Determination Of Traces Research Articles

Low-Level Quantification of Cefixime and Cefdinir in Human Plasma Using Ultrasound-and Magnetic-Assisted Dispersive Micro-Solid-Phase Extraction (MSPE) Based upon Carbon Quantum Dots (CQDs) Functionalized with Magnetite/Zeolitic Imidazolate Framework 71/Polypyrrole Combined with High-Performance Liquid Chromatography (HPLC)

A promising and reusable nanohybrid based on carbon quantum dots immobilized with Fe3O4/zeolitic imidazolate framework-71/polypyrrole (CQD/Fe3O4/ZIF-71/PPy) was fabricated as a sorbent for ultrasound-and magnetic-assisted dispersive micro-solid-phase extraction (US-M-A-DMSPE) followed by high-performance liquid chromatography with ultraviolet detection (HPLC-UV) for simultaneous trace determination of cefixime (CFX) and cefdinir (CFD) in human plasma. In order to improve the contact between the analyte and the sorbent, the surface of the CQDs was modified by individual materials involving zeolitic imidazolate framework and polypyrrole via an in-situ synthesis of ZIF-71 followed by oxidative polymerization of pyrrole. The structure of the prepared sorbent was characterized by x-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Under the optimized conditions, the nanosorbent provided high adsorption and selectivity toward the analytes. The limits of detection for CFX and CFD were 0.15 and 0.04 ng mL−1, respectively. The coefficients of determination (r2) were between 0.990 and 0.993, with dynamic ranges of 0.5–1750.0 and 0.2–1500.0 ng mL−1. The method was used for quantifying CFX and CFD in plasma samples to evaluate the pharmacokinetic aspects, including the half-life (T½), the time to reach the maximum concentration (Tmax), the maximum plasma concentration (Cmax), area under the curve (AUC0-24) and area under the curve at infinite time (AUC0-∞). Reliable reproducibility as the intra- assay (≤ 6.3%) and inter-assay (≤ 8.7%) together with reasonable accuracy (≤ 8.8%) were obtained.

Determination of trace perfluorinated compounds in environmental water samples by dispersive solid- phase extraction-high performance liquid chromatography-tandem mass spectrometry using carbon nanotube composite materials

In this work, carbon nanotubes (CNTs) on silica rod (SiO2) composite materials were prepared to extract six perfluorinated compounds (PFCs) in real environmental water samples by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The as-synthesized sorbents, hereafter referred to as CNT@SiO2, were employed for dispersive solid-phase extraction (d-SPE). Perfluoroheptanoic acid (PFHpA), perfluorohexane sulfonate (PFHxS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorooctane sulfonate (PFOS), and perfluorodecanoic acid (PFDA) were selected as target analytes. The main extraction parameters were systematically optimized using the single-factor optimization method. The optimum adsorption parameters were as follows: adsorption time of 30 min, sorbent amount of 10 mg, pH 6 and NaCl concentration of 1.7 mol/L for sample solution, and 4 mL acetone as desorption solvent, desorption for 4 min. LC-triple quadrupole MS was conducted to quantify the selected PFCs in water samples. The mobile phase was 5 mmol/L ammonium acetate and methanol, the flow rate was set to 0.4 mL/min, the column temperature was set to 40 ℃, and the injection volume was 5.0 μL. The chromatographic separation system was equipped with a Kinetex C18 column (100 mm×2.1 mm, 1.7 μm). The mass spectrometer was operated with negative electrospray ionization in multi-reaction monitoring mode. CNT@SiO2 was prepared in five batches and used as the d-SPE sorbent, and the relative standard deviations (RSDs) of the PFC recoveries among these five batches ranged from 4.9% to 9.3%. The reusability of the CNT@SiO2 sorbent was assessed. After eight d-SPE cycles using the same sorbent, the RSDs of the PFC recoveries were 3.7%-8.2%. These results indicated that the sorbent had good stability and reusability for d-SPE. Excellent results were achieved under optimal extraction conditions. The method validation results indicated that the linear ranges were 0.4-1000 ng/L for PFNA, PFOS, and PFDA, 0.9-1000 ng/L for PFHpA, 0.7-1000 ng/L for PFHxS, and 0.6-1000 ng/L for PFOA. The correlation coefficients were 0.973-0.997. The limit of detection (LOD) and limit of quantification of the method were 0.10-0.26 ng/L and 0.33-0.87 ng/L, respectively. At 20 ng/L, the RSDs of the intra- and inter-day precisions were 2.73%-7.75% and 3.38%-8.21%, respectively. At 100 ng/L, the RSDs of the intra- and inter-day precisions were 2.95%-8.46% and 4.16%-9.14%, respectively. Finally, at 500 ng/L, the RSDs of the intra- and inter-day precisions were 2.51%-7.48% and 3.59%-9.63%, respectively. The developed method was applied to analyze six PFCs in tap water, barreled drinking water, and river water samples. PFOA and PFOS were determined in tap water at mass concentrations of 5.6 and 8.7 ng/L, respectively. No PFCs were found in barreled drinking water and river water. Satisfactory recoveries of 72.1%-109.6% at low, middle, and high spiking levels were also obtained. In conclusion, the d-SPE-LC-MS/MS method based on CNT@SiO2 composite sorbents is accurate and sensitive. The results of this study demonstrate that CNT@SiO2 is a good choice for the rapid and effective determination of PFCs from water samples. Further exploration of the use of CNT@SiO2 sorbents for the extraction and determination of trace organic pollutions in environmental samples is in progress.

