Inductively Coupled Plasma Atomic Emission Spectrometry with Internal Standards for Water-Soluble Silicon Determination in White Tea
[Objective]A method for determining the content of water-soluble silicon in white teas using inductively coupled plasma atomic emission spectrometry(ICP-AES)with internal standards was developed.[Method]The ICP-AES procedures were first optimized using the internal standards of iridium,indium,germanium,and silicon with 1.00,2.00,3.00,4.00,5.00,and 6.00 g sample weights in a boiling water bath for a 20,40,60,90,or 120 m extraction.White tea samples were ground,filtered through a 5.0 μm sieve,and oven-dried at 80oC for more than 4 h as a pretreatment prior to spiking the filtrate with the internal standards and making up to volume.Water-soluble silicon was determined by the optimized ICP-AES,and the results correlated to the standard curve.[Result]The linearity of the silicon measurement curve against iridium standard showed the highest correlation coefficient of greater than 0.9999 with a detection limit of 7.5µg·L-1,a relative standard deviation(RSD)of 1.53%,and a recovery rate on spiked standards of 99.4%-104.8%.On the 10 white tea specimens,including 4 Baimudan and 4 Shoumei stored for one,3,7,and 10 years,and 2 Paohuang Baimudan(Baimudan tea made of leaves from bushes not plucked for years)stored for one and 3 years,the content of water-soluble silicon in Shoumei increased with increasing storage age,while Baimudan of different ages remained relatively constant;and that in Paohuang Baimudan was significantly lower than those in the others.[Conclusion]The newly developed ICP-AES assay was precise and reliable in detecting water-soluble silicon in white teas.It was considered adequate for the determination.By unveiling the differences in the content,in-depth studies on the health effect of varied white teas and quality improvement for new products were significantly facilitaed.
Inductively coupled plasma atomic emission spectroscopyinternal standard methodwater-soluble siliconwhite tea
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