Simultaneous Estimation of Fenofibric Acid Tablets' Elemental Impurities using Inductively Coupled Plasma Mass Spectrometry (ICP-MS)

 

Amitkumar J. Vyas1, Nensi D. Santoki1*, Dhruvi U. Parmar1, Ashok B. Patel2, Ajay I. Patel1, Ashvin V Dudhrejia1, S. R. Shah2, Devang B. Sheth3

1B.K. Mody Government Pharmacy College, Polytechnic Campus,

Near Aji Dam, Rajkot, Gujarat, India, Postal Code: 360003.

2Government Pharmacy College, Gandhinagar, Gujarat, India. Postal code: 382027.

3L.M. College of Pharmacy, Ahmedabad, Gujarat, India. Postal code: 380009.

*Corresponding Author E-mail: nensipatel1702@gmail.com

 

ABSTRACT:

Control of elemental impurities in medications and pharmaceuticals, as outlined in USP <232> and ICH Q3D, is a mandatory prerequisite for regulatory approval. This study introduces a microwave-assisted sample preparation method for Fenofibric Acid Tablets using diluted nitric acid. Through addition and recovery experiments conforming to oral permissible daily exposure values for Class 1 (As, Cd, Hg, and Pb) and Class 2A (Co, V, and Ni) elements, each sample was spiked with element concentrations of 2.5J and 1.5J to assess recoveries in accordance with USP <233> requirements. Our findings demonstrate the efficacy of a matrix that addresses low spike recovery issues, enabling the simultaneous determination of Class 1 and Class 2A elements in a single analysis. The analytical procedure undergoes validation for Specificity, Limit of Detection, Limit of Quantitation, Linearity, Precision (System Precision and Method Precision), Intermediate Precision, Accuracy, and System Suitability. This validated analytical method is suitable for detecting elemental impurities in Fenofibric Acid Tablets, supporting their regulatory submission in various regulated markets.

 

KEYWORDS: Fenofibric Acid Tablets, ICP-MS, Elemental Impurities, Microwave Assisted Digestion, Method Validation.

 

 

 

INTRODUCTION:

Control of Elemental Impurities in Drugs and Pharmaceuticals, mandated by USP <232> and ICH Q3D since January 2018, is a crucial requirement for regulatory submission. Regulatory bodies and official pharmacopoeias increasingly demand more precise and accurate quantitative determination of elemental impurities in pharmaceuticals due to their potential health risks and effects on drug stability and efficacy.4-6,8

 

USP has established permitted daily exposures (PDEs) for elemental impurities, measured in mg/day, based on the route of administration (oral, parenteral, inhalation), in alignment with ICH Q3D standards. The presence of impurities significantly impacts the stability and pharmacological effectiveness of pharmaceutical active ingredients (APIs) and drug products.4

 

EXPERIMENTAL:

Chemical and Laboratory Reagents:

Concentrated nitric acid (70%) was acquired from J.T. Baker, while concentrated hydrochloric acid (35%) was obtained from Fisher Scientific. All of these reagents were of trace metal grade.

 

Diluted nitric acid was utilized for preparing analytical solutions and sample dilutions. Deionized water with a resistance of 18 MΩ-cm was generated using a Milli-Q water purification system from Millipore. Lead Standard (1000µg/mL), Arsenic Standard (1000µg/mL), Cadmium Standard (1000µg/mL), Mercury Standard (1000 µg/mL), Cobalt Standard (1000µg/mL), Vanadium Standard (1000µg/mL), Nickel Standard (1000µg/mL), Gold Standard (1000µg/mL), Scandium Standard (1000 µg/mL), Germanium Standard (1000µg/mL), Rhodium Standard (1000µg/mL), and Bismuth Standard (1000 µg/mL) of ICP-MS grade were procured from Inorganic Ventures.

 

Fenofibric Acid Tablets were provided by Amneal Pharmaceutical Pvt. Ltd., and all test materials were stored according to the recommended conditions specified in the supplier’s certificate of analysis. Solutions prepared from these test materials were stored at room temperature. All chemicals sourced from Amneal Pharmaceutical Pvt. Ltd. for analytical purposes were of trace analysis grade or of equivalent quality. Volumetric flasks utilized in preparations were made of polymethylpentene (PMP), polypropylene (PP), or similar high-quality polymer materials. All sample preparation procedures and measurements conducted at Amneal Pharmaceutical Pvt. Ltd. adhered to Good Manufacturing Practices (GMP).

