Pipette-tip Solid-phase Extraction Research Articles

Efficient enrichment and analysis of atrazine and its degradation products in Chinese Yam using accelerated solvent extraction and pipette tip solid-phase extraction followed by UPLC–DAD

The Chinese Yam (Dioscorea opposita) is cultivated widely in China. However, there are potential safety risks associated with herbicide residues in Chinese Yam because of its characteristics and unregulated use of pesticides. We developed an efficient sample preparation technique for simultaneous analysis of atrazine and its degradation products in Chinese Yam using accelerated solvent extraction and pipette tip solid-phase extraction followed by UPLC-DAD analysis. Molecularly imprinted polymer (MIP) were used as the adsorbent material. Method performance was evaluated and our results showed the limit of quantification was 1–3 μg/ kg, with recoveries in the range 79.2–103.8%. When compared with other methods, this method provided superior performance in terms of sensitivity, accuracy, and precision. This method is, therefore, expected to be useful in supervised residue analysis.

Core-satellite surface imprinting polymer-based pipette tip solid-phase extraction for the colorimetric determination of pyrethroid metabolite.

A core-satellite-structured surface molecularly imprinted polymer has been synthesized for the enrichment of 3-phenoxybenzaldehyde by pipette tip solid-phase extraction (SPE). In a typical sol-gel process, two silane reagents as functional monomers and 3-phenoxybenzoic acid as the dummy template, the surface imprinting layer was coated on the core-satellite silica microsphere, which formed thecore-satellite-structured molecularly imprinted polymer (CSMIP). Compared tothe silica-based core-shell ones, this CS-MIP exhibits astunning surface area (142m2g-1) in micrometer size and also overcomes the aggregation trends of core-shell structure in nanoscale. Taking potassium permanganate solution as oxidizer and indicator, the adsorbed 3-phenoxybenzaldehyde can be a quantitatively determined through redox reaction after elution. The value of maximum adsorption capacity and imprinting factor of CS-MIP were calculated to be 87.5μgmg-1 and 2.13, respectively. These CS-MIPs were packed into commercial pipette tip as the sorbent to concentrate 3-phenoxybenzaldehyde. Under the optimum condition, a liner relationship was achieved in the range 0.200 to 1.00μgmL-1 and the limit of detection was 81ngmL-1. Moreover, this customized SPE device exhibits good adsorption capability after six sequential adsorption-desorption cycles, and the high recovery range of 92.2~99.7% ofspiked tap water assay demonstrated its potential application forreal sampleanalysis. Graphical abstract Schematic presentation of core-satellite molecularly imprinted polymer preparation strategy and customized pipette tip solid-phase extraction device.

Deep eutectic solvent functionalized graphene oxide composite adsorbent for miniaturized pipette-tip solid-phase extraction of toluene and xylene exposure biomarkers in urine prior to their determination with HPLC-UV.

A deep eutectic solvent functionalized graphene oxide composite adsorbent (DFG) was synthesized through reversible-addition fragmentation chain-transfer polymerization. The synthesized DFG had multiple adsorption interactions after covalent modification with a deep eutectic solvent (allyltriethylammonium bromide/ethylene glycol). Adsorption isotherms and kinetics studies of DFG indicate that the adsorption of hippuric acid (HA) and methylhippuric acid (MHA) was monolayer chemical adsorption. The comparison of DFG with commercial adsorbents demonstrates that the adsorption ability of DFG was superior. This was due to the multiple adsorption interactions of DFG for the three analytes (mainly π-interaction, hydrogen bonding, electrostatic adsorption, and hydrophobic interaction). The DFG adsorbent was applied to miniaturized pipette-tip solid-phase extraction (MPT-SPE), followed by high-performance liquid chromatography (HPLC) to determine biomarkers in urine for toluene and xylene exposure. The DFG-MPT-SPE-HPLC method required only 2.00mg of DFG as adsorbent, 0.50mL of washing solvent, and 0.40mL of elution solvent to achieve a wide linear range (0.200-200μgmL-1), high recoveries (90.9-99.1%), and high precision (RSD ≤ 6.3%). The proposed method was applied to determine HA and MHA in urine samples from occupational workers. Graphical abstract Deep eutectic solvent functionalized graphene oxide composite adsorbent for miniaturized pipette-tip solid-phase extraction of toluene and xylene exposure biomarkers in urine prior to their determination with HPLC-UV.

