Chemometric methods simultaneous determination

R. Petkovska, C. Cornett, A. Dimitrovska, Development and validation of rapid resolution RP-HPLC method for simultaneous determination of atorvastatin and related compounds by use of chemometrics, Anal. Lett. 41 (2008) 992-1009. 

A chemometric method for simultaneous determination of calcium and magnesium in natural waters using Arsenazo III and FIA system was described [5], The concentrations of the analytes were calculated by the H-point standard addition method for ternary mixtures. 

Fort he determination of preservatives and sweeteners in soft drinks or fruit juices LC analysis with UV detection is widely used. The sample pretreatment, prior to LC analysis, often consists only of degassing, filtration and dilution of the liquid [2]. Sometimes a liquid-liquid extraction, suitable not only for soft drinks but also for more complex matrices, is applied [3]. Chemometric methods applied to overlapped spectra offer the advantage of minimizing or eliminating sample preparation by allowing to simultaneously determining one or more analytes in relatively complex matrices. 

Each chemometric method relies on different tools of regression analysis of multicomponent system permitting simultaneous determination of two or more components. 

The simultaneous monitoring of three drugs requires chemometric methods. The fluorimetric determination of vitamins Bi, B2, and Bg from multicomponent solid... 

In simultaneous determination, some kind of resin or chemometric method (principal component regression) is used for improving the selectivity. For speciation, generally the same wavelength is used for determining different iron species. Sometimes... 

Other examples presented in the literature are those based on the use of copolymeric disk-based sorbent materials for the isolation and preconcentration of nitro-substituted phenol isomers and the concurrent removal of potentially interfering matrix components followed by onhne simultaneous determination of individual species by diode array spectrophotometry, via chemometric deconvolution of the overlapped spectra, without the need for chromatographic separation. In contrast to bead-extraction, no flow impedance is observed when using extraction disks while better enrichment factors are obtained because of the improved specific surface area. Compared with earlier methods for isolation/preconcentration of nitrosubstituted phenols based on liquid-liquid extraction, these systems should be regarded as environmentally friendly approaches because the use of harmful organic solvents is circumvented. 

Several methods have been developed for determination of Sunset Yellow mixed with other colorants. A simple and sensitive kinetic spectrophotometric method has been developed for the simultaneous determination of Amaranth, Ponceau 4R, Sunset Yellow, Tartrazine, and Brilliant Blue in mixtures with the aid of chemometrics [31]. This work involved two coupled reactions, the reduction of iron(III) by the analytes to iron(II) in sodium acetate/hydrochloric acid solution (pH 1.71,) and the chromogenic reaction between iron(II) and hexacyanoferrate(III) ions to yield a Prussian blue peak at 760 nm. The spectral data were recorded over the 500-1000 nm wavelength range every 2 s for 600 s. The kinetic data were collected at 760 nm and 600 s, and linear calibration models were satisfactorily constructed for each of the dyes, with detection limits in the range 0.04-0.50 mg/L. 

Multivariate calibration has the largest number of applications of chemometric methods in routine analysis for instance it became a widely used technique in quantitative analy.sis of complex mixtures by IR or UV detectors, especially in food chemistry and environmental analytical chemistry. A number of textbooks, tutorials, and reviews " have been published in this field, and software is offered by the instrument manufacturers. Applications of multivariate calibration is very widespread, ranging for instance from the determination of moisture in mushrooms to research for non-invasive measurement techniques of glucose in human blood. The multivariate methods mostly applied are PLS, PCR. and recently also neural networks, Typical calibration models describe the relationship between a set of x-variables (UV or IR absorbances) and one y-variable (concentration of one substance) although it is possible to derive models that simultaneously predict a set of y-variables. 

The use of chemometrics will continue to increase and is almost mandatory for online applications. The spectral stripping of cigarette smoke could be done using a chemometrics approach rather than by sequential subtraction. The advantage is that all the components would be determined simultaneously without the laborious and somewhat subjective subtractions. The disadvantage is that the work to setup the method is somewhat greater however, for a large number of samples this would be recovered in reduced time per analysis and the use of less skilled personnel. The trade-off between time to setup the method and time to carry out the analysis is the usual case. 

ATR-FTIR is a useful analytical tool for multicomponent analysis that employs a mathematical data-treatment process. Also, Carolei and Gutz (2005) have used this technique combined with chemometrics, to determine three surfactants and water simultaneously in shampoo and in liquid soap without either sample dilution or pretreatment. The surfactants analysed were an amphoteric one (cocoamidopropyl betaine), two nonionic ones (coco diethanolamide in shampoo and alkylpolyglucoside in liquid soap), (minor components) and an anionic one (sodium lauryl ether sulfate). Overlapping bands and water absorption were resolved by two multivariate quantification methods classical least squares (CLS) and inverse least squares (ILS) (Massart et al., 1997, 1998). The wave numbers chosen for the calculation process were preferably those of maximum absorption of the minor components. This method can be applied during the production process but not in final product analysis because of interference caused by the fragrance added in the last step (Figure 7.1.2). 

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