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WO1994022009A2 - Procede et appareil d'analyse de composes organiques volatils - Google Patents

Procede et appareil d'analyse de composes organiques volatils Download PDF

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Publication number
WO1994022009A2
WO1994022009A2 PCT/EP1994/000889 EP9400889W WO9422009A2 WO 1994022009 A2 WO1994022009 A2 WO 1994022009A2 EP 9400889 W EP9400889 W EP 9400889W WO 9422009 A2 WO9422009 A2 WO 9422009A2
Authority
WO
WIPO (PCT)
Prior art keywords
trap
sample
column
equipment according
gas chromatographic
Prior art date
Application number
PCT/EP1994/000889
Other languages
English (en)
Other versions
WO1994022009A3 (fr
Inventor
Fausto Munari
Dimitris Kotzias
Matthew Duane
Original Assignee
Fisons Instruments S.P.A.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Fisons Instruments S.P.A. filed Critical Fisons Instruments S.P.A.
Publication of WO1994022009A2 publication Critical patent/WO1994022009A2/fr
Publication of WO1994022009A3 publication Critical patent/WO1994022009A3/fr

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
    • G01N30/02—Column chromatography
    • G01N30/04—Preparation or injection of sample to be analysed
    • G01N30/06—Preparation
    • G01N30/12—Preparation by evaporation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
    • G01N30/02—Column chromatography
    • G01N2030/022—Column chromatography characterised by the kind of separation mechanism
    • G01N2030/025—Gas chromatography
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
    • G01N30/02—Column chromatography
    • G01N30/04—Preparation or injection of sample to be analysed
    • G01N30/06—Preparation
    • G01N30/12—Preparation by evaporation
    • G01N2030/121—Preparation by evaporation cooling; cold traps
    • G01N2030/122—Preparation by evaporation cooling; cold traps cryogenic focusing
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
    • G01N30/02—Column chromatography
    • G01N30/26—Conditioning of the fluid carrier; Flow patterns
    • G01N30/28—Control of physical parameters of the fluid carrier
    • G01N30/32—Control of physical parameters of the fluid carrier of pressure or speed
    • G01N2030/324—Control of physical parameters of the fluid carrier of pressure or speed speed, flow rate

