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RegisterCorrect method for preparation of stock solution [Bioanalytics]
Pl read my response in blue.
Regards
Chirag
❝ In our lab when we prepare stock solution we weigh an approximate quantity of standard and add an equivalent amount of solvent in it. For example, we weigh about 10.3 mg of reference standard (when trying to weigh 10.00mg )and add 10.3 ml of solvent with a calibrated pipette to prepare a 1mg/ml solution. From that solution we prepare our calibrators.
To the best of my understanding this practice is not acceptable. Volumetric flasks have to be used upto their graduation mark to get accurate dilutions.
❝ However, an auditor raised the objection that in our case the final volume of the solution would change since the volume occupied by solute also adds to the final volume and hence the strength we finally get is different from what we intended. They suggested using a volumetric flask (say 10ml), weigh an approximate quantity (say 10.3mg as in our case) but make up volume to 10ml so final concentration is 10.03mg/ml which should be used for preparation of further dilutions.
The volume of stock can be adjusted for preparing subsequent dilutions keeping the final volume according to the graduation mark of the volumetric flask used
❝ Please let me know if this difference in the method of solution preparation is significant enough to invalidate our previously done studies?
If the subsequent dilutions are prepared in a similar way as indicated, the concentrations of the calibrator, QCs and unknown samples may be incorrect
❝ Secondly, which method is more practical to work with?
The one suggested by the auditor
Complete thread:
- Correct method for preparation of stock solution Ionsource 2013-03-11 17:25
![[Mix]](https://static.bebac.at/img/mix.png "open in Mix view")
- Volumetric flasks Helmut 2013-03-11 17:55
- Volumetric flasks Ohlbe 2013-03-11 18:45
- Volumetric flasks Ionsource 2013-03-15 18:10
- Volumetric flasks Ohlbe 2013-03-11 18:45
- Correct method for preparation of stock solutioncakhatri 2013-03-12 18:35
- A vote for both approaches ElMaestro 2013-03-16 19:58
- Volumetric flasks Helmut 2013-03-11 17:55
Ing. Helmut Schütz