Sample Pretreatment By In-situ Polymerized Solid Phase Extraction On Micro-Fluidic Chip

Miniaturized total analysis system ((TAS) is a developing new field of analytical chemistry recently. Its finally goal is that all process of analytical chemistry could be put into and carried out on microchip. Most researchers paid their attention on micro-mixers, micro-reactors and detection, while sample pretreatment process was somehow neglected, such as micro-separation and concentration on micro-fluidic chip. In this paper,the in-situ polymerized monolithic porous polymer which is thermally initiated within a glass micro-column was proposed to applied for solid phase extraction(SPE) and preconcentration. Integrating SPE micro-column and micro-fluidic chip together, a combination micro-fluidic chip with SPE micro-column was established. The capability of SPE micro-column was estimated by selected analytical methods. Analytical process, including perconcentration, mixing, reaction and detection, were realized on the combination micro-fluidic chip at last.In this paper,the factors of temperature, oxygen-free condition and polymerization reaction time were interpreted. Effects of the amount of each monomer on the SPE micro-column properties were discussed. SPE micro-column with anion-exchange sorbent was prepared in-situ at glass capillary. The structure image of polymers were observed by microscopy and scanning electron micrograph (SEM). Porogenic solvent mixture was of advantages in the process of forming porous structure polymers during its polymerization. Absorption charateristic of conventional SPE column was proved by catalytic-kinetic spectrophotometric determination of nitrite, which was a system of nitritre-potassium bromate -bromothymol bule. The results shown that absorption efficiency of the conventional SPE column was 65.1%, and enrichment efficient is 30.3 times. SPE micro-column still was of enrichment capacity, ie. enrichment efficient was 29.0 times. Furthermore, enrichment times could achieve 77.9 times with on-line sample treatment by SPE micro-column. All enrichment efficient for on-line process were obtained by UV determination. According to the different retention property of L—phenylalanine and L—Arginine in pH=9.60 solution, the selectivity of SPE micro-column was discussed by the amino acid-hydroxide-Luminol system. It was feasible to separate components with significantly properties on the self- designed combination micro-fluidic chip. For NaNO2—KI—Luminol, the framework of a micro-fluidic chip was designed. Sampling mode, velocity of flow, detection point of chemiluminescence were discussed. Effective plate number of SPE micro-column for NO2— was calculated. Breakthrough volumes of SPE micro-column for NO2—were systematically investigated by breakthrough curve and predicting methods.Sample of trace nitrite in food and water were concentrated on a combination micro-fluidic chip with SPE micro-column, and examined on-line by a system of NaNO2—KI—Luminol. The contents of nitrite in Luncheon meat and tap water were 14.63mg/kg and 0.052mg/kg respectively.