Definitions

  • the present invention concerns a method and an equipment for the analysis of volatile organic compounds.
  • This method besides not avoiding the loss of volatile compounds during the sample transfer to the trap, also involves problems of reproducibility, since the latter depends on the constancy of the sample flow through the cool trap and said constancy is hardly achievable because of the condensate forming inside the trap itself.
  • first of all moisture is eliminated from the sample, that is passed through a cool trap having considerable size, wherein there is provided a packing of different materials capable of retaining volatile compounds at a temperature of about -20 * C.
  • the compounds are then desorbed by heating and flowing of an inert gas therethrough, and then reconcentrated in a second trap, downstream of the first one, kept at -150 * C.
  • the packing material used in the first trap must be constituted by different layers of materials having different adsorption power, both in order to try to retain volatile compounds that otherwise would not be retained at -20 * C, and not to retain excessively the heaviest substances.
  • the consequence of this structure is that the transfer of the compounds from the first to the second trap must be carried out in backflow mode and possible losses of compounds are avoidable only as a function of the effectiveness of the second trap. Disclosure of the invention
  • An object of the present invention is to solve the aforementioned problems by means of a method and a device for on-line analysis of volatile organic compounds, which is of easy structure and avoids the loss of compounds, simultaneously ensuring a high analysis efficiency and reproducibilit .
  • Said object is achieved by means of the present invention, that concerns a method for the analysis of volatile organic compounds, of the type comprising a sampling and concentration step of a gaseous sample in a trap and a step of heating said trap and transfer the compounds retained therein to a gas chromatographic column, characterized in that during said sampling and concentration step of the sample, this sample is fed to said cool trap at a speed ranging between 50 and 1000 cm/sec .
  • the invention moreover concerns an equipment for the analysis of volatile organic compounds present in a gaseous sample, of the type comprising a trap for the concentration of said volatile compounds, means to feed said sample to the trap and a gas chromatographic device provided with at least a gas chromatographic column for their analysis, characterized in that said trap and said feeding means are sized in such a way to feed said sample to said trap at a speed ranging between 50 and 1000 cm/sec.
  • speed of the sample means the speed that can be substantially considered as the average speed of the sample, achievable by dividing the sample flowrate in ml/min by. the area of the inlet section of the trap 2 and performing the appropriate dimensional adjustments.
  • gases coming out of the trap during the step of concentration of volatile compounds are simultaneously conveyed to the gas chromatographic column and to a purge line having a substantially nil fluidic resistance with respect to that of said column.
  • the trap is of the type that can be cooled and is provided with an ejector for the feeding of the cooling fluid.
  • the method and the equipment according to the invention offer a number of advantages versus the state of the art. It is actually possible to use a single cool trap with reduced sizes, avoiding to desorb and reconcentrate the initially trapped compounds, that are on the contrary directly sent to the column. Furthermore, it has been noticed that part of the water contained in the samples of ambient air is eliminated through the purge line during the initial step of volatile compound concentration in the trap, and that the residual water does not affect the subsequent separation on column and the analysis by means of gas chromatographic detectors or mass spectrometer.
  • a further advantage is provided by the use of a particular trap with ejector for the cooling fluid feeding.
  • This trap is described in the patents US-A-4 ,836,871 and EP-B-201632 to the content of which, when considered included in the present specification, reference is made for further details.
  • the geometry and reduced size of the trap allow to reduce to a minimum (up to about 60 ml/min) the consumption of liquid nitrogen for each analysis and to house the trap inside the gas chromatographic oven together with the column.
  • Said injector allows in fact the injection of liquid samples into the system, thus greatly facilitating the calibration of liquid compounds at ambient temperature (e.g. aromatics) that can be injected in solution, even aqueous solution.
  • the calibration of volatile gaseous compounds is extremely facilitated with the present invention, thanks to the presence of one or more loops for sample loading, and a possibility to directley iniecting with syringe through the injection part of split-splitless injector.
  • figure 1 is a schematic view partially in cross- section of an equipment according to the invention
