Analytical Method Calculations ( GC & HPLC )

Hey guys, today here i wanna deliver something related to Quality Control [ QC ], which will be felt extraordinary to many process engineering beginners,

When a Process Engineer is considered, the final destination of a Process Engineer in a Pharma Company will be always Vice President of the company, as always the Head carder of the Company will be occupied by manufacturing team only. So every process engineer should excel the other aspects of pharma also, like having a good knowledge on QC operations, QA role by adhering to cGMP, safety related things etc,

And now i gonna share you some of my knowledge related to QC, as most likely i'll always interested in calculations, here i gonna give you some basic calculations.




Assay by Titrimetry :

Assay is nothing but content of the desired material in the given sample, assay can be calculated on two basis, by

1) Titrations and
2) HPLC / GC

Assay by Titrations = [Titrate value of (sample - blank) x M x F x 100 x 100 ] / [Ws x (100- LOD)]

Where,
M  - Molarity of Volumetric Solution,
Ws - Weight of solution,
F  - Factor for drug substance,
LOD - Loss On Drying.




Assay content by HPLC :

Assay  =  [ At x Ws x P x (100 - LOD of std ) ] / [ As x Wt x ( 100 - LOD of sample) ],

Where,
At  -  Area of the sample,
As - Area of the Standard,
Ws - Weight of the standard,
Wt - Weight of the Sample,
P - Potency or Assay of standard.

RS[Related Substances] by HPLC :

There will be mostly two formulae which will be helpful for calculating RS by HPLC,

1) Calculating known impurity Level,
2) Calculating unknown impurity level.

Calculating known impurity level :

% of known impurity  =  ( Ri / Rs ) x 100 x RF

% of unknown impurity = ( Ri / Rs ) x 100

May be right now, you may get a doubt 

What are these known impurity & unknown impurity ?

 Known Impurity : The impurity which will be detected at a known RRT is called known Impurity, 

Unknown Impurity : The impurity which will be detected at a unknown RRT is called Unknown impurity.

Another Query you may get here, & i.e., 

What is RRT ?
RRT stands for Relative Retention Time
Usually our sample for which HPLC need to be performed is pressurized into a column and while this process under progress, some peaks will be observed at some particular times based on the Standard solution,
and the time interval denotes the Retention time, the ratio of the sample peak Retention time to the Standard peak Retention time is nothing but our Relative Retention Time.

Ri - Area of each impurity Peak in the chromatogram of the sample solution,

Rs - Sum of areas of Main drug and all impurity Peaks in the chromatogram of the sample solution,

RF - Response Factor.

Total Impurities = Sum of known impurities + Sum of unknown impurities.



You may also like:

How to perform Material balance ? 

Calculate LMTD correction factor

RS[Residual Solvents] by GC :

This is most used term while describing a dry product Purity & LOD, Usually RS by GC will give a clear idea about how much of solvent is being washed away from the material during a filtration, also it characterizes the drying efficiency, 

RS by GC can be calculated as

 = (At/As) x (Vol. of solvent taken x Density/10ml) x (0.1/10ml) x (Dilution of sample/Weight of sample) x (10^6)

At= Area of the solvent in the sample - Blank

As= Area of the solvents in the standard -blank 

Note: Volume of the solvents taken should be mentioned in microliters 

As we are multiplying with 10 power 6 we can get the results in PPM

That's it...........!!!

If you understood say Cheer's, If you don't then feel free to message me....!!

Comments are most appreciated.................!!!!

Related Articles:

Bond Energy calculations 

Calculate Product Assay in liquid ?

Calculate NPSH - Net Positive Suction Head

How to Calculate height required for vapour column of batch reactor ?

About The Author

---

Hi! I am Ajay Kumar Kalva, Currently serving as the CEO of this site, a tech geek by passion, and a chemical process engineer by profession, i'm interested in writing articles regarding technology, hacking and pharma technology.
Follow Me on Twitter AjaySpectator & Computer Innovations