C 18 alkyl bonded phase, as the primary stationary phase, is widely used in pharmaceutical and food analysis. The phenyl bonded phase often serves as a complementary choice to the C 18 phase to enhance the separation performance of specific categories of compounds. However, both C 18 and the currently available phenyl bonded phase chromatography columns show room for further optimization in improving the separation efficiency of specific compound classes, such as dihydroflavonoids. Additionally, the potential role and impact of introducing phosphorus groups into chromatographic stationary phases have not been fully explored, indicating a promising direction for research. In the present work, we prepared a novel phenyl stationary phase by bonding 9-oxa-10-phosphaphenanthrene 10-oxide onto silica gel. The obtained material was characterized by scanning electron microscopy, fourier transforms infrared spectroscopy, and elemental analysis. The results show that 9-oxa-10-phosphaphenanthrene 10-oxide was successfully bonded on the silica surface with a load of 3.90 %. Further chromatographic characterization in high-performance liquid chromatography exhibited high column efficiency (40,792 plates m-1 for the determination of biphenyl) and good stability (RSD of 0.28 %∼5.38 %). Moreover, we made a detailed study of the column separation mechanism by nuclear magnetic resonance spectroscopy titration experiment. Comparing to commercial phenyl column, the proposed stationary phase showed shorter retention time and higher throughput. In addition, the stationary phase has a strong ability to separate multiple types of compounds, which provides a new strategy for the separation of complex samples, such as active ingredients in traditional Chinese medicine. We have developed a novel phenyl column and conducted a comprehensive examination of its chromatographic performance, demonstrating excellent separation capabilities and high efficiency for both nonpolar and moderately polar aromatic compounds. Additionally, we explored the impact of phosphorus-containing groups on the separation performance of chromatographic stationary phases. [Display omitted] • A new DOPO bonded phenyl stationary phase was proposed. • The stationary phase shows typical RPLC properties for aromatic compounds. • Abundant functional groups improve the polarity separation range. • Retention mechanism of DOPO-SiO 2 was investigated through NMR titration experiment. [ABSTRACT FROM AUTHOR]

Due to their excellent stability, low toxicity, flexible modification and adjustable functionality, carbon dots (CDs) have a promising application prospect in the field of chromatographic stationary phases. Hydrogels are new functional polymer materials with three-dimensional network structure that have excellent hydrophilicity, high porosity and unique mechanical properties, which are also good candidate materials for liquid chromatography. Nevertheless, a review of the literature reveals that CDs based nanocomposite hydrogels have not yet been reported as HPLC stationary phases. In this work, amphiphilic CDs with multiple functional groups and polyacrylic acid hydrogel were grafted to the surface of silica gel by an in-situ polymerization method, and a CDs/polyacrylic acid nanocomposite hydrogel stationary phase (CDs/hydrogel@SiO 2) was prepared. CDs act as the macroscopic cross-linking agents to form a cross-linked network with polyacrylic acid chains through physical cross-linking by hydrogen bonding and chemical cross-linking by amidation and esterification reactions, which not only improve the swelling property of the hydrogel but also increase its stability. Additionally, the introduction of CDs with multifunctional groups modulates the hydrophilic-hydrophobic balance of the hydrogel that also imparts good hydrophobicity to the composite hydrogel. Through the study of retention mechanism and influencing factors, it is certificate that the CDs/hydrogel@SiO 2 has mixed-mode chromatographic performance. Furthermore, the CDs/hydrogel@SiO 2 column shows great potential for the determination of organic contaminants in environmental water samples. This work confirms the potential application of CDs/hydrogel composite for the separation of various samples and provides the possibility of developing CDs based nanocomposite hydrogel in the field of liquid chromatography. Introducing CDs into hydrogel can open up a new way for nanocomposite hydrogels to be used in HPLC, which expands the advance of hydrogel and CDs in separation field. A novel amphiphilic carbon dots-based nanocomposite hydrogel modified silica stationary phase (CDs/hydrogel@SiO 2) was proposed for mixed mode liquid chromatography. [Display omitted] • An amphiphilic carbon dots (CDs) based nanocomposite hydrogel was proposed for HPLC. • CDs act as the macroscopic cross-linking agents to produce a nanocomposite hydrogel. • Introduction of CDs adjusts the hydrophilic-hydrophobic balance of composite hydrogel. • Potential application of CDs/hydrogel for efficient HPLC separation was confirmed. • A new way for CDs-based nanocomposite hydrogels to be used in HPLC was opened up. [ABSTRACT FROM AUTHOR]

The development, modification and optimization of analytical methods capable of simultaneous extraction and in-cell clean-up of extracts for subsequent determination of parent PAHs and their associated transformed nitro-PAHs (NPAH), carbonyl-PAHs (CPAH) and hydroxy-PAHs (HO-PAH) products (TPPs) is essential for reducing the time and cost of analysis. The aim of this study was to modify and optimize the pressurized fluid extraction (PFE) technique capable of simultaneous extraction and in-cell clean-up of PAHs and TPPs in urban dust standard reference material and road dust for GC-MS analyses. In this study, multivariate data analysis such as factor analysis (FA), and preference ranking organisation method for enrichment evaluation (PROMETHEE) and geometrical analysis for interactive aid (GAIA) were used to assess the performance of the methods. As the key outcome of the study, an optimized selective reaction monitoring (SRM) Triple Quadrupole (TQ) electron ionization (EI)-GC/MS for measuring PAHs and TPPs without derivatization of polar HO-PAHs was developed. The limits of detection (LOD) for parent PAHs, CPAHs, NPAHs and HO-PAHs using Shimadzu TQ were 1.0–5.0 pg, 1.0–5.0 pg, 1.0–50.0 pg, and 1.0–25.0 pg, respectively. The PROMETHEE-GAIA analysis of the results showed that a combination of 3% deactivated silica gel and activated alumina (2:1) as in-cell clean-up material, and sequential PFE extraction (200 °C ASE temperature, 9 min preheat time and 3 times extraction cycle) using 100% hexane followed by hexane/DCM (1:1) is the best condition for analytes extraction from road dust. An optimized, fast and reliable GC/MS method operated solely in electron ionization (EI) mode was developed for measuring all analytes. The outcomes of this study will contribute significantly to future research on PAHs and TPPs, thereby promoting a safe and sustainable environment. Image 1 • Studies on PAHs and their transformed PAH products (TPPs) are limited. • Simultaneous analyte extraction and in-cell clean-up PFE methods are scarce. • Time, efficiency and cost effective simultaneous PFE method has been developed. • Multivariate data analysis and PROMETHEE-GAIA chemometric tools are essential. • Optimized GC/MS method operated solely in EI mode for all analytes was developed. [ABSTRACT FROM AUTHOR]

