Application of X-ray fluorescence spectrometry for screening pharmaceutical products for Elemental Impurities according to ICH guideline Q3D

Journal Pre-proof Application of X-ray fluorescence spectrometry for screening pharmaceutical products for Elemental Impurities according to ICH guideline Q3D Benjamin Sauer (Methodology) (Validation) (Investigation)Writing – original draft) (Supervision) (Project administration), Youhong Xiao (Formal analysis) (Resources)Writing – review and editing), Michel Zoontjes (Formal analysis) (Resources)Writing – review and editing), Christian Kroll (Conceptualization) (Resources)Writing – review and editing)

PII:

S0731-7085(19)31933-8

DOI:

https://doi.org/10.1016/j.jpba.2019.113005

Reference:

PBA 113005

To appear in:

Journal of Pharmaceutical and Biomedical Analysis

Received Date:

6 August 2019

Revised Date:

18 November 2019

Accepted Date:

20 November 2019

Please cite this article as: Sauer B, Xiao Y, Zoontjes M, Kroll C, Application of X-ray fluorescence spectrometry for screening pharmaceutical products for Elemental Impurities according to ICH guideline Q3D, Journal of Pharmaceutical and Biomedical Analysis (2019), doi: https://doi.org/10.1016/j.jpba.2019.113005

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Application of X-ray fluorescence spectrometry for screening pharmaceutical products for Elemental Impurities according to ICH guideline Q3D

Benjamin Sauera,*; Youhong Xiaob; Michel Zoontjesb; Christian Krolla

a Salutas

Pharma GmbH, Otto-von-Guericke Allee 1, 39179 Barleben, Germany Panalytical B.V., Lelyweg 1, 7600 AA Almelo, The Netherlands

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b Malvern

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Graphical abstract

Highlights:       

ICH Q3D defines requirements for drug products regarding Elemental Impurities (EI) Common methods for screening of EI in drug products: ICP-MS, ICP-OES EDXRF represents alternative for screening of oral solid dosage drug products for EI Reduced sample preparation effort (no digestion step needed) A cluster approach is applied for EDXRF method validation Method validation is compliant with European Pharmacopeia Method LOQs: 2 µg/g (Cd, Pb, As, Hg), 10 µg/g (Co, V, Ni) 1

Abstract Energy-dispersive X-ray fluorescence spectrometry (EDXRF) is a suitable analytical procedure for screening drug products for Elemental Impurities (EI) according to ICH guideline Q3D. EDXRF represents a cost-efficient, robust and standard-free alternative compared to other methodologies for trace analysis, and therefore utilization of this application should be

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encouraged. This study demonstrates the capability of EDXRF for EI screening of oral solid

dosage drug products (OSD products) within a defined matrix range. Method development and

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validation focused on class 1 (Cd, Pb, As, Hg) and class 2A (Co, V, Ni) elements, as defined by ICH guideline Q3D. In order to limit validation activities, a novel cluster approach was applied,

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based on matrix properties. This included comprehensive characterization of method performance parameters for exemplary pharmaceutical matrices and demonstration of LOQ independence from matrix effects by using a set of limit samples representing typical matrix

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variations of OSD products. The methodology can be used as a limit test for class 1 and class 2A elements and is fully compliant with method validation requirements according to the

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European Pharmacopeia. The novelty of the present work is the application of EDXRF for a routine screening of OSD products for Elemental Impurities within the pharmaceutical industry beyond previously published feasibility studies for a limited number of pharmaceutical raw

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materials or products.

Abbreviations: AAS, atomic absorption spectroscopy; EDTA, Ethylendiaminetetraacetic acid; EDXRF, energydispersive X-ray fluorescence spectrometry; EI, Elemental Impurities; Ph. Eur, European Pharmacopeia; FCT, filmcoated tablet; GRT, gastro-resistant tablet; HGC, hard gelatin capsule; ICH, International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use; ICP-MS, inductively coupled plasma mass spectrometry; ICP-OES, inductively coupled plasma optical emission spectrometry; LA-ICP-MS, laser ablation

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inductively coupled plasma mass spectrometry; LOD, limit of detection; LOQ, limit of quantitation; MDD, maximum daily dose; MUT, multiunit system tablet; OSD, oral solid dosage; PDE, permitted daily exposure; Q3D, ICH guideline on Elemental Impurities; R, Pearson correlation coefficient; RSD, relative standard deviation / coefficient of variation; SST, system suitability test; TAB, tablet; USP, United States Pharmacopeia; WDXRF, wavelength-dispersive X-ray fluorescence spectrometry; XRF, X-ray fluorescence spectrometry.

* Corresponding author. E-mail address: [email protected] (B. Sauer).

