Desorption Volume Research Articles

Magnetic solid-phase extraction and determination of ultra-trace amounts of antimony in aqueous solutions using maghemite nanoparticles

A magnetic solid-phase extraction method was developed using maghemite as an efficient sorbent for the separation and preconcentration of antimony prior to its determination by ET-AAS. Maghemite was synthesized through a simple method and characterized by XRD, FT-IR and SEM. Various factors affecting maghemite synthesis, separation and preconcentration of antimony such as desorption solvent type, concentration and volume, desorption temperature and time, sample pH, amount of sorbent, and extraction temperature and time were optimized. The effects of interfering ions were also investigated. Under optimized conditions, the method exhibited good linearity (r2 > 0.9960). The sorption capacity and enrichment factor (EF) of the method were 37.5 mg g−1 and 242, respectively. The limit of detection (LOD) was 0.03 ng mL−1. The intraday, interday, and batch-to-batch relative standard deviations (%RSDs) were quite reasonable. The proposed method was applied to various real samples and the relative recoveries found were between 95.8 and 104.0 %.

Graphene oxide based molecularly imprinted polymers modified with β-cyclodextrin for selective extraction of di(2-ethylhexyl) phthalate in environmental waters.

Graphene oxide based molecularly imprinted polymers modified with β-cyclodextrin were prepared as solid-phase extraction column sorbents for specific recognition and sensitive detection of di(2-ethylhexyl) phthalate in water samples. The morphology and composition of synthesized sorbents were characterized by scanning electron microscopy, thermo-gravimetric analysis, Raman spectroscopy, and Fourier-transform infrared spectroscopy. The conditions affecting the performance of extraction procedures such as desorption solvent types and volume, sample pH and volume were investigated. The loading capacity (8.2μg/mg) of the prepared sorbents increased eight times after modification with β-cyclodextrin. The developed extraction procedures coupled to high-performance liquid chromatography exhibited good linearity (0.2-500μg/L), low limit of detection (0.052μg/L), and good precision (relative standard deviation˂5.7%) under optimized conditions. The developed solid-phase extraction technique with prepared sorbents has been successfully applied in extracting trace di(2-ethylhexyl) phthalate from real natural waters with high efficiency, good selectivity, and desirable recoveries.

Synthesis, characterization and application of a new nano-structured samarium(III) ion-imprinted polymer

This work presents the synthesis of a new nano-structured samarium ion-imprinted polymer (Sm(III)-IIP) by precipitation polymerization. The Sm(III)-IIP nanoparticles were prepared by the copolymerization of Sm(III)–acrylic acid–4-vinylpyridine ternary complex with ethylene glycol dimethacrylate and methyl methacrylate, and then, Sm(III) was leached to obtain Sm(III)-IIP leached particles. Moreover, non-imprinted polymer particles were similarly prepared without Sm(III) ions. The characterization of polymers was carried out by Fourier transform IR spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), thermogravimetric analysis–differential scanning calorimetry (TGA–DSC) and surface analysis. The effect of several parameters such as solution’s pH, sorption and desorption time, type, concentration and volume of eluent on the extraction of the polymers was investigated and optimized by one variable at the time. Optimized parameters were as follows: pH 4; mass sorbent 0.1 g; sorption time, 120 min; desorption time, 120 min; aqueous phase volume, 10 mL. Moreover, it is found that 30 mL of HCl (3 M) provided the most effective elution of Sm3+ ion from IIP beads. The maximum sorbent capacity of the IIPs is 14.91 mg g−1. The sorbent was used for purification of samarium-152 stable isotope. The samarium-152 stable isotope recovery yield was % 99.67. The detection limit of the method was evaluated to be 0.27 ng mL−1. The precision of the method (%RSD, n = 6) was % 0.47.

