Studies On Sequential Injection Coupled With Spectrophotometry For The Determination Of Antioxidant Capacity Of Tea And Iron In Environmental Water Samples

Today,the cardiocerebrovascular disease,diabetes and cancer etc.have been becoming the main diseases of human beings.The causes of these diseases are complex,but there is a co-relationship between the lipid peroxidation and metabolic disorders which are caused by the excessive free radicals.Therefore,in order to scavenge the excessive free radicals antioxidants should be properly added to the body,which will have a beneficial effect on the body.Tea is a healthy drink,which has many efficacies such as clearing heat and removing toxicit,refreshing,eliminating the fire-evil.Iron is widespread in the human body,animals and plants as well as food and drugs.Iron is closely related to human life,which is very important for human health,but excessive intaking will produce toxic to the body,causing potential harm.Therefore,establishing convenient,quick,sensitive,and reliable methods for the detection of antioxidant capacity of tea and the content of iron in environmental water samples will be meaningful to the control of environmental pollution and the health of human beings.Spectrophotometry method is an attractive and powerful detection technique owing to its analytical advantages such as low detection limit,very high sensitivity,wide linear dynamic range,fast response and simple equipment.At the same time,sequential injection analysis(SIA)was developed as a branch of sampling means of FIA or second generation FIA with the advantages of high degree of automation,low consumption and good reproducibility.When spectrophotometry detection was coupled with SIA analysis,its features were reserved,and the shortcomings such as inconvenience of reaction process control and poor repeatability caused by fast reaction,were overcome.Combination spectrophotometry with SIA remarkably improved the repeatability,accuracy and analytical frequency of the analytical method.In this dissertation,the sequential injection coupled with spectrophotome-try detection technique was proposed and applied to the determination of antioxidant capacity of tea and the content of iron in environmental water samples,satisfactory results were obtained.The concept,classification,mechanism and application in food of antioxidants were introduced in the first chapter of the dissertation and a simple description on the classification,composition of tea were gave.The analytical methods included high performance liquid chromatography(HPLC),near-infrared spectrometry(NIR),chemiluminescence(CL),electron spin resonance(ESR),capillary electrophoresis(CEP)and spectrophotometry analysis;the dissertation described in detail the latest progress of determining antioxidant activity of tea.In addition,the purpose and significance of the topic was introduced briefly.A sequential injection coupled with spectrophotometry in determination of antioxidant capacity of tea were described in the second chapter of the dissertation.Under the acidic condition,a trivalent ferric-tripyridyltriazine complex is reduced to the ferrous form,an intense blue color with an absorption maximum at 597 nm.In case of an excess of Fe3+,the amount of blue material can reflect the reduction ability of the sample.FeSO4(mmol/L)concentration is obtained in the standard curve according to the relative absorbance value after the reaction,which is defined as total antioxidant capacity of the samples.The absorbance intensity was proportional to the concentration of Fe2+ in the range of 5.000×10?3-2.400×10-1 mmol/L.The method provided a limit of detection of only 3.200×10-4 mmol/L(3?/K).The relative standard deviation for eleven repeated measurements for 0.100 mmol/L Fe2+ was 0.43%.The sampling frequency was 36 samples per hour.The method was applied to determining antioxidant activity of tea with the recoveries in 88.2%?110.0%.The factors affecting FRAP value of tea was discussed in this chapter,and three kinds of tea antioxidant capacity was compared.A sequential injection coupled with spectrophotometry in determination of iron in water samples were described in the third chapter of the dissertation.Under the acidic condition,Fe(?)with 1,10-phenanthroline generate an orange complex(C12H8N2)3Fe]2+ with an absorp-tion maximum at 511 nm,which can determine the iron(?)content by this principle.When the total iron content of the sample was measured,hydroxylamine hydrochloride must be added to reduce Fe(?)to Fe(?)before the color.The absorbance intensitywas proportional to the concentration of Fe(?)in the range of 0.200?26.000 mg/L,with a correlation coefficient of 0.9995.The relative standard deviation for eleven repeated measurements for 12.000 mg/L Fe(II)was 0.66%.The sampling frequency was 37 samples per hour.The method provided a limit of detection of only 0.160 mg/L(3?/K).The method was applied to the determination of Fe(II)and total iron in environmental waters with the recoveries in 86.2%?109.8%and 92.5%?107.5%,respectively.In the last chapter,a summary for the characteristic of sequential injection coupled with spectrophotometry detection technique was described.