Solvent-free analysis of organic pollutants from a complex matrix has attracted significant attention. In this work, we designed and fabricated a facile cooling-assisted solid-phase microextraction device (CA-SPME) that could be used for the solvent-free extraction of volatile and semivolatile compounds from a complex matrix using a commercial SPME probe. Determination of polycyclic aromatic hydrocarbons (PAHs) from soil samples was carried out to evaluate the performance of the designed CA-SPME device. The effects of heating temperature, cooling temperature, extraction time, and moisture content in soil on extraction efficiency were investigated. To enhance the extraction efficiency of the targeted analytes, the matrix solid-phase dispersion technique (MSPD) by grinding soil with silica gels was applied. The results showed that grinding with silica gels promoted the release of PAHs from the soil matrix to the headspace by disrupting the matrix structure, which then facilitated the extraction efficiency. Under optimized conditions, for all of the targeted PAHs, the method exhibited good linearity (40–4000 ng g−1) with regression coefficients (R 2) ranging from 0.9586 to 0.9964. The limits of detection and limits of quantification ranged from 4.2 to 8.5 ng g−1 and 14.0–28.5 ng g−1, respectively. Relative standard deviations corresponding to the analysis of spiked soil samples (n = 5) were 8.1–13.4%. The solvent-free analysis of the certified soil sample using the proposed method demonstrated satisfactory results. Image 1 • A facile cooling-assisted solid phase microextraction device was designed. • The designed device can be used for cooling extraction with commercial SPME fiber. • MSPD enhanced extraction efficiency toward PAHs from soil samples. • Solvent-free analysis of PAHs from soil was accomplished by the proposed method. [ABSTRACT FROM AUTHOR]

High-performance thin-layer chromatography (HPTLC) combined with 1H nuclear magnetic resonance (NMR) spectroscopy has only been demonstrated over a small spectral range so far. The self-printing of chromatographic plates with a modified 3D slurry printer allowed the operator to influence the composition of the adsorbent slurry and thus the purity of the adsorbent layer. The combination of such self-printed, binder-free HPTLC plates with inkjet-driven sample application made possible submicromole-scaled analytical 1H NMR spectroscopy. This was proven using pure HPTLC adsorbents. For comparison, commercial silica gel HPTLC plates were purified by pre-development with solvents for spectroscopy, whereas commercial silica gel HPTLC particles were self-printed on the glass plate after purification under solvent pressure in a recycled HPLC cartridge. Evaluating the signals from different treatments, seven background signals disappeared in the proton spectra and three were reduced to a minimum by use of pre-developed commercial HPTLC plates. In the case of the self-printed, binder-free HPTLC plates made of purified adsorbent, most of the spectral background signals were reduced to a minimum, thus these spectra showed the highest cleanness and most pure analyte proton spectra. For the first time, the full 1H NMR spectroscopy range was made available after an HPTLC separation. This proof of principle opens the avenue for submicromole-scaled analytical 1H NMR spectroscopy. Image 1 • Reduced background signals, useful for structure elucidation at analytical scale. • Full 1H NMR spectroscopy range (small molecule range) available after HPTLC separation. • Suitable HPTLC plate quality for submicromole-scaled analytical 1H NMR spectroscopy. • Clean 1H NMR spectra obtained after separation on inkjet-printed binder-free HPTLC plate. • Orthogonal cleaning procedures utilized to proof quality of self-printed vs. commercial plates. [ABSTRACT FROM AUTHOR]

The composites of covalent organic frameworks (COFs) and silica gel have been considered to be promising chromatographic separation materials due to the distinct advantages such as large specific surface area, good mechanical strength and high porosity. In the present study, a novel imine-linked COF@silica composite was prepared by in-situ growth of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT) and 2,5-dihydroxyterephthalaldehyde (DHTA) monomers on the surface of aminated silica gel (SiO 2 –NH 2). The successful surface-modification of TAPT-DHTA-COF distinctly enhanced the separation selectivity and efficiency of SiO 2 –NH 2. Multiple types of analyte-stationary phase interactions contributed to the selective retention of structurally similar analytes. The designed TAPT-DHTA-COF@SiO 2 was observed to effectively separate hydrophobic phenyl ketones, phthalate esters and steroid hormones. Moreover, the polar amino and hydroxyl groups of TAPT-DHTA-COF facilitated the selective determination of hydrophilic nucleosides/bases. The kinetic performance and thermodynamic behavior of TAPT-DHTA-COF@SiO 2 column were particularly explored. It was found that column efficiency was mainly affected by the mass transfer resistance, and the retention of nucleosides/bases on the TAPT-DHTA-COF@SiO 2 column was temperature dependent. The developed versatile TAPT-DHTA-COF@SiO 2 column was finally applied for detecting environmental hormones as well as water-soluble nicotinamide in real samples. In summary, the potential application of TAPT-DHTA-COF@SiO 2 composite material for liquid chromatographic separations was first explored and verified. The TAPT-DHTA-COF@SiO 2 was proved to be a promising chromatographic separation material. A novel imine-linked COF@SiO 2 composite material was prepared and proposed for mixed-mode chromatographic separations. [Display omitted] • An imine-linked COF@SiO 2 composite was proposed as a versatile HPLC stationary phase. • Hydrophobic and hydrophilic analytes were detected in different chromatographic modes. • Multiple analyte-stationary phase interactions contributed to selective separation. • Strategic design of COF@SiO 2 composites for mixed-mode HPLC separation was verified. • Theoretical inspiration for developing COF-based HPLC stationary phases was provided. [ABSTRACT FROM AUTHOR]

Hydrophilic interaction chromatography (HILIC) is a rapidly developing liquid chromatography mode suitable for separation of strongly or moderately polar samples on polar columns in highly organic mixed mobile phases. In the past five years many new types of columns appeared based on silica gel, organic polymers and other types of supports. The present work reviews the new additions to their family. Further, the progress in the understanding of theoretical principles of the HILIC mode, especially of the role of the mobile phase, and of the adsorbed water are addressed. The amount of adsorbed water strongly depends on the type of the polar column and may be used to distinguish between “conventional HILIC” and “aqueous normal phase chromatography (ANP)”. Further, sample structural effects on the retention are treated in terms of the Linear Solvation Energy Relationship model adopted for partially ionized polar compounds. The impact of dual HILIC-reversed phase (RP) mechanism on a possible increase of the applications of some polar columns is discussed. Attention is paid also to the increasing role of the HILIC mode in various two-dimensional LC techniques and the related mobile phase compatibility problems. [ABSTRACT FROM AUTHOR]

