manufacturer :       Micromass

model :                   Quattro Ultima

annotation :           Dokumente engl.

The Micromass Quattro Ultima is a high performance benchtop triple quadrupole mass spectrometer designed for routine LC-MS-MS operation. Quattro Ultima may be coupled to:

• a HPLC system with or without an autosampler.
• an infusion pump.
• a syringe pump.

Ionisation takes place in the source at atmospheric pressure. These ions are sampled through a series of orifices into the first quadrupole where they are filtered according to their mass to charge ratio (m/z).

The mass separated ions then pass into the hexapole collision cell where they either undergo collision induced decomposition (CID) or pass unhindered to the second quadrupole. The fragment ions are then mass analysed by the second quadrupole. Finally the transmitted ions are detected by a conversion dynode, phosphor and photomultiplier detection system. The output signal is amplified, digitised and presented to the data system.

Vacuum System

Vacuum is achieved using two direct drive rotary pumps, and two turbomolecular pumps.

The rotary pumps are mounted on the floor external to the instrument. The E1M18 pumps the ion source block, while the E2M28 pumps the first ion tunnel and also backs the turbomolecular pumps. The E1M18 has an automatic gas ballast control valve mounted in the oil return line from the mist filter. This solenoid valve is opened whenever the E1M18 is switched on, allowing continuous recirculation of the pump oil provided that the manual gas ballast valve on the pump is left open.

The turbomolecular pumps evacuate the analyser and ion transfer region. These pumps are both water cooled.

Vacuum measurement is by an active inverted magnetron (Penning) gauge for the analyser and a Pirani gauge for the gas cell. The Penning gauge acts as a vacuum switch, switching the instrument out of the OPERATE mode if the pressure is too high.

The speed of each turbomolecular pump is also monitored and the system is fully interlocked to provide adequate protection in the event of a fault in the vacuum system, a failure of the power supply or vacuum leaks.

Ionisation Techniques

Two atmospheric pressure ionisation techniques are available.

Atmospheric Pressure Chemical Ionisation

Atmospheric pressure chemical ionisation (APcI) generally produces protonated or deprotonated molecular ions from the sample via a proton transfer (positive ions) or proton abstraction (negative ions) mechanism. The sample is vaporised in a heated nebuliser before emerging into a plasma consisting of solvent ions formed within the atmospheric source by a corona discharge. Proton transfer or abstraction then takes place between the solvent ions and the sample. Eluent flows up to 2 ml/min can be accommodated without splitting the flow.

Electrospray

Electrospray (ESI) ionisation takes place as a result of imparting a strong electrical field to the eluent flow as it emerges from the nebuliser. producing an aerosol of charged droplets. These undergo a reduction in size by solvent evaporation until they have attained a sufficient charge density to allow sample ions to be ejected from the surface of the droplet (“ion evaporation”).

A characteristic of ESI spectra is that ions may be singly or multiply charged. Since the mass spectrometer filters ions according to their mass-to-charge ratio, compounds of high molecular weight can be determined if multiply charged ions are formed.

Eluent flows up to 1 ml/min can be accommodated although it is often preferable with electrospray ionisation to split the flow such that 100 to 200 µl/min of eluent enters the mass spectrometer.

Nanoflow Electrospray

The optional nanoflow interface allows electrospray ionisation to be performed in the flow rate range 5 to 1000 nanolitres per minute.

For a given sample concentration, the ion currents observed in nanoflow are comparable to those seen in normal flow rate electrospray. Great sensitivity gains are therefore observed when similar scan parameters are used, due to the great reductions in sample consumption.

Sample Inlet

Sample is introduced from a suitable liquid pumping system along with the nebulising gas to either the APcI probe or the electrospray probe. For nanoflow electrospray, metal coated glass capillaries allow the lowest flow rates to be obtained while fused silica capillaries are used for flow injection analyses or for coupling to nano-HPLC.

Data System

The PC based data system, incorporating MassLynx NTTM software, controls the mass spectrometer detector and, if applicable, the HPLC system, autosampler, syringe pump, divert valve or injector valve.

The PC uses the Microsoft Windows NT graphical environment with colour graphics and provides for full user interaction with either the keyboard or mouse.

MassLynx NT provides full control of the system including setting up and running selected HPLC systems, tuning, acquiring data and data processing.

Analog inputs can be read by the data system so that, where applicable, a trace from a conventional LC detector (for example UV or fluorescence) can be stored simultaneously with the acquired mass spectral data. A further option is the ability to acquire UV photodiode array detector data.

Weights

Instrument: 150kg (330lb)

Data system

(computer, monitor and printer): 60kg (130lb)

Rotary pumps

E2M28: 40kg (90lb)
E1M18: 32kg (72lb)

Transformer (optional): 100kg (220lb)

Power

Instrument: 230V (+10%, -14%), 13A Data system: 100-120V or 200-240V, 13A Pumps: 230V (+10%, -14%), 13A

Environment

Ambient temperature: 15-28°C (59-82°F) Short term variance (1.5 hours): <_2°C (<_4°F)

Overall heat dissipation (excluding LC

and optional water chiller): 4.2kW maximum

Humidity: Relative humidity <_70%

Water Cooling

Heat dissipation into the water: 200W

Exhausts

Rotary Pumps

The rotary pumps must be vented to atmosphere (external to the laboratory) via a fume hood or industrial vent.

API Gas Exhaust

The API gas exhaust must be vented to atmosphere (external to the laboratory).

Caution: The API gas exhaust line must not be connected to the rotary pump exhaust line. In the event of an instrument failure, rotary pump exhaust could be admitted into the source chamber producing severe contamination.

Nitrogen

A supply of dry, oil-free nitrogen at 6-7 bar (90-100 psi) is required.

Caution: The lines supplying nitrogen to the instrument must be clean and dry. If plastic tubing is used it must be made of Teflon. The use of other types of plastic leads to contamination of the instrument.

CID Gas

Argon is required as collision gas. The supplied gas should be dry, of high purity (99.9%) and at a pressure of approximately 350 mbar (5 psi).

Caution: Operating with the CID gas at a significantly higher pressure results in a fault.