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\begin{document}


\def\RunningAuthor{Chandan R. S. et al.}
\firstPage{3933}
\articleType{Original Article}
\receivedDate{04 Feb 2020}
\acceptedDate{03 Mar 2020}
\revisedDate{03 Mar 2020}
\journalVolume{2020, 11}
\journalIssue{3}
\journalDoi{ijrps.v11i3.2583}
\copyrightYear{2020}
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\def\journalTitle{International Journal of Research in Pharmaceutical Sciences}

\title{\textbf{Stability indicating assay method for the simultaneous estimation of Empagliflozin and Metformin HCl by RP-HPLC method}}
\author{Supriya~Reddy~K,  
            Chandan~R.~S.\textsuperscript{*},  
            Sai~Charan~A, 
            Akshay~N~\\[5pt]{Department of Pharmaceutical Analysis, JSS College of Pharmacy, JSS Academy of Higher Education and Research, Sri Shivarathreeshwara Nagara, Mysuru, Karnataka  {\textendash} 570015, India}}

\begin{abstract}
A Specific, Linear and Precise reversed phase- HPLC was developed for the simultaneous estimation of Metformin HCl and Empagliflozin and the column used is Zorbax SB Phenyl with length, Internal diameter and Particle size of 250mm, 4.6 mm and 5\ensuremath{\mu}m respectively. The Mobile phase is Phosphate buffer: ACN: Methanol in ratio 45:25:30. 1.0 ml/min was the used flow rate and the wavelength was adjusted to 220nm for detection. The retention time for Empagliflozin was found to be 5.5min and for Metformin was 9.3min. Both the APIs exhibited good linearity revealing correlation coefficient(R) of 0.9999. The percentage recoveries for Metformin and Empagliflozin was found to be 100.0 {\textendash} 100.9\% and 100.3 {\textendash} 102.4\% respectively which was found to be within the limit. Forced degradation studies were performed and the developed method has suitable specificity as no interference is observed with impurity spiked sample and placebo of Drug Product. The proposed drug products were subjected to various types of stress conditions according to ICH Q1 guidelines like acidic, alkaline, neutral, peroxide, and Thermal conditions. The degradation products were well resolved from the main peaks , thus indicating the stability- indicating nature of the method. The method was validated with respect to system suitability, linearity, accuracy, precision and robustness according to ICH guidelines and the proposed RP-HPLC Method was accurate, precise and linear for the simultaneous determination of Metformin and Empagliflozin in bulk and pharmaceutical formulations.  
\end{abstract}\def\keywordstitle{Keywords}

\begin{keywords}Simultaneous estimation,\newline Reversed Phase HPLC,\newline Validation,\newline FDS
\end{keywords}
\twocolumn[ \maketitle {\printKwdAbsBox}]
\makeatletter{\raggedright\textsuperscript{*}Corresponding Author\par Name:\ Chandan~R.~S.~\\ Phone:\ +91-9900622911 ~\\  Email:\ rschandan@jssuni.edu.in
        \par}\vspace*{-11pt}\hrulefill\par{\fontsize{12}{14}\selectfont ISSN: 0975-7538}\par% 
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        \makeatother
        
    
\section{Introduction}
Metformin hydrochloride (Met HCl) is 1,1-diMethylbiguanide hydrochloride. The molecular formula of Met HCL is C\ensuremath{_{4}}H\ensuremath{_{11}}N. HCl with the molecular weight of 165.63 g/mol. It is mainly used for the therapy for type-2 diabetes especially in people with overweight. It is generally used as first choice of drug in the management of type 2 diabetes. Common side effects of Met HCl include diarrhoea, nausea, and abdominal pain. The Structure for Metformin is given in the Figure~\ref{f-ff10e5414f4d}. \unskip~\citep{710689:16850238,710689:16850239}. 

MOA of Metformin is unique from other class of oral hypoglycaemic drugs. It decreases the blood glucose level by reducing the gluconeogenesis (production of hepatic glucose), thus decreasing the glucose absorption in intestine and results in increased uptake and utilization of peripheral glucose by increasing insulin sensitivity. This process will lead to the reduction of blood glucose, thus managing type 2 diabetes and exhibiting positive effects on glycaemic control.\unskip~\citep{710689:16850231}.  Molecular formula of Empagliflozin (Empa) is C\ensuremath{_{23}}H\ensuremath{_{27}}ClO\ensuremath{_{7\ }}and having a molecular weight of 450.91 g/mol. It is used as a medication along with exercise and diet for the therapy of type 2 diabetes. Structure of Empa is given in Figure~\ref{f-62a8c6ad63ac}.\unskip~\citep{710689:16850229,710689:16850235}\ensuremath{^{}}

Empagliflozin is sodium glucose co-transporter (SGLT-2) inhibitor. SGLT-2 is responsible for the uptake of glucose from the glomerular filtrate in kidney. It also contributes to the decreased hyperglycaemia and helps in weight loss and reduction of blood pressure. \unskip~\citep{710689:16850240}.  According to the literature survey, many analytical methods have been recorded for the estimation of individual drugs as well as combination by HPLC, UPLC, UV, LC/MS technique in dosage form. The intention of the study is to develop and validate simultaneous Method for two antidiabetic drugs with less time consumption. 
    
\section{Materials and Methods}
\textbf{Experimental}

Metformin and Empagliflozin, active pharmaceutical ingredients (APIs) were furnished by Dr. Reddy's laboratories, Hyderabad. All the reagents used are of HPLC grade.