Zr-MOF modified cotton fiber for pipette tip solid-phase extraction of four phenoxy herbicides in complex samples

Phenoxy herbicides are widely applied in agricultural weeding. The determination of herbicides is important in environmental protection, agricultural production, food safety, and public health. In this study, a facile and efficient analytical method was proposed for the trace detection of phenoxy herbicides in soil, cucumber, and tap water samples by coupling pipette tip solid phase extraction (PT-SPE) with high performance liquid chromatography. UiO-66-funtionalized cotton (Cotton@UiO-66) was packed into pipette-tip as sorbent to fabricate extraction device. The modification of UiO-66 on cotton fiber was confirmed using scanning electron microscope, Fourier transform infrared spectroscopy, and X-ray diffraction. The main factors affecting the adsorption of Cotton@UiO-66 for four phenoxy herbicides were evaluated by response surface methodology in detail. Under optimized conditions, Cotton@UiO-66 displayed excellent properties in the extraction of phenoxy herbicides with good peak shape. Linear ranges of 4-chlorophenoxyacetic acid, dicamba, 2,4-dichlorophenoxyacetic acid, and 2-(2,4-dichlorophenoxy) propionic acid were 1.4-72μg/L, 5.6-280μg/L, 2.8-140μg/L and 3.2-160μg/L (RSDs<6.3%), respectively. The recoveries were between 83.3 and 106.8% with RSDs <6.7%, with detection limits ranging from 0.1μg/L to 0.3μg/L. The results show that Cotton@UiO-66 in PT-SPE is an effective method for monitoring phenoxy herbicides in complex samples.

1,3,5-Triethynylbenzene and melamine as monomers to synthesize three-dimensional network porous aromatic frameworks based silica/florisil for determination of carbendazim and thiabendazole in spinach.

In this study, the new and efficient three-dimensional network porous aromatic frameworks materials called Silica-PAFs-a, Florisil-PAFs-a, Silica-PAFs-b, and Florisil-PAFs-b were first synthesized. The properties of materials were analyzed by five characterization methods. The materials were used as adsorbents in pipette-tip solid-phase extraction for the effective determination of carbendazim and thiabendazole in spinach sample. Meanwhile, the obtained materials were tested by static adsorption and dynamic adsorption. The result showed that the specific surface area of materials greatly increased after introducing three-dimensional network porous aromatic frameworks. Microstructural modification exposed a large number of amino reactive groups that made them have a better adsorption amount for the two targets. The calibration graphs of carbendazim and thiabendazole in methanol were linear over 0.10-300.0µg/mL, and the limits of detection and quantification were 0.00546 and 0.0182µg/mL, and 0.00741 and 0.0247µg/mL respectively. A reliable analytical method was developed for recognition targets in spinach sample by Silica-PAFs-b with satisfactory extraction recoveries (96.25 and 100.51%). The proposed method using the material was applied for trace analysis of the carbendazim and thiabendazole residue.

Rapid Analysis of Four Amphetamines in Urine by Self-Made Pipette-Tip Solid-Phase Extraction Followed by GC-MS/MS.

A simple and rapid pipette-tip solid-phase extraction (PT-SPE) procedure with derivatization prior to gas chromatography triple quadrupole mass spectrometry analysis is developed for the simultaneous determination of amphetamine (AMP), methamphetamine (MA), 3,4-methylenedioxyamphetamine (MDA) and 3,4-methylenedioxymethamphetamine (MDMA) in urine samples. The PT-SPE procedure using self-made sorbent could extract drugs within 6min from 100-μL urine samples, requiring low solvent-consumption (<2.0mL). Besides, the self-made pipette tip could be reused at least five times. Under optimized conditions, the recoveries of four amphetamines at spiked levels (low, medium and high) ranged from 87.7 to 110.4%, with relative standard deviations<9.5%. The limit of detections and limit of quantifications for AMP, MA, MDA and MDMA were in the range of 2.52-8.25ng⋅mL-1 and 8.4-27.5ng⋅mL-1, respectively. Validation results show that the proposed method is suitable for the quantitation of amphetamines and has been successfully applied in the urine samples of suspected drug abusers.

