What are the methods for the determination of heavy metals?

The detection methods for the limits of heavy metal elements in food include photometric method, turbidimetric method, spot comparison method, chromatographic method, spectrometric method, electrochemical analysis method, neutron activation analysis and so on. The relevant national standards all specify in detail the methods for determining the content of heavy metal elements in food. Listed below are the national standard testing methods for lead, cadmium, mercury and arsenic in food.　　

(1) The common detection methods for lead in food include: graphite furnace atomic absorption spectrometry, with a detection limit of 5 μg/kg; flame atomic absorption spectrometry, with a detection limit of 0.1 mg/kg; single scanning polarography, with a detection limit of 0.085 mg/kg; dithizone photometry, with a detection limit of 0.25 mg/kg; hydride atomic fluorescence spectrometry, with a detection limit of 5 μg /kg.　　

(2) The common detection methods for cadmium in food include: Graphite Furnace Atomic Absorption Spectrometry (GFAAS), with a detection limit of 0.1 μg/kg; Flame Atomic Absorption Spectrometry (FAAS), with a detection limit of 5 μg/kg; Photometric Method (PVP), with a detection limit of 50 μg/kg; and Atomic Fluorescence Method (AFM), with a detection limit of 1.2 μg/kg.　　

(3) The common detection methods for total mercury in food include: atomic fluorescence spectrometry, with a detection limit of 0.15 μg/kg; cold atomic absorption spectrometry, with a detection limit of 0.4 μg/kg (pressure digestion) or 10 μg/kg (other digestion methods); and disulfide hydrazide photometric method, with a detection limit of 25 μg/kg. Methylmercury is often analyzed by acid extraction of mercaptan cotton adsorption separation, followed by gas chromatography or cold atomic absorption spectrometry for determination.　　

(4) The common detection methods for total arsenic in food are: hydride atomic fluorescence spectrometry, the detection limit is 0.01 mg/kg; silver salt method, the detection limit is 0.2 mg/kg; arsenic spot method, the detection limit is 0.25 mg/kg; borohydride reduction photometry, the detection limit is 0.05 mg/kg.