Synthesis of cuprous oxide/silver (Cu2O/Ag) hybrid as surface-enhanced Raman scattering probe for trace determination of methyl orange.

Recently, there have been publications on preparing hybrid materials between noble metal and semiconductor for applications in surface-enhanced Raman scattering (SERS) substrates to detect some toxic organic dyes. However, the use of cuprous oxide/silver (Cu2O/Ag) to measure the trace amounts of methyl orange (MO) has not been reported. Therefore, in this study, the trace level of MO in water solvent was determined using a SERS substrate based on Cu2O microcubes combined with silver nanoparticles (Ag NPs). Herein, a series of Cu2O/Agx ( 1-5) hybrids with various Ag amounts was synthesized via a solvothermal method followed by a reduction process, and their SERS performance was studied in detail. X-ray diffraction (XRD) and scanning electron microscopy results confirmed that 10 nm Ag NPs were well dispersed on 200-500 nm Cu2O microcubes to form Cu2O/Ag heterojunctions. Using the as-prepared Cu2O and Cu2O/Agx as MO probe, the Cu2O/Ag5 nanocomposite showed the highest SERS activity of all samples with the limit of detection as low to 1 nM and the enhancement factor as high as 4 × 108. The logarithm of the SERS peak intensity at 1389 cm-1 increased linearly with the logarithm of the concentration of MO in the range from 1 nM to 0.1 mM.

Sensitive detection of chromium (VI) using Au-NPs/MWCNT/chitosan composite via electrochemical approach

A glassy carbon electrode (GCE) was nanostructurally modified with a scaffold of gold nanoparticles (AuNPs), multiwalled carbon nanotubes (MWCNTs) and chitosan (Chit) for a sensitive detection of hexavalent chromium Cr(VI) in aqueous solutions. Each step of modification was analyzed and characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Strong interfacial adhesion between gold nanoparticles and porous nanostructure of MWCNTs-Chit was depicted. This scaffold uniformly distributed hydroxyl and carboxylate groups, as well as amine group throughout the surface of glassy carbon electrode, and gold nanoparticles adhered to carbon nanotubes wall inside the polymeric matrix. This scaffold selectively coordinated and preconcentrated the chromate ions for ulterior Cr(VI) detection. Under the optimized conditions (deposition potential: + 0.8 V vs. SCE, deposition time: 120 s), differential pulse voltammetry (DPV) electroanalysis results indicated the linear increment of electrochemical signals with an increase in the concentration of Cr(VI). Fabrication of a calibration curve was performed in a concentration range of 0.003–0.1 μg L−1 and limit of detection (LOD, 3σ/m) was calculated as 0.007 μg L−1. This nanostructured electrochemical sensor coupled with differential pulsed voltammetry, constitutes a very effective prospective capable of high sensitivity, selectivity, precision, accuracy, and rapid trace determination of hexavalent chromium ion in aqueous medium.

