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Overview of the LCT Premier

The LCT Premier ^TM time-of-flight (TOF) mass spectrometer features a ZSpray source with electrospray ionization (ESI) and modular LockSpray ^TM interface.

The LCT Premier uses ion guide technology for optimum transfer of ions from the source to the orthogonal acceleration time of flight ( oa -TOF) mass analyzer. Ion detection is by dual microchannel plate detector assembly. Data is acquired by a 4.0 GHz time-to-digital converter (TDC) and histogrammed in an embedded PC. Instrument control and data acquisition is by the MassLynx ^TM software system.

lonization Techniques

Using the Zspray atmospheric pressure ionization (API) source, three techniques are available.

ElectroSpray lonization

Atmospheric Pressure Chemical lonization

Atmospheric Pressure Photoionization

Performance Specifications

Resolution in Positive Ion (V Mode)

Infuse mellitin at a concentration of 5 pmol /µL, in 50:50 acetonitrile :water + 0.2% formic acid, using a flow rate of 5 µL/min. Ensure that the intensity of the peak at 712 Da is <300 counts/s.

The peak at 712 Da should be resolved such that the mass divided by the peak width at half height is greater than 5000 when using a scan time of 1 s and an inter-scan delay of 0.1 s. At least 30 s of data should be summed.

Resolution in Positive Ion (W Mode)

Infuse mellitin at a concentration of 5 pmol /µL in 50:50 acetonitrile :water + 0.2% formic acid, at a flow rate of 5 µL/min. Ensure that the intensity of the peak at 712 Da is <300 counts/s.

The peak at 712 Da should be resolved such that the mass divided by the peak width at half height is greater than 10,000 when using a scan time of 1 s and an inter-scan delay of 0.1 s. At least 30 s of data should be summed.

Resolution in Negative Ion (V Mode)

Infuse raffinose at a concentration of 500 pg/µL in 50:50 acetonitrile :water , at a flow rate of 10 µL/min. Ensure that the intensity of the peak at 503 Da is <300 counts/s.

The peak at 503 Da should be resolved such that the mass divided by the peak width at half height is greater than 5,000 when using a scan time of 1 s and an inter-scan delay of 0.1 s. At least 30 s of data should be summed.

Resolution in Negative Ion (W Mode)

Infuse raffinose at a concentration of 500 pg/µL in 50:50 acetonitrile :water at a flow rate of 10 µL/min. Ensure that the intensity of the peak at 503 Da is < 300 counts/s.

The peak at 503 Da should be resolved such that the mass divided by the peak width at half height is greater than 10,000 when using a scan time of 1 s and an inter-scan delay of 0.1 s. At least 30 s of data should be summed.

Sensitivity in Positive Ion

In V mode, infuse 50 pg/µL of leucine enkephalin in 50:50 acetonitrile :water + 0.1% formic acid at a flow rate of 5 µL/min. Using a scan rate of 1 s, an inter-scan delay of 0.1 s and a mass range of 100 to 1000 Da , check that the resolution at 556 Da is greater than 5000 and the intensity is greater than 440 counts/s.

Switch the instrument to W mode. Check that the resolution is greater than 10,000 and the intensity is greater than 110 counts/s .

Sensitivity in Negative Ion

In V mode, infuse 500 pg/µL. of raffinose in 50:50 acetonitrile :water at a flow rate of 10 µL/min. Using a scan rate of 1 s, an inter-scan delay of 0.05 s and a mass range of 100 to 1000 Da , check the resolution at 503 Da is greater than 5000 and the intensity is greater than 240 counts/s.

Switch the instrument to W mode. Check that the resolution is greater than 10,000 and the intensity is greater than 60 counts/s .

Mass Calibration Accuracy

Infuse 50 pg/µL of sodium formate at a flow rate of 5 µL/min into the analyte probe.In V mode, ensure that the intensity is less than 300 counts/s and that the resolution is greater

than 5000. Run a calibration using the parameters listed in Table E-1, with no smoothing and no background subtraction, and using a centroid top value of 80%.

Table E-1 Mass Calibration Accuracy Parameters

Scan Type                               Continuum

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Scan Range                            150-900 Da

Scan Time                               5 s

Inter-Scan Delay                     0.1 s

Acquisition Time                      1 min

Save the calibration and then perform an acquisition for 1 minute using the same parameters. Combine and center the data, using 4 channels and a centroid top value of 80%.Measure at least 6 peaks and calculate the mass error ( ppm ) for each peak. Using the formula below, calculate the RMS error. The RMS error should be < 5 ppm .

Mass Measurement Accuracy

Infuse 50 pg/µL of sodium formate at 5 µL/min into the analyte probe . In W mode, ensure that the intensity is less than 300 counts/s and that the resolution is greater than 10,000. Run a calibration using the parameters listed in Table E-1. Create a calibration with no smoothing and no background subtraction, using a centroid top value of 80%.Save the calibration and then perform the following acquisition.

Infuse 50 pg/µL of leucine enkephalin into the reference probe and 500 pg/µL of raffinose into the ESI probe. Ensure that both probes give an intensity of <200 counts/s and that the resolution is greater than 10,000.

Acquire data in LockSpray mode for 25 minutes, using the following parameters:

Scan Type                               Continuum

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Scan Range                            100-1000 Da

Scan Time                              1 s

Inter-Scan Delay                     0.1 s

Acquisition Time                      25 min

Reference Scan Frequency   5

Reference Cone Voltage        100 V

Combine 12 scans at each of the following times: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20 minutes.

Using the Mass Measure feature an each of the spectrums, create a centered spectrum using lockmass 556.2771 Da . Calculate the RMS error using the formula below. The m/z value of raffinose is 527.1588 Da .

The calculated RMS error should be <3 ppm .

Chromatographic Signal to Noise

Note: This test should only be performed if there is already a suitable HPLC system installed.

Infuse 50 pg/µL of leucine enkephalin at a flow rate of 5 µL/min. Tune the ion beam in V mode and check that the resolution is greater than 5000.

Purge the HPLC using 75:25 methanol :water and 5 mM ammonium acetate. Connect the 10-µ.L sample loop, injection port, and waste tube to the Rheodyne injector. Connect a Waters Atlantis dC18 column (2.1 x 30 mm; 3 µM) between the injector and the probe. Condition the column for approximately 20 minutes.

Set up the following sample list acquisition parameters:

Table E-2 Sample List Acquisition Parameters

Scan Type                               Continuum

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Scan Range                            150-900 Da

Scan Time                               2 s

Enter-Scan Delay                    0.I s

Acquisition Time                      30 min

Make five injections of 1 pg/µL reserpine in 75:25 methanol :water and 5 mM ammonitun acetate, at 5 minute intervals.

Using the 609 Da mass chromatogram, calculate the peak to peak, 1 SD signal to noise ratio for each peak. The average signal-to-noise value should be >100.