Sol–gel niobia sorbent with a positively charged octadecyl ligand providing enhanced enrichment of nucleotides and organophosphorus pesticides in capillary microextraction for online HPLC analysis

A niobia‐based sol–gel organic–inorganic hybrid sorbent carrying a positively charged C₁₈ ligand (Nb₂O₅‐C₁₈(+ve)) was synthesized to achieve enhanced enrichment capability in capillary microextraction of organophosphorus compounds (which include organophosphorus pesticides and nucleotides) before their online analysis by high‐performance liquid chromatography. The sorbent was designed to simultaneously provide three different types of molecular level interactions: electrostatic, Lewis acid–base, and van der Waals interactions. To understand relative contributions of various molecular level analyte–sorbent interactions in the extraction process, two other sol–gel niobia sorbents were also created: (a) a purely inorganic sol–gel niobia sorbent (Nb₂O₅) and (b) an organic–inorganic hybrid sol–gel niobia sorbent carrying an electrically neutral‐bonded octadecyl ligand (Nb₂O₅‐C₁₈). The extraction efficiency of the created sol–gel niobia sorbent (Nb₂O₅‐C₁₈ (+ve)) was compared with that of analogously designed and synthesized titania‐based sol–gel sorbent (TiO₂‐C₁₈ (+ve)), taking into consideration that titania‐based sorbents present state‐of‐the‐art extraction media for organophosphorus compounds. In capillary microextraction with high‐performance liquid chromatography analysis, Nb₂O₅‐C₁₈ (+ve) had shown 40–50% higher specific extraction values (a measure of extraction efficiency) over that of TiO₂‐C₁₈ (+ve). Compared to TiO₂‐C₁₈(+ve), Nb₂O₅‐C₁₈(+ve) also provided superior analyte desorption efficiency (96 vs. 90%) during the online release of the extracted organophosphorus pesticides from the sorbent coating in the capillary microextraction capillary to the chromatographic column using reversed‐phase high‐performance liquid chromatography mobile phase.     

Solid-phase extraction of carotenoids

In this work, solid-phase extraction (SPE) trapping performance of lutein and β-carotene, which were used as the model molecules of carotenoids, was investigated. The absorption, elution, and enrichment of carotenoids on SPE cartridges with four different sorbents, i.e. C₃₀, C₁₈, diol, and silica, were compared respectively with the help of frontal analysis technique. The high retentions of both lutein and β-carotene were achieved on the C₁₈ and C₃₀ cartridges. The diol and silica cartridges only had good retention for lutein. The optimized SPE method for sample pretreatment for the carotenoids analysis was obtained after the investigation of trapping performance. The method was applied successfully to the analysis of biological sample, i.e. serum and human breast milk. The recovery, accuracy, and precision of SPE method comparing with those of traditional liquid–liquid extraction (LLE) method for the sample pretreatment for the analysis of carotenoids owned a number of advantages such as rapid, no chloroform used, and accurate versus LLE.     

Measurement of bisphenol A in human serum by gas chromatography/mass spectrometry

The purpose of this study is to establish an easy and accurate method for the determination of bisphenol A (BPA) in the human serum. The samples were applied to the C₁₈ solid phase extraction (SPE) column for clean up of samples. The BPA is conjugated with tetrabutylammonium hydrogen sulfate as the counter ion in alkali solution. The ion paired BPA is moves from the aqueous phase to the organic phase as an ion paired extraction. BPA extracted from human serum were derivatized with pentafluorobenzyl bromide (PFBBr). The derivative was analyzed by gas chromatography (GC)/mass spectrometry (MS) using negative chemical ionization (NCI). The instrumental detection limit of BPA was 5 pg/ml (10 fg). The instrumental response between 0.01 and 100 pg/ml of BPA standards was linear (r²=0.998). The recovery of BPA spiked into human serum was 101.0±4.63 (1 pg/ml) and 100.9±3.75 (10 pg/ml), respectively. The concentration of BPA in the human serum from 20 individuals was 0.54 pg/ml.     