A New Mapping Protocol for Laser Ablation (withFast‐Funnel) Coupled to aTime‐of‐FlightMass Spectrometer (LA‐FF‐ICP‐ToF‐MS) for the Rapid, Simultaneous Quantification of Multiple Minerals

Althoughin situanalysis by LA‐ICP‐MS is considered a rapid technique with minimal sample preparation and data reduction, mapping areas of millimetres in size using a small beam (< 15 μm) can be time consuming (several hours) when a quadrupole ICP‐MS is used. In addition, fully quantitative imaging using internal standardisation by LA‐ICP‐MS is challenging in samples with more than one mineral phase present due to varying ablation rates. A new protocol for the quantification of multiple coexisting phases, mapped at a rate of about 12 mm2h‐1and a resolution of 12 μm × 12 μm per pixel, is presented. The protocol allows mapping of most atomic masses, ranging from23Na to238U, using a time‐of‐flight mass spectrometer (ICP‐ToF‐MS, TOFWERK) connected to a 193 nm excimer laser. A fast‐funnel device was successfully used to increase the aerosol transport speed, reducing the time usually required for mapping by a factor of about ten compared with a quadrupole ICP‐MS. The lower limits of detection for mid and heavy masses are in the range 0.1–10 μg g‐1, allowing determination of trace to ultra‐trace elements. The presented protocol is intended to be a routine analytical tool that can provide greater access to the spatial distribution of major and trace elements in geological materials.

Development of a New and Facile Carrier Element-Free Coprecipitation Procedure for Separation, Preconcentration and Sensitive Determination of Cu(II) and Cd(II) Ions in Water and Vegetable Samples

A facile and sensitive method predicated on carrier element free coprecipitation (CEFC) using 2-(2-(2-(4-bromobenzyl)-1H-benzo[d]imidazole-1-yl)acetyl)-N-ethylhydrazine-1-carbothioamide (BIMANEC) is reported for trace determination of Cu(II) and Cd(II) in vegetables and water. BIMANEC was used for the first time for the quantitative determination of these trace heavy metals. Flame atomic absorption spectrometer (FAAS) was used for quantitation. The preconcentration conditions were optimized with respect to pH (8.0), BIMANEC mass (4.0 mg), volume of sample (100 mL), standing time (5 min), and centrifugation time and rate (3 min and 2500 rpm). The influence of potentially interfering ions was scrutinized for the recovery of analyte ions. Under the optimum conditions, the limits of detection (LODs) were 0.51 and 2.28 µg L−1 for Cu(II) and Cd(II), respectively. The relative standard deviations were < 5% for both. The recoveries from the spiked vegetable samples were from 94.9 to 102.8% and from the spiked water samples between 93.2 and 101.6%. Consequently the developed new, facile, rapid, and highly efficient CEFC process was employed for the trace determination of Cu(II) and Cd(II).

QbD green analytical procedure for Novel study of a genotoxic and carcinogenic compound trace determination in physiological solution compatibility

