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Characterisation of non-compendial reference standards for impurities: How good is good enough? Dr. Christian Zeine, Live webinar, Feb 1, 2017

Science

for a safer world

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Before we start

• In contrast to API RS (see for example Ph.Eur. Chapter

5.12.), for impurity RS not much guidance from

authorities

– ICH Q3A(R2) and Q3B(R2):

„Reference standards used in the analytical procedures for

control of impurities (Q3B: degradation products) should be

evaluated and characterised according to their intended uses.”

– Outdated document of German authority BfArM

(1996, “Randnummerndokument”*), translated:

“Impurity standards are used for purity tests and during method

development and validation of those tests. Identity must be

ensured and purity and assay must be defined.” *Erläuterungen zum Antrag auf Zulassung eines Arzneimittels beim BfArM

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Impurity reference standards

• The intended use determines the analytical effort

• Two major types of uses

– Qualitative use

• System suitability

• Peak identification

• During analytical method validation (e.g. specificity)

– Quantitative use

• Limit test

• Quantification of impurity

– With the reference standard directly at each test

– With the help of relative response factors (RRFs) [POLL]

• During analytical method validation (e.g. accuracy)

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Impurity reference standards, uses

• Impurity RS for qualitative use

– Identity must be secured

• Recommended combination of techniques:

– H-NMR

– IR

– CHN (free base resp. salt form)

– MS (from coupling with LC or GC)

– UV/VIS (from coupling with LC or GC)

plus

– Purity estimation (from LC/GC, sometimes H-NMR possible,

>85-90% should be the target, otherwise difficulties possible to interpret

H-NMR and IR appropiately)

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Impurity reference standards, uses

• Impurity RS quantitative use

– Accepted approach (in practice):

• Identity and assay to be determined

• Identity as aforementioned:

– H-NMR, IR

CHN (free base resp. salt form, relevant for quantitative use)

MS and UV/VIS (from coupling with LC or GC)

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Impurity reference standards, uses

• Impurity RS quantitative use

– Accepted approach (in practice):

• Identity and assay to be determined

• Assay per 100%-method (aka mass balance;

see also formula below):

– Water by Karl-Fischer/coulometry

– Residual solvent by H-NMR estimation, or GC/Headspace if necessary

– Subtract all absolute percentages (aka mass fractions or weight

percentages) from 100%

– Multiply then with analyte’s relative percent chromatographic purity

(LC/GC)

• Or use another, sufficiently specific assay technique (e.g. qNMR)

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Impurity reference standards, uses

Next slides: CofA, quant. impurity RS,

regularly accepted by authorites

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CofA: Impurity RS

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CofA: Impurity RS

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CofA: Impurity RS

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CofA: Impurity RS

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CofA: Impurity RS

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CofA: Impurity RS

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• CHN analysis, an underestimated tool (1)

– Extremely helpful on issues concerning free base resp. salt form

– Relevant to know in case standard is used for quantification

– „Common“ issue when user switches from one RS to another

(see also next slide)

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Points to consider during characterisation

OH2N

ClNH

O

N

O

Metoclopramide Imp. G (EP):

Metoclopramide N-Oxide

11,93 6.58 47,74 Hydrochloride [%]

13,31 7,02 53,25 specified value [%]

13,07 6,85 53,25 result [%]

N H C

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Salt form issues during

RS production

• Wanted: 1-(3-Chlorophenyl)piperazine Hydrochloride

CAS

Supplier 2

Supplier 3

Supplier 1

Supply of… Melting point Molecular mass

ClN

HN x HCl

210-214°C (lit.) 65369-76-8 M=196.68 (free base)

210°C 65369-76-8 M=233.14

189-191°C 51639-49-7 M=233.14

Dihydrochloride

Dihydrochloride

Hydrochloride

Hydrochloride

M=233.14

CAS 65369-76-8

mp=210-214°C

Dihydrochloride

M=269.60

CAS 51639-49-7

mp=189-191°C

Free base

M=196.68

CAS 6640-24-0

liquid

• Literature data:

• Order from chemical trade:

• CHN analysis, an underestimated tool (2)

– Use of corrected values helpful, here water,

residual solvent also possible

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Points to consider during characterisation

Risperidone cis-N-Oxide

C [%] H [%] N [%]

value mean (n=3) 58,80 6,99 11,55

theoretical value 62,87 6,81 12,22

difference -4,08 0,18 -0,67

correction with 6,48% water; (RES <0,05%)

C [%] H [%] N [%]

corrected value 62,87 6,76 12,29

difference 0,00 -0,05 0,07

• Look for plausibility between other available results

– Example H-NMR and HPLC, case 1

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Points to consider during characterisation

Cl

O

OH

4-Chlorobenzoic acid,

bezafibrate impurity A (EP), purity HPLC 99.3%

1H-NMR HPLC

• Look for plausibility between other available results

– Example H-NMR and HPLC, case 2

Nabumetone Imp D (EP): Imp of imp at 5.9 minutes

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Points to consider during characterisation

O

O

• Look for plausibility between other available results

– Example H-NMR and HPLC, case 2

Nabumetone Imp D (EP): No corresponding result in H-NMR

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Points to consider during characterisation

0,17% RES

Dichloromethane

organic impurities < 0,5%

TMSH

marker

Solvent

DMSO-d6

O

O

• Look for plausibility between other available results

– Example H-NMR and HPLC, case 2

– Nabumetone Imp D light sensitive

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Points to consider during characterisation

HPLC

0 h

1 h

24 h

trans cis

O

O

O O

h

• Can I use a qualitative impurity standard (research

material) for quantitative applications?

