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Comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry combined with solid phase microextraction as a powerful tool for quantification of ethyl carbamate in fortified wines. The case study of Madeira wine

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An analytical methodology based on headspace solid phase microextraction (HS-SPME) combined with comprehensive two-dimensional gas chromatography—time-of-flight mass spectrometry (GC×GC–ToFMS) was developed for the identification and quantification
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  Comprehensive two-dimensional gas chromatography time-of- fl ightmass spectrometry (GC × GC/TOFMS) for the analysis of volatilecompounds in  Piper regnellii  (Miq.) C. DC. essential oils ☆ Anaí L. dos Santos a , Allan dos S. Polidoro a , Jaderson K. Schneider a , Michele E. da Cunha a , Caroline Saucier a ,Rosangela A. Jacques a , Cláudia A.L. Cardoso a , Jonas S. Mota b , Elina B. Caramão a,b,c, ⁎ a UFRGS, Instituto de Química, ZIP 91501-970, Porto Alegre, RS, Brazil b UEMS, Instituto de Química, ZIP 79804-970, Dourados, MS, Brazil c INCT-E&A, Instituto Nacional de Ciência e Tecnologia em Energia e Meio Ambiente, Salvador, BA, Brazil a b s t r a c ta r t i c l e i n f o  Article history: Received 21 December 2013Received in revised form 1 July 2014Accepted 10 July 2014Available online 17 July 2014 Keywords: Essential oil Piper regnellii  (Miq.) C. DCGC× GC/TOFMSLPTRI Thisworkcombinesthe analytical capability of GC× GC/TOFMS, theuse of retention indicesand adequate soft-ware tools for the study of essential oils of   Piper regnellii  (Miq.) C. DC. (pariparoba) growing wild in  “ cerrado ” landscape, Central-West region, Brazil. The leaves, stems and  fl owers of   P. regnellii  generated essential oils with163, 119 and 110 compounds tentatively identi fi ed, respectively. The major compounds in each essential oilwere approximately the same, except dill apiole, which was concentrated more highly in the stems. The majorcompounds were: myrcene, anethole  E   and bicyclogermacrene (22%, 19% and 5%, respectively) in leaves,anethole  E  , dill apiole and myrcene (20%, 19% and 16%, respectively) in stems and anethole  E  , myrcene andbicyclogermacrene (24%, 18% and 9%, respectively) in fl owers. This is the fi rst time that this plant was analyzedbyGC× GC/TOFMSandthistechniqueallowsidenti fi cationofahighernumberofcompoundswhencomparedtotraditional one-dimensional chromatography.© 2014 Elsevier B.V. All rights reserved. 1. Introduction The genera  Piper   and  Peperomia are the largestand themostknownof the family Piperaceae [1]. The leaves of various  Piper   species weretypically aromatic or had a pungent smell, providing essential oilswith commercial importance for the fragrance and pharmaceuticalindustries [2]. Piper regnellii  (Miq.) C. DC. is a herbaceous plant found in tropicaland subtropical regions of the world [3], popularly known as “ pariparoba ” . It is a species belonging to the  Piper   genus employed infolk medicine, the leaves being used in the form of crude extracts,infusions and plasters in the treatment of wounds, swellings and skinirritations [4].Previousworksperformedwith P.regnellii leavesextractreporteditsantimicrobial [5] and anticancer activity [6]. The essential oils of the leaves showed activity against  Staphylococcus aureus  and  Candidaalbicans [7]andanalgesicactivity[8].The P.regnellii essentialoilcompo-sition wascommonly analyzed by GC/qMS [7 – 10]. The results reportedthat monoterpenes and sesquiterpenes were the principal compoundsin these essential oils studied.The volatility and polarity of essential