- Research Article
- Open Access
Determination of carbamazepine in urine and water samples using amino-functionalized metal–organic framework as sorbent
© The Author(s) 2018
- Received: 5 October 2017
- Accepted: 26 June 2018
- Published: 30 June 2018
A stable and porous amino-functionalized zirconium-based metal organic framework (Zr-MOF-NH2) containing missing linker defects was prepared and fully characterized by FTIR, scanning electron microscopy, powder X-ray diffraction, and BET surface area measurement. The Zr-MOF-NH2 was then applied as an adsorbent in pipette-tip solid phase extraction (PT-SPE) of carbamazepine. Important parameters affecting extraction efficiency such as pH, sample volume, type and volume of eluent, amount of adsorbent, and number of aspirating/dispensing cycles for sample solution and eluent solvent were investigated and optimized. The best extraction efficiency was obtained when pH of 100 µL of sample solution was adjusted to 7.5 and 5 mg of the sorbent was used. Eluent solvent was 10 µL methanol. Linear dynamic range was found to be between 0.1 and 50 µg L−1 and limit of detection for 10 measurement of blank solution was 0.05 µg L−1. This extraction method was coupled to HPLC and was successfully employed for the determination of carbamazepine in urine and water samples. The strategy combined the advantages of fast and easy operation of PT-SPE with robustness and large adsorption capacity of Zr-MOF-NH2.
- Pipette-tip solid phase extraction
- Zirconium-based metal–organic framework
- Urine analysis
Carbamazepine (CBZ, 5H-dibenzo [b,f] azepine-5-carboxamide) often used as anticonvulsant drug for treatment of epilepsy [1, 2]. Whenever a patient consumes CBZ, about 2–3% of this drug will excrete unchanged through his urine and enters into environmental aquatic ecosystems . Studies confirmed that CBZ can be present in wastewater (up to 6.3 µg L−1) [4–7], surface water (up to 1.1 µg L−1) [8, 9], and drinking water (around 30 ng L−1) [10, 11]. Biodegradation of CBZ is very difficult in environmental media owing to its low solubility and stability in water. Therefore, several methods including advanced oxidation processes (AOPs), adsorption on various sorbent media have been employed for the removal and extraction of it [1, 2, 12–14].
In recent years, some sample preparation techniques such as liquid–liquid extraction (LLE) , dispersive liquid–liquid microextraction (DLLME)  and solid-phase extraction (SPE)  have been used for isolation and extraction of CBZ in complicated matrices. SPE is a prevalent procedure for pre-treatment of various pharmaceutical analytes due to its reproducibility, high recovery and simple operation. Miniaturized SPE has been developed to overcome on the problems raised by conventional SPE processes such as matrix effect, low detection limit, losses of analytes, and environmental problems due to consumption of large amounts of organic solvents.
Pipette-tip solid-phase extraction (PT-SPE) is a convenience, and microscale of SPE method which reduces amount of sorbent and reagents and saves the analysis time [18–20]. This technique required several repeated aspirating/dispensing cycles to complete the extraction procedure.
Intrigued by the above-mentioned findings, we encouraged to prepare and use the bio inspired sponge, amino-functionalized Zr-MOF, for micro-scale solid phase extraction and determination of the carbamazepine. Several parameters affecting extraction efficiency including pH, type and volume of eluent, volume of sample solution, and amount of sorbent, number of draw/eject of sample solution and eluent solvent type were tested and optimized. Finally, the method was used for the determination of carbamazepine in urine and water samples.
Chemicals and materials
All reagents (analytical grade) were purchased from Sharloa (Spain) and used as received, except HPLC solvents which were of chromatographic grade. All aqueous solutions were prepared using ultra-pure Milli-Q® purification system. 20 µL pipette-tips (Dragon Lab, China) were used as micro columns. Carbamazepine was obtained from Sigma-Aldrich (St. Louis, MO, USA).