Mobile sensing enabled by MS2 technology, which integrates microfluidic and smartphone components, has seen many applications in recent years. In this direction, we developed an MS2 platform (an integrated kit) for nucleic acid assay, which included a chitosan-modified minimalistic microfluidic chip (CM3-chip), a smartphone-based fluorescence detector (SF-detector), an APP for imaging and analysis, reagents, and accessories. Once the lysed sample was loaded into the CM3-chip modified by 1% concentration and 200–260 kDa molecular weight of chitosan, the following assay can be completed in approximately 1 h. The Mkit can detect 3 × 10° copies μL−1 of plasmid DNA and its polymerase chain reaction (PCR) efficiency was 96.8%. The CM3-chip equipped for the Mkit can enrich nucleic acid from the pH = 5 of lysis buffer, instead of using conventional adsorption mediums such as the magnetic beads and silica gel membranes, which could result in unexpected impurity residuals and tedious cleaning operations. In addition, the performance of the Mkit equipped with the pristine chip was demonstrated to perform poorer than that coupled with the CM3-chip in which the enriched nucleic acid can be all used for " in-situ PCR". The universality, selectivity, and user-friendliness of the Mkit were also validated. We finally demonstrated the feasibility of the Mkit for testing artificially prepared infected samples. H5N6 and IAV-infected saliva samples provided the limits of detection of 5 × 102 copies mL−1 and 3.24 × 102 copies mL−1 per chamber, respectively. The streamlined assay and compact device should enable the great potential of the Mkit in research and potential diagnostic uses. Mobile nucleic acid assay based on chitosan-modified minimalistic microfluidic chip and smartphone. [Display omitted] • A novel nucleic acid analysis system (Mkit) based on chitosan-modified minimalistic microfluidic chip (CM3-chip) and smartphone is developed. • On-chip nucleic acid enrichment by electrostatic force and " in situ PCR"are demonstrated. • The Mkit streamline the entire procedure of nucleic acid assay. • H5N6 and IAV-infected saliva sample tests are demonstrated. [ABSTRACT FROM AUTHOR]

Phospholipids-related matrix effects are a major source impacting the reproducibility of analyte quantification in LC-MS/MS-based bioanalysis. This study intended to evaluate different combinations of polyanion-metal ion based solution system for phospholipids removal and elimination of matrix effects in human plasma. Blank plasma samples or plasma samples spiked with model analytes were proceeded with different combinations of polyanions (dextran sulfate sodium (DSS) and alkalized colloidal silica (Ludox)) and metal ions (MnCl 2 , LaCl 3 , and ZrOCl 2) followed with acetonitrile-based protein precipitation. The representative classes of phospholipids and model analytes (acid, neutral, and base) were detected using multiple reaction monitoring mode. The polyanion-metal ion systems were explored for providing balanced analyte recovery and phospholipids removal by optimizing reagent concentrations or adding formic acid and citric acid as the shielding modifiers. The optimized polyanion-metal ion systems were further evaluated for eliminating matrix effects of non-polar and polar compounds. Any combinations of polyanions (DSS and Ludox) and metal ions (LaCl 3 and ZrOCl 2) could completely remove phospholipids at best-case scenario, while the analyte recovery is low for compounds with special chelation groups. Addition of formic acid or citric acid can improve analyte recovery but significantly decrease the removal efficiency of phospholipids. Optimized ZrOCl 2 -Ludox/DSS systems provided efficient phospholipids removal (>85%) and adequate analyte recovery, and the systems also correctly eliminated ion suppression or enhancement of the non-polar and polar drugs. The developed ZrOCl 2 -Ludox/DSS systems are cost-effective and versatile for balanced phospholipids removal and analyte recovery and provide adequate elimination of matrix effects. [Display omitted] • The polyanion-metal ion systems are developed for phospholipids removal. • Balanced phospholipids removal and analyte recovery is achieved. • Elimination of matrix effects for non-polar and polar compounds is proved. [ABSTRACT FROM AUTHOR]

The hydrogels, because of their swelling properties in response to the environmental stimulus, are being widely considered for the design of controlled drug release systems. To meet the need for developing effective drug delivery methods, we developed special silica colloidal crystal (SCC)-embedded chitosan hydrogel films. The SCC films served as an interference substrate and drug storage layer, while the chitosan hydrogel served as a cover to regulate the drug release. The optical interferometry was performed to dynamically monitor the volume phase transition of chitosan hydrogel response to pH stimulation. Furthermore, the effects of crosslinking ratio and hydrogel thickness on the swelling properties of chitosan hydrogel were also evaluated. More importantly, the pH-responsive swelling of chitosan hydrogel was used to slowly release indomethacin. This system may provide support for drug delivery studies, therefore further expected to apply in the enhancement of the treatment efficiency of new drug therapies. A silica colloidal crystal (SCC)-embedded chitosan hydrogel film was developed and its swelling properties were studied using the OPLI system. The pH-responsive reversible swelling process of chitosan hydrogels was monitored in real time, the effects of factors such as crosslinker concentration on the swelling properties and optical response of hydrogels were evaluated. As a simple controlled release system for indomethacin, the SCC films provide an adsorption area and storage space as a drug storage layer, and the chitosan hydrogel acts as a cover to control drug release, release profile of indomethacin was quantitatively studied. [Display omitted] • Construction of SCC-embedded chitosan hydrogels suitable for optical sensing. • Real-time monitoring of swelling behavior of chitosan hydrogels. • Effects of different factors on swelling properties of chitosan hydrogels. • The drug release application of SCC-embedded chitosan hydrogels. [ABSTRACT FROM AUTHOR]

Two novel chiral stationary phases (CSPs) were prepared by bonding chiral imidazoliums on the surface of silica gel. The chiral imidazoles were derivatized from chiral amines, 1-phenylethylamine and 1-(1-naphthyl)ethylamine. The obtained CSPs were characterized by Fourier Transform Infrared (FT-IR) spectroscopy and elemental analysis (EA), demonstrating the bonding densities of CSP 1 and CSP 2 were 0.43 mmol g −1 and 0.40 mmol g −1 , respectively. These two CSPs could be used to availably separate 8 pharmaceuticals, 7 mandelic acid/its derivatives, 2 1-phenylethylamine derivatives, 1 1,1′-bi-2-naphthol, and 1 camphorsulfonic acid in high-performance liquid chromatography (HPLC). It is found that CSP 1 could effectively enantioseparate most chiral analytes, especially the acidic components, while CSP 2 could enantiorecognize all chiral analytes, although a number of components did not achieve baseline separation. Additionally, the effects of mobile phase composition, mobile phase pH and salt content, chiral selector structures, and analyte structures on the enantiorecognitions of the two CSPs were investigated. It is found that high acetonitrile content in mobile phases was conducive to enantiorecognition. Mobile phase pH and salt content could alter the retention behaviors of different enantiomers of the same chiral compound, resulting in better enantioresolution. Moreover, both chiral selector structures and substituted groups of analytes played a significant role in the separation of chiral solutes. [ABSTRACT FROM AUTHOR]

