Trích:
Nguyên văn bởi duongqua28
Mình đang làm trên máy IC ( sắc kí ion). Đang tối ưu quy trình phân tích polyphosphate. Chỉ tiêu này làm trong nước thì đơn giản, chỉ cần lọc và tiêm vào máy. Tuy nhiên khi phân tích polyphoste trong mẫu cá thì gặp khó khăn. Trong mẫu cá hàm lượng chất hữu cơ qua lớn, mình đã dùng chiết lỏng lỏng bằng hệ hexan và nước. Tuy nhiên không thể loại hết chất hữu cơ trong pha nước. Quyết định đem pha nước này tiếp tục qua cột C18 rồi lọc bằng đầu lọc 0.2 micro. Tuy nhiên hàm lượng chất hữu cơ còn rất nhiều, lọc không được. Mong thầy cô và bạn bè chỉ bảo. Hay có một quy trình nào khác cũng được. Cảm ơn
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Chào duongqua,
Đọc qua cái này đi nha. Mình thấy là dùng IC không ổn rồi đó!
Inorganic polyphosphates (di-, tri- and higher polyphosphates) can be used to treat fish, fish fillets and shrimps in order to improve their water-binding capacity. The practical relevance of this treatment is a significant gain of weight caused by the retention/uptake of water and natural juice into the fish tissues. This practice is legal; however, the use of phosphates has to be declared. The routine control testing of fish for the presence of polyphosphates, produced some results that were difficult to explain. One of the two analytical methods used determined low diphosphate concentrations in a number of untreated samples, while the other ion chromatography (IC) method did not detect them. This initiated a number of investigations: results showed that polyphosphates in fish and shrimps tissue undergo a rapid enzymatic degradation, producing the ubiquitous orthophosphate. This led to the conclusion that sensitive analytical methods are required in order to detect previous polyphosphate treatment of a sample. The polyphosphate concentrations detected by one of the analytical methods could not be explained by the degradation of endogenous high-energy nucleotides like ATP into diphosphate, but by a coeluting compound. Further investigations by LC-MS-MS proved that the substance responsible for the observed peak was inosine monophsosphate (IMP) and not as thought the inorganic diphosphate. The method producing the false-positive result was modified and both methods were ultimately able to detect polyphosphates well separated from natural nucleotides. Polyphosphates could no longer be detected (<0.5 mg kg-1) after modification of the analytical methodology. The relevance of these findings lies in the fact that similar analytical methods are employed in various control laboratories, which might lead to false interpretation of measurements.
( Analysis of polyphosphates in fish and shrimps tissues by two different ion chromatography methods: implications on false-negative and -positive findings.Food Additives and Contaminants 22 (11) 1073–1082)
Có thể liên hệ với tác giả nhận định này qua:
Official Food Control Authority of the Canton of Zurich (Kantonales Lab. Zurich), PO Box, CH-8030 Zurich, Switzerland. E-mail
anton.kaufmann@klzh.ch
Thân,
Teppi