manufacturer :       Micromass

model :                   Q-TOF micro

annotation :           Dokumente engl.

Instrument Description

The Q-Tof micro hybrid quadrupole time of flight mass spectrometer is available with electrospray ionisation (ESI) and atmospheric pressure chemical ionisation (APcI).

Q-Tof micro utilises a high performance, research grade quadrupole mass analyser, incorporating a prefilter assembly to protect the main analyser from contaminating deposits, and an orthogonal acceleration time of flight (TOF) mass spectrometer. A hexapole collision cell, between the two mass analysers, can be used to induce

fragmentation to assist in structural investigations.

Ions emerging from the second mass analyser are detected by the microchannel plate detector and ion counting system.

A PC computer runs the MassLynx NT software system to control Q-Tof micro, and to acquire and process data.

Ionisation Techniques

Using the Micromass Z-spray atmospheric pressure ionisation (API) source, two 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 vapourised 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 millilitres/minute can be accommodated without splitting the flow.

Electrospray

Electrospray ionisation (ESI) takes place as a result of imparting a strong electrical charge to the eluent as it emerges from the nebuliser. An aerosol of charged droplets emerges from the nebuliser. 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”).

Specifications

ROOM LOCATION

Dimensions

The Micromass Q-Tof micro MS is 180 mm wide by 635 mm deep by 1163 mm long and weighs 200 kg. It is mounted on 6 supporting feet. An external Edwards EM28 requires an additional 650 mm by 200 mm of floor space.

In the event that the unit needs to be lifted, the side panels should be removed and suitable lifting bands passed beneath the bottom of the frame. These should be attached to a suitable device (hoist etc.) to raise the analyser unit in a safe and controlled way. Only trained personnel with the correct equipment should carry this out.

A separate table 1200 mm by 730 mm is supplied for the computer terminal.

Doorways through which the instrument is to be transported should be a minimum of 820 mm wide.

In the laboratory a minimum clearance of 500 mm should be allowed all round the bench for service access, apart from at the rear of the instrument where 900 mm is required.

Note: The instrument should not be placed close to heavy machinery (compressors, generators etc.) which give excessive floor vibration.

Environment

It is recommended that the instrument be sited in an air conditioned laboratory, in a draught free position and away from excessive amounts of dust.

General

Altitude: upto 2000m

Pollution degree 1 in accordabce with IEC 664

Rotary Pump

15° to 40°C

Instrument

The maximum ambient laboratory temperature should not exceed 30°C, optimum temperature lies in the range 19° - 22°C. Short term (1.5 hour) variations should be no more than 2°C.

The relative humidity should not exceed 70%.

Heat dissipated into the laboratory from the instrument is about 1.2 kW.

The instrument conforms to IEC 1010 - 1, Pollution Degree 1, and Installation Category II.

Magnetic Fields

OA-Tof instruments are relatively tolerant to stray magnetic fields. We would advise an upper limit of 10 Gauss for both AC and DC components of magnetic field measured at the mass spectrometer.

Radio Emissions

The instrument should not be placed within a RF field greater than 0.2 V/metre. This approximates to a 1 W hand held unity gain transmitter at a distance of 10 m.

Possible sources of RF emission include RF linked alarm systems or LANs, portable telephones and hand held transmitters.

Water Supplies

The heat dissipated into the cooling water is about 400 Watts . The water flow required to dissipate the heat generated by the turbo pumps is 35 L/hour for an inlet temperature of

about 200 C or 23 L/hour at an inlet temperature of about 150 C assuming an outlet temperature of about 300 C.

The water may be supplied by a recirculating chiller with the following characteristics:-

• Heat dissipation into system: 400 W
• Temperature stability: +/- 2°C
• Minimum reservoir volume: 5 L
• Minimum supply pressure: 10 psi (outlet at atmospheric pressure).
• Maximum supply pressure: 60 psi
• Minimum flow rate at 15°C: 0.4 L/min

The above assume that the outlet water temperature will be no more than 30°C. Inlet water temperatures below 15°C are not recommended since excessive condensation may form on exposed pipework.

Alternatively, when there is a cooled water supply available it may be used either directly through the instrument or indirectly via a water-to-water heat exchanger. In this latter case the chilled water supply to the heat exchanger must be at least 10°C below the required inlet temperature for the instrument.

One inlet and one outlet are required for the instrument. Reinforced 10mm (3/8 inch) flexible hose is preferred.

To prevent blockage of the water pipes suitable in-line filters will be required to remove particulate matter from town water supplies when these are used.

Operation above 2000 metres altitude may adversely affect the cooling of the system.

Power Requirements

The instrument requires a single phase 50 - 60 Hz, 230 V nominal power supply rated at 13 A (UK) or 15 A (Europe).

An additional single phase 50 – 60 Hz, 230 V or 115 V nominal power supply rated at 5A (UK) is required to run the embedded PC.

In the USA and Canada a single-phase 50 – 60 Hz supply at 230 V phase to neutral fused and rated at 15 A is required. Alternatively two phases of a 50 – 60 Hz 208 V phase to phase, 3 phase supply, rated and fused at 15 A may be used. It is mandatory that no other apparatus is connected to this supply.

