Gas chromatography with MS detection was applied for simultaneous determination of six of the most toxic organotin compounds (OTs): monobutyltin, dibutyltin, tributyltin, monophenyltin, diphenyltin, triphenyltin. Headspace single drop microextraction (HS-SDME) in Ionic liquids (ILs) was proposed as Green alternative to the traditional one. Three different ILs ([C8MIM][PF6]; [C6MIM][PF6]) and [C4MIM][PF6]) were evaluated as a collector phase. The first one was found as the most appropriate for a group microextraction of the tested OTs. Analytes were evaporated from the IL microdrop by means of thermal desorption. ILs possess some advantages as an extraction phase in comparison with traditionally used organic solvents. They are more stable during the analytical process and are considered as environmentally friendly compounds. Moreover HS-SDME procedure was performed in a single drop of only 5μl IL. The time needed for the extraction was proved to be only 20 min. Therefore the proposed method could be related to the Green chemistry methods.The current study has been financially supported by: NSF of Bulgaria (Project DO 02-70 (GAMA)); EC 7FP Project 245588 (BioSupport); MICINN of Spain (Project CTQ2008-06730-C02-01) and Regional Government of Valencia (Project ACOMP2010/047). LG thanks Erasmus program and Ministry of Education for her fellowship. IPR also thanks “Caja de Ahorros del Mediterraneo (CAM)” for his Ph.D fellowship

Canals, Antonio

Georgieva, Lora I.

Kmetov, Veselin Y.

Román Falco, Iván

Stefanova, Violeta M.

