An Improved Method for BTEX Extraction From
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Analytical Methods Accepted Manuscript This is an Accepted Manuscript, which has been through the Royal Society of Chemistry peer review process and has been accepted for publication. Accepted Manuscripts are published online shortly after acceptance, before technical editing, formatting and proof reading. Using this free service, authors can make their results available to the community, in citable form, before we publish the edited article. We will replace this Accepted Manuscript with the edited and formatted Advance Article as soon as it is available. You can find more information about Accepted Manuscripts in the Information for Authors. Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal’s standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains. www.rsc.org/methods Page 1 of 6 Analytical Methods 1 2 Analytical Methods RSC Publishing 3 4 5 TECHNICAL NOTE 6 7 8 9 An improved method for BTEX extraction from 10 charcoal 11 Cite this: DOI: 10.1039/x0xx00000x 12 13 Raffaele Cucciniello a, Antonio Proto a,*, Federico Rossi a, Nadia 14 b c 15 Marchettini , Oriana Motta Received 00th January 2015, 16 Accepted 00th January 2015 17 Abstract In this paper we propose a simple procedure for the extraction of BTEX (benzene, 18 DOI: 10.1039/x0xx00000x toluene, ethylbenzene and xylenes) from activated charcoal. For this purpose synthetic samples 19 www.rsc.org/ were prepared in laboratory and real samples were collected in a polluted environment using 20 21 passive sampling. The proposed extraction procedure is based on the use of an appositely Manuscript 22 designed soxhlet apparatus which dimensions are as small as the cartridge of the passive 23 samplers, in order to accommodate this latter and permit to use a small amount of solvent. The 24 25 selection of solvent was based on the strong request to substitute carbon disulfide, which is by far 26 the solvent of choice, with less hazardous substance in order to enhance operator protection. 27 Among the solvents tested the best results were found by using dichloromethane that, under 28 29 optimized conditions, led to a complete recovery (>97%) of each analyte (BTEX), both in the 30 synthetic and the real samples. The extracting procedure, with CH 2Cl 2 in the soxhlet last about 20 31 minutes which also results in a reduced operating time. Accepted 32 33 34 35 36 37 38 Introduction Occupational carbon disulfide exposure has been associated with a variety of health effects stimulating some 39 Aromatic hydrocarbons, such as benzene, toluene, ethylbenzene and xylenes (commonly called BTEX) are widely present in the epidemiological researchers to study the potential relationships 40 Methods environment. These compounds can be generally found in between the exposures and neurological, reproductive, 41 gaseous phase and have a key role in the chemistry of the cardiovascular or endocrine dysfunctions as well as eye and 42 troposphere [1,2]. Major sources of aromatics to the urban skin irritations. It has been reported that CS 2 induces diffuse 43 environment include vehicle exhaust (mobile sources), vascular encephalopathy, parkinsonism and peripheral 44 petroleum refining processes, residential heating, waste polyneuropathy [10,11,12]. The US Occupational Safety and 3 45 incineration, coke ,aluminium production (stationary sources) Health Administration (OSHA) indicates for CS 2 12.4 mg/m as 46 and gas fuel stations [3,4,5]. The presence of BTEX in the an 8-h TWA concentration [9]. However Godderis et al. [13] demonstrated that diminished neurobehavioral functions in 47 urban atmosphere has a direct impact on human health because of their carcinogenic and mutagenic potential [6], therefore they workers currently exposed to CS 2 could be detected even if 48 3 need to be monitored periodically. The techniques used for average exposure was as low as ≤ 10 mg/m in a relatively short 49 BTEX monitoring are usually based on their sorption in a tube time (<10 years exposure). Therefore they concluded that the 50 current TLV insufficiently protects against neurological effects (active or passive devices) which is filled with a suitable Analytical 51 sorbing agent, usually activated charcoal, followed by solvent and should be lowered. The request to find less hazardous substituted was first caught 52 desorption with CS 2 and gas chromatographic determination 53 [7,8]. In Italy, at the best of our knowledge, more than 95% of by Bertoni and Ciuchini [14], who investigated on the 54 laboratories of environmental analysis follows this procedure feasibility of substituting CS 2, in the desorption of COV notwithstanding alternative techniques are well known but not sampled on activated charcoal adsorbents, with 