US3714813A - Apparatus for stabilizing component elution times in gas chromatographs - Google Patents

Apparatus for stabilizing component elution times in gas chromatographs Download PDF

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Publication number
US3714813A
US3714813A US00105893A US3714813DA US3714813A US 3714813 A US3714813 A US 3714813A US 00105893 A US00105893 A US 00105893A US 3714813D A US3714813D A US 3714813DA US 3714813 A US3714813 A US 3714813A
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United States
Prior art keywords
peak
amplitude
amplifier
polarity
signal
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Expired - Lifetime
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US00105893A
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English (en)
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F Martin
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Dow Chemical Co
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Dow Chemical Co
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    • 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
    • G01N30/86—Signal analysis
    • G01N30/8624—Detection of slopes or peaks; baseline correction
    • 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
    • G01N30/86—Signal analysis
    • G01N30/8665—Signal analysis for calibrating the measuring apparatus
    • G01N30/8668—Signal analysis for calibrating the measuring apparatus using retention times
    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06G—ANALOGUE COMPUTERS
    • G06G7/00—Devices in which the computing operation is performed by varying electric or magnetic quantities
    • G06G7/48—Analogue computers for specific processes, systems or devices, e.g. simulators
    • G06G7/75—Analogue computers for specific processes, systems or devices, e.g. simulators for component analysis, e.g. of mixtures, of colours
    • 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
    • G01N30/86—Signal analysis
    • G01N30/8624—Detection of slopes or peaks; baseline correction
    • G01N30/8627—Slopes

Definitions

  • ABSTRACT A peak stabilizer in accordance with this invention controls the peak retention time during an analysis, by gas chromatograph, for example, so that this time will be the same for all determinations. This allows a peak to be gated or picked for process control or read-out without the undesirable possibility that it would drift beyond the time limits of the gate. If a peak in the chromatogram, for example, is sampled on the leading and trailing slopes at predetermined times, a comparison of these voltages will indicate if the peak is early, late or at its right time. The carrier gas flow or other rate control parameter may be automatically changed to bring the peak back to the proper retention time.
  • a principal object of this invention is to provide improved apparatus for stabilizing peak retention times in the output signal of an analytical instrument.
  • Another object of this invention is to provide improved apparatus for use with a gas chromatograph to stabilize peak retention time.
  • a peak in the chromatogram is sampled on the leading and trailing slopes at predetermined times, these voltages, when compared, will provide an output which is neutral, negative or positive and thus indicate if the peak is at its right time, is early or is late.
  • the carrier gas flow may be automatically changed to bring the peak back to the proper retention time in accordance with the polarity and magnitude of the output of the apparatus.
  • FIG. 1 is a diagrammatic view of apparatus in accordance with this invention.
  • FIG. 2 is a representation of output peaks of an analytical instrument which is used to illustrate the operation of the apparatus of FIG. 1.
  • Peak D meets these requirements.
  • Operation may be understood by following the circuit in FIG. 1.
  • the sequence is controlled by a timer 110 that operates switches 12, 14,98, and 100 and is initiated by a master timer (not shown).
  • the output voltage E of gas chromatograph is sampled at time X (FIG. 2) by closing contact F on switch 12 for a short period of time.
  • This value is stored by the hold amplifier 28 which has inverted polarity diodes 22, 24 coupled across its input positive and negative inputs.
  • the input value from contact F is applied to the positive input of amplifier 28.
  • Capacitor l8 and resistor 26 are coupled between ground and the positive and negative inputs, respectively, of amplifier 28.
  • the output voltage E is sampled at time Y (see FIG. 2) by closing contact G of switch 14.
  • amplifier 42 which is similar to amplifier 28.
  • the two values of E at times X and Y are compared by amplifier 54.
  • Amplifiers 42 and 54 each have inverted diodes 38,40 and 50,52 respectively, connected in parallel across their positive and negative inputs.
  • Amplifier 42 has a capacitor 20 and resistor 66 connected across its inputs and to ground 16 the same as capacitor 18 and resistor 26 are connected to amplifier 28.
  • Amplifiers 28 and 42 each have a resistor 30,44 respectively coupled between its output and ground and a feed back resistor 36,46 respectively coupled between its output and'negative input.
  • the output of amplifier 28 is coupled through resistor 32 and contact 34 of switch S to the negative input of amplifier 54, while the output of amplifier 42 is coupled through resistor 48 to the positive input of amplifier 54. Feed back from the output of amplifier 54 to its negative input is accomplished through resistor 36.
  • An internal trim adjustment composed of resistor 64 and variable resistor having a movable contact 62 is shown coupled to the amplifier 54. Similar trim adjustments, not shown, may be provided for amplifiers 28 and 42.
  • the output of amplifier 54 is coupled to the base of transistors 102, 104 whose emitters are coupled through resistors 106, 107, respectively, to ground.
  • the collector of transistor 102 is coupled to a negative voltage through relay coil 72 which controls the opening and closing of switch 74.
  • the collector of transistor 104 is coupled to a positive voltage source through relay coil 109 which controls the opening and closing of switch 84.
  • a part of the output of amplifier 54 is coupled from the movable contact 58 of variable resistor 56 to the bases of transistors 108, 86 whose emitters are coupled to ground through resistors 75,90, respectively.
  • the collectors of transistors 108,86 are coupled respectively to negative and positive voltage sources through relay coils 68,78 which control the opening and closing of switches 70,80 respectively.
  • Switches 70,80 are connected in parallel with switches 74,84, respectively.
  • a reversible electric motor 96 has the junction of its two windings coupled to one side of a suitable AC. power source.
  • the other side of the AC. power source is coupled, respectively, through switches 98, 100, 80, 84 or 98, 100, 70, 74 to an end of one of the windings of the motor 96 which is mechanically coupled to the valve 94 in the carrier fluid line feeding the gas chromatograph 10.
  • timer 110 which controls switches 12,14. 34, 98, 100 in suitable operating sequence.
  • the timer 1 l0 first closes switch 12 at F to couple the output of the chromatograph 10 to the amplifier to store the value of point X (FIG. 2) on peak D. The timer then couples the output of the chromatograph across switch 14 to amplifier 42 to store the value of point Y of peak D.
  • the switch 100 is closed for a shorter time than is switch 98, used for making so-called large timing corrections in carrier fluid flow through the chromatograph 10.
  • the output of amplifier 54 is either positive, negative or zero.
  • the appropriate relay switch 74 or.84 will be closed and, during the time the switch 100 is energized, the motor 96 will be energized to correct the flow of carrier fluid to the chromatograph 10 by a specific amount.
  • the switch 70 or 80 closes, allowing a larger correction to be made, since the switch 98 is closed for a longer time than is the switch 100.
  • the switch 34 when open, leaves one input to the amplifier 54 floating, effectively preventing any output from the amplifier 54 and possible energization of relays until the actual comparison of X and Y signals are to be made.
  • the switch S (34) could be eliminated if power economy were not desired.
  • values of previous X and Y signals dissipate so that the new signals are the result only of the new" X and Y values.
  • a system for stabilizing the peak retention time in fluid chromatographs comprising means including a capacitor and an amplifier for sequentially measuring and storing amplitude values at points along opposite slopes of a selected peak signal, signal comparison amplifier means for providing an output signal which is a function in amplitude and polarity of the difference between said stored values, means for applying said output signal to polarity and amplitude sensitive switching means, said switching means coupling a power source to reversible motor drive means, said drive means being coupled to a valve for controlling the flow of carrier fluid to said chromatograph as a function of the polarity and amplitude of said signal.
  • timer means controls the time interval during which said drive means may be actuated.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Immunology (AREA)
  • General Health & Medical Sciences (AREA)
  • Biochemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Pathology (AREA)
  • Health & Medical Sciences (AREA)
  • Computer Hardware Design (AREA)
  • Theoretical Computer Science (AREA)
  • Mathematical Physics (AREA)
  • Amplifiers (AREA)
  • Treatment Of Liquids With Adsorbents In General (AREA)
US00105893A 1971-01-12 1971-01-12 Apparatus for stabilizing component elution times in gas chromatographs Expired - Lifetime US3714813A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US10589371A 1971-01-12 1971-01-12

