Sign Up

Sign In

Forgot Password

Lost your password? Please enter your email address. You will receive a link and will create a new password via email.

You must login to ask question.

Sorry, you do not have a permission to add a post.

Please briefly explain why you feel this question should be reported.

Please briefly explain why you feel this answer should be reported.

What is solvent delay in GC MS?

What is solvent delay in GC MS? The function of the solvent delay in a GC-MS system is to protect the MS filament form the effects of high concentrations of solvent vapour in the source. Since, usually, an FID is not damaged by solvent going through it, a solvent delay is not necessary on a GC-FID.

Which solvent is used to reduce tailing in gas chromatography?

Abstract. The injection of analytes into a gas chromatography–mass spectrometry (GC–MS) system using dichloromethane (DCM) as solvent led to gradual deterioration of chromatographic signals, with significant tailing and loss of sensitivity for C17+ hydrocarbons.

How do you calibrate a GC instrument?

Basic Steps of Gas Chromatography Calibration

  1. Switch on the GC instrument and open the carrier gas cylinders or run your gas mixer if you are using one.
  2. Adjust pressure and check the carrier gas flow rate, comparing setpoint to observed flows at different rates.

How can the separation of gas chromatography be improved?

Increasing the carrier gas linear velocity will increase the speed of analysis. Loss of resolution can occur if the speed is increased much higher than the optimal velocity for the carrier gas. Using hydrogen and higher linear velocity will improve efficiency.

How do you find concentration from peak area in GC?

  1. First you run pure standard with known concentration and note down retention time and peak area.
  2. Now run sample and note down the chromatographic area of peak appear at same retention time as that of standard. …
  3. Calculate concentration= sample Area of sample divided by area of standard multiply by conc.

How can we reduce tailing?

There are a few methods that can be used to avoid peak tailing:

  1. Operate at a lower pH.
  2. Use a highly deactivated column.
  3. Consider the possibility of mass overload.
  4. Consider the possibility of column bed deformation.
  5. Work at high pH when analyzing basic compounds.
  6. Use a sample clean-up procedure.

How do you lower peak tailing in GC?

Try changing your stationary phase or solvent. If peak tailing is occurring only in peaks closest to the solvent front or major component peak, consider the Reverse Solvent Effect. Try a retention gap or guard column to correct this.

How does temperature affect liquid chromatography?

Chromatography is a series of equilibrium reactions where the analytes are either dissolved in the mobile phase or adsorbed to the stationary phase of the column. The higher the temperature, the faster the exchange of the analytes between the mobile phase and the stationary phase.

How often should a GC be calibrated?

The GC makes slight adjustments to the Retention Times and Response Factors during calibration. As long as the shifts are less than the limits, the Response Factors and Retention Times will be updated. This is why Emerson recommends doing a validation every 30, 60, 90 days.

What is the principle of GC?

Principle of gas chromatography: The sample solution injected into the instrument enters a gas stream which transports the sample into a separation tube known as the « column. » (Helium or nitrogen is used as the so-called carrier gas.) The various components are separated inside the column.

What are the GC calibration parameters?


  • Column : Porapack Q.
  • Oven Temperature : 150°C.
  • Injector Temperature : 200°C.
  • Carrier : 30ml/min. ( N2)
  • Injector Temperature : 180°C.
  • Injector volume : 2.0ml.

What affects GC resolution?

The lower the boiling point, the lower will be the temperature of vapour formation and shorter will be the retention time of the eluting peak. The greater the difference between the boiling points of the constituents the better will be the resolution between the separated peaks.

What is the resolution in GC?

In chromatography, resolution is a measure of the separation of two peaks of different retention time t in a chromatogram.

What factors affect resolution in chromatography?

The choice of mobile phases, the number of sample components, the concentration of two different solvents used, sample solubility, detector efficiency (PDA or UV/VIS), and other factors may all affect resolution in HPLC separation.

Why is Peak area better than peak height?

The repeatability of peak area is much better than that of peak height. The effect of column temperature on peak area is negligible, while it is very important on peak height, because the retention time and the band width increase rapidly with decreasing temperature.

Is Peak area proportional to concentration?

The peak area is proportional to the amount of the component, so if a 100 ppm concentration has a count of 1000, a 700 count means a 70 ppm concentration. As with qualitative analysis, one could say that a standard sample is also required for quantitative analysis.

How can I improve my peak shape?

Steps that can be taken to improve early eluting peak shape:

  1. Use a split injection. This limits the amount of solvent that gets onto the column and reduces how much analyte dissolves in pooled solvent. …
  2. Decrease the injection volume. …
  3. Use a pressure pulsed injection. …
  4. Use a guard column. …
  5. Increase the column film thickness.

What is peak broadening?

peak broadening is that the peaks are fully resolved and that we could fit more peaks into a similar window of time in the chromatogram. An ideal chromatographic system would therefore produce peaks that were straight line spikes in which no broadening occurred (Figure 18a).

How do you increase peak resolution?

How to Improve Resolution in HPLC

  1. Increasing column length.
  2. Decreasing particle size.
  3. Reducing peak tailing.
  4. Increasing temperature.
  5. Reducing system extra-column volume.

What does it mean when a GC peak appears asymmetrical?

A peak is considered asymmetric when the distance from the start of the peak to the centre (A) and from centre to the end (B) of the peak differs (Fig 1). It is best to measure these distances at about 10% of the peak height. Within asymmetric peaks, there are two possibilities that could exist; Fronting and Tailing.

What is tailing factor in GC?

Definition: Tailing factor

The tailing factor is a measure of peak tailing. It is defined as the distance from the front slope of the peak to the back slope divided by twice the distance from the center line of the peak to the front slope, with all measurements made at 5% of the maximum peak height.

How does temperature affect separation in gas chromatography?

The temperature is a very important parameter to influence separation. As a rule of thumb, for every 15 °C higher or lower, the retention of a column decreases or increases by a factor of 2. That means if the last peak elutes at 100 °C after 10 minutes, it will elute at 5 minutes at 115 °C and at 20 minutes at 85 °C.

Does peak shape affect retention time?

A sample-solvent-induced retention time change is often accompanied by a change in the peak shape. For samples containing a significant portion of the matrix, an interfering peak coeluting with an analyte peak may cause a small change in the apparent retention time.

What happens if GC temp is too low?

Therefore, the temperature needs to be lowered to get favorable interactions with the phase. Obviously, too low a temperature will cause the entire amount of compound to be condensed. … This happens to be between 10 and 50C below the boiling point of the compound for a traditional open tubular capillary column.



Leave a comment