A coumarine–imino–C2-glucosyl conjugate ( L ) was synthesized and characterized. The conjugate L is found to recognize Cu 2+ in aqueous HEPES buffer by exhibiting a 95% fluorescence quenching in pH range 7–10 even in the presence of several biologically and ecologically relevant metal ions. Fluorescence on–off behavior has been clearly demonstrated on the basis of the binding variability of Cu 2+ to L . The binding has been elicited through the changes observed in fluorescence, absorption, ESI-MS and 1 H NMR titrations. All the other thirteen metal ions studied did not show any change in the fluorescence emission. These ions do not interfere with the recognition of Cu 2+ by L . The structural features of [Cu L ] 2 complex in both the isomeric forms were established by DFT computational calculations. The utility of L has been demonstrated by showing its sensitivity toward Cu 2+ on a thin layer of silica gel. The L gives sensitive fluorescence signals for Cu 2+ even in blood serum and exhibits appropriate fluorescence responses in living cells. [ABSTRACT FROM AUTHOR]

The collection of a low vapor pressure chemical simulant triethyl phosphate sorbed onto silica gel (TEP/SG) from a surface with subsequent analysis of the TEP/SG particulates using desorption electrospray ionization–mass spectrometry (DESI–MS) is described. Collection of TEP/SG particulates on a surface was accomplished using a sticky screen sampler composed of a stainless steel screen coated with partially polymerized polydimethylsiloxane (PDMS). DESI–MS analysis of TEP/SG particulates containing different percentages of TEP sorbed onto silica gel enabled the generation of response curves for the TEP ions m / z 155 and m / z 127. Using the response curves the calculation of the mass of TEP in a 25 wt% sample of TEP/SG was calculated, results show that the calculated mass of TEP was 14% different from the actual mass of TEP in the sample using the m / z 127 TEP ion response curve. Detection limits for the TEP vapor and TEP/SG particulates were calculated to be 4 μg and 6 particles, respectively. [ABSTRACT FROM AUTHOR]

A robust and rapid method for the determination of natural levels of beryllium (Be) in seawater was developed to facilitate mapping Be concentrations in the ocean. A solid-phase extraction method using a silica gel column was applied for preconcentration and purification of Be in seawater prior to determination of Be concentrations with inductively coupled plasma mass spectrometry (ICP-MS). Be was quantitatively adsorbed onto silica gel from solutions with pH values ranging from 6.3 to 9, including natural seawater. The chelating agent ethylenediamine tetraacetic acid was used to remove other ions in the seawater matrix (Na, Mg, and Ca) that interfere with the ICP-MS analysis. The reproducibility of the method was 3% based on triplicate analyses of natural seawater samples, and the detection limit was 0.4 pmol kg −1 for 250 mL of seawater, which is sufficient for the analysis of seawater in the open ocean. The method was then used to determine the vertical profile of Be in the eastern North Pacific Ocean, which was found to be a recycled-type profile in which the Be concentration increased with depth from the surface (7.2 pmol kg −1 at <200 m) to deep water (29.2 pmol kg −1 from 3500 m to the bottom). [ABSTRACT FROM AUTHOR]

Highlights: [•] Silica gel with a film of polyaniline was obtained in a process in situ polymerization of aniline. [•] Uniform distribution of PANI on the surface was confirmed by Raman analysis. [•] Prepared column was tested for non-suppressed IC with spectrophotometric detection. [•] The application of silica gel modified with polyaniline for separation of selected anions with use HPIC was tested. [•] The column and optimized chromatographic system were successfully used for analysis of lake water. [ABSTRACT FROM AUTHOR]

Highlights: [•] MAE-GPC silica gel SPE GC/MS method was developed for determining OPEs in biota samples. [•] The method can remove the lipid compounds and co-extract interferences efficiently. [•] The method reduces amounts of elution solvents and losses of volatile OPEs by use of self-made narrow GPC and SPE column. [•] The method was successfully applied for the analysis of fish and bird samples. [ABSTRACT FROM AUTHOR]

Highlights: [•] We developed a sticky screen sampler for contact sampling of surfaces. [•] We investigated the ability of the sticky screen sampler for collecting chemical particulates from a surface. [•] We demonstrated that the sticky screen was capable of collecting chemical particulates from a surface. [•] We demonstrated that chemical particulates collected by the sticky screen could be analyzed using thermal desorption-ion trap mass spectrometry. [•] We demonstrated nanogram (ng) level detection limits for DMMP immobilized into silica gel. [Copyright &y& Elsevier]

Abstract: A double-receptor sandwich supramolecule method for the separation and determination of trace uranium was proposed in this paper. One receptor is a salophen which can react with uranyl to form a uranyl-salophen complex, and another receptor is an oligonucleotide which can bind uranyl to form oligonucleotide-uranyl-salophen supramolecule. The salophen was immobilized on the surface of silica gel particles and used as the solid phase receptor for separating uranium from solution. The oligonucleotide was labeled with a fluorescent group and used as the labeled receptor for quantitatively analyzing uranium. In the procedure of separation and determination, uranyl ion was first combined with the solid phase receptor and then conjugated with the labeled receptor to form the sandwich-type supramolecule. The labeled receptor in the sandwich supramolecule was then eluted and determined by fluorescence analysis. The experimental results demonstrate that this method has a number of advantages such as high selectivity, excellent pre-concentration capability, high sensitivity, good stability and low cost. Under optimal conditions, the linear range for the detection of uranium is 0.5–30.0ngmL−1 with a detection limit of 0.2ngmL−1. The proposed method was successfully applied for the separation and determination of uranium in real samples with the recoveries of 95.0–105.5%. [Copyright &y& Elsevier]

Abstract: N,N′-bis-(α-methylsalicylidene)-2,2-dimethyl-1,3-propanediimine (SBTD) modified silica gel was prepared and used as sorbent for solid phase extraction of Cr(III) ions from aqueous solution. This sorbent showed a high sorption affinity for Cr(III) while recovery of Cr(VI) was very low. The analyte ion retained on the column was eluted with 1molL−1 HNO3. The chromium ion in the eluent was determined by graphite furnace atomic absorption spectrometry. The effects of different parameters such as pH, eluent type and volume, Schiff''s base concentration, sample and eluent flow rate, interfering ions and adsorbent amount were investigated. [Copyright &y& Elsevier]