Regulatory bodies more focusses on the safety and efficacy of the pharmaceuticals, through this work we want to express the necessary control of 5-Hydroxymethyl furfural (5-HMF) impurity level in intra-venous (IV) injections. Genotoxic and carcinogenic compound 5-HMF determination in IV injections was determined by using the simple, sensitive, green, and eco-friendly HPLC method. Box-Behnken Design (BBD) was utilized to optimize the final method conditions prior to method validation, resulting in 15 design of experiments (DOE) using critical method parameters (CMPS) and critical assumptions. The identification and quantification were done with Phenomenex prodigy C8 (150 × 4.6) mm, 5 μm column with a flow rate of 0.6 mL/min. The peak detection was done at 284 nm and with a total run time of 6 min. The mobile phase consists of 0.1 M potassium dihydrogen phosphate (PDP) pH 2.5 buffer and acetonitrile (ACN) in the ratio of 80:20 (v/v) used for the isocratic elution. The method was validated as per the current regulatory guidelines. The accuracy results from LOQ to 150% level were attained between 95.1% and 103.4%. The 5-HMF response is linear from LOQ to 150% with a correlation coefficient (r) > 0.999. The %coefficient of variation (CV) from method precision and intermediate precision (n = 6) results were found to be 1.67% and 3.45%, respectively. Trace analysis of 5-HMF was done in selected IV injections Pancuronium Bromide (PMB), Meropenem (MPM), Doripenem (DPM), and Cefotaxime (CTM) injections at different time points. The method greenness was evaluated by utilizing the Green analytical procedure index (GAPI), Analytical GREEness (AGREE), National environmental procedure index (NEMI), and analytical eco-scale and concluded that the method is green.

Spectrophotometric Assay ofMetoclopramide in PharmaceuticalPreparations

A sinple and sensitive photometric rnethod for the trace determination of metoclopramide lras been worked olri .The rnethod is based on the diazotization reaction of the detet'tnination in acidic medium with the coupled o,-naphthol,to form purplisli violet water soiubie azo dye that shows maximurn absorption at 549nm with molir absorbtivity of 3.85x104 l.mol-l.cm-l.Bee.'s larv is obeyed over the concentration range 12.5-200pg of metoclopramide in final volume of 25m1,i.e.0.5-8pprn with the relative enor of -0.2 - +1.3 atrd a relative standard deviation 0.68-2.17%.Morever,the method does not require either temperature

Dual-monomer molecularly imprinted electrochemical sensor based on amino-functionalized MOFs and graphene for trace determination of taurine.

Amolecularly imprinted electrochemical sensor (MIECS) for trace determination of taurine was developed. The sensor was constructed by electropolymerizing dopamine and o-phenylenediamine as dual monomers on the surface of amino-functionalized iron-based MOFs and graphene composite-modified electrode. The porous structure and large specific surface area of amino-functionalized iron-based MOFs not only increase the number of imprinted sites, but also facilitate the binding of molecularly imprinted films. The presence of dual monomers can increase the binding sites during the formation of imprinted films. The linear range of this sensor for taurine detection is 1.00 × 10-14-1.00 × 10-8mol L-1 with a determination limit of3.20 × 10-15mol L-1. The proposed MIECS was successfully applied to quantify the amount of taurine in human serum sample with good recovery values from 97.3 to 113%.

Combination of switchable hydrophilic solvent liquid-liquid microextraction with QuEChERS for trace determination of triazole fungicide pesticides by GC-MS.

This work first proposed a novel green and efficient method based on Quick, Easy, Cheap, Efficient, Rugged, and Safe pretreatment (QuEChERS) combined with switchable hydrophilic solvent homogeneous liquid-liquid microextraction (SHS-HLLME) for trace determination of triazole fungicides (TFs) in agricultural products such as vegetables and fruits by gas chromatography-mass spectrometry (GC-MS). N,N-Dimethyl benzylamine was used for the synthesis of SHS. Box-Behnken design was applied for the optimization of extraction conditions and a mathematical model was obtained. Ultimately, 0.50mL SHS, 1.0mL 10molL-1 sodium hydroxide, and 45s ultrasonic time were determined as optimal conditions for the SHS-HLLME method. The limit of detection and limit of quantification determined using the optimal method (SHS-HLLME/GC-MS) were 0.13-0.27ngmL-1 and 0.43-0.90ngmL-1, respectively. In addition, the SHS-HLLME method under optimal conditions was combined with the traditional QuEChERS method to realize the advancement of the SHS-HLLME method from simple to complex matrix analysis, and the QuEChERS-SHS-HLLME method was successfully applied to the analysis of TFs in cucumbers, tomatoes, watermelon and grapes in agricultural products. Matrix-matched calibration standards were used to improve the accuracy of TFs in spiked cucumber samples to obtain recovery results close to 100%. It was shown that the new method is green and rapid, enabling fast and inexpensive sample pretreatment with up to 100-fold enrichment factor and low detection limit compared with the original QuEChERS method.