Repositorio Institucional de la Universidad de Alicante

Journal?of?International?Scientific?Publications:??Ecology? ?Safety,?Volume?6,?Part???ISSN?1313-2563,?Published?at:?http://www.science-journals.eu?316 Published?by?Info?Invest,?Bulgaria,?www.sciencebg.net?IONIC LIQUIDS USED AS A GREEN APPROACH IN HEADSPACE SINGLE DROPMICROEXTRACTION AND GCMS DETERMINATION OF ORGANOTIN COMPOUNDSLora I. Georgieva1, Ivan. P. Román2, Violeta M. Stefanova1, Veselin Y. Kmetov1, Antonio Canals21 Department of Analytical Chemistry and Computer Chemistry, University of Plovdiv “PaisiiHilendarski”, 24 Tzar Assen, Str., 4000 Plovdiv, Bulgaria2 Department of Analytical Chemistry and Food Sciences, and Institute of Materials, Faculty ofScience, University of Alicante, P.O. Box 99, 03080 Alicante, SpainAbstractGas chromatography with MS detection was applied for simultaneous determination of six of the mosttoxic organotin compounds (OTs): monobutyltin, dibutyltin, tributyltin, monophenyltin, diphenyltin,triphenyltin. Headspace single drop microextraction (HS-SDME) in Ionic liquids (ILs) was proposedas Green alternative to the traditional one. Three different ILs ([C8MIM][PF6]; [C6MIM][PF6]) and[C4MIM][PF6]) were evaluated as a collector phase.  The first one was found as the most appropriatefor a group microextraction of the tested OTs. Analytes were evaporated from the IL microdrop bymeans of thermal desorption. ILs possess some advantages as an extraction phase in comparison withtraditionally used organic solvents. They are more stable during the analytical process and areconsidered as environmentally friendly compounds. Moreover HS-SDME procedure was performed ina single drop of only 5µl IL. The  time needed for the extraction was proved to be only 20 min.Therefore the proposed method could be related to the Green chemistry methods.Key words: ionic liquids, organotin compounds, headspace single drop microextraction, greenchemistry.INTRODUCTIONOrganotin compounds (OTs) have been widely used (e.g. Butyltin-BT and Phenyltin-PhT) in the past50 years as active components in different applications. Some of them are: antifouling paints;pesticides formulations; catalysts; additives for thermal and light stabilization in the plastic industry;fungicides; insecticides; water disinfectants; pharmaceuticals and cosmetics [1, 2]. The most extensiveuse of trialkyltins is as biocides in marine antifouling paints in which the active components of theantifouling paint are usually incorporated in a copolymer which induces their steady diffusion intowater:After the awareness of their significant toxicity for mammalian and aquatic organisms in the 1980s,the interest of their speciation increased rapidly. OTs can cause changes in the endocrine system suchas the occurrence of imposex in gastropods, which can lead to sterilization and death of the affectedorganisms [1]. They might exhibit toxic effect on a broad range of non-target organisms. TheirJournal?of?International?Scientific?Publications:??Ecology? ?Safety,?Volume?6,?Part???ISSN?1313-2563,?Published?at:?http://www.science-journals.eu?317 Published?by?Info?Invest,?Bulgaria,?www.sciencebg.net?toxicity, environmental persistence and ability to transfer along the trophyc chains are dependent onthe type, size and number of organic groups attached to the tin atom, so the determination of theirspices is of crucial importance. European Union listed them as priority pollutants. The Directive2000/60/EC (Water Framework Directive, WFD) includes as a priority and hazardous substance thetributyltin compounds among the other substances. Moreover, the Directive 2008/105/EC establishesextent permitted of tributyl compounds (tributyl cation) in inland and other surface waters, expressedas an annual value (0.0002µg/L) or as maximum allowable concentration (0.0015 µg/L).This work aimed to develop a method for determination of six of the most toxic OTs: monobutyltin(MBT), dibutyltin (DBT), tributyltin (TBT), monophenyltin (MPT), diphenyltin (DPT), triphenyltin(TPT). OTs are generally detected by gas chromatography or liquid chromatography (LC) asseparation method in combination with selective techniques such as mass spectrometry (MS), tandemmass spectrometry (MS-MS) or an element selective techniques as an inductively coupled plasma-mass spectrometry [3,  4].  The Gas chromatography (GC) is  more widely used for  OTs analysis  andwas applied in this work for simultaneous determination of six organotin compounds. Due to the verylow content of OTs in the environment preliminary extraction and preconcentration are needed.Nowadays there is a tendency of replacing the traditional liquid-liquid extraction with microextractiontechniques [5, 6].In this work liquid-liquid microextraction was applied as a green alternative of the traditional liquid-liquid extraction.Ionic liquids are considered as more friendly to the environment than traditionally applied organicsolvents so it was interesting to test their applicability as a collector phase for HS SDME procedure.One  problem  is  that  ILs  are  not  compatible  for  direct  introduction  to  GC-MS.  Their  use  in  gaschromatographic analysis could block the chromatographic column. In order to avoid this problem theefficiency of a device for thermal desorption was checked, and thermal desorption program wasoptimized. Procedure of cryofocusing was added for trapping the analytes before introducing them tothe GC-MS[7].  