1. Introduction 2

The ICH guideline Q3D on Elemental Impurities (EI) [1] came into effect in December 2017 and replaces the compendial sulfide precipitation test (Ph. Eur. monograph 2.4.8) [2] for the control of heavy metals in drug substances and excipients. For compliance with the new holistic control strategy, a risk assessment for every commercial drug product within the scope of ICH guideline Q3D must be prepared. Information for this risk assessment includes, but is not limited to: identification of potential sources for EI, evaluation of the presence of EI within the drug product by determining the observed or predicted level of the EI and comparing with the established permitted daily exposure (PDE), and implementation of control strategies, if necessary [1]. If a

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product-specific risk assessment certifies compliance of the commercial drug product with the defined PDEs, there is no obligation for any screening activities. However, the implementation

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of ongoing screening strategies should be considered in order to complement the theoretical outcome of the risk assessment approach and to verify ongoing product compliance with the stated EI limits over the full product lifecycle. An annual skip test for every product seems

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reasonable for controlling production processes as well as raw materials.

The common methods for analysis of EI in pharmaceuticals are ICP-MS or ICP-OES, as

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reported by numerous publications [3–5]. These methods offer sensitivity, selectivity and precision, but they are also known to be complex, time-consuming and expensive, especially

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with regard to running costs and complicated sample preparation procedures [6]. Moreover, in the case of presence of poorly-soluble excipients like SiO2 or TiO2, toxic HF has to be added for vessel digestion [7]. For some companies, the usage of HF on a routine basis represents a

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knock-out criterion for the method with regard to safety issues. A recent contribution focused on laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) which is reported to serve as an alternative for screening pharmaceuticals for EI [8]. The key advantage is a direct measurement of prepared sample pellets without any previous digestion steps, compared to conventional ICP techniques. However, the study does not disclose the applicability of the method for different types of pharmaceutical formulation. The influence of typical complications

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on method performance (e.g. coatings causing increased heterogeneity of sample pellets) were not addressed.

X-ray fluorescence spectrometry (XRF) represents a suitable analytical procedure for the screening of EI in drug products in compliance with compendial standards and is simple and economic compared to other common methodologies. Especially notable is the superiority of XRF due to low sample preparation effort, non-destructive measurement, lack of need for consumables, as well as ease-of-use for untrained individuals [6]. In addition, it should be 3

highlighted that XRF calibrations have the advantage of being stable for long periods of time before requiring recalibration, in contrast to other elemental analysis techniques [9]. Several studies have focused on the application of XRF to the analysis of pharmaceutical materials. Wavelength-dispersive X-ray fluorescence spectrometry (WDXRF) was found to be a suitable tool for the analysis of EI in pharmaceuticals [10–12]. However, energy-dispersive X-ray fluorescence spectrometry (EDXRF) seems preferable for analyzing pharmaceuticals for EI. Firstly, XRF spectra can be obtained by the simultaneous measurement of all target elements or subgroups (EDXRF) compared to a sequentially measurement (WDXRF). Secondly, driven by

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different optical pathways, EDXRF requires significantly lower X-ray intensities compared to WDXRF. This results in less sample stress and fewer complications with respect to volatile and are therefore more expensive than EDXRF devices [13].

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elements. Finally, WDXRF devices are more complex due to the required optical mechanics,

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A feasibility study conducted by Arzhantsev et al. reported that handheld EDRXF devices combined with wavelet transforming filters might be a suitable tool for rapid limit tests for elemental impurities in pharmaceutical materials. The study is limited to the elements As, Pb,

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Hg and Cr, and the reported method LOQs are not compliant with ICH Q3D requirements [14]. A recent study published by Furukawa et al. [15] showed that EDXRF is capable of measuring

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EI at different concentration levels in a cellulose matrix while meeting the USP <735> [16] method validation requirements. Subsequently, this approach was extended by Davis and Furukawa, focusing on the screening of pharmaceutical excipients for 12 elements [9]. It was

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reported that the method is a suitable screening tool for 12 elements, where the maximum daily dose is 1 gram per day. Furthermore, the element V was excluded from the validation for samples containing TiO2, despite the fact that class 2A elements like V are required to be assessed, according ICH guideline Q3D. This limits the reported method in practice. For example, it would only be applicable to one-third of the local portfolio of Salutas Pharma GmbH, and would not therefore be an applicable screening tool. Additionally, the study does not

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address typical complications such as sample heterogeneity or the presence of other interfering matrix elements.

In order to extend previous studies on EDXRF, this study focused on the development of a new method approach for the screening of EI in oral solid dosage drug products (OSD products) manufactured and marketed by Salutas Pharma GmbH with respect to Ph. Eur. and USP requirements. Validation of method performance was conducted by the measurement and

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evaluation of a representative sample set covering a portfolio of more than 400 different commercial OSD products.

