A Capillary Flow Directed Assembly Technique On The Surface Of Solid Supports And Its Applications In Biochemical And Pharmaceutical Analysis

Base on self-assembly phenomenon, the formation mechanisms of ring-like deposit were presented including evaporation induced capillary flow, 2-D bubbles, dried-hole and other hypotheses, and the current developments of the capillary flow directed self-ordered ring (SOR) technique in analytical science were described further. The drawbacks of the SOR technique were discussed based on the study of antibiotics, ease pain and probe drug as model analytes.The antibiotics in this paper include berberine (BB) and tetracycline (TC). In a medium of pH 3.95 (HAc-NaAc), berberine has very weak fluorescence, but when a small droplet of 0.50 l BB with the aid of poly(vinyl alcohol)-124(PVA-124) was dropped on dimethyl dichlorosilane (DMCS) pretreated hydrophobic glass slide, a typical fluorescent SOR with outer diameter less than 1.2 mm and ring belt width less than 19 m can be obtained and the solute on the ring belt has strong fluorescence. Data analysis for the digitally imaged SOR by using a CCD camera showed that the berberine molecules across the SOR diameter follow a Gaussian distribution, and the maximum fluorescent intensity (Imax) of BB was found to be proportional to BB content at the femtomole level. Linear response is observed in the range of 6.9-160.0 frnol (or 6.9~160.0 10-8M) when the droplet volume is 0.10 l, and the detection limit reaches 0.69 fmol (or 6.9 10-9 M) with 3-fold signal-to-noise ratio. With the proposed technique, the content in oral administration tablets and the average excretion rates of berberine through human urines after taking medicine could be satisfactorily monitored. Thus, the SOR analytical method of detecting femtomole level BB was established. In the process of the assay study, the established SOR model was modified in ordered to be more identical with the real situation and the quantitative equation of SOR was further supplemented and perfected in theory by more reasonable mathematics processes.The assay found that in the reaction medium of pH 4.58 (HAc-NaAc) containing poly (vinyl alcohol)-124, the SOR fluorescence intensity of BB can be quantitatively quenched by picric acid, and the outer diameter of 1.1 mm and the ring belt width of 19.2 (xm of BB-PC can be obtained by microwave heating. When 0.10 \ droplet of BB-PC complex was spotted on the hydrophobic-treated glass surface, picric acid in the range of 1.3~30.0xlO~14 mol(1.3~30.0xlO~ M) can be detected, and the detection limit can reach 1.3 fmol (or 1.3x10 M) with three times of signal to noise ratio. Compare with the fluorimetric method, the sensitivity of SOR technique enhanced 60 folds. With present method, the contents of picric acid in water samples and synthetic samples were determined with satisfactorily results.It is well-known that tetracycline has a strong fluorescence in basic medium with a characteristic Aex at 390 nm and Aem at 510 nm instead of weak fluorescence in acidic and neutral solutions. This paper describes a fluorescence microscopic method for determination of tetracycline in oral administration tablet and synthetic sample by SOR technique. In the presence of PVA-124, the droplet of tetracycline in the medium of hexahydropyridine can form a SOR on the surface of hydrophobic glass slides with the diameter of 1.14 mm and the ring belt width of 0.025 mm. By measuring the fluorescence intensity of ring belt, the quantification analysis of tetracycline is successfully achieved with the detection limit of 8.5 fmol when 0.20 [xl droplet was spotted. It has the advantages of lower background interfere and small amount of sample consumption.Although tetracycline has weak fluorescence in acid solution of pH 5.20 (Tris-HCl), increased fluorescence with wavelength of excitation (380 nm) and emission (498 nm) is obtained by the formation of highly fluorescent complex with A13+. In this paper, a fluorescence microscopic determination of trace amount of tetracycline is reported based on the aluminum-sensitized fluorescence effect of a SOR formed by a sessile droplet on glass slide support. Whe...