Agilent Technologies 7820A Advanced User's Manual
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Agilent Technologies 7820A Advanced User's Manual

Gas chromatograph
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Advanced User Guide
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  • Page 1 Agilent 7820A Gas Chromatograph Advanced User Guide Agilent Technologies...
  • Page 2 Shanghai 200131 P.R.China Limited Rights as defined in FAR 52.227-14 met. (June 1987) or DFAR 252.227-7015 (b)(2) (November 1995), as applicable in any Firmware Version technical data. This manual is written for 7820A GCs using firmware version A.01.18.

  • Page 3: Table Of Contents

    Contents Software Keypad Using the Software Keypad Programming Run Time Programming Using run time events Programming run time events The run table Adding events to the run table Editing events in the run table Deleting run time events Clock Time Programming Using clock time events Programming clock time events Adding events to the clock table...
  • Page 4 Selecting the correct S/SL inlet liner Vapor Volume Calculator Setting parameters for the S/SL split mode Selecting parameters for the S/SL splitless mode Setting parameters for the S/SL splitless mode Setting parameters for the S/SL pulsed modes About the Purged Packed Column Inlet Setting parameters About the Packed Column Inlet Adjusting parameters...
  • Page 5 Hydrogen Sensor Instrument logs Calibration Status information Operation with an Agilent data system Detectors About Makeup Gas About the FID How FID units are displayed in Agilent data systems and on the GC To light the FID flame To extinguish the FID flame FID automatic reignition (Lit offset) Recommended starting conditions for new FID methods Setting parameters for FID...
  • Page 6 Selecting an NPD jet To configure the NPD Automatically adjusting NPD bead voltage Setting NPD adjust offset on the clock table Aborting NPD adjust offset Extending the NPD bead life Setting the initial bead voltage for new beads Setting NPD bead voltage manually (optional) About the FPD linearity Lit Offset...
  • Page 7 Controlling a Valve From the keyboard From the run or clock time tables Gas sampling valve GC Output Signals About Signals Analog Signals Analog zero Analog range Analog data rates Selecting fast peaks (analog output) Digital Signals Digital zero Signal Freeze and Resume Data rates with Agilent data systems Zero Init Data Files Auxiliary Devices...
  • Page 8 Advanced User Guide...

  • Page 9: Software Keypad

    Agilent 7820A Gas Chromatograph Advanced User Guide Software Keypad Agilent Technologies...

  • Page 10: Using The Software Keypad

    Software Keypad Using the Software Keypad The Agilent software keypad (remote controller) provides the ability to program and use the 7820A Gas Chromatograph (GC). Refer to the Operating Guide for instructions for its installation and use. Figure 1 Software keypad (remote controller) All instructions in this manual assume the use of the software keypad unless otherwise noted.
  • Page 11 Agilent 7820A Gas Chromatograph Advanced User Guide Programming Run Time Programming Using run time events Programming run time events The run table Adding events to the run table Editing events in the run table Deleting run time events Clock Time Programming...

  • Page 12: Programming

    Programming Run Time Programming Run time programming during a method allows certain setpoints to change automatically during a run as a function of the chromatographic run time. Thus an event that is programmed to occur at 2 minutes will occur 2 minutes after every injection.

  • Page 13: Programming Run Time Events

    Programming Programming run time events Press [Run Table]. Press [Mode/Type] to see the available run time events. Scroll to the event to be programmed. Press [Enter]. Enter values for the Time: and the other parameter. Press [Enter] after each entry. Press [Mode/Type] to add another event.

  • Page 14: Editing Events In The Run Table

    Programming Editing events in the run table Press [Run Table]. Move the cursor to the event you want to change. To edit the time for an event, move the cursor to the line labeled Time:. Type the desired time and press [Enter]. To edit a setpoint value, scroll to the setpoint line.

  • Page 15: Clock Time Programming

    Programming Clock Time Programming Clock time programming allows certain setpoints to change automatically at a specified time during a 24-hour day. Thus, an event programmed to occur at 14:35 hours will occur at 2:35 in the afternoon. A running analysis or sequence has precedence over any clock table events occurring during this time.

  • Page 16: Editing Clock Time Events

    Programming Select the event type. Set appropriate parameters. Repeat this process until all entries are added. Editing clock time events Press [Clock Table] to view all events programmed. Scroll to the event you want to change. To edit the time for an event, move the cursor to the line labelled Time: and type the desired time.

  • Page 17: Post Run Programming

    Programming Post Run Programming This function can be used with both isothermal and programmed methods. Post run is a period that begins at the end of the normal run. The parameters include: • Time—How long is the post run period? •...
  • Page 18 Programming Advanced User Guide...

  • Page 19: Inlets

    Agilent 7820A Gas Chromatograph Advanced User Guide Inlets Using Hydrogen Inlet Overview Carrier Gas Flow Rates About Gas Saver Pre Run and Prep Run Auto Prep Run About the Split/Splitless Inlet Split/Splitless inlet split mode overview Split/Splitless inlet splitless mode overview...