Circuit breakers are an acceptable alternative to fuses. The supply should be terminated in the laboratory no more than 2 m from the instrument with either a wall mounted isolator or socket and plug to be fitted to the instrument.

Other supply voltages can be accommodated using a transformer to change the primary supply voltage to 230 V. Advance notice is required and Micromass should be contacted.

On single-phase supplies the power supply should ensure that the line and neutral wires cannot be transposed.

On pump start-up currents of up to 30 A may be drawn for several seconds. Time delay fuses and breakers are recommended to prevent nuisance tripping.

A safety earth (ground) correctly rated must be provided in all cases.

Data system components, chromatographs, syringe pumps etc. should be connected directly to laboratory power outlets (no ancillary outlets are provided on the instrument).

A residual current device (RCD) is recommended for additional protection. In the case of instruments fitted with a transformer the RCD should be fitted in the supply side of the transformer.

Supply brownout should not fall to less than half main voltage for greater than 20 msec duration.

Gases and Regulators

Nitrogen

The instrument requires oil free dry nitrogen regulated at 7 bar (100 psi) minimum outlet pressure to provide nebulising and drying gas to the instrument.

During API operation typical usage of nitrogen is about 400 L/hour, but under high flow rate conditions (Megaflow/APcI) this may increase to 650 L/hour. This equates, approximately, to the consumption of a large cylinder of compressed nitrogen each day and it may be preferred to use a liquid nitrogen dewar which may last several weeks.

Collision Gases

Typically Argon is used as the collision gas for CID experiments. This should be 99.9% pure, regulated at no more than 50 psi. Connection is via 1/8 inch OD stainless steel or copper tubing (NOT SUPPLIED).

Exhaust Outlets

Rotary Pump Outlet

The rotary pump exhaust outlet must be vented to the atmosphere external to the laboratory clear from any air intakes for air conditioning systems. A 12 mm (1/2 inch)

hose connection is required. If the length of exhaust exceeds 4 m then the internal diameter of the pipe should be increased to 48 mm (2 inch) for the excess distance.

Nitrogen Outlet

Severe damage to the instrument will result if the electrospray/APcI exhaust is connected to the rotary pump exhaust line. This will occur when the nitrogen supply is off and rotary pump oil vapour will migrate via the source exhaust to the ion source and then through the sampling orifice into the quadrupole and gas cell assembly.

A separate exhaust for the ion source gas (nitrogen) must be provided to the atmosphere external to the laboratory clear from any air intakes for air conditioning systems. A (6mm OD) hose connection is required. If the length of exhaust exceeds 3 m then the internal diameter of the pipe should be increased to 12 mm (1/2 inch) for the excess distance.

Performance Specifications

Time of Flight Mass Resolution, Positive Ion

5000 (FWHM) on (M+H)+ ion from Leucine Enkephalin.

Time of Flight Mass Resolution, Negative Ion

5000 (FWHM) on (M-H)- ion from Raffinose.

Full Scan MS Sensitivity, Positive Ion

The signal height obtained from a sample consumption of 200 fmol of horse heart Myoglobin (16952 Da) will be greater than 166 ion counts on the most intense peak in the charge state envelope.

A solution of 200 fmol/µL horse heart Myoglobin (in 50/50 acetonitrile/water + 0.2% formic acid) will be introduced at a flow rate of 5 µL/min .

Full Scan MS Sensitivity, Negative Ion

The signal height obtained from the sample consumption of 1 ng of raffinose will be greater than 200 counts on the (M-H)- peak at m/z 503. This will correspond to a signal to noise ratio of greater than 200:1 (after a 1x3 smooth).

The instrument will be tuned at 5000 resolution (as demonstrated in specification 2a) and a

solution of 5 ng/L in 50/50 acetonitrile/water (no additives) will be introduced at 10 µL/min.

Full Scan MS/MS Sensitivity, Positive Ion

The signal height obtained from a consumption of 20 fmol of [Glu ¹ ] -Fibrinopeptide B (1569 Da) will be greater than 6 counts on the most intense yî sequence ion from the MS/MS spectrum of the doubly charged precursor ion.

This will correspond to a signal to noise ratio of greater than 30:1 (after a 3x9 smooth) on the most intense yî sequence ion.

A solution of 100 fmol/µL will be introduced at a flow rate of 5 µl/min.

Mass Measurement Accuracy (with internal reference)

The RMS error between the measured and the accepted masses of peaks which have sufficient intensity and are free from interference from other masses, over the range from 150-900 Daltons, will be less than 5 ppm.

One suitable peak of known mass will be used as an internal reference.

The instrument will be tuned at 5000 resolution as demonstrated in specification 1a.

Electrospray Option - Nanoflow

Full Scan MS/MS Sensitivity, Positive Ion

The signal to noise from a consumption of 2 fmol of [Glu ¹ ]-Fibrinopeptide B (1569 Da) will be greater than 30:1 (after a 3x9 smooth) on the most intense yî sequence ion from the MS/MS spectrum of the doubly charged precursor ion.

A solution of 500 fmol/L concentration in MeOH/H ₂ O + 0.2% formic acid solution and with glass micropipettes with 1 or 2 gm tips will be used.

The integration period per spectrum will be about 5 sec and data will be summed over a period appropriate for the required consumption of sample.