DE2311135A1 - METHOD OF FLAME PHOTOMETRY AND PERFORMANCE OF A SUITABLE DETECTOR - Google Patents

Description

Method of flame photometry and to its implementation suitable detector

Priority: Mar 3, 1972 - USA - Serial No. 232 926

It becomes a flame photometer detector with a burner unit described, which has a first passage leading to the burner tip, so that a mixture of hydrogen de fuel gas and a combustion-promoting gas, For example, oxygen "can be supplied to the burner tip via this passage in order to produce a hydrogen-rich" to produce a reducing flame. The one to be analyzed Sample is fed in via a second passage and with a sample guide in the Uzafangsboroich the reducing Directed flame, where the sample is burned in a hydrogen-rich area of relatively low temperature, so that the interfering light emlssion of interfering substances is kept at a low T.'ert.

Behind the Flame photometry detectors are now commonly called

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relatively cheap spoktroscopic dopants for use with gas chromatographs, especially for the analysis of sulfur and phosphorus substances in the output stream of the gas chromatograph. As in an article by CH. Hartmann "Gaschromatographic Detectors", Analytical Chemistry, Vol. 43, No. 2, pages 113A to 125A, February 1971 », the basic elements of a flame photometry detector are a burner nozzle, where the output _{sample from the gas chromatograph is burned in the combustion, which is replaced by H 2} as the fuel gas and a combustion-promoting gas such as oxygen or air , and a spectrometer with which the burning sample is observed and which has a suitable light filter uxd a photodetector * When substances containing sulfuric oil are burned in the hydrogen-rich flame, they emit a characteristic light spectrum at around 360 to 410 nm; Burning phosphorus-containing substances provide light emission with a focus at around 526 nm.

In known detectors of this type (US Pat. No. 3,290,118; 3 4C9 498) the sample to be examined, for example air or the column output stream of a gas chromatograph, mixed with the combustion-promoting gas, such as oxygen or air, and this mixture becomes the burner tip fed through a stirrer or channel. The hydrogen is fed to the Brezmer housing via a separate passage, where it burns with the sample gas and oxygen and causes the desired combustion.

The flame achieved with such a device cannot be reliable in operation, for example because of it can be blown out that a sudden shock wave of solvent in the outlet stream of the gas chromatograph

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may be contained and result in oino oxygen depletion Furthermore, if the column output Bdt of the oxygen source When the detector is disconnected, the bottle goes out and the hydrogen can escape Form a source of danger

In addition, separate the sample and the carrier gas. Into the very hot Iuteltell the hydrogen-oxygen flame is introduced »results in the combustion of substances such as organic compounds» which may be present »an interfering light emission» which reduces the specific effectiveness of the detector »ie its Ability to react chiefly to a certain group or groups of substances - especially only ? Mn * ^ma T to all other substances. So far, special precautions have been taken »to block this disruptive light emission for the spectrometer; For example, according to US Pat. No. 3,489,498, a cylindrical screen is placed around the burner tip "so that the lower part of the flame" where such disturbance-producing combustion normally takes place is not in the optical line of sight of the photospectrometer "so that this disturbing light emission the selectivity does not deteriorate. Blocking the emitted light in this way, however, brings about a certain reduction in detector sensitivity »ie the effectiveness of the detector as a transducer» with which the sample is converted into a measurable electrical signal »because part of the desired emission is also blocked.

the

The invention is a novel flame photometry

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Detector made available in which the hydrogen as Fuel gas and the combusting gas, for example Oxygen, first mixed and then fed to the torch tip through a single passage to generate the desired reducing flame at the tip. The sample becomes the circumferential area of the flame supplied via a separate Passago, so that the consumption the sample takes place in the outer part of the flame. This makes the flame much more reliable and becomes Do not tune with solvent impacts through the sample line blown out · In fact, the flame continues to burn even if the gas chromatograph column is removed. As a result this premix does not result in any freely flowing hydrogen that can escape.

Since the sample is introduced into the circumferential area of the flame, it burns in a cooler part of the hydrogen-rich flame and thereby the substances of interest are burned under optimal conditions, including temperature and hydrogen concentration, while at the same time the interfering substances are burned under non-optimal conditions. This results in a minimal Sturllohtomlssion, ν & Λ therefore frg t w n a more comprehensive consideration of the flame for the spectrophotometer is provided.

The invention is to be explained in more detail with reference to the drawing} show it:

Fig. 1 is a longitudinal section through a preferred Auefühi-ungeform of a flame photometry detector according to Dor Invention;

Flg. 2 shows the tip area of the burner area of a detector according to FIs * 1; and

Flg. 3 shows a heat curve of a known detector and a proper detector.

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The detector shown in the drawing consists of a generally elongated body old dor the burner device 11 to a 2ηΛο, the photospectroneter 12 am at the other end and an iconic Yerbrennuncskaxnaer in between 13 · UIe for conventional Flainienphotometrle detectors the construction is equipped with a suitable igniter 14 "with which the fluff is ignited" and an ion collocator 15, with the hydrocarbons In the chamber 13 are monitored.

The burner device consists of a mounting base plate 21 with an elnor threaded hole '22 and a cylindrical Brexmorbasls 23 which is screwed into the hole in the base plate. "The burner base 23 is provided with an axial hole 24" which is provided with an internal thread at the upper end and fits into a hole 24 * tapers at the lower 3ndo »where it is provided with a hole 25 as a flow passage. This bore 25 meets a bore 26 which leads through the mounting plate 21 to the outside to a T-piece 24, the two legs of which are supplied with supplies for hydrogen or oxygen via regulating needle valves 2B and 29.

