Determination of NaHCO3 Content in Alka-Seltzer Tablets: An Acoustic Approach

Research Article

Austin J Anal Pharm Chem. 2018; 5(2): 1103.

Determination of NaHCO3 Content in Alka-Seltzer Tablets: An Acoustic Approach

Crespo Sariol H,1, Mari&nTilde;o Peacok T1, Sánchez Roca á2, Carvajal Fals H2, Puente Torres J3, Yperman J4*, Carleer R4 and Brito Sauvanell á2

¹Faculty of Chemical Engineering, Laboratory of Applied Acoustics, Universidad de Oriente, Santiago de Cuba, Cuba

²Faculty of Mechanical Engineering, Universidad de Oriente, Santiago de Cuba, Cuba

³Facultyof Electrical Engineering, Universidad de Oriente, Santiago de Cuba, Cuba

4Research group of Applied and Analytical Chemistry, Hasselt University, Agoralaan building D, B-3590 Diepenbeek, Belgium; Email: [email protected]

*Corresponding author: Jan Yperman, Research group of Applied and Analytical Chemistry, Hasselt University, Agoralaan building D, B-3590 Diepenbeek, Belgium

Received: July 21, 2018; Accepted: September 12, 2018; Published: September 19, 2018


The feasibility of using acoustic emission analysis in order to determine the sodium bicarbonate (NaHCO3) content in Alka-Seltzer tablets is evaluated. The mass of reactive NaHCO3 of two different types of tablets has been assessed using the acoustic emission method based on the signal of the typical bubbling sound produced by CO2 formation in the acid-base reaction by water and lactic acid solution flooding the Alka-Seltzer tablets. The produced sound intensity can not only be related to the amount of NaHCO3 present but also to the differences in the total composition of the tablets. The NaHCO3 content in the tablet was acoustically determined using calibration curves from the bubbling sound produced by contacting moisturized sodium bicarbonate and lactic acid. NaHCO3 determined is in very good agreement with the bicarbonate content reported by the manufacturer using the cumulative energy parameter.

Keywords: Alka-Seltzer; NaHCO3 content; Acoustic emission; Bubbles


Alka-Seltzer is a well-known antacid and pain-relief medication that is dissolved in water before it is ingested. It is presented as an effervescent tablet that contains basically aspirin (acetylsalicylic acid: MW=180.16), citric acid (MW=192.13), and sodium bicarbonate (MW=84). As the tablet dissolves in water, sodium bicarbonate undergoes the acid–base reaction with the acids (citric and acetylsalicylic) contained in the tablet releasing carbon dioxide which causes the bubbling (effervescency) effect according to reaction I [1].

The content of carbonates and bicarbonates can be quantified by measuring parameters such as simple weight loss, gravimetric analysis, eudiometry, titration or volume of CO2 formed from the reaction with a dedicated acid [2,3]. The percent by mass of sodium bicarbonate in Alka-Seltzer tablets can be determined by the method of eudiometry [4].

Recently, a number of papers have been published describing an acoustic emission method for the characterization of activated carbons [5-7]. By flooding an activated carbon sample with water, it results in a sound emission produced by the bubbles escaping from the carbon cracks and pores when water molecules occupy the air filled voids inside of the material by displacing the present air. The bubbles escape through the bulk water and explode at the liquid surface. It was found that parameters of the carbon acoustic signal can be successfully correlated with the porosity of the material [5-7]. Bubbles and its corresponding sound patterns are in general widely studied, theoretically analyzed and applied in many scientific fields.

The analysis of acoustic and vibrating signals to characterize different events such as pump cavitation, cooking stages or stir spot welding process have proven to be accurate and sensitive techniques [8-11].

The effervescency effect of the of Alka-Seltzer tablets by releasing the CO2 after contacting with water (or an acid) produces a typical bubbling sound which can give information about the volume of gas produced in the acid-base reaction, therefore, it can be considered as an analogous phenomenon which is used for the activated carbon acoustic porous assessment [5-7]. Since the amount of CO2 is stoichiometry related with the reacting amount of NaHCO3, using a proper acoustic method to analyze the CO2 bubbling process, the amount of reacting bicarbonate can be quantified.

In this work, acoustic emission measurements of the typical Alka- Seltzer effervescence sound are evaluated in order to determine the reactive bicarbonate content in the tablet. This study is an approach to assess the NaHCO3 content not only in Alka-Seltzer tablets but also in other materials where the amount of carbonates/bicarbonates or other gas forming acids needs to be evaluated using an acid-base reaction.

Materials and Methods

Alka-Seltzer tablets

Two types of Alka-Seltzer tablets (Bayer Corporation) were evaluated: Alka-Seltzer Original (AZ-Original) and Alka-Seltzer Extra Strength (AZ-Extra). Table 1 shows the compounds listed in each type of tablet according to the reported values by the manufacturer labeled in the product.