One of the widely used antibiotics of the penicillin series in medicine are amoxicillin and amoxiclav – the representatives of "protected" penicillins. To control the concentration of these antibiotics, HPLC, spectrophotometry, capillary electrophoresis are applicable, which are long-lasting, require expensive equipment, operators and are not applicable for the express determination of aminopenicillins in biological and medicinal aqueous.