Synthesis of Zr-MOF-NH2 sorbent
Zr-MOF-NH2 was synthesized according to the Hupp/Farha method  with minor modifications. In a 25 mL vial, dimethyl formamide (5 mL) and concentrated HCl (2.85 mL, 850 mmol) were added to 0.125 g, (0.54 mmol) of ZrCl4 before being sonicated for 10 min. A mixture of 2-aminoterephthalic acid (0.134 g, 0.75 mmol) and dimethyl formamide (10 mL) were then added to the clear solution and the mixture was sonicated for 20 more minutes. Afterwards, the capped vial was placed in a pre-heated oven at 80 °C for 15 h. After cooling to room temperature, the solid Zr-MOF-NH2 was filtered and washed with dimethyl formamide, and then with ethanol several times. In order to evaporate any solvents, this product was left for several hours under the hood and then was dried under reduced pressure (80 °C, 3 h). The solid Zr-MOF-NH2 was then activated at 120 °C for 12 h under high vacuum prior to measuring N2 isotherms.
Characterization of Zr-MOF-NH2
Fourier-transform infrared spectroscopy (FT-IR) spectra were recorded using a Perkin-Elmer FTIR (USA). Powder X-ray diffraction (PXRD) patterns were recorded on a Philips X’pert diffractometer (Germany) with monochromated Cu Kα radiation (λ = 1.5418 Å) within the range of 1.5° < 2θ < 38°. Samples for scanning electron microscopy (SEM) were sputtered with a layer of Os (5-nm thickness) prior to taking images on a Hitachi S-4800 SEM (Japan) with a 15.0 kV accelerating voltage. BET surface area measurements were made at 77 K with liquid nitrogen on a Micrometrics TriStar 3020 (N2) surface area analyzer (Britain). Zr-MOF-NH2was degassed for 12 h at 120 °C before the measurement under a stream of nitrogen.
Determination of CBZ was performed on an HPLC manufactured by Cecil company (England), equipped with a C18 ACE column (250 × 4.6 mm, 5 μm particle sizes) and a UV detector at wavelength of 210 nm. A mixture of water: acetonitrile (75:25) were used as mobile phase (isocratic elusion). Column was thermostated at room temperature. Injection volume and flow rate were 10 µL and 1 mL min−1, respectively.
CBZ Extraction procedure
5 mg of Zr-MOF-NH2 was transferred to a 20 µL pipette-tip as micro column and attached to 100 µL variables sampler (Isolable, Germany). 100 µL sample solution was then introduced to column and passed over the sorbent and dispensed back to a 1 mL test-tube. The same sample solution was loaded into the micro column for 5 cycles. Adsorbed CBZ was then eluted by 10 µL of methanol in a 1 mL test-tube for 7 cycles, from which, 20 µL was injected to HPLC. Urine sample was collected from a healthy female and stored at − 80 °C and used throughout all experiments. This participant was not using supplements containing CBZ. Before start of the experiments, sample was brought to the room temperature, of which 250 µL was transferred to a canonical centrifuge tube. After addition of 1 mL of 1 M ammonium persulphate, it was heated in a water bath for 60 min at 95 °C. Then, this solution was brought to room temperature and was extracted by means of the suggested procedure. Tap water was obtained from laboratory and sample was filtered through a 0.45 µm Whatman filter paper and spiked with carbamazepine.
Characterization of adsorbent
The morphology of the MOF was examined by scanning electron microscopy (SEM) (Fig. 4). Unlike the octahedral crystal shape of Zr-MOF-NH2 obtained by other methods , the SEM images of the nominal MOF showed aggregates of quasi-spherical particles between 100 and 200 nm.
Optimization of PT-SPE procedure
To achieve the best extraction efficiency, we tried to optimize the conditions influencing the extraction processes as described below. All optimization experiments were performed with 10 µg L−1 of CBZ solution.
Effect of pH
Amount of adsorbent
Effect of volume of sample solution
Effect of volume of eluent
Effect of draw/eject of sample solution and eluent
The procedure of aspiration of a solution into pipette tip and dispensed back into the same sample tube is called aspirating/dispensing (or draw/eject) cycles, which a critical factor for PT-SPE extraction. Therefore, the influence of this parameter on the extraction efficiency was examined between 3 and 20 cycles. After 5 cycles, the extraction of CBZ from sample solution was found to be complete. Meanwhile, the best elusion of CBZ from the sorbent was occured at 7 cycles of draw/eject of eluent. In higher number of cycles, the efficiency was decreased, which is probably due to the back extraction of the analyte from adsorbent into the sample solution, causing a decrease in the recovery.
