Separation and determination of acesulfame-K in soy sauce by capillary electrophoresis with contactless conductivity detection using liquid-liquid extraction and field-amplified sample injection

doi:10.3724/SP.J.1123.2019.11029

Abstract

Abstract:

A new method was established for the sensitive determination of artificial synthetic sweetener acesulfame-K in soy sauce by capillary electrophoresis (CE) with field-amplified sample injection (FASI)and capacitively coupled contactless conductivity detection (C⁴D). Liquid-liquid extraction (LLE) technology was employed to eliminate the complex matrix interference co-existing in soy sauce. Ethyl acetate was used as the extraction solution. The pH of the sample solution was adjusted to 1.7, and both inorganic salts and organic compounds causing interferences were effectively removed by LLE. The type and volume of the extraction solvents, pH of the sample solutions, extraction method and extraction time were investigated in detail. Under the optimized experimental conditions, acesulfame-K in soy sauce was well separated and sensitively detected. The limit of detection and limit of quantification were 0.15 mg/kg and 0.48 mg/kg, respectively. The accuracy was tested by spiking acesulfame-K into soy sauce samples, and the recoveries ranged from 92.3% to 108.1%. The relative standard deviations were below 8.0%. The proposed method can meet the requirements for the fast screening and sensitive detection of acesulfame-K in soy sauce samples.

Key words: capillary electrophoresis (CE), capacitively coupled contactless conductivity detection (C⁴D), field-amplified sample injection (FASI), liquid-liquid extraction (LLE), acesulfame-K, soy sauce

CHEN Hushui, JIANG Jiankun, YI Jia, XIE Tianyao. Separation and determination of acesulfame-K in soy sauce by capillary electrophoresis with contactless conductivity detection using liquid-liquid extraction and field-amplified sample injection[J]. Chinese Journal of Chromatography, 2020, 38(6): 708-714.

Figures/Tables 6

Fig. 1 CE-C4D electropherograms of acesulfame-K by (a) normal hydrodynamic injection (5.0 mg/L) and (b) FASI (0.10 mg/L) C4D: capacitively coupled contactless conductivity detection; FASI: field-amplified sample injection.

Fig. 2 Effect of the amount of extraction solution on the recovery of acesulfame-K (n=5)

Fig. 3 Effect of pH values of soy sauce samples after acidification on the recovery of acesulfame-K (n=5)

Fig. 4 FASI-CE-C4D electropherograms of the soy sauce sample (a) before and (b) after clean-up procedure

Table 1 Contents and spiked recoveries of acesulfame-K in six soy sauce samples (n=5)

Sample No.	Background^a)/(mg/kg)	Added/(mg/kg)	Found/(mg/kg)	Recovery/%	RSD/%
a): the original soy sauce samples diluted 100 times. ND: not detected.
1	2.30	2.00	4.65	108.1	4.2
2	ND	2.00	1.84	92.3	7.1
3	ND	2.00	1.90	94.8	7.1
4	ND	2.00	2.02	101.3	6.6
5	1.61	2.00	3.57	98.6	5.0
6	1.89	2.00	3.97	101.9	4.8

Fig. 5 FASI-CE-C4D electropherograms of acesulfame-K in the blank and spiked soy sauce samples a. blank sample; b. spiked with 0.80 mg/kg acesulfame-K; c. spiked with 2.0 mg/kg acesulfame-K.

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