Selective Solid-phase Extraction Method Research Articles

Preparation, evaluation, and application of dummy molecularly imprinted polymer for analysis of hesperidin in lime juice.

Lime juice as the most commonly used natural source production can be characterized using determination of flavonoids contents such as hesperidin. So, development of analyzing methods for checking the quality and healthiness of lime juices is necessary. In this study, we aimed to set up a selective solid phase extraction method using dummy molecularly imprinting approach for extraction and separation of hesperidin in lime juice to check the quality of commercial lime juice products of Mashhad city market. The imprinted polymers were synthesized by hesperitin as dummy template due to the hesperitin solubility in the wide range of porogenic solvents. The specificity extent of synthesized polymers toward hesperidin was tested and optimum one was used as adsorbent in solid-phase extraction cartridge. The dummy molecularly imprinted polymer with high adsorption capacity for hesperidin (dissociation constant 0.12 μM) was successfully used for extraction and clean-up of hesperidin in the lime juice matrix prior to analysis by high-performance liquid chromatography. The analysis of hesperidin was done in the range of 0.312-50μg/mL with detection limit of 0.05μg/mL. This technique was successfully set up to remove the interfering compounds for analysis of hesperidin in commercial lime juice products.

Separation and Preconcentration of Cobalt(II) from Water Samples with Amberlite CG-120 Resin

A selective solid-phase extraction method has been developed for the preconcentration and separation of trace amounts of Co(II). The method was based on the adsorption of Co(II) ions on the Amberlite CG-120 resin. The adsorbed Co(II) ions on the resin were eluted by 4 mol/L HCI and then they were determined by Flame Atomic Absorption Spectrometry (FAAS). Various experimental conditions, such as pH, type and concentration of eluent, the flow rate of sample and eluent solution, amount of resin, and sample volume were investigated to obtain better sensitivity and effective separation of trace levels of the Co(II) ions. Moreover, the interference effects of some ions on the recovery of Co(II) were also investigated. The developed method was applied for the determination of Co(II) ions in drinking and wastewater samples. The enhancement factor (EF) and limit of detection (LOD) values were found to be 25-fold and 9.32 µg/L, respectively. The accuracy of the method was tested by the certified reference material of TMDA-70.2 Lake Ontario Water and there was a good agreement between found and certified values at a 95% confidence level.

Enhanced dispersive solid phase extraction assisted by cloud point strategy prior to fluorometric determination of anti-hepatitis C drug velpatasvir in pharmaceutical tablets and body fluids.

An innovative spectrofluorometric method was developed for the analysis of a recently FDA approved anti-hepatitis C velpatasvir (VELP). The developed method was relied on dispersive solid phase extraction (dSPE) using synergistic effect of reduced graphene oxide (RGO) and cobalt hydroxide nanoparticles (CHNPs) in addition to cloud point extraction (CPE) using polyethylene glycol 6000 (PEG 6000) as non-ionic surfactant. This method combines the merits of preconcentration and interferences elimination achieved by dSPE and CPE, respectively. All relevant parameters such as surfactant concentration, ionic strength, pH, incubation time and others were thoroughly investigated and optimized. Fluorometric detection of VELP was carried out at excitation wavelength of 350 nm and emission wavelength of 415 nm. Under the optimum conditions, a linear calibration curve was achieved in the range of 0.5–45 ng mL−1. Limits of detection (LOD) and quantification (LOQ) based on three and ten times the standard deviation of the blank were 0.040 and 0.112 ng mL−1, respectively. This method was successfully applied for determination of VELP in real samples such as tablets, human plasma and urine samples with good recoveries.

Solid-phase extraction of plant thionins employing aluminum silicate based extraction columns.

Thionins belong to a family of cysteine-rich, low-molecular-weight (∼5 KDa) biologically active proteins in the plant kingdom. They display a broad cellular toxicity against a wide range of organisms and eukaryotic cell lines. Thionins protect plants against different pathogens, including bacteria and fungi. A highly selective solid-phase extraction method for plant thionins is reported deploying aluminum silicate (3:2 mullite) powder as a sorbent in extraction columns. Mullite was shown to considerably improve selectivity compared to a previously described zirconium silicate embedded poly(styrene-co-divinylbenzene) monolithic polymer. Due to the presence of aluminum(III), mullite offers electrostatic interactions for the selective isolation of cysteine-rich proteins. In comparison to zirconium(IV) silicate, aluminum(III) silicate showed reduced interactions towards proteins which resulted into superior washings of unspecific compounds while still retaining cysteine-rich thionins. In the presented study, European mistletoe, wheat and barley samples were subjected to solid-phase extraction analysis for isolation of viscotoxins, purothionins and hordothionins, respectively. Matrix-assisted laser desorption/ionization time of flight mass spectroscopy was used for determining the selectivity of the sorbent toward thionins. The selectively retained thionins were quantified by colorimetric detection using the bicinchoninic acid assay. For peptide mass-fingerprint analysis tryptic digests of eluates were examined.

