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WO2006000099A1 - Detecteur a flamme et procede de chromatographie gazeuse - Google Patents

Detecteur a flamme et procede de chromatographie gazeuse Download PDF

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Publication number
WO2006000099A1
WO2006000099A1 PCT/CA2005/001004 CA2005001004W WO2006000099A1 WO 2006000099 A1 WO2006000099 A1 WO 2006000099A1 CA 2005001004 W CA2005001004 W CA 2005001004W WO 2006000099 A1 WO2006000099 A1 WO 2006000099A1
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WO
WIPO (PCT)
Prior art keywords
flame
hydrogen
micro
detector
oxygen
Prior art date
Application number
PCT/CA2005/001004
Other languages
English (en)
Inventor
Kevin B. Thurbide
Original Assignee
Uti Limited Partnership
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
Priority claimed from CA002489073A external-priority patent/CA2489073A1/fr
Application filed by Uti Limited Partnership filed Critical Uti Limited Partnership
Publication of WO2006000099A1 publication Critical patent/WO2006000099A1/fr

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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
    • G01N30/62—Detectors specially adapted therefor
    • G01N30/64—Electrical detectors
    • G01N30/68—Flame ionisation detectors

Definitions

  • the method employs low gas flows to support a high energy premixed flame (about 3 mm tall x 1 mm wide) that can perform atomic emission/hydrocarbon ionization detection on the surface of a micro-analytical chip.
  • the flame photometric detector (FPD) is a widely used GC sensor for determining sulfur, phosphorus, tin, and other elements in volatile organic compounds based on their chemiluminescence within a low-temperature, hydrogen-rich flame.
  • micro-Flame Photometric Detector ⁇ FPD
  • ⁇ FPD micro-Flame Photometric Detector
  • the dimensions and qualities of the micro counter-current flame indicated that it could be a potentially useful method of producing chemiluminescent molecular emission, similar to a conventional FPD, within small channels and analytical devices of reduced proportions.
  • the primary disadvantage to the micro-flame method was the relatively large detection limits that it produced for sulfur and phosphorus due to an elevated background emission.
  • the spectrum, intensity, and orange appearance of the emission indicated that the fused silica capillary burner was glowing from contact with the flame. Despite efforts to prevent this it was observed under all conditions investigated.
  • a ⁇ FPD device with enhanced response by removing interference from an elevated background emission.
  • a ⁇ FPD flame detector is provided with similar performance to a conventional FPD flame, even though the two differ in size by about 3 orders of magnitude. Further, a flame detector is provided with photometric tin response and flame ionization response.
  • an improved ⁇ FPD response that is obtained by using a metallic capillary burner to support a micro counter-current flame, as for example a stainless steel capillary burner.
  • the ⁇ FPD has satisfactory response for many elements such as sulfur, phosphorus, and tin.
  • the micro counter-current flame detector produces a satisfactory ionization response toward carbon.
  • the ⁇ FPD as discussed herein is convenient for use in chemical weapons detection, sulfur measurements in, for example, oil and gas or pulp and paper, measuring amounts of H 2 S or SO 2 in the environment, analyzing pesticides containing sulfur, phosphorus, and other elements, performing general gas analysis for hydrocarbons present, or detecting other elements such as transition metals and main group elements such as selenium, tin, lead, tellurium, and halogens such as chlorine or bromine.
  • a micro-flame photometric detector comprising a housing having a flame detection port, an oxygen inlet, a hydrogen inlet, an analyte port and a flame region, a metal capillary for delivering oxygen through the oxygen inlet to the flame region, the metal capillary having a melting point sufficiently high that glow emissions from the metal capillary during flame detection does not significantly interfere with detection, a hydrogen and analyte delivery system for delivering hydrogen and analyte to the flame region; and a photo-detector arranged to detect flame emission through the flame detection port.
  • a method of detecting an analyte using a micro-flame photometric detector comprising the steps of: stabilizing a flame on the end of a metal capillary arranged for delivering oxygen to a flame region of the micro-flame photometric detector in the presence of hydrogen, the metal capillary having a melting point sufficiently high that glow emissions from the metal capillary during flame detection does not significantly interfere with detection; and detecting the flame emission through a port of the micro-flame photometric detector.