Reusability of the sorbent
To investigate the stability and reusability of the Zr-MOF-NH2 packed micro column, after desorption of CBZ from the adsorbent, the column was washed five cycles with methanol and then five cycles with deionized water. After that, several extraction and elution operation cycles were carried out under the optimized conditions. The result of experiments indicated that the adsorbent could be reused at least for eight times with a decrease of only 5% in extraction recovery. As the powder PXRD patterns of the Zr-MOF-NH2 before and after adsorption shown in the Fig. 3, the crystallinity of the MOF was reserved during the experimental conditions, confirming the stability of the MOF under the experimental conditions.
The adsorption capacity of the Zr-MOF-NH2 was determined by the batch experiments. For this purpose, a standard solution containing 2000 mg L−1 of CBZ was applied. The amount of adsorbed CBZ was calculated by determination of difference between initial and final concentration of CBZ after adsorption. The maximum sorption capacity was defined as the total amount of adsorbed CBZ per gram of the Zr-MOF-NH2. The obtained capacity was found to be 32 mg g−1. High adsorption capacity indicated that large porosity and large surface area of adsorbent.
Analytical figures of merit for Zr-MOF-NH2 for extraction of CBZ
Linear Dynamic range (μg L−1)
R2 (determination coefficient)
Repeatability (RSD%) (50 μg L−1)
Limit of detection (µg L−1)
Total extraction time (min)
Determination of carbamazepine in real samples
Evaluation of carbamazepine in real samples
Concentration found (µg L−1)
Spiked at concentration (µg L−1)
Comparison of proposed method with other methods
Comparisons of the proposed methods with other methods for extraction of CBZ
LOD (µg L−1)
LOQ (µg L−1)
Molecularly imprinted polymer
SPE/graphene- silica gel
SPE/modified sulfur nanoparticles
SPE/oasis HLB cartridges
A porous amino-functionalized metal organic framework containing missing-linker defects was firstly prepared and then applied for pipette-tip solid phase extraction of a drug, carbamazepine. The total time of analysis, including extraction was less than 12 min. The Zr-MOF-NH2 sorbent was used for at least eight extractions without any significant change in its capacity or repeatability. Only 5 mg of the sorbent was enough for filling the PT. The presence of more open active zirconium sites, more numbers of hydroxyl groups, the large porosity, very high surface area, the amino functionality, and the suitable pore size of the Zr-MOF-NH2 could improve the extraction of CBZ. Moreover, the fast, inexpensive, effective, reliable, applicable and organic solvent-free method can open up new practical applications for MOFs in SPE based analytical techniques.
MRRK did the practical work and wrote the manuscript. Both ARO and BRK co-wrote the manuscript and ARO also synthesized MOF. MK co-wrote the manuscript and planned the study. All authors read and approved the final manuscript.
Authors hereby thanks from health laboratory of Zabol University of Medical Sciences for cooperation to perform experiments.
The authors have declared no competing interests.
