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Difference Between PURITY, ASSAY & POTENCY
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Purity:
It is calculated by area normalisation method, it can be directly find out by chromatograms obtained from HPLC.
% Purity = (Area of desired peak / Sum of area of all peaks) x 100
Assay:
It is calculated against standard. It may be of following types:
1) On as is basis = (Area of sample / Area of standard) x (conc. of standard / conc. of sample) x potency or assay of standard
2) On anhydrous basis = (Assay on as is basis / 100 – moisture) x 100
3) On dried basis = (Assay on as is basis / 100 – LOD) x 100
Potency:
100 – (moisture or LOD + residual solvents + heavy metals + sulphated ash + impurities)
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Dr. Amit Patel's Blogs...!!! 
07/12/2023 at 15:22
Very useful information
sir pls share any reference for this calculation if you have
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23/01/2023 at 07:21
Bravo, thank you sir, great summary
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22/04/2021 at 14:55
how to prepare 1000 stock solution for B
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01/05/2021 at 19:41
I am not getting your question. Please give details.
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05/05/2022 at 14:49
My drug is soluble all my multimedia solutions, but In monograph they selected dissolution media as 0.1 N, why ?
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22/04/2021 at 14:21
WHAT IS DIFFERENCE RT &RRT
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01/05/2021 at 19:43
RT is Retention Time
RRT is Relative Retention Time of any other peak against that of Main Peak RT
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14/04/2020 at 21:47
On what basis we consider the assay as 100% if assay is found more than 100%
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04/11/2015 at 12:19
If u r doing Lod then no need to perform res solvents
What if we have molecules with Na. Mg and Ca how potency can b calculated
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28/09/2015 at 11:40
Thank u sir,
pl clarify my formula for Potency
Potency = [100 – ( organic imp + Inorganic Imp)]
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08/09/2015 at 08:42
which case we use solvent free basis assay calculation take for hplc analysis
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15/07/2021 at 11:19
I also cant understand when assay calculated on both- solvent free basis and on anhydrous basis.
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28/08/2015 at 14:22
good and informative
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28/08/2015 at 14:21
It was nicee talking to you.
As discussed I am Dr.sridevi AGM biologics
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01/05/2021 at 19:39
Hello.. Can you please introduce yourself.. I am not recognize you.
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20/06/2015 at 11:53
For assay testing we doing std and sample preparation…i want take std weight 50mg so howmany mg difference wil take weight and sample also eg 5.0000g howmany will take difference
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02/03/2016 at 19:49
±10% is acceptable in both side.
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19/11/2022 at 14:49
Can u please give the refference.
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28/04/2015 at 18:26
But assay on anhydrous basis means with water contents according to USP i.e in case of Ciprofloxacin HCl contains water contents so assay is written as anhydrous basis.Now according to your formula;-
2) On anhydrous basis = (Assay on as is basis / 100 – moisture) x 100
it not gives the correct answer
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16/04/2015 at 20:27
1) On as is basis = (Area of sample / Area of standard) x (conc. of standard / conc. of sample) x potency or assay of standard
where is avg wt /label claim in above equation ……………..is it a incomplete equation………………………
sir will u clarify above doubt ?
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03/11/2015 at 16:48
on as is basis =(Area of sample / Area of standard) x (conc. of standard / conc. of sample) x potency or assay of standard x 100/ label claim
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24/11/2022 at 06:41
On as is basis calculation there is no salt form of compound is involved. It is like we calculate only compound of intrest
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08/05/2019 at 13:42
Calculation Above mentioned is related to API.
please note for formulation products, we check the Assay on as is basis generally.
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15/07/2014 at 02:09
Q. I’m student >please!Can anyone help me this problem,how can calculate for preparation?
* I want to prepare stock standard such as Cefaclor(working standard) for test pharmaceuticals productions.
-I have more information about this raw material(working standard)which must use it.that’s working standard with rate reference (95%)in pharma products
potency register it(working standard):96.19%(delete moisture)-assay:101.57 microgr/mg- moisture 5.38%.
While
Report certificate manufactor country productions assay:993 microgr/mg(calculate on anhydrous base)-moisture 5.1%.
what can I do or considerate to prepare stock solution(working standard).
from USP32 too:
M.W(cefaclor monohydrate=385.82)—M.W(Cefaclor anhydrate=367.81)
potency(950-1020)microgr/mg(calculate on anhydrous base)
acceptable for assay test pharmaceuticals productions range(90-120)%.
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12/07/2014 at 12:56
If we have to do API calculation for particular Sterile liquid batch, how do we claculate API quantity by considering assay of API.
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22/03/2014 at 17:25
Assay as per mass balance method
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28/02/2014 at 07:31
thanks
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19/09/2013 at 10:29
Dear sir,
Can i get any information about Elemental Impurities Specification Limits, Guidelines for Quantification & how to give a specification limit for Elements.
Regards
suman
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15/07/2021 at 11:23
For Residual of elemental impurities limit refer guideline ICH Q3D.
Basis on PDE valu e u can calculate specification limit.
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12/08/2021 at 11:48
Kindly refer ICH Q3 (E) guidance and USP general chapter ,
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21/08/2013 at 16:31
How to calculate Peak Purity?Purity angle and Threshold angle?
Some of Softwares give Similarity Index instead of Purity angle and Threshold angle..is there any difference between them??
is there any mathematical Formula for Peak Purity, Purity angle and Threshold angle?
