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This manuscript covers the application of the main techniques for simultaneous optimization of multiple responses generated by the application of multivariate designs (two-factor factorial, Central Composite, Doehlert, etc.) or by chromatographic runs in the development of analytical methods. Special attention will be given to the graphical method, desirability function, multiple response function and chromatographic response functions, since they are more frequently used in the analytical area. The advantages, disadvantages, limitations, and potentialities of these methods will also be addressed, as well as some of their applications, commenting on real examples from the literature. Some less usual methods in multiple response optimization in Analytical Chemistry will also be commented.

This work proposes an analytical strategy utilizing digital images (DI) for the iron inorganic speciation in white wine. The method was established by the reaction of iron(II) ions with 1,2 ortho-phenanthroline as a chromogenic reagent. Total iron was determined using the same reagent after the addition of hydroxyl ammonium chloride as a reducing agent. In both cases, digital images of the standards/chromogenic reagent and samples were acquired and stored in JPEG format. The region of interest (ROI) was determined with a constant square shape for all images. The ROI was submitted to decomposition in color values according to the RGB additive color model. However, the data obtained by the blue channel was the one used in the construction of the analytical curves because it presented the highest sensitivity. The optimization of the experimental conditions of the procedure was performed by employing multivariate techniques. The precision was evaluated using a wine sample with iron (II) and total iron contents of 0.41 and 0.69 mg L−1, respectively. The results expressed as relative standard deviations were 3.57% for iron (II) and 4.76% for total iron contents. A comparison between the results obtained for total iron by the DI method with the results found using flame atomic absorption spectrometry confirmed the method accuracy. The DI procedure was applied for speciation analysis in six white wine samples and the contents found varied from 0.41 to 1.67 mg L−1 for iron (II) and from 0.69 to 1.71 mg L−1 for total iron. These results are in agreement with those found for speciation analysis of iron in wine samples. Iron (III) contents can be found by the difference between the total iron and iron (II) contents.

Sweet potato is a food consumed in the world. In this work, the minerals and centesimal composition in sweet potatoes of organic and conventional cultivars was investigated. The accuracy was confirmed with a certified reference material of apple leaves (NIST 1515). The quantification of the samples was performed by inductively coupled plasma optical emission spectrometry and the digestion efficiency was evaluated by residual carbon content. The mean concentrations (in mg/100 g) of minerals were: 23.5 and 40.7 (Ca); 0.082 and 0.159 (Cu); 0.303 and 0.481 (Fe); 197 and 381 (K); 166 and 35.7 (Mg); 0.183 and 1.15 (Mn); 68.6 and 0.433 (Na); 54.1 and 62.2 (P) and 0.197 and 0.261 (Zn) for conventional and organic cultivars, respectively. Average centesimal concentrations in conventional and organic cultivars (in %), were: 72 and 72 (moisture); 0.87 and 0.90 (ashes); 1.5 and 1.4 (proteins); 0.63 and 0.54 (lipids) and 24.8 and 23.9 (carbohydrates).

Rose (Rosa spp.) petals have been used for the preparation of new cooking recipes, due to their sensory properties. In this paper were evaluated the micro (Co, Cu, Fe, Mn, Mo, Ni and Zn), macro (Ca, Mg, Na and P) and toxic elements (As, Cd and Cr) of organic cultivation rose by ICP OES and ICP-MS. The bioactive compounds (total phenolics, total flavonoids, total anthocyanins and antioxidant capacity in DPPH) were determined by UV-VIS spectrophotometry. Chemometric tools were used in method optimization, such as full factorial design for acid digestion and Box-Behnken design for total phenolics, in addition to the application of Artificial Neural Networks with Kohonen Neural Network for bioactive compounds. The application of PCA and HCA showed that the mineral composition of rose petal samples had differences between summer and winter. The accuracy of the method was confirmed by the analysis of three certified reference materials: apple leaves (1515), spinach leaves (1570a) and peach leaves (1547), from the National Institute of Standards and Technology (NIST). Digestion efficiency was evaluated by residual carbon content. The developed methods were promising to evaluate the minerals, toxic elements and bioactive compounds in rose petals, and the results indicate that they can be added as a potential nutritional supplement in the human diet.