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- Beltran A, Marcé RM, Cormack PAG, Borrull F (2009) Synthesis by precipitation polymerisation of molecularly imprinted polymer microspheres for the selective extraction of carbamazepine and oxcarbazepine from human urine. J Chromatogr A 1216(12):2248–2253View ArticlePubMedGoogle Scholar
- Asgari S, Bagheri H, Es-haghi A, AminiTabrizi R (2017) An imprinted interpenetrating polymer network for microextraction in packed syringe of carbamazepine. J Chromatogr A 1491:1–8View ArticlePubMedGoogle Scholar
- McEneff G, Barron L, Kelleher B, Paull B, Quinn B (2013) The determination of pharmaceutical residues in cooked and uncooked marine bivalves using pressurised liquid extraction, solid-phase extraction and liquid chromatography–tandem mass spectrometry. Anal Bioanal Chem 405(29):9509–9521View ArticlePubMedGoogle Scholar
- Ternes TA (1998) Occurrence of drugs in German sewage treatment plants and rivers1. Water Res 32(11):3245–3260View ArticleGoogle Scholar
- Miao XS, Metcalfe CD (2003) Determination of carbamazepine and its metabolites in aqueous samples using liquid chromatography–electrospray tandem mass spectrometry. Anal Chem 75(15):3731–3738View ArticlePubMedGoogle Scholar
- Kosjek T, Andersen HR, Kompare B, Ledin A, Heath E (2009) Fate of carbamazepine during water treatment. Environ Sci Technol 43(16):6256–6261View ArticlePubMedGoogle Scholar
- Miao XS, Yang JJ, Metcalfe CD (2005) Carbamazepine and its metabolites in wastewater and in biosolids in a municipal wastewater treatment plant. Environ Sci Technol 39(19):7469–7475View ArticlePubMedGoogle Scholar
- Andreozzi R, Marotta R, Pinto G, Pollio A (2002) Carbamazepine in water: persistence in the environment, ozonation treatment and preliminary assessment on algal toxicity. Water Res 36(11):2869–2877View ArticlePubMedGoogle Scholar
- Mashayekhi HA, Abroomand-Azar P, Saber-Tehrani M, Husain SW (2010) Rapid determination of carbamazepine in human urine, plasma samples and water using DLLME followed by RP–LC. Chromatographia 71(5–6):517–521View ArticleGoogle Scholar
- Dai CM, Zhang J, Zhang YL, Zhou XF, Duan YP, Liu SG (2013) Removal of carbamazepine and clofibric acid from water using double templates–molecularly imprinted polymers. Environ Sci Pollut Res 20(8):5492–5501View ArticleGoogle Scholar
- Zhou XF, Dai CM, Zhang YL, Surampalli RY, Zhang TC (2011) A preliminary study on the occurrence and behavior of carbamazepine (CBZ) in aquatic environment of Yangtze River Delta, China. Environ Monit Assess 173(1):45–53View ArticlePubMedGoogle Scholar
- Prieto A, Schrader S, Bauer C, Möder M (2011) Synthesis of a molecularly imprinted polymer and its application for microextraction by packed sorbent for the determination of fluoroquinolone related compounds in water. Anal Chim Acta 685(2):146–152View ArticlePubMedGoogle Scholar
- C-m Dai, Geissen SU, Zhang YL, Zhang YJ, Zhou XF (2010) Performance evaluation and application of molecularly imprinted polymer for separation of carbamazepine in aqueous solution. J Hazard Mater 184(1–3):156–163Google Scholar
- Akpinar I, Yazaydin AO (2017) Rapid and efficient removal of carbamazepine from water by UiO-67. Ind Eng Chem Res. https://doi.org/10.1021/acs.iecr.7b03208 View ArticleGoogle Scholar
- Teng XW, Wang SWJ, Davies NM (2003) Stereospecific high-performance liquid chromatographic analysis of ibuprofen in rat serum. J Chromatogr B 796(2):225–231View ArticleGoogle Scholar
- Behbahani M, Najafi F, Bagheri S, Bojdi MK, Salarian M, Bagheri A (2013) Application of surfactant assisted dispersive liquid–liquid microextraction as an efficient sample treatment technique for preconcentration and trace detection of zonisamide and carbamazepine in urine and plasma samples. J Chromatogr A 1308:25–31View ArticlePubMedGoogle Scholar