Such technique has not been previously applied in the case of OTs determination.2. EXPERIMENTAL:2.1. Reagents and instruments? ?rganotin compounds: monobutyltin (MBT), dibutyltin (DBT), tributyltin (TBT),monophenyltin (MPT), diphenyltin (DPT), triphenyltin (TPT)  and sodium tetraethyl borateNaBEt4  have been obtained  from Aldrich (Steinheim, Germany).? Ionic liquids 3-Methyl-1-octylimidazolium hexafluorophosphate ([C8MIM][PF6]); 1-Hexyl-3-methylimidazolium hexafluorophosphate ([C6MIM][PF6]) and 1-Butyl-3-methylimidazolium hexafluorophosphate ([C4MIM][PF6]) have been obtained from Merck(Damstadt, Germany).A two-tubes concentrically disposed system made up of a Gerstel thermal desorption glass tube (187mm length, 4 mm I.D., 6mm O.D.), a laboratory-cut glass Pyrex tube (20 mm length, 3 mm I.D., 4 mmO.D.) from Corning Incorporated (Corning, NY, USA) and washed glass wool from Panreac(Barcelona, Spain) were used for  desorption of the compounds from the IL droplet (Fig.1).Journal?of?International?Scientific?Publications:??Ecology? ?Safety,?Volume?6,?Part???ISSN?1313-2563,?Published?at:?http://www.science-journals.eu?318 Published?by?Info?Invest,?Bulgaria,?www.sciencebg.net?Fig.1 Thermal desorption deviceA Gerstel TDS 2 thermodesorption system equipped with a Gerstel CIS-4 cooled injection systemprogrammable temperature vaporization inlet from Gerstel (Mülheim an der Ruhr, Germany) was usedto carry out the TD process.An Agilent 6890N gas chromatograph coupled with an Agilent 5973 mass spectrometry detector, bothfrom Agilent Technologies (Palo Alto, CA, USA), were employed for the analytical measurements.The column used was DB-5 (30m x 0.25 mm i.d.) film thickness 0.25µm. Helium was used as carriergass.2.2. Headspace microextraction procedure with in-situ derivatization by NaBEt4In order OTs to be converted into a suitable form for GCMS analysis derivatization by sodiumtetraethyl borate (NaBEt4) was performed.In this procedure 8 ml freshly prepared working standard solution (20 ng ml-1) of each OTs analytewere placed into a vial containing a stir bar. Then 100 µl 1% NaBEt4 (freshly prepared) were added.The derivatization process was held at pH 5 with the help of acetate buffer. The needle of amicrosyringe containing 5µl IL was passed through a valve septum. Thus, a 3-mm piece of PTFE tubewas fitted to the tip of the syringe needle, and the vial finally capped with the valve stopper. Then thesyringe was placed until  its  tip  was 1 cm approximately up to the liquid surface of  the sample.  Theplunger was then depressed and a droplet of IL was formed and exposed to the headspace of thestirring (at 1600 rpm) solution at 45 0C.After extraction, the droplet was retracted into the syringe. Then, the cap was removed from the vialand  the  PTFE tube  was  removed  from the  syringe  tip.  Finally,  the  IL  droplet  was  placed  inside  thecommercial TD glass tube as shown in Fig. 1.2.3 TD-GC-MS conditionsThermal desorption conditions were optimized experimentally. Higher sensitivity and reproducibilityhave been obtained at the followed parameters: the drop was initially conditioned for 0.5 min at 25 0C,after  that  the  temperature  was  increased  to  240 0C  with  ramp  of  60 0C min-1 and held for 5 min(desorption time); helium flow rate was 100 mL min-1. The desorbed compounds were cryofocused inthe cool injection system with liquid nitrogen at -40 0C . Then the collected fraction was rapidly heatedto 250 0C with ramp of 12 0C s-1. This allowed analytes to be transferred to the GC column by the Hegas. Gas chromatographic conditions for separation were set as: the GC oven temperature was set at50 0C for 1min and was increased to 300 0C at 10 0C min-1 and held for 4min.n = 1, 2, 3Journal?of?International?Scientific?Publications:??Ecology? ?Safety,?Volume?6,?Part???ISSN?1313-2563,?Published?at:?http://www.science-journals.eu?319 Published?by?Info?Invest,?Bulgaria,?www.sciencebg.net?The MS detector voltage was set at 1700V. Electron impact ionization was 70 eV ionization energy.The  mass  source  was  set  at  230 0C. The measurements were carried out in selected ion monitoring(SIM) mode.3. RESULTS AND DISCUSSIONThe use of ionic liquids as collector phase for head space single drop microextraction showed to be agood choice for organotin compounds preconcentration. The high viscosity of the tested ILs improvesthe stability of the microdrop and makes the method more robust even using a 5 µl drops. On the otherhand, ILs possess high boiling points and it is not possible to use them for direct injection in GCinstruments. The optimized procedure for thermal desorption  (2.3) and the selected device (Fig. 1)allowed good repeatability for introducing the six analytes into GC-MS instrument.The efficiency of HS-SDME was tested by heating the sample solution (down to the head space) atdifferent temperature: 100, 200, 300, 400, 450, 500 and 800 C. Results obtained by 450 C showed themost suffisticated extraction yeild for all compounds with exeption of TPT - Fig. 2. It was observedthat TPT extraction needs at least 800 C. The phenomena is due to the higher molecular mass andboiling point of triphenyltin compound. On this temperature in comparison to 450., there is quite highlost of extraction efficiency for MPT, TBT and DPT (Fig. 2). Therefore compromise must be