Thread based analytical device as an analytical platform with mobile phone has been developed as green chemical analysis for the assay of anionic surfactant. The platform involves microfluidic behavior. The thread composing a bunch of cotton fibers could serve as channel that allows anionic surfactant to move along. The part of the thread containing anionic surfactant could be seen blue when threated with methylene blue while the part without anionic surfactant showed no blue. The platform could be then photo taken. A plot of log value of concentration of anionic surfactant versus the move distance along the thread exhibits linear: y = 129x+ 371; r2 = 0.999 where x being log (SDS concentration) and y being distance.
We report a new flow injection analysis method utilizing an online photochemical reactor for deoxyribose, which is oxidized in the reactor to produce oxalate and other unidentified compounds that reduce [Ru(III)(bpy)3]3+ with chemiluminescence. Deoxyribose injected to dilute HNO3 as a carrier was delivered to a reaction coil, which was then irradiated with ultra-violet light to promote the oxidation by HNO3. The process parameters, such as the ultra-violet irradiation time and concentrations of HNO3 and [Ru(III)(bpy)3]3+, were optimized, resulting in the detection limit of ca. 20 pmol. The chemiluminescences of ribose, ATP, deoxyadenosine monophosphate, and DNA from salmon sperm by this method were also observed.
Sequential injection analysis (SIA) protocols for the determination of phosphorus and mineral iron (Fe) in the Lagos Lagoon sediment were developed by optimizing some existing standard methods. Sandwiched sample was found to offer higher sensitivity than a 2-zone stack for P SIA. The injection volumes of sample and reagent for P analysis were 40 µL and 20 µL (split into two 10-µL zones) respectively while 150 µL of sample and 10 µL of reagent were injected in Fe analysis. The sampling rates were 31 h-1 and 75 h-1 for P and Fe SIA protocols respectively. Quantitative digestion of total P was achieved by a sediment-to-persulfate ratio of 1:3 by mass in 2.0 mL of 0.3 M NaOH. Average recovery of bioavailable P in matrix samples was 91.7 % and average recoveries of total P were 111.5 % and 96.6 % in matrix samples and blanks respectively. Average recovery of mineral iron in matrix samples was 94.3 % while average recovery in blanks was 97.4 %. The method detection limits were 1.4 mg P kg-1 and 2.6 mg P kg-1 for bioavailable-P and total-P methods respectively while the method detection limit for mineral iron method was 0.44 mg Fe kg-1. The combination of neutralization and dilution of bicarbonate extract prevented CO2 interference during SI absorbance scanning. The performance of these methods indicated their suitability for sediment P and Fe monitoring of the Lagos Lagoon system.
A method for preparation of a surface plasmon resonance (SPR) sensor chip with 8-stripe pattern for multiplex immunoassay, where several kinds of antibodies can be immobilized, is proposed in this paper. For immobilization of two types of antibody, anti-IgA and anti-IgG antibodies on the sensor chip at 8-stripe pattern alternatively, a flow generated by the centrifugal force was used for introducing the antibody solutions separately into a microchip with 8-channel on the 8-stripe patterned sensor chip. The resulting sensor chip, on which the anti-IgA antibody and anti-IgG antibody were immobilized alternatively, was attached to a flow cell prepared from an acrylic with a single flow channel. Mixed solutions of IgA and IgG at different concentrations were injected into a carrier stream of a pH buffer solution at 7.4, and SPR sensor signals for IgA and IgG were detected separately from the SPR sensor chip with stripes immobilized with corresponding antibodies. As a result, calibration curves for IgA and IgG, which fit to those calculated from the Langmuir adsorption isotherm, were obtained. The detection limit of the SPR sensor was ca. 5 ppm.
In this tutorial review, the principle of amplitude modulated multiplexed flow analysis, a continuous flow analysis coupled with fast Fourier transform, FFT, is described. The flow rates of sample solutions are respectively varied at different frequencies. The solutions are merged, and then air bubbles are introduced to the merged stream so as to limit the axial dispersion of analytes that causes amplitude damping. The stream is led to a detector with no physical deaeration. Air signals are removed by signal processing, and the resulting liquid signals are analyzed by FFT. The analytes in the samples are respectively determined from the amplitudes of the corresponding wave components. Temporal profile of amplitudes can be obtained in real-time by moving the window for FFT with time.