A compactly integrated flow cell with a chemiluminescent FIA system for determining lactate concentration in serum

We have fabricated an integrated now cell as a total microanalysis system ( mu TAS). This flow cell (size, 15 x 20 mm; total inner volume, 12.2 muL) wa s designed for a rational analyzing system of lactate determination for ser um. This cell was made by micromachining techniques and consisted of two ho llows of a lactate oxidase (LOD) reactor and a mixing cell, a spiral groove , and three penetrated holes. To form the reactor and capillary, these patt erns, etched on a silicon wafer, were attached to a glass plate by the anod ic bonding method. A photodiode was put under part of the spiral capillary. The compactly accumulated devices were integrated into a now injection ana lysis (FIA) system. In the now cell, lactate was catalyzed to pyruvate and hydrogen peroxide at the LOD reactor; subsequently, hydrogen peroxide react ed with the luminol-ferricyanic reagent at the mixing cell. The resulting c hemiluminescent light was detected by the photodiode. Using the miniaturize d now cell, the sample volume for one measurement was greatly reduced to 0. 2 muL. The response to lactate was obtained within 30s and was linear betwe en 0.5 and 5.0 mM (4.5 and 45 mg/dL) lactate with excellent correlative var iances of 3.2% (average of three measurements at 5.0 mM), For practical app lication, the lactate concentration in control human serum was determined u sing 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, thi s integrated now cell shows potential as a clinical device for lactate dete rmination in serum. In this article, the effect of the design on the chemil uminescent FIA system is also described.