Direct UV determination of Amadori compounds using ligand-exchange and sweeping capillary electrophoresis

Abstract

The detection of Amadori compounds poorly absorbing in the UV region is challenging. To cope with this problem, a simple and effective method using ligand-exchange and sweeping capillary electrophoresis was first developed. With this method, Amadori compounds can be detected by UV at 236 nm without derivatization steps and separated based on the stable levels of Amadori compound-Cu(2+) complexes. Under optimal conditions with background electrolyte of 50 mmol/L copper sulfate, pH 3.94, and separation voltage 25 kV, baseline separations of the following five Amadori compounds, N-(1-deoxy-D-fructos-1-yl) valine (Fru-Val), N-(1-deoxy-D-fructos-1-yl) leucine (Fru-Leu), N-(1-deoxy-D-fructos-1-yl) alanine (Fru-Ala), N-(1-deoxy-D-fructos-1-yl) methionine (Fru-Met), N-(1-deoxy-D-fructos-1-yl) glutamic acid (Fru-Glu), were achieved within a 20 min run. The method was applied to analyze these Amadori compounds in two tomato products. Fru-Glu could be quantitated sensitively down to 0.706 mg/L in MS powder (a kind of tomato powder), 0.726 mg/L in MS liquid (a kind of concentrated tomato juice), and the limit of quantification for the others ranged from 0.792 to 1.084 mg/L. The most abundant Amadori compound was Fru-Glu (1057.5 mg/100 g) in MS powder; however, Fru-Met was rarely detected in MS liquid. The accuracy of the method was tested by recovery measurement of the spiked samples, which yielded good results (94.2-106.0%) with relative standard deviation lower than 5%. Simultaneously, the method was also applied in the analysis of Fru-Glu content during a tomato puree evaporating concentration process. The first significant increase in Fru-Glu content coincided with the increment rate of soluble solids, which indicated that fast evaporation of water could be a critical step for the formation of Amadori compounds. These results show that this method is convenient and reliable for rapid analysis of Amadori compounds in tomato products.

Recent progress of sample stacking in capillary electrophoresis (2016–2018)

“…A CE‐sweeping method based on dynamic complexation with copper ions was developed by Yu et al. and used to analyze five Amadori compounds (intermediates of Maillard reaction in foods) in tomato products. Combination of a BGE containing 50 mM CuSO 4 and HAc at pH 3.94 and of samples dissolved in water assured both sweeping of the analytes and UV detection of the formed complexes at 236 nm without derivatization.…”

LC‐MS/MS for simultaneous detection and quantification of Amadori compounds in tomato products and dry foods and factors affecting the formation and antioxidant activities

“…The potential health effects of various ACs have instigated great interests. To begin with the study, a rapid and reliable analytical method is warranted for the identification and quantification of different ACs during food processing (Hau, Devaud, & Blank, ; Yu, Aboshora, Zhang, & Zhang, ).…”

“…One technique currently in use for the separation of ACs is capillary electrophoresis (CE). This CE method could also be applied to detect ACs with mass spectrometry (MS), however, the drawback is that it is quite expensive and not widespread (Hau et al., ; Yu et al., ). Recently, a CE method with UV detector without derivatization steps was developed to quantify ACs.…”

“…Recently, a CE method with UV detector without derivatization steps was developed to quantify ACs. The separation of ACs is based on the stable levels of AC‐Cu 2+ complexes (Yu et al., ). However, it is quite difficult to efficiently separate analytes over five species.…”

Composition and stability constants of copper(II) complexes with succinic acid determined by capillary electrophoresis

“…The copper(II) complexes are also employed in CE for the metal determination [24] and in ligand-exchange CE for the separation of different organic analytes [36][37][38][39][40], including enantiomers [37]. But the CE technique has not been used early for studying the copper(II) complexes with succinic acid ions.…”