Method for detecting and quantifying oxygen in oxidizable compounds by oxidizing a sample with an isotopic oxygen composition different from natural abundance

Abstract

The present invention concerns an analytical method that makes use of an oxygen-containing source having a predetermined content of an isotope of oxygen .sup.ZO, which is not the same as natural composition and distribution of oxygen isotopes, to detect and/or quantify oxygen in oxidizable compound(s). The analytical method allows detecting and/or quantification with relatively high precision and accuracy oxygen in oxidizable compound(s), even at low content. The method is easy to implement and can be used for in-line analysis.

Claims

1. A method for oxygen analysis in an oxidizable compound or in a mixture of oxidizable compounds, said oxidizable compound(s) being organic compound(s), comprising: (a) providing a test sample containing at least one oxidizable compound and a reference sample containing at least one oxidizable reference compound which contains at least one chemical element present in the test sample, (b) submitting separately the test sample and the reference sample to the following steps under the same conditions: (i) a step of complete oxidative reaction, in which the sample is submitted to an oxidizing medium containing at least one oxidizing agent under conditions efficient to completely oxidize the sample into gaseous oxidized species A.sub.aO.sub.o, where A is any chemical element different from O present in the sample, a is the number of A atoms, o is the number of O atoms, said oxidizing medium containing a predetermined content of an isotope of oxygen .sup.ZO that is not the same as natural composition and distribution of oxygen isotopes, where z is the mass number of the atom, (ii) a step of detection, in which all the gaseous oxidized species A.sub.aO.sub.o formed in step (i) are detected by means of a detector device adapted to detect gaseous oxidized species containing different isotopes of oxygen and to generate, for each detected gaseous species, a signal representative of the quantity of said detected gaseous species, the signals obtained for the test sample and for the reference sample being further treated and compared for at least one action chosen from determination of the presence of oxygen and quantification of oxygen, and prior to step (i), the test sample is introduced into a liquid or gas chromatography device to separate oxidizable compounds having different retention times, which are then submitted separately to steps (i) and (ii).

2. The method according to claim 1, wherein in step (b), the test sample and the reference sample are volatilized prior to be submitted to step (i) by using a gas chromatography device.

3. The method according to claim 1, comprising a further step of determination of the chemical formula of said at least one oxidizable compound contained in the test sample.

4. The method according to claim 3, wherein said step of determination of the chemical formula comprises analyzing said compound(s) using a gas or liquid chromatography device.

5. The method according to claim 1, where the reference sample does not contain oxygen, further comprises a step (c) for each separated oxidizable compounds having different retention times, this step (c) including, for each gaseous oxidized species A.sub.aO.sub.o, or for some predetermined gaseous oxidized species A.sub.aO.sub.o, obtained from complete oxidation step (i): extracting compound test values from treatment of the signals generated by the detector device at step (ii) for said separated oxidizable compound, said compound test values being the values of each isotopic ratio A.sub.a.sup.16O/A.sub.a.sup.ZO.sub.i.sup.16O.sub.o-i, where indicia i is an integer taking all the values from zero to o, obtained from the corresponding oxidized species A.sub.aO.sub.o, extracting reference values from treatment of the signals generated by the detector device at step (ii) for the reference sample, said reference values being the values of each isotopic ratio A.sub.a.sup.16O/A.sub.a.sup.ZO.sub.i.sup.16O.sub.o-i for which a compound test value has been determined, determining if the separated oxidizable compound contains oxygen by checking if at least one of its compound test values differs from the corresponding reference value.

6. The method according to claim 5, wherein in step a), the reference sample contains at least one reference compound in a known amount and the at least one reference compound contains at least one chemical element different from O present in said at least one oxidizable compound contained in, or consisting, the test sample, and wherein, when step (c) has determined that a separated oxidizable compound contains oxygen, the analytical method further comprises, for each separated oxidizable compound containing oxygen: a quantification step (d) comprising: extracting from treatment of the signals generated by the detector device at step (ii) for this oxygen-containing separated oxidizable compound, values representative of intensities of the signals generated at step (ii) for all the isotopes of a predetermined species A.sub.aO.sub.o, where element A is present in both the separated oxidizable compound and reference sample, and summing these intensity values, extracting from treatment of the signals generated by the detector device at step (ii) for the reference sample, values representative of intensities of the signals generated at step (ii) for all the isotopes of the predetermined species A.sub.aO.sub.o, and summing these intensity values, from the known amount of A contained in the reference sample and from the above sums, calculating the amount of A in the oxygen-containing separated oxidizable compound, and calculating the amount of O in the oxygen-containing separated oxidizable compound or the amount of the oxygen-containing separated oxidizable compound by means of the chemical formula of the oxygen-containing separated oxidizable compound determined in a previous step.

