微波–干灰化混合消解和原子荧光光度法测定鱼粉中总砷

Determination of total arsenic in fishmeal using Microwave-Dry ashing mixed digestion coupling with atomic fluorescence spectrophotometry

关键词:  微波–干灰化混合消解  原子荧光光度法  总砷  鱼粉

Key words:  Microwave-dry ashing mixed digestion  Atomic fluorescence spectrophotometry  Total arsenic  Fishmeal

摘要:

采用微波–干灰化混合消解法进行前处理，原子荧光光度法测定鱼粉中的总砷含量。结果显示，样品经微波消解、干灰化、原子荧光分光光度法分析，加标回收率为96.8%~103.6%，相对标准偏差为2.4%，检出限为0.1 μg/L；采用CNAS能力验证鱼粉样品，微波–干灰化混合消解法总砷测定结果与中位值一致。研究表明，微波–干灰化混合消解法能减少前处理过程中砷(As)因高温或消解不完全导致的损失，使鱼粉中的各种形态的As完全转化为无机砷离子，方法重现性好、准确可靠，是测定鱼粉中的总砷含量理想的前处理方法，也可以用于砷形态比较复杂的食品、饲料等样品中总砷的测定。

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.