Dispersive solid-phase extraction based on mesoporous melamine-formaldehyde polymer for sensitive determination of five chlorinated herbicides residues in water by high-performance liquid chromatography

ABSTRACTIn this work, a low-cost melamine-formaldehyde polymer with large-surface-area mesoporous structure was prepared and applied as an efficient solid sorbent for pre-concentration of five kinds of chlorinated herbicides including fomesafen, atrazine, pyrithiobac-sodium, benazolin and acifluorfene from water samples. Extraction parameters such as pH of the sample solution, amount of mesoporous melamine-formaldehyde polymer (mMFP), extraction time, type of desorption solv-ent and volume of the sample were systematically investigated. Combining dispersive solid-phase extraction with high-performance liquid chromatography (HPLC), the detection limits (S/N = 3) of the five herbicides were ranged from 0.04 to 0.18 μg L−1 with good linearity (R2 ≥ 0.9908). Then the tap water and river water samples were analysed by the developed method, and the obtained results indicated that this method provides acceptable recoveries and precisions. mMFP can be prepared through one-pot catalyst-free polymerisation from low-cost starting materials, so that they could be easily scaled up for the sample pre-treatment and have the powerful potentiality in purification of contaminated water.

Metal organic frameworks-derived magnetic nanoporous carbon for preconcentration of organophosphorus pesticides from fruit samples followed by gas chromatography-flame photometric detection

In this work, magnetic nanoporous carbons (MNPCs) based on Zn/Co-MOFs was synthesized via a facial one-step carbonization method. The prepared MNPCs exhibited high specific surface areas, good chemical stability and high extraction efficiency for interest organophosphorus pesticides (OPPs). The good extraction performance of the MNPCs for interest OPPs can be primarily attributed to π-π interaction and hydrophobic interaction between MNPCs and OPPs. Based on it, MNPCs-based MSPE-GC-FPD method was established for the quantification of five OPPs in fruit samples. The main experimental conditions for MSPE of five target OPPs were investigated systematically and optimized, such as the desorption solvent and volume, extracted volume, ionic strength, extraction time and desorption time. Under the optimal conditions, the limits of detection (LODs, S/N = 3) were found to be in the range of 0.018 (ethion) -0.045 (malathion) μg/L. The linearity was 0.05-100 μg/L for phorate, diazinon, ethion and 0.1-100 μg/L for malathion, fenthion respectively. The reproducibility of the method was in the range of 3.5-9.7%. The recovery experiments were carried out by spiking target OPPs at three concentration levels to validate the accuracy of the proposed method, and the recoveries for target OPPs were 84-116%. The results show that the proposed method in this work can be successfully used to analyze OPPs residue in fruit sample.

Gas adsorption on commercial magnesium stearate: The origin of atypical isotherms and BET transform data

The causes of atypical nitrogen adsorption isotherm features of commercial magnesium stearate grades have been investigated through a combination of alternative adsorbates and variation of analytical conditions. Atypical features have previously been identified as having poor linearity of adsorption isotherms at relative pressures applied to the calculation of BET surface area and low pressure hysteresis between adsorption and desorption branches. These features are most pronounced for di-hydrated MgSt and are absent for the anhydrous form: the presence of hydrated water causing atypical features. The possible interaction between hydrated water molecules and nitrogen via the nitrogen quadrupole is investigated through application of non-polar adsorbates; argon and krypton. Low pressure hysteresis is investigated through alteration of equilibration conditions and through truncating adsorption isotherms to successively lower maximum relative pressures before commencing desorption. It is found that atypical gas sorption isotherms are not limited to nitrogen. The effects of these conditions on adsorption and desorption volumes are discussed and a model for the origin of atypical isotherm features is presented. The difference in gas sorption behaviour of anhydrous, mono-hydrated and di-hydrated magnesium stearate is discussed and ultimately the consequences on the calculation of BET surface area is considered.

Magnetic solid-phase extraction with copper ferrite nanoparticles for the separation and preconcentration of ultra-trace amounts of tellurium (IV) ion in aqueous samples

A selective, simple and rapid magnetic solid-phase extraction was developed using copper ferrite (CuFe2O4) as an efficient sorbent for the separation and preconcentration of tellurium (IV) ion prior to its determination by electrothermal atomic absorption spectrometry. In this method, only 5 mg of the sorbent was needed to obtain a satisfactory extraction recovery. The CuFe2O4 was synthesized by means of a simple coprecipitation method and subsequently characterized by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. The factors affecting the separation and preconcentration of tellurium (IV) ions including, the type of desorption solvent, desorption solvent concentration and volume, desorption temperature and time, pH, amount of sorbent, extraction temperature and time were investigated and optimized. The effects of interfering ions on the extraction of Te (IV) ions were also investigated. Under the optimized conditions, the method exhibited a linear dynamic range of 0.04–0.5 µg L−1 with good linearity (r2 = 0.9982). The limit of detection and sorption capacity were found to be 0.012 µg L−1 and 89.0 mg g−1, respectively. Enrichment factor was 223. The intraday, interday, and batch-to-batch relative standard deviations were found to be 3.1, 4.4, and 6.0% for 0.25 µg L−1 concentration. Finally, the proposed analytical procedure was successfully applied to monitor tellurium (IV) ions in some aqueous samples, with relative recoveries of > 96%.

