Rapid Planar Chromatographic Analysis of 25 Water-Soluble Dyes Used as Food Additives

Abstract

A rapid planar chromatographic method for identification and quantification of 25 water-soluble dyes in food was developed. In a horizontal developing chamber, the chromatographic separation on silica gel 60F254 high-performance thin-layer chromatography plates took 12 min for 40 runs in parallel, using 8 mL ethyl acetatemethanolwateracetic acid (65 + 23 + 11 + 1, v/v/v/v) mobile phase up to a migration distance of 50 mm. However, the total analysis time, inclusive of application and evaluation, took 60 min for 40 runs. Thus, the overall time/run can be calculated as 1.5 min with a solvent consumption of 200 L. A sample throughput of 1000 runs/8 h day can be reached by switching between the working stations (application, development, and evaluation) in a 20 min interval, which triples the analysis throughput. Densitometry was performed by absorption measurement using the multiwavelength scan mode in the UV and visible ranges. Repeatabilities [relative standard deviation (RSD), 4 determinations] at the first or second calibration level showed precisions of mostly 2.7, ranging between 0.2 and 5.2. Correlation coefficient values (R 0.9987) and RSD values (4.2) of the calibration curves were highly satisfactory using classical quantification. However, digital evaluation of the plate image was also used for quantification, which resulted in RSD values of the calibration curves of mostly 3.0, except for two 6.0. The method was applied for the analysis of some energy drinks and bakery ink formulations, directly applied after dilution. By recording of absorbance spectra in the visible range, the identities of the dyes found in the samples were ascertained by comparison with the respective standard bands (correlation coefficients 0.9996). If necessary for confirmation, online mass spectra were recorded within a minute.

Performance of Electropun Polyacrylonitrile Nanofibrous Phases, Shown for the Separation of Water-Soluble Food Dyes via UTLC-Vis-ESI-MS

“…In the positive ion mode, the mass signals were marginal. For the dyes investigated, the desodiated molecule of E 103 at m/z 293.0 [M−Na] − , the twofold deprotonated molecule of E 105 at m/z 177.6 [M−2H] 2− and for the other dyes (E 111, E 127 and E 133) the twofold desodiated molecules [M−2Na] 2− were the dominant and characteristic base peaks ( Table 2 ), as already reported in [ 17 ] using HPTLC plates silica gel 60. Other minor signals in the mass spectra of the electrospun layers originated from the plate background.…”

“…On the manufactured electrospun PAN nanofiber phase, the linear calibrations of water-soluble food dyes obtained by videoevaluation resulted in precisions of the linear calibration functions of 3.1–9.1% (mean % RSD 5.7%) for peak heights and 2.4–9.3% (mean % RSD 5.5%) for peak areas ( Table 1 ). Hence, the quality (characterization by SEM), good efficiency (separation time and resolution), and performance (precisions and linear calibrations) of the electrospun PAN nanofiber phase for quantitative studies on such upcoming layer materials was successfully demonstrated, if compared to a powerful HPTLC method [ 17 ].…”

Scientific Opinion on the re‐evaluation of Brilliant Black BN (E 151) as a food additive

“…A number of different methods have been published for the analysis of Brilliant Black BN in foods, mostly based on clean-up by adsorption onto polyamide (powder or a column) followed by chromatographic determination. High Performance Liquid Chromatography (HPLC) has been mostly employed with diode array detection (Kirschbaum et al, 2006;Yoshioka and Ichihashi, 2008), but other approaches such as High Performance Thin Layer Chromatography (HPTLC) (Morlock and Oellig, 2009) and Capillary Electrophoresis (CE) have also been advocated (Frazier et al, 2000). Although diode array detection does provide some level of confirmation from scanned spectra, the most unequivocal identification of Brilliant Black BN in foods was conducted by eluting HPTLC zones for subsequent mass spectral confirmation (Morlock and Oellig, 2009).…”

Scientific Opinion on the re-evaluation of Amaranth (E 123) as a food additive

“…A number of different methods have been published for the analysis of Amaranth in various foods including direct analysis of beverages (Vachirapatama et al, 2008), including extraction into dimethyl sulfoxide (DMSO) (Ma et al, 2006) or clean-up by adsorption onto polyamide powder or polyamide columns (Kirschbaum et al, 2006;Morlock and Oellig, 2009) followed in each case by chromatographic determination. High Performance Liquid Chromatography (HPLC) with diode array detection has been mostly employed (Kirschbaum et al, 2006;Yoshioka and Ichihasi, 2008), although other approaches such as High Performance Thin Layer Chromatography (HPTLC) have also been used (Morlock and Oellig, 2009). Although diode array detection does provide some level of confirmation from scanned spectra, the most unequivocal identification of Amaranth in foods was conducted with electrospray Liquid Chromatography-Mass Spectrometry (LC-MS) (negative ionisation) using selected ion monitoring of m/z 537 (Ma et al, 2006).…”

“…Although diode array detection does provide some level of confirmation from scanned spectra, the most unequivocal identification of Amaranth in foods was conducted with electrospray Liquid Chromatography-Mass Spectrometry (LC-MS) (negative ionisation) using selected ion monitoring of m/z 537 (Ma et al, 2006). Methods have been applied to soft drinks and confectionery (Yoshioka and Ichihasi, 2008), soft drinks and bakery inks (Morlock and Oellig, 2009) and fish roe and caviar (Kirschbaum et al, 2006) (with recoveries for example of 91% from soft drinks and 93% from confectionery, CV = 2.1-5.4%). It can be concluded that methods of analysis for Amaranth in selected foods appear to be reliable, have received some validation and would be appropriate for use for survey or enforcement purposes.…”