One pot green synthesis of m-aminophenol–urea–glyoxal resin as pipette tip solid-phase extraction adsorbent for simultaneous determination of four plant hormones in watermelon juice

Plant hormones (PHs) are a type of pesticide that can potentially affect human health. Therefore, their quantitative detection is particularly important. In this study, a green and economic method for the simultaneous extraction and determination of four PHs, namely thidiazuron, forchlorfenuron, 1-naphthylacetic acid, and 2-naphthoxyacetic acid, in watermelon juice was developed by using m-aminophenol–urea–glyoxal resin as the adsorbent for pipette tip solid phase extraction (PT-SPE) coupled with liquid chromatography. The resin was synthesized via a simple (one pot hydrothermal synthesis) and green (ethanol as the solvent and glyoxal as crosslinking agent) process. The synthesized resin possesses multiple functional groups (hydroxyl, amino, and imino, among others), high adsorption capacity, larger specific surface area than the urea–glyoxal resin and m-aminophenol–glyoxal resin, and can be regenerated easily. The PT-SPE device is simple, cheap, and easy to obtain, and the adsorbent dosage is only 5.0 mg. The proposed method has a wide linear detection range, high recovery, good precision, and high sensitivity, and satisfies the measurement requirements for detecting trace levels of PHs in fruits and vegetables.

Electrospinning fabrication of covalent organic framework composite nanofibers for pipette tip solid phase extraction of tetracycline antibiotics in grass carp and duck

In the current study, a novel covalent organic frameworks COF-SCU1 incorporated electrospun nanofibers (PAN@COF-SCU1 nanofibers) was fabricated via a facile electrospinning method and utilized as adsorbent in pipette tip solid-phase extraction (PT-SPE) of tetracycline antibiotics (TCs) from foods. The prepared PAN@COF-SCU1 nanofibers possessed both of the unique characteristics of electrospun nanofibers and COFS-CU1, and thus improving the adsorption capacity of the electrospun nanofibers and preventing the problems of leakage and high pressure caused by directly using the nanosize COFs as adsorbent in PT-SPE. The experiments affected the adsorption and desorption efficiencies, such as the loading ratios of COFS-CU1 in nanofibers, the amount of nanofibers, the matrix pH and desorption solvent, were studied in detail. Eventually, a new pipette tip solid-phase extraction-high performance liquid chromatography (PT-SPE/HPLC) method was proposed for the analysis of three TCs from food. Satisfied linearity for TCs was obtained in the range of 4–70 ng mL−1. The limits of detection and quantification were ranged from 0.6 to 3 ng mL−1 and from 2 to 10 ng mL−1, respectively. The interday and intraday precisions (RSD) were all lower than 9%. The proposed PT-SPE/HPLC method was used to determine TCs residues in grass carp and duck samples for the first time. The results could not only explore the availability of PT-SPE in the extraction of TCs in food samples, but also broadened the potential applications of COFs in sample preparation.

Molybdenum disulfide-hypercrosslinked polymer composite as an adsorbent for determination of polycyclic aromatic hydrocarbons in environmental water coupled with HPLC-FLD.

A composite was synthesized from two-dimensional molybdenum disulfide (MoS2) nanosheets and hypercrosslinked polymers (HCP), and the composite was characterized by infrared spectroscopy, scanning electron microscopy, and specific surface area. The fluffy and porous structure and multiple adsorption sites (π-interaction, static electricity, hydrogen bonding) make it ideal for use as an adsorbent. A pipette tip solid-phase extraction with the composite as the adsorbent combined with HPLC-FLD was developed to determine trace amounts of polycyclic aromatic hydrocarbons (phenanthrene, anthracene, fluoranthene, pyrene, benzo(α)anthracene) in environmental water. Under optimal extraction conditions, the method has a wide linear range (0.5-100ngmL-1) and low limit of detection (0.024-0.099ngmL-1), and the recoveries of PAHs from spiked environmental water were 73.8% to 123.6% (relative standard deviation ≤ 6.7%, n= 3). Graphical abstract Schematic representation of a three-dimensional molybdenum disulfide-ethylenediamine-hypercrosslinked polymer composite (MoS2-EDA-HCP) using pipette tip solid-phase extraction adsorbent for extracting trace levels of polycyclic aromatic hydrocarbons (PAHs) prior to HPLC-FLD. HCP, hypercrosslinked polymer; MoS2, molybdenum disulfide; EDA, ethylenediamine.

Polyacrylonitrile/MIL-53(Fe) electrospun nanofiber for pipette-tip micro solid phase extraction of nitrazepam and oxazepam followed by HPLC analysis.