Instrumentation:

Sample digestion was conducted using the ETHOS UP closed vessel microwave digestion unit from Milestone, Italy. Quantitative analyses were carried out using a Thermo ScientificTM iCAP™ RQ ICP-MS system equipped with a model ASX-560 Autosampler from Teledyne CETAC Technologies. Kinetic Energy Discrimination (KED) Mode, also known as Helium collision mode, was employed for all measurements, ensuring effective elimination of most common polyatomic interferences (Li G et al, 2015). Internal standards were carefully selected for each elemental analyte to minimize interferences by ensuring similarity in their first ionization energies.

 

Instrumental parameters were optimized daily before analysis to ensure system suitability. Automated adjustments to torch alignment, detector voltage, and ion lens voltages were made to optimize resolution, sensitivity, and stability across a wide range of masses.

 

RESULTS AND DISCUSSION:

Method Development:

Throughout this study, various challenges were addressed, primarily focusing on the inadequate recovery of certain elements due to their incompatibility with the analysis matrix. Both room temperature digestion and microwave-assisted digestion were explored as potential sample preparation techniques, utilizing different concentrations of acids and adjusting various parameters of the microwave digestion system 11-14. Among these approaches, digestion with nitric acid was deemed suitable due to the production of a clear solution. A summary of the conducted trials is provided in Table 2. Diluents were carefully chosen to match the matrix present in the sample solutions and to stabilize volatile mercury, as required by USP <233>6.

 

Table 1.  Selection of Solvent System and Parameters for Microwave Digestion

Selection of Solvent System

Sr No#

Sample Weight (gm)

Conc HNO3 added (mL)

Conc HF added (mL)

Conc HCl added (mL)

Dilute up to volume with diluent

Inference

1

0.12544

10

0.5

N/A

100

Clear Solution observed

Parameters for Microwave Digestion

Accessories

Maxi-44

Door locking

> 80 ºC

Control Type

Ramp to temperature

Sr. No.

Time (min)

MW (w)

T2 (ºC)

1

30

1800

180

2

30

1800

180

Cooling Time (min)

25

 

Preparation of Solutions:

Diluent Preparation:

Diluent-1:

Transfer 40mL of concentrated nitric acid into an appropriate beaker containing 500mL of water. Then, add 0.6mL of gold standard solution and dilute the mixture to 2000mL with water and mix well.

 

Diluent-2:

Transfer 40mL of concentrated nitric acid and 10mL of HCl into a suitable beaker with 500mL of water. Then, add 0.6mL of gold standard solution and dilute the mixture to 2000mL with water and mix well.

 

Rinsing Solution Preparation:

4mL of concentrated Nitric acid and 20mL of concentrated Hydrochloric acid was transferred into a suitable beaker containing 500mL of water 0.6mL of Gold standard solution (1000µg/mL) was added and diluted to 2000mL with water and mixed well.

 

Internal Standard Preparation:

Internal Standard Stock Solution:

In a 25mL volumetric flask, add 0.3mL of Indium Standard (1000mg/L), 0.1mL of Bismuth Standard (1000 mg/L), and 1.0mL of Yttrium Standard (1000µg/mL). Dilute to volume with Diluent-1 and well mix.

 

Internal Standard Solution:

Add 2.5mL of Internal Standard Stock Solution 1 and 1.5mL of Germanium Standard (1000µg/mL) to a 100 mL volumetric flask. Dilute with Diluent-2 and well mix.

 

Linearity Solution Preparation:

(Note: Use only micropipettes for Linearity solution preparation.)

 

Linearity stock solution-1:

In a 50mL volumetric flask, add 0.480mL of Vanadium standard solution (1000µg/mL), 0.240mL of Cobalt standard solution (1000µg/mL), and 0.960mL of Nickel standard solution (1000µg/mL). Dilute to volume with Diluent-1 and well mix.


Linearity stock solution-2:

In a 50mL volumetric flask, add 0.360mL of Arsenic standard solution (1000µg/mL), 0.120mL of Cadmium standard solution (1000µg/mL), 0.715mL of Mercury standard solution (1000µg/mL), and 0.120mL of Lead standard solution (1000µg/mL). Dilute to volume with Diluent-1 and thoroughly mix.

 

Linearity stock solution-3:

10.0mL of Linearity stock solution-1 and 2.0mL of Linearity stock solution-2 were combined in a 50mL volumetric flask, diluted to volume with Diluent-1, and well mixed. Table 2 depicts linearity solution preparation.