Effect of moisture on the desorption and unsteady-state diffusion properties of gas in low-rank coal

Currently, resource integration in coal-burning facilities and clean energy reconstruction are being strongly pushed forward in China. As a clean fossil energy, unconventional natural gas, such as coalbed methane (CBM), exhibits promise as an energy development strategy. In China, there are abundant CBM resources in the considerable reserves of low-rank coal. Therefore, the study of low-rank coal is the key to realize the high-yield and high-efficiency development of CBM resources in China. In this paper, a new water injection device was designed to prepare coal samples with a variety of moisture contents, and a novel method to measure the gas desorption properties in coal containing water was introduced. On this basis, the gas desorption law in low-rank coal with different moisture contents was tested, and the effect of moisture on the gas diffusion properties in low-rank coal was analyzed. The results indicate that the initial gas desorption volume of low-rank coal is extremely large and that the gas desorption law in the moisture-containing low-rank coal can be described by Airey's empirical equation. It is also observed that the ultimate gas desorption volume, initial gas desorption rate and initial effective gas diffusion coefficient all shift toward the direction that is beneficial to CBM development. Therefore, reducing the moisture content in low-rank coals through certain techniques can dramatically enhance the gas migration behavior and achieve the purpose of high-yield CBM development.

Determination of three tetracyclines in bovine milk using magnetic solid phase extraction in tandem with dispersive liquid-liquid microextraction coupled with HPLC

A novel analytical method namely magnetic solid phase extraction in tandem with dispersive liquid-liquid microextraction was developed and used for the extraction/preconcentration of tetracycline (TCN), oxytetracycline (OTC) and doxycycline (DC) from bovine milk sample before HPLC-UV analysis. The β-cyclodextrin functionalized silica-coated magnetic graphene oxide (Fe3O4@SiO2@GO-β-CD) was used as an adsorbent. The adsorbent was fully characterized using FT-IR, SEM, EDX and Zeta potential techniques. The effective parameters on the performance of the method such as extraction solvent type and volume, adsorbent amount, desorption solvent type and volume, disperser solvent type, desorption time, ionic strength and pH value were investigated. The limit of detection (LOD) and limit of quantification (LOQ) were obtained in the ranges of 1.8–2.9 μg L−1 and 6.1–9.7 μg L−1, respectively. The linearity was in the range of 10.0–200.0 μg L−1 with satisfactory determination coefficients (R2) higher than 0.9929 and a good precision (RSD < 8.8%). The recovery percentages for the analytes in real samples (bovine milk and water) were achieved in a range from 70.6 to 121.5%.

Determination of nitrosamines in skin care cosmetics using Ce-SBA-15 based stir bar-supported micro-solid-phase extraction coupled with gas chromatography mass spectrometry

Improvement for nitrosamine detections, particularly in consumables and products applied to skin is a growing area of research due to implications of nitrosamines on human health. In this study, mesoporous silica, SBA-15 was doped with various ceria loadings and used in the stir bar-supported micro-solid-phase extraction (SB-µ-SPE) of nitrosamines in cosmetic samples. The synthesized sorbents were characterized using field emission scanning electron microscopy and energy dispersive X-ray spectrometry. The effects of extraction variables (sorbent type and amount; desorption time, solvent, and volume; extraction time; and ionic strength) were determined. This newly improved method provides good linear range (R2 value up to 0.9985) and trace detection (2.7–3.4 ng mL−1). Relative standard deviation (RSD) values determined at different concentration levels ranged between 2.3 and 8.0%, and the screened sorbent shows excellent regeneration ability for four cycles. With this developed Ce-SBA-15 based stir bar-supported micro-solid-phase extraction, trace levels of nitrosamines can be detected in matrices that are commonly encountered by humans.