oil components indicate thecapillary gas chromatography as being the technique of election fortheir analysis, because essential oils in general are complex mixturesof components with similar physicochemical characteristics [11]. How-ever, the satisfactory separation of an extremely complex sample re-quires a higher peak capacity, being indicated in this case, for the useof comprehensive two-dimensional gas chromatography (GC × GC).This is a relatively new technique idealized by Liu and Phillips [12]and in recent years has been largely applied to petrochemical samples.The GC × GC has the advantage of increasing the resolution andsensitivityduetothere-concentrationofthefractionthroughthemod-ulationprocess, allowingfor thedetectionof compounds in trace levelsand separation of related compounds in the second dimension [13].GC × GC, in particular when combined with MS is the most powerfulseparation system now available. The separation power of GC × GC isevidentwhencomplexessentialoilsareanalyzed[11].Resultsofstudiesthat used GC × GC with time of   fl ight mass spectrometry detector(GC × GC/TOFMS) for the analysis of essential oils [14 – 17] showed animportant improvement in the characterization of these samples.Anotherimportanttoolfortheidenti fi cationofessentialoilcompoundsare Retention Indices that were developed srcinally by Kovatz [18] forisothermal analysis and modi fi ed by Van den Dool and Kratz [19] for Microchemical Journal 118 (2015) 242 – 251 ☆  Paper presented at the Brazilian Congress on Analytical Chemistry. ⁎  Corresponding author at: UFRGS, Instituto de Química, ZIP 91501-970, Porto Alegre,RS, Brazil. Tel./fax: +55 51 33087213. E-mail address:  elina@ufrgs.br (E.B. Caramão). URL:  http://www.inct.cienam.ufba.br (E.B. Caramão).http://dx.doi.org/10.1016/j.microc.2014.07.0070026-265X/© 2014 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Microchemical Journal  journal homepage: www.elsevier.com/locate/microc  linear temperature programmed analysis. Interestingly, the mostcommonly used is the last one named  Low Temperature Programmed-Retention Index  (LTPRI) [20], which is calculated by the equation: LTPRI   ¼  100 n  þ 100  R T i ð Þ − R T n ð Þ R T n þ 1 ð Þ − R T n ð Þ ! In the present work, GC/qMS and GC × GC/TOFMS were employedto investigate the essential oil composition from stems, leaves and fl owers of   Piper regnellii  (Miq.) C. DC. Linear retention indices werealso used to con fi rm peak assignment. The knowledge of the essentialoils composition may be useful to clarify the employment of this plantin folk medicine. The analysis of different parts of the same plant wasintended to determine if there is a differential distribution of the com-pounds in the plant tissues, potentially indicating a selective use formedicinal purposes. 2. Experimental  2.1. Materials The parts (leaves,  fl owers and stems) of the  Piper regnellii  (Miq.)C.DC. were collected in March of the 2012 in Dourados-MS/Brazil(22°12 ’ 37.7 ”  S; 54°55 ’ 03.2 ”  W, 490 m above sea level), and identi fi edby Prof. Elsie Franklin Guimarães (Botanical Garden of Rio de Janeiro,RJ,Brazil).Thevoucherspecimen Piper regnellii (KATO242)wasdepos-ited in the Herbarium of Botanical Garden of Rio de Janeiro, RJ/Brazil.All solvents and reference standards (linear alkanes) used werechromatographic grade (JT Baker and Sigma Aldrich).  2.2. Isolation of essential oils Eachessentialoilwasisolatedfrom200goffreshpartsof  P.regnellii (leaves, fl owers and stems) byhydrodistillationusinga Clevenger-typeapparatus,accordingtotheBrazilianOf  fi cialPharmacopoeiaV [21].Theessential oils were recovered, dried with anhydrous sodium sulfate,transferred to dark vials and stored at − 4 °C for further analysis. Theplant essential oils (1000 mg) were diluted in n-hexane (1 mL) beforegas chromatographic analysis.  