Determination of Ibuprofen Drug in Aqueous Environmental Samples by Gas Chromatography mass Spectrometry without Derivatization

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1 Columbia International Publishing American Journal of Modern Chromatography (2014) Vol. 1 No. 1 pp Research Article Determination of Ibuprofen Drug in Aqueous Environmental Samples by Gas Chromatography mass Spectrometry without Derivatization Tahira Qureshi 1, * Najma Memon 1, Saima Q. Memon 2, and Huma Shaikh 1 Received 10 April 2014; Published online 14 June 2014 The author(s) Published with open access at Abstract Ibuprofen (IBP) is one of the most used active pharmaceutical ingredients globally. Due to its extensive use and resistance to biodegradation it is considered as environmental pollutant and included in the list of pharmaceutically active compounds (PhACs). The objective of this work was to develop the method for the identification and quantification of IBP from water samples without derivatization using gas chromatography mass spectrometry based on the sublimation property of this class of drugs. Solid-phase extraction (SPE) was used for clean-up and enrichment of samples. Under optimum conditions, 1.0 µl of sample in dichloromethane was injected onto GC-MS equipped with HP-5 MS column. The instrumental linear calibration range for IBP was found between 0.8 to 70 µg ml -1. However, the LOD of 0.8 ng ml -1 and LOQ of 2.6 ng ml -1 were achieved after pre-concentration. The method was applied to determine IBP in synthetic, hospital and municipal wastewaters and river water. It may be concluded that GC-MS is useful tool for quick identification and determination of IBP in aqueous environmental samples. Keywords: Ibuprofen; Wastewater; Solid phase extraction; Gas chromatography-mass spectrometry 1. Introduction IBP is non-steroidal anti-inflammatory drug with good analgesic, anti-inflammatory and antipyretic effects used in enormous amount worldwide. IBP s pain killing effect takes place almost immediately after a suitable dosage is administrated while its anti inflammatory effect takes a little longer time (Gonzalez-Rey & Bebianno, 2012).IBP is alkyl benzene with a carboxylic acid functional group with pka 2.48 and solubility of 21 mg L -1 ( Scheytt et al., 2005). *Corresponding najmamemon@gmail.com 1 National Centre of Excellence in Analytical Chemistry, University of Sindh, Jamshoro, Sindh, Pakistan 2 Dr.M.A.Kazi Institute of Chemistry, University of Sindh, Jamshoro, Pakistan. 45