Voltammetric quantitative analysis of vildagliptin in bulk form and spiked human serum at a modified electrode

The electrochemical behavior of Vildagliptin (VILD) was studied using the cyclic voltammetric technique in an aqueous Britton–Robinson (BR) universal buffer solution of various pH levels between 4.0 and 10 at a 5% calcium-montmorillonite clay modified with carbon paste electrode surface (5% Ca-MMT/CPE). The results exhibited an irreversible anodic peak at about 1.238 V versus Ag/AgCl, KCl (3 mol L−1). The anodic peak was found to be diffusion–adsorption controlled. The possible reaction mechanism is estimated taking into consideration of the calculated electrons and protons number transferred on the electrode/electrolyte interface using the cyclic voltammetric technique. VILD was found to adsorb onto the surface of 5% Ca-MMT/CPE in a monolayer surface coverage of 3.0 × 10−12 mol cm−2. A validated square wave voltammetry (SWV) technique for VILD determination was performed. The calibration curve of VILD onto the 5% Ca-MMT/CPE surface was linear in the concentration range of 1.0–110 nmol L−1 with the mean limits of detection and quantification was 0.285 and 0.950 nmol L−1, respectively, in the bulk form. The proposed procedure for the assay of VILD in bulk form, dosage form, and spiked human serum has the advantage of being simple, rapid, sensitive, and inexpensive compared to other analytical methods. The described method showed an excellent performance for the trace determination of VILD in its formulation without interference from excipients.Graphical abstract

Flexible SERS strip based on HKUST-1(cu)/biomimetic antibodies composite multilayer for trace determination of ethephon

A surface-enhanced Raman scattering (SERS) sensor based on the folding and assembly characteristics of the three-dimensional structure of paper fibers, the skeleton controllability of metal-organic framework materials (MOFs), and the morphology designability of plasmonic noble metal materials has been established for rapid on-site determination of ethephon in food. HKUST-1(Cu) was assembled onto a carbon-treated chromatographic paper matrix by electrodeposition, and its skeleton respiration and sponge effect were used to overcome the bottleneck problem of poor affinity of SERS substrate for target molecules. Further coupled with the targeted recognition specificity of biomimetic antibodies, a paper-based interface with high specificity of molecular sensitivity was constructed. A sandwich multi-stage progressive enhancement structure was designed to couple plasma pine branch-shaped silver material in situ at the interface to realize superposition and collaborative amplification of SERS signals. When the paper-based strip sensor was used to monitor ethephon, it demonstrated a linear range of 10−3 to 10 mg kg−1 and a detection limit of around 1.39 × 10−4 mg kg−1. The construction and application of the paper-based HKUST-1(Cu)/biomimetic antibodies/pine branch-shaped silver material sensor will provide technical means and theoretical support for the rapid and efficient identification of biological ripening agent residues in food with multi-level signal enhancement.

An overall validation approach based on β-content, γ-confidence tolerance interval and uncertainty profile: Application for LC-MS/MS quantification of Carbendazim in drinking water.