\textbf{Apparatus}

The LC system consists of auto sampler HPLC designed by Waters and UV-Vis detector. The studies were carried out on phenyl column having length of 250mm and 4.6 mm of internal diameter and particle size of 5\ensuremath{\mu}m and it was monitored at 220 nm. Chromatogram was obtained by empower software. \unskip~\citep{710689:16850230,710689:16850228}. 

Zorbax SB Phenyl with length, internal diameter and particle size of 250mm, 4.6 mm and 5\ensuremath{\mu}m respectively were used as a column. PDA detector is used at 220nm.

\textbf{Reagents \& Material}

All the chemicals and reagents used are of AR grade. Metformin HCl and Empagliflozin were obtained from Dr. Reddy's Laboratories Pvt. Ltd., Hyderabad as a gift sample.

\textbf{Preparation of standard stock solution}

Metformin HCl and Empagliflozin were weighed in precise measures of 50 mg and 100 mg in two separate 100ml volumetric flasks. 70ml of diluent [water: acetonitrile in 50:50 (percent v/v)] was added to it, and was retained until it dissolved for sonication. Diluent was used to make up the volume, and for a correct blend. \unskip~\citep{710689:16850241,710689:16850236}\ensuremath{^{}}

\textbf{Preparation of working solutions}

5 ml is pipetted out form the stock solution into 100 ml of volumetric flask and the mark is made up by using water to get a concentration of 25 \ensuremath{\mu}g/ml and 50 \ensuremath{\mu}g/ml (Met HCl and Empa) respectively. \unskip~\citep{710689:16850233}\ensuremath{^{}}

\textbf{Chromatographic Conditions\ensuremath{^{}}}

The Table~\ref{tw-658ad65407ac} indicating the chromatographic parameters. \unskip~\citep{710689:16850235}. The Chromatograms of Blank and Standard are given in Figure~\ref{f-8f577e429494} and Figure~\ref{f-650fc921c644}.
    
\section{Results and Discussion}
The main aim of this was to develop a stable HPLC Method that indicated the simultaneous estimation of Metformin HCl and Empagliflozin. HPLC provides a quick and highly accurate Method and efficient when compared to other chromatographic techniques. While developing a Method, different trials were performed by changing the columns like Cyano, Hi chrom Altima, Zorbax phenyl etc., when cyano and Hi chrom Altima columns were used; results were not proper, a shift was observed in RT of Empagliflozin and Metformin peak shape was not good because tailing factor was more than 2. Different buffers such as pH 5.5 and, pH 7 phosphate were used which showed that the two main peaks were eluting at the same retention time, and by altering the organic phase ratio in the mobile phase by which there was a proper separation in both the peaks. The good peak shape was obtained with short rum time in the chromatographic parameters using Zorbax SB Phenyl column with pH 7.5 phosphate buffer: Acetonitrile: Methanol (45:25:30) as a mobile phase, Injection volume of 10\ensuremath{\mu}L and 1 mL/min flow rate. It was detected at 220 nm.\ensuremath{^{}}


\begin{table*}[!htbp]
\caption{\boldmath {Results for system suitability} }
\label{tw-2bdfcb7a8d2a}
\def\arraystretch{1.1}
\ignorespaces 
\centering 
\begin{tabulary}{\linewidth}{p{\dimexpr.3088\linewidth-2\tabcolsep}p{\dimexpr.24999999999999996\linewidth-2\tabcolsep}p{\dimexpr.2448\linewidth-2\tabcolsep}p{\dimexpr.1964\linewidth-2\tabcolsep}}
\tbltoprule \rowcolor{kwdboxcolor}\cAlignHack System suitability parameters \mbox{}\protect\newline  & \multicolumn{2}{p{\dimexpr(.4948\linewidth-2\tabcolsep)}}{\cAlignHack Observed value} & \cAlignHack Acceptance Criteria\\
\rowcolor{kwdboxcolor}\cAlignHack  & \cAlignHack Empagliflozin & \cAlignHack Metformin HCl & \cAlignHack \\
\tblmidrule 
Tailing factor for Empagliflozin and Metformin peaks from standard solution \mbox{}\protect\newline  &
  \cAlignHack 1.1 &
  \cAlignHack 1.5 &
  \cAlignHack Not more than 2.0\\
Theoretical plate count for Empagliflozin and Metformin peaks from standard solution \mbox{}\protect\newline  &
  \cAlignHack 13007 &
  \cAlignHack 13853 &
  \cAlignHack Not less than 2000\\
\%RSD for peak areas of Empagliflozin and Metformin peaks from five replicate injections of standard solution &
  \cAlignHack 0.02 &
  \cAlignHack 0.2 &
  \cAlignHack Not more than 2\%\\
\tblbottomrule 
\end{tabulary}\par 
\end{table*}

\begin{table*}[!htbp]
\caption{\boldmath {Results of Linearity} }
\label{tw-9b5910fd8878}
\centering 
\begin{threeparttable}