Evaluation of a novel silica-supported sol–gel sorbent prepared by a surface molecular imprinting technique for the selective separation of estazolam from human plasma

A molecular imprinting polymer (MIP) based on surface modification of silica gel was prepared via the sol–gel process with 3-aminopropyltriethoxysilane and phenyltrimethoxysilane as functional monomers, and estazolam as the template. The imprinted silica sorbent was characterized by Fourier Transform Infrared Spectroscopy, surface elemental analysis, and scanning electron microscopy (SEM). An MIP of agglomerated nano-particles with multi-pores was grafted onto the surface of the silica gel after hydrolytic condensation of the siloxane. The imprinted silica sorbent was used for solid phase extraction (SPE). Using water as loading solvent, the extraction efficiency for estazolam was higher compared to the use of an organic solvent. The imprinted silica sorbent was selective not only for the template, but also for the analogue. Compared to C₁₈-SPE and liquid–liquid extraction, the MIP-SPE was the most feasible technique for extraction of estazolam from human plasma; up to 98.7?±?1.2% recovery was achieved.     

Preparation and Application of a Novel Silica-Supported Organic-Inorganic Hybrid Molecular Imprinting Polymer

Abstract

A novel estazolam-imprinted silica sorbent was prepared by the surface imprinting technique using 3-aminopropyltriethoxysilane (APTEOS) and phenyltrimethoxysilane (PTMOS) as functional monomers. The functional monomers are expected to form hydrogen bonds and π-π interactions with estazolam. The imprinted silica sorbent was characterized by Fourier transform infrared spectroscopy (FT-IR), element analysis, and scanning electron micrograph (SEM). Compared to C₁₈ solid phase extraction (SPE) and liquid-liquid extraction, molecular imprinting polymer (MIP) SPE was the most feasible method to extract estazolam from human plasma, and the recovery of estazolam was up to 98.7±1.2%.     

SPE of Tanshinones from Salvia miltiorrhiza Bunge by using Imprinted Functionalized Ionic Liquid-Modified Silica

Ionic liquid-modified silica, with functional groups based on imidazole as the cation, was obtained. A molecular imprinting technique was introduced to form the order of functional groups. The selectivity of the obtained ionic liquid-modified silica was successfully used as a special imprinted sorbent in the solid-phase extraction to isolate cryptotanshinone, tanshinone I and tanshinone IIA from Salvia miltiorrhiza Bunge. Several washing and elution solvents with different polarities were evaluated. The ionic liquid-modified silica as the sorbent exhibited a higher selectivity than blank ionic liquid-modified silica, traditional silica and C₁₈ cartridges. A quantitative analysis was conducted by liquid chromatography with a C₁₈ column and methanol/water (75:25, v/v, containing 0.5% acetic acid) as the mobile phase. A good linearity was obtained from 0.5 × 10^?4 to 0.1 mg mL^?1 (r ²  > 0.99) with relative standard deviations that were less than 4.6%.     

Determination of Propylthiouracil in Human Breast Milk by Direct Injection High Performance Liquid Chromatography

Abstract

A high-performance liquid chromatographic(HPLC) method was developed for the assay of propylthiouracil in human breast milk. After filtration with membran filter(Molcut II), the eluent was injected into a liquid chromatogaph equipped with C₁₈ precolumn and analytical column in series according to column switching techniques. This method is sufficiently sensitive for most pharmacokinetic studies in human breast milk. The concentration of propylthiouracil was linear over the 50 – 5000ng/ml range. The recovery and the coefficient of variation was 92.0 – 100.6% and 1.6 – 2.9%, respectivery. This assay has the advantages of specificity, simplicity and reproducibility for the measurement of propylthiouracil in human breast milk.     

Octadecylsilane/Nylon‐6 composite as a thin‐film microextraction sorbent for the determination of bisphenol A in water samples

We report on the fabrication of a thin‐film composite for the extraction of bisphenol A from aqueous solutions. Nylon‐6, C₁₈ particles, and polyethylene glycol were used to prepare the thin film sorbent. Bisphenol A was used as a model compound to evaluate the extraction efficiency of the sorbent. High‐performance liquid chromatography with UV detection was used for the analysis. The extraction yield of the sorbent was compared with other thin films fabricated using different sorbents including nanoclay, LiChrolut EN, and multiwalled carbon nanotubes. Experimental parameters affecting the extraction performance (extraction time, desorption condition, sample stirring, and ionic strength of the sample solution) were investigated. The detection limit and the dynamic range of the method were 0.05 and 0.15–50 μg/L, respectively. The relative standard deviation of the method at two concentration levels (0.5 and 20 μg/L) was less than 7.2%. Finally, a polycarbonate baby bottle, river water, and wastewater samples were analyzed by the method.     