The Carbendazim is a fungicide which can seep into the water supply, presenting a public health risk, therefore the accurate trace determination of this substance is very important. The purpose of the study is to perform a top-down analytical validation approach in order to determine the amount of Carbendazim in drinking water by using an SPE-LC/MS-MS technique. Quantification of Carbendazim using solid-phase extraction coupled with LC/MS-MS in order to ensure the accuracy of the analytical method and to master the risk of its routine application. An overall validation methodology based on two side tolerance interval type β-content, γ-confidence has been applied for the validation and estimation of uncertainty by building a decision graphical tool called "uncertainty profile" by using the statistical process known as the "Satterthwaite approximation" with no recourse to supplementary data by satisfying intermediate precision condition for each concentration level within the acceptance limits fixed in advance. As a result, the process of the validation is based on the selection of a linear weighted 1/X model enabling validation of the Carbendazim dosage using LC/MS-MS in the range of working concentrations as the β γ-CCTI fell inside acceptable limits of ± 10%, and the relative expanded uncertainty didn't surpass 7% regardless of the β values (66.7%, 80%, 90%) and the 1- γ=risk (10%, 5%). The application of the Uncertainty Profile approach for full validation of a SPE-LC/MS-MS assay for the quantification of carbendazim has been successfully achieved.

Application of nano-LC – nano-ESI – Orbitrap-MS for trace determination of four priority PFAS in food products considering recently established tolerable weekly intake (TWI) limits

An analytical method was developed and validated for the analysis of four priority perfluoroalkyl substances (PFAS), namely, perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorohexanesulfonic acid (PFHxS), and perfluorooctanesulfonate (PFOS) in food products using nanoscale liquid chromatography (nano-LC) coupled with nanoscale electrospray ionization (nano-ESI) and Orbitrap mass spectrometry (Orbitrap-MS) detection. The efficiency of two different nano-LC setups for chromatographic separation of selected PFAS was evaluated. The optimal LC separation of analytes was achieved using a reversed phase C18 (RP-C18) nano bore column with an integrated emitter. The effect of matrix concentration factor on signal suppression/enhancement was evaluated for different matrices. The method validation indicated analyte recoveries in the range 83–118% and within-laboratory reproducibility from 7 to 18%, while reanalysis of the materials from proficiency tests (PTs) showed that the accuracy of the obtained concentrations ranged from 85 to 124% of the provided consensus values. The method limits of quantification (m-LOQs) were set as first validation levels ranging from 0.001 to 0.3 ng g−1 sample depending on the type of the food group. The observed method performance characteristics met the criteria stated in Commission Regulation (EU) 2022/1428, Commission Recommendation (EU) 2022/1431, as well as Guidance Document on Analytical Parameters for the Determination of Per- and Polyfluoroalkyl Substances (PFAS) in Food and Feed with regards to the compliance testing of PFAS maximum levels (MLs) and monitoring purposes. The elaborated method was applied for the analysis of selected priority PFAS in different food groups collected from the Latvian retail market.

Anchoring Au on UiO-66 surface with thioglycolic acid for simultaneous SERS detection of paraquat and diquat residues in cabbage

SERS sensors based on metal-organic frameworks (MOFs) have garnered considerable attention in trace pesticide residue detection. UiO-66/AuNPs suspension substrates were fabricated by introducing thioglycolic acid (TGA) as a binder to modify the surface of AuNPs to facilitate their electrostatic assembly with UiO-66 prepared through hydrothermal reaction. The proposed substrates were used for quantitative and simultaneous analysis of paraquat and diquat in cabbage. Diquat and paraquat in actual cabbage samples were individually analysed with detection of limits (LOD) of 6 μg/L and 3 μg/L, respectively, and validated with recoveries ranging from 92.65 to 118.34%. Furthermore, the UiO-66/AuNPs substrate was able to differentiate between paraquat and diquat mixtures, even for the concentrations in the cabbage extracts differed by a factor of 100. The proposed UiO-66/AuNPs substrate provides a potentially useful tool for the trace determination of pesticide residues in the practical food safety analysis

An Innovative Polymer-Based Electrochemical Sensor Encrusted with Tb Nanoparticles for the Detection of Favipiravir: A Potential Antiviral Drug for the Treatment of COVID-19.