2 A lot of kilotons of IBP are produced worldwide each year, part of which is disposed off to the effluents also it is excreted by patients. Even though possible environmental problems may root by the use of IBP, its consumption is unlikely to be restricted since it is beneficial to humankind (Löffer & Ternes,2003; Weigel et al., 2004; Hamoudová & Pospíšilová, 2006; Bhandari & Venables, 2001; Ferrando-Climent et al., 2012). A number of reports have confirmed the presence of the IBP, in effluents of wastewater treatment plants (WTPs). Concentrations of IBP in the environment are reported between 10 ng L -1 to 169 μg L -1. Despite of lower concentrations in aquatic systems, it may appear as the potential danger for living beings (Sharma & Mishra, 2006; Zhang et al., 2011). IBP is most commonly determined through chromatographic techniques coupled to mass detection after suitable sample clean up. Various solid-phase extraction (SPE) methods combined with GC MS and GC MS MS (Azzouz & Ballesteros, 2012) or LC MS techniques with electrospray ionisation (LC ESI MS) and LC MS MS have been developed for identification and quantitation of IBP (Lee 2005; Costi et al., 2008). Liquid and gas chromatography coupled with MS detection are competitive techniques where gas chromatography is preferred over liquid chromatography for ease of operation, availability of instrument to most of laboratories and MS libraries for identification of unknown compounds. GC- MS methods so far reported for acidic pharmaceutical residues require derivatization where diazomethane is the most commonly used derivatization reagent (Öllers et al., 2001). However toxicity, carcinogenicity and explosiveness of this derivatization agent, propose the development of alternative methods that are free from toxic agent. We are reporting here a simple GC-MS method as an alternative to LC-MS for identification and quantification of IBP. No derivatization is needed as IBP sublimes from dichloromethane solution and is taken to detector. Selectivity is improved by cleaning up water samples using solid-phase extraction and using selected ion monitoring (SIM) mode in MS. Method is systematically validated for various instrumental and chemical parameters. 2. Materials and Methods 2.1 Reagents IBP was purchased from Sigma Aldrich (St.Louis, MO, USA). Dichloromethane and methanol were purchased from Fischer Scientific (UK). Milli Q water was obtained from Elga water system, 18 Ω (UK). 2.2 Chromatographic conditions A system consisting of an Agilent (USA) gas chromatograph model 6890, autosampler model 7683, and mass selective detector model 5973 was used for the GC-MS analysis in this work. Chromatographic separation of IBP was achieved by a HP5 MS (30 m, 0.25 mm I.D., 0.25 µm thickness) column using the temperature program as initial temperature, 100 C, with 1 minute hold, oven temperature ramps at 10 C min -1 from 100 to 300 C, with a 10 minute final hold. The injection port temperature was 300 C and helium was used as carrier gas at constant flow rate of 7.7 ml min -1. Mass detector was set at 350 C. Samples of 1 µl aliquots were injected in the splitless 46

3 mode with a 1 min hold of injection. Electron-impact ionization mass spectrometry (EI-MS) with 70 ev was used for the detection of ibuprofen. Full-scan mass spectra were obtained over a range of m/z Selected ion monitoring (SIM) was employed for the quantitative analyses of the target compound s fragment ions m/z of 206, 163, 161,119 and 91 that are characteristic fragment ions of IBP (Zayed et al., 2012). 3. Preparation of Solutions and Samples 3.1 Standard solution Stock solutions of IBP (1000 µg ml -1 ) were prepared in dichloromethane and successive dilutions were done for further studies and calibration plot. However, IBP solution of 10 µg ml -1 was also prepared in methanol while optimization of GC-MS method. 3.2 Synthetic wastewater Synthetic wastewater was prepared by mixing various nutrients, minerals, etc. reported composition was employed (Boeijie, 1999) Sample Preparation Water samples were collected from River Indus at Jamshoro and from local hospitals of Hyderabad, Pakistan. After immediate transfer to laboratory, all samples were adjusted to ph 2.5 with HCl (37%) and were vacuum filtered using 0.45 µm filter paper. Samples collection, filtration and enrichment were completed on the same day to avoid any loss of IBP in analysis Solid-phase extraction The solid-phase extraction was performed on Visiprep Solid-Phase extraction system fitted with mini vacuum pump (Supleco, Bellefonte, PA, USA). Oasis HLB cartridges 60 mg 3 ml -1 (Waters, Milford, USA). Extraction of IBP was performed using 100 ml of aqueous samples as reported by Quintana and Reemtsma (2004). After pre-concentration the volume was made up to 1mL with dichloromethane prior to GC-MS analysis. By this process, samples were pre-concentrated 100 times to its original concentration. 4. Results and Discussion IBP is an acidic drug, soluble in polar solvents and remains in protonated (neutral) form at acidic ph. IBP has high melting and boiling points to be directly analyzed by gas chromatography. However, its sublimation increases as temperature increases (Florence, 2007; Maxwell & Chickos, 2012) thus, the vapors of sublimed IBP in injector ( 300 C) are taken to capillary column and carried to mass detector via carrier gas. Fig. 1 shows the full scan mass spectrum and fragmentation of IBP using electron impact (EI) ionization. For identification of IBP in unknown samples, spectral match with NIST05 library was used whereas optimization and quantification of IBP was carried in selected ion monitoring mode (SIM) using ions 206, 163, 161, 119, and 91 ions (Table 1). Multiple ions were used to enhance the signal thereby the sensitivity of assay. 47