  • FIG. IA is a schematic view of a micro-counter-current flame detector according to the invention
  • Fig. IB is a detail of the tip of the burner of Fig. IA showing a flame
  • Fig. 3 is a chromatogram illustrating the ⁇ FPD response toward tin as tetramethyl tin, where from left to right the amounts injected are 0.1, 1, 10, 100, and 1000 pg respectively, which correspond to the peaks indicated by the arrows; Fig.
  • FIG. 4 shows ⁇ FID response of the micro counter-current flame toward carbon as decane ( ⁇ ) and benzene (O), for which the gas flows used are 7 mL/min oxygen and 40 mL/min hydrogen;
  • Fig. 5 shows chromatograms of an unleaded gasoline as monitored (from top to bottom) in the ⁇ FID mode, the ⁇ FPD mode without an interference filter, the ⁇ FPD phosphorus mode using a 520 nm (11 nm b.p.) interference filter, and the ⁇ FPD sulfur mode using a 393 nm (1 1 nm b.p.) interference filter (The sample is diluted 1 :10 in hexane.
  • Injection volume is 0.5 ⁇ L and also contains 500 ng each of tetrahydrothiophene and trimethyl phosphite.
  • the gas flows used are 7 mL/min oxygen and 45 mL/min hydrogen.); and Fig. 6 shows gas flows for a hydrogen/air and a hydrogen/oxygen microflame.
  • a flame photometric detector is considered to be a micro-flame photometric detector, or ⁇ FPD, if the flame volume, as defined by the visible boundary of the flame, is less than 1 ⁇ L (Ix 10 "6 L), which for example is satisfied by spherical flame diameters of less than 1 mm.
  • ⁇ FPD micro-flame photometric detector
  • FIG. IA presents a simplified schematic illustration of a micro counter-current flame arrangement according to an embodiment of the invention.
  • Fig. IB shows a detail of the flame region of the ⁇ FPD.
  • a housing 10 is conveniently made from a stainless steel VA" cross union (SwagelokTM) that encloses the micro-flame. The cross design permits monitoring of the flame.
  • the bottom 12 of the housing 10 is connected to a 10 cm length of stainless steel tubing 22 (1/16" o.d.) for the supply of hydrogen to the flame region 40 at the center of the housing 10.
  • the housing 10 is secured via a union adaptor to a tube stub 16 (1/4" o.d.) that fits an FID detector base 18 of a Gas Chromatograph instrument (GC Shimadzu model GC-8A).
  • GC Shimadzu model GC-8A Gas Chromatograph instrument
  • Hydrogen is introduced from a suitable source (not shown) and suitable ferrules such as VespelTM ferrules are used to connect the hydrogen supply tubing 22 to, but prevent its direct contact with, the GC instrument or detector housing in order to maintain proper FID operation.
  • suitable ferrules such as VespelTM ferrules are used to connect the hydrogen supply tubing 22 to, but prevent its direct contact with, the GC instrument or detector housing in order to maintain proper FID operation.
  • a ferrule situated within the tube stub 16 is suitable for securing the tubing 22.
  • One of the horizontal ports, such as port 24, of the housing 10 is used to visually align and monitor the micro-flame.
  • the other horizontal port 26 is adapted with a threaded stainless steel tube 28 that encases a quartz light guide 30 (150 mm x 6 mm o.d.) which directs the flame emission to a photomultiplier tube 32 (R 268 with wavelength range 300-650 nm; Hamamatsu, Bridgewater, NJ, USA).
  • a quartz capillary sleeve 33 (0.9 mm i.d.) extends vertically from bottom port 12 through to top port 36. In the lower port 12, the capillary sleeve 33 surrounds the hydrogen sleeve 22 and a capillary GC column 20.
  • the capillary sleeve 33 conducts the hydrogen and column effluent (analyte plus carrier) from capillary sleeve 22 towards the flame 42.
  • a septum 34 in the top port 36 a length of stainless steel capillary tubing 38 (0.01" i.d. x 0.018" o.d.) carrying oxygen extends downward into the quartz sleeve 33 to the center 40 of the union 10, directly in front of both the light guide port 26 and the viewing port 24.
  • the micro-flame 40 is situated on the end of this oxygen capillary 38 burning 'upside down' within a counter flowing stream of hydrogen and column effluent from the bottom.
  • the arrangement for delivering hydrogen and analyte may be varied considerably from what is described here.
  • a tube in tube arrangement with hydrogen in the annulus between the tubes may be used as described here.
  • hydrogen may be supplied through a capillary column 20 along with the analyte.
  • the separation column 20 employed is an EC-5 ((5% Phenyl)-95% Methylpolysiloxane) megabore column (30 mm x 0.53 mm i.d.; 1.00 ⁇ m thickness; Alltech, Deerfield, IL, U.S.A.) that extends vertically upward from the GC instrument and into the detector housing 10 through the connecting stainless steel tube 22 carrying the hydrogen.
