Methods for determining relative response factors for impurity analysis using liquid chromatography with absorbance and evaporative light scattering detection

Patent metadata

Field	Value
Publication number	US-10422775-B2
Application number	US-201715404851-A
Country	US
Kind code	B2
Filing date	Jan 12, 2017
Priority date	Jan 12, 2016
Publication date	Sep 24, 2019
Grant date	Sep 24, 2019

Abstract

Methods and systems for determining relative response factors for liquid chromatography using both molar concentration-based detection and mass concentration-based detection are described herein. A method includes determining a relative response factor for a compound based on the ratio of a molar-based peak area for the compound to the logarithm of the mass-based peak area for the compound and based on the ratio of a molar-based peak area for a reference compound divided by the logarithm of the mass-based peak area for the reference compound.

First claim

The invention claimed is:

1. A method for determining relative response factors comprising:
performing liquid chromatographic separation of a sample including a reference compound and one or more additional compounds;
performing molar concentration-based detection on the separated sample to determine a molar-based peak area for the reference compound and for each of the one or more additional compounds;
performing mass concentration-based detection on the separated sample to determine a mass-based peak area for the reference compound and for each of the one or more additional compounds; and
determining a relative response factor (RRF) for each of the one or more additional compounds based on the ratio of the molar-based peak area for the additional compound to the logarithm of the mass-based peak area for the additional compound and the ratio of the molar-based peak area for the reference compound to the logarithm of the mass-based peak area for the reference compound.

2. A method for determining relative concentrations of a reference compound and one or more additional compounds in a test sample, the method comprising:
determining relative response factors for the one or more additional compounds using the method of claim 1 ;
performing liquid chromatographic separation of the test sample;
performing molar concentration-based detection on the separated test sample to determine a molar-based peak area for the reference compound and for each of the one or more additional compounds;
applying the relative response factor for an additional compound to the molar-based peak area for the additional compound to obtain a corrected molar-based peak area for each of the one or more additional compounds in the test sample; and
determining the relative concentrations of the reference compound and the one or more additional compounds in the test sample based on the molar-based peak area of the reference compound and on the corrected molar-based peak area for each additional compound.

3. The method of claim 2 , wherein the sample used to determine the relative response factors is the same as the test sample.

4. A method for determining concentrations of a reference compound and one or more additional compounds in a test sample, the method comprising:
determining relative response factors for the one or more additional compounds using the method of claim 1 ;
performing liquid chromatographic separation of the test sample;
performing molar concentration-based detection on the separated test sample to determine a molar-based peak area for the reference compound and for each of the one or more additional compounds;
applying the relative response factor for an additional compound to the molar-based peak area for the additional compound to obtain a corrected molar-based peak area for each additional compound in the test sample;
determining the relative concentrations of the reference compound and the one or more additional compounds in the test sample based on the molar-based peak area of the reference compound and the corrected molar-based peak area for each additional compound;
performing liquid chromatographic separation of a reference sample including a known concentration of the reference compound;
performing molar concentration-based detection on the reference sample to determine a molar-based peak area for the reference compound in the reference sample; and
comparing the molar-based peak area of the reference compound in the reference sample to the molar-based peak area of reference compound in the test sample to obtain concentrations of the reference compound and the one or more additional compounds in the test sample from the determined relative concentrations of the reference compound and one or more additional compounds in the test sample.

5. A method of performing mass balance for a degraded sample including an active pharmaceutical ingredient (API) and one or more impurities, the method comprising:
determining relative response factors for the one or more impurities using the method of claim 1 with the reference compound being the API and the one or more additional compounds being the one or more impurities;
performing liquid chromatographic separation of an initial sample not subjected to degrading conditions;
performing molar concentration-based detection on the separated initial sample to determine a molar-based peak area for the API and for each of the one or more impurities in the initial sample;
applying the relative response factor for each of the one or more impurities to the molar-based peak area for the impurity to obtain a corrected molar-based peak area for each impurity in the initial sample;
performing liquid chromatographic separation of a degraded test sample, the degraded test sample being a test sample including the API that was previously subjected to degrading conditions;
performing molar concentration-based detection on the separated degraded test sample to determine a molar-based peak area for the API and for each of the one or more impurities;
applying the relative response factor for an impurity to the molar-based peak area for the impurity to obtain a corrected molar-based peak area for each of the one or more impurities in the degraded test sample; and
comparing the sum of the corrected molar-based peak areas of the one or more impurities and the molar-based peak area of the API for the degraded sample with the sum of the corrected molar-based peak areas the one or more impurities and the molar-based peak area of the API for the initial sample to obtain a percentage recovery.

6. The method of claim 1 , wherein the relative response factor for each of the one or more additional compounds (RRF add _ cpnd ) is a function of the ratio of the molar-based peak area for the additional compound (Molar_Area add _ cpnd ) to the logarithm of the mass-based peak area for the additional compound (log(Mass_Area add _ cpnd )) divided by the ratio of the molar-based peak area for the reference compound (Molar_Area add _ cpnd ) to the logarithm of the mass-based peak area for the reference compound (log(Mass_Area add _ cpnd )).

7. The method of claim 6 , wherein the relative response factor for each of the one or more additional compounds is described by the following equation:

RRF
add_cpnd

∝

Molar_Area
add_cpnd

log
⁡

(

Mass_Area
add_cpnd

)

/

Molar_Area
ref_cmpd

log
⁡

(

Mass_Area
ref_cmpd

)

.

8. The method of claim 1 , wherein the molar concentration-based detection is absorption spectroscopy in the ultraviolet-visible spectral region.

9. The method of claim 1 , wherein the mass concentration-based detection is

Assignees

• Waters Technologies Corp

Inventors

• Hong Paula
• Jones Michael D

Classifications

• G01N30/74

  Optical detectors {(measurement of intensity, velocity, spectral content, polarisation, or phase of infrared, visible or ultraviolet light G01J)} · CPC title

• G01N2030/045

  internal · CPC title

• G01N30/06 Primary

  Preparation · CPC title

• G01N2030/8872

  impurities · CPC title

• G01N30/8665 Primary

  for calibrating the measuring apparatus · CPC title