Hollow fiber-stir bar sorptive extraction and microwave assisted derivatization of amino acids in biological matrices

Hollow fiber membrane-protected amino/hydroxyl bifunctional microporous organic network fiber for solid-phase microextraction of bisphenols A, F, S, and triclosan in breast milk and infant formula

Bisphenols and triclosan have been used in various products, and exposure to these chemicals may affect human health. The present study proposes a sensitive method for the determination of bisphenols A, F, S, and triclosan. The fiber was coated by amino/hydroxyl bifunctional microporous organic network and protected by polyvinylidene fluoride hollow fiber membrane for direct immersion solid phase microextraction. The limit of detection was 0.005 μg/L (μg/kg), and the recoveries were in the range of 76.7% to 107.5% (87.4% to 107.6%) for breast milk (infant formula), with intra-day and inter-day precisions <10.5% (7.3%) and 13.6% (8.4%), respectively. Fiber-to-fiber reproducibility of < 9.5% and a lifespan of >100 cycles were obtained. The 95th percentile estimated daily intake of total bisphenols was close to temporary tolerable daily intake for infants fed by human milk, which highlighted the needs for further attention on human exposure to BPA and its substitutes.

Metabolic Profiling and Quantitative Analysis of Cerebrospinal Fluid Using Gas Chromatography-Mass Spectrometry: Current Methods and Future Perspectives

Cerebrospinal fluid is a key biological fluid for the investigation of new potential biomarkers of central nervous system diseases. Gas chromatography coupled to mass-selective detectors can be used for this investigation at the stages of metabolic profiling and method development. Different sample preparation conditions, including extraction and derivatization, can be applied for the analysis of the most of low-molecular-weight compounds of the cerebrospinal fluid, including metabolites of tryptophan, arachidonic acid, glucose; amino, polyunsaturated fatty and other organic acids; neuroactive steroids; drugs; and toxic metabolites. The literature data analysis revealed the absence of fully validated methods for cerebrospinal fluid analysis, and it presents opportunities for scientists to develop and validate analytical protocols using modern sample preparation techniques, such as microextraction by packed sorbent, dispersive liquid-liquid microextraction, and other potentially applicable techniques.

In situ growth of copper-based metal-organic framework on a helical shape copper wire as a sorbent in stir-bar sorptive extraction of fenthion followed by corona discharge ion mobility spectrometry

In this paper, a helical copper wire, coated with copper-benzene-1,4-dicarboxylic acid metal-organic framework (Cu-BDC) was used as a sorbent for stir-bar sorptive extraction of fenthion from water and fruit samples. The homogenous coating was fabricated through two simple and fast steps. The chemical conversion of copper substrate to copper hydroxide nanotubes (Cu(OH)₂ NTs) was performed in an alkaline solution and then Cu-BDC was formed through a neutralization reaction. Corona discharge ion mobility spectrometry in positive mode was applied for the detection of fenthion. To improve the sensitivity of the method, some synthesis and extraction parameters affecting the extraction efficiency such as benzene-1,4-dicarboxylic acid concentration, ionic strength, sample pH, stirring rate, extraction temperature, and extraction time were investigated. The linear dynamic range between 0.5 and 80 μg L^-1 and detection limit of 0.1 μg L^-1 were obtained under optimal conditions. The intra- and inter-day relative standard deviations were less than 6.4 and 8.6%, respectively. The applicability of the method was examined for the analysis of different samples (i.e., well water, agricultural wastewater, and orange). The recovery for the determination of fenthion in spiked samples varied from 88 to 111%.

Fabrication of carboxyl functionalized microporous organic network coated stir bar for efficient extraction and analysis of phenylurea herbicides in food and water samples

Fabrication of novel coatings continues to be an area of great interest and significance in the development and application of stir bar sorptive extraction (SBSE). In this work, a carboxyl-enriched microporous organic network (MON-2COOH) coated stir bar was designed and fabricated as a novel adsorbent for efficient extraction of four phenylurea herbicides (PUHs) before their determination by high-performance liquid chromatography coupled with photodiode array detector (HPLC-PDA). The MON-2COOH was represented as an effective adsorbent for PUHs due to its large surface area, rigid porous structure, aromatic pore walls and the desired hydrogen bonding sites of introduced carboxyl groups. Variables affecting the SBSE of target analytes were optimized in detail. Under the optimal extraction conditions, favorable correlation coefficients (R² > 0.996) in the linear range 0.10-250 μg L^-1, low limits of detection (LODs, S/N = 3) of 0.025-0.070 μg L^-1 and good enrichment factors (46-49) were obtained. Besides, the proposed SBSE-HPLC-PDA method was successfully applied to determine trace PUHs in food and environmental water samples with recoveries in the range of 80.0-104.8% and the precisions (relative standard deviations, RSDs) lower than 9.9% (n = 3). This work revealed the potential of MONs in SBSE of trace contaminants from environmental samples.

