Prince:Introduction

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What is Mass Spectrometry?

For our purposes, mass spectrometry is an analytical technique by which we measure the m/z or mass/charge ratio of charged particles we've introduced by use of our electrospray ionization ESI from the liquid phase, allowing for liquid chromatography to occur in-line with the instrumentation. It is nearly that simple. However, in application, there are many factors that must be considered to achieve desired results.

Nano-electrospray ionization (NSI)

Nano-ESI is essentially the same process as conventional ESI with a primary difference in the flow rates involved. ESI is conventionally performed at μL/min flow rates and involves the coordination of gas flows around the spray tip. Nanospray is typically performed at < 1 μL flow rates, to as low as ~30 nL/min.

Ultra-High Pressure/Performance Liquid Chromatography (UPLC)

To provide ever better chromatographic separations, instrumentation has gone to ever increasing pressures. For NSI applications, the low flow rates and desire to limit the 'dead volume' or space in which chromatographic resolution might be lost by diffusion, the entire system is very low volume. Because of these concerns, tubing is conventionally fused-silica with a very small internal diameter ( < 100 microns). Chromatography is performed in columns packed inside this glass tubing, and with the smallest beads possible. These factors result in a very high pressure due to the small diameters and flow restriction by these beads.

Fragmentation

intro discussion to why we fragment, followed by ...

Our Instrumentation

We run a Thermo-Fischer LTQ Orbitrap XL w/ ETD coupled to a Eksigent Ultra 2D LC system capable of maximum pressures of 10,000 psi and flow rates on the two pumps of < 1000 nL/min and < 30 μL/min (discuss the two pumps)...

• More information.... Prince:Lab_Equipment_&_Instruments_Description

Guidelines for use

We are not lab technicians. Unless that changes, we are unable to allow for unorthodox uses of the instrument. Contact us if you have other questions.

Criteria for use

There are two types of samples we are willing to run. Please understand that determining what a spectra represents can be very challenging.

Direct Injection

• Salt-free samples
• Only MS grade solvents required
• Minimum concentration of 1 pmol/μL
  • pH < 3 for positive ion mode
  • pH > 10 for negative ion mode
• Own silica tubing (2 ft) and gas-tight Hamilton (50 to 500μL) syringe required (for your own sample's sake)
• Use must be scheduled by Aman or Ryan

LCMS

• Digested proteins/peptides only
• pH of 3 (1% formic acid is great)
• 20 μL minimum sample volume (requires low-volume vials, listed below)
  • Or, the stockroom has vials that are minimum 200 μL volume
• Must have been run through Vivacon MWCO Filter
• Unless you can convince us that your method is acceptable, samples must be prepared with our Filter-Aided Sample Preparation (FASP) method (in-gel and solution variants)

Parts/Supplies Ordering information

• snap cap lids ( National Scientific C4011-55 ) 100/pkg
• 250 μL conical well sample vials ( National Scientific C4011-13 plastic or C4011-LV1W glass )
• silica 360 μm OD (IDEX Health & Sciences FS-120) will be more than enough for your needs
• Vivacon Filters