21ηο Th vwn ^ n yffpj ^^ fff n ^ n Q yt / iiwyi ^ T ig-t in dor borehole Located within the burner basls imA consists of a hollow cylinder-shaped flame tip element 31 »a brass sleeve 32 \ ν> Λ a fa ^ hH * yl ün ^ r A ffc-h ct> 1-Iutter 331 which forms a sample guiding elomont · The hollow cylindrical Flamospitzonelement 31 is nested at one end in the lower end of the bore 24 'in the burner basl 23, whereby the Flammepltzenelement is gripped by the ring-shaped hoof in turn downwards against the lower wall of the in yf pltzenolomentefl 31 ^1WU * die "foim f w ^ der

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Brexmer base 23 with the hollow cylinder tube guide element 33 gedrUoIrb vrlrd that goes into the bore of the burner base is screwed in. Its bore 34 leads through the burner base 23 from its lower end, and this bore meets with a hole 34 * in the base 21 »ve it establishes a connection with a line 35, which serves as the sample entrance. The bore 34 leads into the annular chamber 36 between the inner wall of the sample guide 33 and the outer wall of the flame tip element 31 is formed. The sample guide 33 is provided with notches 33 'in the threaded inner end to provide a good access from the bore 34 to the annular chamber 36 create·

Iq operation will be co? Hydrogen as Bronnstoff gas and the combustible gas, for example oxygen, via the needle valve controls 28 and 29 are admitted into the flow passage 27, where they are mixed and then brought into the bore 26 in the assembly basl, then they flow up through the central Bore of the tip element 31 up to the edge of the tip element, before the gases are ignited with a suitable flame tinder 14 to form the flame rich in water. The sample including the support from the chromatographic column is introduced through the bore 34 in the lower end of the burner base 23 and flows around the upper part of the sleeve 32 into the chamber 36 which surrounds the flame tip 31. The sample is then directed with the sample guide 33 into the itafan area of the reducing flame, ie the hydrogen-rich area of low temperature. The temperature of this area is in the order of 400 ⁰ C, Sm difference to the temperature in Oxydationsbereich dor flame in the order of 1700 ⁰ C. Vährend the combustion is optimal from the substances of interest in this vasserstoffreichen range of 400 ⁰ C "to create a good Llohtemlssion get here to be

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the undesirable interfering substances, such as hydrocarbons, are not effectively burned. The disturbing ones Light emissions are therefore at a rolctiv low Held up

The photospectrometer unit 12 consists of a conventional one Photo pre-multiplier 41, a light filter 42 and a Explosion protection 43 and is above the burner unit and. arranged axially aligned with this »so that sioh a full forehead view of the flame shows. It is worth mentioning "that the combustion area can also be viewed from the side" as is the case with conventional ones Forms of flame photomatrle detectors is common; the advantage »that disturbing emissions are reduced due to the better burner construction is still retained.

In Fig. 5 two curves are shown which give the answer of the flame photometry detector in Ampdre for a known Embodiment of a detector (curve A) and a detector with a heater according to the invention (curve B) shows "which are obtained with different" constant levels of sulfur dioxide "which are burned as a sample will. The answer for the detector described earlier is stronger »but a higher noise level was also obtained» so that the actual finding- ' possible (net detectivity) for the two devices is approximately the same, while the known detector A, however shows a limit of the dynamic range at about 20 ppm. The detector described here has a dynamic one Range »at least up to 50 ppm ·

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Claims (4)

Claims M. The method of Flammphotometrle for detecting the presence of selected substances in bucket sample viewed at the eino burning sample with a spectrophotometer ι rtftfliirch geke nnzei chnet "that a fuel gas mixed with a verbrennungef-promoting gas, and this gas mixture is supplied to a Verbrennungsberoich" where the gases are burned to create a reducing flame »and the sample is brought into the utafang area of the resulting flame, where it is burned · 2. The method according to claim 1, characterized in that the fuel gas is hydrogen and the gas mixture is hydrogen-rich 3. Procedure according to .Anspruch ^ r flflflVflPfifa ffl * lfifflnfl? ItffhttfTifi the coating from a hydrogen-rich mixture Is composed of hydrogen and oxygen. 4. Flammphotometrle detector for performing the method according to claim 1, 2 or 3 »consisting of a burner device and a photodetector device which responds to Photoemisslon from the burning sample. thereby jgelc ennz ffi * r> hn # t ^ fl ff fl die has a first passage with which a mixture of the fuel gas with the combustion-promoting gas is delivered in a flame tip »where the combustion a reducing flame forms, and a second passage. which is separated from the first passage. to deliver the sample to the reducing fluff collection area. 5 x detector according to claim 4 »characterized gekennzf HiftFfflMfi that 309839/0867 _Jk9 the burner device has a flame tip element, that forms a flame tip in one Eude and a ereto passage has »the one to the end of the faucet and that the second passage outside the FlaiiaspltzeneleBentee is formed. 6 · Detector according to claim 5, characterized in that the burner device has a Frobon guide element "which surrounds the flange tip area of the flaODspit element and forms the necessary passage for the sample" which leads to the containment area of the flame. 7 · Detector according to one of Claims 1 to 6, characterized in that the optical axis of the photodetector lies parallel to the axis of the flame and is aligned with it. 309839/0867 Blank page