  • Page 20: Using Hydrogen

    Inlets Using Hydrogen When using hydrogen (H ), as the carrier gas, be aware that WA RN IN G hydrogen (H ) gas can flow into the oven and create an explosion hazard. Therefore, be sure that the supply is off until all connections are made, and ensure that the inlet and detector column fittings are either connected to a column or capped at all times when hydrogen (H...

  • Page 21: Inlet Overview

    Inlets Inlet Overview Table 1 Comparing inlets Sample Sample Comments Inlet Column Mode concentration to column Split/splitless Capillary Split High Very little Pulsed split High Useful with large Very little injections Splitless Useful with large Pulsed splitless injections Purge packed Packed column Large capillary...

  • Page 22: Carrier Gas Flow Rates

    Inlets Carrier Gas Flow Rates The flow rates in Table 2 are recommended for all column temperatures. Table 2 Column size and carrier flow rate Column type Column size Carrier flow rate, mL/min Hydrogen Helium Nitrogen Packed 1/8-inch 1/4-inch Capillary 0.05 mm id 0.10 mm id 0.20 mm id...

  • Page 23: About Gas Saver

    Inlets About Gas Saver Gas saver is not supported on EPR (electronic pneumatics regulation) NO T E equipped GCs. Gas saver reduces carrier flow from the split vent after the sample is on the column. It applies to the Split/Splitless inlet (all modes).

  • Page 24: To Use Gas Saver

    Inlets To use gas saver Press [Front Inlet] or [Back Inlet]. Turn gas saver On. Set Gas saver flow. It must be at least 15 mL/min greater than the column flow. If in split mode, set Saver time after injection time. In all other modes, set after Purge time.

  • Page 25: Pre Run And Prep Run

    Inlets Pre Run and Prep Run With some inlets and operating modes, certain instrument setpoints are different between runs than during an analysis. To restore the setpoints for injection, you must place the GC into the Pre Run state. You must use the Pre Run state when: •...

  • Page 26: Auto Prep Run

    Inlets Auto Prep Run To set this parameter, usually for a non-Agilent integrator, workstation, or other controlling device: Press [Config] to view a list of configurable parameters. Scroll to Instrument and press [Enter]. Scroll to Auto prep run and press [On/Yes]. Advanced User Guide...

  • Page 27: About The Split/Splitless Inlet

    Inlets About the Split/Splitless Inlet This inlet is used for split, splitless, pulsed splitless, or pulsed split analyses. You can choose the operating mode from the inlet parameter list. The split mode is generally used for major component analyses, while the splitless mode is used for trace analyses.

  • Page 28: Standard S/Sl Inlet

    Inlets Standard S/SL inlet The standard split/splitless inlet is rated to 100 psi pressure at the inlet. It is appropriate for most columns. Recommended source pressure is 120 psi. Split/Splitless inlet split mode overview During a split injection, a liquid sample is introduced into a hot inlet where it vaporizes rapidly.

  • Page 29: Split/Splitless Inlet Splitless Mode Overview

    Inlets Carrier Supply Split Septum Purge 80 PSI EPC/EPR Module Frit Frit Valve Valve Split Vent Trap Inlet Weldment FS = Flow Sensor Column PS = Pressure Sensor Split/Splitless inlet splitless mode overview In this mode, the split vent valve is closed during the injection and remains so while the sample is vaporized in the liner and transferred to the column.

  • Page 30: The S/Sl Inlet Pulsed Split And Splitless Modes

    Inlets Split Carrier Supply Septum Purge 80 PSI EPC/EPR Module Frit Frit Valve Valve Split Vent Trap Inlet Weldment FS = Flow Sensor PS = Pressure Sensor Column The S/SL inlet pulsed split and splitless modes Pulsed split and pulsed splitless modes are not supported on EPR NO T E (electronic pneumatics regulation) equipped GCs.

  • Page 31: Split/Splitless Inlet Split Mode Minimum Operating Pressures

    Inlets You must press [Prep Run] before doing manual injections in the pressure pulse modes. See “Pre Run and Prep Run” on page 25 for details. You can do column pressure and flow programming when in the pressure pulse mode. However, the pressure pulse will take precedence over the column pressure or flow ramp.

  • Page 32: Selecting The Correct S/Sl Inlet Liner

    Inlets Table 3 Approximate minimum viable inlet pressures for split/splitless inlet in split mode, in psi (kPa) Split vent flow (mL/min) 50–100 100–200 200–400 400–600 Helium and hydrogen carrier gases Split liners - 5183-4647, 19251-60540 2.5 (17.2) 3.5 (24.1 4.5 (31) 6.0 (41.4) Splitless liners - 5062-3587, 5181-8818 4.0 (27.6)
  • Page 33 Inlets Splitless liner Pulsed split and pulsed splitless modes are not supported on EPR NO T E (electronic pneumatics regulation) equipped GCs. The liner volume must contain the solvent vapor. The liner should be deactivated to minimize sample breakdown during the purge delay.