2. Materials and Methods 2.1. Method development approach The method scope for utilization of EDXRF for EI screening of a wide range of OSD products is set as standard-free, semi-quantitative evaluation of class 1 and 2A elements (limit test). ICH guideline Q3D defines the PDE default values for OSD products. Conversion of PDEs into

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concentration limits requires definition of the maximum daily dose (MDD). With reference to the portfolio of Salutas Pharma GmbH, we have assumed a MDD of 2.5 g for the majority of OSD

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products, resulting in the concentration limits given in Table 1. In general, a method should be able to discriminate between EI concentrations above or below the defined concentration limits

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for verifying product compliance with ICH guideline Q3D. For further consideration and simplification, option 2A concentration limits are subsumed in class-specific specification limits,

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which are defined as corresponding to method LOQs (Table 1).

The objective of this study was to evaluate matrix influences on EI X-ray fluorescence responses and to develop appropriate element-specific corrections. In order to decide whether

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EDXRF could be applied to the full local product portfolio of Salutas Pharma GmbH (>400 different OSD products), a cluster validation approach was performed, based on matrix properties. 15 different OSD products were selected as representative of the typical elemental

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composition profiles of pharmaceutical matrices (see Table 2). The samples used were classified into two different types; setup samples and limit samples. Two setup sample sets, spiked with the elements of interest ranging from 1 µg/g to 20 µg/g, were used for method setup and the evaluation of method performance parameters. One sample set was based on a cellulose matrix, while the other was representative of a typical OSD product (Metoprolol

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succinate MUT, No. 7; see Table 2). Metoprolol succinate MUT was considered a typical OSD product because it encounters common complications with XRF method development: multiple coatings lead to increased sample heterogeneity and Ti content affects the assessment of V, due to line overlap. TiO2 is a common white pigment excipient used as a coating additive for pharmaceutical products. The detailed composition of Metoprolol succinate MUT is given in Table S1 (supplementary data) and the elemental composition is disclosed in Table 2. The limit samples were based on the 15 selected OSD products, spiked at concentration levels of 2 µg/g

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for class 1 elements and 10 µg/g for class 2A elements. The limit samples were used for method and LOQ verification. The requirements regarding the application of EDXRF to EI screening are stated in Ph. Eur. monographs 2.2.37 and 2.4.20 (Table 3) [17,18] and USP monographs <233> and <735> [16,19]. The requirements of the compendial references essentially correspond to each other. This study focuses on the content and structure of Ph. Eur. monographs, because the OSD products concerned are marketed solely in non-US countries. Ph. Eur. Chapter 2.2.37 issues operational qualification and performance qualification guidance, while Chapter 2.4.20 defines

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the method validation requirements. The criteria listed in Table 3 were applied as necessary, depending on the measured sample type. In addition, validation curve parameters were

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evaluated for the setup samples (R, y-intercept, LODs and LOQs), in order to provide a holistic view on method performance.

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2.2. Preparation of sample sets

Detailed information about the commercial drug products used is given in Table 2. For sample

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preparation, the tablets were initially crushed using an agate mortar and a Tube Mill control (IKA GmbH & CO. KG). Homogeneity, especially for coated tablets, is essential for sample quality.

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Limit samples were prepared according to the described procedure below. Preparation of setup samples required the adoption of added standard volume and powder dilution steps as appropriate. A fraction of ground material (7.5 g) was spiked with a defined volume (2.0 mL) of

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customized elemental reference standard (Bernd Kraft) containing the elements of interests at a concentration of 100 µg/mL in diluted nitric acid. After drying to a constant weight in an oven at 50°C, the spiked ground material was homogenized in an agate mortar and the final concentration achieved via powder dilution (final mass of 20 g for 10 µg/g samples), using a Tube Mill control. The concentration level of 2 µg/g was achieved in a similar manner by the homogenization of spiked powder (3 g) and crude ground material (12 g). Finally, the spiked

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powder (5 g) was compacted by applying a pressure of 6 tons (hydraulic press) to form a disc shape with a 32 mm diameter. Measurement of the compacted sample pellets was related to a significant improvement in method performance compared to that from spiked powder, as previously reported [20]. The spiking procedure was verified by ICP-MS reference analysis conducted at an external laboratory. Recovery rates and RSDs met the defined validation criteria for the spiked elements, except for Hg (see supplementary data, Table S4). Complications during the analysis of Hg trace amounts caused by its volatile behavior are wellknown and discussed in section 3.1. 6

