A Highly Specific Colorimetric Method for On-Spot Determination of Lidocaine Using Color Kit and Application of Uncertainty Principles

A simple, accurate, precise, selective and detectable Colorimetric method was developed for estimation of Lidocaine in five different Pharmaceutical Formulations. The method is an azo C-coupling reaction where Lidocaine undergoes series of reaction and finally couples with resorcinol to form yellow color azo compound. The colored complex was measured at 430 nm. Beers law was obeyed in concentration range of 0.05-0.8 ug/ml. The method was validated and was found to be accurate, precise and robust with limit of detection and quantification to be 0.014 and 0.045 ug/ml. The Color kit was also developed for On-Spot detection of Lidocaine. Measurement uncertainty principles were also adopted to obtain reliable results where the process of uncertainty started from specifying measurand, then identifying uncertainty sources by cause-effect diagram, quantification of these sources of uncertainty and then finally calculating combined standard uncertainty and expanded uncertainty. In the present experiment, Concentration of sample and mass of sample was the major contributor towards uncertainty for all five Formulations. From the five formulations combined standard uncertainty of Transdermal patch was high, followed by Aerosol, Ointment, Gel and Injection. Keywords: Lidocaine, Uncertainty, Transdermal patch, Aerosol, Injection, Ointment, Gel