Nanofibers were prepared from a nanocomposite consisting of polyacrylonitrile and a metal-organic framework of type MIL-53(Fe) by electrospinning. They are shown to be a viable sorbent for pipette-tip solid-phase extraction for the extraction of the benzodiazepine drugs nitrazepam and oxazepam. The nanofibers were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy and X-ray diffraction. The effects of sample pH value and volume, composition, and amount of electrospun nanofibers, the number of adsorption cycles and the type and volume of the eluent were optimized. Following extraction the drugs were quantified by HPLC. Under the optimized conditions, response is linear for both drugs in the 5.0-1000ngmL-1 concentration range. The limits of detection for oxazepam and nitrazepam are 1.5 and 2.5ngmL-1, respectively, and the relative standard deviations at the levels of 50, 100 and 250ngmL-1 (for n = 3) are ≤7.6%. The method was successfully applied for determination of drugs in spiked wastewater and biological fluids. Graphical abstractSchematic representation of polyacrylonitrile/MIL-53(Fe) composite nanofiber synthesis by electrospinning, and theuse of them as the sorbent in pipette-tip microsolid-phase extraction (PT-μSPE) for the preconcentration of Nitrazepam and Oxazepam before HPLC-DAD analysis.

Selective extraction and detection of β-agonists in swine urine for monitoring illegal use in livestock breeding

The illegal use of β-agonists often endangers animal-derived food safety. In this study, a selective detection method for β-agonists in swine urine was established via the combination of polymeric ionic liquid-molecularly imprinted graphene oxide-miniaturized pipette tip solid-phase extraction and high-performance liquid chromatography. It is worth noting that this method relied mainly on the designed adsorbent, which presented a rich adsorption mechanism, fast mass transfer rate, and high selectivity, and was successfully utilized in the selective extraction of β-agonists from swine urine samples. The proposed method has low LOD (0.20–0.56 ng/mL), high recovery (94.9–107.9%), and high reusability (4 times, 91.9–108.8%), which indicates its high potential as a selective, sensitive, accurate, and nonfatal method for monitoring the illegal use of β-agonists in the livestock breeding stage.

A molecularly imprinted polymer based monolith pipette tip for solid-phase extraction of 2,4-dichlorophenoxyacetic acid in an aqueous sample.

This paper presents a simple approach for fabrication of a pipette tip solid-phase extraction (PT-SPE) device, which possesses a monolith structure with low back pressure and has high selectivity to 2,4-dichlorophenoxyacetic acid (2,4-D). Pipette tips were packed with molecularly imprinted polymers (MIPs) as a selective adsorbent and high-density polyethylene (HDPE) as a co-sintering agent, and then heated to form a monolith extraction device. The key factors including the particle size and amount of packing material, and the type and volume of elution solvent, which influence PT-SPE device performance were optimized. A packing material of 40 mg/0.20 mL in a ratio of 4/6 (MIPs/HDPE) and treatment temperature of 150 °C was selected. By the determination with high-performance liquid chromatography (HPLC-SPD), the extraction device was found to have a good extraction recovery for a 2,4-D lake water sample at a low concentration (0.006 mg L-1) with an enrichment factor about 50. The proposed method provided a simple approach for the fabrication of a PT-SPE monolith device with reduced back pressure and wall effect, which are very important for improving the extraction efficiency. And the device will have promising application in the extraction of a variety of analytes in complex samples.

Peristaltic pump-assisted zirconium nanoparticle-based pipette-tip solid phase extraction for the determination of cobalt by slotted quartz tube-flame atomic absorption spectrophotometry

In this work, a novel, efficient, simple and green solid phase extraction method based on a pipette tip filled with zirconium nanoparticles was developed for the sensitive determination of cobalt in soil samples via slotted quartz tube-flame atomic absorption spectrophotometry.

Pipette-tip solid-phase extraction using cetyltrimethylammonium bromide enhanced molybdenum disulfide nanosheets as an efficient adsorbent for the extraction of sulfonamides in environmental water samples.

Surfactant cetyltrimethylammonium bromide enhanced molybdenum disulfide was used as an adsorbent in pipette-tip solid-phase extraction for the pretreatment of sulfonamides in environmental water samples. The factors affecting the extraction recoveries of the analytes, including the sample pH value, amount of sorbent, type and volume of eluent solution, and salt concentration were optimized. This pipette-tip solid-phase extraction method demonstrated good linearity (0.05-10.0 µg/L) with a coefficient of determination of 0.9984-0.9996, limit of detection (0.2-0.4 ng/L) and limit of quantitation (0.5-1.0 ng/L), good analyte recoveries (76-91), and acceptable limit of quantitation (<10%) under the optimized conditions. These results indicated that the proposed method was a good tool for monitoring sulfonamides in environmental water samples.

