We have fabricated an integrated flow cell as a total microanalysis system (microTAS). This flow cell (size, 15 x 20 mm; total inner volume, 12.2 microL) was designed for a rational analyzing system of lactate determination for serum. This cell was made by micromachining techniques and consisted of two hollows of a lactate oxidase (LOD) reactor and a mixing cell, a spiral groove, and three penetrated holes. To form the reactor and capillary, these patterns, etched on a silicon wafer, were attached to a glass plate by the anodic bonding method. A photodiode was put under part of the spiral capillary. The compactly accumulated devices were integrated into a flow injection analysis (FIA) system. In the flow cell, lactate was catalyzed to pyruvate and hydrogen peroxide at the LOD reactor; subsequently, hydrogen peroxide reacted with the luminol-ferricyanic reagent at the mixing cell. The resulting chemiluminescent light was detected by the photodiode. Using the miniaturized flow cell, the sample volume for one measurement was greatly reduced to 0.2 microL. The response to lactate was obtained within 30 s and was linear between 0.5 and 5.0 mM (4.5 and 45 mg/dL) lactate with excellent correlative variances of 3.2% (average of three measurements at 5.0 mM). For practical application, the lactate concentration in control human serum was determined using this system. The results showed a good correlation coefficient (r = 0.979) with the results obtained by the spectrophotometric reference method. No difference in sera (normal or pathological) was found. Consequently, this integrated flow cell shows potential as a clinical device for lactate determination in serum. In this article, the effect of the design on the chemiluminescent FIA system is also described.
The electrocatalytic activity of a glassy carbon electrode with regard to the oxidation of ammonium carbamate increased with the electrolysis time because of the electrochemical modification of the electrode surface. From X-ray photoelectron spectroscopy data, it was found that a carbon-nitrogen bond was newly formed due to the electrode oxidation of carbamic acid at
+1.0V
vs
Ag∕AgCl
. Redox waves of catechol bound to amino group were observed at
+0.05V
vs
Ag∕AgCl
when cyclic voltammetry of catechol was carried out by using a glassy carbon electrode pre-electrolyzed in ammonium carbamate solution. This indicates that catechol can be attached to the electrolyzed surface by the reaction of the amino group bound to the pre-electrolyzed electrode surface and 1,2-benzoquinone formed by electrode oxidation. This result supports the concept that an amino group can be introduced by electrolysis in which ammonium carbamate is used as the electrolyte. The electrochemical introduction of the amino group may have occurred due to the decomposition of carbamaic acid attached to the carbon electrode surface.
Photoresists have been widely used as patterning materials for electronic devices such as displays and semiconductors. Understanding pattern formation mechanisms is essential for the efficient development of resist materials. In particular, the dissolution mechanism of resist materials is an important process in pattern formation. In this study, the dissolution mechanisms of negative-type resists for display manufacture were investigated using a quartz crystal microbalance (QCM) method. The changes in frequency during development were measured for polymer and resist films. The observed major trend was as follows. The development type changed from an insoluble state to a peeling type and a dissolution type with Case II diffusion with an increase in the acid value of the polymers. The characteristics of the dissolution with Case II diffusion are the formation of a transient swelling layer (dissolution front) and steady-state front motion (linear weight loss). For the dissolution with Case II diffusion, the dissolution time and the original thickness of the transient swelling layer decreased with an increase in the acid value of the polymers.
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