Solid phase extraction, hydrogen peroxide

Solid phase extraction, hydrogen peroxide determination, 635... 

Solid-phase extraction is routinely used to clean up extracts prior to quantitation (19,42,70, 80-82). Alternatively, endogenous fluorescent artifacts in food samples can be eliminated by oxidation with potassium permanganate/hydrogen peroxide/sodium metabisulphite. Benzyl alcohol has been used to extract riboflavin selectively without the coenzymes, permitting the determination of free riboflavin. 

LC combined with postcolumn chemiluminescence detection has also been applied to the determination of trace N-nitrosamines in groundwater The method combines solid-phase extraction (SPE) on to a mini-activated carbon column, followed by elution with acetone and concentration of the extracts by denitro-sation and fluorogenic derivatization. Peroxyoxalate chemiluminescence detection was carried out by using bis(2-nitrophenyl) oxalate and hydrogen peroxide as chemilumigenic reagents. The method provides N-nitrosamines detection at picomole per liter levels. 

The checkers observed the separation of a heavy, white precipitate presumed to be a borate salt during the addition of hydrogen peroxide. After the three-phase mixture had been stirred at room temperature for 3 hr, the liquid layers were decanted into a separatory funnel. The solid remaining in the flask was washed with two 75-mL portions of ether and these washings were used to extract the aqueous layer. 

The hydride generation ICP-mass spectrometric technique [75] had a sensitivity of 6.4 ng/g selenium in plant material and was applied to digests of corn, kale and rice. In the isotope dilution mass spectrometric technique [77], the samples were spiked with 76-selenium solution and digested on a heating block at 150 °C with a mixture of nitric acid and hydrogen peroxide. Solid-phase microextraction was used to extract selenium from plant material prior to the gas chromatographic techniques [76]. See also Sects. 7.34.1 and 7.34.2. 

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