\def\arraystretch{1.1}
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\centering 
\begin{tabulary}{\linewidth}{p{\dimexpr.29528000000000006\linewidth-2\tabcolsep}p{\dimexpr.18691999999999993\linewidth-2\tabcolsep}p{\dimexpr.1621\linewidth-2\tabcolsep}p{\dimexpr.2056\linewidth-2\tabcolsep}p{\dimexpr.15010000000000002\linewidth-2\tabcolsep}}
\tbltoprule \rowcolor{kwdboxcolor}\cAlignHack Linearity Level \mbox{}\protect\newline  & \multicolumn{2}{p{\dimexpr(.34901999999999994\linewidth-2\tabcolsep)}}{\cAlignHack Empagliflozin} & \multicolumn{2}{p{\dimexpr(.3557\linewidth-2\tabcolsep)}}{\cAlignHack Metformin}\\
\rowcolor{kwdboxcolor}\cAlignHack  & \cAlignHack Concentration (\ensuremath{\mu}g/mL) & \cAlignHack Peak Area & \cAlignHack Concentration \mbox{}\protect\newline (\ensuremath{\mu}g/mL) & \cAlignHack Peak Area\\
\tblmidrule 
Linearity Solution-1 &
  \cAlignHack 10.0058  &
  \cAlignHack 260970  &
  \cAlignHack 2.5065 &
  \cAlignHack 72268\\
Linearity Solution-2 &
  \cAlignHack 20.0116  &
  \cAlignHack 523639  &
  \cAlignHack 10.0258 &
  \cAlignHack 288784\\
Linearity Solution-3 &
  \cAlignHack 50.0291  &
  \cAlignHack 1297452  &
  \cAlignHack 25.0646 &
  \cAlignHack 720507\\
Linearity Solution-4 &
  \cAlignHack 60.0349  &
  \cAlignHack 1566713  &
  \cAlignHack 50.1292 &
  \cAlignHack 1445975\\
Linearity Solution-5 &
  \cAlignHack 90.0523  &
  \cAlignHack 2335378  &
  \cAlignHack 60.1550 &
  \cAlignHack 1742904\\
Linearity Solution-6 \mbox{}\protect\newline  &
  \cAlignHack 120.0698  &
  \cAlignHack 3130478  &
  \cAlignHack 80.2067 &
  \cAlignHack 2316405\\
\cAlignHack \textbf{Linearity Parameters} \mbox{}\protect\newline  &
  \multicolumn{2}{p{\dimexpr(.34901999999999994\linewidth-2\tabcolsep)}}{\textbf{Empagliflozin}} &
  \textbf{Metformin} &
  \\
Slope &
  \multicolumn{2}{p{\dimexpr(.34901999999999994\linewidth-2\tabcolsep)}}{26024.691985} &
  28917.562787 &
  \\
Intercept &
  \multicolumn{2}{p{\dimexpr(.34901999999999994\linewidth-2\tabcolsep)}}{114.867417} &
  -1482.834656 &
  \\
Correlation Coefficient &
  \multicolumn{2}{p{\dimexpr(.34901999999999994\linewidth-2\tabcolsep)}}{0.9999875} &
  0.9999948 &
  \\
\% Bias at 100\% &
  \multicolumn{2}{p{\dimexpr(.34901999999999994\linewidth-2\tabcolsep)}}{0.01} &
  -0.2 &
  \\
Residual sum of squares &
  \multicolumn{2}{p{\dimexpr(.34901999999999994\linewidth-2\tabcolsep)}}{147436852.921254} &
  40073987.162193 &
  \\
\tblbottomrule 
\end{tabulary}\par 
\begin{tablenotes}\footnotesize 
    
\item{Correlation coefficient should be not less than 0.999.}
\end{tablenotes}
\end{threeparttable}

\end{table*}

\begin{table*}[!htbp]
\caption{\boldmath {Results of precision} }
\label{tw-216382d6029c}
\centering 
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\centering 
\begin{tabulary}{\linewidth}{p{\dimexpr.3023\linewidth-2\tabcolsep}p{\dimexpr.3715\linewidth-2\tabcolsep}p{\dimexpr.3262\linewidth-2\tabcolsep}}
\tbltoprule \rowcolor{kwdboxcolor}Sample No. & \multicolumn{2}{p{\dimexpr(.6977\linewidth-2\tabcolsep)}}{\cAlignHack \% Assay}\\
\rowcolor{kwdboxcolor} & Empagliflozin & Metformin\\
\tblmidrule 
1 &
  100.5  &
  101.3 \\
2 &
  100.6  &
  100.9 \\
3 &
  100.0  &
  100.0 \\
4 &
  99.9  &
  100.5 \\
5 &
  100.2  &
  100.2 \\
6 &
  100.5  &
  100.9 \\
Average &
  100.3 &
  100.6\\
*\% RSD &
  0.3 &
  0.5\\
\tblbottomrule 
\end{tabulary}\par 
\begin{tablenotes}\footnotesize 
    
\item{*\% RSD is percentage relative standard deviation and it should be not more than 2.0.}
\end{tablenotes}
\end{threeparttable}

\end{table*}

\begin{table*}[!htbp]
\caption{\boldmath {Results of Intermediate precision} }
\label{tw-c4e1424e03c0}
\centering 
\begin{threeparttable}

