The Royal Society of Chemistry posted a terrific tutorial on the basics of gas chromatography. The video shows an operator separating methanol and toluene step by step using a flame ionization detector (FID). Towards the end of the video, the GC is connected to a mass spectrometer detector similar our Shimadzu QP5050A.
..to be safe. This reminder is especially useful during routine tasks. Indeed, safety has been a hot topic lately in the chemistry blogosphere. It is abuzz about recent charges brought against UCLA over the tragic death of a research assistant in an organic chemistry laboratory. According to C&ENews, the young chemist was using tert-butyllithium when it spilled and autoignited. This tragedy has become a teachable moment for chemistry labs everywhere. Subscribe to The Safety Zone at CENtral Science for the latest chemical safety news and tips.
Posted in Safety
Say goodbye to the elusive art of KBr pellet making and messy NaCl plates (along with the variability they introduce) with the department’s new FT-IR spectrometer and ATR accessory. The PerkinElmer Spectrum Two is the gold standard for rapid IR measurements and the ATR zinc selenide crystal is perfect for generation of an evanescent wave that penetrates any sample (pH range 5-9).
Apply just enough pressure on the clamp to ensure a 1 micrometer intimacy and you’re on your way to spectral heaven. There’s even a nifty preview feature in the software which allows you to optimize contact before scanning to prevent scratching. An installed humidity sensor detects the best time to change desiccants, perfect for the rainy seasons we’ve been having (a.k.a. optics killers). Still curious about how this incredible technology works? The vid below depicts the S2 in action. (Click here to learn more about IR spectroscopy with correlation table.)
Recently, an overhaul was conducted on our Shimadzu GC/MS. Both source and trap filaments were replaced inside the ion source box, the heart of the system. This is where your sample gets zapped by an electron beam turning it into fragments. The two filaments (doohickeys that produce the beam) were barely alive and have since been put out of their misery. Additionally, the ion source box was scrubbed from top to bottom, ridding it of extraneous ions produced from the blasts.
A helium purifier has also been replaced which scrubs our carrier gas. This provides a smoother baseline when injecting into the GC port.
Bottom line – the unit is fully optimized for its nanogram range detection limit. Here are some tips to keep it that way:
1) Begin with 1uL of sample for GC or a “spec” of solid for direct insertion. More than that may contaminate the system for the next person.
2) Remember to set the detector no greater than 1.10 kV. It’s an electron multiplier that won’t give you better data if you ramp it up. You’ll only be shortening its life.
3) Any questions contact Joe at the info provided on the instrument. He will be more than happy to assist.
This Royal Society of Chemistry vid is the best I’ve seen to describe chromatographic principles within the context of HPLC. According to the standard handbook, the money currently spent annually on HPLC exceeds that of any other analytical technique.
Posted in HPLC
Tagged HPLC, video
3 primary trouble shooting steps to eliminate residual contamination in a GC are changing inlet liners, replacing rubber septa, and cutting a few inches of the front of the column near the injection port. This last step will remove the part of the column that gets battered with high temperature adhering compounds. Tailing may also result as integrity in this area of the column is lost. Watch this great vid by the Agilent guys that details the technique (at 3:00) . It takes a bit of practice to get it right, so be sure to look at the end carefully to make sure it’s a clean slice. Jagged edges will cause leaks.
Posted in GC
Tagged contamination, GC
Software was recently attained and installed on an Agilent 1200 Series LC after being down for quite some time, although this didn’t solve the problem entirely. If you encounter the same, here is everything you need to know about how to get the hardware working again..fast.
1) Flush with IPA
Isopropyl alcohol with water is the perfect solvent to wash away both polar and non-polar contaminants that have accumulated in the lines. It is also viscous enough to get into all the cracks and crevices where air bubbles are hiding. Prep a 50:50 mixture, replace the column with a union, and run all the lines together at 0.5 mL/min.
There may be enough air in the system to render the pump useless. To attain suction, manually pull through 20 mL of your IPA/water mixture on each of your 4 lines. Simply remove the outgoing fitting from the degasser, press firmly using a plastic syringe to create an air tight seal, turn on the pump and withdraw the syringe plunger. Repeat the final step. It will soon flow like a river.
3) Go to Step 1
Assuming the lamp still has life on it, the pump is the heart of the instrument and should render it functional once cleared of air and contaminants. After sufficient washing with your IPA mixture (when the pressure stabilizes you’ll know all the air is out), check your flow rate at the waste bottle using a small graduated cylinder and stop watch. Once validated you’re good to go.