7. The method according to claim 6, where the reference sample does not contain oxygen and further comprising a step (c′) including, for each gaseous oxidized species A.sub.aO.sub.o, or for some predetermined gaseous oxidized species A.sub.aO.sub.o, obtained from complete oxidation step (i): extracting test values from treatment of the signals generated by the detector device at step (ii) for the test sample, said test values being the values of each isotopic ratio A.sub.a.sup.16O/A.sub.a.sup.ZO.sub.i.sup.16O.sub.o-i where indicia i is an integer taking all the values from 0 to o, extracting reference values from treatment of the signals generated by the detector device at step (ii) for the reference sample, said reference values being the values of each isotopic ratio A.sub.a.sup.16O/A.sub.a.sup.ZO.sub.i.sup.16O.sub.o-i for which a test value has been determined, determining if the test sample contains oxygen by checking if at least one of the test values differs from the corresponding reference value.

8. The method according to claim 5, wherein: in step (a), the reference sample contains at least one reference compound in a known amount and the at least one reference-compound contains at least one chemical element different from O present in said at least one oxidizable compound contained in, or consisting, the test sample, step (c) or (c′) is performed for all the gaseous oxidized species A.sub.aO.sub.o obtained from complete oxidation step (i) and detected in step (ii), and wherein the analytical method further comprises: a step (d′) for determining the quantity of oxygen in the test sample, including, for each gaseous oxidized species A.sub.aO.sub.o for which it has been determined at step (c) or (c′) that the isotopic ratio value of the test sample, optionally the isotopic ratio value of a separated oxidizable compound, differs from the value of the same isotopic ratio of the reference sample, showing the presence of oxygen originating from the test sample, optionally from the separated oxidizable compound: extracting from treatment of the signals generated by the detector device at step (ii) for the test sample, optionally for the separated oxidizable compound, values representative of intensities of the signals generated at step (ii) for all the isotopes of this A.sub.aO.sub.o species, and summing these intensity values, extracting from treatment of the signals generated by the detector device at step (ii) for the reference sample, values representative of intensities of the signals generated at step (ii) for all the isotopes of this A.sub.aO.sub.o species, and summing these intensity values, from the known amount of A contained in the reference sample and from the above sums, calculating the amount of A in said test sample, optionally in the separated oxidizable compound, and then calculating its amount of oxygen using the isotopic ratio A.sub.a.sup.16O/A.sub.a.sup.ZO.sub.i.sup.16O.sub.o-i and the abundances of the isotopic O present in the oxidizing medium.

9. The method according to claim 1, wherein: in step (a) the reference sample contains at least one reference compound in a known amount and the at least one reference compound contains any chemical element present in said at least one oxidizable compound contained in, or consisting, the test sample, and wherein the analytical method further comprises, optionally for each separated oxidizable compound: a quantification step (e) comprising: extracting from treatment of the signals generated by the detector device at step (ii) for the test sample, optionally for the separated oxidizable compound, values representative of intensities of the signals generated at step (ii) for all the isotopes of the oxidized species A.sub.aO.sub.o of a predetermined chemical element A or O, where element A or O is present in both the reference sample and the test sample, optionally the separated oxidizable compound, and summing these intensity values, extracting from treatment of the signals generated by the detector device at step (ii) for the reference sample, values representative of intensities of the signals generated at step (ii) for all the isotopes of oxidized species A.sub.aO.sub.o of same element A or O, and summing these intensity values, from the amount of A or O contained in the reference sample and from the above sums, calculating the amount of A or O in the test sample, optionally in the separated oxidizable compound.

10. The method according to claim 1, wherein the oxygen isotope .sup.ZO present in the oxidizing medium is chosen among .sup.18O, .sup.17O and their mixture.

