Multielemental Screening and Analytical Method Validation for Determination of Elemental Impurity in Sucroferric Oxyhydroxide by Using (ICP-MS)

A highly selective, specific, precise sensitive and reliable ICPMS method has been developed and validated by using ICP-MS for the determination of multielement in Sucroferric oxyhydroxide.


INTRODUCTION
Sucroferric oxyhydroxide is a non-calcium, ironbased phosphate binder used for the control of serum phosphorus levels in adult patients with chronic kidneydisease (CKD) on haemodialysis (HD)or peritoneal dialysis (PD) [1]. It is used in form of chewable tablets.It has a molecular formula of C12H29Fe5Na2O23 and a molecular weight of 866.5g/mol.
The USP current method, (231) "heavy metals limit test" is recognized to be insufficient and is due to be replaced with USP (232) & (233) new general chapters. On the subject of the constraint of elemental impurities like heavy metals & catalyst residue, bring into being an urgent requirement for robust and competent ICP-MS analytical method [4]. Permitted daily exposure (PDE) limits for a extensive assortment of inorganic elemental impurities defined in USP (232):

Aim
Our main aim and objective of research work is to develop and validate method to make sure efficient control of the levels of elemental impurities in the different pharmaceuticals .An approach based on assessing and controlling potential sources of elemental impurities, coupled with focused, limited testing, is preferable to exhaustive testing on the different Pharmaceuticals drugs and APIs.A scientific, risk-based approach combined with knowledge and control of the key sources of elemental impurities in the different active pharmaceutical ingredients(APIs) manufacturing processsuch as catalysts, provides an efficient and comprehensive elemental impurity control strategy for different Pharmaceuticals.
The objective contains three main aspects: 1. An evaluation of the toxicity data for potential elemental impurities. 2. The establishment of permitted daily exposure (PDE) for each element of toxicological concern. 3. Development of controls to limit the inclusion of elemental impurities in drug products to levels at or below the PDE.

METHOD
For multi-metal screening of 24 elements in pharmaceutical API .There is no single standard solution having all elements of interest, because some specific elements require specific conditions for producing stable solution.
Therefore the desired standard solution have been made by using comercially available single element standard by reference standard material.Working standard solutions were prepared by diluting individul stock standard solutions.The tuning solution used for the ICP-MS instruements contained 1μg/L Ce,Co,Li,Mg,Tl and Y.
The nonspectral matrix effects were resolved by the addition of internal standards.The internal standard stock solution was prepared by diluting single element stock solutions of Sc(1000 ppm) and Dy (1000 ppm) into 10 mL volumetric flask made of polypropylene or polymethylpentene, added 100 μL of concentrated nitric acid, than added Sc ( 100 μL ) and Dy ( 100 μL ) and dilute the volume up to mark with Milli-Q water.

ICP-MS Instrument and Equipment
The elemental impurity (heavy metal) analysis was carried out by using Agilent technologies 7700 Series (ICPMS MODEL 7700X) with Mass Hunter Workstation Software for ICP-MS with Milestone Microwave Reactor Milestone, model Ultra WAVE.
The Agilent 7700x ICP-MS provides unparalleled accuracy in high matrix samples redefining cell performance in helium mode with revolutionary 3 rd generation cell design-ORS (Octapole Reaction System), it includes a standard helium (He) mode cell gas line which provides removal of polyatomic interference. The advanced high energy helium mode (He) was used in this method. The instrument equipped with standard nickel sampling and skimmer cones and concentric nebulizer of glass, quartz spray chamber and quartz torch with 2.5 mm id injector. An agilent ASX-500 ICP-MS autosampler was used to deliver the samples.It can measure trace metals as low as one part per trillion (ppt) and have capability to quick scan more than 80 elements to determine the composition of unknown samples with MassHunter Workstation Software that automates the analysis and accurately interprets the analysed data.

Selection of Matrix Solvent
The matrix solvent composition plays very crucial role for elemental analysis .Sample digestion is mainly done by common mineral acids like nitric acid, hydrochloric acid ,perchloric acid and sulphuric acid.By using microwave assisted digestion procedures with 0.1 g of sample and simplified reagent with mixture of HNO3/ HCl in ratio of 1:3 v/v were used for quantitative determination of 27 elements(Ag,As, Au, Ba, Cd, Co, Cr, Cu, Hg, Ir, Li, Mo, Ni,Os, Pb, Pd, Pt, Rh, Ru, Sb, Se, Sn, Tl and V ) and observed minimal contribution to ICP-MS spectral intrferences.

