Simultaneous Determination of Aromatic Amines and Pyridines in Soil

Transcription

1 Simultaneous Determination of Aromatic Amines and Pyridines in Soil Huang Xiongfeng, Liu Lvye, Xu Qun, and Jeffrey Rohrer Thermo Fisher Scientific, Shanghai, People s Republic of China; Thermo Fisher Scientific, Sunnyvale, CA, USA Application Note 4 Key Words Aniline Compounds, Environmental Analysis, Environmental Safety, Acclaim 0 C8 Column, HPLC Goal To develop an efficient high-performance liquid chromatography (HPLC) method for fast and simultaneous determination of -methylpyridine, 3-methylpyridine, m-toluidine, and p-toluidine in soil Introduction Aniline and pyridines are widely used in the polymer, fuel, pesticide, rubber, and pharmaceutical industries. Not only do some of these compounds have a putrid odor, but they are also suspected potential carcinogens and mutagens that can be highly toxic to life. Therefore, the Ministry of Environmental Protection of the People s Republic of China has proposed a provisional guideline concentration of 0. mg/l for pyridine in environmental water. The U.S. Environmental Protection Agency (EPA) lists aniline and -methylaniline in its Health Effects Notebook for Hazardous Air Pollutants. 3 As cities grow larger and become more crowded, some of the factories that use these hazardous compounds are closed, and houses and parks are then built on the vacated land. The soil may be polluted, however, and require treatment before building. Therefore, it is necessary to establish a sensitive, efficient, and simple method for the determination of compounds such as pyridines in soil samples. The most common techniques used for determination of aromatic amine and pyridine compounds in environmental samples are gas chromatography (GC) and HPLC, although capillary zone electrophoresis (CZE) and spectrophotometric methods also have been reported. 0 Because the compounds involved are thermolabile and polar, a derivatization step prior to GC analysis is often required and most such procedures are time consuming and complicated. Therefore, HPLC analysis is a good alternative to GC analysis because derivatization is not needed. Figure shows the structures of four aromatic amine and pyridine compounds that will be simultaneously determined in this study using HPLC. NH NH CH 3 N CH 3 N CH 3 CH3 -Methylpyridine 3-Methylpyridine m-toluidine p-toluidine Figure. Structures of four aromatic amine and pyridine compounds.

2 Equipment, Software, and Consumables Thermo Scientific Dionex UltiMate 3000 Rapid Separation LC (RSLC) system, including: LPG-3400RS Quaternary Pump (P/N ) SRD-3400 Integrated Solvent and Degasser Rack (P/N ) WPS-3000TRS Wellplate Sampler, Thermostatted (P/N ), with 5 μl sample loop (P/N ) TCC-3000RS Thermostatted Column Compartment (P/N ) DAD-3000RS Diode Array Detector (P/N ) with.5 μl flow cell (P/N ) Thermo Scientific Dionex Chromeleon Chromatography Data System (CDS) software, version 7. Thermo Scientific Sorvall ST6 Centrifuge (P/N ) Thermo Scientific Target Nylon Syringe Filters, 0.45 μm, 30 mm (P/N F500-) Reagents and Standards Deionized (DI) water, 8. MΩ-cm resistivity, generated using a Thermo Scientific Barnstead GenPure Pro ultrapure water system (P/N ) Acetonitrile, HPLC Grade (Fisher Scientific P/N AC ) Methanol, 99.8%, HPLC Grade (Fisher Scientific P/N AC ) Ammonium Acetate, Crystalline/HPLC (Fisher Scientific P/N A ) Acetic Acid, Optima LC/MS (Fisher Scientific P/N A3-50) -Methylpyridine, 5GR (Fisher Scientific P/N ) 3-Methylpyridine, >98%, GC (Fisher Scientific P/N ) p-toluidine, 99% (Fisher Scientific P/N AC ) m-toluidine, 99% (Fisher Scientific P/N AC ) Conditions Column: Thermo Scientific Acclaim 0 C8, 3 µm Analytical,. 00 mm (P/N 0599) Eluent: Acetonitrile/ammonium acetate buffer (dissolve 3.85 g of ammonium acetate and 3 g of acetic acid in L of DI water) Gradient: 0 min, 5% acetonitrile; 3.5 min, 80% acetonitrile; min, 5% acetonitrile Flow Rate: 0.4 ml/min Injection Volume: µl (partial-loop injection mode) Temperature: 35 C Detection: UV, 60 nm Preparation of Standard Solutions Stock Standard Mix Dissolve 0. g each of -methylpyridine, 3-methylpyridine, m-toluidine, and p-toluidine in a 00 ml volumetric flask and dilute to volume with methanol. The concentration of each compound will be mg/ml. Working Mixed Standard Solutions For calibration, prepare five working mixed standard solutions with different concentrations by diluting the proper amount of each stock standard solution mix with methanol. The volumes of each solution needed to make the calibration standards are shown in Table. Sample Preparation Soil Sample used in this work was collected from Jinqiao Park in Shanghai, People s Republic of China. Soil Sample, also from Shanghai, was supplied by a real estate developer. Add 0 ml of methanol to g of an air-dried soil sample in a 0 ml centrifuge tube and vortex for min. After ultrasonically extracting the sample at 50 W for 40 min, centrifuge the extract for min at 8000 rpm. Transfer the supernatant to a 0 ml tube and use nitrogen to dry the sample. Add ml methanol to the dried sample. Prior to injection, filter the solution through a 0.45 μm filter. Table. Preparation of working mixed standard solutions. Vol of mg/ml Stock Standard Mix Vol of Methanol Final Vol of Working Mixed Standard Solution Final Concn of Each Calibration Standard