  • Typical separations employ 5 mL/min of helium as the carrier gas. Normally, about 2-3 mm separates the end of the column 20 from the oxygen burner 38.
  • electrical leads from a Shimadzu GC are used such that the polarizer 44 of the GC is connected to the stainless steel oxygen burner 38 and the collector 46 is connected to the stainless steel hydrogen tube 22 surrounding the separation column 20.
  • High purity helium, hydrogen, and oxygen may be obtained from any suitable source such as Praxair. Tetrahydrothiophene (99%), trimethyl phosphite (99%), benzene (99%), decane (99%), and tetramethyl tin (95%) are obtained from any suitable source, such as Aldrich.
  • Stainless steel is an improvement over fused silica because it has a higher heat capacity. As such, the heat of the flame does not cause it to glow from being incandecently heated. Glowing creates a large background response in the detector, which decreases its sensitivity.
  • the improvement offered by stainless steel include improved detection limits and the simultaneous FID method and allow the method to be useful in more situations.
  • the flame could also be supported on other metals that have a sufficiently high melting point, such as nickel, or some alloys. Typical flame volume for the stainless steel example given here was about 30 nL. 15
  • the flame 40 is lit by introducing hydrogen, and igniting the flame as a diffusion flame at the top of the chimney.
  • the lower hydrogen limit measured was 6 mL min "1 using 2 mL min "1 of oxygen (point E) while the upper hydrogen limit measured was 113 mL min "1 using 5 mL min '1 of oxygen (point F).
  • point E the lowest gas flows that describe point E yield the lowest relative background emission observable. This is also considerably lower than the background emission observed for the lowest hydrogen/air flame gas flow setting.
  • the hydrogen/oxygen flame displays excellent stability under all of the conditions tested. This is also noted by its extraordinary capacity to withstand solvent injections tested up to 10 ⁇ L. As well, visually it appears much more compact in size and precisely centered in the viewing area.
  • the hydrogen/oxygen micro-flame provides the best properties in terms of stability and background emission, and the optimal flow region for operation is found to be in the area of 6 mL min "1 of hydrogen and 2 mL min "1 of oxygen. It should be noted that this flow region did not display any signs of flame instability and was typically operated daily for over 8 h with no degradation in performance. Lower gas flows than 6 mL min "1 of hydrogen and 2 mL min "1 of oxygen are also believed to be provide flame stability.
  • Burner Characteristics 18 Stainless steel capillary tubing of both 0.01" i.d. and 0.005" i.d. was investigated for its properties as a ⁇ FPD burner 38.
  • these dimensions are the same as and smaller than the fused silica tubing i.d. used previously. It was found that both tubing sizes were able to support a stable flame. However, the 0.005" i.d. (0.009" o.d.) tubing was observed to glow considerably, yielding a similar background emission to that noted earlier for the fused silica burner. In terms of relative wall thickness, this capillary burner (0.002") was slightly smaller compared to the fused silica tubing (0.003") used originally. 19 In contrast to this, when trials were run using the 0.01" i.d.
  • this stainless steel capillary tubing provides a more effective burner for the ⁇ FPD and was used in experiments described herein.
  • Photometric Response of Sulfur and Phosphorus 20 Similar to earlier efforts using a fused silica burner, the best ⁇ FPD signal to noise ratios in this study are also generally found at lower flows of oxygen and hydrogen, the former having a much more significant impact on the background emission.
  • the optimum ⁇ FPD response for sulfur was obtained with 7 mL/min of oxygen and 45 mL/min of hydrogen, while that for phosphorus was obtained when using 9 mL/min of oxygen and 58 mL/min of hydrogen.
  • the quadratic response toward sulfur spans over 3.5 orders of magnitude down to a minimum detectable limit of 3x10 " " gS/s. This value is determined at the conventional signal to noise ratio of 2, where noise is measured as the peak to peak fluctuations of the baseline over at least 10 analyte peak base widths.
  • the ⁇ FPD response is linear over 5 orders of magnitude down to a minimum detectable elemental flow of 3xlO "12 gP/s.
  • Fig. 2 also includes the response toward different flows of carbon (as both decane and benzene) obtained under optimal sulfur and phosphorus conditions in the ⁇ FPD.