  • Page 34: Vapor Volume Calculator

    Inlets Table 5 Splitless mode liners (continued) Liner Description Volume Mode Deactivated Part Number Single Taper 900 uL Splitless 5181-3316 4 mm Single Taper Direct column connect G1544-80730 4 mm Dual Taper Direct column connect G1544-80700 Vapor Volume Calculator Agilent provides a Vapor Volume Calculator to help you determine if a liner is suitable for a method.
  • Page 35 Inlets Septum Purge Flow, in mL/min, through the septum purge line. If all columns in the flow path are defined Press [Front Inlet] or [Back Inlet]. Scroll to Mode: and press [Mode/Type]. Select Split. Set the inlet temperature. The following two steps are not applicable to EPR equipped GCs with an NO T E S/SL inlet.

  • Page 36: Selecting Parameters For The S/Sl Splitless Mode

    Inlets Selecting parameters for the S/SL splitless mode A successful splitless injection consists of these steps: Vaporize the sample and solvent in a heated inlet. Use a low flow and low oven temperature to create a solvent-saturated zone at the head of the column. Use this zone to trap and reconcentrate the sample at the head of the column.
  • Page 37 Inlets There is no setpoint for the Pressure parameter in EPR (electronic NO T E pneumatics regulation) equipped GCs with an S/SL inlet. Pressure Actual and setpoint inlet pressure in psi, bar, or kPa Purge time The time, after the beginning of the run, when you want the purge valve to open.

  • Page 38: Setting Parameters For The S/Sl Pulsed Modes

    Inlets Press [Prep Run] (see “Pre Run and Prep Run” on page 25) before manually injecting a sample (this is automatic for Agilent ALS). If a column in the flow path is not defined Press [Front Inlet] or [Back Inlet]. Scroll to Mode: and press [Mode/Type].

  • Page 39: About The Purged Packed Column Inlet

    Inlets About the Purged Packed Column Inlet This inlet is used with packed columns when high-efficiency separations are not required. It can also be used with wide-bore capillary columns, if flows greater than 10 mL/min are acceptable. The inlet is flow controlled, regardless or whether or not the column is capillary and defined, or packed.

  • Page 40: Setting Parameters

    Inlets Setting parameters The inlet operates in flow control mode. While in flow control mode, you cannot enter pressures here. Temperature The setpoint and actual temperature values. Pressure The actual pressure (in psi, bar, or kPa) supplied to the inlet. You cannot enter a setpoint here. Total flow Enter your setpoint here, actual value is displayed.

  • Page 41: About The Packed Column Inlet

    Inlets About the Packed Column Inlet This inlet is used with packed columns when high-efficiency separations are not required. The inlet is flow controlled regardless of whether the column is defined or not. This inlet is available in EPR (electronic pneumatics regulation) equipped GCs only.

  • Page 42: Adjusting Parameters

    Inlets Adjusting parameters The inlet operates in flow control mode. You cannot enter pressures here. Temperature The setpoint and actual temperature values. Col flow Adjust using the 2/+ and 8/- keys on the virtual keypad, actual value is displayed. Advanced User Guide...

  • Page 43: About The Cool On-Column Inlet

    Inlets About the Cool On-Column Inlet This inlet introduces liquid sample directly onto a capillary column. To do this, both the inlet and the oven must be cool at injection, either at or below the boiling point of the solvent. Because the sample does not vaporize immediately in the inlet, problems with sample discrimination and sample alteration are minimized.

  • Page 44: Setup Modes Of The Coc Inlet

    Inlets Setup modes of the COC inlet The COC inlet hardware must be set up for one of three usages, depending on the type of injection and column size. • 0.25 mm or 0.32 mm automated on-column. Use predrilled septa. •...

  • Page 45: Setting Coc Inlet Flows/Pressures

    Inlets Track oven mode In the Track oven mode, the inlet temperature stays 3 °C higher than the oven temperature throughout the oven program. You cannot enter a temperature setpoint—it is set automatically. If you have CryoBlast, the inlet will track oven temperatures to –40°C;...

  • Page 46: Setting Coc Inlet Parameters

    Inlets Setting COC inlet parameters Track oven mode Press [Front Inlet] or [Back Inlet]. Press [Mode/Type] and select Track oven. There is no setpoint for Track oven mode. Ramped temperature mode Press [Front Inlet] or [Back Inlet]. Press [Mode/Type] and select Ramped temp. Enter a value for Temp.

  • Page 47: Columns And Oven

    Agilent 7820A Gas Chromatograph Advanced User Guide Columns and Oven About the Oven Oven safety Configuring the Oven About Oven Temperature Programming Programming setpoints Oven ramp rates Setting the oven parameters for constant temperature Setting the oven parameters for ramped temperature...

  • Page 48: About The Oven

    Columns and Oven About the Oven Table 7 Oven capabilities Capability Range Temperature range 0 °C to the configured limit Maximum temperature 425 °C (100 V oven: 350°C) Temperature programming Up to five ramps Maximum run time 999.99 minutes Temperature ramp rates 0 to 75 °C/min, depending on instrument configuration (100 V oven: 0 to 30 °C/min)

  • Page 49: Configuring The Oven

    Columns and Oven Configuring the Oven Oven configuration sets maximum temperature, equilibration time, and the cool down mode. Maximum temperature Maximum allowable oven temperature setpoint. Some accessories, such as the valve box, valves and columns have specific temperature limits. When configuring Maximum temperature, these limits should be considered so that the accessories are not damaged.

