Collecting Fractions
Fraction Collection Control via an MS

Mass Traces can be used to selectively collect certain substances in fractions. This selective collection is possible since the occurrence of peaks with data acquisition via Mass Spectrometers depends much more selectively on the corresponding masses than it depends on the wavelength with UV Detectors.

It is possible to use certain mass traces at specific times to trigger the fraction collection. For this purpose, online extraction of mass traces is required (see Using Mass Spectrometers  Extracting Mass Traces Online). The following program requires five channels for online extraction of mass traces:

; Definition of the minimum/maximum mass and of the filter index for the channels MS_01 to MS_05:

 MS_01.MinMass = 243.5

 MS_01.MaxMass = 244.5

 MS_01.FilterIndex = 2

 MS_02.MinMass = 145.5

 MS_02.MaxMass = 146.5

 MS_02.FilterIndex = 2

 MS_03.MinMass = 164.5

 MS_03.MaxMass = 165.5

 MS_03.FilterIndex = 2

 MS_04.MinMass = 178.5

 MS_04.MaxMass = 179.5

 MS_04.FilterIndex = 2

 MS_05.MinMass = 192.5

 MS_05.MaxMass = 193.5

 MS_05.FilterIndex = 2

;********************************************************************

;*Definition of triggers for fraction collection starts here

;********************************************************************

;Definition copied from template <Timebase>\FractionCollectionTemplate!

;FracStart: Start of fraction collection

 Trigger FracStart  FracStartDetected

 Collect

 Log SFM_A.Tray

 EndTrigger

;TubeChange: The fraction is collected to another tube when the current tube is full

 Trigger TubeChange FracTubeChange

 Drain

 SFM_A.TubePosition = FractionCollection.TubePosition

 Collect

 EndTrigger

;FracEnd: End of fraction collection

 Trigger FracEnd FracEndDetected

 MovementMode = InterruptAndEject

 Drain

 SFM_A.TubePosition = FractionCollection.TubePosition

 EndTrigger

;********************************************************************

;*Definition of triggers for fraction collection ends here

;********************************************************************

; Maximum liquid level in a tube in ml:

 PumpDevice = "Pump"

 TubeMaxVolume = 10

; Maximum number of installed fraction tubes:

 FractionCollection.TotalNumberInstalled = 240

; Basic fraction collection parameters:

 MaxTubesPerFraction =  Unlimited

 TubeWrapping = No

 TubeChangeDuration =  2.0 [s]

 ChannelEvaluation =  All

; Delay time between detector output and switching valve or tube:

 DelayTime = 0.8

 DetectionChannel2.OffsetTime = 0.0

 DetectionChannel3.OffsetTime = 0.4

; Conditions for online peak recognition at program start:

 CollectFractions =  Yes

 DetectionChannel2.Name = "UV_VIS_01"
 ;Slope at peak start [mAU/s]:

 DetectionChannel2.PeakStartSlope = 2.000

 ;Minimum signal height at peak start [mAU]

 DetectionChannel2.PeakStartThreshold = 5000.00

 ;Slope after peak maximum [mAU/s]

 DetectionChannel2.PeakMaxSlope = -5.000

 ;Slope at peak end [mAU/s]

 DetectionChannel2.PeakEndSlope = -4.000

 ;Maximum signal height at peak end [mAU]

 DetectionChannel2.PeakEndThreshold = 5000.00

 ;Signal mst be less than this threshold value

 ;before a new peak start can be recognized [mAU]

 DetectionChannel2.ThresholdNoPeakEnd = 10000

 ;Baseline drift correction:

 DetectionChannel2.BaselineOffset = 0.000

 DetectionChannel2.BaselineDrift = 0.000

; Conditions for online peak recognition for the MS detection channel:

 DetectionChannel3.Name = "MS_01"
 DetectionChannel3.PeakStartSlope = 2.000
 DetectionChannel3.PeakStartThreshold = 10.00
 DetectionChannel3.PeakMaxSlope = -5.000
 DetectionChannel3.PeakEndSlope = -4.000
 DetectionChannel3.PeakEndThreshold = 5.00
 DetectionChannel3.ThresholdNoPeakEnd = 200
 DetectionChannel3.BaselineOffset = 0.000

 DetectionChannel3.BaselineDrift = 0.000

; Separation start with injection and acquisition start

0.000 UV.Autozero

 Wait Sampler.Ready and MS.Ready

 Inject

 3DFIELD.AcqOn

 UV_VIS_1.AcqOn

 MS_01.AcqOn

 MS_02.AcqOn

 MS_03.AcqOn

 MS_04.AcqOn

 MS_05.AcqOn

; Basic fraction collection parameters:

 CollectFractions =  By_Peak

; Change of the detection channel according to the expected substances

3.20  DetectionChannel3 =  "MS_02"

3.7   DetectionChannel3 =  "MS_03"

4.3   DetectionChannel3 =  "MS_04"

5.5   DetectionChannel3 =  "MS_05"

; End of data acquisition

10.000 3DFIELD.AcqOff

 UV_VIS_1.AcqOff

 MS_01.AcqOff

 MS_02.AcqOff

 MS_03.AcqOff

 MS_04.AcqOff

 MS_05.AcqOff

 CollectFractions =  No

 End

 Notes:

The trigger block used in this program example refers to the Dionex Sample and Fraction Manager (SFM).

In the example, DetectionChannel1 has not been used as the first detection channel because '1' and 'I' look identical when Courier is the selected font.

If the above Program is used, fractions would be collected at the following retention times, provided that a peak occurs within the following mass traces:

(Usually, the desired mass peak occurs only once within the corresponding time interval - this is assumed in the above table. Otherwise, the positions of the collection vials will change accordingly.)

This program example for mass-controlled fraction collection presumes that the same substances will be collected in all samples. If there are different substances in the samples, fraction collection via a mass channel needs to be adapted accordingly. For more information, refer to  Fraction Collection Control via an MS for Different Samples.

For more program examples, refer to:

 Program Example (One Detection Channel)

 Program Example (Two Detection Channels)

For an overview of the fraction collection topics, refer to  Collecting Fractions.