in order to confirm the suitability of arp reference standard, H-NMR analysis was carried out as described in section 2.1. the observed chemical shifts well agreed with literature data[21]. quantitative analysis was carried out by comparing the integrated of H-NMR spectra. the calculated purity degree of arp resulted in 99+2%, in good agreement with that declared by the provider(99.7%).these data confirm the suitability of the arp standard employed