donedepending on the analytical task needed. In order to acomplish a group extraction of the all sixanalytes 800 C was prefered.Figure 2 Extraction efficiency at 450C and 800CThe microextraction was tested at different time from 10 and 60 min. It was found that the treatmentlonger that 20 min did not lead to higher extraction efficiency for the six OTs.The organotin compounds were chromatographically separated (Fig.3). The retention times of theethylated organotin derivatives were determined experimentally using model solutions -  Table 1.Journal?of?International?Scientific?Publications:??Ecology? ?Safety,?Volume?6,?Part???ISSN?1313-2563,?Published?at:?http://www.science-journals.eu?320 Published?by?Info?Invest,?Bulgaria,?www.sciencebg.net?Table 1 Retention  times of OTs derivatizated by NaBEt4Analytes MBT(BuSn3+)DBT(Bu2Sn2+)TBT(Bu3Sn+)MPT(PhSn3+)DPT(Ph2Sn2+)TPT(Ph3Sn+)Ethylatedderivatives BuSnEt3 Bu2SnEt2 Bu3SnEt PhSnEt3 Ph2SnEt2 Ph3SnEtRetentiontime, min 9.7 11.9 13.8 13.2 15.1 22.1Figure 3 Chromatogram of ethylated OTsThe suitability of the Ionic liquids to be used as collector phase for HS-SDME was compared by theextraction yield obtained for the three ILs tested. Fig. 4 represents the results for 3-Methyl-1-octylimidazolium hexafluorophosphate ([C8MIM][PF6]); 1-Hexyl-3-methylimidazoliumhexafluorophosphate ([C6MIM][PF6]) and 1-Butyl-3-methylimidazolium hexafluorophosphate([C4MIM][PF6]) respectively. It was found that only 1-octylimidazolium hexafluorophosphate has theability to extract all six OTs analytes. Moreover with an exeption of MPT is gives greater extractionyields for all the rest organotin compounds tested. Therefore the [C8MIM][PF6] was appointed as thebest choice for the method created.Journal?of?International?Scientific?Publications:??Ecology? ?Safety,?Volume?6,?Part???ISSN?1313-2563,?Published?at:?http://www.science-journals.eu?321 Published?by?Info?Invest,?Bulgaria,?www.sciencebg.net?4. CONCLUSIONSThe combination of head space microextraction with ionic liquids with GC-MS was proved to beapplicable for simultaneous determination of butyl- and phenyltin compounds. Results from evaluatedthree ionic liquids shown that  the extraction with 1-octylimidazolium hexafluorophosphate givesgreater yield than the others two ILs studied. The device for thermal desorption and cryofocusing wassuccessfully applied for introducing organotin compounds from IL into GC-MS instrument.The small volume (5µl) of IL consumed, the replacement of the classical organic solvents with moreenvironmentally friendly compounds, as well as the possibility for group extraction of six organotincompounds refers the suggested method as relevant to the Green Chemistry principles.AcknowledgementsThe current study has been financially supported by: NSF of Bulgaria (Project DO 02-70 (GAMA));EC 7FP Project 245588 (BioSupport); MICINN of Spain (Project CTQ2008-06730-C02-01) andRegional Government of Valencia (Project ACOMP2010/047). LG thanks Erasmus program andMinistry of Education for her fellowship. IPR also thanks “Caja de Ahorros del Mediterraneo (CAM)”for his Ph.D fellowship.REFERENCES1. De Carvalho Oliveira, R. and R. E. Santelli (2010). "Occurrence and chemical speciationanalysis of organotin compounds in the environment: A review." Talanta 82(1): 9-24.2. Blanca, A.-L. (2008). "Environmental levels, toxicity and human exposure to tributyltin(TBT)-contaminated marine environment. A review." Environment International 34(2): 292-308.3. Zachariadis, G. A. and E. Rosenberg (2009). "Determination of butyl- and phenyltincompounds in human urine by HS-SPME after derivatization with tetraethylborate and010203040506070MBT DBT MPT TBT DPT TPTPeakArea(x10-6)[C4MIM][PF6] [C6MIM][PF6] [C8MIM][PF6]Fig. 4  Extraction yield of ethylated OTs obtained by the evaluated ILsJournal?of?International?Scientific?Publications:??Ecology? ?Safety,?Volume?6,?Part???ISSN?1313-2563,?Published?at:?http://www.science-journals.eu?322 Published?by?Info?Invest,?Bulgaria,?www.sciencebg.net?subsequent determination by capillary GC with microwave-induced plasma atomic emissionand mass spectrometric detection." Talanta 78(2): 570-576.4. Zachariadis, G. A. and E. Rosenberg (2009). "Speciation of organotin compounds in urine byGC–MIP-AED and GC–MS after ethylation and liquid–liquid extraction." Journal ofChromatography B 877(11–12): 1140-1144.5. Pena-Pereira, F., I. Lavilla, et al. (2010). "Liquid-phase microextraction techniques within theframework of green chemistry." TrAC Trends in Analytical Chemistry 29(7): 617-628.6. Campillo, N., P. Viñas, et al. (2012). "Solid-phase microextraction followed by gaschromatography for the speciation of organotin compounds in honey and wine samples: Acomparison of atomic emission and mass spectrometry detectors." Journal of FoodComposition and Analysis 25(1): 66-73.7. Chisvert, A., I. P. Román, et al. (2009). "Simple and commercial readily-available approachfor the direct use of ionic liquid-based single-drop microextraction prior to gaschromatography: Determination of chlorobenzenes in real water samples as model analyticalapplication." Journal of Chromatography A 1216(9): 1290-1295.

Ionic liquids used as a green approach in headspace single drop microextraction and GCMS determination of organotin compounds

Abstract

Similar works

Full text

Available Versions

Repositorio Institucional de la Universidad de Alicante