Abstract: The performances of three adsorbents, i.e. silica gel, neutral and basic alumina, in the separation of short chain polychlorinated n-alkanes (sPCAs) from potential interfering substances such as polychlorinated biphenyls (PCBs) and organochlorine pesticides were evaluated. To increase the cleanup efficiency, a two-step cleanup method using silica gel column and subsequent basic alumina column was developed. All the PCB and organochlorine pesticides could be removed by this cleanup method. The very satisfying cleanup efficiency of sPCAs has been achieved and the recovery in the cleanup method reached 92.7%. The method detection limit (MDL) for sPCAs in sediments was determined to be 14ngg−1. Relative standard deviation (R.S.D.) of 5.3% was obtained for the mass fraction of sPCAs by analyzing four replicates of a spiked sediment sample. High resolution gas chromatography/electron capture negative ion–low resolution mass spectrometry (HRGC/ECNI–LRMS) was used for sPCAs quantification by monitoring [M−HCl] − ions. When applied to the sediment samples from the mouth of the Daliao River, the optimized cleanup method in conjunction with HRGC/ECNI–LRMS allowed for highly selective identifications for sPCAs. The sPCAs levels in sediment samples are reported to range from 53.6ngg−1 to 289.3ngg−1. C10- and C11-PCAs are the dominant residue in most of investigated sediment samples. [Copyright &y& Elsevier]

Abstract: A comparison of SPE cartridges produced in authors laboratory containing silica modified by addition of three functional moieties with standard C-18 and SDVB cartridges was made in terms of their applicability for the isolation of flavor compounds. Compounds found in wine and grapes were used for model mixture, which was spiked into a grape juice. Functionalized phases for SPE were prepared modifying silica gel with alkoxysilanes with different functional groups: (3-(phenylamino)-propyltrimethoxysilane, octyltriethoxysilane and octadecyl-silane. The functionalization was carried out by the dry method, which resulted 5, 10 and 20 weight parts of initial support. Functionalized phases were characterized using FT-IR, elemental analysis and NMR. Performance for new phases compared to “standard” ones (C-18 and SDVB (styrene–divinylbenzene) varied, depending on the group or type of analyzed compound. They were more efficient in extraction of methyl anthranilate and vanilins. For extraction of terpenes, C-6 alcohols, isoprenoids, benzene derivatives and phenols their efficiency was comparable to that of C-18. Functionalized laboratory-made mixed phases are suitable for extraction of flavor compounds from grape juice. They are suitable for extraction of compounds belonging to different chemical classes with the efficiency comparable to C-18 and SDVB phases. The production of such functionalized phases can be easily performed in the laboratory, at a very low cost, comparing to C-18 or SDVB cartridges. This makes the proposed functionalized phases an interesting alternative, in sample preparation for analysis and particularly in preparative/flash chromatography. [Copyright &y& Elsevier]

Abstract: The potentiometric response of a carbon paste electrode modified with silica sol–gel and mercaptosuccinic acid (MSA) in the presence and absence of gold nano-particles was studied. The results showed that the electrode with gold nano-particles was responded to Al3+ ions as a hard metal ion. On the other hand, the electrode without gold nano-particles was responded to copper ions as a soft metal ion. The electrodes without and with gold nano-particles exhibits a Nernstian slope of 29.1 and 19.2mVdecade−1 for copper and aluminum ions over a wide concentration range of 4.3×10−7–1.0×10−2 and 4.5×10−7–1.6×10−3 molL−1, respectively. The detection limits of electrodes were 4.0×10−7 and 1.6×10−7 molL−1 for copper and aluminum ions, respectively. [Copyright &y& Elsevier]

Abstract: A new diffusive sampling method for the simultaneous determination of ozone and carbonyls in air has been developed. In this method, silica gel impregnated with a mixture of trans-1,2-bis(2-pyridyl)ethylene (2BPE) and 2,4-dinitrophenylhydrazine (DNPH) is used as the absorbent; further, a porous sintered polyethylene tube (PSP-diffusion filter), which acts as a diffusive membrane, and a small polypropylene syringe (PP-reservoir) for elution of the analytes from the absorbent are used. The carbonyls present in air react with DNPH in the absorbent to form hydrazone derivatives. Concurrently, ozone in the air reacts with 2BPE to form pyridine-2-aldehyde, which immediately reacts with DNPH to form a pyridine-2-aldehyde hydrazone derivative. All the hydrazones derived from airborne carbonyls, including pyridine-2-aldehyde (formed from ozone), are completely separated and analyzed by high-performance liquid chromatography. The sampling rates of ozone (44.6mLmin−1) and formaldehyde (72.0mLmin−1) are determined by comparison with the rates obtained in an active sampling method. The sampling rates of other carbonyl compounds are calculated from the respective molecular weights according to a rule based on Graham''s law. The calculated sampling rates agree with the experimental values. The DSD-BPE/DNPH method is advantageous because it is simple and allows for the simultaneous analysis of ozone and carbonyls. [Copyright &y& Elsevier]

Abstract: New optical sensors for trace amounts of oxygen are based on platinum(II) and palladium(II) complexes of 5,10,15,20-meso-tetrakis-(2,3,4,5,6-pentafluorphenyl)-porphyrin covalently attached to the surface of amino-modified silica-gel particles. The dye-doped silica-gel particles are dispersed in silicone rubber. The Stern–Volmer plots show linear response and are virtually identical for either luminescence intensity and decay time. Other features include high photostability and rapid response times (∼150ms in gas phase). The sensors based on the palladium(II) complex show significantly higher sensitivity (K SV about 67kPa−1 at 25°C) with the dynamic range from 0.02 to 100Pa. The sensitivity of the platinum(II) complexes is significantly lower (K SV =3.7–4.2kPa−1, dynamic range 0.3–1000Pa). The sensors can be suitable for application in breweries, water boilers and for marine research (monitoring of oxygen minimum zones). [Copyright &y& Elsevier]

Abstract: Four novel ILs functionalized β-cyclodextrins (β-CDs) were prepared by treating 6-tosyl-β-cyclodextrin with 1,2-dimethylimidazole or 1-amino-1,2,3-triazole, and bonded to silica gel to obtain chiral stationary phases (CSPs) to be used in high-performance liquid chromatography (HPLC). The separation performances of these CSPs were examined with 16 chiral aromatic alcohol derivatives and 2 racemic drugs in acetonitrile-based polar-organic mobile phase. Excellent enantioseparations were achieved for most of the analytes. The highest value of resolution factor calculated is 6.868. Comparison of the performance of 8a, 8b, 8c and 8d suggests that the positively charged imidazole group provides electrostatic interactions probably through strong H-bonding with the analytes, whereas the cationic triazole, which forms a weaker ion pair with its counter ion, is more capable of participating in ion-pairing interactions with acidic analytes. However, for compounds 12 and 13, which have larger molecular volumes than the other analytes, the interactions between analytes and both cationic imidazole and its counter ion of the selectors play an important role in the chiral resolution. Moreover, the high resolutions were found to depend on the properties of the cations and anions on the selectors in combination with the chiral recognition sites on the rim of the CD. The ionic strength in mobile phase affects the relative interactions between analytes and the chiral selector as well as between analytes and solvents. [ABSTRACT FROM AUTHOR]

