Chemometrics-assisted spectrophotometric determination of certain β-lactam antibiotics combinations

Multivariate and derivative spectrophotometric techniques (first derivative and derivative ratio)
were developed for the determination of four β-lactam antibiotic binary mixtures; ampicillin with flucloxacillin
(mix I), ampicillin with dicloxacillin (mix II), amoxicillin with flucloxacillin (mix III) and amoxicillin with dicloxacillin
(mix IV) in pharmaceutical combinations containing these compounds. The simultaneous determination of
these compounds was accomplished by first derivative (dA/dλ) spectrophotometric technique, applying
zero-crossing technique and first derivative of the ratio spectrum. The influence of Δλ for obtaining the
first derivative of the ratio spectra and the effect of the divisor concentration on the calibration graphs were
studied. Lastly by multivariate methods; (classical least squares (CLS) and principle component regression
(PCR)). Absorption spectra of compounds were used to optimize the spectral data set performs the calibration
by CLS and PCR. These calibration models were evaluated by internal validation (prediction of compounds
in its own designed training set of calibration), by cross-validation (obtaining statistical parameters that
show the efficiency for a calibration fit model) and by external validation over synthetic and pharmaceutical
mixtures. The four described procedures were successfully applied to the determination of these compounds
in synthetic mixtures and in pharmaceutical preparations with high percentage of recovery, accuracy
and precision. The procedures do not require any separation step.
Keywords: β-lactam antibiotics; Classical least squares; Derivative ratio spectrum; First derivative
spectrophotometry; Principle component regression