Standardization of UV-visible data in a food adulteration classification problem.

This study evaluates the performance of multivariate calibration transfer methods in a classification context. The spectral variation caused by some experimental conditions can worsen the performance of the initial multivariate classification model but this situation can be solved by implementing standardization methods such as Piecewise Direct Standardization (PDS). This study looks at the adulteration of culinary spices with banned dyes such as Sudan I, II, III and IV. The samples are characterised by their UV-visible spectra and Partial Least Squares-Discriminant Analysis (PLS-DA) is used to discriminate between unadulterated samples and samples adulterated with any of the four Sudan dyes. Two different datasets that need to be standardised are presented. The standardization process yields positive classification results comparable to those obtained from the initial PLS-DA model, in which high classification performance was achieved.

Modulation of mobile phase composition in flow-injection/sequential-injection chromatography exploiting multisyringe flow analysis.

In this paper, a time-based multicommutated flow system is proposed for appropriate selection and modulation of mobile phase composition in flow-injection (FI)/sequential-injection (SI) chromatography. The novel flow assembly involves the on-line coupling of a short monolithic reversed-phase chromatographic column with a multisyringe flow injection set-up furnished with a set of solenoid valves. The proposed hyphenated technique was applied to the simultaneous spectrophotometric determination of thiamine (B(1)), pyridoxine (B(6)) and cyanocobalamin (B(12)) which were taken as model analytes. The separation method capitalizes on a dual isocratic elution protocol involving the use of a single forward stroke of the multisyringe pump for initial delivery of 50 mmol L(-1) ammonium acetate (pH 7.0) for 2.4 min followed by 50 mmol L(-1) ammonium acetate-methanol (80:20, v/v) for 6.4 min at 0.5 mL min(-1) and room temperature. Detection was performed at the maximum wavelength for each target vitamin-280 nm for B(1), 325 nm for B(6), and 360 nm for B(12). A first-order, two-level full-factorial design was utilized to ascertain the significant variables influencing the chromatographic separation and the magnitude of the interaction effects. The experimental design method revealed that resolution of the target vitamins is highly dependent on the pH, percentage of organic modifier, and their second-order interaction. The multisyringe flow-injection-based monolithic column separation method, which should be viewed as an expeditious and cost-effective alternative to the high-performance liquid chromatography counterpart, was applied to the separation and determination of B(1), B(6), and B(12) in different pharmaceutical dosage forms in less than 9 min. Statistical comparison of the results from the proposed procedure with those from the HPLC method endorsed by the US Pharmacopeia revealed there were no significant differences at the 95% confidence level.