4 Fig. 1. The IBP standard of 10 µg ml -1 ion chromatogram at full scan mode (a) and mass spectra (b). Table 1 IBP fragment ions with m/z. m/z Fragment structure 206 H 3 C O OH O OH H 3 C

5 4.1. Method Optimization To optimize chromatographic determination of IBP different temperature programs were tested. Chromatographic conditions; including mode of injection (split or split less), injector temperature, volume of sample injection, initial and final column temperatures, column temperature rate and carrier gas flow rate were optimized. Injection parameters: IBP standard was prepared in methanol in order to maintain the solvent match to that eluted from SPE, initially. Standard prepared in methanol gave poor signal even for 10 µg ml -1 of IBP; however, signal was significantly increased when standard of same concentration of IBP was prepared in dichloromethane (Fig. 2). This may be due to hydrogen bonding or other polar interactions of methanol with IBP which diminishes entropy, thereby sublimation rate (Aragón et al., 2010). The injector temperature was optimized in the range of 100 to 300 C. Better results were obtained at injector temperature of 300 C. Fig. 2. Response of IBP standard prepared in dichloromethane (a) and methanol (b). Sample volume and injection mode: Using sample volume of 1µL (10 µg ml -1 ) of IBP was injected in split and splitless mode at injector temperature 300 C. No peak was observed using split mode with split ratio of 1:10 even on injecting 3 µl of sample volumes. However, poor signal was observed when same concentration of IBP was injected at split ratio of 1:50. Therefore, splitless mode was studied further (Fig. 3). Volume of injection was optimized from 0.2 to 2 µls where 1 µl in splitless mode provided good signal along with better peak shape, whereas on 0.2 µl no appreciable signal was observed and peak broadening was observed at 2 µl. 49

6 Fig. 3. Response of IBP (10 µg ml -1 ) using 1 µl injection volume, split mode (1:50) (a) and splitless mode (b). Temperature programming: Various initial (100 to 300 C) and final (250 to 350 C) temperatures with ramp rates of 10 to 30 C min -1 were tried to get the IBP peak with total run time of 10 to 30 minutes. Also, the peak intensity and shape were taken in to account in selection of optimum temperature parameters. The suitable parameters were as 100 C initial temperature hold for 1 minute and then temperature increased with rate of 10 C min -1 and reached to 300 C and then held for ten minutes. Detector parameters: Throughout the study, MS detector temperature was set at 350 C. MS was operated at amu in scan mode while in SIM mode targeted ions were 91, 119, 161,163, and 206 m/z. These ions were used for optimization and quantification of IBP. Sample preparation: The solid phase extraction technique was used to pre-concentrate IBP from water samples. The thoroughly optimized method reported by Quintana and Reemtsma (2004) was used for the extraction of IBP via HLB cartridge. Maximum percent recovery ( 80%) was obtained when loaded cartridges were eluted with methanol; however, GC-MS results were best optimized using dichloromethane. Therefore, elution contents were dried under nitrogen stream and again dissolved into dichloromethane. The SPE extraction cartridge was eluted twice with 4 ml of methanol to ensure complete desorption of IBP. Pre-concentration factor of 100 was adopted as reported in method. 4.2 Method Validation The LOD and LOQ for IBP were determined as the lowest absolute amount of analyte detected with signal-to-noise ratios of at least 3:1 and 10:1, respectively, with corrected relative ion intensities and a retention time. LOD and LOQ for IBP were found to be 0.08 µg ml -1 and 0.26 µg ml -1, respectively. Moreover, the samples could be concentrated 100 times, therefore, the LOD and LOQ of 0.8 ng ml -1 and 2.6 ng ml -1 may be assumed, respectively. The linearity of method was determined by the calculation of the regression line using the method of least squares with r 2 = with slope (a) and intercept (b) , the linear range of method was