Absorption and utilisation of epimedin C and icariin from Epimedii herba, and the regulatory mechanism via the BMP2/ Runx2 signalling pathway

Bone nonunion remains a challenge during the treatment of bone defect accompanied with infection. Epimedii herba is a widely used medicine in clinic to enhance bone healing. Epimedin C and icariin are the major flavonoid glycosides from Epimedii herba. Although the effects of these compounds have been reported, their different absorption and utilisation by osteoblasts remain unclear. In the present study, lipopolysaccharide (LPS)-induced osteoblast was adopted as the model cell to evaluate the effects of epimedin C and icariin. The intracellular and extracellular drug concentrations within 24 h were assayed by pipette tip solid-phase extraction and high-performance liquid chromatography, respectively. MTT, alkaline phosphatase (ALP) and calcified nodule staining were performed to identify and evaluate the effects of epimedin C and icariin on LPS-induced osteoblasts. The regulatory roles of epimedin C and icariin in the bone morphogenetic protein-2 (BMP-2)/Runt-related transcription factor 2 (Runx2) signalling pathway were investigated. The results revealed that epimedin C and icariin were not efficiently absorbed by LPS-induced osteoblasts. Nevertheless, they still had high utilisation efficiency after entering the cells. ALP activity, mineralisation and osteoblasts proliferation were enhanced by a high concentration of epimedin C and icariin. The suppressed expression of BMP-2 and Runx2 in LPS-induced osteoblasts was up-regulated significantly after treatment with epimedin C and icariin. These findings firstly illustrated the behavior of epimedin C and icariin from Epimedii herba on LPS-induced osteoblasts and the regulatory property on the expression of key genes and proteins of the BMP-2/Runx2 signalling pathway, which might be helpful for better understanding flavonoids’ mechanism to enhance bone repair and improving their future application.

Synthesis of chitosan based molecularly imprinted polymer for pipette-tip solid phase extraction of Rhodamine B from chili powder samples

The purpose work is devoted to design of a simple, one-pot and green approach for the synthesis of molecularly imprinted polymer to construct a selective sorbent for pipette-tip solid phase extraction of Rhodamine B from chili powder samples and its subsequence separation and quantification by high performance liquid chromatography-ultraviolet/visible detection. The prepared molecularly imprinted polymer was synthesized using chitosan as versatile natural multi-functional bio-monomer and Rhodamine B as template in aqueous media. The effects of influential parameters (sorbent dosage, flow rate and eluent solvent volume) and their influences on Rhodamine B extraction recovery were examined and optimized by central composite design based response surface methodology as a powerful multivariate optimization tool. Under the optimized conditions, the linear range and limit of detection and quantification of proposed method were achieved to be 0.005–15 mg kg−1, 0.0015 mg kg−1 and 0.00488 mg kg−1, respectively, with satisfactory recoveries (>85.0%) and excellent repeatability (relative standard deviation < 6.1%). The easy synthesis conditions as well as satisfactory figures of merit are good indication of applicability of suggested method for extraction and determination of Rhodamine B from chili powder samples in terms of simplicity, cost effectiveness, selectivity and accurate analysis.

Optimization of heteroatom doped graphene oxide by deep eutectic solvents and the application for pipette-tip solid-phase extraction of flavonoids.

In order to improve the permeation and adsorption properties of graphene oxide, heteroatoms and deep eutectic solvent were introduced in this study. After being modified, the structural properties of graphene oxide were improved and the materials were applied to the determination of myricetin and rutin in tea sample by pipette-tip solid-phase extraction method. The materials were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-Ray diffractomer, energy dispersive spectroscopy, atomic force microscope, and specific surface area by Brunauer-Emmett-Teller N2 adsorption desorption analysis. Meanwhile, they were tested by static and dynamic adsorption. The result showed that the materials after modifying had better adsorption amount for myricetin and rutin than graphene oxide. The calibration graphs of myricetin and rutin in MeOH were linear over 0.10-500.00µg/mL, and the limits of detection and quantification were in the range of 0.00546-0.0182µg/mL and 0.00741-0.0247µg/mL, respectively. A reliable analytical method was developed for recognition targets in tea sample by DES modified nitrogen-doped graphene oxide with satisfactory extraction recoveries (myricetin 99.77%, rutin 98.14%). It was potential for the rapid purification of myricetin and rutin in tea sample combined with the pipette-tip solid-phase extraction.

