Table 1. Overview of Analytical Methods, Parameters, and the Content of Lipoic Acid (LA), and Lipoyllysine (LLys) in Meat Products^a.

method	sample	analyte	linear range	recovery	LOD	LOQ	reference
colorimetric assay	animal tissues	LA	0–100 μmol/L	NR	NR	NR	(16)
enzymatic assay	animal tissues	LLys	1–5 μmol/L	NR	0.1 μmol/L	NR	(17)
GC-FID	chick livers, chicken eggs	LA	NR	34%	NR	NR	(21)
GC-FID	bacteria, cow’s milk, rat liver, rat kidney	LA	0–97 μmol/L	>87%	NR	NR	(22)
GC-MS	animal tissues	LA	0.05–97 μmol/L	60–70%	0.05 μmol/L	NR	(20)
GC-FDP	mouse tissue, bacterial cells	LA	20–500 ng	50–94%	50 pg	NR	(19)
HPLC-FLD	spinach, animal samples	LLys	0.0155–1 μmol/L	99–107%	0.007 μmol/L	0.022 μmol/L	(15)
HPLC-ECD	plant and animal tissue	LLys	0–2.5 μg/g	100%	NR	NR	(25)
HPLC-UV	enzyme hydrolysates	LLys	NR	117–120%	NR	NR	(24)
HPLC-DAD	liver, heart, kidney and stomach	LA LLys	0.1–10 μmol/L	88–101%	0.03 μmol/L	0.1 μmol/L	proposed method

^aNR: not reported.