SPE/TLC/Densitometric Quantification of Selected Synthetic Food Dyes in Liquid Foodstuffs and Pharmaceutical Preparations

Table 1

Selected references on TLC separation and/or quantification of synthetic food dyes (including some illegal or delisted examples).

Dyes	Sorbent	Eluent	Detection method	Ref.
Amaranth, indigotine, tartrazine, Ponceau 4R, orange yellow, Allura Red, Brilliant Blue, food green 3	Silica gel RP18	Methanol-acetonitrile-5% aq.; Na2SO4 (3 : 3 : 10, v/v/v); Methanol-butanone-5% aq.; Na2SO4 (1 : 1 : 1, v/v/v)	Densitometry	[14]
Detection of illegal dyes	RP-18	Methanol-acetonitrile-5% aq.; Na2SO4 (3 : 3 : 10, v/v/v); Methanol-butanone-5% aq.; Na2SO4 (1 : 1 : 1, v/v/v); Methanol-butanone-5% aq.; Na2SO4 (1 : 1 : 1, v/v/v)	Mass spectroscopy	[13]
Tartrazine, azorubine, orange yellow	NH2	i-PrOH-Et2O-NH3 (2 : 1 : 1 v/v/v)	Video-scanning	[15]
Ponceau 4R, tartrazine, orange yellow	Silica gel 60	i-PrOH-NH3-H2O; (10 : 1 : 1 v/v/v)	Sorbent scraping, extraction, and spectrophotometry	[11]
Indigotine, Ponceau 4R, orange yellow, tartrazine, amaranth	MgO	Sodium citrate 15% aq.-methanol; (4 : 1 v/v)	Visual	[20]
Amaranth, tartrazine, orange yellow	Silica gel	n-butanol-ethanol-H2O-NH3(10 : 5 : 5 : 2 v/v/v/v)	Visual	[3]
Tartrazine, Allura Red	RP-18W	Methanol-citric buffer pH 3.5 (45 : 55 v/v)	Densitometry	[4]
Ponceau 4R	RP-18W	Tetrahydrofuran-acetic buffer pH 3.5 (45 : 55 v/v)
Brilliant Blue	CN	1,4-Dioxane-acetic buffer pH 3.5-H2O (25 : 20 : 55 v/v/v) + 0.025 M sodium octane-1-sulfonate
Azorubine	RP-18W	Acetone-acetic buffer pH 3.5 (4 : 6 v/v)
Patent blue	CN	Tetrahydrofuran-acetic buffer pH 3.5-H2O (25 : 20 : 55 v/v/v) + 0.025 M diethylamine	Densitometry	[4]
Quinoline yellow	RP-18W	1,4-Dioxane-acetic buffer pH 3.5 (1 : 9 v/v)
Amaranth, tartrazine, Brilliant Blue	Scolecite	Acetone	Visual	[21]
	Silica gel G
Tartrazine, orange yellow, quinolone yellow, amaranth, Ponceau 6R, erythrosine, indigotine, Brilliant Blue, brilliant black	RP-18	Water-ethanol-(NH4)2SO4 aq.; Water-acetone-(NH4)2SO4 aq.	Visual	[22]
Fat soluble dyes	Al2O3	Petroleum ether-CCl4 (1 : 1 v/v)	Visual	[8]
	Starch impregnated with paraffin or vegetable oil	MeOH-H2O-AcOH (80 : 15 : 5 v/v/v)
Water soluble dyes	Polyamide powder	NH3-methanol-H2O 5 : 15 : 80 (v/v/v)
Fat soluble dyes	Silica gel G	Benzene	Visual	[23]
Water soluble dyes	Silica gel G	i-BuOH-HCOOH-H2O (25 : 10 : 10 v/v/v)
		i-BuOH-AcOH-H2O (25 : 10 : 10 v/v/v)
		Butanone-methyl isobutyl ketone-AcOH-H2O (20 : 10 : 10 : 5 v/v/v/v)
		i-BuOH-i-PrOH-NH3 aq. (1 : 1 : 1 v/v/v)
		Butanone-pyridine-H2O (4 : 1 : 1 v/v/v)
Naphthol yellow, tartrazine, Ponceau 4R, amaranth, erythrosine, rhodamine B, indigotine, patent blue	Silica gel G	EtOH-n-BuOH-H2O (9 : 2 : 1 v/v/v)	Sorbent scraping, extraction, and spectrophotometry	[12]
			Densitometry
			Spectral reflectance
Tartrazine, orange yellow, amaranth, Ponceau SX, erythrosine, Allura Red, Brilliant Blue, food green 3	Silica gel 60	n-BuOH-AcOH-H2O (4 : 1 : 5 v/v/v)	Densitometry	[5]
		n-BuOH-EtOH-H2O-NH3 (10 : 5 : 5 : 2 v/v/v/v)