2.3. EDXRF analysis Measurements were carried out on a Malvern Panalytical Epsilon 4, benchtop EDXRF spectrometer, equipped with a 15 W, 50 kV silver anode X-ray tube, 6 primary beam filters, a helium purge facility, a high-resolution Silicon Drift Detector, a sample spinner and a 10-position removable sample changer. For the elements of interest, 4 measurement conditions were applied (see Table 4 for details). The evaluation of elemental concentrations was conducted using element-specific XRF lines: Ka line was used for Cd, As, Co and Ni; Lb1 line was used for Pb; La line was used for Hg and for V Ka (samples with Ti <0.1%) or Kb (samples with Ti

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>0.1%) lines were used. In addition to the 7 elements above, 7 majors present in the selection of OSD products were simultaneously analyzed: condition 3 was used to analyze Fe, and

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condition 4 was used for P, S, Cl, K, Ca & Ti. The default deconvolution of the operating

software was used to resolve the spectra and determine the intensity per element. For Cd Ka,

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Pb Lb1 and V Kb only, a region of interest was applied. To correct for matrix effects, different correction models were validated (fundamental parameters, alphas or ratios), and the most appropriate model was selected for each element. To obtain linear correlations, the matrix effect

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was corrected with ratios (Cd, Hg, Pb, As, Co, Ni) and alphas (V and majors). For ratios, the net element intensity was corrected with respect to the background intensity because both were

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inversely proportional to the mass attenuation coefficient of the sample. In a few cases, line overlap correction was applied; for example, Fe and Ti on Co and V.

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3. Results and Discussion

3.1. Evaluation of setup samples To validate the method setup, the two different setup sample sets were used. For each set, 6 concentrations of sample pellets were prepared in triplicate and both sides of the pellets were measured. The 6 individual values obtained per concentration level were plotted and subjected

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to linear regression analysis. The validation curve parameters are summarized in Table 5. For both sample sets, a strong linear correlation was found for all elements (R ≥ 0.990) except for V in Metoprolol succinate samples (0.98). There are multiple explanations for the lower R value for V. Firstly, the less linear correlation for V compared to other elements was caused by the presence of Ti with a calculated concentration of approximately 0.71%. As shown in Figure 1, the Ti-Kb line overlaps the V-Ka line and consequently, high Ti concentrations have a strong impact on V-Ka line intensities. In order to avoid this, for samples containing a relatively high amount of Ti an alternative line intensity (V-Kb) is used to determine V concentrations. 7

However, the V-Kb line shows only a fraction of intensity compared to the V-Ka line, and this has an adverse effect on method performance parameters for the defined concentration range. Secondly, the energy of V-Ka or -Kb photons was the lowest compared to the other elements of interest. The penetration depth of X-ray fluorescence spectrometry is a function of the matrix composition and X-ray fluorescence photon energy. The penetration depth for the elements of interest within a predefined matrix composition is shown in Figure 2. For V, photons originate from a small penetration depth (less than 1 mm), therefore derived information about V was representative of only a sample surface layer. For Cd, however, the penetration depth is greater

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than the sample thickness, so the information for Cd was collected from the whole sample volume and is less sensitive to sample heterogeneity. Sample pellets derived from coated

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tablets such as Metoprolol succinate 142.5 mg MUT showed a lower homogeneity than pellets derived from uncoated tablets. Typical coating ingredients like polymers lead to elastic behavior

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of coating fragments during the homogenization process and therefore induce larger particle sizes compared to tablet matrix components. This process leads to increased heterogeneity of the sample pellets derived from coated tablets, which had a significant influence on the

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measured V intensities. This effect for V was intensified in the presence of Ti. Since Ti is embedded in coating particles, their heterogeneous distribution caused variations of the Ti X-ray

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fluorescence intensities between individual samples. The inter-element effect between Ti and V was stronger, compared with the inter-element effect of Ti on other elements. Consequently, the measured V intensities were more sensitive to a varying Ti distribution, compared to other

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elements of interest.

For the estimation of LODs and LOQs, the RSD for samples spiked with 1 µg/g of class 1 and 2A elements was multiplied by 3 or 10, respectively. The calculated LODs and LOQs differed slightly between the two sample sets but were, for the majority of elements, below the defined specification limits of 2 µg/g (class 1) and 10 µg/g (class 2A), supporting the applicability of the

