Questions about a shodex column

Record: 424

Category: Specifications
Product: SH1821
Sample:

Question
I purchased a Shodex SH1821 column with the SH-G guard column through
Phenomenex. As described in the litrature, the column has a maximum of a 50
bar (5 MPa) backpressure and a recommended temperature of 50-60 deg C (but
up to 95 deg C).

We are concerned about our new column because, while running it with the
guard, at 50 deg C and 0.8 ml/min (0.01 N H2SO4 as in CoA) the system back
pressure is reaching ~43 bar (4.3MPa). I consider this high for a new
column and I’m concerned that this is not what I should expect. The
certificate of analysis (gel lot number 080513, column serial number
H811040) showed 32 bar (3.2 MPa) on the system running at 50 deg C and 1.0
ml/min. I’ve learned from Phenonenex that Shodex does not use the guard
column during certification, which is to be expected.

We previously discussed this with Phenomenex but there only suggestion was
that we could try their Rezex H column. This will not due primarily because
I selected your column for the exclusion limit. The Rezex column is more
like the Shodex SH1011 with an exclusion limit of 1000.

Can Shodex please offer some guidence concerning this column. The overall
concern is that the expected lifetime will be significantly reduced if it is
already running at such a high back pressure. Other than the inclusion of
the guard column what else might explain the significantly increased back
pressure between the certification and first use? Other than the high back
pressure the column appears to work perfectly for what we needed.

Answer
Regarding the column pressure, the maximum pressure stated in the manual is the actual column pressure and not the system pressure (guard+ pressure created by other part of HPLC/detector system). This means as long as column pressure is within the maximum pressure, there should not be potential damage to the column.

However, observed increased pressure (~1 MPa) by guard column seemed to be little high.. I’d like you to check the column back pressure of the analytical column and guard column individually. Another potential increase of back pressure is the connection tubing. We would recommend you to use 0.25 mm i.d. tubing to connect guard and analytical columns. Please let me know the result and any further questions you may have.

 
 
Additional Comments
So the results of our analysis:
1) Starting 44.4 bar
2) Disconnect before guard column 6.9 bar
3) After guard column (guard only) 9.1 bar
4) After guard and SH1821 39.7 bar
5) Total system without columns 13.8 bar

From this analysis it would seem that there is only ~30 bar over the column at 50deg C and 0.8 ml/min. This is expected so it would seem that there is not a problem with the column. We have a new Agilent 1200 series (just 2 weeks old). The system apparently has 13.8 bar without any column in line. The system is plumbed with 0.17mm ID tubing, The only thing that seems strange to me is the doubling of back pressure with the UV absorbance cell addition (6.9 bar >>13.8 bar).

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