| After the concept of micro total analysis system (uTAS) was introduced by Manz et al. in 1990, the field ofμTAS is growing rapidly. Because miniaturization is currently considered as one of the most important trends in the development of analytical instrumentation, the ultimate purpose ofμTAS is the integration of the entire analytical process on a micro-device. The micro-flow injection system on the chip is part of theμTAS and also has many advantages.The dissertation is made up of two sections. One is the review ofμTAS and micro-flow injection system on the chip. Another is the research work. In the first part of the research work, the micro-flow injection systems which are used for food analysis and environment analysis are introduced. Different sampling mode, including double-T sampling mode, micro-valve sampling mode and discrete microdroplet sampling mode, is used. With the sampling modes, the reagent consumption is reduced and the sensitivity is improved. In the second part, combining with the solid phase extraction technique, a chemiluminescence (CL) micro-flow system is presented for determination ofβ-lactam antibiotics in milk. In the last part of the research work, microdialysis sampling technique was used on the micro-flow injection system for the determination of glucose and Cr(III) metabolism in blood.1. Investigation on the chemiluminescence micro-flow injection analysis on a chip(1) Determination of benzoyl peroxide in flourBenzoyl peroxide(BP) is a common additive in flour because of its bleaching and sanitizing properties, but excessive benzoyl peroxide in flour could induce allergic reactions, weak cancer causing, Vitamin E and nutrients destruction. A rapid and sensitive chemiluminescence microfluidic chip fabricated in polymethyl methacrylate for determination of benzoyl peroxide in flour is described. The width of the microchannel was 200 urn and the depth was 100μm in the chip (50×40×5 mm). The total length of the microchannel was 67 mm with the detection area of 5×5 mm2. Benzoyl peroxide can directly oxidize luminol to produce chemiluminescence. Two injectors of double-tee injector and microvalve injector were used. The sampling volume was 0.16μL for the double-tee injector and 0.25μL for the microvalve injector. The linear range of the benzoyl peroxide concentration was 8×10-7-1×10-4 g mL-1. The detection limit was 4×10-7 g mL-1 and the R.S.D for eight times is 3.06% for the double-tee injector and 2.41% for the microvalve injector. The proposed method has been successfully applied to the determination of benzoyl peroxide in flour.(2) Determination of hypochlorite in tap waterA micro-flow injection chemiluminescence detection system fabricated in Polymethyl methacrylate (PMMA) (50mm×40mm×5mm) for determination of hypochlorite in tap water is described, based on the direct chemiluminescence reaction of hypochlorite and luminol. The microchannel on the micro-flow injection chemiluminescence detection system are made by laser ablation (200μm width, 150μm depth) and the sampling volume was about 0.3μL with double-tee mode. The linear range of the hypochlorite concentration was 3.0×10-7-1.0×10-4g/mL. The detection limit is 1.4×10-7g/mlL and the R.S.D for 11 times is 4.5%. The system is easy, fast (sample throughput 368h-1) and reduces reagent consumption. The proposed method has been successfully applied to the determination of hypochlorite in tap water.(3) Rapid determination of chemical oxygen demand in waterChemical oxygen demand (COD) is an important parameter for water monitoring because it can represent the organic contaminants in water. A fast, continuous and automatic analysis method for COD determination was needed. A chemiluminescence (CL) micro-flow system for rapid determination of chemical oxygen demand (COD) in water at room temperature is proposed in this paper. In this system, potassium dichromate is reduced to Cr3+ in 2 mol L-1 H2SO4 during chemical oxidation of COD-substances in sample and Cr3+ can be measured by the luminol-H2O2 CL system. The polymethyl methacrylate micro-flow chip with discrete microdroplet sampling was used here. Effects for COD determination (such as pH, concentrations, the channel length, and interference) were investigated. The linear range for COD determination was 0.27-10 g L-1 and the detection limit was 100 mg L-1. The proposed method has been successfully applied to the determination of COD in wastewater samples. The datas obtained by the present method were fairly in good agreement with those obtained by the titrimetric method.