2.3. GC/qMS analysis The essential oils were analyzed by GC/qMS (Shimadzu QP2010plus, Shimadzu, Tokyo, Japan) equipped with an AOC20i autoinjectorsplit/splitless injector. The chromatographic separation was performedonaOV-5capillarycolumn(methylsiliconwith5%phenylgroupswith60m×0.25mmid×0.10 μ  m fi lmthickness,AgilentTechnologies –  J&WScienti fi c,PaloAlto,CA,USA)underthefollowingconditions:carriergashelium (99.999%, Linde Gases, Porto Alegre, RS, Brazil) at a  fl ow rate of 0.91 mL/min; 1  μ  L of injection volume using a split ratio of 1:50, andheating from 50 °C to 250 °C at 3 °C/min. The injector, transfer lineand detector temperature used were maintained at 250 °C. The MSscan parameters included electron impact ionization voltage at 70 eV,a mass range from 50 to 500 Da and a scan interval of 0.5 s. The GCMSsolution software 2.6 (Shimadzu, Japan) was used in the analysis of data and peaks were considered identi fi ed only when their spectra co-incided in more than 80% with the equipment library. Temperature-programmed retention indices [19] were calculated using a mixture of normal paraf  fi n (C 6 – C 30 ) as external references. The tentative identi fi -cation used the spectral library database NIST-05.  2.4. GC × GC/TOFMS analysis GC × GC analysis was carried out in a gas chromatograph 6890NAgilent with a LECO Pegasus IV time-of- fl ight mass spectrometric(TOFMS) system (St. Joseph, MI, USA). Electron impact (EI) ionizationenergy was 70 eV, mass acquisition was performed in the range from50to500Da,at45Hzanddetectorvoltagewas1620V.Ionsource,trans-ferlineandinjectorwerekeptat250 °C.AllsampleswereintroducedintotheGC×GCinletsystembyusinganautosamplerCombi-Pal(CTCAnalyt-ics, Carrboro, NC, USA), using split mode with a ratio of 1:50 and carriergas helium (99.999%, Linde Gases, Porto Alegre, RS, Brazil) at a  fl owrate of 1.0 mL/min. A conventional column set was employed: DB-5 (5%phenyl – 95% dimethylpolysiloxane) with 60 m length, 0.25 mm of inter-nal diameter, and 0.10  μ  m of   fi lm thickness in the  fi rst dimension and aDB-17 ms (50% phenyl – 50% dimethylpolysiloxane) with 2.15 m length,0.18mmofinternaldiameterand0.18 μ  mof  fi lmthickness.Bothcolumnswere also acquired from Agilent Technologies –  J&W Scienti fi c (Palo Alto,CA, USA). The temperature program of the  fi rst column started at 50 °Cfor5min,heatingat3 °C/mintill230 °C.Thesecondcolumntemperaturewas maintained 10 °C above the temperature of the fi rst column. Modu-lation period was 10 s and Hot pulse was 20% of modulation period.ChromaTOFsoftwareversion3.32wasemployedfordataprocessingof the total ion current chromatogram (TIC), including tools such aspeak  fi nder and mass spectra deconvolution. Data processing was per-formed using a signal to noise ratio equal to three. The criterion foraccepting a detected compound was a minimum of 80% similaritywith the library. Linear Temperature Programmed Retention Indices(LTPRIs) [19] were calculated using a mixture of normal paraf  fi n(C 6 – C 30 ) as external references. The tentative identi fi cation used thespectral library database NIST-05. 