– Depending on the angle from which you look on it:

You can, but think twice!

– If purity indicated as for example „>80%“, or similar: With what

value should I calculate? [QUESTION TO PARTICIPANTS!]

• Do not calculate with that value (i.e. 80%)!

– Material probably purer than that value, risk of underestimation of

impurity

– If at all: Calculate with 100%! Risk of overestimation „only“!

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Points to consider during use

• Can I use a qualitative impurity standard (research

material) for quantitative applications?

– Risk of overestimation of imps

• Normally no regulatory issue, as patients not at risk to receive

medicines with impurities really out of specs

• Economic risk however for pharmaceutical manufacturer

– Lot of outcomes possible that would generate hidden costs!

– False positive OOS results for imps: unnecessary investigations!

– Issues during validation studies possible

– During development of FDF (consideration of ICH Q3A/B):

Risk of pushing yourself into unneccessary

and expensive qualification studies (last resort animal tox studies)

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Points to consider during use

• Can I use a qualitative impurity standard (research

material) for quantitative applications?

– The less analytical details – the higher the economic risk

• Depending on sources, qualitative standards often lacks

correct identity with regard to salt forms

• Also water and residual solvents not checked

– Especially water in hydrates can make a considerable part

of the substance on hand

• Salt form and water issues can lead to overestimation of

40% and more, i.e. assuming 100% assay when in fact 70% „as is“

– Even when chromatographic purity is quite high

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Points to consider during use

• For quantitative impurity standards:

Do we need a second assay method,

like for primary API RSs?

– We see these requests sometimes from clients

– Mainly due to requests from authorities

• My personal opinion:

– Not really …

• With the 100%-method (or qNMR), risk of underestimation of

assay of impurity RS is extremely low

– And then also underestimation of imps present in medicines

=> low risk for patients if at all

• Overestimation is minimised

• In backhand with our imp RS: carbon titration from CHN analysis

• Happy to discuss further … please send me an email!

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Quantitative use:

How good is good enough?

Closing remarks

• LGC Standards is part of LGC group

• Science & Innovation section of LGC acts as NMI for

chemical and biochemical measurement in the UK

(comparable to NIST in the US)

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Closing remarks

• Manufacturing of pharmaceutical reference materials

– For impurities, APIs and excipients approx. 4,300 standards

– Constantly new developments (e.g. primary standards)

• Brochure of almost 500 impurity standards available with

reference to the USP description, in most cases less

expensive price-per-mg compared to USP, plus the CofA!

– ISO 34 and ISO 17025 accredited

– Customised services

• Production of solvents

– For HPLC applications

in pharma industry

– Extremely pure for residue analysis

• Distribution

– Pharmacopoeial reference standards, phytochemicals

– CRMs/RMs from LGC, IRMM, NMIA, NIST etc. for all purposes 27

Service modules

Supplementary processes for stability monitoring and re-testing

Process steps based on internal quality standards; ISO 17025 or ISO Guide 34

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Sourcing

2

Quality Control

3

RAW-material

4

Packaging

5

Characte-risation

6

Certifi-cation

7

Storage

8

Distribution

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Services for two pharmaceutical

World Top 10 companies

1

Sourcing

2

Quality Control

3

RAW-material

4

Packaging

5

Characte-risation

6

Certifi-cation

7

Storage

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Distribution

1

Sourcing

2

Quality Control

3

RAW-material

4

Packaging

5

Characte-risation

6

Certifi-cation

7

Storage

8

Distribution

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Services over the whole chain

1

Sourcing

2

Quality Control

3

RAW-material

4

Packaging

5

Characte-risation

6

Certifi-cation

7

Storage

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Distribution

• For several top generic / ethical companies

• Depending on the extent of the service, price per unit can

go down to less than 30 EURO

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Stability Monitoring +

QC Batch

Monitoring +

• Main topics of seminar at Day One:

– Different kinds of reference standards

and their intended application areas

– How to handle the details presented in a

certificate of analysis that help you choose

the right reference standard for

your specific purpose

– Presented by experts from EDQM, Teva, LPU and LGC

• Day Two:

– Visit our production site in Luckenwalde

– Manufacture of impurity and

primary reference standards

– Warehouse and dispensing facilities

• You will receive further information with tomorrow‘s

follow up email! 31

Join us April 6-7, 2017 in Potsdam!

http://bit.ly/2kmnDoH

„Bridge of Spies“

Source: Wikipedia

• Most of these slides were originally shown at the

International Reference Standard Symposium at USP‘s

headquarter on Nov 3, 2016:

– Thanks to the IRSS organisation team for the opportunity to

speak there last year as a representative from LGC

• Thanks to my colleagues Dr. Andreas Sieg and

Dr. Peter Weber for the analytical slides

– Join us for the seminar in April to see how we produce our

reference standards!

• And thanks of course to you as the audience today!

– Please take the short survey after leaving the webinar!

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Thank you!

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QUESTIONS?

• Of course also per email to

christian.zeine@lgcgroup.com

© Dr Christian Zeine, 2017, LGC. All rights reserved.

LGC Ltd., Queens Road, Teddington, Middlesex, TW11 0LY, UK