55 dichloromethane. CH Cl is a good solvent for GC analysis 56 commonly used, among the others, thermal desorption and 2 2 accelerated solvent extraction [9], because of their high costs. because it has a low boiling point and it doesn’t interfere with 57 other analytes, it has an higher TLV (174 mg/m 3) and is less 58 expensive with respect to CS 2. The results of BTEX extraction 59 60 This journal is © The Royal Society of Chemistry 2015 J. Name ., 2015, 00 , 1-3 | 1 Analytical Methods Page 2 of 6 TECHNICAL NOTE Journal Name 1 with CH 2Cl 2 were not satisfying because the recovery ranged benzene is well separated from that of the solvent and easily 2 from 90% for benzene to 55% for o–xylene. They also tested integrable. 3 different solvents to increase the recovery, without achieving 4 appreciable results. Results 5 This study follows and completes the investigations of Bertoni Apparatus description and extraction conditions 6 and Ciuchini with particular attention to BTEX extraction from Preliminary tests were performed on laboratory prepared 7 passive devices filled with activated charcoal. We screened a samples in order to compare the extraction capacity of selected 8 large number of solvents and CH 2Cl 2 turned out to be the most solvents with carbon disulfide. Synthetic samples were efficient in our experimental conditions. prepared by injecting 1.0 µL of each compound (benzene, 9 Moreover, CH Cl is already used in ultrasonic extraction 10 2 2 toluene, ethyl-benzene, o-xylene, m-xylene and p-xylene) to 10 procedures for BTEX, as recommended by EPA standards g of activated charcoal into a closed chamber. The system was 11 [3,4,5]; this procedure is, in fact, a valid alternative to the kept closed for 24 hours and charcoal was finally removed and 12 employment of CS , though many laboratories still prefer 2 maintained under N 2 atmosphere before analysis. Analyses 13 Soxhlet extraction for its simplicity and low cost of the basic were conducted on 300.0 mg of sample, i.e. the same amount as 14 equipment [15]. in a RING passive sampler, which contains 2.65 µg benzene 15 We performed the extraction of BTEX with CH 2Cl 2 by using a and xylenes and 2.63 µg of toluene and ethyl-benzene. Classic small Soxhlet appositely designed to contain the cartridges of 16 extraction with CS 2 was performed by desorbing the analytes the passive samplers. Recently Soxhlet has been defined as a directly into a glass tube for about 30 minutes with 2 mL of 17 “panacea” in the field of extraction [15], where the 18 solvent (CS 2, low benzene, Sigma Aldrich) following NIOSH development of new technologies has improved its performance method 1501 [8], than the extract was filtered on cellulose 19 opening the door to the utilization in a number of different based filter to remove carbon residues and successively injected 20 approaches. Optimizing the extraction procedure we obtained for the gas chromatographic analysis. The same procedure was 21 quantitative recoveries for each analyte after only eight followed for the other solvents; samples were extracted by Manuscript 22 extraction cycles, that last about 20 minutes. Moreover we using 2 mL of solvent for 30 minutes in a closed glass tube and 23 applied the same procedure to analyze real environmental successively analyzed by GC-FID. The blank was prepared by 24 samples and found data comparable to CS 2 extraction in all using activated charcoal without any treatment. cases. 25 Figure 1 shows the performances of the various solvents tested, where the extraction capacity of each solvent was normalized 26 Experimental with respect to the extraction capacity of CS 2 (100%). 27 Reagents Dichloromethane resulted to give the best results with an 28 The organic solvents used to desorb BTEX from activated efficiency of about 80% with respect to CS 2. Since CH 2Cl 2 is 29 charcoal were pentane, isopropanol, acetonitrile, also suitable for gas chromatographic analysis (low boiling 30 dichloromethane, carbon disulfide, diethylether, chloroform and point and poor response to FID), we used it to test our proposed methylethylketone. Stock standards in all solvents were extraction procedure. 31 Accepted 32 prepared from benzene, toluene, ethylbenzene and o-, m-, p- 33 xylenes. The solutions were kept at 4 °C. All reagents were purchased from Sigma Aldrich at reagent grades and used 34 without any purification. Carbon disulfide was bought form 35 Sigma Aldrich, declared as product with low benzene 36 contamination. 37 38 Samplers and field sampling 39 RING passive samplers filled with activated charcoal (300 mg) were obtained from Aquaria Research srl, Italy. 40 Methods 41 Field sampling was conducted in the city of Salerno (Italy). The measurement site was a commercial area characterized by an 42 elevated traffic density.