  • Page 50: About Oven Temperature Programming

    Columns and Oven About Oven Temperature Programming You can program the oven temperature from an initial temperature to a final temperature using up to 5 ramps during a run. A single ramp temperature program raises the initial oven temperature to a specified final temperature at a specified rate and holds at the final temperature for a specified period of time.

  • Page 51: Oven Ramp Rates

    Columns and Oven Final temperature Temperature of the oven at the end of a heating or cooling rate. Final time Time in minutes that the oven will be held at the final temperature of a temperature-programmed rate. Total length of a run is determined by its oven temperature program.

  • Page 52: Setting The Oven Parameters For Ramped Temperature

    Columns and Oven Setting the oven parameters for ramped temperature Single ramp Press [Oven] to open the oven parameter list. Enter a starting temperature (Temperature). Enter the time (Initial time) that you want the oven to stay at Temperature. Enter the rate (Rate 1) at which the oven temperature is to change.

  • Page 53: About Columns

    Columns and Oven About Columns In all GCs, a sample—which is a mixture of several components—is vaporized in an inlet, separated in a column, and examined in a detector. The column separates components in time because: • When a vaporized component is presented with a gas phase and a coating phase, it divides between the two phases according to its relative attraction to the two phases.

  • Page 54: Select A Column Mode

    Columns and Oven Ramped flow mode is not supported on EPR (electronic pneumatics NO T E regulation) equipped GCs. • Ramped flow—Increases the mass flow rate in the column during the run according to a program you enter. A column flow profile can have up to three ramps, each consisting of a programmed increase followed by a hold period.

  • Page 55: Setting The Column Parameters For Constant Flow Or Constant Pressure

    Columns and Oven This completes column mode selection. Next you must specify the inlet conditions either during the entire run (if you selected either of the constant modes) or at the beginning of the run (if you selected either of the ramped modes). Setting the column parameters for constant flow or constant pressure If the column is defined, you can enter any one of these quantities—the GC will calculate and display the other two.

  • Page 56: Programming Column Pressure Or Flow

    Columns and Oven When a flow or pressure program is running, the Pressure, Flow, and Velocity lines that you used to set constant conditions show the progress of the program. The oven program determines the length of the run. If a flow or pressure program ends before the analytical run does, the flow (or pressure) remains at the last final value.

  • Page 57: Procedures For Manually Creating A Backflush Method

    Columns and Oven • Provides the ability to create pre-column backflush methods, which require careful adjustment due to the elution times and elution order differences found on pre-columns (compared to the analytical column). For more information, see the GC and GC/MS User Manuals & Tools DVDs.
  • Page 58 Columns and Oven • Increase the pressure of the primary column connected between the CFT device and the detector(s). This creates the backward flow through the column and increases the flow through any connected detectors. When developing the backflush portion of your method, consider the following: •...
  • Page 59 Columns and Oven If you turned off data acquisition in a data system during backflush, remember to turn it on again at the end of the run. To backflush using a ramped flow program In this case, the backflush occurs as part of the run, so the detectors continue to collect data.
  • Page 60 Columns and Oven • Position 2 Carrier gas flows through the column toward the inlet, removing components on the column through the inlet vent line. The Run Table contains commands to perform these actions: • After the last peak of interest appears, switch the valve to Position 2.

  • Page 61: Nickel Catalyst Tube

    Columns and Oven Nickel Catalyst Tube About the nickel catalyst tube The Nickel Catalyst Tube accessory, G4337A, is used for trace analysis of CO and CO with a flame ionization detector. The gas sample is separated on the column and passed over a heated catalyst in the presence of hydrogen, which converts the CO and peaks to CH Sample...

  • Page 62: Setting Temperatures For The Nickel Catalyst Tube

    Columns and Oven Table 10 Gas flows for a TCD/FID series installation Flow rate, mL/min Carrier (helium) TCD switching flow FID hydrogen 45 (see Caution) FID air Hydrogen flow is pressure-controlled, where an FID provides a C AU TI O N known resistance.

  • Page 63: Hydrogen Sensor

    Columns and Oven Hydrogen Sensor The Hydrogen Sensor module checks for uncombusted free hydrogen in the GC column oven. During normal operation with hydrogen as a carrier gas, leaks from the inlets or detectors could possibly put hydrogen gas directly into the oven. Hydrogen–air mixtures are potentially explosive in concentrations of 4–74.2% hydrogen by volume.

  • Page 64: Operation With An Agilent Data System

    Columns and Oven Operation with an Agilent data system Using the hydrogen sensor with an Agilent data system provides additional features. Use the data system to: • Print calibration reports. The report includes a plot of all calibration data stored in the GC, •...
  • Page 65 Agilent 7820A Gas Chromatograph Advanced User Guide Detectors About Makeup Gas About the FID About the TCD About the µECD About the NPD About the FPD About the FPD Agilent Technologies...

