For sulfanilamide, in the second derivatives results, 54, 60, 66, 72, 74, 81[cm.sup.-1] are observed (54, 59, 67, and 73 [cm.sup.-1] in the absorption spectrum), so 73 [cm.sup.-1] band is formed by 72 and 74 [cm.sup.-1] bands; for caprolactam, 71 [cm.sup.-1] band is formed by 66, 69, and 71 [cm.sup.-1] child-bands; for acrylamide, weak band at 48 [cm.sup.-1] is emphasized in the second derivatives results, 67 [cm.sup.-1] band mainly has several child-bands: 64, 67, 70, 74, and 82 [cm.sup.-1]; for salicylamide, 40, 48, 54, 64, 69, 79 [cm.sup.-1] bands are observed compared to 48, 54, and 80 [cm.sup.-1] in the absorption spectrum.
The FIR spectra of benzamide, acrylamide, caprolactam, salicylamide and sulfanilamide, after automatic baseline correction shown in Figure 3 indicate that the five molecules have different band positions and relative band intensities.
For salicylamide, it has many bands in the region: 608, 564, 526, 515, 456, 421, 385, 296, 160, 146, 108, and 93 [cm.sup.-1].
For benzamide and salicylamide, there is one OH difference.
Fortunately, there are some calculation results for benzamide, salicylamide, and sulfanilamide .
For salicylamide, 30 [cm.sup.-1] band is assigned to twisting of ph-CON[H.sub.2]; 141[cm.sup.-1] band is assigned to out-of-plane vibration of whole molecule; 184 [cm.sup.-1] band is assigned to wagging of N[H.sub.2]; 247 [cm.sup.-1] band is assigned to out-of-plane wagging of whole molecule, especially ph ring; 275 [cm.sup.-1] band is assigned to rocking of N[H.sub.2], rocking of ph; 383 [cm.sup.-1] band is assigned to in-plane vibration of ph and torsion of (C=O-N[H.sub.2] and COH); 419 [cm.sup.-1] band is assigned to out-of-plane folding of ph and stretching of NH; 439 [cm.sup.-1] band is assigned to in-plane wagging of ph; twisting of (C=O-N[H.sub.2] and COH); 509 [cm.sup.-1] band is assigned to rocking of NH, rocking of (C=O and OH), in-plane wagging of ph, and so forth.
Spectral Characteristics and Construction of Calibration Curves of Salicylamide and Ascorbic acid
Analysis of Laboratory Prepared Mixtures of Salicylamide and Ascorbic acid
While there is no literature reveals determination of Salicylamide and Ascorbic acid in their binary mixture and pharmaceutical formulation and as shown in Fig.2 there is severe overlapping between their spectra so the objective is to establish different spectrophotometric methods for rapid quantification of Salicylamide and Ascorbic acid using the Area under curve dual wavelength isoabsorptive point and ratio subtraction spectrophotometric methods which are less expensive less time consuming and required less sophisticated equipment rather then the reported HPLC method.
Table-1: Determination of Salicylamide and Ascorbic acid in laboratory prepared mixtures by the proposed spectrophotometric methods.
Table-2: Determination of Salicylamide and Ascorbic acid in their pharmaceutical formulation by the proposed methods and application of standard addition technique.
Table-3: Results of assay validation parameters of the proposed methods for determination of Salicylamide and Ascorbic acid.