3 To prepare the spiked soil sample, add 5 μl of the mg/ml stock standard mix to g of a soil sample. Prepare the sample as described above. The spike concentrations will be 5 mg/kg for each analyte. Results and Discussion Separation of -Methylpyridine, 3-Methylpyridine, p-toluidine, and m-toluidine Initial experiments showed that when using methonal/ water or acetontrile/water as the mobile phase, it was difficult to separate p- and m-toluidine. Therefore, the addition of a phosphate or acetate buffer to the mobile phase was investigated as a way to achieve the separation. The peak resolution between p- and m-toluidine was.4 when using an acetonitrile/acetate buffer mobile phase. In addition to the baseline separation, the peak asymmetry factors of -methylpyridine, 3-methylpyridine, p-toluidine, and m-toluidine were all in the range of 0.9~.4 better than that yielded when using methanol/acetate, methanol/phosphate, and acetonitrile/phosphate mobile phases. Therefore, an acetonitrile/acetate buffer mobile phase was used in this work. Figure shows a chromatogram of a standard mix of -methylpyridine, 3-methylpyridine, p-toluidine, and m-toluidine under the specified and optimized chromatographic conditions. Method Reproducibility, Linearity, and Detection Limit Method precision was estimated by making nine consecutive µl injections of a calibration standard with a concentration of 0 mg/l for each compound. Retention time and peak area reproducibilities (RSDs) are shown in Table. Retention time RSDs all are <0.% and peak area RSDs all are <.%, demonstrating good short-term precision for this method. 45 mau 0 Figure. Separation of a mixed standard solution. Peaks:. -Methylpyridine 5 mg/l. 3-Methylpyridine 5 3. p-toluidine 5 4. m-toluidine 5 Calibration linearity of -methylpyridine, 3-methylpyridine, p-toluidine, and m-toluidine was investigated by making three consecutive μl injections of the working mixed standard solution prepared at five different concentrations (i.e., 5 total injections). A linearity range of 000 mg/l for these four compounds was observed when plotting concentration versus peak area. Detailed calibration data calculated by Chromeleon CDS software are shown in Table. Five consecutive μl injections of a working mixed standard solution with a concentration of mg/l for each compound were used for estimating the method detection limit (MDL) using a signal-to-noise ratio = 3. The calculated MDLs also are listed in Table Minutes 3 Table. Calibration data and MDLs. Target Analyte Retention Time RSD Peak Area RSD Regression Equation r Range MDL -Methylpyridine A = 0.6c Methylpyridine A = 0.6c p-toluidine A = 0.05c m-toluidine A = 0.037c