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method as a limit test for EI screening. The theoretical LOQ slightly exceeded the specification limit only for Cd in cellulose. However, the calculated LOD for Cd in cellulose met the requirements for a limit test with a specification limit of 2 µg/g. All calculated LOQs were confirmed by practical LOQ determination according to Ph. Eur. criteria [6], with values at or below the defined specification limits. Recovery and repeatability requirements were met for the majority of concentration levels (see supplementary data, Tables S2 and S3). A few results exceeded the defined thresholds, but in each case at a concentration level below the defined specification limit and therefore, method 8

validation was not at risk. It was noticeable that Hg could not be assessed in Metoprolol succinate samples due to its volatile behavior. Experiments on Hg stability revealed a strong dependency on matrix composition. If the matrix facilitated the reduction of added Hg(II) species, the concentration was seen to decrease as function of time, while matrix-mediated stabilization of Hg (II) species negated this effect. Currently, examination of the exact redox mechanism, as well as prediction of Hg stability in samples, is not possible due to matrix complexity. However, this hypothesis is strongly supported by Hg stabilization experiments. According to Louie et al., Hg stabilization can be achieved by adding chloride ions to sample

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solutions for ICP-MS analysis [21], though another contribution on this topic reported divergent results [22]. The approach of chloride ion-mediated Hg stabilization appears to also be

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ineffective for EDRXF samples, as mentioned by Shibata et al. [23] and observed by internal experiments. It was found that Hg stability could be improved by adding an organic sulfide donor to form Hg sulfide precipitates. Daily measurement of monitor samples stabilized by a

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sulphenamide, which was generated in situ from Esomeprazole magnesium, showed constant levels of class 1 and class 2A elements including Hg over a few months. In contrast, EDTA-

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mediated stabilization of Hg(II) led to an increased loss of Hg X-ray intensities. A possible reason for this is the acceleration of photocatalytic conversion of chelated Hg(II) species into elementary Hg and consequently volatilization of the element, as reported earlier [24]. The

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mentioned contribution furthermore described the heterogeneous photocatalysis of Hg(II) over TiO2, which is comparable to the chemical system present in Metoprolol succinate samples.

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3.2. Evaluation of limit samples

For the full method validation, including demonstration of LOQ independence from matrix effects, a limit sample set based on 15 different OSD products was used. This selection was representative of the local Salutas Pharma GmbH portfolio, covering dosage form subgroups including coated and uncoated tablets, multi-unit tables, multi-layer tablets, capsules etc., and

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considering diverse physical properties, different types of coatings, excipient blends and production processes. Details of the elemental composition of each individual product are summarized in Table 2, although information about light elements is excluded because their influence on the elements of interests is strongly limited and therefore, specific corrections are not intended. The elemental composition range shows that the matrices of different products varied over a wide range (see Table 2, No. 16). The matrix had a strong influence on the measured intensities of the elements of interest. Therefore, to obtain accurate results, the matrix effect must be corrected (see section 2.3). 9

For each OSD product, spiked samples were prepared at concentrations of 2 µg/g and 10 µg/g in triplicate, except for products 1, 2 and 8, which were prepared in duplicate due to sample availability. The concentrations were chosen according to the defined specification limits as discussed in section 2.1. In order to compensate for possible sample heterogeneity, both sides of each limit sample were measured and the calculated mean was used for assessment of recovery and repeatability. The LOQ validation criteria according to Ph. Eur. were met for every product, as shown in the recovery and repeatability plots (Figure 3): All recovery rates were within 70% -150% of the expected values, and the RSDs did not exceed 20%. Thus, following

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this method, element-specific correction algorithms operated reliably and products within the defined matrix range (see Table 2, No. 16) can be screened for EI using the EDXRF limit test in

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compliance with the method validation requirements.

4. Conclusions

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This study demonstrates the capability of EDXRF with regard to EI screening on oral solid dosage drug products (OSD products) within a defined matrix range. The developed method

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can be used as a limit test for class 1 and class 2A elements at the defined specification limits of 2 µg/g and 10µg/g, and is fully compliant with Ph. Eur. method validation requirements. With regard to the local portfolio handled at Salutas Pharma GmbH (>400 different OSD products), a

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cluster validation approach is applied based on matrix properties in order to define the limits of the method. Method onboarding of new products can be conducted with minimal effort if the

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product meets the defined matrix range.

As initially theorized, EDXRF represents an economic alternative for EI screening within the pharmaceutical industry. Measurement of all blank samples (see Table 2) showed values below 2 µg/g for class 1 elements and below 10 µg/g for class 2A elements and consequently, ICH guideline Q3D compliance was confirmed. Nevertheless, two important limitations of the reported approach must not be forgotten. Firstly, the lowest possible quantitation limits are fixed

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within the range of 1 µg/g -10 µg/g for the elements of interest due to methodology limitations, and secondly, the results may only be evaluated as below or above the defined limit, without specifying values. In the case of results exceeding the specification limits, this should be confirmed using a suitable reference analytic, e.g. ICP-MS or ICP-OES. Of course, quantitative method validation for EDXRF is possible, as shown by evaluation of the setup sample sets, which might also serve as a suitable reference analytic. However, for establishment of a quantitative method based on the proposed cluster validation approach, further investigations are necessary. 10

Author statement Benjamin Sauer: Methodology, Validation, Investigation, Writing – Original Draft, Supervision, Project administration. Youhong Xiao: Formal analysis, Resources, Writing – Review and Editing. Michel Zoontjes: Formal analysis, Resources, Writing – Review and Editing. Christian Kroll: Conceptualization, Resources, Writing – Review and Editing.