Abstract: A new ion-selective electrode (ISE) for the detection of trace chromium(III) was designed by using 2-acetylpyridine and nanoporous silica gel (APNSG)-functionalized carbon paste electrode (CPE). The presence of APNSG acted as not only a paste binder, but also a reactive material. With 7.5wt% APNSG proportions, the developed electrode exhibited wide dynamic range of 1.0×10−8 to 1.0×10−3 M toward Cr(III) with a detection limit of 8.0×10−9 M and a Nernstian slope of 19.8±0.2mVdecade−1. The as-prepared electrode displayed rapid response (∼55s), long-time stability, and high sensitivity. Moreover, the potentiometric responses could be carried out with wide pH range of 1.5–5.0. In addition, the content of Cr(III) in food samples, e.g. coffee and tea leaves, has been assayed by the developed electrode, atomic absorption spectrophotometer (AAS) and atomic emission spectrometer (ICP-AES), respectively, and consistent results were obtained. Importantly, the response mechanism of the proposed electrode was investigated by using AC impedance and UV–vis spectroscopy. [Copyright &y& Elsevier]

Abstract: Bisphenol A (BPA) is an emerging contaminant with severe toxic effects such as disrupting endocrine system or causing cancer, therefore, developing sensitive and selective sensor for BPA is very important and interesting. Herein, MCM-41, a kind of mesoporous silica, was synthesized and then used to prepare an electrochemical sensor for BPA. For better comparison, carbon nanotubes, activated carbon, silica gel and graphite were also employed to prepare electrochemical sensor for BPA. The electrochemical behaviors of BPA at different electrochemical sensors were investigated. Compared with other sensors, the MCM-41 sensor greatly enhances the response signal of BPA due to the large active surface area and high accumulation efficiency. The effects of pH value, accumulation time and sensor composition were examined. The linear range is from 2.2×10−7 to 8.8×10−6 molL−1, and the limit of detection is evaluated to be 3.8×10−8 molL−1. Finally, the MCM-41 sensor was successfully employed to determine BPA in water samples. [Copyright &y& Elsevier]

Abstract: In this study, a new 4-(2-morinyldiazenyl)-N-(3-(trimethylsilyl)propyl)benzamide modified silica gel (SG-MTPB) sorbent was prepared and characterized by FT-IR spectroscopy and studied for separation and preconcentration of Sc(III) prior to its determination by inductively coupled plasma atomic emission spectrometry (ICP-AES). Experimental conditions for effective adsorption of trace Sc(III) were optimized using both batch and column procedures. At pH 3, Sc(III) could be quantitatively adsorbed on the new sorbent. And the adsorbed Sc(III) could be completely eluted by using 2mL of 6molL−1 of HCl+2% CS(NH2)2. Most common coexisting ions did not interfere with the separation and preconcentration of Sc(III) at optimal conditions. The maximum static adsorption capacity of the sorbent for Sc(III) was 600μmolg−1 while the time of 95% adsorption was less than 2min. The detection limit of present method was found to be 0.085μgg−1, and the relative standard deviation (R.S.D.) was lower than 1.3%. The method was also successfully applied to the preconcentration of trace Sc(III) in the environmental samples with satisfactory results. [Copyright &y& Elsevier]

Abstract: Solid-phase spectrophotometric and visual test-methods of fluoride and oxalate determination are proposed. The methods are based on the competitive reactions of ZrOCl2 with methylthymol blue immobilized on silica gel and fluoride or oxalate in solution. Absorbance of the solid-phase reagent at 590nm decreases with the growth of fluoride and oxalate contents in solution. The developed methods demonstrate high selectivity. The interference of Bi(III) and SO4 2−, PO4 3− is eliminated by the addition of 0.01molL−1 solution of ascorbic acid and 0.01molL−1 of BaCl2, respectively. To eliminate the fluoride interference with oxalate determination 1×10−3 molL−1 solution of Ca(NO3)2 at pH 1.5 was added. The anions of the organic acids were destructed prior to F− determination by ultrasonic exposition (44kHz, intensity of ≤10Wcm−2 for 3min). The proposed methods were applied to the analysis of mineral water, toothpaste and biological fluids. [Copyright &y& Elsevier]

Abstract: Dysprosium(III)-imprinted thenoyltrifluoroacetone (TTA) modified silica gel sorbent was synthesized by surface imprinting technique and was employed as a selective solid-phase extraction material for flow injection solid-phase extraction on-line coupled with inductively coupled plasma-atomic emission spectrometry (ICP-AES) determination of Dy(III). The largest selectivity coefficient for Dy(III) in the presence of competitive ions such as La(III), Nd(III) and Gd(III) was above 350. The static adsorption capacity and selectivity coefficient of the imprinted sorbent are higher than those of the non-imprinted sorbent and the imprinted TTA modified silica gel sorbent offered a fast kinetics for the adsorption and desorption of Dy(III). With a sample loading flow rate of 2.5mLmin−1 for 48s preconcentration and elution flow rate of 1.5mLmin−1 for 8s elution, an enrichment factor of 10 and the sample frequency of 40sampleh−1 were obtained. Detection limits (3σ) based on three times standard deviations of the blanks by eight replicates was 0.2ngmL−1 and the precisions (R.S.D.s) was 1.5% (n =8, c =40ngmL−1). To validate the proposed method, two certified reference materials of GBW07401 soil and GBW07301a sediment were analyzed and the determined values were in a good agreement with the certified values. The method is rapid, selective, sensitive and applicable to the determination of trace Dy(III) in environmental samples with complicated matrix. [Copyright &y& Elsevier]

Abstract: A novel atomic-contribution system for predicting of values is presented and validated on 13 thin layer chromatography screening systems on silica gel, where the large experimental datasets (198–761 values) are available. The is predicted with error less than 0.5 in majority of solutes (besides several outliers), which corresponds to difference in equal to 0.28 in the worst case. The system was validated by dividing the data into training and validation datasets, proving its accuracy. The main reason of larger errors in outliers are: large conjugated heterocycles, quarternary ammonium cations, large amount of polar atoms or very simple but unique molecules. The calculations are very easy and can be performed on free software or even manually. The presented method can be used in the retention prediction of new solutes in existing chromatographic screening systems. [Copyright &y& Elsevier]

Abstract: Titanium phosphate grafted on the surface of silica gel (devoted briefly as Si-TiPH) was synthesized and used as bulk modifier to fabricate a renewable three-dimensional chemically modified electrode. The Si-TiPH bulk modified carbon paste electrode was used for the selective determination of dopamine (DA) in the presence of ascorbic acid (AA). The modified electrode offers an excellent and stable response for the determination of DA in the presence of AA. The differential pulse voltammetry peak current was found to be linear with the DA concentration in the range 2×10−7 to 1×10−6 and 2×10−6 to 6×10−5 molL−1. The detection limit of the proposed method in the presence of 2.0×10−5 M of AA was found to be 4.3×10−8 molL−1 for DA determination. The proposed method was successfully applied for the determination of DA in injections. [Copyright &y& Elsevier]