3. Results and discussion The weight percentage yields (w/w) of essential oils obtained fromleaves,  fl owers and stems of   P. regnellii  by hydrodistillation were 0.3,0.4 and 0.2, respectively. The essential oils were  fi rstly analyzed byGC/qMS and further analyzed by GC × GC/TOFMS. Figs. 1, 2 and 3show the 1D-GC/qMS chromatogram and the 2D color diagram(GC × GC/TOFMS) for the essential oil from leaves, stems and  fl owersof   P. regnellii .The compounds were tentatively identi fi ed with a combination of the mass spectral similarity and LTPRI calculated using the Van denDoll and Kratz equation [19].TheretentiontimesinGC/qMS,determinedfromthreeindependentexperiments, showed a coef  fi cient of variation less than 2%.The 1D-GC chromatograms show a complex chromatographic pro fi lewiththepresenceofco-elutions,ascanbeseeninFig.1a.Acomparisonof the three essential oils pro fi les shows a similar composition, althoughwith little quantitative differences. The list of identi fi ed compounds byGC/qMSissummarizedinTable1.Inleavesand fl owersoils,sixtyonevol-atilecompoundsweretentativelyidenti fi edandsixtyfourinstemsoil,in-cluding monoterpenes, oxygenated monoterpenes, sesquiterpenes,oxygenated sesquiterpenes, phenylpropanoids and other compounds(aldehydes,alcohols,andesters).Themaincharacteristicsoftheseessen-tialoilswerethepredominanceofphenylpropanoids.WhenGC/qMSwasused, seventy- fi ve different compounds were identi fi ed in the threeessential oils studied. The essential oil of leaves and  fl owers showedmyrcene and anethole  E   as main constituents, while the major compo-nents in the stems essential oil were dill apiole and myrcene. Thereare few studies about the essential oil composition of   Piper regnellii .Constantin et al. [7], Mesquita et al. [9] and Morandim-Giannetti et al. [10] analyzed the essential oil of   Piper regnellii  leaves by conventionalgas chromatography. They reported that monoterpenes and sesquiter-penes were considered as the principal constituents. But differing fromthe present work, no phenylpropanoid was identi fi ed in these studies.This class of compounds, found here in a large concentration, can proba-bly be used as marker for this plant from  “ cerrado ” , having been foundin the essential oil from leaves, as well as from stems and fl owers.However, many peaks remained unassigned, due to extensive com-poundsoverlapping.Thus,inordertoobtainamorecompletechemical 243  A.L. dos Santos et al. / Microchemical Journal 118 (2015) 242 –  251  Fig. 1.  Chromatographic analysis of the essential oil from leaves of   Piper regnellii :  (a)  total ion chromatogram (GC/qMS) and  (b)  2D Color Diagram (GC × GC/TOFMS). Fig. 2.  Chromatographic analysis of the essential oil from stems of   Piper regnellii :  (a)  total ion chromatogram (GC/qMS) and  (b)  2D Color Diagram (GC × GC/TOFMS).244  A.L. dos Santos et al. / Microchemical Journal 118 (2015) 242 –  251  Fig. 3.  Chromatographic analysis of the essential oil from  fl owers of   Piper regnellii :  (a)  total ion chromatogram (GC/qMS) and  (b)  2D Color Diagram (GC × GC/TOFMS).  Table 1 Peak identi fi cation of compounds in essential oils from  Piper regnellii  using GC/qMS.No. Compound LTPRI  lit  Leaves Stems Flowerst R   RI b area % t R   RI b area % t R   RI b area %1 Hexenal 2E 846 9.07 852 0.49 n.i. n.i. n.i. n.i. n.i. n.i.2 Hexenol 3Z 850 9.21 856 0.20 n.i. n.i. n.i. n.i. n.i. n.i.3 Heptanal 901 n.i. n.i. n.i. n.i. n.i. n.i. 10.87 904 0.144 Thujene alpha 924 11.86 925 0.08 11.85 925 0.03 11.86 925 0.055 Pinene alpha 932 12.13 931 0.62 12.13 931 0.39 12.13 931 0.466 Camphene 946 12.78 945 0.54 12.78 945 0.45 12.79 945 0.367 Sabinene 969 13.98 971 0.28 13.98 971 0.05 13.98 971 0.198 Pinene beta 974 14.09 974 0.13 14.09 974 0.14 14.09 974 0.199 Myrcene 988 14.90 991 21.97 14.89 991 14.9 14.89 991 23.0410 Phellandrene alpha 1002 15.45 1003 0.22 15.45 1003 0.17 15.45 1003 0.1811 p-cimeno 1020 16.45 1023 0.16 16.45 1023 0.10 16.45 1023 0.0912 Sylvestrene 1025 16.65 1027 1.44 16.65 1027 1.06 16.65 1027 1.3613 Cineole 1,8 1026 16.80 1030 0.16 16.79 1030 0.38 16.78 1030 0.6114 Ocimene (E)-beta 1044 n.i. n.i. n.i. 