There is also a HPLC/MS system in use, which is an Agilent 6210 system consisting of an Agilent 1100 HPLC with an additional DAD (diode array detector) and an ESI-MSD TOF by Agilent Technologies.
This instrument provides high resolution spectra at very high mass precision (below 5 ppm with external and below 2 ppm with internal calibration. Furthermore, internal calibration is provided by a second in-built sprayer orthogonal to the spray capillary and the first sprayer. The mass range (m/z 50 to 3,500) means that most ionic or polar compound can be detected, since ESI (electrospray ionization) is used to interface the LC system to the mass spectrometer. For higher mass analytes in positive ion mode a positive voltage of approx. 4 kV is applied at the spray capillary. Usually multiply charged, cationized ions of the kind [M+nH]n+ and/or [M+n(Cat1+)]n+ are detected. Samples should be as pure as possible. All other precautions are described in the FTICR section.
Direct infusion experiments can be performed by trained users, as long as they ensure that only filtered (4 µm filters), completely dissolved solutions are sprayed. Also, the sample concentration should be kept as low as possible to prevent carry-over and damage to the detector, a maximum concentration of 100 µmol/L is requested. Maximum number of counts per peak is 1,000,000 (106)! If you have higher counts, please dilute immediately! The saturation of the detector also leads to a dramatic loss in mass accuracy.
For LC/MS measurements, the measurements are performed by the users themselves after some training. In addition to the precautions which should be taken into account for direct infusion measurements, the user has to ensure that all compounds in the sample solution are suitable for HPLC measurements. The samples must neither react with the column nor stick to the column for eternity. The pH of all samples and the solvents used should be between ph 7 and pH 4. As buffers, all highly volatile buffers (with anions like carbonate, acetate or formate and ammonium, triethylammonium) at a maximum concentration of 10 mmol/L can be used.
Acids/bases/buffers with low volatility like, e.g., sulfuric acid, phosphate buffers or sodium hydroxide are strictly forbidden to prevent damage.