11. The method according to claim 1, wherein at least one oxidizing agent in the oxidizing medium is chosen from (1) an oxygen-containing gas, and (2) a metal oxide, said metal being optionally chosen among Cu, Ni, or others.

12. The method according to claim 1, wherein the detector device used in step (ii) a cavity Ring Down infra-red spectrometer.

13. The method according to claim 1, wherein the test sample is a mixture of hydrocarbonaceous organic compounds of vegetal, animal or fossil origin.

14. The method according to claim 1, wherein the test sample is chosen among (1) synthetic crude or fractions thereof; (2) crude petroleum or fractions thereof; (3) refinery off-gas; (4) LPG; (5) monomer containing material such as ethylene, propylene, butene isomers, pentene isomers, hexene isomers, their mixtures, and their mixtures with their corresponding alkanes; (6) pyrolysis gas; (7) naphtha; (8) gasoline; (9) jet-fuel; (10) avgas; (11) diesel fuel; (12) bunker fuel; (13) bitumen; (14) petroleum residue such as light cycle oil, heavy cycle oil, atmospheric residue, vacuum residue, visbroken residue, slurry residue, pet-coke; (15) optionally hydrogenated oil or wax directly issued from animal, vegetal or algal biomass or waste.

15. The method according to claim 1, wherein the oxidizable reference compound contains C and either N or S.

16. The method according to claim 1, wherein the reference sample comprises As, Se, or Pb.

17. The method according to claim 1, wherein the oxidizing agent is mixed with an inert gas.

18. The method according to claim 1, wherein the oxidizing agent is a metal oxide comprising Cu or Ni.

19. The method according to claim 1, wherein the oxidative reaction is performed in the presence of a catalyst, wherein the catalyst comprises Cu, Ni, or Pt, or a metallic oxide.

20. The method according to claim 19, wherein the metallic oxide is CuO or AgO.

21. A method for operating an industrial unit comprising at least one operation step in which the presence of oxygen and/or the content of oxygen in one or several fluids circulating into the industrial unit is determined by means of the analytical method according to claim 1, said operation being chosen among the management, control, monitoring, startup, shutdown, adjustment and tuning of the industrial unit.

22. The method for operating according to claim 21, wherein the industrial unit is part of a chemical or petrochemical plant.

23. The method for operating according to claim 22, wherein the industrial unit is chosen from (1) a fixed bed catalytic cracker or a fluid catalytic cracker, (2) a steam cracker, (3) a hydrogenating unit working under pressure for hydrogenation of olefins or alkynes, sulfur removal (EDS), oxygen removal (HDO) and/or nitrogen removal (HDN), (4) a hydrocracker, (5) a steam methane reformer, (6) a unit converting alcohols into olefins such as Methanol To Olefins (MTO) unit and MTO/OCP, (7) an isomerisation unit, (8) a visbreaker, (9) an alkylation unit, (10) a bitumen blowing unit, (11) a distillation tower such as atmospheric or vacuum towers, (12) a sulfur recovery unit, (13) an amine washing unit, (14) a hydrocarbon deep conversion unit such as H-Oil, ARDS, coker, slurry hydrocracker, (15) a polymerization unit such as those using ethylene, propylene, styrene, or butadiene monomer and their mixtures, and eventually with at least one other additional monomer, (16) a syngas producing unit, (17) a syngas fed unit such as a Fischer-Tropsch unit.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 represents an example of analytical device for performing the method according to the invention,

(2) FIG. 2 represents an extract of a mass chromatogram registered for test A in which the intensity of signals corresponding to m/z species of 18, 20, 44, 46 and 48 are represented in function of the retention time.

(3) FIG. 1 shows an example of analytical device 10 that can be used for implementing the analytical method of the present invention.

(4) The analytical device 1 comprises a gas chromatography device 2, a combustion unit 3 and a detector device 4.

(5) The sample to analyze (test sample) is injected into the gas chromatography device 2 using an injector 5, for example an injection port that is part of the gas chromatography device 2. The injector 5 volatilizes the test sample which then passes through a separation column of the gas chromatography device 2.

(6) When the sample contains different oxidizable compounds, volatilized oxidizable compounds with different retention times leave the gas chromatography device 2 separately.