  • Page 66: About Makeup Gas

    Detectors About Makeup Gas Most detectors use a makeup gas to increase the flow rate through the detector body. This sweeps peaks out of the detector quickly, avoiding mixing of components and loss of resolution. This is particularly important with capillary columns because the column flow rates are so small.

  • Page 67: About The Fid

    Detectors About the FID The FID passes sample and carrier gas from the column through a hydrogen-air flame. The hydrogen-air flame alone creates few ions, but burning an organic compound increases the number of ions produced. A polarizing voltage attracts these ions to a collector located near the flame.

  • Page 68: How Fid Units Are Displayed In Agilent Data Systems And On The Gc

    Detectors How FID units are displayed in Agilent data systems and on the GC The GC displays the FID signal in picoamperes (pA). The following table lists how different data systems convert the display units to reporting units. Table 11 Unit conversions Data system Height units...

  • Page 69: Recommended Starting Conditions For New Fid Methods

    Detectors The default setting for Lit offset is 2.0 picoamps. This is a good working value for all but very clean gases and systems. You may want to lower this setpoint if the detector attempts to reignite when the flame is still on, thus producing a shutdown. To change Lit offset: Press [Config][Front Det] or [Config][Back Det].

  • Page 70: Setting Parameters For Fid

    Detectors * Detector hydrogen is pressure controlled, where the detector provides a known resistance. If using a nickel catalyst tube, the resistance changes, and the flow rates displayed by the GC will not be accurate. Measure the actual hydrogen flow using a flow meter at the detector vent, with all other flows turned off.

  • Page 71: About The Tcd

    Detectors About the TCD The TCD compares the thermal conductivities of two gas flows—pure carrier gas (the reference gas) and carrier gas plus sample components (the column effluent). This detector contains a filament that is heated electrically so that it is hotter than the detector body. The filament temperature is held constant while alternate streams of reference gas and column effluent pass over it.
  • Page 72 Detectors Column effluent Column effluent is forced away from is forced toward the filament. TCD the filament. TCD measures reference gas. measures peaks (if present). Advanced User Guide...

  • Page 73: Tcd Pneumatics

    Detectors TCD pneumatics The figure below shows the pneumatics design of the TCD. Makeup Reference gas EPC/EPR Module Frit Frit Frit Valve Valve Valve Vent Frit Frit Reference switching valve PS = Pressure Sensor Column TCD carrier, reference, and makeup gas Reference and makeup gas must be the same as the carrier gas, and the gas type must be specified in both the inlet and detector parameter lists.

  • Page 74: Tcd Gas Pressures

    Detectors Ratio of reference flow to column + makeup flow Column + makeup flow, mL/min TCD gas pressures Choose a flow, find a pressure, set source pressure 10 psi (70 kPa) higher. Hydrogen Helium Reference gas flow, mL/min Nitrogen Pressure (psig) kPa) Advanced User Guide...

  • Page 75: Selecting Reference And Makeup Flows For The Tcd

    Detectors Hydrogen Makeup gas flow, mL/min Helium Nitrogen Pressure (psig) kPa) Selecting reference and makeup flows for the TCD Table 13 Recommended flow rates and temperatures Gas type Flow range Carrier gas Packed, 10 to 60 mL/min (hydrogen, helium, nitrogen) Capillary, 1 to 5 mL/min Reference 15 to 60 mL/min...

  • Page 76: Changing The Tcd Polarity During A Run

    Detectors compounds may attack the filament. The immediate symptom is a permanent change in detector sensitivity due to a change in filament resistance. If possible, such compounds should be avoided. If this is not possible, the filament may have to be replaced frequently. Changing the TCD polarity during a run Negative polarity On inverts the peak so the integrator or Agilent data system can measure it.
  • Page 77 Detectors Verify that makeup gas type is the same as that plumbed to your instrument (next to Makeup line in the parameter list). Change the gas type, if necessary. Set the reference gas flow rate. If you are using packed columns, turn off the makeup gas (or proceed to step and enter 2 to 3 mL/min, see “TCD carrier,...
  • Page 78 Detectors 2 m × 0.2 mm capillary column If column flow is 0.75 mL/min, the makeup must be at least 4.25 mL/min. Set it = 5. Reference flow will then be 3 × 5.75 = 17.25 mL/min. Total detector flow = 5.75 + 17.25 = 22.5 mL/min.

  • Page 79: About The Μecd

    Detectors About the µECD The micro-cell detector (µECD) contains a cell plated with a radioactive isotope. The Ni releasesparticles that collide with carrier gas molecules to produce low-energy electrons—each  particle produces approximately 100 electrons. The free electrons produce a small current—called the reference or standing current—that is collected and measured in a pulsed circuit.

