Sensitive and highly selective determination of vitamin B1 in the presence of other vitamin B complexes using functionalized gold nanoparticles as fluorophore†
The present work describes the highly selective and sensitive determination of vitamin B1 (thiamine) using 4-amino-6-hydroxy-2-mercaptopyrimidine capped gold nanoparticles (AHMP-AuNPs) by spectrofluorimetry. The AHMP-AuNPs were synthesized by wet chemical method and were characterized by HR-TEM, XRD, UV-visible, zeta potential and spectrofluorimetry. They show emission maximum at 781 nm while exciting at 520 nm and a large stock shift (261 nm) with a narrow emission profile and good photostability. While adding 0.15 μM thiamine, the red color solution of AHMP-AuNPs changes to purple and the absorbance at 520 was decreased. This is due to the aggregation of AHMP-AuNPs and it was confirmed by HR-TEM. No change in absorbance was observed in the UV-visible spectra for AHMP-AuNPs in the presence of less than micromolar concentration of thiamine. On the other hand, the emission intensity of AHMP-AuNPs was enhanced even in the presence of picomolar concentration of thiamine. Based on the enhancement of emission intensity, the concentration of thiamine was determined. Interestingly, no change in the emission intensity was observed while adding even milli molar concentration of other vitamin B complexes. The present fluorophore showed an extreme selectivity towards the determination of thiamine in the presence of 10 000 fold common interferents including vitamin B2, B3, B6, B9 and vitamin C while the presence of cysteine and glutathionine interferes for the determination of thiamine. A good linearity was observed from 10 to 120 × 10−12 M thiamine and a detection limit was found to be 6.8 fM L−1 (S/N = 3). The present method was successfully used for the determination of thiamine in human blood serum samples.