Solid-Phase Extraction of Caffeine and Theophylline from Green Tea by a New Ionic Liquid-Modified Functional Polymer Sorbent

The new ionic liquid-modified polymer sorbent was developed by surface chemical modification of the synthesized polymer particles using ionic liquids. The obtained ionic liquid-modified polymer was successfully used as a special sorbent in a solid-phase extraction (SPE) process to isolate caffeine and theophylline from green tea. A comparison of different SPE cartridges using the blank polymer, C₁₈, and ionic liquid-modified polymer revealed that the highest recovery was obtained using ionic liquid-modified polymer sorbent. Quantitative analysis was carried out by using a C₁₈ column (5 µm, 150 × 4.6 mm) as an analytical column. Good linearity was obtained from 5 × 10^?4 to 0.5 mg/mL (r²>0.999) for the two analytes with relative standard deviations <4.5%.     

Purification of 4-hydroxybenzoic Acid and 4-hydroxybenzaldehyde from Laminaria japonica Aresch Using Commercial and Monolithic Sorbent in SPE Cartridge

Phenolic compounds are one of the major compounds in Laminaria japonica Aresch. Solid-phase extraction was used to separate the two phenolic compounds (4-hydroxybenzoic acid and 4-hydroxybenzaldehyde). A new monolithic sorbent was developed and used successfully as a special sorbent in a solid-phase extraction process. The effects on different SPE cartridges using silica, C₁₈, and monolithic were compared. Quantitative analysis was carried out using a C₁₈ analysis column (5 µm, 150 × 4.6 mm). Good linearity was obtained for the two targets, ranging from 0.5 to 100 µg mL^?1 (r ²  > 0.999), with relative standard deviations <4.7%.     

Rapid and quantitative extraction and analysis of trace organics using directly coupled SFE-GC

Supercritical fluid extraction can be coupled with capillary gas chromatography (SFE-GC) using commercially-available on-column or split/splitless injection ports. While liquid solvent extractions require several hours or even days to perform, SFC-GC analyses can be completed in ≤ 1 hour including extraction, analyte concentration, and GC separation. SFE-GC yields chromatographic peak shapes that compare favorably with those obtained using conventional liquid solvent injections. Quantitative extraction and recovery of analytes is usually achieved in 10 minutes, and maximum sensitivity is obtained since the extracted analytes can be quantitatively transferred into the GC column for cryogenic focusing prior to GC analysis. SFE-GC analysis of a variety of organic pollutants from environmental solids and sorbent resins, and flavor and fragrance compounds from food products will be discussed.     

High-Performance Liquid Chromatography-Tandem Mass Spectrometry for the Determination of Trospium Chloride in Human Plasma and Its Application in a Bioequivalence Study

A selective, rapid, and sensitive high performance liquid chromatography-tandem mass spectrometry (HPLC-ESI-MS/MS) method was developed and validated for the quantification of trospium chloride in human plasma. With tramadol chloride as the internal standard, sample pretreatment involved a simple liquid-liquid extraction with chloroform-isopropyl alcohol (40/2, v/v) of 0.5 ml plasma. The analysis was carried out on a Hypsil C₁₈ column (150 mm × 2.1 mm, 5.0 μm) with a flow rate of 0.2 ml/min. The mobile phase was methanol-5% acetic acid-20 mM ammonium methylate (55/30/15, v/v/v). The detection was performed by a selected reaction monitoring (SRM) mode via electrospray ionization (ESI). Linear calibration curves were obtained in the concentration range of 0.2–50.0 ng/ml, with a lower limit of quantification of 0.2 ng/ml. The intra- and inter-day precision (RSD) values were below 15%. The method was successfully applied to a clinical bioequivalence study of trospium chloride in Chinese healthy volunteers following oral administration.     

Packing for high-performance liquid chromatography based on microspheric particles of (urea-formaldehyde resin)-silica gel composite

Preparation of uniform microspheric particles of the (urea-formaldehyde resin)-silica gel composite was studied. The suitability of this composite modified with C₁₈ groups as packing for reversed-phase high-performance liquid chromatography was evaluated. The sorbent was modified using either octadecyldimethylchlorosilane or polymers containing C₁₈ groups, and the columns packed with the resulting sorbent were studied. The experimental results showed that the polymeric modification allows efficient shielding of the surface silanol groups.     