 

Table 2: Linearity solution preparation

Level

Linearity stock Solution-3 to be taken (mL)

Internal Standard Solution

to be taken

(mL)

Dilute to volume with Diluent-1 (mL)

Concentration in ppb

V

Co

Ni

As

Cd

Hg

Pb

Solution A (10 %)

0.100

0.3

100

4.573

2.221

9.067

0.736

0.244

1.464

0.247

Solution B (25 %)

0.250

0.3

100

9.764

4.699

19.22

1.551

0.525

3.117

0.520

Solution C (50 %)

0.500

0.3

100

18.37

8.919

36.38

2.972

0.977

5.922

0.994

Solution D (100 %)

1.000

0.3

100

38.74

19.15

72.56

5.775

1.899

11.52

1.905

Solution E (150 %)

1.500

0.3

100

57.88

29.10

116.1

8.735

2.869

17.23

2.864

Solution F (200 %)

2.000

0.3

100

77.14

38.50

154.8

11.54

3.847

22.85

3.828

Drift

Use Solution E as drift evaluation solution

 

 

Blank Preparation:

Blank solution:

1.0mL of internal standard solution was transferred into a 50mL volumetric flask containing 50mL of diluent-1 mixed well.

 

Calibration blank:

Use blank solution as calibration blank.

 

Sample blank solution:

The digesting vessel was filled with 10.0mL of strong nitric acid and kept open. After that, 0.5mL of strong hydrofluoric acid was added, and the container was left open. The vessel was placed in a microwave digesting machine after being sealed with a cap. The software was executed with the chosen settings. Following the end of the digesting process, the vessel was removed, the solution was put into a 100mL volumetric flask, and the vessel was rinsed three times with about 10mL of diluent-2 before being placed back into the flask. The flask received 0.5mL of Internal Standard Solution added to it. Using diluent-2, the solution was diluted to the appropriate level and combined. PVDF membrane filter with a 0.45µm pore size was used to filter the mixture.

 

Sample Preparation:

A tablet crusher was used to ground the tablets. A sample weighing about 0.125 gramme was moved into the vessel. Following that, the sample blank solution's identical process was used.

 

Two replicates of samples were prepared.

 

Method Validation6,15-16

The suggested technique was verified for compliance with USP <233>, USP <730>, USP <736>, and the most recent ICH guideline in terms of Specificity, Limit of Detection and Limit of Quantitation, Linearity, Precision (System Precision and Method Precision), Intermediate Precision, Accuracy, and System Suitability.
Table 7 summarises the derived targeted limits (µg/g) and allowed daily exposure (PDE) limits (µg/day) for elemental impurities from classes 1, 2A, and 2B.

 

Specificity:

The assessment of specificity involved determining how much less of each elemental impurity was identified in the blank sample compared to the spiked sample. Table 3 presents the specificity results.

 

The sample blank's substantial interference (CPS) at each element's mass is less than the spiked sample solution's CPS for each element. It is thus shown that the approach is distinctive for each of the seven elements.

 

Linearity:

Determining out how much less of each elemental impurity was found in the blank sample than in the spiked sample was part of the specificity assessment process. The specificity results are shown in Table 3. The significant interference (CPS) of the sample blank at each element's mass is smaller than the CPS of the spiked sample solution for each element. Thus, it can be seen that each of the seven elements has a unique method.

 

For every target element, the correlation coefficient was less than 0.990. The results show that the analytical process is linear in the concentration range of 10% to 20% (0.999 ppb to 19.980 ppb) of working concentration for Vanadium, 10% to 20% (0.499 ppb to 9.980 ppb) of working concentration for Cobalt, 10% to 20% (2.002 ppb to 40.040 ppb) of working concentration for Nickel, 10% to 20% (0.149 ppb to 2.997 ppb) of working concentration for Arsenic, 10% to 20% (0.050 ppb to 1.002 ppb) of working concentration for Cadmium, 10% to 20% (0.299 ppb to 5.994 ppb) of working concentration for Mercury, and 10% to 20% (0.049 ppb to 0.998 ppb) of working concentration for Lead.

 

Precision:

System Precision:

The Standard Linearity for calibration curve is in acceptance criteria. All the acceptance Criteria described in the USP was met as the correlation coefficient is ≥ 0.990 for each target element. And the drift is ≤20%. for each target element. Thus the analytical procedure is precise with respect to system and suitable for its intended use.

 

 

Table 3. Permitted Daily Exposures and Concentration Limits for Tested Elemental Impurities and specificity

Name of Element

Permitted Daily Exposures

Specificity

Class

Oral PDE µg/Day

µg/ day

CPS of sample blank

CPS of Spiked sample solution

Cadmium (Cd)

1

5

3.253

876

409276

Lead (Pb)

1

5

1.626

113

534051

Arsenic (As)

1

15

6.505

773

508333

Mercury (Hg)

1

30

0.488

22

7726

Cobalt (Co)

2A

50

0.163

15

10032

Vanadium (V)

2A

100

0.976

556

77032

Nickel (Ni)

2A

200

0.163

5287

123529

 

