As you are not using GC-MS, identification of the peaks is difficult. Probably the peaks which did not show any change in area with conc. were coming from column bleeding. The peaks might be from plasticizers also, which you had used for standard/sample preparation. You can run only pure solvent and check whether any peak is coming or not. If the chromatogram shows similar peaks then they might be coming from your column (e.g. siloxane). Then either you have to condition or replace the column.

Hi

From what you have written, I suppose you are doing this analysis for the first time and have no earlier data to compare. So in that case you need to check following things

1. Your ref. standard wrt its COA. Is it the cinnamon oil or only cinnamldehyde that you are using as ref. std? If its oil, there could be other compounds as well. From what you have written i hope its pure trans cinnamaldehyde, but just check the certificate of analysis provided by the manufacturer.

2. Also check your GC column. Condition it as per the manufacturer's guideline. It may not have been cleaned properly last time some body used it....Running a column blank, may help. If unwanted peaks are eluting from column itself you need to condition it or other wise replace with a good brand.

3. Check your GC liner, it may be dirty, clean it.

4. Clean your GC syringe

5. Unwanted peaks coming from Nitrogen is a rare possibility

6. Checking solvent is also a good idea. Just put the pure solvent you have used to make dilutions

I hope this helps

Please ensure the purity of your sample, sometime cinnamaldehyde get oxidised by air exposer which leads to produce impurities like cinnamic acid  etc..  I suggest you try other fresh packed sample. 

Another possibility,

Your GC Column has some previous impurity.  Please reactivate your column for 1 day.

Column Reactivation procedure.

Suppose Your column maximum temperature limit is 300oC.  Increase your column temperature with 5oC/min to 280oC in present of flow carrier gas.  Keep it for 5 to h.  This leads to your column cleaning and reactivation.    Before reactivation you can change the glass wool in sample inlet.  Keep detector and injector temperature on.

Hello

maybe the reasons are

1) Low purity of carrier gas ( the most recommended gas carrier is He ) and you maybe need to install a moisture trap

2) Septum or column bleeding due to high temperature (you must clean your column with solvents of different polarity at 250 -280°C by 12-24 hrs.

3)Ghost peaks please check your electric connections

4) clean the siringe

5) use solvents of high quality (GC or HPLC grade only)

6) replace the liner and septum

7) if you are using a FID  you must check the connections beetwen jet and column (ferrule)

8) check ypu reference materials with some blanks of pure solvents

with best regards

Please check  all the suggestions by the other scientists. I think they covered almost every reason why you are having problems with your analysis.  If the standards are pure (99% +) then it could be:

1. degradation of the standard in solution

2. Dirty septum

3. Column bleeding

4. Change to Helium fo cor carrier gas

5. Run solvent by itself-Control

6. What type of detector are you using for your analysis

Good luck

There are a lot of very good ideas in all the answers above.  You did not provide any information about your sample prep.  Since you said that the largest peak does not change linearly with concentration, and we expect the largest peak to be cinnamaldehyde even if the sample has oxidized, I wonder:

1.  is the largest peak your solvent peak (you are using solvent, correct?)

2.  are you injecting too much, too concentrated a sample, so that the detector is saturated for this peak?  In this case, the numerous peaks could be relatively minor impurities that are out of proportion.  The large peak would be mis-shapen and maybe even flat-topped it if is overloaded.

What is your sample concentration?  Try diluting the samples 10-fold and repeating the calibration.

one large peak could be of the solvent in which you have prepared your std or it would be mentioned on the bottle itself, try to inject the same solvent in pure for individually and see if the largest peak is at the same time or not,

second you should dilute your sample it can be in larger concentration.

Third some times there are certain peaks which come very frequently could be the noise in the instrument which usually comes when voltage fluctuation is there.

for this you need to stabilize the instrument in the given condition by injecting solvent only many times once you are getting only solvent peak trhen inject your sample/std.

Although I do not get much information from your question, I guess the problem is the vanished cap liner, which is easily dissolved by most organic solvents. Change to a silicone or put a teflon liner would solve your problem.

First of all, you should analyze the pure solvent, you will get information about the large peak not growing - this is probably a solvent, and in addition you will see if then also additional peaks appear

if the peaks do not appear, it is most likely a fault only for the standard, which either oxidized or has a low purity to GC, the best purity is at least 99.8%

if the peaks still appear with the pure solvent, (which should also have a purity of at least 99.8%), this means that the problem may be an impure solvent, a carrier gas with too little purity or a dirty liner - but since these peaks are in the same retention times and grow with the increase in the addition of the standard is rather the fault of the polluted standard.

You didn't tell us anything at all about how you ran the sample - no detector, no injector conditions, no column information, etc. You do state that you injected mg quantities of cinnamaldehyde into the GC. This would require that your split ratio be huge, on the order of 1:200. Since you tell us that you don't know GC I assume that you also have no clue how to measure a split ratio.

You are at the University of Utah. I will promise you that you have people on campus that absolutely know how to use a GC. I highly suggest that you seek them out and learn the basics of GC before you post again here so that you can ask intelligent and well-formulated questions and give us a chance to actually help you rather than throw out guesses like all of the previous posts.

Just starting / stepping into a steep learning curve.  Simply said, the presence of multiple peaks in GC is either chemical (compound of interest itself once entering the GC column is no longer a single chemical species)  or instrumental (the GC operating parameters are not set up properly or optimized fully), or some of each.

The access to figuring this out is choosing to be a detective: make a hypothesis and test the hypothesis experimentally.  If another single compound injected onto the same column also gives multiple GC peaks, that suggests one answer,  if not, choose another hypothesis and invent a experiment to test that one.  My experience especially in analytical chemistry is that one must do the experiments to know in any specific case what the actual reason something works or does not work.  Hypotheses are just likely or possible answers,  I guess.