An innovative polymer-based electro-sensor decorated with Tb nanoparticles has been developed for the first time. The fabricated sensor was utilized for trace determination of favipiravir (FAV), a recently US FDA-approved antiviral drug for the treatment of COVID-19. Different techniques, including ultraviolet-visible spectrophotometry (UV-VIS), cyclic voltammetry (CV), scanning electron microscope (SEM), X-ray Diffraction (XRD) and electrochemical impedance spectroscopy (EIS), were applied for the characterization of the developed electrode TbNPs@ poly m-THB/PGE. Various experimental variables, including pH, potential range, polymer concentration, number of cycles, scan rate and deposition time, were optimized. Moreover, different voltammetric parameters were examined and optimized. The presented SWV method showed linearity over the range of 10-150 × 10-9 M with a good correlation coefficient (R = 0.9994), and the detection limit (LOD) reached 3.1 × 10-9 M. The proposed method was applied for the quantification of FAV in tablet dosage forms and in human plasma without any interference from complex matrices, obtaining good % recovery results (98.58-101.93%).

Fabrication of nanostructured ZnNiBi-NO3 layered double hydroxides for speciation and preconcentration/separation of chromium ions prior to MIS-FAAS determination

ABSTRACT Nanostructured ZnNiBi-NO3-Layered Double Hydroxides (LDHs) was synthesised, followed by the simple co-precipitation method using Zn(NO3)2.6 H2O, Ni(NO3)2.6 H2O and Bi(NO3)3 as the precursors. Synthesised LDHs was characterised by various techniques such as infrared (IR) spectroscopy, x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray (EDX) and thermal gravimetric analysis (TGA). ZnNiBi-NO3 LDHs were applied as efficient adsorbents for speciation analysis and preconcentration/separation of Cr(VI)/Cr(III) ions in aqueous samples prior to their trace determinations by microsample injection system-coupled flame atomic absorption spectrometry (MIS-FAAS). ZnNiBi-NO3 LDHs worked well for speciation and preconcentration/separation of Cr(VI)/Cr(III) ions at an optimum of pH 3.0 and adsorbent dosage of 400 mg. LOD and LOQ of Cr(VI) ions were calculated to be 0.03 and 0.10 μg L−1, respectively with a preconcentration factor of 400. The total saturation capacity of ZnNiBi-NO3 LDHs for Cr(VI) ions was investigated and found to be 46.0 mg g−1. The mthod was reproduced with RSD ≤1.4% of five replicates. The accuracy of method was evaluated by analysing 10–100 μg L−1 Cr(VI) ions standard solutions, and Cr(VI) ions were recovered ≥96.9% with RSD ≤2.4%. The developed method worked well on wastewater samples.

An environmentally friendly approach for the characterization of construction materials: determination of trace, minor, and major elements by slurry sampling high-resolution continuum source graphite furnace atomic absorption spectrometry.

A slurry sampling method was developed for the fast determination of Pb, Ni, Fe, and Mn in construction materials by high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GFAAS). For sample introduction into the GF, stable slurries were prepared by sonicating 10 mg of ground solid sample in 10.0 mL of 1% (v/v) Triton X-100 and 1% (v/v) HNO3 solution for 1.0 min. The determination of the four elements was carried out in three measurement runs, with Ni and Fe being determined simultaneously. The HR-CS GFAAS measurements were performed using analytical lines with adequate sensitivity, considering the content of each element in the material: Pb at 283.306 nm (42%), Mn at 403.080 nm (6.7%), Ni at 232.003 nm (100%) and Fe at 232.036 nm (1.4%). The pyrolysis and atomization temperatures and the use of chemical modifiers were optimized using both aqueous standards and slurry samples. At optimal conditions, samples with concentrations of Pb from 1.5 to 80 μg g-1, Ni from 4.0 to 75 μg g-1, Mn from 2.0 to 600 μg g-1, and Fe from 0.15 to 60 mg g-1 could be determined using a unique sample suspension. To assess the validity of the method, a fly ash certified reference material (CRM) was analysed using the slurry sampling HR-CS GFAAS method; this CRM and the construction material samples were also analysed by HR-CS GFAAS after the digestion of the samples. The obtained results using both methods were statistically comparable (Student's paired t-test for two independent methods at a 95% confidence level) demonstrating the suitability of the proposed method.

