Study On Reactive Oxygen Species Mediated Determination Of Tetracyclines By New Chemiluminescence Methods And Its Mechanism

Antibiotics,one of the largest groups of pharmaceuticals and personal care products(PPCPs),have received increasing attention and scientific interest in recent years.The use of PPCPs in the medical field for preserving human and animal health has resulted in their undesirable accumulation in the environment and foodstuff.Antibiotic resistance represents a serious and growing human health threat worldwide,such as tetracycline antibiotics(TCAs).By considering the risks of TCAs in the food and ecosystem,the search for sensitive and selective analytical methodologies capable of ensuring food safety and consumers' confidence is necessary.(1)Novel chemiluminescence mechanisms of cerium(IV)and five tetracyclines in the absence and presence of Tween 80 are reported.The role of tetracyclines in the present chemiluminescence system was studied in detail by ultraviolet spectra and the singlet oxygen 1O2 probe 2-methyl-6-(4-methoxyphenyl)-3,7-dihydroimidazo[1,2-a]-pyrazin-3-one hydrochloride.It is the first report that cerium(IV)reacted with tetracyclines producing singlet oxygen 1O2 after breaking the organic skeleton and decomposition of peroxyacetic acid in the absence of the surfactant Tween.Furthermore,by examining the effects of sodium azide and the chemiluminescence spectra,the results indicated that the maximum chemiluminescence emission at approximately 480 nm was due to dimer emission of singlet oxygen 1O2 from the reaction between cerium(IV)and tetracyclines as well as the reaction of cerium(IV)and Tween 80,respectively.Moreover,the chemiluminescence signals were unaffected when the reaction was performed under anaerobic condition,indicating that dissolved oxygen was independent of this system.Under the optimal conditions,the analytical characteristics and parameters of the cerium(IV)-Tween 80-tetracyclines chemiluminescence system were investigated.The present method was successfully employed for the determination of tetracyclines in milk.(2)In this article,five tetracyclines(TCAs)showed ultrasensitive chemiluminescence(CL)based on the novel CL system of methoxylated Cypridina luciferin analogues(MCLA)and Ce(IV).It was found that the CL intensity of MCLA-Ce(IV)system was enhanced 30 times by adding 10 pmol chlortetracycline.Mechanisms of MCLA-Ce(IV)-TCAs were investigated by CL spectra,radical scavengers and UV spectra.The results indicated that singlet oxygen,resulting from the reaction between Ce(IV)and TCAs,was involved in the enhancement of CL phenomenon.This CL system coupling with flow injection analysis was developed for the determination of five common TCAs.Linear ranged from 100 fmol to 20 pmol(r>0.999)with limit of detection of 20 to 50 fmol(S/N=3).The sensitivity of the present method is comparable to that of UPLC-MS/MS detection for TCAs.(3)A novel,good sensitivity,simple operation and low cost chemiluminescence(CL)methods for the determination of TCAs was established.An ultraweak CL was observed when sodium periodate(NaIO4)and sodium bicarbonate(NaHCO3)reacts with hydrogen peroxide(H2O2)and was enhanced 30 times by adding 50 pmol metacycline.Mechanism of NaIO4-NaHCO3-H2O2-TCAs system were investigated by CL spectrum,radical scavengers,electron spin resonance(ESR)and LC-MS/MS.Hydroxyl radical(·OH)and superoxide anion radical(·O2-)were generated in the Na IO4-NaHCO3-H2O2-TCAs system.There action between ·OH radical and TCAs induced strong CL emission and hydroxyl TCAs were responsible for the emitter except chlortetracycline and 4-epichlortetracycline which processed different redox route comparing with other TCAs.The proposed method was developed to determine TCAs in milk and honey with with a detection limit of 90 fmol(S/N =3).The present work not only proposed a highly sensitive,differentiable CL method for TCAs but also provided new insight into advanced oxidation processes of TCAs.