  • figure 2 is a sectional schematic view of a preferred injector for the equipment according to the invention
  • figure 3 is a cross-sectional and magnified schematic view of a detail of figure 2
  • figures 4 - 6 are schemes of an equipment provided with loading loop during the operative step
  • figures 7 and 8 are schemes of the equipment during its operation in absence of loading loop
  • figure 9 is a scheme of a further embodiment of the invention
  • FIG. 10 is a scheme of another embodiment according to the invention.
  • figures 11 - 14 are analytical diagrams obtained with the equipment according to the invention.
  • the equipment 1 comprises in a known way a cool trap 2 connectable to a source (not shown) of cooling fluid, means for sample feeding and a gas chromatographic device 3 provided with at least a gas chromatographic column 9 for the separation and the analysis of the volatile compounds contained in the sample.
  • the detectors 4 of the gas chromatograph can be for instance of the FID or ECD type or they can consist of a mass spectrometer 5.
  • the means for feeding the sample to the trap, figures 2-4, comprise a line 6, a multi-position valve 15 and an injector of the split-splitless type 7.
  • said means and the trap 2 are sized in such a way that the speed of the sample feeding flow to the trap 2 (namely the speed of the gaseous sample at the trap inlet), during the step of the sampling and sample concentration, ranges between 50 and 1000 cm/sec. It has been surprisingly noticed that these speeds allow to perform the analysis of volatile compounds at a wide range of trap temperatures, according to the type of volatile compounds to be analysed and to the type of packing present (if any) in the trap itself.
  • the speed according to the present invention allows to analyse also samples with high moisture content, even mists, avoiding the risk of obstruction of the trap itself because of the water present in the sample and condensing in the trap.
  • the trap 2, figures 2 and 3 is preferably formed by a pre-column made of silanised fused silica 8 connected upstream to a liner 8a present in the injector 7 and downstream to the gas chromatographic column 9, preferably of the capillary type.
  • the injector 7 is of the split-splitless type as described in the Italian patent application n. MI91A001140 filed by the Applicant, and is provided with a liner 8a removable together with the connected pre-column 8.
  • a substitution of precolumn 8 is made easy when, for instance, the packing present therein must be changed as a function of the volatile compounds to be trapped.
  • a packing 12 arranged between two layers 11 of glass wool or similar retaining material.
  • the pre-column 8 of the trap 2 has preferably a reduced section, of the order of tenths of mm, and the packing material 12 is present in the order of few mg.
  • Preferential dimensions are: internal diameter of about 0.53 mm for the pre-column 8, of about 0.32 mm for the column 9 and a packed zone of about 3 - 5 cm in length.
  • the choice of the packing material is made according to criteria known in the art (see for instance K. Grob et al. , Journal of Chromatography, 321, (1985) 45-58) as a function of the type of volatile compounds to be trapped and of the operational temperature. Generally said temperature ranges from -180 * C approx. during the concentration of volatile compounds in the trap, to a maximum of about 400 * C during their desorption and conveyance to the separation column.
  • Suitable packing materials are for example Tenax (TM), graphitized Tenax (TM) , Carbotrap (TM) and mixtures thereof.
  • TM Tenax
  • TM graphitized Tenax
  • TM Carbotrap
  • the temperature for the desorption of volatile compounds will proportionally increase with the retention power of the packing material.
  • Normal capillary columns suitable for the analysis to be performed can be used, and they will not be affected by the small amount of water entering the column.
  • the water penetrated in the column can be temporarily retained, namely during the first part of the gas chromatographic analysis, by using a column provided with an appropriate stationary phase, e.g. an AI2O3 PLOT column deactivated with KC1 or Said column is advantageously used in combination with a second non polar column, for instance of the SE-54 type, mounted in series with the first column, downstream of same.
  • This combination allows to perfectly resolve aromatic compounds too, and to have a long life of the column itself, that is considered to be constituted by two different portions.
  • this configuration it is also possible to obtain reproducible retention times and reduced analytical times, since it is not necessary to cool the oven at low temperature and avoid that alumina particles reach the detector and alter its operation.
  • Figure 3 shows in detail a preferential embodiment of connection between pre-column 8 and column 9.
  • column 9 is positioned inside the pre-column 8 and its upper end is preferably outside and in the vicinity of the lower limit of the trap 2.
