Contact manager:

443-854-4640(cell phone)

Cungen Zhang, Ph.D
Department of Pharmacology
312 WBSB
Johns Hopkins School of Medicine
1915 E. Madison St.
Baltimore, MD 21205

czhang17@jhmi.edu

The API 150 EX is being checked out everyday by Dr. Cungen Zhang, Manager

I.              Peptide User:

Peptides are usually good at about 50 micrograms/20 microliters -- should get 10^7 cpm comfortably -- but even 10-50x lower concentration should be detectable with MCA signal averaging.

The following is the washing procedure:

1.      Make sure that your peptide has a best solvent, say Acetone Nitrile. In that case you should wash with 100% CH3-CN first to monitor the decrease of your peptide peaks. You may need to fill in another syringe of pure CH3-CN. Then, wash it with 1:1 of CH3CN:H2O. Then wash it with 100% MeOH and then wash it with 1:1 of MeOH:H2O.

2.      If your peptide is most soluble in H2O, then wash it with 100% H2O, and monitor the decrease of the peaks of your peptide. Wash two syringes of the best solvent and  then wash with CH3CN, then MeOH and then the mix of MeOH and H2O.

3.      Make sure that there is no salt in the solvent. You know Na2CO3 or NaHCO3 can be possibly crystallized in the tubing. So wash completely with H2O if you know that there is some salt in your buffer.

4.      Peptide users are strongly suggested to minitor the low molecular region, say 100 to 500. And wash out all the peaks to as low as e^5.    e^4 is the ideal level for you to leave.

II.               Small Molecule User:

Small organics, the same, in volatile non-flammable solvents (MeOH and MeCN are ok, though). Sometimes 2-10 x higher concentration for small molecules is necessary because noise is higher at <1000 amu, however.  DMSO/DMF co-solvents ok at less than 10% v/v.

The following is the washing procedure:

5.      Make sure that your organic coumpound has a best solvent, say CHCl3. In that case you should wash with 100% CHCl3 first to monitor the decrease of your compound peaks. You may need to fill in another syringe of pure CHCl3. (Then, wash it with the second best solvent, say CH3CN and then wash 1:1 of CH3CN:H2O.) Then wash it with 100% MeOH and then wash it with 1:1 of MeOH:H2O.

User Young is working on the spectrometer

----------------------The following are the suggestions by Chris Gross.

When done, the instrument should be washed with 1:1 MeOH/Water. This wash should be complete . Usually 3 times. We need to monitor the decreasing of the peaks.

If it is necessary to run a sample in chloroform, I suggest you use the following wash sequence: 1:1 MeOH, then MeOH, then chloroform (solvent) then inject chloroform sample(s) followed by solvent chloroform, MeOH, 1:1 MeOH Water.

This extensive wash sequence before and after prevents precipitation in the capillary.

Other tips:

1-5 % AcOH is good to promote ionization of species bearing amino groups or other positive functional groups (like the guanidino's on Phil's oligo Arg peptides) for positive mode scanning.

1-5% triethylamine is good to promote ionization of species bearing acidic groups (like nucleic acids) for negative mode scanning. That being said, however, negative mode scanning is inherently less sensitive than positive mode, so only use it as a less resort.

NO PHOSPHATE BUFFERS !!!! -- Suppresses ionization and nearly impossible to completely remove.

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Positive side calibration should be done every 3-4 mos. or so, depending on drift; Negative side calibration, similar, if it is being used (not very common when I was there). This is done by manager.

Pump oil should be changed when it is discolored or every 12 mos, whichever occurs first: be careful not to stain Bob's carpet. This is done by manager

Quadrupole and ring should be cleaned at least every 12 mos, unless there are a lot of heavy and/or dirty and/or salty samples being injected; residue should be visilbe outer plate.

We thank Chris Gross for the suggestions. CZ