| Author | Message | ||
     Gavriel Levin (levin) Senior Member Username: levin Post Number: 29 Registered: 1-2006 |
Hi, Anyone wants info on Benzene, Toluene in gas cell, please write to me. Gabi Levin, Brimrose. [email protected] | ||
| Nuno Matos (nmatos) Intermediate Member Username: nmatos Post Number: 37 Registered: 2-2005 |
Bruce, Thank you for your reply. At this moment I am not using a calibration yet. What I do is to collect the spectra and perform two PCA on two peaks (each one with contribution of a sinlge solvent). The spectra are pre-processed - 2nd derivative - to remove baseline drifts - not using heated line. Because I do not perform mean-centering, 1st score of each PCA will give me the mean. This is the same as calculating the area under each peak (the software does not allow me to do that). From this EDA I get a drying profile. The profile iis than compared with the GC results of offline samples (after normalizing units). On the next run I will test the residence time by flushing the gas line with nitrogen and let the dryer gas outflow again into the line. Suggestions are very welcome. Regards | ||
| Bruce H. Campbell (campclan) Moderator Username: campclan Post Number: 91 Registered: 4-2001 |
From what you stated it appears the GC is testing the dried material. If that is so, you may have some buildup of solvent in the piping when intially the drying is initially started. Then, with highly laminar flow in the pipe, the contents of the pipe don't change as fast as in the drier. This hypothesis may be butressed - if the calibration for the NIR gas cell was performed by GC for samples that in essence were "taken" at the same spatial place as those for the GC. | ||
| Nuno Matos (nmatos) Member Username: nmatos Post Number: 36 Registered: 2-2005 |
I have used the gas cell in a drying process (two organic solvents are dried in a biconical dryer) and got good and realistic results. However, the GC results (off-line test) shows that the solvents were bellow 100ppm much before the NIR signal was residual. Does this make any sense? (The gas cell is mounted on the NIR equipment and the gas is being transported from the gas outflow to the gas cell 2x100 ft, no condesates were observed). | ||
| Nuno Matos (nmatos) Junior Member Username: nmatos Post Number: 35 Registered: 2-2005 |
Howard, I am aware of the lackness of reports on NIR measurements of gases. That is way I have posted the previous message. I will keep you posted. At the moment I am using a fixed pathlenght cell of 1200mm (~47''). I already got a gas spectrum. My actual problem was keeping flow in the gas cell. Nuno | ||
| Howard Mark (hlmark) Senior Member Username: hlmark Post Number: 39 Registered: 9-2001 |
Nuno - there are very, very few reports of NIR measurements of gases. Be good of you could keep us posted on your experiences. What pathlength cell are you using? Howard \o/ /_\ | ||
| Nuno Matos (nmatos) New member Username: nmatos Post Number: 34 Registered: 2-2005 |
I am trying to use a gas cell for NIR sprectroscopy. I starting the process. Do you have any useful advices? Thanks in advance |