switching the mobile phase from acetonitrile to …v~acetonitrile...gl sciences lc technical note...
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LC Technical Note
GL Sciences Inc.Switching the mobile phase from Acetonitrile to Methanol
Example 1.Analytical Conditions:
System: LC800 HPLC
Column: Inertsil ODS-SP 5um, 150 x 3.0mmI.D.
Mobile Phase: CH3CN / H2O or CH3OH / H2O
Flow Rate: 0.4 mL/min
Column Temp.: 60C
Detection UV 360 nm
Injection Vol.: 10 uL
From the end of last year, the shortage of Acetonitrilesupply has been a topic in the HPLC industry. Oureconomy is now drawn into chaos, which was caused byAmerican financial crisis. All car industries are goingdown resulting in less production of Acrylonitrile as thecar industries uses a lot of Acrylonitrile during theirproduction of cars. Acetonitrile is a by-product ofAcrylonitrile and only from 2 to 3% Acetonitrile isgenerated when producing Acrylonitrile.We would like to introduce the important reminders onwhen switching the mobile phase from Acetonitrile toMethanol.
Attention!!!
1) The elution strength of an organic solvent may change.
=The elution strength of Methanol is weaker than
Acetonitrile.
2) The elution pattern may change.
= Conduct qualitative analysis again to confirm.
3) Back pressure will definitely increase.
= Use a column that offers low back pressure.
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0 2 4 6 8Time (min)
010
20mV
olt
0 2 4 6 8Time (min)
010
20mV
olt
0 2 4 6 8Time (min)
010
20mV
olt
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60% Acetonitrile
60% Methanol
70% Methanol
= Mobile Phase Composition
1. Formaldehyde-DNPH( 100μg/L )2. Acetaldehyde-DNPH ( 100μg/L )
As you can see, the elution strengthbecomes weaker.
In addition, the elution pattern maychange depending on the sample.Back pressure will increase too.
The retention time can be optimized byincreasing the ratio (%) of an organicsolvent.
Back Pressure: 6.7 MPa (67 bar, 971 psi)
Back Pressure: 6.2 MPa (62 bar, 899 psi)
Back Pressure: 3.9 MPa (39 bar, 565 psi)
GL Sciences LC Technical Note
Inertsil provides the lowestback pressure in the world!Therefore, it is totallycompatible with Methanolmobile phase condition.
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0 20 40 60 80 100
Methanol Concentration (%)
Bac
k P
ress
ure
(Mpa
)
When changing the mobile phase, the elution pattern may change depending on the sample.Please refer to the 2 chromatograms below.The ratio (%) of an organic solvent was adjusted to obtain the same retention time.
Inertsil ODS-3
Inertsil ODS-4Inertsil ODS-SP
* Analytical Conditions used in the above comparison dataColumn: 5um、250 x 4.6mmI.D.Col Temp: 40 ℃Flow Rate: 1.0 mL/min
Back pressure comparison using Methanol
Commercially available C18 column
Even if the column specification were the same, when the packing material changes, the column back pressuremay increase. When the column back pressure increases, the following phenomena can be experienced;-Short column lifetime-Frequent instrument maintenance as high column back pressure deteriorates the instrument
Example 2.
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0 20Time (min)
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72% Acetonitrile 80% Methanol : Alkylbenzenes
: Polyaromatics
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GL Sciences LC Technical Note
When changing the mobile phase from Acetonitrile to Methanol, please make sure to set the flowrate lower than that of Acetonitrile.As you can see in the chart below, when using Methanol, maximal performance, minimum HETPcan be obtained when setting the flow rate at a low range.
Additional Information
Comparison of Organic Solvents
Theoretical Plates vs Flow Rate
Maximal performance can be obtained when setting the flow rate at a low range with Methanol
●:CH3OH / H2O = 85 /15▲:CH3CN / H2O = 65 /35