7 to 70 µg ml -1 analyzed in triplicate in SIM mode (91, 119, 161,163, and 206). The accuracy and precision were investigated at three concentration levels (10, 20 and 50 µg ml -1 ) of IBP in the linear range with five independent replicates on the same day and on three consecutive days (Table 2). Table 2 Accuracy and precision data assay of IBP in Synthetic wastewater. Drug Concentration µg ml -1 Intra-Day* % RSD (±SD) Inter-Day** % RSD(±SD) %Recovery Ibuprofen ± ± ± ± ± ± * Average from five replicate determinations, ** Average from three days determinations 4.2.1Recovery of IBP In order to establish the reliability of the reported method by Quintana and Reemtsma (2004) for extraction of IBP, recovery experiments were carried out. Apparent recoveries, calculated as the ratio of the measured concentration in calibrated levels to the spiked synthetic wastewater (expressed as percentage). For recovery, known amounts of IBP added whose concentration after pre-concentration reached at 10, 20 and 50 µg ml -1 ; the observed recoveries were 80%, 85% and 114%, respectively. All samples were free of co-eluting peaks at the retention time of IBP which provided little chances of positive error in identification of IBP. The selectivity of the method was adequate with minimal matrix effect in the samples. The developed method can achieve 80 to 114 % recovery to detect the IBP in ng ml -1 level after pre-concentration without derivatization. This is the first report on the quantification of IBP without derivatization using GC-MS which offers simple and rapid alternative to lengthy derivatization based procedures (Araujo et al. 2008; Zhang & Lee, 2009; Guitart & Readman, 2010; Ferreira et al., 2011; Noche et al., 2011; Guo & Lee, 2012). Furthermore, current procedure does not involve any additional steps but sublimation of IBP in injector port forms the basis of assay procedure. 4.3 Real water samples The real water samples were analyzed using developed procedure by spiking 100 ml of sample with 100 ng ml -1 of IBP. The samples were also pre-concentrated and analyzed without spiking. The obtained results are shown in Table 3. The presence of IBP found in ng ml -1 level in nearly all of the samples which is higher as compared to rest reported methods, mainly due to inefficient waste treatment plants in locality (Fig. 4). 51

8 Fig. 4. Ion chromatogram of IBP obtained from sample A after SPE unspike (a) and spiked (b). Table 3 Determination of IBP in real water samples followed by SPE. Sample 5. Conclusion Hospital wastewater Conc.(ng ml -1 )(±Std Dev) Unspiked Spiked * sample A 52(±0.12) 162(±0.07) sample B 80(±1.13) 174(±1.02) sample C 55(±0.014) 155(±0.212) sample D 58(±0.04) 149(±0.02) River Water sample E 32(±0.02) 134(±0.03) Municipal wastewater sample F 52(±0.7) 158(±1.4) * Each sample was spiked with 100 ng ml -1 prior to pre-concentration step. The developed GC MS method can be used for determination of the IBP in aqueous samples obtained after pre-concentration. The method is fairly sensitive and very specific in comparison with other methods, e.g. HPLC and GC with classic detection. It is useful for analysis of unknown real water samples. Although, sensitivity of the method was capable of measuring concentrations at µg ml -1 levels but when SPE was used quantification at ng ml -1 levels was possible. The main advantage of the method is the analysis of IBP without derivatization. The developed method was successfully applied to real water samples while the relative recovery percentages obtained for the synthetic wastewater samples was observed as 80%.The IBP is found in ng ml -1 level in nearly all of the samples, as there are no proper regulations of this analgesic and anti-inflammatory drug circulation and inefficient treatment for removal of IBP wastewater streams. Acknowledgements Higher Education Commission of Islamabad, Pakistan for providing funds through Indigenous Fellowship Program batch VII [ PS7-141] 52

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