Jump to content

Recommended Posts

Anyone use pipettes for accurate sample results? If so, where is a good source for finding them?

Thanks,

Mike

I use a Taylor pH test (midget comparator K-1285-2) whose titrant is dispensed with a type of pipette. The pipettes are available in a number of titrating water tests sold by Taylor and separately for small change (a dollar or two) but I imagine any pharmeceutical supply house carries these and others as well. The pH test's pipette (see link below for photo) can be threaded to a 3/4 oz bottle of titrant. However, I don't much care for them -- you have to be careful in the amount of titrant that is drawn up and be sure it's emptied completely into the sample tube (the 5 and 10 mL square tubes used in the midget comparators are also a bit tricky to work with -- they don't like to stand up on a counter top). Other companies sell higher quality volumetric pipettes but I have no experience with these.

http://www.taylortec...mentPartID=2076

Link to post
Share on other sites

Polyvue,

I was thinking more along the lines of using a volumetric pipette to deliver a more accurate volume of water to be tested, ie: 10, 25, and 44 ml.

Thanks,

Mike

Hello Mike,

Got it. Interesting proposition. I rely on the marks on the graduated cylinder (sample tube) supplied with the tests and try to line up the meniscus (lower portion of c curve observed near the top of a solution) with those marks. Do you think that tweaking the sample volume might produce a significant increase in test result accuracy?

Greg

Link to post
Share on other sites

Hello Mike,

Got it. Interesting proposition. I rely on the marks on the graduated cylinder (sample tube) supplied with the tests and try to line up the meniscus (lower portion of c curve observed near the top of a solution) with those marks. Do you think that tweaking the sample volume might produce a significant increase in test result accuracy?

Greg

Most likely it will not have a major affect on the sample results. I guess it is just the nerd side of me coming through. I was able to get my hands on a 25 ml pipette, and ordered a manual pipette pump off of eBay for filling it.

Link to post
Share on other sites

I use a 25 ml volumetric pipette for dilution tests, i.e., testing the strength of the liquid chlorine I buy. For daily water testing I use the graduated cylinders which came with my test kit. Once you get the hang of placing the meniscus, or at least place it consistently, the accuracy provided is close enough.

Link to post
Share on other sites

If you use Taylor kits how about one of these!

Has anyone here used the so-called sample-sizer? When I look at the demo pics it appears that once this plunger instrument is seated in the tube, the excess sample solution just dumps out and down its sides (and all over the hand that holds it!) My thought was that in the time it takes to rinse or wipe off the tube's exterior (and my hand) from the overflow I could have already apportioned the sample and lined up the meniscus.

And, of course, the sample-sizer can only be used for Taylor's standard round 25 mL tubes. I don't think they have an equivalent tool that fits other sizes and shapes.

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...