Application of direct-injection detector integrated with the multi-pumping flow system to chemiluminescence determination of the total polyphenol index

• A DID-CL-MPFS method for determination of the total polyphenol index is proposed.
• Direct-injection detector enables fast measurement of CL in stop-flow conditions.
• The method is based on the enhancement of manganese(IV)-based CL reaction.
• Ethanol was used as a ‘green’ alternative to formaldehyde enhancer.
• The method ensures minimal consumption of reagents and waste generation.

In this work, we present a novel chemiluminescence (CL) method based on direct-injection detector (DID) integrated with the multi-pumping flow system (MPFS) to chemiluminescence determination of the total polyphenol index. In this flow system, the sample and the reagents are injected directly into the cone-shaped detection cell placed in front of the photomultiplier window. Such construction of the detection chamber allows for fast measurement of the CL signal in stopped-flow conditions immediately after mixing the reagents. The proposed DID-CL-MPFS method is based on the chemiluminescence of nanocolloidal manganese(IV)-hexametaphosphate-ethanol system. The application of ethanol as a sensitizer, eliminated the use of carcinogenic formaldehyde. Under the optimized experimental conditions, the chemiluminescence intensities are proportional to the concentration of gallic acid in the range from 5 to 350 ng mL−1. The DID-CL-MPFS method offers a number of advantages, including low limit of detection (0.80 ng mL−1), high precision (RSD = 3.3%) and high sample throughput (144 samples h−1) as well as low consumption of reagents, energy and low waste generation. The proposed method has been successfully applied to determine the total polyphenol index (expressed as gallic acid equivalent) in a variety of plant-derived food samples (wine, tea, coffee, fruit and vegetable juices, herbs, spices).

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