Synthesis of poly (styrene-divinylbenzene) by nano-TiO2 and the application for pipette-tip solid-phase extraction of flavonoid in Epipremnum aureum rhizome

ABSTRACT PS-DVB-TiO2 modifying with amino (polyethyleneimine or polyaniline) were synthesized, and they were characterized by scanning electron microscopy, fourier transform infrared spectroscopy, thermogravimetric analysis, and Brunauer Emmett Teller. The obtained polymers were used for purification of myricetin and quercetin from Epipremnum aureum rhizome by pipette-tip solid-phase extraction. The satisfactory extraction recoveries for the two targets (myricetin 86.39% and quercetin 83.67%) were obtained by changing different washing and eluted solvents. The result showed that the obtained modified PS-DVB exhibited high mechanical strength and special selectivity to the targets, and the proposed method was successfully applied for purifying complex samples with PT-SPE. Abbreviation PS-DVB: poly (styrene-divinylbenzene); PEI: polyethyleneimine; PANI: polyaniline; SPE: solid-phase extraction; MIP-SPE: molecularly imprinted solid-phase extraction; UAE: ultrasound-assisted extraction; MSPD: molecularly imprinted-matrix solid phase dispersion; PT-SPE: Pipette-tip solid-phase extraction; DMF: N, N-Dimethylformamide; SEM: scanning electron microscopy; TGA: thermogravimetric analysis; FT-IR: fourier transform infrared spectroscopy; BET: Brunauer Emmett Teller.

A hybrid material prepared by controlled growth of a covalent organic framework on amino-modified MIL-68 for pipette tip solid-phase extraction of sulfonamides prior to their determination by HPLC.

A hybrid material was synthesized by growing a covalent organic framework (COF) in-situ on the surface of functionalized metal organic framework (MOF). Specifically, the amino-modified MOF (typeMIL-68) was obtained by reacting indium(III) nitrate and 2-aminoterephthalic acid. Subsequently, it was reacted with tris(4-formylphenyl)amine and tris(4-aminophenyl)amine to obtain the final hybridCOF. This material overcomes the disadvantage of MOF concerning poor stability in aqueous solution and it combines the advantages of MOF and COF. This MOF@COF hybrid material is shown to be a viable adsorbent for the extraction of sulfonamides by pipette tip solid-phase extraction). Following elution with acetonitrile, the sulfonamides were quantified by high performance liquid chromatography using variable wavelength detection (HPLC-VWD). The structure and morphology of the material was characterized by various techniques. Extraction parameters such as amount of adsorbent, sampling rate, sample pH, elution solvent and sample volume were investigated. Under the optimum conditions, the sulfonamides tested (sulfadimethoxine sulfamethoxazole, sulfamonomethoxine, sulfamethazine, sulfamerazine and sulfadiazine) can be determined over a wide linear range (10-2000ng·mL-1), with low limits of detection (1ng·mL-1) and high precision (RSD <5.2%). The method was applied the determination of sulfonamide residues in (spiked) environmental water, milk and meat samples and gave recoveries in the range from 68.9-103.8%, with RSDs of <6.6%. The packed pipette tip column exhibits excellent stability, reproducibility and high adsorption capacity. Graphical abstract A hybrid sorbent was prepared by controlled growth of a covalent organic framework on amino-modified MIL-68 and packed into a pipette tip for sulfonamide extraction. The sensitivity was dramatically increased after optimized extraction, with limit of detection as low as 1 ng·mL-1.

Application of response surface methodology for optimization of metal\u2013organic framework based pipette-tip solid phase extraction of organic dyes from seawater and their determination with HPLC

This paper describes the application of response surface methodology (RSM) to develop a miniaturized metal organic framework based pipette-tip solid phase extraction for the extraction of malachite green (MG), rhodamine B (RB), methyl orange (MO) and acid red 18 (AR) dyes from seawater samples and their determination by high performance liquid chromatography. The effects of various parameters such as pH of the sample solution, type and amount of added salt, type and volume of eluent solvent, concentration of surfactant (triton X-114), sample volume, and number of cycles of extraction and desorption were investigated and optimized by two methods of one-variable-at-a-time and RSM based on Box–Behnken design. Under optimum conditions, the linear range of the method was 0.5–200.0 µg/L for RB and MG and 1.0–150.0 µg/L for AR and MO. Limits of detection of the analytes were obtained in the range of 0.09–0.38 µg/L. Reproducibility of the method (as RSD %) was better than 6.4%. The method has been successfully used for analysis of four dyes in seawater of Chabahar Bay.