  • the sensitivity between benzene and decane differs very little in each mode. While this is reasonable, it is necessary to examine since it has been demonstrated previously that aromatic compounds can respond considerably stronger than aliphatic compounds under certain FPD conditions.
  • the carbon response displayed in Fig. 2 increases by a factor of 6 from the phosphorus to the sulfur mode.
  • phosphorus in the ⁇ FPD yields a molar selectivity over carbon (i.e. mole P/mole C that yield the same response within the linear range) of 5 orders of magnitude.
  • sulfur produces a molar selectivity over carbon of 3.5 orders of magnitude near the upper response limit, which narrows as analyte amounts decrease.
  • Narrow band interference filters are often used to selectively monitor sulfur or phosphorus response in the conventional FPD, although this practice is known to decrease sensitivity. Since these methods were equally effective in the ⁇ FPD with a fused silica capillary burner, no differences in behavior of the narrow band interference filters were anticipated or observed from using stainless steel instead. For example, when the S 2 * emission of sulfur is isolated and monitored near 400 nm, the ⁇ FPD sensitivity for this element typically decreases by a factor of 2 to 10 times depending on the filter used. Comparable results are also obtained when observing the HPO* emission of phosphorus near 526 nm. Selective monitoring of sulfur and phosphorus using suitable interference filters with the ⁇ FPD is demonstrated later in this study.
  • Table 2 displays the results and clearly indicates that as the amount of co-eluting acetone approaches 1 ⁇ L, the sulfur response reduces to approximately 30% of that which occurred without any acetone present.
  • This amount of acetone corresponds to about 60 ⁇ g s "1 of carbon flow in the detector, which agrees with the mass flow of carbon observed to induce sulfur response quenching in a conventional FPD.
  • sulfur response quenching due to co-eluting hydrocarbons does occur in the micro-FPD and this effect appears to only be significant for carbon flows in the microgram range. 25
  • the setup used also helps avoid false positives and avoids carbon influencing the results.
  • the simultaneous FID mode helps to identify large amounts of material as opposed to strongly responding sulfur or phosphorus compounds.
  • Photometric Response of Tin 26 Tin is another element commonly monitored by a conventional FPD, normally producing a red and/or blue chemiluminescence in the detector.
  • FPD Fluorescence-Activated Device
  • tin response has not been examined in the ⁇ FPD or in the larger counter-current flame.
  • quartz sleeves contaminated with traces of tin were visually observed to yield an intense blue emission on the surface of the enclosure surrounding the flame. This same luminescence is also observed in the form of tailing peaks when picogram quantities of tetramethyl tin are introduced into the detector equipped with a regular clean quartz capillary sleeve.
  • tetramethyl tin this is observed between approximately 0.1 and 1 pg of the injected compound.
  • This narrow linear range also reproduces with other calibration standards such as tetrabutyl tin, and under a variety of gas flows investigated.
  • Fig. 3 illustrates this for a 0.1, 1, 10, 100, and 1000 picogram injection of tetramethyl tin under the same optimal ⁇ FPD condition.
  • peak heights do not appreciably increase for this mass range, it is observed occasionally that the peak widths sometimes do.
  • micro counter-current flame provides photometric response that is similar to its larger analogue, it was somewhat anticipated that it too might also deliver useful ionization response toward carbon.
  • fuel-rich hydrogen radical flame chemistry that supports photometric signals is unique from the air-rich oxygen radical flame chemistry that promotes hydrocarbon ionization. Since the effect of reducing counter-current flame size on these processes remains unclear, it is therefore necessary to establish and investigate the extent of FID response that can be derived from the ⁇ FPD flame. This information is also potentially beneficial since such a feature could be useful in applications where both universal and selective detection of samples is desired. 29 Fortunately, this is facilitated by using a stainless steel capillary burner 38 in the ⁇ FPD, which makes it very convenient to apply a potential across the flame.
  • the FID flame normally operates in a diffusion mode where hydrogen and column effluent are introduced through a central burner supporting the flame, which is concentrically surrounded by an excess of oxygen [HiIl].
  • the ⁇ FID flame operates in the unique counter-current mode, where it is supported on a capillary delivering oxygen, and burns in a counter-flowing excess of hydrogen mixed with column effluent.
