Validation and measurement uncertainty evaluation of the GC-MS method for the direct determination of hexamethylenetetramine from foods.

A simple GC-MS method has been developed and validated for the direct determination of hexamethylenetetramine (HMT). The separation of HMT was performed using a MXT-1 column. The calibration curve was linear over the concentration range 0.1-25 µg/mL, with a good correlation coefficient (r =0.9996). The recoveries of HMT from foods spiked at 1, 5, and 10 µg/g ranged from 91.7% to 115.2%. Intra-day (n=5) and inter-day (n=5) precision were less than 7%. The limit of detection and the limit of quantification of the method were 0.05 and 0.15 µg/mL, respectively. The uncertainties associated with food matrix and calibration contributed most to the overall expanded uncertainty. The method validation data indicated that quantitative method could be applied to the direct determination of non-hydrolyzed HMT in foods.

Assessment of caffeine intake in the Korean population.

An improved method for the analysis of caffeine in foods by HPLC was validated by measuring several analytical parameters. The caffeine contents of 1202 products available from Korean markets were analysed. A consumption study was conducted by using data from the Korea National Health and Nutrition Examination Survey (KNHANES), 2010-12, to estimate the caffeine intakes of the Korean population. The mean intakes of caffeine from all sources in the general population and consumers were 67.8 and 102.6 mg day(-1) for all age groups, respectively. The 95th percentile intakes of the general population and consumers were 250.7 and 313.7 mg day(-1), respectively. In those aged 30-49 years, the caffeine intakes of the general population and consumers were highest at 25.5% (101.8 mg kg(-1) day(-1)) and 36.6% (0.9 mg kg(-1) day(-1)), respectively, compared with the maximum recommended daily intake (400 mg day(-1)) for adults. In the general population, the main contributors to the total caffeine intake were carbonated beverage for the younger age groups and coffee for the adults. These data provide a current perspective on caffeine intake in the Korean population.

Determination of Tinopal CBS-X in rice papers and rice noodles using HPLC with fluorescence detection and LC-MS/MS.

To date there have been no reports of methods to determine Tinopal CBS-X. We developed a rapid and simple method to determine the Tinopal CBS-X content in rice noodles and rice papers using HPLC equipped with fluorescence detection. Heating the rice noodles and rice papers to 80°C after adding 75% methanol solution induced the release of Tinopal CBS-X from processed rice products. Tinopal CBS-X was separated using an isocratic mobile phase comprising 50% acetonitrile/water containing 0.4% tetrabutyl ammonium hydrogen sulphate at pH 8.0. The samples suspected to be positive by HPLC analysis were then confirmed by LC-MS/MS analysis. This study also investigated the Tinopal CBS-X content of three rice noodle products and two rice papers. The limits of quantification for rice papers and rice noodles were 1.58 and 1.51 µg kg(-1), respectively, and their correlation curves showed good linearity with r(2) ≥ 0.9997 and ≥ 0.9998, respectively. Moreover, rice papers had recoveries of 70.3-83.3% with precision ranging from 5.0% to 7.9%, whereas rice noodles had slightly lower recoveries of 63.4-78.7% and precisions of 8.5-11.5%. Only one rice noodle product contained Tinopal CBS-X, at around 2.1 mg kg(-1), whereas it was not detected in four other samples. Consequently, Tinopal CBS-X from rice noodles and rice papers can be successfully detected using the developed pre-treatment and ion-pairing HPLC system coupled with fluorescence detection.

Quantitative determination of carmine in foods by high-performance liquid chromatography.

A simple and rapid method has been developed and validated for the determination of carmine in foods. Samples were homogenised and extracted with 0.05 M NaOH, followed by centrifugation. The resulting solution was filtered and injected to HPLC. Carmine was separated by HPLC using an NovaPak C18 column coupled to a photodiode array detector. The contents of carmine were finally quantified using corresponding calibration curves over ranges of 1.0-100 µg ml(-1), with good correlation coefficients (r(2)=0.9999). The recoveries of carmine from foods spiked at levels of 10, 50, and 100 µg g(-1) which ranged from 90.4% to 96.2% with relative standard deviations between 2.8% and 6.8%. Limit of detection and limit of quantification of carmine were 0.4 and 1.0 µg ml(-1), respectively. This method was found to be useful to distinguish carmine from carminic acid, a major component of cochineal extract. The method has been successfully applied to various foods.