Magnetic carbon nanotube composite for the preconcentration of parabens from water and urine samples using dispersive solid phase extraction

This study describes the use of a magnetic multi-walled carbon nanotube composite for the preconcentration of nine parabens (methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, phenyl and benzylparaben) from water and urine samples after in situ acetylation. The enriched extracts were obtained by dispersive magnetic solid phase extraction (DMSPE) and analysed by gas chromatography with mass spectrometry (GC–MS). Several parameters affecting the adsorption (extraction time, magnetic material mass and ionic strength) and desorption (desorption solvent nature and volume, and desorption time) DMSPE steps were investigated. Matrix-matched calibration was recommended for quantification of the samples. Linearities in the 0.5–150 ng mL−1 range were obtained, depending on the compound. Under the optimal experimental conditions, the limits of detection ranged between 0.03 and 2.0 ng mL-1, depending on the sample matrix and the paraben congener. None of the samples analysed contained the above mentioned parabens. The method was validated with two water samples (harbour and wastewater treatment plant) and two urine samples spiked at two concentration levels. Recoveries in the 81–119% range were obtained.

Three-dimensional multi-walled carbon nanotubes@g-C3N4@Fe3O4nanocomposites-based magnetic solid phase extraction for the determination of polycyclic aromatic hydrocarbons in water samples

In this study, three-dimensional multi-walled carbon nanotubes@g-C3N4@Fe3O4 nanocomposites (3D MWNTs@g-C3N4@Fe3O4 nanocomposites) were prepared and used as a novel magnetic solid phase extraction (MSPE) sorbent for the analysis of 16 polycyclic aromatic hydrocarbons (PAHs). The novel nanocomposites were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), and vibrating sample magnetometer (VSM) methods. To achieve the best extraction efficiency, several experimental parameters, including sorbent amount, extraction time, stirring rate, ionic strength, desorption solvent, desorption volume and desorption time, were optimized. Under the optimized preparation and extraction conditions, the proposed method showed the limits of detection (LODs) for polycyclic aromatic hydrocarbons (PAHs) were found to be in the range of 0.001–0.5 μg L−1, limits of quantification (LOQs) were in the range of 0.005–0.8 μg L−1 and their relative standard deviations (RSDs) were lower than 5.0%. The proposed MSPE method was applied successfully in the analysis of PAHs in rainwater, river water and industrial wastewater samples. The recovery of the PAHs in all samples spiked with 5 g L−1 ranged from 82.4 to 116.9% with RSDs below 9.7%.

Spatio-temporal evolution of apparent resistivity during coal-seam hydraulic flushing

Hydraulic flushing in gas predrainage is widely used, but the hydraulic-flushing effect is evaluated in a traditional way, by determining the desorption volume, moisture content, gas drainage rate and other conventional indices. To verify the rationality and feasibility of the multielectrode resistivity method in the evaluation of coal-seam hydraulic flushing and to research the spatio-temporal evolution of apparent resistivity during hydraulic flushing, a field test was conducted in 17# coal seam at Nuodong Mine, Guizhou. During hydraulic flushing, four stages were defined according to the variation in coal rock resistivity with time, namely, the preparation stage, the sharply decreasing stage, the rapidly increasing stage and the steady stage. The apparent resistivity of the coal rock mass is affected mainly by its own degree of fragmentation and flushing volume. A more serious rupture and a greater flushing volume yield a smaller apparent resistivity during the sharply decreasing stage and a higher resistivity during the stable stage. After three months of gas predrainage, the residual gas content and the gas pressure at different points in the expected affected area decrease below the critical value. Changes in the residual gas content and gas pressure at these points are consistent with the apparent resistivity, which validates the rationality and feasibility of the multielectrode resistivity method in evaluating coal-seam hydraulic flushing.

A hybrid material composed of a polyoxometalate of type BeW12O40 and an ionic liquid immobilized onto magnetic nanoparticles as a sorbent for the extraction of organophosphorus pesticides prior to their determination by gas chromatography.