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24/05/2013 at 16:56
Difference between as such basis and on dried basis then on dried basis meaning for LOD Added are removed explain the details.
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22/03/2013 at 20:22
When CRS/RS or any type of Reference std is not available then Reference standard can be prepared in own R&D deptt. Then potency of that standard is calculated as :100-(LOD/water+Residual solvent+sulphated ash+impurities). This calculation is only for the indigenously prepared Reference std.
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05/03/2013 at 20:34
so what is the last conclusion , can anybody clear??
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17/09/2012 at 16:49
is there any standard for slope of floor in the manufaturing area?
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18/09/2012 at 09:32
Purity:
It is calculated by area normalisation method, it can be directly find out by chromatograms obtained from HPLC.
% Purity = (Area of desired peak / Sum of area of all peaks) x 100
Assay:
It is calculated against standard. It may be of following types:
1) On as is basis = (Area of sample / Area of standard) x (conc. of standard / conc. of sample) x potency or assay of standard
2) On anhydrous basis = (Assay on as is basis / 100 – moisture) x 100
3) On dried basis = (Assay on as is basis / 100 – LOD) x 100
Potency:
100 – (moisture or LOD + residual solvents + heavy metals + sulphated ash + impurities)
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14/10/2012 at 11:04
Ur potency calculation is not adequate?????. Potency and assay of any API/material are the same ………In a more explanatory way Assay of an API is generally calculated against a known standard ODB,OAB or as is basis. While Potency of an API is the assay on as is basis……………….
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13/08/2012 at 09:25
Purity:
It is calculated by area normalisation method, it can be directly find out by chromatograms obtained from HPLC.
% Purity = (Area of desired peak / Sum of area of all peaks) x 100
Assay:
It is calculated against standard. It may be of following types:
1) On as is basis = (Area of sample / Area of standard) x (conc. of standard / conc. of sample) x potency or assay of standard
2) On anhydrous basis = (Assay on as is basis / 100 – moisture) x 100
3) On dried basis = (Assay on as is basis / 100 – LOD) x 100
Potency:
100 – (moisture or LOD + residual solvents + heavy metals + sulphated ash + impurities)
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20/06/2022 at 13:56
Hello,
If You check Betamethasone Sodium Phosphate BP standard COA , Potency As is not mention instead they gave some information which shows 0.3%, so 99.7 will be Potency Dried Or As is?
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16/06/2012 at 23:24
dear sir,
is there any method for benzoyl chloride by potentiometry:for assay,for free acid
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31/03/2012 at 16:04
Thanks alot , I hope th know how to calculate Asssay of material If it has Equation :
Each ml of ….M ( A ) solution is Equivalent to …….. gm of material
I am waiting for your reply
Mohammed Nasser
m_nasser2012@yahoo.com
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26/01/2014 at 22:34
Vol. consumed(Titrant) x Normality(Titrant) x Equivalent weight
——————————————————————————————- x100 =…………%
Weight of sample(mg)
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05/03/2012 at 21:20
gOod infOrmation…
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17/09/2011 at 16:51
with all above comments, what should I believe? Is above information correct or wrong?
I am also having a doubt.
In Assay formula, used Assay or Potency of standard. So, are Assay and Potency same?
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25/10/2011 at 18:44
assay calculated with water
potency calaculated with out water
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24/08/2011 at 16:25
This is useful.
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09/08/2011 at 22:43
Nice sir
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03/08/2011 at 22:41
1 .Purity formula is incorrect: All blank peak should be minus from sum of all peak and calculated with % total area calculation. For further details refer Water Empower.Also refer 21 CFR US FDA
2. For Assay calculation : Dried basis is OK but anhydrous basis, Sulphated ash and residual solvent can be minus.
3. Potency formula is incorrect.
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23/04/2012 at 12:23
If minus residual solvents in assay it will become :”assay by solvent free basis”
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30/06/2011 at 09:42
can u please send me the calculation formula of assay on as is basis.
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10/05/2011 at 10:58
After almost 3 months, you still haven’t enlightened us with the issue on hand.
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25/02/2011 at 08:01
It is hard for me to believe that potency is “100 – (moisture or LOD + residual solvents + heavy metals + sulphated ash + impurities)”!
I am working for a government regulatory body for pharmaceutical products and this formula always pops up almost automatically everytime when the product being registered has come from India.
I have nothing against Indians but on the 15 years experience I have in the “business” of drug registration, I have not yet came across the formula given above from any reputable reference!
1. Do you have any reputable reference to back up you formula?
2. Why is this methodology only comes from India (and also Pakistan)? No other country uses this in their product formulation.
3. 1% moisture content is equivalent to a 1% loss of potency? This is debatable.
Looking forward to your answer, thank you!
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14/10/2012 at 11:12
Hi dear u can see my comment above. Moreover potency/concentration factor/Assay of an API are the same value(synonyms)…More deeply Assay of an API is reported on as is basis/OAB/ODB However Potency is always calculated only on as is basis. Hence if assay of any API is calculated on as is basis then this value can also be called as potency of that API.
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29/01/2011 at 12:16
On as is basis = (Area of sample / Area of standard) x (conc. of standard / conc. of sample) x potency or assay of standard
In this case how we can use assay of standard, as per my experience we should use potency only
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13/10/2010 at 13:17
Thanks sir for preparing such type of imp information
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12/09/2010 at 23:14
thank u sir for leaving such type of informative article in ur blog.
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29/05/2010 at 22:30
amitpatel745.wordpress.com’s done it once more. Incredible read!
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