  • the analyte, immersed in hydrogen is directed toward the counter-current flame's oxygen-rich inner cone through its hydrogen-rich outer mantle.
  • This is opposed to the conventional FID where analytes, also immersed in hydrogen, enter the oxygen-rich outer mantle of the flame through its hydrogen-rich inner cone region.
  • Fig. 4 demonstrates the ⁇ FID sensitivity toward carbon as both decane and benzene under optimum conditions.
  • the response of the two compounds agrees within a factor of 2, and increases linearly over 5 orders of magnitude yielding a detection limit of 2x10 " ' gC/s.
  • the ⁇ FID produces a response of about 5 milliCoulombs/gC.
  • Table 1 illustrates the relative change in the ⁇ FPD sulfur signal when using gas flows optimized for obtaining photometric sulfur, photometric phosphorus, and hydrocarbon ionization response from the flame. Also included is a similar set of data illustrating the relative change in the ⁇ FPD phosphorus signal in each of these three operating modes. As can be seen from the table, the ⁇ FPD sensitivity for sulfur and for phosphorus changes relatively little amongst the different settings. The sulfur signal is decreased by only 4% when operated in the photometric phosphorus mode, and by 10% when operated in the hydrocarbon ionization mode. By comparison, the phosphorus signal is decreased by 15% when operated in the photometric sulfur mode.
  • the ⁇ FID response toward carbon displays the chromatographic profile of the gasoline sample as monitored (from top to bottom) by the ⁇ FID response toward carbon, the ⁇ FPD response without an interference filter, the ⁇ FPD response toward phosphorus at 520 nm, and the ⁇ FPD response toward sulfur at 393 nm.
  • the ⁇ FID response was found to be least compromised and maintained 90% of its optimal sensitivity.
  • the ⁇ FID trace shows several partially separated peaks illustrating the primary hydrocarbon components of the sample, while in the ⁇ FPD trace below only those peaks containing sulfur and phosphorus are dominant. It should be mentioned that while other sulfur or phosphorus peaks may have been present amongst the main hydrocarbon components of the sample, it is possible that quenching of their ⁇ FPD emissions may have occurred. For instance, emission quenching by co-eluting hydrocarbons is widely observed in the conventional FPD [Dressier]. Similarly, it has also been shown to reduce ⁇ FPD response by nearly 70 % when carbon flows of 60 ⁇ g/s or greater are present in the detector [K.B. Thurbide, CD. Anderson, Analyst 128 (2003) 616]. 38 Fig.
  • FIG. 5 also demonstrates the ⁇ FPD traces which selectivity monitor the HPO* emission of phosphorus, and the S 2 * emission of sulfur at specific wavelengths using an appropriate interference filter. Note that the peak for trimethyl phosphite appears somewhat sharper than in the earlier work, which was performed 'on-column' at lower temperatures when using hydrogen as the carrier gas [Thurbide 2003]. Similar to previous studies, the phosphorus trace additionally yields a minor contribution from sulfur due to the well-known extension of S 2 * emission bands above 500 nm. Thus, Fig. 5 shows that information qualitatively similar to a conventional FID and a conventional FPD can also be obtained in two dimensions from the same micro counter- current flame.
  • the attributes of this method demonstrate that the hydrogen-rich micro counter- current flame is indeed capable of delivering useful, sensitive response toward organic analytes. In spite of its very small size, it yields selective chemiluminescent and universal hydrocarbon ionization response that is similar in quantity and quality to those of conventional flame based detectors. As well, since it can deliver this as a multi-dimensional response under a common set of conditions, the micro counter-current flame method allows for more information to be obtained from a sample analysis. The properties and dimensions of the micro counter-current flame may therefore be potentially useful for application to analytical devices of reduced proportions.
  • the method can support a stable hydrogen-rich micro-flame within a small channel, it may be beneficial for portable or miniature GC methods where the performance of a conventional FPD and/or FID in an enclosed micro format is desirable.
  • the apparatus and method disclosed here should also act as a useful flame source to support and adapt other micro-flame based detection methods such as Alkali Flame Detection.
  • the apparatus and method disclosed also have utility in refinery and hydrocarbon processing plants for example in online applications.
  • Solvent Original sulfur Injected/ ⁇ L Signal (%) 0.0 100 0.2 99 0.5 96 1.0 33 a Injected as ethyl sulfide; monitored using a 400 nm wide band colored glass filter (100 nm bandpass). b Peak separation is 10 s.

