title: Application of derivative and derivative ratio spectrophotometry to simultaneous trace determination of rhodamine B and rhodamine 6G after dispersive liquid-liquid microextraction.
abstract: Two novel methods, first derivative spectrophotometric method ((1)D) and first derivative ratio spectrophotometric method ((1)DR), have been developed for the simultaneous trace determination of rhodamine B (RhB) and rhodamine 6G (Rh6G) in food samples after dispersive liquid-liquid microextraction (DLLME). The combination of derivative spectrophotometric techniques and DLLME procedure endows the presented methods with enhanced sensitivity and selectivity. Under optimum conditions, the linear calibration curves ranged from 5 to 450 ng mL(-1), with the correlation coefficients (r) of 0.9997 for RhB and 0.9977 for Rh6G by (1)D method, and 0.9987 for RhB and 0.9958 for Rh6G by (1)DR method, respectively. The calculated limits of detection (LODs) based on the variability of the blank solutions (S/N = 3 criterion) for 11 measurements were in the range of 0.48-1.93 ng mL(-1). The recoveries ranged from 88.1% to 111.6% (with RSD less than 4.4%) and 91.5-110.5% (with RSD less than 4.7%) for (1)D and (1)DR method, respectively. The influence of interfering substances such as foreign ions and food colorants which might be present in the food samples on the signals of RhB and Rh6G was examined. The developed methods have been successfully applied to the determination of RhB and Rh6G in black tea, red wine and chilli powder samples with the characteristics of simplicity, cost-effectiveness, environmental friendliness, and could be valuable for routine analysis.
authors.affiliation: School of Chemistry and Chemical Engineering, University of South China, Hengyang, Hunan 421001, China.
authors.forename: Ni
authors.initials: N
authors.lastname: Xiao
authors.affiliation: School of Chemistry and Chemical Engineering, University of South China, Hengyang, Hunan 421001, China. Electronic address: jdeng_usc@163.com.
authors.forename: Jian
authors.initials: J
authors.lastname: Deng
authors.affiliation: School of Chemistry and Chemical Engineering, University of South China, Hengyang, Hunan 421001, China.
authors.forename: Kaihui
authors.initials: K
authors.lastname: Huang
authors.affiliation: School of Chemistry and Chemical Engineering, University of South China, Hengyang, Hunan 421001, China.
authors.forename: Saiqin
authors.initials: S
authors.lastname: Ju
authors.affiliation: School of Chemistry and Chemical Engineering, University of South China, Hengyang, Hunan 421001, China.
authors.forename: Canhui
authors.initials: C
authors.lastname: Hu
authors.affiliation: School of Chemistry and Chemical Engineering, University of South China, Hengyang, Hunan 421001, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Liang
mesh_terms: D005504:Food Analysis / Q000379:methods*; D005505:Food Coloring Agents / Q000032:analysis*; D012235:Rhodamines / Q000737:chemistry*; D013053:Spectrophotometry
chemical_list: D005505:Food Coloring Agents; D012235:Rhodamines; C026188:rhodamine 6G; C029773:rhodamine B
keywords: Derivative ratio spectrophotometry; Derivative spectrophotometry; Dispersive liquid–liquid microextraction; Food samples; Rhodamine 6G; Rhodamine B