  • Page 80: Μecd Warnings

    Detectors µECD licenses Customers in the United states can purchase an exempt model µECD. Customers outside the United States should contact their local Agilent sales office for information. µECD warnings Although beta particles at this energy level have little penetrating power —the surface layer of the skin or a few sheets of paper will stop most of them—they may be hazardous if the isotope is ingested or inhaled.
  • Page 81 State regulation. For other countries, consult with the appropriate agency for equivalent requirements. Agilent Technologies recommends a vent line inside diameter of 6 mm (1/4 inch) or greater. With a line of this diameter, the length is not critical.

  • Page 82: Μecd Gas Flows

    Detectors µECD gas flows Anode purge Makeup EPC Module Frit Frit Frit Valve Valve Valve Vent Frit Frit Capillary adapter Column PS = Pressure Sensor µECD linearity The µECD response factor versus concentration curve is linear for four orders of magnitude or more (linear dynamic range = or higher) for a broad range of compounds.

  • Page 83: Μecd Temperature

    Detectors µECD temperature To prevent peak tailing and to keep the cell clean, the detector temperature should be set higher than the highest oven temperature used—the setpoint should be based on the elution temperature of the last compound. If you operate at excessively high temperatures, your results will not necessarily improve and you may increase sample and column decomposition.

  • Page 84: Μecd Temperature Programming

    Detectors µECD sensitivity can be increased by reducing the makeup gas flow rate. µECD chromatographic speed (for fast peaks) can be increased by increasing the makeup gas flow rate. µECD temperature programming The µECD is flow sensitive. If you are using temperature programming, in which the column flow resistance changes with temperature, set up the instrument as follows: •...

  • Page 85: About The Npd

    Detectors About the NPD We strongly recommend that you allow the firmware to perform Auto Adjust and set the Bead Voltage. NPD flows and general information The NPD passes sample and carrier through a hydrogen/air plasma. A heated ceramic or glass source, called the bead, is just above the jet. The low hydrogen/air ratio cannot sustain a flame, minimizing hydrocarbon ionization, while the alkali ions on the bead surface facilitate ionization of nitrogen- or phosphorus-organic compounds.

  • Page 86: Npd Flow, Temperature, And Bead Recommendations

    Detectors NPD flow, temperature, and bead recommendations Table 16 General operating values Gas or Setting Recommendation Carrier gas (helium, hydrogen, nitrogen) Capillary, choose optimum flow based on column dimensions. Detector gases Hydrogen Ceramic bead 2 to 5 mL/min 60 mL/min Capillary makeup (helium, nitrogen) Ceramic bead Nitrogen: 5 to 10 mL/min...

  • Page 87: Npd Required Gas Purity

    Detectors Flow, mL/min Helium Nitrogen Pressure (psig) kPa) Hydrogen Flow, mL/min Pressure (psig) kPa) Temperature programming The NPD is flow sensitive. If you are using temperature programming, in which the column flow resistance changes with temperature, set up the instrument as follows: •...

  • Page 88: Setting Parameters For The Npd

    Detectors gases, including the detector hydrogen, air, and makeup gases. Do not use plastic (including PTFE) tubing, plastic-bodied traps, or O-ring seals. Setting parameters for the NPD Before operating the NPD, make sure that detector gases are connected, a column is installed, and the system is free of leaks. Set the oven temperature, inlet temperature, and column flow.

  • Page 89: Selecting An Npd Bead Type

    Detectors flow mode, choose Constant makeup. For a column in the constant pressure mode, choose Column +makeup=constant. If your column is not defined, enter a makeup gas flow. Only constant flow is available. Monitor the offset adjustment process. If Auto Adjust is On, the adjust offset process starts automatically when the detector reaches setpoint.

  • Page 90: Selecting An Npd Jet

    Detectors Selecting an NPD jet Open the oven door and locate the column connection fitting at the base of the detector. It will look like either a capillary optimized fitting or an adaptable fitting. Adaptable fitting Capillary optimized fitting Detector fitting Adapter •...

  • Page 91: To Configure The Npd

    Detectors Table 19 Jets for adaptable fittings Figure 4 ID Jet type Part number Jet tip id Length Capillary with extended jet G1534-80590 0.29 mm (0.11 inch) 70.5 mm (recommended) Capillary 19244-80560 0.29 mm (0.011 inch) 61.5 mm Capillary, high-temperature 19244-80620 0.47 mm (0.018 inch) 61.5 mm...

  • Page 92: Automatically Adjusting Npd Bead Voltage

    Detectors Maximum Bead Voltage Display only. Shows the current maximum bead voltage for the configured bead type (4.095 V for ceramic beads). Automatically adjusting NPD bead voltage Agilent recommends using the Adjust offset feature to automatically determine the lowest bead voltage needed to give the desired response.

  • Page 93: Setting Npd Adjust Offset On The Clock Table

    Detectors Detector on and ready. When the Adjust offset value is reached, the Adjust offset line reads Done and displays the offset target setpoint. Your detector is on and ready. The display shows the actual Bead voltage. Setting NPD adjust offset on the clock table You can use the Clock table feature to begin Adjust offset at a specified time.