The authors describe a method for the extraction of organophosphorus pesticides (OPPs) by using a magnetically separable sorbent consisting of a polyoxometalate of type BeW12O40 supported on imidazole functionalized silica-coated cobalt ferrite. The sorbent was characterized by X-ray powder diffraction, field-emission scanning electron micrographs, vibrating sample magnetometry and FT-IR. The effects of the amount of adsorbent, pH value, salt concentration, extraction time, desorption solvent nature and volume and desorption time were investigated. Under optimal conditions, the method resulted in the following figures of merit: (a) thelinear parts of thecalibration plots typically extend from 0.08 to 300μg mL-1 of OPPs; (b) detection limits are between 0.02 to 0.06ng mL-1; and (c), extraction recoveries from spiked samples vary from 70.0 to 89.2%, with relative standard deviations between 5.4 and 7.6%. The nanocomposites can be reused up to 10 times. Compared to other methods for pretreatment and preconcentration of OPPs, the new method is more rapid, sensitive, accurate and eco-friendly. The method was successfully applied to the determination of the OPP residues in water samples and fruit juices. Graphical Abstract Schmatic presenation of the synthesis of core-shell magnetic nanoparticles (MNPs) of the type BeW12O40-ILSCCFNPs, and their application as sorbent for magnetic solid-phase extraction (MSPE) of organophosphorus pesticides.

Synthesis of polydopamine-functionalized magnetic graphene and carbon nanotubes hybrid nanocomposites as an adsorbent for the fast determination of 16 priority polycyclic aromatic hydrocarbons in aqueous samples.

A novel adsorbent made of polydopamine-functionalized magnetic graphene and carbon nanotubes hybrid nanocomposite was synthesized and applied to determine 16 priority polycyclic aromatic hydrocarbons by magnetic solid phase extraction in water samples. FTIR spectroscopy, transmission electron microscopy, scanning electron microscopy, and Raman spectroscopy consistently indicate that the synthesized adsorbents are made of core-shell nanoparticles well dispersed on the surface of graphene and carbon nanotubes. The major factors affecting the extraction efficiency, including the pH value of samples, the amount of adsorbent, adsorption time and desorption time, type and volume of desorption solvent, were systematically optimized. Under the optimum extraction conditions, a linear response was obtained for polycyclic aromatic hydrocarbons between concentrations of 10 and 500ng/L with the correlation coefficients ranging from 0.9958 to 0.9989, and the limits of detection (S/N=3) were between 0.1 and 3.0ng/L. Satisfactory results were also obtained when applying these magnetic graphene/carbon nanotubes/polydopamine hybrid nanocomposites to detect polycyclic aromatic hydrocarbons in several environmental aqueous samples.

Development of a Microfluidic Open Interface with Flow Isolated Desorption Volume for the Direct Coupling of SPME Devices to Mass Spectrometry.

Technologies that efficiently integrate the sampling and sample preparation steps with direct introduction to mass spectrometry (MS), providing simple and sensitive analytical workflows as well as capabilities for automation, can generate a great impact in a vast variety of fields, such as in clinical, environmental, and food-science applications. In this study, a novel approach that facilitates direct coupling of Bio-SPME devices to MS using a microfluidic design is presented. This technology, named microfluidic open interface (MOI), which operates under the concept of flow-isolated desorption volume, consists of an open-to-ambient desorption chamber (V ≤ 7 μL) connected to an ionization source. Subsequently, compounds of interest are transported to the ionization source by means of the self-aspiration process intrinsic of these interfaces. Thus, any ionization technology that provides a reliable and constant suction, such as electrospray ionization (ESI), atmospheric-pressure chemical ionization (APCI), or inductively coupled plasma ionization (ICP), can be hyphenated to MOI. Using this setup, the desorption chamber is used to release target compounds from the coating, while the isolation of the flow enables the ionization source to be continuously fed with solvent, all without the necessity of employment of additional valves. As a proof of concept, the design was applied to an ESI-MS/MS system for experimental validation. Furthermore, numerical simulations were undertaken to provide a detailed understanding of the fluid flow pattern inside the interface, then used to optimize the system for better efficiency. The analytical workflow of the developed Bio-SPME-MOI-MS setup consists of the direct immersion of SPME fibers into the matrix to extract/enrich analytes of interest within a short period of time, followed by a rinsing step with water to remove potentially adhering proteins, salts, and/or other interfering compounds. Next, the fiber is inserted into the MOI for desorption of compounds of interest. Finally, the volume contained in the chamber is drained and moved toward the electrospray needle for ionization and direct introduction to MS. Aiming to validate the technology, the fast determination of selected immunosuppressive drugs (e.g., tacrolimus, cyclosporine, sirolimus, and everolimus) from 100 μL of whole blood was assessed. Limits of quantitation in the subppb range were obtained for all studied compounds. Good linearity (r2 ≥ 0.99) and excellent precision, with (8%) and without (14%) internal standard correction, were attained.