Funding sources

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This research did not receive any specific grant from funding agencies in the public,

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commercial, or not-for-profit sectors.

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Declaration of interests

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

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The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:

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This work was supported by Malvern Panalytical. Special thanks go to Anh Minh Huynh and

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Lisa Newey-Keane for reviewing the paper draft for content and wording.

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References International Council for Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use, Guideline for Elemental Impurities Q3D(R1), 2019.

[2]

20408 (07/2010), Eur. Pharmacop. 9.0. (2010).

[3]

G. Li, D. Schoneker, K.L. Ulman, J.J. Sturm, L.M. Thackery, J.F. Kauffman, Elemental impurities in pharmaceutical excipients, J. Pharm. Sci. 104 (2015) 4197–4206. https://doi.org/10.1002/jps.24650.

[4]

Aaron Hineman; Ken Neubauer, Meeting the USP <232> and <233> Guidelines with ICPOES, Spectrosc. (Santa Monica). 33 (2018) 8–15.

[5]

Aaron Hineman, Determination of Elemental Impurities in Antacids by ICP-MS According to the Validation Protocols Defined in USP Chapters <232> and <233> and ICH Q3D Step 4 Guidelines, Spectrosc. (Santa Monica). 32 (2017) 36–40.

[6]

By Spectroscopy Editors, Trends in X-Ray Techniques, Spectrosc. (Santa Monica). 32 (2017) 25–35.

[7]

Reynhardt Klopper, Microwave Digestion for Elemental Impurities Analysis According to ICH and USP Guidelines, Spectrosc. (Santa Monica). 32 (2017) 44–49.

[8]

T. Pluháček, M. Ručka, V. Maier, A direct LA-ICP-MS screening of elemental impurities in pharmaceutical products in compliance with USP and ICH-Q3D, Anal. Chim. Acta. 1078 (2019) 1–7. https://doi.org/10.1016/j.aca.2019.06.004.

[9]

D. Davis, H. Furukawa, Using XRF as an alternative technique to plasma spectrochemistry for the new USP and ICH directives on elemental impurities in pharmaceutical materials, Spectrosc. (Santa Monica). 32 (2017) 12–17.

[10]

E. Marguí, C. Fontàs, A. Buendía, M. Hidalgo, I. Queralt, Determination of metal residues in active pharmaceutical ingredients according to European current legislation by using Xray fluorescence spectrometry, J. Anal. At. Spectrom. 24 (2009) 1253–1257. https://doi.org/10.1039/b904064a.

[11]

A. Figueiredo, T. Fernandes, I.M. Costa, L. Gonçalves, J. Brito, Feasibility of wavelength dispersive X-ray fluorescence spectrometry for the determination of metal impurities in pharmaceutical products and dietary supplements in view of regulatory guidelines, J. Pharm. Biomed. Anal. 122 (2016) 52–58. https://doi.org/10.1016/j.jpba.2016.01.028.

[12]

P. Kikongi, C. Fauteux-Lefebvre, J. Salvas, R. Gosselin, Detecting trace levels of heavy metals in pharmaceutical raw materials with wavelength-dispersive X-ray fluorescence spectroscopy and curve-fitting regression, Spectrochim. Acta - Part B At. Spectrosc. 147 (2018) 59–70. https://doi.org/10.1016/j.sab.2018.05.011.

Jo

ur na

lP

re

-p

ro

of

[1]

[13]

M. Haschke, J. Flock, Röntgenfluoreszenzanalyse in der Laborpraxis, 1. Auflage, WILEYVCH, 2017.

[14]

S. Arzhantsev, X. Li, J.F. Kauffman, Rapid limit tests for metal impurities in pharmaceutical materials by X-ray fluorescence spectroscopy using wavelet transform filtering, Anal. Chem. 83 (2011) 1061–1068. https://doi.org/10.1021/ac1028598.

[15]

H. Furukawa, N. Ichimaru, K. Suzuki, M. Nishino, J. Broughton, J. Leinders, H. Ochi, The comparative verification of calibration curve and background fundamental parameter 12

methods for impurity analysis in drug materials, X-Ray Spectrom. 46 (2017) 382–387. https://doi.org/10.1002/xrs.2788. USP <735>, United States Pharmacop. 2018. (2018).