  • Page 94: Setting The Initial Bead Voltage For New Beads

    Detectors Turning off the detector If you turn Adjust offset [Off] at any time, the bead voltage, C AU TI O N hydrogen, and air flows all turn off. Setting the initial bead voltage for new beads Before you turn on the bead for the first time, manually set its voltage to a safe value so that the new bead is not destroyed.
  • Page 95 Detectors desired offset. With a clean environment, clean gas supplies, and low bleed column, a typical offset may decrease 6-12 pA during a 24 hour period. Typical voltages for new ceramic beads range from 2.5 to 3.7 volts. Higher values reduce bead life. Advanced User Guide...

  • Page 96: About The Fpd

    Detectors About the FPD The sample burns in a hydrogen-rich flame, where some species are reduced and excited. The gas flow moves the excited species to a cooler emission zone above the flame where they decay and emit light. A narrow bandpass filter selects light unique to one species, while a shield prevents intense carbon emission from reaching the photomultiplier tube (PMT).

  • Page 97: Fpd + Linearity

    Detectors gas flows The hydrogen fuel gas and makeup gas mix at the EPC module, and enter the bottom of the detector where the column enters the transfer line. See Figure 4. This gas mixture eliminates any dead volume near the column entrance before mixing with air in the emission block for combustion.

  • Page 98: Fpd + Optical Filters

    Detectors on. A brief exposure (always with the PMT voltage turned off) will not damage it but prolonged exposure will cause a gradual loss of sensitivity. optical filters The filters are marked on the edge with the transmission wavelength. Each filter has a small arrow or triangle on its side which must point toward the PMT when installed.

  • Page 99: Fpd + Gas Purity

    Detectors gas purity High-purity gases have a lower sulfur content. Standard purity gases have a higher sulfur content which impairs sulfur detection in the compound being studied. Instrument or Chromatographic grades work well. Agilent recommends using helium carrier, nitrogen makeup gas, and air with 99.9995% purity or better.

  • Page 100: Setting Parameters For The Fpd

    Detectors During the ignition sequence, the detector does the following: Until the detector temperature zones reach setpoint, the GC purges the detector with all gas flows. Once the detector stabilizes at its thermal setpoints, the GC turns off hydrogen and makeup gas flows. Carrier and air flows remain on.
  • Page 101 Detectors Press [Front det] or [Back det]. Set the detector temperature. Scroll to Temperature and input the desired value, and press [Enter]. It must be greater than 120 °C for the flame to light. Scroll to H2 flow and change the hydrogen flow rate, if desired.

  • Page 102: About The Fpd

    Detectors About the FPD The sample burns in a hydrogen-rich flame, where some species are reduced and excited. The gas flow moves the excited species to a cooler emission zone above the flame where they decay and emit light. A narrow bandpass filter selects light unique to one species, while a shield prevents intense carbon emission from reaching the photomultiplier tube (PMT).

  • Page 103: Fpd Linearity

    Detectors FPD linearity Several mechanisms produce sulfur emission. The excited species is diatomic, so that emission intensity is approximately proportional to the square of the sulfur atom concentration. The excited species in the phosphorus mode is monatomic, leading to a linear relationship between emission intensity and atom concentration.

  • Page 104: Inlet Liners For Use With The Fpd

    Detectors The phosphorus filter is yellow/green and transmits at 525 nanometers. Inlet liners for use with the FPD Compounds containing sulfur may adsorb on an inlet liner and degrade the GC’s performance. Use deactivated, clean liners or a cool on-column inlet, which injects directly onto the column. For best results with splitless injection, use liner 5181-3316.

  • Page 105: Lighting The Fpd Flame

    Detectors Table 21 Recommended flows (continued) Sulfur mode flows, Phosphorus mode mL/min flows, mL/min Detector gases Hydrogen Carrier + makeup Helium, either as carrier or makeup gas, may cool the detector gases below the ignition temperature. We recommend using nitrogen rather than helium. Lighting the FPD flame Before trying to light the flame, have the detector at operating temperature.

  • Page 106: Setting Parameters For The Fpd

    Detectors Manual ignition Press [Front Det] or [Back Det]. Scroll to Flame. Press [On/Yes]. The flame ignition sequence begins. Automatic ignition If the FPD output with the flame on falls below the flame-off output plus the Lit offset value, this is interpreted as a flame-out condition.
  • Page 107 Detectors On ignition, the signal increases. Typical levels are 4 to 40 pA in sulfur mode, 10 to 70 pA in phosphorus mode. Verify that the flame is lit by holding a cold, shiny surface, such as a mirror or chrome-plated wrench, over the vent exit. Steady condensation indicates that the flame is lit.
  • Page 108 Detectors Advanced User Guide...
  • Page 109 Agilent 7820A Gas Chromatograph Advanced User Guide Valves The Valve Box Heating the valves Valve temperature programming Valve Control The valve drivers The internal valve drivers Valve Types Configuring a Valve Controlling a Valve From the keyboard From the run or clock time tables...

  • Page 110: Valves

    Valves The Valve Box The GC holds up to three valves in a heated valve box on top of the oven. The valve box is the preferred location for valves because it is a stable temperature zone, isolated from the column oven. Back of chromatograph Valve heater block Valve box, cover...