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Abstract

L'invention concerne un microdétecteur à flamme en contre-courant assurant la double détection de photométrie et d'ionisation pour la chromatographie gazeuse. Dans le détecteur, un capillaire en acier inoxydable (0.01 i.d.) fournit de l'oxygène comme brûleur, lequel assure une flamme compacte brûlant dans un excès d'hydrogène à contre-courant. En mode de réponse de microdétecteur à photométrie de flamme (µFPD), le niveau d'émission de fond est réduit de plus d'un ordre de grandeur par rapport aux expériences antérieures reposant sur un brûleur à capillaire en silice fondue, ce qui donne des limites de détection largement améliorées. Le dispositif peut être utilisé avec succès comme détecteur sélectif et universel dans la chromatographie gazeuse. Les résultats montrent que ce procédé de détection à flamme en contre-courant offre une performance comparable à celle des détecteurs à photométrie et ionisation de flamme.
PCT/CA2005/001004 2004-06-25 2005-06-27 Detecteur a flamme et procede de chromatographie gazeuse WO2006000099A1 (fr)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
US58254904P 2004-06-25 2004-06-25
US60/582,549 2004-06-25
US11/019,107 2004-12-22
CA002489073A CA2489073A1 (fr) 2004-06-25 2004-12-22 Detecteur de microflamme et methode de chromatographie gazeuse
US11/019,107 US20050287033A1 (en) 2004-06-25 2004-12-22 Micro flame detector and method for gas chromatography
CA2,489,073 2004-12-22

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102680454A (zh) * 2011-09-20 2012-09-19 深圳市爱诺实业有限公司 二阶微分火焰发射光谱仪
US8305086B2 (en) 2007-09-13 2012-11-06 Bayer Technology Services Gmbh Flame ionization detector
US12263068B2 (en) 2009-08-27 2025-04-01 The Procter & Gamble Company Absorbent article having a multi-component visual signal

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4234257A (en) * 1979-01-15 1980-11-18 Process Analyzers, Inc. Flame photometric detector adapted for use in hydrocarbon streams
CA1093341A (fr) * 1977-02-28 1981-01-13 Paul L. Patterson Bruleur double-flamme pour detection photometrique de flamme

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA1093341A (fr) * 1977-02-28 1981-01-13 Paul L. Patterson Bruleur double-flamme pour detection photometrique de flamme
US4234257A (en) * 1979-01-15 1980-11-18 Process Analyzers, Inc. Flame photometric detector adapted for use in hydrocarbon streams

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
THURBIDE ET AL: "FLAME PHOTOMETRIC DETECTION INSIDE OF A CAPILLARY GAS CHROMATOGRAPHY COLUMN.", THE ANALYST., vol. 128, no. 6, 2003, pages 616 - 622 *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8305086B2 (en) 2007-09-13 2012-11-06 Bayer Technology Services Gmbh Flame ionization detector
US12263068B2 (en) 2009-08-27 2025-04-01 The Procter & Gamble Company Absorbent article having a multi-component visual signal
CN102680454A (zh) * 2011-09-20 2012-09-19 深圳市爱诺实业有限公司 二阶微分火焰发射光谱仪
CN102680454B (zh) * 2011-09-20 2014-06-18 深圳市爱诺实业有限公司 二阶微分火焰发射光谱仪

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