- Beltran A, Caro E, Marcé RM, Cormack PAG, Sherrington DC, Borrull F (2007) Synthesis and application of a carbamazepine-imprinted polymer for solid-phase extraction from urine and wastewater. Anal Chim Acta 597(1):6–11View ArticlePubMedGoogle Scholar
- Rezaei Kahkha MR, Daliran S, Oveisi AR, Kaykhaii M, Sepehri Z (2017) The mesoporous porphyrinic zirconium metal-organic framework for pipette-tip solid-phase extraction of mercury from fish samples followed by cold vapor atomic absorption spectrometric determination. Food Anal Methods 10(7):2175–2184View ArticleGoogle Scholar
- Rezaei Kahkha MR, Kaykhaii M, Afarani MS, Sepehri Z (2016) Determination of mefenamic acid in urine and pharmaceutical samples by HPLC after pipette-tip solid phase microextraction using zinc sulfide modified carbon nanotubes. Anal Methods 8(30):5978–5983View ArticleGoogle Scholar
- Kaykhaii M, Yahyavi H, Hashemi M, Khoshroo MR (2016) A simple graphene-based pipette tip solid-phase extraction of malondialdehyde from human plasma and its determination by spectrofluorometry. Anal Bioanal Chem 408(18):4907–4915View ArticlePubMedGoogle Scholar
- Dhakshinamoorthy A, Asiri AM, García H (2016) Metal-organic framework (MOF) compounds: photocatalysts for redox reactions and solar fuel production. Angew Chem Int Ed 55(18):5414–5445View ArticleGoogle Scholar
- Aguado S, El-Jamal S, Meunier F, Canivet J, Farrusseng D (2016) A Pt/Al2O3-supported metal-organic framework film as the size-selective core-shell hydrogenation catalyst. Chem Commun 52(44):7161–7163View ArticleGoogle Scholar
- Mason JA, Veenstra M, Long JR (2014) Evaluating metal-organic frameworks for natural gas storage. Chem Sci 5(1):32–51View ArticleGoogle Scholar
- Farha OK, Özgür Yazaydın A, Eryazici I, Malliakas CD, Hauser BG, Kanatzidis MG et al (2010) De novo synthesis of a metal–organic framework material featuring ultrahigh surface area and gas storage capacities. Nat Chem 2(11):944–948View ArticlePubMedGoogle Scholar
- Navarro-Sánchez J, Argente-García AI, Moliner-Martínez Y, Roca-Sanjuán D, Antypov D, Campíns-Falcó P et al (2017) Peptide metal-organic frameworks for enantioselective separation of chiral drugs. J Am Chem Soc 139(12):4294–4297View ArticlePubMedGoogle Scholar
- Bao Z, Chang G, Xing H, Krishna R, Ren Q, Chen B (2016) Potential of microporous metal-organic frameworks for separation of hydrocarbon mixtures. Energy Environ Sci 9(12):3612–3641View ArticleGoogle Scholar
- Cunha D, Ben Yahia M, Hall S, Miller SR, Chevreau H, Elkaïm E et al (2013) Rationale of drug encapsulation and release from biocompatible porous metal-organic frameworks. Chem Mater 25(14):2767–2776View ArticleGoogle Scholar
- Wu MX, Yang YW (2017) Metal–organic framework (MOF)-based drug/cargo delivery and cancer therapy. Adv Mater. https://doi.org/10.1002/adma.201606134 View ArticlePubMedPubMed CentralGoogle Scholar
- Li P, Moon S-Y, Guelta MA, Lin L, Gómez-Gualdrón DA, Snurr RQ et al (2016) Nanosizing a metal-organic framework enzyme carrier for accelerating nerve agent hydrolysis. ACS Nano 10(10):9174–9182View ArticleGoogle Scholar
- Bobbitt NS, Mendonca ML, Howarth AJ, Islamoglu T, Hupp JT, Farha OK et al (2017) Metal-organic frameworks for the removal of toxic industrial chemicals and chemical warfare agents. Chem Soc Rev. https://doi.org/10.1039/c7cs00108h View ArticlePubMedGoogle Scholar
- Wang TC, Hod I, Audu CO, Vermeulen NA, Nguyen ST, Farha OK et al (2017) Rendering high surface area, mesoporous metal-organic frameworks electronically conductive. ACS Appl Mater Interfaces 9(14):12584–12591View ArticlePubMedGoogle Scholar
- Zhang FM, Dong LZ, Qin JS, Guan W, Liu J, Li SL et al (2017) Effect of imidazole arrangements on proton-conductivity in metal-organic frameworks. J Am Chem Soc 139(17):6183–6189View ArticlePubMedGoogle Scholar
- Moghadam PZ, Fairen-Jimenez D, Snurr RQ (2016) Efficient identification of hydrophobic MOFs: application in the capture of toxic industrial chemicals. J Mater Chem A 4(2):529–536View ArticleGoogle Scholar