(4) Simultaneous determination of Cr (III) and Cr (VI) in waterA sensitive method for the simultaneous determination of chromium (III) (Cr3+) and chromium (VI) (Cr2O72-) using micro-flow chemiluminescence system was developed. The chemiluminescence detection was based on the catalytic effect of Cr (III) on the chemiluminescence reaction of luminol and hydrogen peroxide. Cr (VI) was on-line reduced to Cr (III) with hydrogen peroxide, and then was detected. The polymethyl methacrylate (PMMA) micro-flow system with three plates was used to realize this procedure. The micro-flow system used the discrete sampling with microdroplet, which can be formed at the tip of the capillary with the sampling volume of 5μL. The width of the microchannel was 200μm and the depth was 100μm. The linear ranges were 5×10-8-1×10-5mol L-1 for chromium(III) and 1×10-7-1×10-5mol L-1 for chromium(VI). The detection limits were 2×10-8 mol L-1 for chromium (III) and 4×10-8mol L-1 for chromium (VI). The proposed method has been successfully applied to the simultaneous determination for chromium (III) and chromium (VI) in water samples.2. Investigation on the chemiluminescence micro-flow injection analysis on a chip with on-line solid phase extraction(5) Determination ofβ-Lactam antibiotics in milkβ-Lactam antibiotics are widely used in the treatment of lactating dairy cattle for several infections. Antibiotic residues in milk, besides inhibiting start of cultures in the production of milk products, can provoke allergic reactions in some hypersensitive individuals. On-line introducing in SPE separation technique for interfering element removal is undoubtedly an ideal choice for interference elimination in CL analysis. In this paper, a chemiluminescence (CL) micro-flow system combined with on-line solid phase extraction (SPE) is presented for determination ofβ-lactam antibiotics (penicillin, cefradine, cefadroxil, cefalexin) in milk. It is based on the enhancement effect ofβ-lactam antibiotics on the luminol-K3Fe(CN)6 CL system. The micro-flow system was fabricated from two polymethyl methacrylate (PMMA) plates (50×40×5mm) with the microchannels of 200μm wide and 150 urn deep. C18-modified silica gel was packed into the microchannel (length: 10mm; wide: 1mm; depth: 500μm) to serve as SPE device. Extraction and preconcentration of the analytes were carried out using on-line SPE micro-flow system and the selectivity of CL detection was improved. The detection limits were 0.5μg mL-1 of penicillin, 0.04μg mL-1 of cefradine, 0.08μg mL"1 of cefadroxil and 0.1 ug mL"1 of cefalexin. The proposed method was also applied to analyzing theβ-lactam antibiotics in milk. Experimental results were in good agreement with those obtained by high performance liquid chromatography (HPLC) method with UV detection.3. Investigation on the chemiluminescence micro-flow injection analysis on a chip by microdialysis sampling(6) Determination of glucose in vivoA micro-flow chemiluminescence (CL) system in vivo for glucose determination by the on-line microdialysis sampling is described in this paper. The micro-flow CL system uses discrete sample droplets, which formed at the tip of the capillary with the sampling volume of 4.5μL. The sol-gel method is introduced to co-immobilize horseradish peroxidase (HRP) and glucose oxidase (GOD) on the inside surface of the micro-flow cell which was fabricated in polymethyl methacrylate (PMMA). The CL detection involved enzymatic oxidation of glucose to D-gluconic acid and H2O2, then H2O2 oxidizing luminol to produce CL in presence of HRP. The microdialysis probe was utilized for sampling in the rabbit blood; the sample throughput was 20 h-1 . The glucose level in blood of the rabbit was on-line monitored with good results.(7) On-line monitoring of chromium metabolism in vivoA micro-flow injection chemiluminescence system based on the Cr (III)-luminol-hydrogen peroxide chemiluminescence system for in vivo on-line monitoring of chromium (III) metabolism in blood by microdialysis sampling is described in this paper. It was fabricated in polymethyl methacrylate(PMMA) of two plates and the separation part of anion exchange resin was also integrated on the micro-flow system. The width of the microchannel was 200μm and the depth was 100μm on the plate(50×40×5mm). A microdialysis probe, implanted in the vein of rabbit, was perfused with perfusate at a flow rate of 5μL min-1. The dialysate sample volume was about 0.4μL. The metabolism of the chromium (III) in the blood of the rabbit was monitored after administration of the chromium (III) to demonstrate the favorable resolution and reliability of the system for in vivo on-line monitoring.
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