\def\arraystretch{1.1}
\ignorespaces 
\centering 
\begin{tabulary}{\linewidth}{p{\dimexpr.3352\linewidth-2\tabcolsep}p{\dimexpr.3248\linewidth-2\tabcolsep}p{\dimexpr.34\linewidth-2\tabcolsep}}
\tbltoprule \rowcolor{kwdboxcolor}\multicolumn{3}{p{\dimexpr(1\linewidth-2\tabcolsep)}}{Analyst-1, Column-1, System-1, Day-1}\\
\rowcolor{kwdboxcolor}S. No. & \multicolumn{2}{p{\dimexpr(.6647999999999999\linewidth-2\tabcolsep)}}{\% Assay}\\
\rowcolor{kwdboxcolor} & Empagliflozin & Metformin\\
\tblmidrule 
1 &
  100.5 &
  101.3\\
2 &
  100.6 &
  100.9\\
3 &
  100.0 &
  100.0\\
4 &
  99.9 &
  100.5\\
5 &
  100.2 &
  100.2\\
6 &
  100.5 &
  100.9\\
Average \mbox{}\protect\newline  &
  100.3 &
  100.6\\
\multicolumn{3}{p{\dimexpr(1\linewidth-2\tabcolsep)}}{\textbf{Analyst-2, Column-2, System-2, Day-2}}\\
1 &
  100.6 &
  99.8\\
2 &
  100.2 &
  99.9\\
3 &
  100.2 &
  99.5\\
4 &
  100.1 &
  99.6\\
5 &
  100.3 &
  99.9\\
6 &
  100.6 &
  100.2\\
Average  &
  100.3 &
  99.8\\
\% RSD &
  0.2 &
  0.2\\
$\ast\ast $C. \% RSD &
  0.2 &
  0.6\\
\tblbottomrule 
\end{tabulary}\par 
\begin{tablenotes}\footnotesize 
    
\item{*\% RSD is percentage relative standard deviation and it should be not more than 2.0.}
    
\item{$\ast\ast $Cumulative \% RSD of \% assay is calculated from both Method precision and Intermediate precision.}
\end{tablenotes}
\end{threeparttable}

\end{table*}

\begin{table*}[!htbp]
\caption{\boldmath {Results of Accuracy (Empagliflozin)} }
\label{tw-751ee225ba87}
\def\arraystretch{1.1}
\ignorespaces 
\centering 
\begin{tabulary}{\linewidth}{p{\dimexpr.11322000000000001\linewidth-2\tabcolsep}p{\dimexpr.17442\linewidth-2\tabcolsep}p{\dimexpr.25052\linewidth-2\tabcolsep}p{\dimexpr.25972\linewidth-2\tabcolsep}p{\dimexpr.20212000000000003\linewidth-2\tabcolsep}}
\tbltoprule \rowcolor{kwdboxcolor}S.No. & Spike level & Amount added `mg' & Amount found `mg' & \% Recovery\\
\tblmidrule 
1  &
  50\% level &
  5.92388  &
  6.04548  &
  102.0 \\
2 &
  100\% level &
  124.09796  &
  125.21444  &
  100.9 \\
3 &
  150\% level &
  190.98820  &
  191.87038  &
  100.4 \\
\tblbottomrule 
\end{tabulary}\par 
\end{table*}

\begin{table*}[!htbp]
\caption{\boldmath {Results of Accuracy (Metformin)} }
\label{tw-07b31e72a897}
\centering 
\begin{threeparttable}

\def\arraystretch{1.1}
\ignorespaces 
\centering 
\begin{tabulary}{\linewidth}{p{\dimexpr.12117999999999999\linewidth-2\tabcolsep}p{\dimexpr.17648\linewidth-2\tabcolsep}p{\dimexpr.24788\linewidth-2\tabcolsep}p{\dimexpr.24798000000000002\linewidth-2\tabcolsep}p{\dimexpr.20648\linewidth-2\tabcolsep}}
\tbltoprule \rowcolor{kwdboxcolor}S.No. & Spike level & Amount added `mg' & Amount found `mg' & \% Recovery\\
\tblmidrule 
1  &
  50\% level &
  250.32834  &
  250.65639  &
  100.1 \\
2 &
  100\% level &
  10000.56878  &
  10068.40012  &
  100.6 \\
3 &
  150\% level &
  15002.68450  &
  15022.93303  &
  100.1 \\
\tblbottomrule 
\end{tabulary}\par 
\begin{tablenotes}\footnotesize 
    
\item{Individual \% recovery should be between 97\% and 103\%.}
\end{tablenotes}
\end{threeparttable}

\end{table*}

\begin{table*}[!htbp]
\caption{\boldmath {Results of effect of variation in flow rate} }
\label{tw-bdcd2805818d}
\def\arraystretch{1.1}
\ignorespaces 
\centering 
\begin{tabulary}{\linewidth}{p{\dimexpr.27290000000000003\linewidth-2\tabcolsep}p{\dimexpr.14233333333333334\linewidth-2\tabcolsep}p{\dimexpr.15526666666666669\linewidth-2\tabcolsep}p{\dimexpr.1481666666666667\linewidth-2\tabcolsep}p{\dimexpr.13886666666666674\linewidth-2\tabcolsep}p{\dimexpr.14246666666666664\linewidth-2\tabcolsep}}
\tbltoprule \rowcolor{kwdboxcolor}System suitability parameters &  & \multicolumn{3}{p{\dimexpr(.4423000000000002\linewidth-2\tabcolsep)}}{\cAlignHack Observed value} & Acceptance Criteria\\
\rowcolor{kwdboxcolor} &  & 0.8 mL/min & 1.0 mL/min & 1.2 mL/min & \\
\tblmidrule 
Tailing factor for Empagliflozin and Metformin peaks from standard solution &
  Empagliflozin &
  1.2 &
  1.1 &
  1.1 &
  NMT 2.0\\
 &
  Metformin \mbox{}\protect\newline  &
  1.5 &
  1.5 &
  1.4 &
  \\
Theoretical plate count for Empagliflozin and Metformin peaks from standard solution &
  Empagliflozin &
  13732 &
  13007 &
  11096 &
  NLT 2000\\
 &
  Metformin \mbox{}\protect\newline  &
  13428 &
  13853 &
  12442 &
  \\
\%RSD for peak areas of Empagliflozin and Metformin peaks from five replicate injections of standard solution &
  Empagliflozin &
  0.1 &
  0.02 &
  0.1 &
  NMT 2.0\%\\
 &
  Metformin &
  0.1 &
  0.2 &
  0.2 &
  \\
\tblbottomrule 
\end{tabulary}\par 
\end{table*}

