MQCA (3-methyl-quinoxaline-2-carboxylic acid) is a metabolite of N-(2-hydroxyethyl)-3-methyl-2-quinoxaline-carboxamide-1,4-dioxide (Olaquindox). Olaquindox is a broad spectrum antibiotic that is used in animal feed for growth promotion, to improve feed efficiency and to increase the rate of weight gain. In 1991, the Joint FAO/WHO Expert Committee on Food Additives (JECFA) recommended maximum residue limits (MRLs) of 30 and 5 µg/kg in liver and muscle tissues, respectively. In 1998, the European Commission (EC) banned the use of olaquindox in food animal production, together with four other feed additives. In 2005, it was banned for use as a veterinary drug by Chinese government regulatory agencies. 

The Kernel® MQCA ELISA Test Kit is a competitive enzyme immunoassay for the quantitative analysis of MQCA in chicken, duck and pork. The MQCA ELISA Test Kit is a competitive colorimetric ELISA assay. The plate wells are coated with anti-MQCA antibody. During analysis, sample is added along with the MQCA-horseradish peroxidase (MQCA-HRP) conjugate. If MQCA residue is present in the sample, it will compete for the MQCA antibody, thereby preventing the MQCA-HRP from binding to the antibody attached to the well. The resulting color intensity, after addition of the HRP substrate (TMB), has an inverse relationship with the concentration of MQCA residue in the sample.