Application of Solid-Phase Extraction Coupled with Dispersive Liquid–Liquid Microextraction for the Determination of Benzaldehyde in Injectable Formulation Solutions

Solid-phase extraction followed by dispersive liquid–liquid microextraction (SPE-DLLME) technique has been developed as a new analytical approach for extracting, cleaning up and preconcentrating benzaldehyde, a toxic oxidation product of the widely used preservative and co-solvent benzyl alcohol, in injectable formulation solutions. SPE of benzaldehyde from samples was carried out using C₁₈ sorbent. After the elution of benzaldehyde from the sorbent by using acetonitrile, DLLME technique was performed on the obtained solution. Benzaldehyde was preconcentrated by using DLLME technique. Thus, 1.5 mL acetonitrile extract (disperser solvent) and 55.0 µL 1,2-dichloroethane (extraction solvent) were added to 5 mL ultra pure water and a DLLME technique was applied. Several variables that govern the proposed technique were studied and optimized. Under optimum conditions, the method detection limit (LOD) of benzaldehyde calculated as three times the signal-to-noise ratio (S/N) was 0.08 µg L^?1. The relative standard deviation (RSD) for four replicates was 5.8 %. The calibration graph was linear within the concentration range of 0.5–500 µg L^?1 for benzaldehyde. The proposed method has been successfully applied to the analysis of the benzaldehyde in injectable formulation solutions (diclofenac, vitamin B-complex and voltaren) and the relative recoveries were between 88 and 92 % and show that matrix has a negligible effect on the performance of the proposed method.     

Rapid Determination of Coumatetralyl in Human Serum by High‐Performance Liquid Chromatography Coupled with Electrospray Ionization Tandem Mass Spectrometry

Abstract

A rapid, sensitive, and selective high‐performance liquid chromatography‐tandem mass spectrometric method (HPLC‐MS‐MS) for the determination of coumatetralyl in human serum using warfarin as an internal standard has been developed and validated. Coumatetralyl and the internal standard were extracted from the human serum samples by liquid‐liquid extraction with ethyl acetate, followed by separation on a XDB C₁₈ reversed‐phase column (150 mm×2.1 mm i.d., 5 µm) using a mobile phase consisting of acetic acid‐ammonium acetate (5 mmol/L, pH=4.5)/methanol (20:80, v/v) at a constant flow rate of 0.40 mL/min. Coumatetralyl and the internal standard were ionized by negative ion pneumatically assisted electrospray and detected in the multiple‐reaction monitoring mode using precursor→product ion combinations at m/z 291→247 and 307→161, respectively. The calibration curve was linear (r²=0.9945) in the concentration range of 0.5～100.0 ng/mL, with a lower limit of quantification of 0.5 ng/mL in human serum. Intra‐ and inter‐day relative standard deviations were less than 6.3 and 11.0%, respectively. The mean extraction recovery was 87.9% for coumatetralyl and 90.1% for the internal standard. This method is found to be able to determine trace coumatetralyl in human serum and can be used for the diagnosis of poisoned human beings.     

High performance liquid chromatography determination of chlorophenols in water samples after preconcentration by continuous flow liquid membrane extraction on-line coupled with a precolumn

A continuous flow liquid membrane extraction (CFLME)-C₁₈ precolumn-liquid chromatography system was developed for preconcentration and determination of chlorinated phenols (CPs). After preconcentration by CFLME, which is based on the combination of continuous flow liquid-liquid extraction and supported liquid membrane, CPs were enriched in 960 μl of 0.5 mol l⁻¹ NaOH used as acceptor. This acceptor was on-line neutralized and transported onto the C₁₈ precolumn where analytes were absorbed and focused. Then the focused analytes were injected onto the C₁₈ analytical column for separation and detected at 215 nm with a diode array detector. CFLME related parameters such as flow rates, pH of donor and acceptor concentration were optimized. The proposed method presents detection limits of 0.02-0.09 μg l⁻¹ (S/N=3) when 100 ml samples were enriched. The proposed method was successfully applied to determine CPs in tap water and river water samples with spiked recoveries in the range of 70-121%.     