\begin{table*}[!htbp]
\caption{\boldmath {Results of effect of variation in column temperature} }
\label{tw-a109c5eff045}
\def\arraystretch{1.1}
\ignorespaces 
\centering 
\begin{tabulary}{\linewidth}{p{\dimexpr.3802\linewidth-2\tabcolsep}p{\dimexpr.16580000000000002\linewidth-2\tabcolsep}p{\dimexpr.11050000000000002\linewidth-2\tabcolsep}p{\dimexpr.10569999999999999\linewidth-2\tabcolsep}p{\dimexpr.10819999999999999\linewidth-2\tabcolsep}p{\dimexpr.12960000000000003\linewidth-2\tabcolsep}}
\tbltoprule \rowcolor{kwdboxcolor}\multicolumn{2}{p{\dimexpr(.5460000000000001\linewidth-2\tabcolsep)}}{\cAlignHack System suitability parameters} & \multicolumn{3}{p{\dimexpr(.3244\linewidth-2\tabcolsep)}}{\cAlignHack Observed value} & Acceptance Criteria\\
\rowcolor{kwdboxcolor} &  & 35\ensuremath{^\circ}C & 40\ensuremath{^\circ}C & 45\ensuremath{^\circ}C & \\
\tblmidrule 
Tailing factor for Empagliflozin and Metformin peaks from standard solution  &
  Empagliflozin &
  1.1  &
  1.1  &
  1.2  &
  \multicolumn{1}{p{\dimexpr(.12960000000000003\linewidth-2\tabcolsep)}}{\multirow{2}{\linewidth}{NMT 2.0}}\\
 &
  Metformin \mbox{}\protect\newline  &
  1.4  &
  1.5  &
  1.4  &
  \\
Theoretical plate count for Empagliflozin and Metformin peaks from standard solution  &
  Empagliflozin &
  11343  &
  13007  &
  12467  &
  \multicolumn{1}{p{\dimexpr(.12960000000000003\linewidth-2\tabcolsep)}}{\multirow{2}{\linewidth}{NLT 2000}}\\
 &
  Metformin \mbox{}\protect\newline  &
  11664  &
  13853  &
  13097  &
  \\
\%RSD for peak areas of Empagliflozin and Metformin peaks from five replicate injections of standard solution  &
  Empagliflozin &
  0.1  &
  0.02  &
  0.1  &
  \multicolumn{1}{p{\dimexpr(.12960000000000003\linewidth-2\tabcolsep)}}{\multirow{2}{\linewidth}{NMT 2.0\%}}\\
 &
  Metformin &
  0.1  &
  0.2  &
  0.1  &
  \\
\tblbottomrule 
\end{tabulary}\par 
\end{table*}

\begin{table*}[!htbp]
\caption{\boldmath {Results of effect of variation of pH of bufferin Mobile phase composition} }
\label{tw-ec59ad8e738c}
\def\arraystretch{1.1}
\ignorespaces 
\centering 
\begin{tabulary}{\linewidth}{p{\dimexpr.2972\linewidth-2\tabcolsep}p{\dimexpr.1462\linewidth-2\tabcolsep}p{\dimexpr.1334\linewidth-2\tabcolsep}p{\dimexpr.1405\linewidth-2\tabcolsep}p{\dimexpr.15189999999999998\linewidth-2\tabcolsep}p{\dimexpr.1308\linewidth-2\tabcolsep}}
\tbltoprule \rowcolor{kwdboxcolor}\multicolumn{2}{p{\dimexpr(.44339999999999996\linewidth-2\tabcolsep)}}{\cAlignHack System suitability parameters} & \multicolumn{3}{p{\dimexpr(.4258\linewidth-2\tabcolsep)}}{\cAlignHack Observed value} & Acceptance Criteria\\
\rowcolor{kwdboxcolor} &  & \cAlignHack pH 7.3 & \cAlignHack pH 7.5 & \cAlignHack pH 7.7 & \\
\tblmidrule 
Tailing factor for Empagliflozin and Metformin peaks from standard solution  &
  Empagliflozin &
  1.3 &
  1.1  &
  1.3 &
  \multicolumn{1}{p{\dimexpr(.1308\linewidth-2\tabcolsep)}}{\multirow{2}{\linewidth}{NMT 2.0}}\\
 &
  Metformin \mbox{}\protect\newline  &
  1.5 &
  1.5  &
  1.7 &
  \\
Theoretical plate count for Empagliflozin and Metformin peaks from standard solution  &
  Empagliflozin &
  7199 &
  13007  &
  7577 &
  \multicolumn{1}{p{\dimexpr(.1308\linewidth-2\tabcolsep)}}{\multirow{2}{\linewidth}{NLT 2000}}\\
 &
  Metformin \mbox{}\protect\newline  &
  6673 &
  13853  &
  7200 &
  \\
\%RSD for peak areas of Empagliflozin and Metformin peaks from five replicate injections of standard solution  &
  Empagliflozin &
  0.04 &
  0.02  &
  0.1 &
  \multicolumn{1}{p{\dimexpr(.1308\linewidth-2\tabcolsep)}}{\multirow{2}{\linewidth}{NMT 2.0\%}}\\
 &
  Metformin &
  0.1 &
  0.2  &
  0.5 &
  \\
\tblbottomrule 
\end{tabulary}\par 
\end{table*}