- Peterson GW, Mahle JJ, DeCoste JB, Gordon WO, Rossin JA (2016) Extraordinary NO2 removal by the metal-organic framework UiO-66-NH2. Angew Chem Int Ed 55(21):6235–6238View ArticleGoogle Scholar
- Lustig WP, Mukherjee S, Rudd ND, Desai AV, Li J, Ghosh SK (2017) Metal-organic frameworks: functional luminescent and photonic materials for sensing applications. Chem Soc Rev. https://doi.org/10.1039/c6cs00930a View ArticlePubMedGoogle Scholar
- Kreno LE, Leong K, Farha OK, Allendorf M, Van Duyne RP, Hupp JT (2012) Metal-Organic Framework Materials as Chemical Sensors. Chem Rev 112(2):1105–1125View ArticlePubMedGoogle Scholar
- Long JR, Yaghi OM (2009) The pervasive chemistry of metal–organic frameworks. Chem Soc Rev 38(5):1213–1214View ArticlePubMedGoogle Scholar
- Khan NA, Hasan Z, Jhung SH (2013) Adsorptive removal of hazardous materials using metal-organic frameworks (MOFs): a review. J Hazard Mater 244:444–456View ArticlePubMedGoogle Scholar
- Katz MJ, Mondloch JE, Totten RK, Park JK, Nguyen ST, Farha OK et al (2014) Simple and compelling biomimetic metal–organic framework catalyst for the degradation of nerve agent simulants. Angew Chem Int Ed 53(2):497–501View ArticleGoogle Scholar
- Azarifar D, Ghorbani-Vaghei R, Daliran S, Oveisi AR (2017) A multifunctional zirconium-based metal–organic framework for the one-pot tandem photooxidative passerini three-component reaction of alcohols. ChemCatChem. https://doi.org/10.1002/cctc.201700169 View ArticleGoogle Scholar
- Ghorbani-Vaghei R, Davood A, Daliran S, Oveisi AR (2016) The UiO-66-SO3H metal-organic framework as a green catalyst for the facile synthesis of dihydro-2-oxypyrrole derivatives. RSC Adv 6(35):29182–29189View ArticleGoogle Scholar
- Katz MJ, Brown ZJ, Colon YJ, Siu PW, Scheidt KA, Snurr RQ et al (2013) A facile synthesis of UiO-66, UiO-67 and their derivatives. Chem Commun 49(82):9449–9451View ArticleGoogle Scholar
- Cavka JH, Jakobsen S, Olsbye U, Guillou N, Lamberti C, Bordiga S et al (2008) A New zirconium inorganic building brick forming metal organic frameworks with exceptional stability. J Am Chem Soc 130:13850–13851View ArticlePubMedGoogle Scholar
- Schaate A, Roy P, Godt A, Lippke J, Waltz F, Wiebcke M et al (2011) Modulated synthesis of Zr-based metal-organic frameworks: from nano to single crystals. Chem Eur J 17(24):6643–6651View ArticlePubMedGoogle Scholar
- Queiroz RHC, Bertucci C, Malfará WR, Dreossi SAC, Chaves AR, Valério DAR et al (2008) Quantification of carbamazepine, carbamazepine-10, 11-epoxide, phenytoin and phenobarbital in plasma samples by stir bar-sorptive extraction and liquid chromatography. J Pharm Biomed Anal 48(2):428–434View ArticlePubMedGoogle Scholar
- Zhang J, Liu D, Meng X, Shi Y, Wang R, Xiao D et al (2017) Solid phase extraction based on porous magnetic graphene oxide/β-cyclodextrine composite coupled with high performance liquid chromatography for determination of antiepileptic drugs in plasma samples. J Chromatogr A 1524:49–56View ArticlePubMedGoogle Scholar
- Yu Y, Wu L (2013) Application of graphene for the analysis of pharmaceuticals and personal care products in wastewater. Anal Bioanal Chem 405(14):4913–4919View ArticlePubMedGoogle Scholar
- Ghoraba Z, Aibaghi B, Soleymanpour A (2017) Application of cation-modified sulfur nanoparticles as an efficient sorbent for separation and preconcentration of carbamazepine in biological and pharmaceutical samples prior to its determination by high-performance liquid chromatography. J Chromatogr B 1063:245–252View ArticleGoogle Scholar
- Mandrioli R, Albani F, Casamenti G, Sabbioni C, Raggi MA (2001) Simultaneous high-performance liquid chromatography determination of carbamazepine and five of its metabolites in plasma of epileptic patients. J Chromatogr B Biomed Sci Appl 762(2):109–116View ArticlePubMedGoogle Scholar