(7) The volatilized oxidizable compounds leaving the gas chromatography device 2 are conducted through a line 6, for example a fused silica capillary, to the combustion unit 3. Therefore, the volatilized oxidizable compounds having different retention times pass through the combustion unit 3 separately.

(8) The combustion 3 unit is for example an oven which is dimensioned to permit a complete oxidative reaction of the volatilized oxidizable compounds while avoiding remix of the volatized oxidizable compounds of different retention times. Thus, the order of the retention times of oxidizable compounds passing through the combustion unit 3 is not modified.

(9) By way of example, the combustion unit 3 can comprise a ceramic tube having an external diameter of 3 mm, an inside diameter of 0.5 mm and a length of 35 cm, said ceramic tube being surrounded by a resistance, the whole being placed inside a thermal insulator.

(10) The combustion unit 3 usually comprises a temperature sensor for temperature regulation.

(11) A line 7 permits to provide the combustion unit 3 with an oxygen-containing gas to perform the complete oxidative reaction. According to the invention, the oxygen-containing gas has a predetermined content of an isotope of oxygen .sup.ZO. Preferably, .sup.18O.sub.2 is used as oxygen-containing gas. If the addition of the oxygen-containing gas is produced on-line with the volatilized oxidizable compounds for their combustion, the excess of oxygen-containing gas should be removed before reaching the detector device 4.

(12) To promote the oxidative reaction, the combustion unit 3 can contain a catalyst, for example Cu and Pt wires or wires of any other appropriate metals or alloys thereof and under any appropriate shape (wires, mesh, nano-particles . . . ). Previously to the oxidative reaction or during the reaction, the Cu wires are oxidized into CuO by the oxygen-containing gas. The oxygen isotope .sup.ZO is therefore present in CuO. Eventually, in any embodiment, the oxidative reaction can be performed only in presence of the metallic oxide containing the oxygen isotope .sup.ZO, without the above mentioned oxygen-containing gas.

(13) In the combustion unit 3, the volatilized oxidizable compounds are completely oxidized. By way of example, an oxidizable organic compound C.sub.cH.sub.h or an oxidizable organic compound C.sub.cH.sub.hO.sub.o will form cCO.sub.2 and h/2H.sub.2O, a C.sub.cH.sub.hN.sub.n compound will form cCO.sub.2, nNO.sub.x and h/2H.sub.2O, and a C.sub.cH.sub.hS.sub.s compound will form cCO.sub.2, sSO.sub.x and h/2H.sub.2O.

(14) The oxidized species leave the combustion unit 3 and pass to the detector device 4 via a line 8, for example a fused silica capillary.

(15) In general, in any embodiment, the detector device 4 detects the different m/z oxidized species leaving the combustion unit 3 and generates signals, each signal being representative of a m/z oxidized species and depending on the quantity of the detected m/z oxidized specie. This detector device 4 is for example a mass spectrometer or any other device adapted to detect different species and their isotopes, such as a cavity Ring Down spectrometer.

(16) A line 9, connected to line 8, permits to provide known amount of isotopes of chemical elements other than oxygen, when determination of the amount of other chemical element is to be performed by isotopic dilution according to the method disclosed in EP1939617. The isotopes species introduced may for example be .sup.13CO.sub.2, .sup.15NO.sub.x, .sup.34SO.sub.x.

(17) A three-way valve 10 can be provided on line 6 to connect the gas chromatography device 2 directly to the detector device 4, for example for qualitative analysis.

(18) Gas chromatography device 2 may be replaced by a liquid chromatography device.

(19) The detector device 4 can be connected to a determination device 11 for performing the determination step of the analytical method that is any of steps (c), (c′), (d, (d′), (e).

(20) The determination device 11 may comprise: reception means 12 to receipt signal(s) generated by the detector device 4, processing means 13 that are arranged so as to, upon reception of the signal generated by the detector device, treat the signals, determine intensity values, isotopic ratio values or peak area or peak height values and determine the presence of oxygen, the quantity of oxygen, of oxygenated compound, or of any compound present in the sample, or the quantity or chemical elements other than oxygen, transmitting means 14 to transmit to a display unit 15 the signals generated by the detector device and/or the values determined by the processing means 13, eventually a memory 16 to store the signals and determined values.