超高效液相色谱-同位素稀释高分辨质谱法测定红葡萄酒中的18种农药残留

建立了采用超高效液相色谱-同位素稀释高分辨质谱法同时快速测定红葡萄酒中18种农药残留的方法。样品采用乙腈提取,以N-丙基乙二胺（PSA）和C₁₈作为吸附剂的分散固相萃取法（d-SPE）进行净化,以BEH C₁₈色谱柱进行色谱分离,分别通过高分辨质谱的全扫描/实时二级质谱扫描（full scan/ddms²）和目标选择离子监测（targeted SIM,tSIM）模式进行定性筛查和定量检测。以多菌灵-D₄、毒死蜱-D₁₀、吡虫啉-D₄、甲氧虫酰肼-D₉、嘧霉胺-D₅和戊唑醇-D₆为内标进行内标法定量,有效地降低了样品基质的影响。待测物在0.5~50 μg/L范围内呈良好的线性关系,相关系数（r）大于0.999。18种农药残留的检出限（LOD）为0.5 μg/kg,定量限（LOQ）为1.0 μg/kg。空白红葡萄酒样品在1~40 μg/kg范围内的4个加标水平的平均回收率为85.4%~117.9%,相对标准偏差为0.5%~6.1%。应用该方法对市售的红葡萄酒样品进行检测,共检出多菌灵、吡虫啉、嘧霉胺、戊唑醇和三唑醇5种农药残留,含量分别为2.6~143.0 μg/kg、0.6~0.9 μg/kg、2.1~3.1 μg/kg、0.6~3.0 μg/kg和0.6 μg/kg。该方法适用于红葡萄酒中农药残留的快速筛查和定量检测。     

Spectrofluorimetric Determination of Aflatoxin B1 in Winter Herbal Teas via Magnetic Solid Phase Extraction Method by using Metal–Organic Framework (MOF) Hybrid Structures Anchored with Magnetic Nanoparticles

MIL53(Al)-SiO₂@Fe₃O₄ composite was prepared by co-precipitation route with a typical Stöber synthetic process and ultrasonic-agitation, then subsequently utilized as a multi-component novel sorbent in solid-phase microextraction (SPME) of aflatoxin B1 in winter herbal teas. Microstructural properties of MIL53(Al)-SiO₂@Fe₃O₄ composite was characterized by using Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) methods, and Brunauer–Emmett–Teller (BET) surface area measurement. The MIL53(Al)-SiO₂@Fe₃O₄ composite was found to be a very effective sorbent in spectrofluorimetric determination of aflatoxin B1 (AFB1) in winter herbal teas via magnetic solid-phase extraction (SPE) route. The proposed method showed a wide linear range from 0.5 to 150 ng/ml, low limit of detection (LOD = 0.5 ng/ml), and an acceptable recovery values (70.7–96.5%) in real samples analysis. This study shows that the suggested method possesses an important potential to use for detecting AFB1 in quality control laboratories.     

Ultra-high-pressure liquid chromatography–tandem mass spectrometry for the analysis of six resorcylic acid lactones in bovine milk

This work reports a rapid, reliable and sensitive multi-residue method for the simultaneous determination of six resorcylic acid lactones in bovine milk by ultra-high-pressure liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS). The resorcylic acid lactones were extracted, purified, and concentrated from milk samples in one step using a solid-phase extraction (SPE) cartridge that contained a polymeric mixed-mode anion-exchange sorbent. The analysis was performed on a Waters Acquity BEH C₁₈ column utilizing a gradient elution profile. Each LC run was completed in 3.5 min. The analytes were detected by multiple reaction monitoring (MRM) using electrospray ionization (ESI) negative mode. Mean recoveries from fortified samples ranged from 92.6% to 112.5%, with relative standard deviations lower than 11.4%. Using 5 mL bovine milk, the limits of detection and quantification for resorcylic acid lactones were in the ranges of 0.01–0.05 and 0.05–0.2 μg/L, respectively. The application of this newly developed method was demonstrated by analyzing bovine milk samples from markets.     

Quick and Simple Determination of Dihydroergotamine by High-Performance Liquid Chromatography

Abstract

A simple and rapid liquid chromatographic assay method using a fluorescence detector for quantitation of dihydroergotamine in plasma without extraction was developed. After precipitating the protein with acetonitrile, the supernatant liquid was directly injected for analysis. Chromatographic separation was achieved on C₁₈ reversed phase column and the mobile phase was the isocratic mixture of methanol, acetonitrile and glycine buffer (0.5:3.5:6.0). With this eluting solvent the drug and its internal standard were well separated from the interference of the plasma sample. The average recovery of dihydroergotamine from 6 replicate samples of different concentrations (5-30 ng/ml) were 92.2 ± 3.37%. The minimum amount of dihydroergotamine detectable by this method was 2 ng/ml of sample.