Flow Injection Determination of Lactate Using Immobilized Lactate Dehydrogenase Enzyme with Tris(2,2′-Bipyridyl)Ruthenium(III) Chemiluminescence Detection

Amperometric L-Lactate Biosensor Based upon a Gold Nanoparticles/Reduced Graphene Oxide/Polyallylamine Hydrochloride Modified Screen-Printed Graphite Electrode

This work describes a novel L-lactate biosensor based on the immobilization of L-lactate dehydrogenase enzyme on the screen-printed electrode modified with a ternary composite based on gold nanoparticles, electrochemically-reduced graphene oxide, and poly (allylamine hydrochloride). The enzyme was stabilized by crosslinking with glutaraldehyde. Applied working potential, pH and NAD+ concentration were optimized. The biosensor reports a specific sensitivity of 1.08 µA/mM·cm2 in a range up to 3 mM L-lactic acid with a detection limit of 1 µM. The operational and long-term stability as well as good selectivity allowed the L-lactic acid measurement in dairy products and wine samples.

A novel immobilization fluorescence capillary analysis method and its applications

Fluorescence capillary analysis (FCA) realizes trace-level analysis of micro-volume samples; it is easy to operate, extremely low in analytical cost and can significantly lessen environmental pollution from analytical chemistry waste. FCA has the characteristics of green analytical chemistry and has been applied in clinical, biochemical, pharmaceutical, food safety and other fields. FCA basically involves a micro-volume glass capillary, a capillary holder and an ordinary fluorescence detector. The capillary is not only a container for chemical reaction and detection but also functions as a carrier to immobilize enzymes, gene probes or reagents; it can be used repeatedly or can be disposable. In analysis, the capillary which is modified with functional reagents sucks in a measured liquid for the reaction and is then inserted into the holder within the fluorescent detector for measurement. The immobilized FCA method has been successfully used in the determination of reduced coenzyme I, ethanol in liqueur, lactic acid in dairy products, pyruvic acid and glucose in serum, trace-level sulfated bile acid in urine, the ratio of pyruvic/lactic acid in serum, and pyruvic acid in cells as well as in DNA end-labeling and dyeing methods. Further, FCA can also be extended to capillary arrays to complete multipurpose simultaneous determinations and can be combined with mobile phones as fluorescence detectors for use in mobile health analytical technology. FCA will produce considerable social benefits in medicine, pharmacy, fermentation of food, environmental protection and other fields. Therefore, the relevant contents are presented in this tutorial review.