Journal of Laboratory Chemical Education 2020, 8(2): 28-32 DOI: 10.5923/j.jlce.20200802.02 A Novel Test for Qualitative Detection of Carbohydrates Sangeeta Pandita Department of Chemistry, Zakir Husain Delhi College, J.L. Nehru Marg, New Delhi, India Abstract The contemporary chemistry teaching laboratories endeavour to integrate the current themes of safety, sustainability and simplicity in all aspects of experimental design. The qualitative analysis of carbohydrates is central to study of organic chemistry and biochemistry laboratory courses at undergraduate level. This paper presents a novel qualitative test for detection of carbohydrates using a single reagent, alkaline potassium hexacyanoferrate (III). This reagent shows a characteristic behaviour towards carbohydrates. The observation is developed and presented as a simple, safe and easy to perform test for detection of carbohydrates. The test is suitable for micro scale as well as mini scale quantities. It involves no special technique to perform, is quick to accomplish and gives unambiguous results. These attributes make it suitable to be adopted in teaching laboratories. Keywords Alkaline potassium hexacyanoferrate (III) reagent, Carbohydrates, Qualitative test 1. Introduction Carbohydrates are a fascinating class of biomolecules having unique structural features that distinguish them from other classes of organic compounds and also form the basis of their characteristic reactions [1,2]. It is due to this special aspect that carbohydrate analysis is fundamentally somewhat different from systematic qualitative analysis of other classes of organic compounds. Molisch test [3,4] is used to establish the presence of carbohydrates. This test requires the use of concentrated sulphuric acid which is to be poured into an aqueous solution (safety hazard) using a special technique. Also, the test gives difficult to interpret results if the concentration of carbohydrate and that of Molisch reagent (alcoholic solution of α- naphthol) are not in proper proportions. These aspects usually make it difficult for freshmen students to achieve results without ambiguity. In order to devise a simple protocol that poses no safety hazard, is easy to perform and gives unambiguous results, our attention was drawn to alkaline potassium hexacyanoferrate (III) oxidation of carbohydrates which has been studied in literature from several aspects including kinetic, qualitative and quantitative aspects [5-7]. Alkaline potassium hexacyanoferrate (III) has been used in our laboratory to afford clear distinction among different classes of carbohydrates [7]. During the course of the reaction, it was observed that carbohydrates cause disappearance of the greenish-yellow colour of the reagent to colourless state. This behaviour was found to be * Corresponding author: sangeetapandita@gmail.com (Sangeeta Pandita) Received: July 21, 2020; Accepted: August 2, 2020; Published: August 29, 2020 Published online at http://journal.sapub.org/jlce characteristic of carbohydrates. Other classes of commonly available organic compounds either caused no disappearance of colour or gave darker colours due to oxidation under test conditions. Disappearance of colour was observed to happen only in case of carbohydrates. In this paper, the observed unique behaviour of carbohydrates is developed and presented as a novel test for qualitative detection of carbohydrates as a class of organic compounds. 2. Experimental Design The experimental design of this study takes into account the choice of compounds, the methodology for accomplishing the test, ease of performing the test and clarity in interpreting the test results. Methodology has been detailed in the next section under the title Experimental Details. The choice of compounds was based on the type of compounds undergraduate students usually receive during qualitative organic analysis laboratory. These are listed in Table 1. Carbohydrates chosen are monosaccharides (aldoses and ketoses) and disaccharides (reducing and non reducing). Other compounds in Table 1 are representatives of carboxylic, carbonyl, ester, amino, substituted amino, nitro, alcoholic, phenolic and amide functions. 3. Experimental Details 3a. Preparation of alkaline potassium hexacyanoferrate (III) reagent The reagent used in this test is 20%/1% alkaline potassium hexacyanoferrate (III). It is prepared by dissolving 20 g NaOH pellets in 100 mL distilled water carefully. It