Coal Temperature Variation Mechanism during Gas Desorption Process

To further reveal the mechanism of coal gas migration, the reasons for coal temperature changes during the methane desorption process were analyzed from the aspect of molecular motion and the thermodynamic theory. The temperature change mechanism was investigated, and the mathematical equation was established to describe the variation of temperature change during the methane desorption and diffusion process. The established equation was applied for the calculation of temperature change for two types of coal samples, and the measured and theoretical values of temperature changes were obtained. The results show that the temperature changes in the coal gas desorption process are mainly caused by the heat adsorption. The heat adsorption phenomenon was also caused by free gas expansion during the pressure relief process. The gas diffusion and work done for gas seepage also need heat adsorption. The temperature change is positively correlated to the coal gas pressure, quantity, and limit value of gas desorption volume. Due to the poor insulation in the test system, the difference between the theoretical and the measured temperature change values increase with the adsorption equilibrium pressure. It is helpful to further reveal the mechanism of coal and gas outburst. It also has an important reference value for controlling gas dynamic disasters in coal mines.

In-situ regeneration of activated carbon with electric potential swing desorption (EPSD) for the H2S removal from biogas

In-situ regeneration of a granular activated carbon was conducted for the first time using electric potential swing desorption (EPSD) with potentials up to 30 V. The EPSD system was compared against a standard non-potential system using a fixed-bed reactor with a bed of 10 g of activated carbon treating a gas mixture with 10,000 ppm H2S. Breakthrough times, adsorption desorption volume, capacities, effect of regeneration and desorption kinetics were investigated. The analysis showed that desorption of H2S using the new EPSD system was 3 times quicker compared with the no potential system. Hence, physical adsorption using EPSD over activated carbon is efficient, safe and environmental friendly and could be used for the in-situ regeneration of granular activated carbon without using a PSA and/or TSA system. Additionally, adsorption and desorption cycles can be obtained with a classical two column system, which could lead towards a more efficient and economic biogas to biomethane process.

Rapid Determination of Aconitum Alkaloids from Human Urine by UHPLC-HRMS.

Aconitum alkaloid poisoning is a type of poisoning caused by accidental ingestion and clinical use of herbal drugs in many countries. In this study, we developed an in-syringe dispersive micro solid-phase extraction (DMSPE) method for selective extraction of aconitine, benzoylaconine and aconine from human urine using a type of polymer material. All of the parameters influencing the extraction efficiency such as the type and amount of sorbent, the extraction time and the desorption solvent and volume in DMSPE were carefully investigated and optimized. Using DMSPE method, the absence of evaporation and centrifugation steps reduced the consuming time of sample preparation. Samples were analyzed by ultra high-performance liquid chromatography-high-resolution mass spectrometry on an HSS T3 analytical column. The results showed that the DMSPE method yielded fewer relative and absolute matrix effects, which reduced the sample to sample variability in human urine. The limits of detection and limits of quantitation of this method were determined to be 0.08-0.1 and 0.2-0.3 μg/L, respectively. The average recoveries of the analytes were between 88.6% and 107.2% with the intra- and interday precisions ranging from 2.1% to 6.4% and from 5.9% to 13.9%, respectively. The method presented here is an efficient, low-cost and selective extraction of aconitine, benzoylaconine and aconine from human urine.

Magnetic molecularly imprinted polymers for selective extraction and determination of naphthols

The authors describe a magnetic molecular imprinted polymer (MMIP) for the extraction and detection of naphthols synthesized by surface imprinting technology using 1-naphthol as the template. The MMIPs were characterized by FT-IR spectroscopy, X-ray diffraction, thermogravimetric analysis and vibrating sample magnetometry. They are shown to be viable magnetic adsorbents for various naphthols. The effects of sample volume, pH value, ionic strength, adsorption time, and desorption solvent, volume and time were optimized. Following elution with methanol, the naphthols were quantified by HPLC. Under optimal experimental conditions, the MSPE-HPLC method exhibits a linear range from 0.02–25 mg·kg−1 for naphthols. The limits of detection (LODs) are 6 μg·kg−1 for both naphthols. The method was applied to the determination of 1-naphthol and 2-naphthol in hair coloring products. Recoveries are in the range of 88.8–101.6% with relative standard deviations of less than 9.3%.