Development and validation of an HPLC method with fluorescence detection for the determination of fluorescent whitening agents migrating from plastic beverage cups

Figures & data

Table 1. Chemical structures of the FWAs studied.

Chemical name	Chemical formula	FCM No.^a	Colour index (C.I.)	SML (mg kg^−1)^a	CAS No.	Chemical structure
1,4-bis-(2-benzoxazolyl)-naphthalene	C24H14N2O2	-	367	-	5089–22-5
1,2-bis (5-methyl-2-benzoxazole) ethylene	C18H14N2O2	-	135	-	1041–00-5
4,4ʹ-bis (2-benzoxazolyl) stilbene	C28H18N2O2	422	393	0.05	1533–45-5
2,5-bis(5-tert-butyl-2-benzoxazolyl) thiophene	C26H26N2O2S	500	184	0.6	7128–64-5
4-(2-benzoxazolyl)-4ʹ-(5-methyl-2-benzoxazolyl) stilbene	C29H20N2O2	919	368	NR^b	5242–49-9
4,4ʹ-bis (5-methyl-2-benzoxazolyl) stilbene	C30H22N2O2	920	76	NR^b	2397–00-4
Mixture of: 1. 4-(2-benzoxazolyl)-4′-(5-methyl-2-benzoxazolyl) stilbene, 2. 4,4′-bis (2-benzoxazolyl) stilbene 3. 4,4′-bis(5-methyl-2-benzoxazolyl)stilbene	C28H18N2O2 C29H20N2O2 C30H22N2O2	65	-	See note^c	1533–45-5 5242–49-9 2397–00-4

^aEU Regulation 10/2011 [EU. 2011].

^bNR = not included in the positive list of the EU Reg. 10/2011.

^cNot more than 0.05% (w/w) (quantity of substance used/quantity of the formulation). The mixture obtained from the manufacturing process in the typical ratio of (58–62%):(23–27%):(13–17%).

Figure 1. HPLC-FLD chromatogram of Simulant D1 fortified with FWAs standard mixture.

Peak order and mass fractions: 1 = 1,2-bis (5-methyl-2-benzoxazole) ethylene, 3.6 min, 3.0 µg kg⁻¹; 2 = 1,4-bis-(2-benzoxazolyl)-naphthalene, 12.4 min, 3.0 µg kg⁻¹; 3 = FCM 422, 14.4 min, 5.0 µg kg⁻¹; 4 = FCM 919, 20.2 min, 5.0 µg kg⁻¹; 5 = FCM 920, 21.2 min, 5.0 µg kg⁻¹; 6 = FCM 500, 21.7 min, 5.0 µg kg⁻¹.

Table 2. Combined method performance characteristics in fortified food simulants A, C and D1 with FWAs standard mixtures (300 μg kg⁻¹).

	Retention time (Rt)		Peak area^a
Analyte	(min)	RSD (%)	(±Sd)	RSD (%)	Resolution Factor (Rs)	Tailing Factor (T)
1 – 1,2-bis (5-methyl-2-benzoxazole) ethylene	3.6	0.72	1311 (±17)	1.31	-	0.84
2 – 1,4-bis-(2-benzoxazolyl)-naphthalene	12.4	0.63	741 (±10)	1.29	23.2	0.90
3 – FCM 422	14.4	0.55	1444 (±126)	0.98	3.2	0.84
4 – FCM 919	20.2	0.16	358 (±28)	3.13	12.2	0.89
5 – FCM 920	21.2	0.07	576 (±22)	3.82	4.6	0.74
6 – FCM 500	21.7	0.06	1538 (±12)	0.81	3.8	0.94

^aCombined average of 3 replicates per spiked food simulant A, C and D1.

Table 3. Linearity, linear range and sensitivity results of the method developed for food simulants A, C and D1.

Analyte	Calibration curve (±Sd)	R^2	LOD (μg kg^−1)	LOQ (μg kg^−1)	Linear range (μg kg^−1)
1,2-bis (5-methyl-2-benzoxazole) ethylene	y = 4326 (±50).x + 0.8 (±7)	0.9996	0.066	0.133	0.133–10,000
1,4-bis-(2-benzoxazolyl)-naphthalene	y = 2465 (±27).x + 0.4 (±4)	0.9996	0.088	0.164	0.164–10,000
FCM 422	y = 3243 (±135).x – 12 (±33)	0.9948	0.251	0.504	0.504–10,000
FCM 919	y = 864 (±34).x + 2 (±9)	0.9953	0.193	0.386	0.386–5000
FCM 920	y = 1291 (±52).x + 6 (±13)	0.9980	0.151	0.303	0.303–5000
FCM 500	y = 3139 (±76).x + 9 (±19)	0.9982	0.053	0.107	0.107–5000

Table 4. Mass fractions (μg per kg of plastic) of the tested FWAs in the tested plastic cup specimens as obtained after ASE and Soxhlet extraction with ethanol.

	FCM 422 *		FCM 919 *		FCM 920 *		FCM 500
	μg kg^−1		μg kg^−1		μg kg^−1		μg kg^−1
Tested cup	ASE	Soxhlet	ASE	Soxhlet	ASE	Soxhlet	ASE	Soxhlet
PS1	2.32	0.03	nd	nd	nd	nd	0.32	0.16
PS2	nd	0.06	nd	nd	nd	nd	0.04	0.04
PS3	4.46	0.15	3.83	nd	7.46	nd	0.04	0.01
PS4	0.04	0.01	nd	nd	nd	nd	0.09	0.03
PS5	0.18	0.01	0.01	nd	nd	nd	0.21	0.07
PS6	0.24	0.06	nd	nd	nd	nd	0.13	nd
PP1	0.04	0.01	nd	nd	nd	nd	0.05	0.02
PP2	0.21	0.01	nd	nd	nd	nd	0.95	0.14
PP3	0.06	0.01	nd	nd	nd	nd	2.1	0.98
PET	0.04	0.01	nd	nd	nd	nd	0.05	0.02

nd = not detectable; mass fraction below LOD

* also part of mixture FCM 65

[EC] European Commission. 2011. Commission Regulation (EU) No. 10/2011 of 14 January 2011 on plastic materials and articles intended to come into contact with food. Off J Eur Comm. L 12:1.

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