[17]

20237 (01/2018), Eur. Pharmacop. 10.0. (2018).

[18]

20420 (07/2018), Eur. Pharmacop. 10.0. (2018).

[19]

USP <233>, United States Pharmacop. 2018. (2018).

[20]

M. Schmeling, R.E. Van Grieken, Handbook of X-Ray Spectrometry, 2nd Editio, Marcel Dekker AG, 2002.

[21]

H. Louie, C. Wong, Y.J. Huang, S. Fredrickson, A study of techniques for the preservation of mercury and other trace elements in water for analysis by inductively coupled plasma mass spectrometry (ICP-MS), Anal. Methods. 4 (2012) 522–529. https://doi.org/10.1039/c2ay05182f.

[22]

C.D.B. Amaral, L.L. Fialho, F.P.R. Camargo, C. Pirola, J.A. Nóbrega, Investigation of analyte losses using microwave-assisted sample digestion and closed vessels with venting, Talanta. 160 (2016) 354–359. https://doi.org/10.1016/j.talanta.2016.07.041.

[23]

Y. Shibata, J. Suyama, M. Kitano, T. Nakamura, X-ray fluorescence analysis of Cr, As, Se, Cd, Hg, and Pb in soil using pressed powder pellet and loose powder methods, XRay Spectrom. 38 (2009) 410–416. https://doi.org/10.1002/xrs.1195.

[24]

G. Custo, M.I. Litter, D. Rodríguez, C. Vázquez, Total reflection X-ray fluorescence trace mercury determination by trapping complexation: Application in advanced oxidation technologies, Spectrochim. Acta - Part B At. Spectrosc. 61 (2006) 1119–1123. https://doi.org/10.1016/j.sab.2006.05.012.

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Fig. 1. Spectra obtained for samples containing 10 µg/g V. Spectrum B is an enlarged display of the red highlighted area of spectrum A. The green color represents a sample containing ~0.7% Ti, while the yellow color represents a sample without Ti. The location of relevant elementspecific X-ray fluorescence lines is indicated.

B

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A

Relative intensity

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Fig. 2. Relative intensity as function of sample thickness for class 1 and class 2A elements. For the theoretical evaluation, an average matrix composition is assumed based on the OSD products used. The thickness of the analyzed sample layer (d) can be estimated for the elements of interest as follows: d(V) ~0.5 mm, d(Co) ~1.1 mm, d(Ni) ~1.3 mm, d(Hg) ~3.5 mm, d(As, Pb) ~4 mm, d(Cd) ~25 mm.

Sample thickness (mm)

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Fig. 3. Recovery and RSD plots for product-specific LOQ validation: Recovery plot for class 1 (A) and class 2A elements (B), RSD plot for class 1 (C) and class 2A elements (D), red line indicates thresholds for method validation. B

C

D

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Table 1. PDEs, concentration limits and specification limits / method LOQs for class 1 and 2A elements. Class

Element

PDE in µg/d

Concentration

Concentration limits

Defined specification

for OSD

limits in µg/g by

in µg/g by option 2A

limits / method LOQs

products

option 1

(MDD: 2,5 g/d)

in µg/g

(MDD: 10 g/d) 0,5

2

Pb

5

0,5

2

As

15

1,5

6

Hg

30

3

12

Co

50

5

20

V

100

10

40

Ni

200

20

80

2

10

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Cd

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Table 2. Elemental composition in %a (elements of atomic number 11 upwards) for 15 limit samples and the matrix range (No. 16). Molecule and Na Mg Si P S Cl K Ca K Ti Dosage Form 1 Carbamazepine 0.34 0.04 0.33 200 mg TAB 2 Trimipramine 0.47 0.04 0.47 50 mg TAB 3 Acetylsalicylic acid 0.30 100 mg TAB 4 Aciclovir 0.33 0.04 400 mg TAB 5 Doxazosin 0.10 0.02 0.05 0.25 8 mg TAB 6 Metoprolol tartrate 0.06 1.78 1.80 2.33 100 mg TAB 7 Metoprolol succinate 1.09 1.63 0.71 142,5 mg MUT 8 Metoprolol succinate 1.08 1.63 0.73 95 mg MUT 9 Omeprazole 0.57 0.68 0.47 0.56 20 mg MUT 10 Enalapril 1.64 0.72 1.05 40 mg TAB 11 Atorvastatin 4.85 0.06 0.22 0.33 0.74 30 mg FCT 12 Diclofenac 2.00 0.44 0.83 3.30 5,11 4.27 0.09 50 mg GRT 13 Opipramol 0.04 0.25 6,25 1.09 100 mg FCT 14 Repaglinide 0.04 0.73 7.21 0,68 9.33 0.68 4 mg TAB 15 Fluconazol 0.01 0.04 0.05 0.01 200mg HGC 16 4.85 1.09 1.78 7.21 0.47 6.25 0.68 9.33 0.68 1.09 Matrix range aNote. Elemental composition was calculated based on raw material composition of the corresponding OSD product.