Reagents and Chemicals
The reagents used to prepare the samples and standard for the method, trace metal grade ultrapure concentrated nitric acid, hydrochloric acid (J.T.Baker), thiourea for metal analysis (Sigma Aldrich),multielement standard of Ag,As, Au, Ba, Cd, Co, Cr, Cu, Hg, Ir, Li, Mo, Ni,Os, Pb, Pd, Pt, Rh, Ru, Sb, Se, Sn, Tl, and V are from inorganic venture.Ultrapure de-ionized water from a Milli-Q analytical reagent grade water purification system(Millipore) was used.All volumetric flasks used in preperations were made up of polypropylene (PP)and polymethyl pentane (PMP).

Diluent (0.076% Thiourea w/v)
Transferred into 1000 mL of volumetric flask made of polypropylene or polymethylpentene add about 0.76 g of thiourea and 25 mL of concentrated hydrochloric acid. Diluted to volume with de-ionised water.
The (0.076% thiourea) diluents selected to overcome the problem of low osmium recoveries due to formation of volatile Os oxide in the nitric acid medium,to prevent formation of osmium tetraoxide 0.076% thiourea used which yield acceptable osmium recoveries around 97%-99%.

Calibration Blank Solution (Blank)
Transfer into 50 mL volumetric flask made of polypropylene or polymethylpentene 3 mL of concentrated nitric acid, 1 mL of concentrated hydrochloric acid and 100 µL of ISTD solution as internal standard. Dilute to volume with diluent.

Internal Standard Stock Solution
A 10 ppm mixed internal standard solution contaning (Scandium and Dysporium) was introduced online into the spraychamber by using peristaltic pump.

Standard Stock Solution 1 Preparation
Transferred into 50 mL volumetric flask made of polypropylene or polymethylpentene.1 mL of concentrated nitric acid, respective volume of Cd 165μL ,Pb 165μL,Co 165 μL,As 500 μL,Hg 1000 μL,Ni 660 μL,Tl 265 μL elements solution and diluted the volume up to mark with de-ionized water.

Stock Solution-2 (SS-2)
Transferred into 50 mL volumetric flask made of polypropylene or polymethylpentene 1 mL of concentrated nitric acid, 2 mL of concentrated hydrochloric acid, respective volume of Stock

Preparation of Calibration Working Standard Solutions
The calibration standards were prepared at 30% (0.3J), 150% (1.5J) and 200% (2J) the target limit for each elemental impurities in the final analysis solution.

Sample Preparation
Duplicate replicates were prepared by weighing accurately about 100 mg of the substance and transferred into digestion tube quartz than added 3 mL of concentrated nitric acid, 1 mL of concentrated hydrochloric acid and 100 µL of ISTD solution as internal standard. Shaked each mixture carefully upto dissolving, Wait at least 30 min before the vessels are closed. Than sample was heated in the microwave reactor, when the microwave reactor temperature program finished, allowed the digestion vessels to cool down and then transfer sample solutions into a 50 mL volumetric flasks made of polypropylene or polymethylpentene and dilute to volume with diluent.

Reference Formula of Metal Content (ppm) in Sample
Metal content in ppm is calculated using the following formula: ng  c (ng/mL) = instrument read-out concentration V (mL) = final volume of dissolved sample (50 mL) m (mg) = sample weight (100 mg).
Three preperations at each spiking level were prepared and each solution was analysed in triplicate measurement.

Working standard solutions for linearity
To demonstrate Linearity, five (5) solutions at different concentrations were prepared, WS-1 Solution, WS-2 Solution, WS-3 Solution, WS-4 Solution and WS-5 Solutions. Transfered into five separate 50 mL volumetric flasks made of polypropylene or polymethylpentene added 3 mL of concentrated nitric acid, and 1 mL of concentrated hydrochloric acid and added as per below table.Each solution was analyzed in triplicate measurements.

Accuracy/Recovery
To demonstrate Accuracy, a single un-spiked sample and samples spiked with reference material, prepared in triplicate (3x), at concentrations of 0.5J, 1.0J and 1.5J were prepared. Each solution was analyzed in triplicate measurements. A Standard stock solution was added to nine sample solutions as shown in the table below.
During method development stage before the addition of Thiourea to the analysis matrix,osmium recoveries were in the range of 55-65%.Excellent Osmium spike recoveries ranging from 97% to 99 % were obtained due to thiourea addition as it prevents the formation of volatile osmium tetraoxide and this helped balance the accuracy of the analysis of osmium response in the calibration standards and will compensate for matrix effect.
The spiked sample solution recoveries was analysed by ICP-MS.Prior to ICP-MS analysis internal standard solution was was added to each solution. The endogeneous content of the unspiked sample was subtracted from the results of the spiked samples. before accuracy and precision were determined. A close inspection of the results from all nine sample matrices indicated that excellent average recoveries were obtained for each of the 24 elements (Ag, As, Au, Ba, Cd, Co, Cr, Cu, Hg, Ir, Li, Mo, Ni, Os, Pb, Pd, Pt, Rh, Ru, Sb, Se, Sn, Tl, and V) was within 70% to 150%.
All acceptance criteria described for accuracy were met as the spike recoveries for the mean of all six preperations at each spiking concentration for each element was within specification criteria i.e 70% -150% and the % RSD for each six replicates at each of the spiking concentrations for each element was ≤ 20%.

