Experimental design and machine learning strategies for parameters screening and optimization of Hantzsch condensation reaction for the assay of sodium alendronate in oral solution Mohamed A. Korany, a Marwa A. A. Ragab, * a Rasha M. Youssef a and Mostafa A. Afify b An experimental design was adopted to attain the optimum reaction parameters of chemical derivatization of anhydrous sodium alendronate in an oral solution formula via Hantzsch condensation reaction. All reaction controlling variables, namely, time of reaction, temperature, reagent ratio and volume and buffer type, pH and volume were studied using the Plackett–Burman screening design to determine significant variables. Reaction temperature and pH of the buffer solution were found to be significant variables. Optimization was performed using the central composite design to get the optimum levels of these variables. Moreover, a comparison was made with artificial neural networks and support vector machines. The same results were obtained with low percentage relative error. After carrying out the spectrophotometric analysis, interferences from oral solution excipients were eliminated with a simple extraction procedure before measuring the absorbance at 340 nm. Satisfactory results of sample analysis were obtained and they were in good agreement with the label claim. A linear calibration graph of absorbance versus concentration was obtained with very low value of intercept and high value of correlation coefficient (0.9999) in the range of 2.44–34.10 mg mL 1 . The proposed spectrophotometric method was fully validated in accordance with ICH guidelines. Statistical comparison with a reported reference method showed similar results with respect to accuracy and precision. 1. Introduction Anhydrous sodium alendronate (ALN); (4-amino-1- hydroxybutylidene) diphosphonic acid mono sodium salt; (Fig. 1) is an aminobisphosphonate with general properties similar to those of the other bisphosphonates. 1,2 It is a potent inhibitor of bone resorption and is given for the management of osteoporosis either alone or with vitamin D. ALN is used for the treatment of Paget's disease of bone. It has also been given in the treatment of bone metastases and hypercalcaemia of malignancy. ALN tablet formulation has a precaution that patients should swallow entire tablets with plenty of water. Thus, a single dose 75 mL of ALN oral solution was formu- lated. 1,2 ALN structure lacks any chromophore, and hence it cannot be determined by direct spectrophotometric methods. ALN is official in the USP 36 and BP 2013. The official methods reported for ALN assay exhibit some difficulties and need sophisticated instruments. 2,3 For the USP method of ALN assay in tablets, the reagent used for precolumn derivatization is very toxic and carcinogenic, 9-uorenylmethyl chloroformate. Furthermore, separation from excess reagent is needed by carrying out an extraction step using methylene chloride. Next, chromatographic separation was conducted using the styrene– DVB polymer column with UV detection. 2 The BP method depends on direct assay using ion exchange chromatography, which is known to be time consuming as the equilibration of the column takes a long time, and inverse UV detection. 3 Therefore, several methods were reported for ALN assay. Spectrophotometric methods were reported for the assay of ALN. 4–14 However, the proposed method has limits of detection and quantitation that are considerably lower than those of many other published methods. 5–7,12,13 Moreover, some of the mentioned spectrophotometric methods have a narrow linear dynamic range when compared to the proposed method. 4,13,14 In Fig. 1 Chemical structure of ALN. a Faculty of Pharmacy, Department of Pharmaceutical Analytical Chemistry, University of Alexandria, El-Messalah, Alexandria 21521, Egypt. E-mail: marmed_2001@yahoo. com; Fax: +20 3 4873273; Tel: +20 3 4871317 b Borg Pharmaceutical Industries, Borg El-Arab new city – Industrial Zone 3 – Area 3 – district 17, Alexandria, Egypt Cite this: RSC Adv. , 2015, 5, 6385 Received 20th October 2014 Accepted 4th December 2014 DOI: 10.1039/c4ra12750a www.rsc.org/advances This journal is © The Royal Society of Chemistry 2015 RSC Adv. , 2015, 5, 6385–6394 | 6385 RSC Advances PAPER Published on 04 December 2014. Downloaded by RSC Internal on 05/01/2015 17:13:58. View Article Online View Journal | View Issue