sajbicz
☆    

Czech Republic,
2016-07-22 14:21
(2805 d 23:06 ago)

(edited by sajbicz on 2016-07-22 15:32)
Posting: # 16513
Views: 3,992
 

 Which order in spiking blank matrices? [Bioanalytics]

Hey guys.

Glad to found this forum! I have a seemingly silly question. We are discussing after yrs of the practice which order in spiking blank plasma is the best.

My way - spiking of the matrix: into the eppendorf tube is pipetted a volume of blank matrix, then is spiked by solution with analyte.
(This is imho better and safer approach, we need not worry about sorptions or evaporation of the solvent)

Way of my older colleague - spiking of empty tube: into the eppendorf tube is pipetted a volume of solution with analyte, then a volume of blank matrix.
(I guess this approach has a flaws mentioned above, and it's just seems to me illogical. It could be useful if the solvent has a high content of an organic matter to ensure an immediate homogenization without precipitation, but no one of us is developing methods like that if possible, right?)

I'll be glad if there will appear some clear answer.
Thanks in advance.
Ohlbe
★★★

France,
2016-07-23 17:24
(2804 d 20:02 ago)

@ sajbicz
Posting: # 16516
Views: 3,229
 

 Which order in spiking blank matrices?

Dear Sajbicz,

❝ We are discussing after yrs of the practice which order in spiking blank plasma is the best.


When spiking large volumes of plasma into a volumetric flask: the usual practice is to half-fill the flask with plasma, add the working solution, mix and make up to the full volume.

When spiking single separate tubes: each approach has its pros and cons. The one positive thing I see in your colleague's approach comes in the case somebody talks to you at the wrong moment, you get distracted and you don't know where you had stopped and which tube has been spiked or not. If you first add the working solution to the tube you immediately see which tube has been spiked. It avoids double spiking or no spiking at all.

Did you ask him why he was doing it this way (apart from "this is how I've always done it and you're not going to teach me my job") ?

Regards
Ohlbe
sajbicz
☆    

Czech Republic,
2016-07-27 14:08
(2800 d 23:18 ago)

@ Ohlbe
Posting: # 16519
Views: 3,077
 

 Which order in spiking blank matrices?

Dear Ohlbe,
thank you for your response.

I'm a former chemist from API development so my approaches are encumbered by that :) Due to that I take into consideration the properties of the analyte primarily. Comfortable work is secondary for me. That's partly why I've asked.

What you wrote is exactly the same what my colleague told me - prevention against distraction. Sure I spoke with him, moreover with all heads of our department, so that was funny ;)

This approach is highly preferable here although that that mine still seems to me a bit safer. But I decided that I'll do it like everyone else. Practice will show whether this is an appropriate approach for the analytes.

Thank you again. Have a nice day.
Ladi
☆    

Thailand,
2016-08-01 09:18
(2796 d 04:08 ago)

@ sajbicz
Posting: # 16531
Views: 3,037
 

 It can sticks to the container

Dear members,

Our lab used to do pipetting analyte into tube first, then adding blank plasma. People liked it because, as you guys mentioned, you can actually see if solution has been added or not. However, there was one project where we had to do the spiking in glass tube sitting in ice-water bath to control temperature. Results were poor especially at low concentration. After many testing to find problem, we were able to conclude that the analyte spiked to glass tube at low temperature adsorbed to glass. Adding plasma first and followed by solution of analyte solved our problem. Now, we only do it in this order with any molecule.

Learned it the hard way,
Ladi
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