Fe

0.03 0.05 0.16

0.28 0.45 0.77

0.77

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No.

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Table 3. Requirements and acceptance values according to Ph. Eur. 2.2.37 and Ph. Eur. 2.4.20. Item

Methodology

Acceptance

Testing scope

Assessment by

criteria SST

this study

Measurement of reference

80 – 120%

Limit Test /

No: Currently out

material containing the

(recovery)

Quantitative Method

of scope

not defined

Limit Test /

No: Currently out

Quantitative Method

of scope

element of interest within the used concentration range Performance

Measurement of reference

Qualification

material in appropriate

detector resolution, energy and intensity Specificity

Demonstrated by complying

Refer to accuracy

Limit Test /

Quantitative Method

Yes: Setup

samples were

ro

with accuracy

of

intervals with regard to

used for

Range

Demonstrated by complying

-p

assessment

Refer to recovery

Accuracy

Demonstrated by complying

Refer to recovery

lP

with recovery or by using

re

with recovery

Quantitative Method

samples were used for assessment

Limit Test /

Yes: Setup

Quantitative Method

samples were

certified reference material

used for assessment

Measurement of spiked

70 – 150%

Limit Test /

Yes: Setup

samples consisting of a

(recovery of

Quantitative Method

samples were

ur na

Recovery

Yes: Setup

suitable matrix with known

mean)

used for

quantity of reference

assessment

standard (3 concentration levels in the range of 50150% of the intended specification limit), in

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triplicate

Repeatability

Measurement of 3

≤20% (RSD)

Quantitative Method

Yes: Setup

concentration levels prepared

samples were

in triplicate

used for assessment

Intermediate

Replicate determinations on

Precision

one sample spiked with

≤25% (RSD)

Quantitative Method

No: Currently out of scope

appropriate reference material, change of day,

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equipment and/or operator (n ≥ 12, two operators with 6 determinations each on two different days using two different apparatus) Limit of

Use the results from the

70 – 150%

quantitation

recovery study and determine

(recovery of

were used for

the lowest concentration

mean),

assessment

meeting the acceptance

LOQ ≤

criterion.

specification limit

Limit of

Determine the lowest

LOD ≤50% of

detection

concentration giving a signal

specification limit

Limit Test

No: LOQ is used for evaluation

ro

clearly distinct from that

Yes: Limit samples

of

Quantitative Method

obtained with blank solution

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Note. SST, system suitability test

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Table 4. Measurement conditions Elements

kV

uA

Filter (thickness in µm)

medium

Measurement time (s)

1

Ni, As, Hg, Pb

50

125

Ag (100)

Air

600

2

Cd

50

300

Cu (500)

Air

900

3

Co

20

240

Al (200)

Air

180

4

V

12

950

Al (50)

Air

120

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Condition

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Table 5. Validation curve parameters for cellulose and Metoprolol succinate MUT samples Matrix

Item

Cd

Pb

As

Hg

Co

V

Ni

Cellulose

R

0,999

0,999

0,999

0,999

0,998

0,995

0,998

Metoprolol succinate MUT

0.1652

-0.2464

-0.1043

-0.2389

0.0742

0.0497

-0.2078

LOD in

µg/gb

0.7

0.2

0.2

0.3

0.6

1.0

0.4

LOQ in

µg/gc

2.3

0.8

0.5

1.0

1.9

3.2

1.2

LOQ in

µg/gd

2

1

1

1

2

2

1

0.999

-a

0.997

0.980

0.998

0.0154

-a

-0.2051

1.8720

0.2934

0.3

-a

0.3

2.4e

0.5

1.1

-a

1.0

8.1e

1.7

1

-a

1

10

1

R

1

y-intercept LOD in

µg/gb

LOQ in

µg/gc

LOQ in

µg/gd

0.0148 0.4 1.4 1

0.999 -0.1084 0.2 0.8 1

of

y-intercept

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aNote. Hg is not stable in Metoprolol succinate MUT samples and was therefore excluded from evaluation. bNote. Calculation formula: LOD = 3*RSD (1 µg/g spiking level) cNote. Calculation formula: LOQ = 10*RSD (1 µg/g spiking level) dNote. Practical estimation: lowest concentration level meeting the recovery and precision requirements [18] eNote. Calculation is based on RSD for 2 µg/g samples.

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