  • the connection 13 is moreover provided with a purge line 14, having a fluidic resistance much lower than that of column 9. If this does not happen, it is possible to increase the column fluidic resistance by attaching a fused silica capillary having a little inner diameter (0,1-0,2 mm) at the column head.
  • the line 14 is positioned downstream of the inlet end of the column 9 and is thus in communication both with said column 9 and pre-column 8.
  • the trap 2 is connected in series, through the injector 7 (that can also be absent) and the line 6, to an injection valve 15 that is generally of the type with six of more positions.
  • the injection valve 15 is in turn connected through a line 21 to the selector 17, which has the function of selecting the samples coming on different lines.
  • the injection valve 15 is connected through line 16 to a carrier gas source, not shown, that is generally He.
  • the line 16 is also connected through a resistor R5 and an electrovalve EV3 to the purge line 14 and therethrough it is connectable to the line 18a leading to the vacuum pump 18.
  • Injection and selection valves 15 and 17 are housed (figures 1 and 2) inside a small chamber 25 thermostatable at a temperature ranging between ambient temperature and about 240 °C, whereas valve EVg is positioned near the injector 7 and is heated by it. Furthermore, the line 6 (figure 2) is provided with an insulation 6b from the injector 7 up to the valve 15.
  • the injection valve 15 is constructed to be used alternatively in a configuration with direct sampling or in a configuration with sampling by loop.
  • the basis of this flexibility of structure is given by the presence of a couple of connections arranged in correspondence to two adjacent ports 5 and 6 (figure 4).
  • the two connections are closed in a known way and are not used during the analysis.
  • said connections 5 and 6 are connected by means of two lines 15b and 15c, figure 7, to the ports 3 and 8 respectively and are used during the step of the sample concentration in the trap.
  • a mechanical or electronic flow regulator 19 allows to obtain a defined value of treated volume.
  • valve EV3 is switched to connect the line 14, through the resistor R5, to the line 16 feeding carrier gas, that is simultaneously conveyed along the valve 15, line 6 and injector 7, also to the trap 2, heated, for the transfer of volatile compounds from the trap 2 to the column 9.
  • valve 15 presents a loop 15a for sample loading.
  • the loop 15a is initially connected by means of the line 20 to the line 18a and the vacuum pump 18, by appropriately switching the valve EV2 (figure 4).
  • Valve EV4 can be programmed to remain open for a period of time to allow the pressure inside the loop to equilibrate to atmospheric pressure before transfer the loop contents to the trap. In this way the transferred volume is always the same because the pressure is constant or known.
  • Figure 9 shows a further embodiment of the invention, where, besides the injection valve 15, another valve 22 is present and is provided with two loops 23 and 24 having different dimensions and connectable alone or in series to the trap 2.
  • Figure 10 shows the scheme of pneumatics relating to an embodiment of 10-position valve 15, capable of feeding an internal standard during the analysis itself.
  • the valve 15, shown herein during the step of transfer the sample and internal standard to the trap 2 besides the loop 15a is provided with a loop for the internal standard 27, with a line 26 for internal standard feeding and with an outlet line 25, controlled by a valve 28.
  • the other configurations of the valve in the different analytical step are similar, mutatis mutandis, to those previously described.
  • Figures 11 to 14 show chromatograms as obtained in analyses performed following the method and with the equipment of the invention, according to the following modalities.
  • Example JL Example JL .
  • a 100 ml sample containing the following compounds at a concentration of 10 - 50 ppb was analysed operating with sampling by loop, at a transfer flowrate from the loop to the trap of 30 ml/min (He, 400 KPa), using a trap formed by a pre-column of fused silica with i.d. of 0.53 mm.
  • the trap was of the ejector type and was provided with a 4 cm packing consisting of a 1/1 mixture of Carbotrap (TM)/graphitized Tenax (TM) and was cooled to -150 'C by means of liquid nitrogen. At the end of the sample transfer, the trap was heated up to 240 °C.
  • Volatile compounds were conveyed with a He flow of 3 ml/min to the analysis on a column consisting of a first portion (50 m) of PLOT AL2O3 deactivated with KC1, serially connected to a following portion (25 m) of a non polar SE 54 column.
  • the gas chromatographic detector was of the FID type.
  • Figures 11 and 12 refer to analyses performed on samples containing 59% (figure 12) and 86% (figure 13) of moisture, respectively.
  • Figure 14 refers to the analysis of a sample containing 70% of moisture with separation carried out according to what described in example 1. In all three chromatograms, the signals corresponding to eluted water coming out from the column towards the FID detectors were indicated.