4 4 Table 3. Sample analysis results. Soil Sample Analyte Detected Added Spiked Sample Found Recovery (%) -Methylpyridine Methylpyridine Not p-toluidine Detected m-toluidine Analysis of Soil Samples -Methylpyridine, 3-methylpyridine, p-toluidine, and m-toluidine were not found in the soil samples. Figure 3 shows chromatograms of both soil samples and Soil Sample spiked with four aromatic amines and pyridines. To judge method accuracy, three injections of Soil Sample spiked with 5 mg/kg of each of the standards were made. Analysis results are summarized in Table 3. The average recoveries were in the range of 76 0%, demonstrating that this method can achieve good recovery and is suitable for the determination of aromatic amines and pyridines in soil. Conclusion This work uses an ammonium acetate/acetonitrile mobile phase for a rapid, simple, and accurate determination of -methylpyridine, 3-methylpyridine, p-toluidine, and m-toluidine in soil. The separation requires only 6 min and demonstrates good reproducibility and recovery. 45 mau D C B Peaks:. -Methylpyridine. 3-Methylpyridine 3. p-toluidine 4. m-toluidine 0 A Minutes 34 Figure 3. Separation of (A) a blank, (B) Soil Sample, (C) Soil Sample, and (D) Soil Sample spiked with 5 mg/kg of each standard.

5 References. Brede, C.; Skjevrak, I.; Herikstad, H. Determination of Primary Aromatic Amines in Water Food Simulant Using Solid-Phase Analytical Derivatization Followed by Gas Chromatography Coupled with Mass Spectrometry. J. Chromatogr., A 003, 983, GB : Environmental Quality Standards for Surface Water; Ministry of Environmental Protection of the People s Republic of China: Beijing, U.S. Environmental Protection Agency. Health Effects Notebook for Hazardous Air Pollutants. [Online] (accessed Oct 3, 04). 4. Chiang, J.S.; Huang, S.D. Simultaneous Derivatization and Extraction of Anilines in Waste Water with Dispersive Liquid Liquid Microextraction Followed by Gas Chromatography Mass Spectrometric Detection. Talanta 008, 75, Jen, J.F.; Chang, C.T.; Yang, T.C. On-Line Microdialysis High-Performance Liquid Chromatographic Determination of Aniline and -Chloroaniline in Polymer Industrial Wastewater. J. Chromatogr., A 00, 930, Sarafraz-Yazdi, A.; Es haghi, Z. Liquid Liquid Liquid Phase Microextraction of Aromatic Amines in Water Using Crown Ethers by High-Performance Liquid Chromatography with Monolithic Column. Talanta 005, 66, Zhao, L.M.; Zhu, L.Y.; Lee, H.K. Analysis of Aromatic Amines in Water Samples by Liquid Liquid Liquid Microextraction with Hollow Fibers and High-Performance Liquid Chromatography. J. Chromatogr., A 00, 963, Thermo Scientific Application Note 9: Determination of Aniline and Nitroanilines in Environmental and Drinking Waters by On-Line SPE. Sunnyvale, CA, 04. [Online] dam/tfs/atg/cmd/cmd%0documents/application %0&%0Technical%0Notes/Chromatography/ Liquid%0Chromatography/Liquid%0Chromatog- raphy%0accessories/an-9-lc-aniline-nitroanilines- Water-SPE-AN703-EN.pdf (accessed Oct 3, 04). 9. Li, J.; Yuan, Z.B. Separation of Aniline Derivatives by Micellar Electrokinetic Capillary Chromatography. Chin. Chem. Lett. 004, 5, Gu, X.X.; Li, C.Y.; Qi, X.; Zhou, T.Z. Determination of Trace Aniline in Water by a Spectrophotometric Method after Preconcentration on an Organic Solvent-Soluble Membrane Filter. Anal. Lett. 997, 30, 59. Application Note Thermo Fisher Scientific Inc. All rights reserved. All trademarks are the property of Thermo Fisher Scientific and its subsidiaries. This information is presented as an example of the capabilities of Thermo Fisher Scientific products. It is not intended to encourage use of these products in any manners that might infringe the intellectual property rights of others. Specifications, terms and pricing are subject to change. Not all products are available in all countries. Please consult your local sales representative for details. Africa Australia Austria Belgium Brazil Canada China (free call domestic) AN743-EN 076S Denmark Europe-Other Finland France Germany India Italy Japan Korea Latin America Middle East Netherlands New Zealand Norway Russia/CIS Singapore Sweden Switzerland Taiwan UK/Ireland USA