No abstract

Fish freshness was assessed using capillary electrophoresis and an immobilized enzyme procedure to monitor degradation of inosine-Smonophosphate (IMP), inosine (HxR) and hypoxanthine (I-Ix). The enzymatic method used an amperometric probe at + 0.7 V (platinum vs silver/silver chloride) with immobilized xanthine oxidase, catalase, nucleoside phosphorylase, and nucleotidase for converting I-Ix, HxR or IMP to uric acid. Capillary electrophoresis resolved IMP, inosine and Hx by migration rates resulting from an applied electric field (416 V/cm, 50 p,A). Components were detected at 250 nm. The H ratio of Hx/[IMP + HxR + Hx] and simplified K value of [HxR + Hx]/ [IMP + HxR + I-Ix] were determined in cod, salmon and trout stored on ice (WC) and at 20°C. The two procedures agreed and for all species H ratio and K values increased with storage time.

The isothermal permeation of oxygen through CaO-ZrO~ was studied at 960~176 and oxygen pressures P'o2 of 10 -:' to 1 atm on one side of the permeation cell and P"o~ of 10-~-10 -4 arm on the other. In the steady state, the permeating flux was directly proportional to (p,o.,n _ p,,o.,,,,), where n varied from 2.5 to 4.0. The value of n depended on the microstructure of the sample. For sample~ withou~ micropores, a value of n = 4 was found. These samples also contained a second phase whose composition depended on the nature and extent of impurities. For samples with nonconnected micropores, n varied from 3.6 to 2.5, depending on the thickness, and the results were consistent with a mechanism in which permeation is limited partly by diffusion within the solid and partly by a surface reaction. Both the bulk and surface processes have activation energies of about 200 kJ-mol-'.

Capillary electrophoresis has been applied to quantitate nucleotide degradation in fish tissues, to provide a basis for determining the K value, an indicator of fish freshness. The three major compounds, inosine monophosphate (IMP), inosine (HxR), and hypoxanthine (Hx) were distinctively separated at 416 V/cm applied potential, 100 mM CAPS buffer, pH 11. There was a good correlation between the peak area and the nucleotide concentration. By using a short distance (22 cm) from the sample entrance to the detector, the identification and determination of these compounds in each sample were completed within 15 min. The results obtained correlated very well with those obtained by enzymatic assays. The capillary was completely regenerated with 1 N NaOH, to dissociate all bound materials from the capillary wall, mainly cations in the fish extract. This provided the same silica surface for repeated runs, resulting in reproducible electropherograms.