Generally the benefit of the liquid ready kits are that the formulations are ready to use. There is no preparation of vials involved. Also within the assay then there are less components to be pipetted into the cuvette, therefore less room for error.
Accreditation
This is important specific accredited method is required. Please see below for the method numbers.
K-ETOH = AOAC 2019.08
K-ETOHLQR = AOAC 2017.07
Sensitivity
The K-ETOH kit is more sensitive (LOD 0.093 mg/L) when compared to K-ETOHLQR (LOD 1.6 mg/L).
The advantage of this sensitivity is that it can detect very low levels of ethanol. However due to this sensitivity samples require high dilutions and the assay is sensitive to environmental ethanol.
Please see the following FAQ which summarised the sensitivity of K-ETOH: I am experiencing problems obtaining consistent/accurate results using the Ethanol Assay Kit (K-ETOH) – what should I do?
Reactions principles
K-ETOHLQR improves upon K-ETOH with a simplified reaction that results in less interference from environmental ethanol often present in the laboratory. Analyst error is also reduced due to lower sample dilution required for the assay.
Storage
Some K-ETOH individual components require specific storage at below -10C to ensure stability.
This specific storage is critical, it components are not stored correctly it can lead to a slower reaction time.
K-ETOHLQR kit components can all be stored at 4C.
Reaction time
K-ETOH reaction takes approx. 5 mins whereas the K-ETOHLQR is ever so slightly slower at approx. 7 mins.
Assay cost
K-ETOH is cheaper per assay to run when compared to K-ETOHLQR.
Both kits are spectrophotometric based and would require a wavelength of 340 nm for their performance. The choice between both is usually down to user preference.