Synthesis, characterization and analytical application of Zn(II)-imprinted polymer as an efficient solid-phase extraction technique for trace determination of zinc ions in food samples

Zinc imprinted polymer (Zn(II)-IIP) as a solid-phase extraction technique was applied for preconcentration and determination of zinc in environmental and food samples by FAAS. Zn(II)-IIP was synthesized by copolymerization of 2-vinylpyridine as the functional monomer, ethylene glycol dimethacrylate (EGDMA) as the cross-linker, 2,2-azobisisobutyronitrile as the initiator, Zn(NO3)2 as the template ion, diphenylcarbazone as the ligand, and methanol/dichloromethane (50:50) as the solvent. The synthesized polymer particles were characterized by thermogravimetry analysis (TGA), differential thermal analysis (DTA), scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FT-IR), and X-ray diffraction (XRD). The optimization process was carried out using the central composite design (CCD). With this design, the optimum conditions for the adsorption step were 6.6, 30mg, and 23min, for pH, mass of polymer and adsorption time respectively, and for desorption step the optimal conditions were 14mL, 12% (v/v), and 23min, for volume of eluent, concentration of eluent, and desorption time, respectively. Under the optimized conditions, the detection limit of the proposed method was found to be 0.15μgL−1, while the relative standard deviation (RSD) for 10 replicate measurements was calculated to be 2.8%. Therefore the introduced selective solid phase extraction method can be used as a reliable technique for selective and sensitive trace detection of zinc in different food matrixes, and the reliability of the proposed solid phase extraction technique was established by the analysis of standard reference materials.

Ultratrace determination of arsenic in water samples by electrothermal atomic absorption spectrometry after pre-concentration with Mg–Al–Fe ternary layered double hydroxide nano-sorbent

A selective solid phase extraction method, based on nano-structured Mg–Al–Fe(NO3−) ternary layered double hydroxide as a sorbent, is developed for the pre-concentration of ultra-trace levels of arsenic (As) prior to determination by electrothermal atomic absorption spectrometry. It is found that both As(III) and As(V) could be quantitatively retained on the sorbent within a wide pH range of 4–12. Accordingly, the presented method is applied to determination of total inorganic As in aqueous solutions. Maximum analytical signal of As is achieved when the pyrolysis and atomization temperatures are close to 900°C and 2300°C, respectively. Several variables affecting the extraction efficiency including pH, sample flow rate, amount of nano-sorbent, elution conditions and sample volume are optimized. Under the optimized conditions, the limit of detection (3Sb/m) and the relative standard deviation are 4.6pgmL−1 and 3.9%, respectively. The calibration graph is linear in the range of 15.0–650pgmL−1 with a correlation coefficient of 0.9979, sorption capacity and pre-concentration factor are 8.68mgg−1 and 300, respectively. The developed method is validated by the analysis of a standard reference material (SRM 1643e) and is successfully applied to the determination of ultra-trace amounts of As in different water samples.

Solid-phase extraction of galloyl- and caffeoylquinic acids from natural sources (Galphimia glauca and Arnicae flos) using pure zirconium silicate and bismuth citrate powders as sorbents inside micro spin columns

Galloyl- and caffeoylquinic acids are among the most important pharmacological active groups of natural compounds. This study describes a pre-step in isolation of some selected representatives of these groups from biological samples. A selective solid-phase extraction (SPE) method for these compounds may help assign classes and isomer designations within complex mixtures. Pure zirconium silicate and bismuth citrate powders (325 mesh) were employed as two new sorbents for optimized SPE of phenolic acids. These sorbents possess electrostatic interaction sites which accounts for additional interactions for carbon acid moieties as compared to hydrophilic and hydrophobic sorbents alone. Based on this principle, a selective SPE method for 1,3,4,5-tetragalloylquinic acid (an anti-HIV and anti-asthamatic agent) as a starting compound was developed and then deployed upon other phenolic acids with success. The recoveries and selectivities of both sorbents were compared to most commonly applied and commercially available sorbents by using high performance liquid chromatography. The nature of interaction between the carrier sorbent and the acidic target molecules was investigated by studying hydrophilic (silica), hydrophobic (C18), mixed-mode (ionic and hydrophobic: Oasis® MAX) and predominantly electrostatic (zirconium silicate) materials. The newly developed zirconium silicate and bismuth citrate stationary phases revealed promising results for the selective extraction of galloyl- and caffeoylquinic acids from natural sources. It was observed that zirconium silicate exhibited maximum recovery and selectivity for tetragalloylquinic acid (84%), chlorogenic acid (82%) and dicaffeoylquinic acid (94%) among all the tested sorbents.

