| Formaldehyde is carcinogen and teratogen, the second in the list of toxic chemicals override controlled. Formaldehyde in food is comed from three aspects. The first one is that formaldehyde added in food for processing material. In the early beer processing, formaldehyde is added in processing to raise the stability. The second one is that formaldehyde is natural consisted in food. The third one is that formaldehyde is added in food by some unscrupulous traders for obtaining large profits. It damages consumers'health, cause the overproof content of formaldehyde in food.There is no determination of formaldehyde in food of GB methods at present in our country. Most current methods is setted by exit and entry inspection and quarantine bureau(CIQ) of some provincial city. At home and abroad, it is limited only for bits of food that the content of formaldehyde in food. For example, it is ruled that the amount of residue of formaldehyde in beer should be less than 2.0 mg/L in GB 2758-2005. It should be less than 0.9 mg/L that the amount of residue of formaldehyde in drinking water by the rule of WHO. It should be less than 25 mg/Kg ruled by CAC in cheese. And the content of formaldehyde should be less than 15 mg/Kg in food package material ruled by EU. In addition, there is no rule about the content of formaldehyde in food. Because of the large difference in different food, it couldn't judge that whether the content is overproof. So it should be strengthened to research the technology of formaldehyde detection in food, revision and perfect relevant technical standards. Perfecting and unifying the detection methods of formaldehyde in food in internationally, it could ensure the fodd safety and reduce international trade disputes.It is strict controlled in souce that the addition of formaldehyde at abroad. Most of document about formaldehyde determination is the detection of the content of formaldehyde in fabrics, toy and air. By contrast, because the law is no perfect, some unscrupulous traders add formaldehyde in food for better appearance and more storage time in our country. Thus it is so important to establish and perfect the determination of formaldehyde that preserves the food safety. There are many methods to dectect the content of formaldehyde, such as the mehods of acetylacetone, chormotropic, phheylhydrazine hydrochloride, phyloroglucinoe, PRA, AHMT, GC-MS, HPLC, IC and TLC. It is studied six commone methods in this page. The results are as follows:(1) Chromotropic acidThe standard curve of chromotropic acd is y=0.1651x-0.038, R2=0.9954. The linearity is fine. The linear range is 0.66 mg/Kg～5.50 mg/Kg, LOD is 0.22 mg/Kg. When the addition levels is 0.55 mg/Kg～2.20 mg/Kg, the covery is 75.5 %～108.6 %, RSD is 7.0 %～11.3 %. It only needs 6min water bath calefaction time, which is shorter than it is record in the document[1].(2) Phenylhydrazine hydrochlorideThe standard curve of phenylhydrazine hydrochloride is y=0.2134x-0.0469, R2=0.9982. The linearity is fine. The linear range is 0.22 mg/Kg～4.40 mg/Kg, LOD is 0.08 mg/Kg. When the addition levels is 0.55 mg/Kg～2.20 mg/Kg, the covery is 70.4 %～107.8 %, RSD is 7.6 %～11.4 %. There is a patent[2] in our country about the method of phenylhydrazine hydrochloride in our country. But the LOD is 2 mg/Kg,and the reaction time is 24 min, which is higher and longer than those in this page.(3) AcetylacetoneThe standard curve of acetylacetone is y=0.1063x-0.0555, R2=0.9979. The linearity is fine. The linear range is 0.55 mg/Kg～8.91 mg/Kg, LOD is 0.33 mg/Kg. When the addition levels is 0.55 mg/Kg～2.20 mg/Kg, the covery is 71.5 %～106.4 %, RSD is 7.5%～12.5%. The water bath calefaction time is 30min in the document[3], which is more longer than that in this page.(4) PhyloroglucinoeThe standard curve of phyloroglucinoe is y=0.021x-0.0064, R2=0.9929. The linearity is fine. The linear range is 0.99 mg/Kg～13.2 mg/Kg, LOD is 0.55 mg/Kg. This method is detecting the red compound produced by the reaction of formaldehyde phyloroglucinoe and NaOH. The red compound would fade quickly after emerge. It is not considered in the document[4], but it is done in this page. The determination would be hurt badly by temperature, so it couldn't be quantitative analysis. But it could be made to colour chart for simple qualitative analysis.(5) GC-MSThe standard curve of GC-MS is y=14514x+3926.12, R2=0.9996. The linearity is very good. LOD is 0.02μg/Kg. When the addition levels is 0.16 mg/Kg～1.35 mg/Kg, the covery is 76.6 %～104.8 %, RSD is 6.7 %～9.2 %. This method uses SIM mode for detecting. Compare to SCAN mode, it is the same in determination result. But the picture of SCAN is very complex. It is need more time to analyse. The picture of of SIM is more simpler and the sensitivity is higher than that of SCAN. Before using SIM mode, it should be sure the selected ion by SCAN mode first. In this page, the selected ions are 63, 79 and 210.(6) HPLCThe standard curve of HPLC is y=151.59x+32.838, R2=0.9992. The linearity is very good. LOD is 0.5 mg/Kg. When the addition levels is 0.5 mg/Kg～5.0 mg/Kg, the covery is 70.0 %～107.8 %, RSD is 5.7 %～13.4 %. DNPH is used for derivating agent in the docment[5]. When there is other aldehyde and ketone, they would participate in the reaction with DNPH. It would extend the analysis time, and require the gradient of mobile phase. So EAA is be used for derivating agent in this page.The best method in spectrophotometry is the method of pheylhydrazine. Though the reaction time is the longest one, but it needn't water bath calefaction. The operation is simple and quick. The linear range of the acetylacetone method is wide, and the reaction time is very short. Using H2SO4 for reaction medium, it has high requirement for operation in the method of chromotropic acid. The operation of phyloroglucinoe method is simple and quick too, but the determination would be hurt badly by temperature. In the two methods of chromatography, the sample preparation is similar. The derivating agent is DNPH in GC-MS and it is EAA in HPLC. Acetonitrile is additional in sample preaparation. Compared with chromatography, spectrophotometry is simple and quick in operation, and needn't complex instrument, but the covery and sensitivity is worse.Now our country has joined into WTO, the issue in this page could contribute to establish and perfect determination system of formaldehyde in food, raise the techonology lever in food safety, and ensure people's health. |
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