Table 4: Linearity concentration

Level

Concentration in ppb

Vanadium

(V)

Cobalt

 (Co)

Nickel

(Ni)

Arsenic (As)

Cadmium (Cd)

Mercury (Hg)

Lead

(Pb)

Solution A (10 %)

4.573

2.221

9.067

0.736

0.244

1.464

0.247

Solution B (25 %)

9.764

4.699

19.22

1.551

0.525

3.117

0.520

Solution C (50 %)

18.37

8.919

36.38

2.972

0.977

5.922

0.994

Solution D (100 %)

38.74

19.15

72.56

5.775

1.899

11.52

1.905

Solution E (150 %)

57.88

29.10

116.1

8.735

2.869

17.23

2.864

Solution F (200 %)

77.14

38.50

154.8

11.54

3.847

22.85

3.828

R2

0.9997

0.9995

0.9987

0.9996

0.9996

0.9995

0.9995

Correlation coefficient (r)

0.9998

0.9997

0.9993

0.9998

0.9998

0.9997

0.9997

Slope

49638.37

119152.5

27249.36

5819.670

31371.80

39876.65

345787.0

Y-intercept

5354.253

110.7031

794.1527

510.4633

29.3203

79.9404

1795.9761

 

Figure 1: Instrument derived Linearity plot

 

Method Precision:

To evaluate the method precision, six individual samples (Spiked with all the known elemental impurities at respective specification levels) were prepared and analyzed as per the analytical procedure.

 

USP requirements for precision (repeatability) were met as the %RSD for each of the six preparations of the spiking concentration for each element was ≤20%. Thus the analytical procedure is precise with respect to method and suitable for its intended use.

 

Accuracy:

The Accuracy of the method was demonstrated by spiking known elemental impurity in to the sample solution from 50% to 150% of respective specification level for Vanadium, Cobalt, Nickel, Arsenic, Cadmium, Mercury and Lead and analyzed as per test method.

 

Mean recovery at each level and overall mean recovery of each target elements were between 70.0% and 150.0 %. Thus, the acceptance criteria described in USP Chapters <233/232> for Accuracy was met.

Table 5: Limit of Detection and Limit of Quantitation

Name of Element

LOD

(ppb)

LOD

(ppm w.r.t. to test)

LOD

(µg/day)

LOQ

(ppb)

LOQ

(ppm w.r.t. to test)

LOQ

(µg/day)

Vanadium (V)

4.198

2.099

8.001

13.120

6.560

25.006

Cobalt (Co)

2.103

1.051

4.006

6.573

3.286

12.526

Nickel (Ni)

8.380

4.190

15.972

26.187

13.093

49.910

Arsenic (As)

0.634

0.317

1.208

0.981

0.490

1.867

Cadmium (Cd)

0.209

0.104

0.396

0.656

0.328

1.250

Mercury (Hg)

1.258

0.629

2.397

3.932

1.966

7.494

Lead (Pb)

0.209

0.104

0.396

0.654

0.327

1.246

 

Limit of Detection and Limit of Quantitation:

The Limit of Detection and the Limit of Quantitation were determined based on the Standard Deviation of the Response and the Slope method.  The results of LOD and LOQ are summarized in Table 15.

 

System Suitability:

The correlation co-efficient was less than 0.990 and the Drift was NMT 20 % for each Target element. Thus the results for system suitability are well within the acceptance criteria; hence the given method is acceptable for its intended use.

 

CONCLUSION:

An ICP-MS method for the determination of elemental impurities in Fenofibric Acid Tablets has been developed using Microwave assisted sample preparation using diluted nitric acid and successfully validated for Specificity, Limit of Detection and Limit of Quantitation, Linearity, Precision (System Precision and Method Precision), Intermediate Precision, Accuracy and System Suitability according to USP <233>, USP <730>, USP <736> and current ICH guideline.

 

This analytical method can be successfully employed for routine analysis of elemental impurities in Fenofibric Acid Tablets. The analytical procedure along with validation supports the regulatory submission of Fenofibric Acid Tablets Application in different regulated markets.

 

CONFLICT OF INTEREST:

There is no conflict of intrest to expose.

 

ACKNOWLEDGEMENT:

The Authors are grateful to Amneal Pharmaceutical Pvt. Ltd., Matoda, Ahmedabad, for providing all the facilities to complete the research work and for providing Fenofibric Acid Tablets as gift samples.

 

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Received on 07.05.2024      Revised on 16.10.2024

Accepted on 09.01.2025      Published on 28.02.2025

Available online from March 04, 2025

Asian Journal of Pharmaceutical Analysis. 2025;15(1):1-6.

DOI: 10.52711/2231-5675.2025.00001

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