Spectrophotometric determination of ammonia using ninhydrin assay and kinetic studies

Abstract

A spectrophotometric method for the determination of ammonia in aqueous media was investigated. This newly developed method for the reaction of ammonia with ninhydrin found to be simple, accurate and precise. A deep red color product was formed in the presence of sodium hydroxide at wavelength of 508 nm. The effects of variables such as temperature, time, acidity and reagents concentration have been evaluated to select the appropriate conditions for this reaction. Beer's law is obeyed; the calibration curve is linear over the range of 2×10 -4 -1.4×10 -3 M of ammonia with regression coefficient (r 2 ) of 0.994 (n = 7). The calculated molar absorptivity and Sandell's sensitivity values are 1.069×10 3 L/mol.cm and 0.015 μg/cm 2 , respectively. The limits of detection (LOD) and quantification (LOQ) are calculated to be 1.2×10 -5 and 3.6×10 -5 M, respectively. The intra-day accuracy expressed as relative error was less than 0.5% with precision (RSD) ranging from 0.49 to 1.55%. The interday accuracy ranged (RSD) from 0.49 to 1.90 % with a relative error was less than 1.50 %. The stoichiometry of this reaction was determined to be of 1:2 between ammonia and ninhydrin with first order reaction.

Spectrophotometric method for determination of ranitidine hydrochloride in bulk and in pharmaceutical preparation using ninhydrin

“…The accuracy for this analytical method is investigated; the %relative error (%RE) for each analysis (Intra-and Interday accuracy) was calculated as shown in Table 2. The small values of %RE indicate that the reference amount and the found amount are close to each other [18]. Statistical analysis was done for the Intraday and interday using F-test and the results are 2.7 and 4.4, respectively, these values indicate that there is no bias between the reference concentration and the actual concentration for ranitidine hydrochloride at 95% confidence level.…”

“…The spectrophotometric method takes a unique position because of its sensitivity, accuracy, rapidity, and simplicity. The kinetic spectrophotometer methods such as initial rate and fixed time methods have a great attention because of selectivity and because there are no interferences due to other chemical reagents during measurement the colored complex in the aqueous media for which we used the two kinetic methods in this research [17][18][19].…”

“…The experimental K values in Table 4 were used to plot the linear curve; log K versus log C. The linear regression equation is: Log K = 0.9884x+2.224, (r 2 = 0.9774), the slope value which is n is 0.9884 (≈1) this confirming that the order of the reaction is the first one. The data analysis was performed at 95% confidence level, the standard error of the slope is ±0.106 and the standard error of the intercept is ±0.179 [18,21].…”

Sulfonic acid functionalized zirconium-based metal–organic framework for the selective detection of copper(ii) ions

“…The presence of functional groups in MOFs is highly advantageous for the selective sensing of different analytes. The selective sensing of heavy metal ions, 9,10 reactive oxygen species (ROS), 11 volatile organic compounds (VOCs), 12 and toxic anions 8 by chromatography, 13 electrochemistry, 14 voltammetry, 15 and spectrophotometric 16 methods is time-consuming and complicated whereas, fluorescence sensing is rapid, selective, sensitive and simple to carry out. Because of the above advantages of the fluorescence-based technique over the other techniques, scientists working in the field of sensing prefer this method.…”

A newly designed sticker-plastic sheet platform and smartphone-based digital imaging for protein assay in food samples with downscaling Kjeldahl digestion

“…It would be of interest to apply colorimetric determination for ammonia/ammonium produced from Kjeldahl digestion as an alternative to the conventional titration. Various reagents for the purpose may be available including indophenol or Berthelot (alkali-phenol), [19][20][21] Nessler (potassium mercuric iodide in alkaline solution), 10,19,22,23 ninhydrin, 24,25 o-phthalaldehyde, 26,27 and acetyl acetone. 28,29 Among those, Nessler's reagent is a commonly used reagent in environmental laboratories.…”