17.71 1048 0.06 n.i. n.i. n.i.15 Terpinene gamma 1054 18.17 1057 0.06 18.17 1057 0.06 n.i. n.i. n.i.16 Linalool 1095 20.30 1100 1.90 20.30 1100 0.88 20.30 1100 0.9317 Nonanal 1100 n.i. n.i. n.i. n.i. n.i. n.i. 20.54 1105 0.5618 Camphor 1141 22.45 1144 0.16 22.45 1144 0.17 n.i. n.i. n.i.19 Benzyl acetate 1157 n.i. n.i. n.i. n.i. n.i. n.i. 23.46 1165 2.0020 Terpinen-4-ol 1174 24.05 1177 0.11 24.05 1177 0.12 24.05 1177 0.0721 Terpinenol alpha 1186 24.73 1190 0.35 24.72 1190 0.43 24.73 1190 0.3122 Anethole Z 1249 27.65 1253 0.07 27.64 1252 0.10 27.64 1252 0.1623 Phenyl ethyl acetate 2 1254 n.i. n.i. n.i. n.i. n.i. n.i. 27.87 1257 0.1724 Anethole E 1282 29.20 1286 16.01 29.19 1286 13.42 29.22 1286 28.2425 Elemene delta 1335 31.48 1337 0.23 31.48 1337 0.09 31.48 1337 0.2326 Cubebene alpha 1345 32.04 1350 0.15 32.03 1350 0.16 32.03 1350 0.1827 Copaene alpha 1374 33.18 1376 0.18 33.17 1376 0.17 33.18 1376 0.3128 Elemene beta 1389 n.i. n.i. n.i. n.i. n.i. n.i. 33.89 1392 0.0829 Gurjunene alpha 1409 34.63 1409 0.14 34.63 1409 0.09 34.63 1409 0.1630 Caryophyllene E 1417 35.04 1419 2.08 35.03 1419 1.11 35.04 1419 1.8231 Gurjunene  β  1431 35.45 1429 0.25 35.44 1429 0.14 35.45 1429 0.34 (continued on next page) 245  A.L. dos Santos et al. / Microchemical Journal 118 (2015) 242 –  251  pro fi le of each sample, the  Piper regenellii  essential oils were alsoanalyzed using the GC × GC/TOFMS technique.Due to its superior performance over the GC/qMS, the GC ×GC/TOFMS allowed an increase in the number of identi fi ed peaks in P. regnellii  essential oils. The GC × GC/TOFMS analyses revealed a com-plex mixture of organic compounds with a similar mass spectral and awide-ranging area,as is exempli fi ed in Fig. 1b. The use of the combina-tionof a low polar 5% phenyl phase in the fi rst dimension with a medi-um polar 50% phenyl phase in the second dimension allowed anef  fi cient use of the available chromatographic space. It was possible toidentify a great number of intense peaks with a medium polarity.More than 200 different compounds were tentatively identi fi ed in thethree essential oil samples, about three times more than by GC/qMS,withsatisfactorylibrarymatchesandthroughtheapplicationofaratherwide±20 LTPRIrange. Theexperimentallinearretentionindices showa good concordance between the identi fi ed compounds and the linearretention indices reported by Adams [22] for 1D-GC. The list of identi- fi ed compounds is shown in Table 2.An example of peak assigned is illustrated in Fig. 4, which shows anexpansionofthe1D-GC(Fig.4a)andGC ×GC (Fig. 4b)fortheessential oil from leaves of   P. regnellii  in the same region.This Figure highlighted the complexity of the  P. regnellii  volatilefraction and the ef  fi ciency of GG × GC for reduce the peak co-elution, obtaining pure MS spectra and increasing peak detectabil-ity [13].The expansion section shows the separation of compounds thatoverlap in the 1D-GC, where the TIC only shows  fi ve de fi ned peaks(three not being identi fi ed). Despite the peaks' apparent symmetry,the use of GG × GC (Fig. 4b) allowed the detection of many otherpeaks, including co-eluted ones (anethole  E   and isobornyl acetate). Itshowsthatinspeci fi ccases,theGC/qMSchromatogrammaybeaninad-equatetool,becausesomepeaksmayappearasasingleone,whereasinreality,therearetwoormoreco-elutedpeaks.Inthesameregion,therearetwopeaksthatarenotconsideredidenti fi edby1D-GC(Fig.4a),dueto a low spectral match given by the library database search and thesame peaks are separated in four new peaks by GG × GC (Fig. 4b).Each of these peaks was shown to be composed of two individualpeaks each of which (peaks 1 & 2 and 7 & 8, Fig. 4b) are now totallyseparated in the