  • Page 111: Valve Control

    Valves Valve Control Valves can be controlled manually from the software keyboard or as part of a clock or run time program. Note that sampling valves automatically reset at the end of a run. The valve drivers A valve driver is the software and circuitry in the GC that controls a valve or related function.
  • Page 112 Valves Manual valves must be switched by hand, and are heated or unheated. Advanced User Guide...

  • Page 113: Valve Types

    Valves Valve Types The possible valve types are: Sampling A two-position (load and inject) valve. In load position, an external sample stream flows through an attached (gas sampling) or internal (liquid sampling) loop and out to waste. In inject position, the filled sampling loop is inserted into the carrier gas stream.

  • Page 114: Configuring A Valve

    Valves Configuring a Valve Press [Config]. Scroll to Valve #. Enter the valve number and press [Enter]. The current valve type is displayed. To change the valve type, press [Mode/Type], select the new valve type, and press [Enter]. Advanced User Guide...

  • Page 115: Controlling A Valve

    Valves Controlling a Valve From the keyboard Valves have two positions controlled by the [On] and [Off] keys. The keyboard commands for two-position valves are: [Valve #] <scroll to the valve> [On] Rotates valve to one stop [Valve #] <scroll to the valve> [Off] Rotates valve to the other stop From the run or clock time tables...
  • Page 116 Valves Sampling valves have two positions: Load position The loop (external for gas sampling, internal for liquid sampling) is flushed with a stream of the sample gas. The column is flushed with carrier gas. Inject position The filled loop is inserted into the carrier gas stream.
  • Page 117 Agilent 7820A Gas Chromatograph Advanced User Guide GC Output Signals About Signals Analog Signals Analog zero Analog range Analog data rates Selecting fast peaks (analog output) Digital Signals Digital zero Signal Freeze and Resume Data rates with Agilent data systems...

  • Page 118: Gc Output Signals

    GC Output Signals About Signals Signal is the GC output to a data handling device, analog or digital. It can be a detector output or the output from flow, temperature, or pressure sensors. One signal output channel is provided. Signal output can be either analog or digital, depending on your data handling device.

  • Page 119: Analog Signals

    GC Output Signals Analog Signals If you use an analog recorder, you may need to adjust the signal to make it more usable. Zero and Range in the Signal parameter list do this. Analog zero Zero Subtracts value entered from baseline. Press [On/Yes] to set to current Value or [Off/No] to cancel.

  • Page 120: Analog Data Rates

    GC Output Signals A: Range = 0 B: Range = 3 C: Range = 1 There are limits to usable range settings for some detectors. The table lists the valid range setpoints by detector. Table 24 Range limits Detector Usable range settings (2 0 to 13 0 to 13 0 to 13...

  • Page 121: Selecting Fast Peaks (Analog Output)

    GC Output Signals Selecting fast peaks (analog output) Press [Config][Analog Out]. Scroll to Fast peaks and press [On]. Agilent does not recommend using Fast peaks with a thermal conductivity detector. Since the gas streams switch at 5 Hz, the gain in peak width is offset by increased noise. Advanced User Guide...

  • Page 122: Digital Signals

    GC Output Signals Digital Signals The GC outputs digital signals only to an Agilent data system. The following discussions describe features that impact the data sent to data systems, not the analog data available to integrators. Access these features from the data system. These features are not accessible from the GC keypad.

  • Page 123: Data Rates With Agilent Data Systems

    GC Output Signals Baseline upset due to valve switch Pause signal here Resume signal here Data rates with Agilent data systems The GC can process data at various data rates, each corresponding to a minimum peak width. The table shows the effect of data rate selection.
  • Page 124 GC Output Signals Table 25 Agilent data system data processing (continued) Data rate, Hz Minimum peak Relative Detector Column type width, minutes noise 0.04 All types 0.22 0.16 0.10 0.07 Slow packed You cannot change the data rate during a run. You will see higher relative noise at the faster sampling rates.

  • Page 125: Zero Init Data Files

    GC Output Signals Zero Init Data Files This feature applies to digital output only, and is mainly intended for non-Agilent data systems. It may help systems that have trouble with non-zero baseline output. When you turn it On, the GC immediately begins to subtract the current detector output value(s) from any future values.
  • Page 126 GC Output Signals Advanced User Guide...

  • Page 127: Auxiliary Devices

    Agilent 7820A Gas Chromatograph Advanced User Guide Auxiliary Devices About Pressure Control Pressure units Agilent Technologies...

  • Page 128: About Pressure Control

    Auxiliary Devices About Pressure Control Pressure units There are two common ways of expressing gas pressures: psia Absolute pressure, measured relative to vacuum. psig Gauge pressure, measured relative to atmospheric pressure. This name is used because most pressure gauges have one side of the sensing element exposed to the atmosphere.
  • Page 129 Auxiliary Devices Advanced User Guide...
  • Page 130 Agilent Technologies © Agilent Technologies, Inc. Printed in USA, August 2016 G4350-90020 G4350-90020...

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