\begin{table*}[!htbp]
\caption{\boldmath {Results of Forced degradation studies (Empagliflozin)} }
\label{tw-20e946b0d3bb}
\def\arraystretch{1.1}
\ignorespaces 
\centering 
\begin{tabulary}{\linewidth}{p{\dimexpr.1667\linewidth-2\tabcolsep}p{\dimexpr.2072\linewidth-2\tabcolsep}p{\dimexpr.1282\linewidth-2\tabcolsep}p{\dimexpr.1331\linewidth-2\tabcolsep}p{\dimexpr.13010000000000002\linewidth-2\tabcolsep}p{\dimexpr.1182\linewidth-2\tabcolsep}p{\dimexpr.1165\linewidth-2\tabcolsep}}
\tbltoprule \rowcolor{kwdboxcolor}\cAlignHack Name of Degradation \mbox{}\protect\newline  & \cAlignHack Conditions & \cAlignHack \% degradation & \cAlignHack Purity Angle & \cAlignHack Purity Threshold & \cAlignHack Purity Flag & \cAlignHack Interference\\
\tblmidrule 
Sample As such  &
  \cAlignHack NA  &
  \cAlignHack NA  &
  \cAlignHack 0.131  &
  \cAlignHack 0.301  &
  \cAlignHack No  &
  \cAlignHack Not Applicable\\
Acid degradation  &
  15mL of 5N HCl, heating at 80\ensuremath{^\circ}C for 16 Hour  &
  \cAlignHack 3.4  &
  \cAlignHack 0.340  &
  \cAlignHack 0.345  &
  \cAlignHack No  &
  \cAlignHack No\\
Base Degradation  &
  5mL of 5N NaOH at bench top for 1 Hour  &
  \cAlignHack 0.7  &
  \cAlignHack 0.163  &
  \cAlignHack 0.323  &
  \cAlignHack No  &
  \cAlignHack No\\
Peroxide Degradation  &
  10mL of 30\% H2O2 at bench top for 48 Hours  &
  \cAlignHack 1.3  &
  \cAlignHack 0.029  &
  \cAlignHack 0.280  &
  \cAlignHack No  &
  \cAlignHack No\\
Photolytic degradation  &
  Visible light for 1.2 million Lux hrs and UV light for 200 watt hour/Meter square  &
  \cAlignHack 0.2  &
  \cAlignHack 0.127  &
  \cAlignHack 0.298  &
  \cAlignHack No  &
  \cAlignHack No\\
Humidity Degradation  &
  90\% RH at 25\ensuremath{^\circ}C for 7 days  &
  \cAlignHack 0.3  &
  \cAlignHack 0.161  &
  \cAlignHack 0.394  &
  \cAlignHack No  &
  \cAlignHack No\\
Hydrolytic Degradation  &
  5mL of water, heating at 80\ensuremath{^\circ}C for 2 Hours  &
  \cAlignHack 0.4  &
  \cAlignHack 0.145  &
  \cAlignHack 0.308  &
  \cAlignHack No  &
  \cAlignHack No\\
Thermal Degradation  \mbox{}\protect\newline  &
  105\ensuremath{^\circ}C for 22 Hours  &
  \cAlignHack 0.2  &
  \cAlignHack 0.168  &
  \cAlignHack 0.313  &
  \cAlignHack No  &
  \cAlignHack No\\
\tblbottomrule 
\end{tabulary}\par 
\end{table*}

\begin{table*}[!htbp]
\caption{\boldmath {Results of Forced degradation studies (Metformin)} }
\label{tw-c316861bb00a}
\centering 
\begin{threeparttable}