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  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Sampling And Sample Adjustment (AREA)
  • Investigating Or Analyzing Non-Biological Materials By The Use Of Chemical Means (AREA)

Abstract

Analyse de composés organiques volatils en faibles concentrations (p.p.b. ou p.p.t.), effectuée par passage d'un échantillon en écoulement dans un piège à condensation renfermant quelques milligrammes de matières de remplissage, selon une vitesse comprise entre 50 et 1000 cm/sec. Ensuite, on chauffe le piège afin de provoquer la désorption de l'échantillon ainsi concentré, puis on évacue ce dernier en vue d'effectuer une analyse.
PCT/EP1994/000889 1993-03-25 1994-03-22 Procede et appareil d'analyse de composes organiques volatils WO1994022009A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ITMI930571A IT1270972B (it) 1993-03-25 1993-03-25 Procedimento ed apparecchiatura per l'analisi di composti volatili organici.
ITMI93A000571 1993-03-25

Publications (2)

Publication Number Publication Date
WO1994022009A2 true WO1994022009A2 (fr) 1994-09-29
WO1994022009A3 WO1994022009A3 (fr) 1995-02-02

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WO (1) WO1994022009A2 (fr)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005038450A3 (fr) * 2003-10-17 2005-10-06 Perkinelmer Life & Analytical Sciences Procede d'introduction d'un gaz standard dans une cuve a echantillon
US8257951B2 (en) * 2002-10-28 2012-09-04 Little Sioux Corn Processors, LLC. Ethanol production process
WO2013037182A1 (fr) * 2011-09-16 2013-03-21 武汉市天虹仪表有限责任公司 Analyseur en ligne de composé organique volatil et procédé d'utilisation de celui-ci
CN103499662A (zh) * 2013-09-12 2014-01-08 苏州威阳环保科技有限公司 一种大气挥发性有机物取样分析装置及取样分析方法
KR101818841B1 (ko) * 2016-03-09 2018-01-16 포항공과대학교 산학협력단 휴대용 육불화황 분석 시스템
CN108627369A (zh) * 2017-03-20 2018-10-09 广州禾信仪器股份有限公司 大气挥发性有机物双级深冷在线富集浓缩采样系统及方法
CN109799302A (zh) * 2019-03-20 2019-05-24 上海市环境科学研究院 中等挥发性有机化合物近在线检测方法
CN112816644A (zh) * 2020-12-31 2021-05-18 杭州谱育科技发展有限公司 水中VOCs检测装置及方法

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3592064A (en) * 1969-02-18 1971-07-13 Bryggeriindustriens Forsknings Method for transferring a sample to be analyzed into the column of a gas chromatograph, and system for carrying out the method
US4998433A (en) * 1989-06-19 1991-03-12 Stumpf David K Method and means for condensing trace air contaminates from gases
US5141534A (en) * 1990-09-28 1992-08-25 The Regents Of The University Of Michigan Sample collection and inlet systems for gas chromatography apparatus
US5168746A (en) * 1991-06-03 1992-12-08 Hughes Aircraft Company Ambient ether vapor testing apparatus and method

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8257951B2 (en) * 2002-10-28 2012-09-04 Little Sioux Corn Processors, LLC. Ethanol production process
WO2005038450A3 (fr) * 2003-10-17 2005-10-06 Perkinelmer Life & Analytical Sciences Procede d'introduction d'un gaz standard dans une cuve a echantillon
US8247239B2 (en) 2003-10-17 2012-08-21 Perkinelmer Health Sciences, Inc. System for introducing standard gas into sample container
WO2013037182A1 (fr) * 2011-09-16 2013-03-21 武汉市天虹仪表有限责任公司 Analyseur en ligne de composé organique volatil et procédé d'utilisation de celui-ci
JP2014529080A (ja) * 2011-09-16 2014-10-30 武▲漢▼市天虹▲儀▼表有限▲責▼任公司Ｗｕｈａｎ Ｔｉａｎｈｏｎｇｉｎｓｔｒｕｍｅｎｔｓ Ｃｏ．， Ｌｔｄ オンライン揮発性有機物分析器及びその使用方法
US8939011B2 (en) 2011-09-16 2015-01-27 Wuhan Tianhong Instruments Co., Ltd On-line analyzer for VOCs and method of using the same
CN103499662A (zh) * 2013-09-12 2014-01-08 苏州威阳环保科技有限公司 一种大气挥发性有机物取样分析装置及取样分析方法
KR101818841B1 (ko) * 2016-03-09 2018-01-16 포항공과대학교 산학협력단 휴대용 육불화황 분석 시스템
CN108627369A (zh) * 2017-03-20 2018-10-09 广州禾信仪器股份有限公司 大气挥发性有机物双级深冷在线富集浓缩采样系统及方法
CN108627369B (zh) * 2017-03-20 2023-11-07 广州禾信仪器股份有限公司 大气挥发性有机物双级深冷在线富集浓缩采样系统及方法
CN109799302A (zh) * 2019-03-20 2019-05-24 上海市环境科学研究院 中等挥发性有机化合物近在线检测方法
CN112816644A (zh) * 2020-12-31 2021-05-18 杭州谱育科技发展有限公司 水中VOCs检测装置及方法

Also Published As

Publication number Publication date
IT1270972B (it) 1997-05-26
ITMI930571A0 (it) 1993-03-25
ITMI930571A1 (it) 1994-09-25
WO1994022009A3 (fr) 1995-02-02

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