Development of a selective solid phase extraction method for nitro musk compounds in environmental waters using a molecularly imprinted sorbent

A powerful analytical method for the determination of the family of the nitro musk compounds at trace level in environmental waters—river, sea, and water from a treatment plant—is presented. The method is based on the use of molecularly imprinted silica (MIS) as sorbent for solid phase extraction (SPE) used for the clean-up and the concentration step of the target analytes previous to their determination by gas chromatography–mass spectrometry. The optimized extraction procedure allowed extraction recoveries between 61% and 87% using the MIS. The comparison with a non-imprinted silica (NIS) sorbent, for which extraction recoveries between 8% and 26% were obtained, showed the high selectivity of the MIS for the nitro musks. Moreover, high enrichment factors, ranging between 580 and 827, were achieved. The imprinted sorbent was compared to a conventional polymeric SPE sorbent for the extraction of the target compounds from environmental waters, showing high selectivity of the MIS and its clean-up potential. For the first time, the five nitro musk compounds were selectively extracted with an imprinted material.

Determination of Aqueous Fluoride by Continuous Powder Introduction Microwave-Induced Plasma Optical Emission Spectrometry after Preconcentration on Various Sorbents

ABSTRACT A spectrometric determination of aqueous fluoride has been improved by coupling of continuous powder introduction microwave-induced plasma optical emission spectrometry with separation of the analyte onto powdered sorbents. A selective solid phase extraction method for preconcentrating trace fluoride from aqueous environmental samples on calcium hydrogenphosphate dihydrate in batch operation was employed while, for flow operation, the zirconium modified activated carbon method was adopted. The fluoride could be readily excited in helium plasma at 685.6 nm. Using a 1-L sample volume and a preconcentration factor of 1000, practical detection limit with respect to water sample is in the range 4.0–4.7 ng mL−1, depending on the sorbent used. External calibration was done using standards obtained by the dropping of standard fluoride solution on the powdered sorbent covering fluoride content from 50 to 5000 µg g−1. The procedure was applied to the determination of fluoride in mineral waters and certified reference material (CRM) drinking water.

Control of matrix effects in the analysis of urinary F2-isoprostanes using novel multidimensional solid-phase extraction and LC-MS/MS

F(2)-isoprostanes (F(2)-iPs), established markers of oxidative stress, exist as four sets of regioisomers. Simultaneous and specific determination of F(2)-iPs can be achieved by liquid chromatography-tandem mass spectrometry (LC-MS/MS). We developed novel methods for urine sample preparation and HPLC to control matrix-related ion suppression effects in the LC-MS/MS analysis of F(2)-iPs. A selective solid-phase extraction (SPE) wash protocol was developed with an Oasis HLB (hydrophilic-lipophilic balance) SPE cartridge using an elution profile of [(3)H]8-iso-prostaglandin (PG)F(2alpha) (iPF(2alpha)-III) when the methanol concentration was increased under acidic, neutral, and base wash conditions. A multidimensional (MD)-SPE method that incorporated size exclusion chromatography [corrected] reverse-phase chromatography, and normal-phase chromatography was developed using an Oasis HLB SPE cartridge and an HLB microElution SPE plate. Average extraction recoveries of the deuterated internal standards of iPF(2alpha)-III and iPF(2alpha)-VI were 62 +/- 8% and 60 +/- 10%. A buffer-free HPLC method for the separation of F(2)-iP isomers was developed on base-deactivated C8 columns. Average matrix effects for iPF(2alpha)-III and iPF(2alpha)-VI were 95 +/- 6% and 103 +/- 5%. The clean extraction of urine F(2)-iPs using MD-SPE and the separation of F(2)-iP isomers using a novel HPLC method did not cause apparent ion suppression in the analysis of iPF(2alpha)-III and iPF(2alpha)-VI using LC-MS/MS. These findings should be useful for establishing a routine LC-MS/MS method for the analysis of F(2)-iPs.