(21) The processing means may also generate a control signal to control the combustion unit 3, and eventually the gas chromatography device 2 and the detector device 4.

(22) This determination device 11 may comprise or be integrated into one or several processors, e.g. microcontrollers, microprocessors, etc.

(23) The reception means may comprise an output pin, an entry port, etc. The processing means may comprise a central processing unit, a processor, etc. The transmitting means may comprise an output pin, an output port, etc.

EXAMPLES

Experimental

(24) Tests were performed on an instrumental device as described in reference with FIG. 1, wherein: the gas chromatography device comprises a column DB-5 (30 m length; 0.25 mm Internal Diameter), the combustion oven 14 contains Cu and Pt wires, the detection device is a mass spectrometer, detecting m/z: 18, 20, 44, 45, 46, 47, 48, 49.

(25) The conditions of operation of the gas chromatography device are reported in table 1, using a split/splitless injector.

(26) The temperature of the combustion oven was set to 850° C.

(27) The oxygen containing gas used in the combustion oven is .sup.18O.sub.2, with an isotopic content of 97.1% of .sup.18O and a 2.1% content of .sup.16O.

(28) Before combustion, a flow of the above oxygen containing gas is flushed in the oven, whereby the Cu wires are oxidized by .sup.18O and .sup.16O. The abundances in .sup.18O (Ab.sup.18O) and .sup.16O (Ab .sup.16O) finally retained in the Cu filaments can be determined by mass spectrometry. We obtained this time: Ab .sup.16O=20.3% and Ab.sup.18O=78.1. However, it should be noted that these values could be slightly different depending in the conditions used during the flushing of the oxygen containing gas into the oven.

(29) The combustion is then performed without flushing with the oxygen containing gas.

(30) TABLE-US-00001 TABLE 1 conditions of the gas chromatography (GC) device: GC Splitless Mode Injector temperature 250° C. Splitless time 0.8 min Split ratio 1:50 Injected volume 1 μL Carrier gas helium Oven temperature program 50° C. (1 min) 15° C. min.sup.−1 250° C. (3 min)
Sample Analysis

(31) A solution made of a mixture of 4 alkanes and 4 esters in known quantities was analyzed in the conditions mentioned above. The composition of the solution is detailed in table 2.

(32) FIG. 2 represents a part of the mass spectrometry spectra obtained, where only the peaks of tetradecane and ethyl benzoate have been represented for clarity sake. In FIG. 2, peaks corresponding to H.sub.2O have been shifted with respect to CO.sub.2 peaks for clarity.

(33) TABLE-US-00002 TABLE 2 composition of the sample in weight ppm ppm ppm ppm ppm Compound Formula compound C O H undecane C.sub.11H.sub.24 59.3 50.1 — 9.17 ethyl benzoate C.sub.9H.sub.10O.sub.2 63.2 45.5 13.5 4.24 hexyl butyrate C.sub.10H.sub.20O.sub.2 73.8 51.4 13.7 8.64 phenethyl acetate C.sub.10H.sub.12O.sub.2 75.5 55.2 14.7 5.56 tetradecane C.sub.14H.sub.30 61.2 51.8 — 9.32 diethyl phthalate C.sub.12H.sub.14O.sub.4 77.3 49.7 22.1 4.86 octadecane C.sub.18H.sub.38 60.2 51.1 — 9.06 nonadecane C.sub.19H.sub.40 63.3 53.8 — 9.50

Example 1

Determination of Presence of Oxygen

(34) By measurement of peak area ratios, the following isotopic ratios have been determined: H.sub.2.sup.16O/H.sub.2.sup.18O corresponding to isotopic ratio 18/20, C.sup.16O.sub.2/C.sup.18O.sub.2 corresponding to isotopic ratio 44/48, C.sup.16O.sub.2/C.sup.18O.sup.16O, corresponding to isotopic ratio 44/46, (H.sub.2.sup.16O+C.sup.16O.sub.2)/(H.sub.2.sup.18O+C.sup.18O.sub.2) corresponding to isotopic ratio (18+44)/(20+48).

(35) The values obtained are collected in table 3.

(36) It can be noted that isotopic ratios 44/48 and 44/46 are very similar in this sample for the alkanes (tetradecane, octadecane and nonadecane) and the O-containing compounds (phenethyl acetate and ethyl benzoate). In fact differences are below 2%. We notice a difference in isotopic ratios 18/20 and (18+44)/(20+48).