Surface area expansion by flower-like nanoscale layered double hydroxides for high efficient stir bar sorptive extraction

Enhancing the surface area of stationary phase is essential in chromatographic science. In this work, nanoscale NiAl-layered double hydroxides (NiAl-LDHs) with flower-like structure was used as a platform for supporting the stationary phase. Then strong hydrophobic p-naphtholbenzein molecule was immobilized onto the LDHs layer as sorbent for stir bar sorptive extraction (SBSE). The flower-like LDHs layer significantly increased the extraction efficiency through increasing the specific surface area and immobilized amounts of stationary phase. In addition, the LDHs can also provide anion exchange ability, which expanded the application of this stir bar for analysis of not only hydrophobic but also anionic analytes. For improving the workability, a poly(ether ether ketone) (PEEK) jacket stir bar with detachable dumbbell-shaped structure was employed. The PEEK jacket with high mechanical strength and dumbbell-shaped structure improved the durability of stir bar and the detectable design allowed elution to be realized with less solvent that enhanced the enrichment factor. The proposed stir bar showed good performance for the extraction of multiple analytes including flavonoids, non-steroid anti-inflammatory drugs and chlorophenoxy acids. By coupling with high performance liquid chromatography-ultraviolet detection (HPLC-UV), the SBSE-HPLC-UV method was applied for the extraction of three active components including bavachin, isobavachalcone and bavachinin in Psoralea corylifolia L. herb with low limit detection of 0.01-0.02 ng/mL.

Analysis of Pesticide Residue in Tomatoes by Carbon Nanotubes/β-Cyclodextrin Nanocomposite Reinforced Hollow Fiber Coupled with HPLC

For addressing the issues of pesticide residue analysis characterized by the trace levels of target analytes and the complexity of sample matrices, a selective extracting material, carbon nanotubes (CNTs)/β-cyclodextrin (β-CD) nanocomposite reinforced hollow fiber (HF), was developed. CNTs were chemically modified with β-CD and then the resultant nanocomposite was immobilized into the wall pores and lumen of HF by sol-gel technology. The reinforced HF was applied to direct-immersion mode of solid phase microextraction for the determination of carbaryl and 1-naphthol in tomatoes, coupled with high performance liquid chromatography. The proposed method provided 240- and 215-fold enrichment factors, good linearity in the range of 0.6 to 600 ng/g and 0.2 to 600 ng/g, good repeatability with RSDs of 4.5% and 6.9%, and batch-to-batch reproducibility with RSDs of 7.4% and 8.3% for 1-naphthol and carbaryl, respectively. Moreover, the low limits of detection at 0.05 and 0.15 ng/g for 1-naphthol and carbaryl, respectively, along with the high recovery in the range of 84.2% to 108.9% were obtained. The results showed that the material combined the respective advantages of CNTs, β-CD, and HF, thus, exhibiting efficient adsorption property, outstanding molecular recognition performance, and excellent sample clean-up effect, and it is applicable for pesticide residue analysis in complex matrices. PRACTICAL APPLICATION: The developed extracting material can be used for pesticide residue analysis of tomatoes. Pesticides, carbaryl, and 1-naphthol were detected in tomatoes, the most popular vegetable grown and consumed globally. The results supported the necessity to monitor pesticide residue for public health.

Determination of nitrofuran metabolites in marine products by high performance liquid chromatography–fluorescence detection with microwave-assisted derivatization

A sensitive method for simultaneous detection of four nitrofuran metabolites (3-amino-2-oxazolidinone (AOZ), semicarbazide (SEM), 3-amino-morpholinomethyl-2-oxazolidinone (AMOZ) and 1-aminohydantoin (AH)) in marine products.

Switchable polarity solvents for preconcentration and simultaneous determination of amino acids in human plasma samples

The application of a mixture of amidine and alcohol as a switchable polarity solvent for the microextraction of 19 amino acids in biological samples.