Abstract: A new porous sorbent for wastewater treatment of metal ions was synthesized by covalent grafting of molecularly imprinted organic–inorganic hybrid on silica gel. With sucrose and polyethylene glycol 4000 (PEG 4000) being synergic imprinting molecules, covalent surface coating on silica gel was achieved by using polysaccharide-incorporated sol–gel process starting from the functional biopolymer, chitosan and an inorganic epoxy-precursor, gamma-glycidoxypropyltrimethoxysiloxane (GPTMS) at room temperature. The prepared porous sorbent was characterized by using simultaneous thermogravimetry and differential scanning calorimeter (TG/DSC), scanning electron microscopy (SEM), nitrogen adsorption porosimetry measurement and X-ray diffraction (XRD). Copper ion, Cu2+, was chosen as the model metal ion to evaluate the effectiveness of the new biosorbent in wastewater treatment. The influence of epoxy-siloxane dose, buffer pH and co-existed ions on Cu2+ adsorption was assessed through batch experiments. The imprinted composite sorbent offered a fast kinetics for the adsorption of Cu2+. The uptake capacity of the sorbent imprinted by two pore-building components was higher than those imprinted with only a single component. The dynamic adsorption in column underwent a good elimination of Cu2+ in treating electric plating wastewater. The prepared composite sorbent exhibited high reusability. Easy preparation of the described porous composite sorbent, absence of organic solvents, cost-effectiveness and high stability make this approach attractive in biosorption. [Copyright &y& Elsevier]

Abstract: Two As(V) selective electrodes (with and without inner reference solution) have been developed using selective membranes based on iron oxyhydroxide embedded on silica gel mixed with ultrapure graphite at a 2/98 (w/w) ratio. The active component of the membrane was synthesised by means of the sol-gel technique and characterized by X-ray and FTIR spectroscopy. This compound shows a great affinity towards As(V) ions adsorbing 408mgg-1. Using 1moll-1 phosphate buffer (at a 1/1, v/v ratio) to adjust the pH and the ionic strength to 7 and 0.5moll-1, respectively, the calibration curve is linear from 1.0×10-1 to 1.0×10-6moll-1 As(V), with a practical detection limit of 4×10-7moll-1 (0.03mgl-1) and a slope close to 30mVdecade-1. The effect of potentially interfering ions was investigated. The accuracy and precision of the procedure have been tested on arsenic-free drinking water samples spiked with known amounts of arsenic and on groundwater samples containing high levels of arsenic. Total arsenic in these samples was determined after oxidation of As(III) with iodine at pH 7. The results of total As were comparable to those generated by ET-AAS. [Copyright &y& Elsevier]

Abstract: A simple method for doping ion-sensing ingredients into silanized silica particles (∼3.5μm) was developed to fabricate carrier-based ion-selective microsphere optical ion sensors. These ion sensors operate according to established bulk optode principles. Na+-selective microsphere optical sensors were prepared with the ionophore tert-butylcalix[4]arene tetraacetic acid tetraethylester, the H+-chromoionophore 9-(diethylamino)-5-octadecanoylimino-5H-benzo[a]phenoxazine (ETH 5294), the ion exchanger sodium tetrakis[3,5-bis(tri-fluoromethyl)phenyl]borate (NaTFPB), PVC and the plasticizer bis(2-ethylhexyl)sebacate (DOS). For Ca2+ sensing, the grafted Ca2+ ionophore AU-1 in poly(n-BA) was applied with ETH 5294, NaTFPB and DOS. Fluorescence microscopy and flow cytometry were used for characterization. The resulting microsphere optical ion sensors were found to obey bulk optode theory with reliable response, high selectivities, dynamic ranges suitable for physiological measurements and a shelf time of over 6 months. The measuring ranges (logarithmic molar concentrations) at pH 7.4 were -3.5 to -1.5 for the fabricated Na+-selective optical-sensing microspheres, and -4.5 to -1.5 for Ca2+-selective optical-sensing microspheres. Corresponding thin optode films and regular PVC/DOS-based microspheres were prepared for comparison and showed similar response characteristics. The fabricated microsphere optical ion sensors were also deposited on an optical fiber bundle, and reproducible fluorescence signals were observed. [Copyright &y& Elsevier]

Abstract: 2-Thiophenecarboxaldhyde is chemically bonded to silica gel surface immobilized monoamine, ethylenediamine and diethylenetriamine by a simple Schiff’s base reaction to produce three new SP-extractors, phases (I–III). The selectivity properties of these phases toward Hg(II) uptake as well as eight other metal ions: Ca(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) were extensively studied and evaluated as a function of pH of metal ion solution and equilibrium shaking time by the batch equilibrium technique. The data obtained clearly indicate that the new SP-extractors have the highest affinity for retention of Hg(II) ion. Their Hg(II) uptake in mmolg-1 and distribution coefficient as log Kd values are always higher than the uptake of any other metal ion along the range of pH used (pH 1.0–10.0). The uptake of Hg(II) using phase I was 2.0mmolg-1 (log Kd 6.6) at pH 1.0 and 2.0. 1.8mmolg-1 (log Kd 4.25), 1.6mmolg-1 (log Kd 3.90) and 1.08mmolg-1 (log Kd 3.37) at pH 3.0, 5.0 and 8.0, respectively. Selective separation of Hg(II) from the other eight coexisting metal ions under investigation was achieved successfully using phase I at pH 2.0 either under static or dynamic conditions. Hg(II) was completely retained while Ca(II), Co(II) and Cd(II) ions were not retained. Ni(II), Cu(II), Zn(II), Pb(II) and Fe(III) showed very low percentage retention values to be 0.74, 0.97, 3.5 and 6.3%, respectively. Moreover, the high recovery values (95.5 ± 0.5, 95.8 ± 0.5 and 99.0% ± 1.0) of percolating two liters of doubly distilled water, drinking tap water and Nile river water spiked with 5ng/l of Hg(II) over 100mg of phase I packed in a minicolumn and used as a thin layer enrichment bed demonstrate the accuracy and validity of the new SP-extractors for preconcentration of the ultratrace amount of spiked Hg(II) prior to the determination by borohydride generation atomic absorption spectrometry (AAS) with no matrix interference. The detection limit (3σ) for Hg(II) based on enrichment factor 1000 was 4.75pg/ml. The precision (R.S.D.) obtained for different amounts of mercury was in the range 0.52–1.01% (N = 3) at the 25–100ng/l level. [Copyright &y& Elsevier]