\def\arraystretch{1.1}
\ignorespaces 
\centering 
\begin{tabulary}{\linewidth}{p{\dimexpr.1618\linewidth-2\tabcolsep}p{\dimexpr.2291\linewidth-2\tabcolsep}p{\dimexpr.1319\linewidth-2\tabcolsep}p{\dimexpr.12129999999999999\linewidth-2\tabcolsep}p{\dimexpr.12020000000000001\linewidth-2\tabcolsep}p{\dimexpr.1054\linewidth-2\tabcolsep}p{\dimexpr.1303\linewidth-2\tabcolsep}}
\tbltoprule \rowcolor{kwdboxcolor}Name of Degradation \mbox{}\protect\newline  & Conditions & \% degradation & Purity Angle & Purity Threshold & Purity Flag & Interference\\
\tblmidrule 
Sample As such  &
  NA  &
  NA  &
  0.033  &
  0.198  &
  No  &
  Not Applicable\\
Acid degradation  &
  5mL of 5N HCl, heating at 80\ensuremath{^\circ}C for 1 Hour  &
  1.2  &
  0.035  &
  0.200  &
  No  &
  No\\
Base Degradation  &
  5mL of 5N NaOH heating at 60\ensuremath{^\circ}C for 45 minutes  &
  5.7  &
  0.034  &
  0.198  &
  No  &
  No\\
Peroxide Degradation  &
  5mL of 30\% H2O2 at bench top for 1 Hour  &
  1.2  &
  0.036  &
  0.198  &
  No  &
  No\\
Photolytic degradation  &
  Visible light for 1.2 million Lux hrs and UV light for 200 watt hour/Meter square  &
  0.7  &
  0.048  &
  0.198  &
  No  &
  No\\
Humidity Degradation  &
  90\% RH at 25\ensuremath{^\circ}C for 7 days  &
  0.3  &
  0.035  &
  0.199  &
  No  &
  No\\
Hydrolytic Degradation  &
  5mL of water, heating at 80\ensuremath{^\circ}C for 2 Hours  &
  0.9  &
  0.032  &
  0.197  &
  No  &
  No\\
Thermal Degradation  &
  105\ensuremath{^\circ}C for 22 Hours  &
  0.8  &
  0.038  &
  0.199  &
  No  &
  No\\
\tblbottomrule 
\end{tabulary}\par 
\begin{tablenotes}\footnotesize 
    
\item{Net degradation should be between 5\% and 20\% in atleast one stress condition.}
    
\item{Peak purity {\textendash} Purity Angle should be less than Purity Threshold and peak should not have any flag in purity table.}
\end{tablenotes}
\end{threeparttable}

\end{table*}

\begin{table*}[!htbp]
\caption{\boldmath {Final Chromatographic conditions} }
\label{tw-658ad65407ac}
\def\arraystretch{1.1}
\ignorespaces 
\centering 
\begin{tabulary}{\linewidth}{p{\dimexpr.4878\linewidth-2\tabcolsep}p{\dimexpr.5122\linewidth-2\tabcolsep}}
\tbltoprule \rowcolor{kwdboxcolor}Chromatographic conditions & Specification\\
\tblmidrule 
Column  &
  Zorbax SB Phenyl 250*4.6,5\ensuremath{\mu}  \\
Mobile Phase &
  Ph 7.5 phosphate buffer\\
Injection volume &
  10\ensuremath{\mu}L \\
Flow rate &
  1 ml/min\\
Column temperature &
  40\ensuremath{^\circ}C \\
Wavelength &
  220nm\\
\tblbottomrule 
\end{tabulary}\par 
\end{table*}

\bgroup
\fixFloatSize{images/88fe0662-467c-404b-874e-881340537383-upicture1.png}
\begin{figure}[!htbp]
\centering \makeatletter\IfFileExists{images/88fe0662-467c-404b-874e-881340537383-upicture1.png}{\includegraphics{images/88fe0662-467c-404b-874e-881340537383-upicture1.png}}{}
\makeatother 
\caption{\boldmath {Metformin}}
\label{f-ff10e5414f4d}
\end{figure}
\egroup

\bgroup
\fixFloatSize{images/97918424-9fd9-42ff-aa17-3318ea152600-upicture2.png}
\begin{figure}[!htbp]
\centering \makeatletter\IfFileExists{images/97918424-9fd9-42ff-aa17-3318ea152600-upicture2.png}{\includegraphics{images/97918424-9fd9-42ff-aa17-3318ea152600-upicture2.png}}{}
\makeatother 
\caption{\boldmath {Empagliflozin}}
\label{f-62a8c6ad63ac}
\end{figure}
\egroup

\bgroup
\fixFloatSize{images/70c2dfef-a632-4c02-9350-a5b56ff6667f-upicture3.png}
\begin{figure}[!htbp]
\centering \makeatletter\IfFileExists{images/70c2dfef-a632-4c02-9350-a5b56ff6667f-upicture3.png}{\includegraphics{images/70c2dfef-a632-4c02-9350-a5b56ff6667f-upicture3.png}}{}
\makeatother 
\caption{\boldmath {Chromatogram of Blank}}
\label{f-8f577e429494}
\end{figure}
\egroup

\bgroup
\fixFloatSize{images/473c153c-63d9-4907-a6a1-c709d4d4a672-upicture4.png}
\begin{figure}[!htbp]
\centering \makeatletter\IfFileExists{images/473c153c-63d9-4907-a6a1-c709d4d4a672-upicture4.png}{\includegraphics{images/473c153c-63d9-4907-a6a1-c709d4d4a672-upicture4.png}}{}
\makeatother 
\caption{\boldmath {Chromatograms of Metformin HCl and Empagliflozin}}
\label{f-650fc921c644}
\end{figure}
\egroup

\bgroup
\fixFloatSize{images/de752df5-51ed-4e15-898f-c01f30beddc4-upicture5.png}
\begin{figure}[!htbp]
\centering \makeatletter\IfFileExists{images/de752df5-51ed-4e15-898f-c01f30beddc4-upicture5.png}{\includegraphics{images/de752df5-51ed-4e15-898f-c01f30beddc4-upicture5.png}}{}
\makeatother 
\caption{\boldmath {Calibration curve of Empagliflozin}}
\label{f-1a4f150fdb26}
\end{figure}
\egroup

