Acquity sample loop volume specifications?

RMJ

<p><span>Could someone at Waters post the specifications, or range of volumes that one can expect to encounter with various sample loops?</span></p><p></p><p><span>The reason I ask is that my 2-microliter loop measured 3.0-uL last week when characterized on the Acquity that I have been using for development work.</span></p><p></p><p><span>If I develop and validate a method using "full loop" mode, and then need to transfer that method to a different lab that has an Acquity where the loop may be 1.8-uL, then the difference between peak heights of the two systems may vary as much as 40% from the original 3-uL volume. This could be sufficient to create accuracy problems with the data, despite a "validated" method being used. Full loop mode is desired for validation activities due to the need to maintain low RSD of injection volumes for an assay validated to comply with my employers validation SOPs.</span></p><p></p><p><span>If I know the range limits or each respective loop size, then this potential for variation could be designed into experiments for the loop size selected for the assay method. </span></p>

lizh

Hello

I will get this asap. The typical tolerance for the best industry can achieve today is +/-0.001, but the tubing ID varies and I need to confirm that the 2 uL tubing is 0.005" SS (This would be 3.199 to 2.204 uL). As you can see the error is worse for the smaller ID's.

I have to hand the 5 and 20 uL loops, as follows.

The tubing I.D. for 5 uL loop is 0.009 inch - Volumetric tolerance resulting from ± 0.001 inch I.D. is ± 22% or 3.95 to 6.17 uL

A 20 uL loop made with 0.015 inch I.D. tubing resulting in ± 13% can vary from 17.4 to 22.8 uL.

Liz

RMJ

LIz,

Thank you for the quick response.

The specifications for the 10-microliter loop is of critical importance as well. Please provide those.

So am I correct to assume that the volume variation is primarily due to I.D. variation and not the length of the steel loop tubing?

Randy

lizh

Randy

Absolutely, the vendors check the lengths and I believe also weigh the cut and polished tubing, it is simply that the extrusion process has this level of variability. I am not saying the vendors are not careful, but simply there is no method to ensure the extrusion process is perfect.

I am sure engineers will get back to me shortly and I asked for all the loops and then I will publish on the web for everyone ...it is a good suggestion and I shall pursue.

Liz

lizh

Randy:

This is the reply from our Support Team. Looks like the 2 uL is 0.005" and the 10 uL is the same ID as the 20 uL loop. I will get a fuller answer, but here is a start.

Liz

Spare Part Number	Description	Nominal Volume (uL)	%Variance due to mechanical tolerances
430001264	Loop, Sample, 2uL	2 uL	50
430001311	Loop, Sample, 5uL	5 uL	30
430001326	Loop, Sample, 10uL	10 uL	18
430001320	Loop, Sample, 20uL	20 uL	18
430001325	Loop, Sample, 50uL	50 uL	11

lizh

Here we are, our Service Organization has provided a list of the loop ID's.

Liz

Loop ID

1ul - 0.004"

2ul - 0.005"

5ul - 0.007"

10ul - 0.012"

20ul - 0.012"

50ul - 0.020"

100ul - 0.030"

250ul - 0.030"

RMJ

Thank you. The information you have provided is very helpful.

Randy

Robert

Hi All,

We got the same comment with a client, for the full loop injection you can add an internal standard in order to have the same response factor with differente caracterization volumes, and that works good for Assays. For impurities methods that the area counts are the limits of quantification or detection, then a PLUNO, is the best recommended injection mode.

scurran

Hello,

I'm new to this forum and have seen this discussion posted. I am currently carrying out transfer of a validated test method which requires the use of a 1ul sample loop.

I was wondering if someone could update the previously included table for % variance to include 1ul loop or tell me what amount of variance is usually seen with a 1ul loop.

So far we have installed three different 1ul sample loops on our system. Each time we have carried out calibration of needle and loop volume and have observed that the measured loop volume for the three different loops are usually within a range of 1.5ul - 1.7ul. Considering that the loop is supposed to be 1.0ul this calculated volume is a large deviation from what is expected. Would I be right in assuming that if we use full loop injection mode and a 1.0ul injection volume that the injection volume would possibly be 70% more than the 1.0ul volume specified?

lizh

Here you go, I have attached the calculations, up to 50 uL loop. The issue decribed is one of the reasons why PLNO mode was developed. However, here are the values and the specifications, as a .pdf

Loop                ID

1ul                  .004

2ul                  .005

5ul                  .007

10ul                .012

20ul                .012

50ul                .020

100ul, 250ul     030

We really are at the limit of the technology, The specifications of the stainless steel tubing is ± 0.001 inch Internal Diameter (ID), and the industry can offer today. One inch of 0.009 inch ID has a volume of 1.04 µL.  For 0.010 inch ID the volume is 1.28 µL and for 0.0105 the volume is 1.42 µL.  And as you observe a small change in the ID across the tube can result in a significant change in the actual volume of the loop.

Let us know if this assist.

BR

Liz

scurran

Thank you for this information.