second dimension due to the different polarities of thecompounds.Furthermore,theGG×GCincreasedthedetectabilityobtain-edbytheuseofthemodulator[13],ascanbeobservedintheincreaseinthe number of minor compounds highlighted in this zone. These peaks  Table 1  (continued) No. Compound LTPRI  lit  Leaves Stems Flowerst R   RI b area % t R   RI b area % t R   RI b area %32 Aromadendrene 1439 35.86 1439 1.24 35.85 1439 0.82 35.85 1439 1.2133 Guaiene  α  1437 36.04 1443 0.09 36.04 1443 0.05 36.04 1443 0.0834 Humulene alpha 1452 36.46 1454 0.24 36.46 1454 0.21 36.46 1454 0.5135 Aromadendrene allo 1458 36.77 1461 0.43 36.76 1461 0.25 36.77 1461 0.8136 Muurola-4-(14),5-diene cis 1465 36.87 1463 0.06 n.i. n.i. n.i. 36.86 1463 0.1237 Cadina-1(6),4-diene trans 1475 n.i. n.i. n.i. 37.31 1474 0.07 37.31 1474 0.0738 Muurolene gamma 1478 37.44 1477 1.70 37.43 1477 2.08 37.45 1477 7.2339 Germacrene D 1484 37.61 1481 0.39 37.61 1481 0.16 37.61 1481 0.5240 Selinene  β  1489 37.82 1486 0.07 37.82 1486 0.07 37.82 1486 0.0641 Muurola-4-(14),5-diene trans 1493 38.05 1492 0.11 38.04 1492 0.07 38.05 1492 0.1642 Bicyclogermacrene 1500 38.27 1497 9.43 38.25 1497 4.43 38.26 1497 9.6043 Muurolene alpha 1500 38.40 1501 0.55 38.40 1500 0.53 n.i. n.i. n.i.44 Cadinene gamma 1513 38.95 1515 0.41 38.95 1514 0.40 38.95 1515 0.5945 Cubebol 1514 39.02 1516 0.36 39.01 1516 0.35 39.01 1516 0.3846 Myristicin 1517 39.26 1522 1.45 39.26 1522 1.36 n.i. n.i. n.i.47 Cadinene delta 1522 39.33 1524 1.70 39.33 1524 1.73 39.33 1524 2.5448 Cadina-1,4-diene trans 1533 n.i. n.i. n.i. 39.67 1533 0.05 39.67 1533 0.0749 Cadinene alpha 1537 n.i. n.i. n.i. 39.88 1538 0.06 39.88 1538 0.150 Calacorene alpha 1544 n.i. n.i. n.i. 40.09 1544 0.05 n.i. n.i. n.i.51 Elemol 1548 n.i. n.i. n.i. 40.35 1550 0.06 n.i. n.i. n.i.52 Elemicin 1555 40.65 1558 0.11 40.65 1558 0.34 n.i. n.i. n.i.53 Germacrene B 1559 n.i. n.i. n.i. n.i. n.i. n.i. 40.64 1558 0.1654 Nerolidol E 1561 40.91 1565 0.64 40.91 1565 0.32 40.91 1565 0.2055 Palustrol 1567 41.08 1569 0.14 41.05 1568 0.23 41.08 1569 0.1356 Germacrene D-4-ol 1574 41.38 1577 1.23 41.38 1577 0.89 41.37 1576 0.9057 Spathulenol 1577 41.45 1578 0.91 41.45 1578 1.68 41.45 1578 0.6158 Globulol 1590 41.71 1585 0.98 41.71 1585 1.55 41.70 1585 0.8459 Viridi fl orol 1592 42.01 1593 0.29 42 1593 0.42 42.00 1593 0.2960 Guaiol 1600 42.10 1595 0.07 42.09 1595 0.11 n.i. n.i. n.i.61 Ledol 1602 42.43 1604 0.23 42.43 1604 0.37 42.44 1604 0.1962 Curzerenone 1606 n.i. n.i. n.i. 42.53 1606 0.10 n.i. n.i. n.i.63 Eudesmol 5-epi-7-epi- α  1607 42.54 1607 0.07 n.i. n.i. n.i. n.i. n.i. n.i.64 Cubenol 1,10-di-epi 1618 n.i. n.i. n.i. 42.89 1616 0.06 42.88 1616 0.0565 Cedrol epi 1618 42.97 1618 0.13 42.97 1618 0.19 42.97 1618 0.0766 Dill apiole 1620 43.31 1627 14.5 43.34 1628 30.15 43.25 1626 1.3867 Cubenol 1-epi 1627 43.41 1630 0.27 n.i. n.i. n.i. 43.39 1629 0.2768 Eudesmol gamma 1630 43.52 1633 0.26 43.53 1633 0.37 43.51 1633 0.1569 Hinesol 1640 43.78 1640 0.11 43.79 1641 0.18 43.76 1640 0.0870 Muurolol epi- α  1640 43.92 1644 1.42 43.93 1644 2.29 43.90 1643 1.3471 Torreyol 1644 44.07 1648 0.25 44.07 1648 0.51 44.06 1648 0.3072 Eudesmol beta 1649 44.22 1652 1.30 44.23 1652 1.76 44.20 1652 0.6173 Cadinol  α  1652 44.37 1656 1.71 44.38 1656 2.86 44.37 1656 1.2574 Apiole 1677 45.39 1684 0.23 45.39 1684 0.30 n.i. n.i. n.i.75 Junicedranol 1692 45.72 1693 8.93 45.72 1692 7.91 45.71 1692 4.90LTPRI lit :retentionindexesfromtheliterature;t R  :retentiontimeinminutes;RI:calculatedretentionindexes;area%:percentageofareaofthecompoundsrelatedtothetotaloftentativelyidenti fi ed peaks.246  A.L. dos Santos et al. / Microchemical Journal 118 (2015) 242 –  251
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