\bgroup
\fixFloatSize{images/4d970585-51a7-4530-85d9-47283a29e207-upicture6.png}
\begin{figure}[!htbp]
\centering \makeatletter\IfFileExists{images/4d970585-51a7-4530-85d9-47283a29e207-upicture6.png}{\includegraphics{images/4d970585-51a7-4530-85d9-47283a29e207-upicture6.png}}{}
\makeatother 
\caption{\boldmath {Calibration curve of Metformin }}
\label{f-fd2ec4f6eeef}
\end{figure}
\egroup
\textbf{System Suitability}

Suitability tests are conducted to check the instrument's reproducibility and resolution. The theoretical plate count, the percentage of RSD and the tailing factors shown in Table~\ref{tw-2bdfcb7a8d2a} were within the limit. \unskip~\citep{710689:16850242}

\textbf{Linearity}

Linearity was performing by taking concentrations of 10-120 \ensuremath{\mu}g/mL for Empagliflozin and 2-80 \ensuremath{\mu}g/mL for Metformin HCl. The graph was found to be linear when plotted between concentration versus peak area as shown in the Figure~\ref{f-1a4f150fdb26} and Figure~\ref{f-fd2ec4f6eeef}, Table~\ref{tw-9b5910fd8878}. \unskip~\citep{710689:16850232}

\textbf{Precision}

Precision of a system is given as degree of closeness between the same quantity replicate measurements.

\textbf{Method Precision}

The precision was accomplished by taking six preparations as per the test protocol and evaluating the \% assay and \% RSD and was found to be within the limit as given in Table~\ref{tw-216382d6029c}.

\textbf{Intermediate Precision}

To demonstrate the ruggedness of the method, test was conducted by variability of systems, analyst to analyst and day to day together by performing assay on six samples as per test Method. 

The \% Assay and \% RSD was calculated for both the drugs and was found to be within the limit as given in Table~\ref{tw-c4e1424e03c0}.

\textbf{Accuracy}

Accuracy was executed by taking different levels of API concentrations i.e., 50\%, 100\% and 150\% and spiked on three placebo preparations. The percentage recovery was within the limits as given in Table~\ref{tw-751ee225ba87} and Table~\ref{tw-07b31e72a897}.

\textbf{Robustness}

The analytical method's robustness was achieved by altering various chromatographic parameters such as flow rate alterations of 0.8 ml/min and 1.2 ml/min, column temperature alterations of 35\ensuremath{^\circ}C and 45\ensuremath{^\circ}C, organic phase and aqueous phase ratios in mobile phase and buffer pH, i.e. pH 7.3 and 7.7, respectively. The findings are presented in Table~\ref{tw-bdcd2805818d}, Table~\ref{tw-a109c5eff045}, Table~\ref{tw-ec59ad8e738c}.

\textbf{Specificity}

Specificity studies were carried for drug product and drug substance by comparing the plots with diluents, placebo and impurities. 

Peak purity tests were also carried out.\unskip~\citep{710689:16850237}

\textbf{Forced degradation studies}

FDS was carried out on Empagliflozin and Metformin, where the API are subjected to different stress conditions like Acid, Base, Oxidation, Thermal, Photolytic and Humidity. Acid stress was performed by adding 15 ml of 5 N HCl, heating for 16 Hour at 80\ensuremath{^\circ}C for Empagliflozin, while, Metformin was stressed with 5N of HCl, heated for 1 Hour at 80\ensuremath{^\circ}C. Base stress was done by adding 5ml of 5N NaOH, kept on bench top for 1 Hour for Empagliflozin, and 5ml 0f 5N NaOH heated at 60\ensuremath{^\circ}C for 45 minutes for Metformin. Oxidative stress was done by adding 10ml and 5ml of 30\% H\ensuremath{_{2}}O\ensuremath{_{2}} for Empagliflozin and Metformin respectively and leave for 1 Hour on bench top. Hydrolytic stress was performed by addition of 5ml water and then warmed up at 80\ensuremath{^\circ}C for 2 Hour for both the drugs. The drugs were stressed with heat at 105\ensuremath{^\circ}C for 22 Hours and with humidity at 90\% RH for 7 days at 25\ensuremath{^\circ}C. Photolytic degradation was performed by exposing the drugs to visible light in the range 1.2 million Lux hours and UV light of 200 Watt hour/Meter square. The results are given in Table~\ref{tw-20e946b0d3bb} and Table~\ref{tw-c316861bb00a}. \unskip~\citep{710689:16850234,710689:16850237}

\textbf{Assay of marketed formulation}

Accurately weighed 10 tablets were powdered and the weight was taken equivalent to 5 mg and 500 mg of Empa and Met HCl respectively in 250 ml flask. Sonication was done for 60 mins after addition of 200 ml of diluent with occasional shaking. It is then made up to the mark with diluent and centrifuged for 15mins at 4000 rpm. The above solution is then diluted to get a concentration of 5\ensuremath{\mu}g/ml of Empa and 25\ensuremath{\mu}g/ml of Met.
    
\section{Conclusion }
The simultaneous method developed was tested in compliance with the guidelines of ICH Q2 (R1), and was within the limits. It can be assumed that the system is efficient, reliable and consistent and can be used to regular formulation testing.
\section*{Acknowledgement}The writers are very thankful to Dr Reddy's Laboratories, Hyderabad for supplying Met and Empa gift samples.

\textbf{Conflict of Interest}

None.

\textbf{Funding Support}

None.


    

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