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US3714813A true US3714813A (en) 1973-02-06

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US (1) US3714813A (it)
BE (1) BE777952A (it)
DE (1) DE2200307A1 (it)
FR (1) FR2170310A5 (it)
IT (1) IT948155B (it)
NL (1) NL7200281A (it)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4150436A (en) * 1977-12-23 1979-04-17 Phillips Petroleum Company First order sample and hold
US4452067A (en) * 1982-08-30 1984-06-05 The Dow Chemical Company Apparatus for analysis of a vapor phase sample
CN113567604A (zh) * 2021-07-22 2021-10-29 华谱科仪(大连)科技有限公司 色谱谱图的检测分析方法及电子设备

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3069895A (en) * 1958-04-10 1962-12-25 Phillips Petroleum Co Chromatographic analyzer peak reader
US3245269A (en) * 1958-09-25 1966-04-12 James O Ivie Automatic sampling device
US3267264A (en) * 1962-02-20 1966-08-16 Phillips Petroleum Co Analysis apparatus using controlled logic circuitry

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3069895A (en) * 1958-04-10 1962-12-25 Phillips Petroleum Co Chromatographic analyzer peak reader
US3245269A (en) * 1958-09-25 1966-04-12 James O Ivie Automatic sampling device
US3267264A (en) * 1962-02-20 1966-08-16 Phillips Petroleum Co Analysis apparatus using controlled logic circuitry

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4150436A (en) * 1977-12-23 1979-04-17 Phillips Petroleum Company First order sample and hold
US4452067A (en) * 1982-08-30 1984-06-05 The Dow Chemical Company Apparatus for analysis of a vapor phase sample
CN113567604A (zh) * 2021-07-22 2021-10-29 华谱科仪(大连)科技有限公司 色谱谱图的检测分析方法及电子设备

Also Published As

Publication number Publication date
NL7200281A (it) 1972-07-14
DE2200307A1 (de) 1972-07-27
FR2170310A5 (it) 1973-09-14
IT948155B (it) 1973-05-30
BE777952A (fr) 1972-07-12

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