For the mico-pi-pettor we ended up using a 19 Ga stainless capillary
(McMaster-Carr in the states), sharpening the one end for the needle.
We used a thin walled 1/16" stainless tube as a sheath so we could fix a
1/16" to 1/8" swagelok reducing union to it, so we could attach it to
the holder (the 1/8" nut fits in nicely). Akin to what's on the
Isogeochem wiki for the sampling needle. We still had to flush it with
water after every sequence and bring it back up to 105% for the next
series. Note, the line is not as malleable as the one that Thermo
supplies--just stay out of the way as it runs ;)
On 6/24/2011 3:49 PM, Travis Horton wrote:
> Hi Chris,
> I have tried switching the capillary / SS lines at the bulkhead fittings
> such that He is now coming out the needle tip and the sample gas+He are
> going in the side-hole to the stainless line.
> I haven't seen any differences in data quality - but the needle clogs much
> less frequently due to the positive pressure. You want to keep a close eye
> on the flow rates - blanks/dummies - and 'spectra' though to be sure you
> don't have a partial/ephemeral clog somewhere else as well. When it rains,
> it pours on a GB from my experience.
> With the manual acidification - do you 'pull up' on the syringe prior to
> removing it from the exetainer (thus - hopefully - getting rid of those
> pesky drops of acid on the underside of the septum)?
> I've started doing this with good results, but I would prefer to restore the
> micro-pippeter - if I knew it would work for more than a week at a time...
> On 06/25/2011 7:21 AM, "gerard"<[log in to unmask]> wrote:
>> HI Chris--
>> You'd rather not over-tighten them, but that would show up as
>> puckering. I'm guessing the needle tip is bent a little out of shape.
>> The end should bend in a little, similar to Hamilton uL syringes.
>> Sometimes they get bent back or blunted. Alltech (excuse me, Grace
>> Discovery) had a sharpening stone for needles, and others might too,
>> just be careful using it. Me, I just use a small pliers to bend it in.
>> To make your own, you can look at:
>> take care,
>> On 6/24/2011 2:06 PM, Christopher Maupin wrote:
>>> Dear Listers,
>>> We're encountering a problem with our gasbench measuring needle. It's
>>> clogging every 2 days or so with usually single but sometimes multiple
>>> pieces of septa. We run carbonates (acidified by hand), primarily, as
>>> well as waters. When the needle isn't clogged we get exceptional
>>> precision using carefully weighed sample sizes. Are we tightening the
>>> exetainer caps too tight? Not tightly enough? I have tried different
>>> needle tip shapes. The exetainer/cap/septa product code is 9RK8W 12mL
>>> BORO x 100 from Labco, and the needle is the OEM thermo measuring needle.
>>> Chris Maupin
>>> Paleoclimate Lab, JGB 5.118
>>> Jackson School of Geosciences
>>> University of Texas at Austin
>>> 1 University Station C1100
>>> Austin, TX 78712
>>> [log in to unmask]
>>> Stable Isotope Lab: 512-232-4184
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