A preconcentration method based on the adsorption of palladium-dimethylglyoxime (DMG) complex on silica gel for the determination of palladium at trace levels by atomic absorption spectrometry (AAS) has been developed. The retained palladium as Pd(DMG)2 complex was eluted with 1 mol l-1 HCl in acetone. The effect of some analytical parameters such as pH, amount of reagent and the sample volume on the recovery of palladium was examined in synthetic solutions containing street dust matrix. The influence of some matrix ions on the recovery of palladium was investigated by using the developed method when the elements were present both individually and together. The results showed that 2500 μg ml-1 Na+, K+, Mg2+, Al3+ and Fe3+; 5000 μg ml-1 Ca2+ ; 500 μg ml-1 Pb2+; 125 μg ml-1 Zn2+; 50 μg ml-1 Cu2+ and 25 μg ml-1 Ni2+ did not interfere with the palladium signal. At the optimum conditions determined experimentally, the recovery for palladium was found to be 95.3±1.2% at the 95% confidence level. The relative standard deviation and limit of detection (3s/b) of the method were found to be 1.7% and 1.2 μg l-1, respectively. In order to determine the adsorption behaviour of silica gel, the adsorption isotherm of palladium was studied and the binding equilibrium constant and adsorption capacity were calculated to be 0.38 l mg-1 and 4.06 mg g-1, respectively. The determination of palladium in various samples was performed by using both flame AAS and graphite furnace AAS. The proposed method was successfully applied for the determination of palladium in the street dust, anode slime, rock and catalytic converter samples. [Copyright &y& Elsevier]

The efficiency for the extraction of U(VI) of new modified silica gels, namely N-tripropionate (or N-triacetate)-substituted tetraazamacrocycles-bound silica gels, has been studied. The effect of the nature of the ligand, the pH and the temperature was studied both in batch experiments as well as in continuous extraction. These silica gels are good candidates for the extraction of U(VI) when compared to a commercially available acid-type chelating resin. The breakthrough and regeneration tests showed that the total removal of U(VI) from a contaminated solution can be achieved by using a column packed with such tetraazamacrocycles-bound silica gels. Finally, the use of a modified silica gel in a pilot device allowed the total decontamination of 50 m3 of real effluents containing traces of uranium, plutonium, and americium. [Copyright &y& Elsevier]

A sensitive and selective column adsorption method is proposed for the off-line preconcentration and determination of phthalic acid esters (PAEs), namely benzyl-butyl phthalate (BBP), di-n-butyl phthalate (DBP) and di-cyclohexyl phthalate (DCHP). The PAEs was preconcentrated on Saccharomyces cerevisiae immobilized on silica gel and then determined by high performance liquid chromatography (HPLC). Several parameters on the recovery of the analytes were investigated. Recoveries of BBP, DBP and DCHP were 100±2, 98±2 and 98±3%, respectively, at 95% confidence level under optimum conditions. The detection limits (3S/N) of BBP, DBP and DCHP were 3.2, 6.3 and 3.1 μg l−1, respectively. The capacity of the adsorbent was also examined and found to be 1.4 mg g−1 for BBP and DBP, and 3.6 mg g−1 for DCHP. S. cerevisiae immobilized on silica gel is suitable for repeated use without decreasing recovery up to about 25 adsorption–elution cycles. The proposed method was successfully applied to the determination of PAEs in river water with high precision and accuracy. [Copyright &y& Elsevier]

Toluidine Blue O (TBO) was covalently bound on silica gel and mixed with graphite powder and paraffin oil to produce modified carbon paste electrodes. The formal potential (E°′) of the covalently bound TBO was found to be −100 mV versus Ag|AgCl (KCl sat.) at pH 7.0 and the E°′ varied less than anticipated for a 2-electron–proton type mediator with pH. The bound TBO was found to act as an efficient electron acceptor for NADH as well as electron donor for oxidised horseradish peroxidase (HRP). The kinetics and the mechanism of the reaction between NADH and TBO were investigated with cyclic voltammetry and using a rotating disc electrode. Further experiments were done in the flow injection mode injecting different concentrations of NADH. Similar studies were done in the presence of hydrogen peroxide when HRP was adsorbed onto the TBO modified silica gel carbon paste electrodes. [Copyright &y& Elsevier]

Cross-linked poly(vinyl alcohol) (PVA)–silica gel copolymer has been employed as a optical pH sensor substrate for immobilisation of fluorescein. Cross-linking was carried out by the sol–gel process incorporating PVA in initial sol–gel solution of tetra-methoxysilane (TMOS) under acidic conditions. Three dimensional network formation could be achieved using compositions of PVA/TMOS=80–90/20–10 vol.% to result in crack-free films. The fluorescent sensor layers were prepared by dip-coating of gel solution onto glass slides. The dynamic fluorescence response towards different pH values was investigated in terms of the influence of sample ionic strength, membrane composition as well as age of sol–gel layers. Depending on the composition of the matrix pKa values of 6.50, 6.68 and 7.06 were found 18 days after continues storage in buffer. [Copyright &y& Elsevier]

Silica gel modified with 3-aminopropyltriethoxysilane was anchored with resacetophenone to prepare a new chelating surface (or matrix). It was characterized with cross polarization magic angle spinning 13C NMR spectroscopy and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and used for the separation and preconcentration of Cu(II), Pb(II), Ni(II), Fe(III), Cd(II), Zn(II) and Co(II) prior to their determination by flame atomic absorption spectrometry (FAAS). The optimum pH ranges for quantitative sorption are 6.0–7.5, 5.5–7.5, 5.0–7.0, 6.5–7.5, 6.0–7.5, 6.0–7.0 and 6.0–7.5 for Cu, Pb, Fe, Zn, Co, Ni and Cd, respectively. All the metals can be desorbed with 3 mol dm−3 HCl or HNO3. The sorption capacity for these metal ions is in range of 57.8–365.0 μmol g−1 of chelating matrix. Tolerance limits for electrolytes NaNO3, NaCl, NaBr, Na2SO4 and Na3PO4 and cations Ca(II) and Mg(II) in the sorption of these metal ions are reported. Preconcentration factors of 200, 300, 150, 250, 250, 200 and 200 for Cd, Co, Zn, Cu, Pb, Fe and Ni, respectively, are obtained and t1/2 values are <1 min except for Cd. 95% extraction by a batch method takes ≤25 min. The simultaneous enrichment and determination of all the metals are possible if the total load of the metal ions is less than the sorption capacity. In river water samples all these metal ions were enriched with the present matrix and determined with a flame atomic absorption spectrometer (R.S.D. ≤ 7.7%). Copper contents of pharmaceutical samples (vitamin capsule) were preconcentrated with the present chelating matrix and estimated with flame AAS, with R.S.D. ∼ 2.2%. The results are in the good agreement with the certified value, 0.4 mg/g of capsule. [Copyright &y& Elsevier]