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HPLC HINTS & TIPS for Chromatographers


Tip# 114: Pressure Drop Across an HPLC Column

Many of you prefer the useful HPLC tables that I provide over equations. So, instead of providing you with another equation, I have done the calculations for you.

To create this table, I had to make a few assumptions. Here they are: Pore Volume = 0.70; Flow Resistivity = 1,000; Linear Velocity = 1.44 mm/sec; Solvent Viscosity = 0.89 cP at 25C (Water). Pore Volume and Flow Resistivity will vary by column type. Obviously the backpressure will be higher with more viscous solvents (e.g. EtOH is 1.20 cP) and lower with less viscous solvents (e.g. ACN is 0.34cP). A Table of HPLC Solvent Viscosity values can be found here [ http://www.hplctools.com/lcsolvent.htm ]. Linear flow rates have been used for all column I.D.'s to better illustrate the relationship between column dimensions and flow rate. If you double the flow rate, then the pressure will approximately double as well.

Note that when run at traditional linear velocities, most 2.5u particles are within the maximum pressure limits of most HPLC systems (under 400 bars). Only the newer sub 2.0 micron particles used in long columns exceed the 400 bar limit. Naturally, you should optimize column efficiency when developing a method. The higher pressure limits of many UHPLC systems allow the use of higher flow rates with these particles.

Column I.D. (mm)

Particle Size (u)

Column Length (mm)

Flow Rate (mL/min)

Back Pressure (Bars)

4.6

5

250

1.000

89

4.6

5

150

1.000

54

4.6

5

100

1.000

36

4.6

5

50

1.000

18

4.6

3.5

250

1.000

182

4.6

3.5

150

1.000

109

4.6

3.5

100

1.000

73

4.6

3.5

50

1.000

36

4.6

2.5

250

1.000

357

4.6

2.5

150

1.000

214

4.6

2.5

100

1.000

143

4.6

2.5

50

1.000

71

4.6

1.9

250

1.000

618

4.6

1.9

150

1.000

371

4.6

1.9

100

1.000

247

4.6

1.9

50

1.000

124

 

 

 

 

 

3.0

5

250

0.430

90

3.0

5

150

0.430

54

3.0

5

100

0.430

36

3.0

5

50

0.430

18

3.0

3.5

250

0.430

184

3.0

3.5

150

0.430

110

3.0

3.5

100

0.430

74

3.0

3.5

50

0.430

37

3.0

2.5

250

0.430

361

3.0

2.5

150

0.430

217

3.0

2.5

100

0.430

144

3.0

2.5

50

0.430

72

3.0

1.9

250

0.430

625

3.0

1.9

150

0.430

375

3.0

1.9

100

0.430

250

3.0

1.9

50

0.430

125

 

 

 

 

 

2.1

5

250

0.210

90

2.1

5

150

0.210

54

2.1

5

100

0.210

36

2.1

5

50

0.210

18

2.1

3.5

250

0.210

184

2.1

3.5

150

0.210

110

2.1

3.5

100

0.210

73

2.1

3.5

50

0.210

37

2.1

2.5

250

0.210

360

2.1

2.5

150

0.210

216

2.1

2.5

100

0.210

144

2.1

2.5

50

0.210

72

2.1

1.9

250

0.210

623

2.1

1.9

150

0.210

374

2.1

1.9

100

0.210

249

2.1

1.9

50

0.210

125

> Bill Letter, 08/17/2011


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Copyright 2011, Chiralizer™ Services, L.L.C. All Rights Reserved. Chiralizer, Column Swapper & LC Spiderling are trademarks of Chiralizer Services, Newtown, PA   USA. *These "Hints & Tips" are protected by copyright and are not to be copied or duplicated in whole or part without the written permission of Chiralizer Services, LLC.