A Study On Arsenic Speciation And Its Application To Safety Evaluation Of Food

Arsenic has a century-long reputation of being poisonous. For example,the inorganic arsenic compounds, such as arsenite and arsenate, are toxic andcarcinogenic. Ingestion of inorganic arsenic may cause cancer of the skin,bladder, kidney, lungs, and liver. However, the toxicity of arsenic is greatlydependent on its chemical form. In fact, the major forms in most marineorganisms, which are organic arsenic compounds such as arsenobetaine (AsB)and arsenosugars, are considered to be nontoxic. For this reason, thedetermination of the total amount of arsenic in a sample is not sufficient toassess the risk from eating seafood, and speciation analysis is necessary. In present dissertation, experimental studies of the arsenic speciation byusing high performance liquid chromatography (HPLC) coupled hydridegeneration atomic absorption spectrometry (HGAAS) were carried out. Themain achievements obtained in this research are: ⑴ An efficient interfacebetween HPLC and AAS was designed, which hold an UV-digestion part, ahydride generation system and a gas-liquid separator in a small box. It wasprovided with some functions such as on-line digestion and hydridegeneration for arsenic compounds, which discussed several importantpractical aspects for on-line coupling of HPLC to AAS. And it had twoadvantages: first, the broaden of peak has been effectively solved; second, thegoal of miniaturization of instrument was achieved. ⑵ Based on theinterface technology, the standard operation procedure (SOP) of speciation ofAs(III), As(V), monomethylarsonic acid (MMA) and dimethylarsinic acid(DMA) by using HPLC-HGAAS was developed. In order to obtain themethod performance characteristics, the following parameters weredetermined: Resolution factor, Limit of detection, Repeatability and Linearityrange. ⑶Verification of the method by another technique was performed byanalyzing spiked samples both with HPLC-HGAAS and HPLC-ICP-MS. IIThe results showed HPLC-HGAAS with low cost, easy operation and highperformance was successfully applied to the speciation analysis of arsenic. In the second part of present dissertation, thirty different types ofChinese edible seafood, including brown algae, red algae, ?sh, crab, shrimp,mussels, oysters, and clams, which are very popular foodstuffs in the Chinesekitchen, were examined for their total content of As as well as its differentspecies. The arsenic species in seafood extracts were determined byhyphenated technique. The results showed high levels of arsenic were foundin seafood, but the major share of arsenic components in seafood wereorganic arsenic with a low toxicity, we can conclude that arsenic in seafooddoes not pose any risk to human health. The study was carried out toinvestigate the chemical changes of these organoarsenic compounds inPorphyra products during the cooking period and human ingestion. Weobserved that the arsenosugars were stable during a series of familiar cookingmethods, such as boiling, steaming, microwaving and frying. However, whenthe sample was baked in a temperature higher than 200 °C, the arsenosugarmay undergo changed during heating, being transformed into another, moretoxic species, such as arsenate and arsenite. The metabolites of thesearsenosugars in human urine after ingestion of seaweed were also studied.The results are helpful not only in the evaluation of seafood safety but also inunderstanding the metabolism and the possible adverse health effects ofarsenosugars in humans.