Abstract:Fishmeal is an important animal protein feed that is rich in protein and vitamins and is a major raw material of animal feed. Arsenic is an essential element for animal growth but is also a cumulative toxic element. Arsenic poses a great threat to animals when its concentration exceeds a certain limit. Serious environmental pollution has caused an increase in the level of arsenic in the environment, and thus, the content of arsenic has increased in fish. This can directly affect the quality of fishmeal, with unfavorable effects on food safety. Therefore, it is crucial to accurately determine the content of total arsenic in feed stuffs. The accurate determination of total arsenic in samples depends on pre-treatment methods. At present, the major pre-treatment methods for arsenic include dry-ashing, wet digestion, and microwave digestion, but none of these methods can completely convert the speciation of arsenic to arsenic ion. Dry-ashing leads to the loss of arsenic due to high temperature and spatter. Wet digestion and microwave digestion do not convert complex forms of arsenic to arsenic ion because of temperature, acid type, and dosage. A novel method was established for the quantitative determination of total arsenic in fishmeal by atomic fluorescence spectrophotometry after microwave dry-ashing mixed digestion. Fishmeal was digested in a microwave, ashed, and the arsenic content was detected by atomic fluorescence spectrophotometry. Recovery was in the range 96.8%~103.6%, the relative standard deviation was 2.4%, and the detection limit was 0.1 μg/L. Results of China National Accreditation Service for Conformity Assessment proficiency testing were in accordance with the median. The results indicated that microwave dry-ashing mixed digestion can reduce the loss associated with the high-temperature of ashing and incomplete microwave digestion, and convert different forms arsenic into arsenic ion. This effective, sensitive, and reproducible method can be used to determine total arsenic levels in fishmeal and other complex samples containing arsenic forms.