(37) Ratios (18+44)/(20+48) correspond to the ratio of the oxidized species that contain .sup.16O exclusively (18 and 44), that comes from the sample and the oxidized medium and .sup.18O exclusively (20 and 48), that comes from the oxidized medium as we can neglect the abundance of .sup.18O in natural O (0.2%). Therefore, if in a peak observed for a particular retention time, this ratio is different from the ratio obtained for an alkane burnt (internal reference(s) that could be tetradecane, octadecane or nonadecane in this case), this means that the organic compound eluting at this particular retention time contains oxygen.

(38) Table 3 shows that the ratios of phenethyl acetate are always statistically different (at 95% confidence, 2 standard deviations) from the ratios of alkanes.

(39) Similar results are observed for isotopic ratios 18/20, comparison of these ratios also show a difference confirming presence of oxygen in phenethyl acetate.

(40) Similarly, results collected in table 3 confirm the presence of oxygen in ethyl benzoate.

(41) TABLE-US-00003 TABLE 3 18/20, 44/48, 44/46 isotopic ratios and (18 + 44)/(20 + 48) isotopic ratios obtained by measurement of peak area ratios (18 + 44)/ Compound (20 + 48) 44/48 44/46 18/20 tetradecane 0.1570 0.0610 0.1245 0.4438 phenethyl acetate 0.1384 0.0611 0.1253 0.5479 Ethyl benzoate 0.1469 0.0602 0.1225 0.6341 octadecane 0.1588 0.0613 0.1248 0.4563 nonadecane 0.1597 0.0618 0.1257 0.4596 Mean alkanes 0.1585 0.0614 0.1250 0.4532 SD alkanes 0.0014 0.0004 0.0006 0.0083 Mean alkanes represents the mean value on the ratios determined for the 3 alkanes species and SD alkanes represents its standard deviation.

Example 2

Quantification Using C Quantification and the Chemical Formula of the Test Sample

(42) The amount of oxygen can then be determined, for example using an internal or external reference compound, the amount of which is known. It is also possible to determine the amount of the corresponding oxygenated compound using an internal or external reference compound of known amount, containing oxygen or not.

(43) In the present case, the quantity of carbon contained in ethyl benzoate and phenethyl acetate was determined using the CO.sub.2 issued from the combustion/oxidative reaction, using one or several alkanes as internal reference. To this effect, we sum the areas of all the isotopic species (detected at different m/z) of CO.sub.2 that will contain all the C present.

(44) The signals of CO.sub.2 for the reference compound are then used to produce a response factor Rf (area total/mass of C) as we know the C content.

(45) This factor can be applied to the target compound (here ethyl benzoate or phenethyl acetate) to quantify the C present (Compound Independent Calibration, CIC).

(46) Table 4 collects the areas of the CO.sub.2 peaks determined for tetradecane, ethyl benzoate and phenethyl acetate.

(47) TABLE-US-00004 TABLE 4 Areas of CO.sub.2 peaks of ethyl benzoate, phenethyl acetate and tetradecane area peak area peak area peak Total m = 44 m = 46 m = 48 areas tetradecane 0.4442 3.5670 7.284 11.29 ethyl benzoate 0.3320 2.7104 5.5190 8.561 phenethyl acetate 0.4377 3.4933 7.1669 11.10

(48) From these value, we can determine for tetradecane: response factor,

(49) $Rf=\frac{\mathrm{area}\mathrm{total}}{\mathrm{ppm}C}=\frac{11.29}{51.8}=0.218$

(50) And deducing the C content in phenethyl acetate

(51) $\frac{\mathrm{area}\mathrm{total}}{\mathrm{Rf}}=\frac{11.10}{0.218}=50.92\mathrm{wt}\mathrm{ppm}C.$

(52) The formula of phenethyl acetate being known (C.sub.10H.sub.12O.sub.2), we can determine the amount of O, here 13.58 wt ppm.

(53) By comparison with the values of table 2, the error of determination of the C and O content of phenethyl acetate is 7.8%.

(54) By similar calculation, we can determine the amount of O in ethyl benzoate with an error of 13.6%.

