Related Experiment Video
Updated: Jan 24, 2026

Highly-Multiplexed Tissue Imaging with Raman Dyes
Published on: April 21, 2022
Multiresidue determination of triarylmethane and phenothiazine dyes in fish tissues by LC-MS/MS
Jonathan A Tarbin1, Danny Chan, George Stubbings
1Central Science Laboratory, Sand Hutton, York YO41 1LZ, UK. j.tarbin@csl.gov.uk
Abstract:
The occurrence of residues of malachite green and its leuco-metabolite in tissues of farmed fish for human consumption have long been of concern and there is extensive literature on methods of analysis and surveillance for these compounds. Recently, concern has been expressed that the use of other related compounds in place of malachite green may go undetected. This paper describes a new method for extending the range of triarylmethane and related phenothiazine dyes that can be detected in fish. In this procedure 13 parent compounds are monitored, with any potential leuco-forms being oxidized back to the parent prior to determination. The method utilizes a buffer-acetonitrile extraction followed by liquid-liquid extraction. Oxidant is added and the extracts further purified by cation exchange chromatography. Final determination is carried out using LC-MS/MS. The method has been validated to the standards of Commission Decision 2002/657/EC.
Related Concept Videos
Determination
Osmoregulation in Fishes
FISH - Fluorescent In-situ Hybridization
Determining Order of Reaction
Determining the pH of Salt Solutions
Rate-Determining Steps
In a multistep reaction mechanism, one of the elementary steps progresses significantly slower than the others. This slowest step is called the rate-limiting step (or rate-determining step). A reaction cannot proceed faster than its slowest step, and hence, the rate-determining step limits the overall reaction rate.
The concept of rate-determining step can be understood from the analogy of a 4-lane freeway with a short-stretch of traffic-bottleneck caused due to...

