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Evaluation of ice-tea quality by DART-TOF/MS.

Evaluation of ice-tea quality by DART-TOF/MS.

Journal of mass spectrometry : JMS (2015-10-28)

Aleš Rajchl, Jana Prchalová, Vojtěch Kružík, Rudolf Ševčík, Helena Čížková

ABSTRACT

DART (Direct Analysis in Real Time) coupled with Time-of-Flight Mass Spectrometry (TOF/MS) has been used for analyses of ice-teas. The article focuses on quality and authenticity of ice-teas as one of the most important tea-based products on the market. Twenty-one samples of ice-teas (black and green) were analysed. Selected compounds of ice-teas were determined: theobromine, caffeine, total phenolic compounds, total soluble solids, total amino acid concentration, preservatives and saccharides were determined. Fingerprints of DART-TOF/MS spectra were used for comprehensive assessment of the ice-tea samples. The DART-TOF/MS method was used for monitoring the following compounds: citric acid, caffeine, saccharides, artificial sweeteners (saccharin, acesulphame K), and preservatives (sorbic and benzoic acid), phosphoric acid and phenolic compounds. The measured data were subjected to a principal components analysis. The HPLC and DART-TOF/MS methods were compared in terms of determination of selected compounds (caffeine, benzoic acid, sorbic acid and saccharides) in the ice-teas. The DART-TOF/MS technique seems to be a suitable method for fast screening, testing quality and authenticity of tea-based products.

MATERIALS

Product Number

Brand

Product Description

Sigma-Aldrich

Sucrose, JIS special grade

Sigma-Aldrich

Sucrose, SAJ first grade

Supelco

Potassium Sorbate, analytical standard

Supelco

Phenol solution, 5000 μg/mL in methanol, certified reference material

Supelco

Phenol solution, certified reference material, 500 μg/mL in methanol

Sigma-Aldrich

Methanol solution, suitable for NMR (reference standard), 4% in methanol-d₄ (99.8 atom % D), NMR tube size 3 mm × 8 in.

Sigma-Aldrich

Sucrose, puriss., meets analytical specification of Ph. Eur., BP, NF

Sigma-Aldrich

Potassium sorbate, purum p.a., ≥99.0% (NT)

Sigma-Aldrich

Sucrose, BioUltra, Molecular Biology, ≥99.5% (HPLC)

Sigma-Aldrich

Nitrogen, ≥99.998%

Sigma-Aldrich

Sodium carbonate-¹²C, 99.9 atom % ¹²C

Sigma-Aldrich

Phenol solution, Equilibrated with 10 mM Tris HCl, pH 8.0, 1 mM EDTA, BioReagent, Molecular Biology

Sigma-Aldrich

Phenol solution, Saturated with 0.01 M citrate buffer, pH 4.3 ± 0.2, BioReagent, Molecular Biology

Sigma-Aldrich

Liquified Phenol, ≥89.0%

Sigma-Aldrich

Sucrose, ≥99.5% (GC)

Sigma-Aldrich

Sucrose, ACS reagent

Sigma-Aldrich

Sucrose, meets USP testing specifications

Sigma-Aldrich

Sucrose, ≥99.5% (GC), BioXtra

Sigma-Aldrich

Sucrose, ≥99% (GC), Grade I, suitable for plant cell culture

Sigma-Aldrich

Sucrose, ≥99.5% (GC), Grade II, suitable for plant cell culture

Supelco

Methanol solution, contains 0.10 % (v/v) formic acid, UHPLC, suitable for mass spectrometry (MS), ≥99.5%

Sigma-Aldrich

Sucrose, ≥99.5% (GC), BioReagent, suitable for cell culture, suitable for insect cell culture

Sigma-Aldrich

Sucrose, ≥99.5% (GC)

Sigma-Aldrich

Phenol, ≥99.0%

Sigma-Aldrich

Phenol, puriss., meets analytical specification of Ph. Eur., BP, USP, 99.5-100.5% (GC)

Sigma-Aldrich

Caffeine, meets USP testing specifications, anhydrous

Sigma-Aldrich

Phenol, SAJ first grade, ≥98.0%

Sigma-Aldrich

Caffeine, powder, ReagentPlus^®

Sigma-Aldrich

Gallic acid, 97.5-102.5% (titration)

Sigma-Aldrich

Phenol, ≥96.0% (calc. on dry substance, T)