Example 3

Quantification Without Knowing the Chemical Formula of the Test Sample

(55) This quantification uses the altered O ratios in the species and the absolute amount of the other element present in such species.

(56) In this case, chemical formula is not needed so this approach can be applied to quantify the: O present in individual compounds separated by chromatography which identity is not known O present in mixtures of compounds (with or without chromatography separation).

(57) In the present case (same test sample as in examples 1 and 2), isotopic ratios 44/48 and 44/46 have also been measured, where m/z=44 corresponds to C.sup.16O.sub.2, m/z=46 corresponds to C.sup.16O.sup.18O, m/z=44 corresponds to C.sup.18O.sub.2.

(58) From table 3, it can be observed that isotopic ratios 44/46 and 44/48 are the same for all the molecules, even if the molecule initially contains oxygen. It can therefore be supposed that .sup.16O contained in the oxygenated compounds is not recovered in CO.sub.2 specie, but rather in H.sub.2O species.

(59) In the present case, O goes only to H.sub.2O. A theoretical example of the computation that needs to be made is then presented. We can therefore quantify the H present and use the isotopic ratio in that species (18/20—corrected if necessary) and the abundances of the isotopic O present in the oxidizing medium to quantify the O present.

(60) If we assume that the O(nat) present in the test sample goes to water we will obtain the following for an oxygenated compound of formula C.sub.cH.sub.hO(nat).sub.o:
c moles of CO.sub.2(iso),o moles of H.sub.2O(nat) and (h/2−o) moles of H.sub.2O(iso).

(61) O(nat) can be considered as pure .sup.16O (0.998 abundance) but O(iso) will reflect the abundances of the O (noted Ab .sup.16O and Ab.sup.18O) finally retained in the Cu filaments and will contain both .sup.16O and .sup.18O. Then:

(62) The moles of H.sub.2.sup.16O detected at m/z=18 is equal to:
o+Ab.sup.16O.Math.(h/2−o)
The moles of H.sub.2.sup.18O detected at m/z=20 is equal to:
Ab.sup.18O.Math.(h/2−o)
The Ratio is then:

(63) $R=\frac{18}{20}=\frac{H_2{\hspace{0.17em}}^{16}O}{H_2{\hspace{0.17em}}^{18}O}=\frac{o+\mathrm{Ab}{\hspace{0.17em}}^{16}O.Math.\left(\frac{h}{2}-o\right)}{\mathrm{Ab}{\hspace{0.17em}}^{18}O.Math.\left(\frac{h}{2}-o\right)}$
We can deduce from the above:

(64) $o=\frac{h}{2}.Math.\frac{R.Math.\mathrm{Ab}{\hspace{0.17em}}^{18}O-\mathrm{Ab}{\hspace{0.17em}}^{16}O}{1+R.Math.\mathrm{Ab}{\hspace{0.17em}}^{18}O-\mathrm{Ab}{\hspace{0.17em}}^{16}O}$
First we carry out the quantification of H in the target using compound Independent Calibration (CIC) and the reference compound. The area of H.sub.2O peaks are reported in table 5.

(65) TABLE-US-00005 TABLE 5 area of peaks corresponding to m/z = 18 and 20 (H.sub.2O peaks) compound Area 18 Area 20 Total tetradecane 1.082 2.4386 3.5208 ethyl benzoate 0.6227 0.9821 1.6048 phenethyl acetate 0.7412 1.3528 2.094
From the area measured for the reference compound (tetradecane), the response factor Rf is determined:

(66) $Rf=\frac{\mathrm{area}\mathrm{total}}{\mathrm{ppm}H}=\frac{3.5208}{9.32}=0.378$

(67) And then, the amount of H in the phenethyl acetate:

(68) $\frac{\mathrm{area}\mathrm{total}}{\mathrm{Rf}}=\frac{2.094}{0.378}=5.54\mathrm{ppm}H$

(69) Using the number of moles of H (h) formed, the ratio 18/20 and the abundances of the isotopic O in the oven, we can determine the O amount: 15.97 ppm O.

(70) By comparison with the values of table 2, the error of determination of the H and O content of phenethyl acetate is 0.3 and 8.5%, respectively.

(71) By similar calculation, we can determine the amount of H and O in ethyl benzoate with an error of 6.8 and 1.4%, respectively.