Specificity
To evaluate specificity of the method for the contents of Ag, As, Au, Ba, Cd, Co, Cr, Cu, Hg, Ir, Li, Mo,Ni, Os, Pb, Pd, Pt, Rh, Ru, Sb, Se, Sn, Tl and V in Sucroferric oxyhydroxide were compared with contents of Ag, As, Au, Ba, Cd, Co, Cr, Cu, Hg, Ir, Li, Mo, Ni, Os, Pb, Pd, Pt, Rh, Ru, Sb, Se, Sn, Tl, and V contents in Sucroferric oxyhydroxide in Accuracy test (Level 2).    Specificity was assessed to show the absence of isobaric and polyatomic interference via quantifying the spiked samples against the calibration standard solution and meeting the the requirements of accuracy.No interference observed the measured mass of any target element from the elements from the elements present in specificity solutions.

Precision (including Repeatability) & Intermediate Precision
A second analyst on a different day prepared and analysed six preperations of approximately 100% target limit spiked samples (J) with freshly prepared spiking solutions.The samples were quantified against fresh calibration standards.
The result determine for Intermediate Precision /Ruggedness are summarised in (Table 6). For each element the second analyst/day mean for all six preparations was within+20% of the mean result for the first analysis. The % RSD for all preparations (n=12) for each target element was <25%.All acceptance criteria described in USP Chapters <233/232> for ruggedness were met.

DISCUSSION
This method is developed to be cost effective and less hazardous method which is consider for safety assessment, so it is therefore essential to develop such kind of chromatographic methods which will characterize and determine identified as well as unidentified impurities present in active pharmaceutical ingredients. Identification of identified as well as unidentified impurities. This method is used to analyze and determine the probability of possible degradational impurities.
All pharmacopoeias include a test for heavy metals, the current heavy metals limit test as stated in pharmacopoeias EP 2.4.8 and USP 231 method has been the main reference for more than hundred years; the method has basically a limit of 10 ppm. The basic reaction is between metal impurities and thioacetamide to form sulphides. The intensity of the colored sulphide precipitate is compared with a lead reference standard.
The compendial method is nonspecific, less sensitive, non-specific, and time-consuming, labour intensive and mostly yield low recoveries and does not provide adequate recovery of the elements being tested., whereas in developed research method all these gaps are covered without any loopholes.
Further serious limitations of the visual heavy metals test are the lack of selectivity and the inability to detect some metals as platinum, iron, palladium, or nickel (frequently used as catalysts) which have to be determined. The color comparison test is difficult to conduct, time consuming and it is not able to detect some toxic elements. Therefore, great effort is currently being devoted for the multimetal screening development and validation of new procedures to control metals in pharmaceuticals that rely on modern advance analytical methodologies.Color comparison of test will be replaced by (ICP-MS) inductively coupled plasma mass spectrometry is a highly sensitive that achieves low detection limits for almost all elements.

CONCLUSION
Method for determination of Ag, As, Au, Ba, Cd, Co, Cr, Cu, Hg, Ir, Li, Mo,Ni, Os, Pb, Pd, Pt, Rh, Ru, Sb, Se, Sn, Tl,and V contents in Sucroferric oxyhydroxide is specific. All results met Acceptance Criteria for Specificity. Method adequately demonstrated Specificity for elemental Ag, As, Au, Ba, Cd, Co, Cr, Cu, Hg, Ir, Li, Mo, Ni, Os, Pb, Pd, Pt, Rh, Ru, Sb, Se, Sn, Tl, and V contents in Sucroferric oxyhydroxide. All system suitability parametersare with in range and satisfactory as per ICH guidelines [8].

CONTENT
It is not applicable.

ETHICAL APPROVAL
It is not applicable.

DISCLAIMER
I have declared that no competing interests exist. The products used for this research are commonly and predominantly use products in our area of research and country. There is absolutely no conflict of interest from producers of the products because we do not intend to use these products as an avenue for any litigation but for the advancement of knowledge. Also, the research was not funded by the producing company rather it was funded by personal efforts.