A Rapid Determination of 30 Prohibited Pesticide Residues in Lycii Fructus by UPLC-MS/MS

Prohibited pesticide residues have become one of the main factors affecting the quality and safety of Lycii Fructus, However, rarely studies focus on the rapid determination of these residues. Here, a total of 30 kinds of prohibited pesticide residues were determined by ultra-performance liquid chromatography tandem triple quadrupole mass spectrometry (UPLC-MS/MS) in five different process ways. Pretreatment methods, chromatographic separation and detection conditions in mass spectrometry were all optimized accordingly. Among the five different pretreatment methods, the first and third solid phase extraction failed to provide high recoveries of sulfosulfuron compounds (both lower than 60%). Recovery of chlorphenamidine by the Quick Easy Cheap Effective Rugged and Safe multiresidue method (QuEChERS) was lower than 60%, which did not meet the requirements of trace determination. The concentrations of 30 prohibited pesticides residues treated by straightforward and solid phase extraction showed good linearity in their corresponding ranges, with correlation coefficients over 0.99. The average recoveries of straightforward ranged from 78.13% to 110.9%, while RSD ranged from 1.3% to 16.9%, albeit poor purification was observed. The recovery yield from solid phase extraction was between 67.75% and 103.08% with RSD value from 0.8% to 14.0%, which met the requirements of trace determination, this method has good precision and stability. These results could be employed to other Traditional Chinese Medicines (TCMs) in detecting prohibited pesticide residues.

Development of two highly sensitive and selective sensor-assisted fluorescence immunoassays for trace determination of copper residues in food samples.

This study describes the development of two highly sensitive and selective sensor-assisted fluorescence immunoassays for the trace determination of copper ions, Cu(ii) residues, in food samples. These assays were the microwell-based fluoroimmuoassay (FIA) and the kinetic exclusion assay (KinExA). FIA and KinExA were assisted by a microplate reader and a KinExA™ 3200 immunosensor, respectively. Both FIA and KinExA were developed utilizing the same antibody, capturing reagent, and fluorescence signal-generating reagent. The antibody was a mouse monoclonal antibody, designated as 8D66, that specifically recognized the Cu(ii)-ethylenediaminetetraacetic acid complex (Cu(ii)-EDTA) but did not recognize Cu(ii)-free EDTA. The capturing reagent was Cu(ii)-EDTA covalently linked to bovine serum albumin protein (Cu(ii)-EDTA-BSA). The fluorescence-generating reagent was an anti-mouse IgG conjugated with fluorescein isothiocyanate (IgG-FITC). Both FIA and KinExA involved competitive binding reactions between Cu(ii)-EDTA complexes, formed in the sample solution, and Cu(ii)-EDTA-BSA conjugate which has been immobilized onto microwell fluorescence assay plates (in FIA) or polymethylmethacrylate beads (in KinExA) for a limited quantity of binding sites of 8D66 antibody. The conditions of both FIA and KinExA were investigated, and the optimum procedures were established. Both FIA and KinExA were validated, and all validation parameters were acceptable. Many different metal ions that are commonly encountered in food samples did not interfere with Cu(ii) analysis by both FIA and KinExA. Both assays were applied to the determination of Cu(ii) in food samples with satisfactory accuracy and precision. Both assays were compared favorably with inductively coupled plasma atomic emission spectroscopy. Comparative evaluation of FIA and KinExA revealed that KinExA had higher sensitivity and better precision than FIA, whereas, both assays had comparable accuracy. Both FIA and KinExA were superior to the existing atomic spectrometric methods for Cu(ii). The proposed FIA and KinExA are anticipated to effectively contribute to assessing Cu(ii) concentrations and controlling the exposure of humans to its potential toxicities.