This study proposes a preliminary assessment of the homogeneity and stability through digital image acquisition of a candidate for mechanically processed pumpkin seed meal reference material, exploring the concepts of homogeneity curve and the analysis of texture characteristics by Continuous-Level Moving Block through Robust Principal Component Analysis. This innovative methodology allowed us to examine the percentage of homogeneity in a set of samples, revealing an average of 41% with only one outlier in relation to the entire sample, indicating low homogeneity. In the stability study carried out after storing samples for 12 months at different temperatures, 83% of the samples were considered regular and 17% were outlier, which means that most of them were considered stable. Therefore, this methodology is useful for screening samples for homogeneity, by textural analysis, and detected non-homogeneity can be corrected in advance for quantification by standard protocols.

The development of a collaborative study as a requirement for the preparation of a laboratory reference material candidate is reported in this paper. The evaluation was performed by 13 laboratories invited to quantify the calcium, potassium, magnesium, phosphorus, copper, iron, manganese and zinc; 8 of them presented results for all the analytes under investigation. The data were statistically analyzed by applying the z-score robust technique as recommended by ISO Guide 35. For the potassium element, laboratories 4 and 13 presented questionable results. Laboratory 5 proved to be unsatisfactory for calcium and zinc. ANOVA-PCA and DD-SIMCA were also applied to evaluate stability and interlaboratory studies results, respectively. It has been demonstrated that multivariate data analysis can be successfully applied as an alternative method to the recommendations made by ISO 13528 and ISO Guide 35 with defined confidence intervals.

This work proposes the use of high performance liquid chromatography coupled to inductively coupled plasma mass spectrometry (HPLC-ICP-MS) for simultaneous speciation of arsenic and chromium in iron supplements used for the treatment of anemia. The sample preparation procedure recommended for the total determination of arsenic and chromium was established using acid digestion in a microwave assisted oven. For speciation analysis, however, the microwave-assisted extraction procedure involved the use of water as extraction solvent at 90 °C for 30 min. The chromatographic separation was performed using a mobile phase containing 1.0 mM tetrabutylammonium hydroxide (TBAH), 0.7 mM ethylenediaminetetraacetic acid (EDTA) and 5% methanol at pH 7.2. Helium was used in the collision cell for elimination of the interferences. Under optimized conditions, the separation and detection of the As(III), As(V), Cr(III) and Cr(VI) species can be performed in 5 min, permitting their quantification with the external calibration technique with standards prepared in the mobile phase. The limits of quantification obtained were 0.008, 0.010, 0.5 and 0.14 µg g−1, for As(III), As(V), Cr(III) and Cr(VI), respectively. The accuracy of the method was evaluated and confirmed by addition/recovery tests. The recoveries obtained varied from 81% to 110%. The proposed method was applied to the speciation analysis of arsenic and chromium in commercially available iron supplements acquired in several cities in Brazil and Spain. The content of the species ranged from 0.01 to 1.3 µg g−1 for arsenic, and from 0.4 to 61.2 µg g−1 for chromium.

A reliable, simple and accurate method was developed to simultaneously determine 13 bioactive phenolic compounds in guava ( Psidium guajava L.) by reversed-phase high-performance liquid chromatography with diode array detection (HPLC-DAD). The proposed methodology was fully validated and proven successful in the analysis of methanolic extracts of lyophilized whole guavas at two maturation stages: green and ripe. The quantification of phenolic compounds revealed that the highest concentrations (mg 100 g − 1 DW) in all samples were: gallic acid (2.43–7.28); chlorogenic acid (1.83–10.75); ellagic acid (5.72–30.60); catequin (1.09–13.09) and rutin (5.09–45.02). Total polyphenol content (55–516 mg GAE 100 g − 1 ); total flavonoid content (35.26–75.19 mg QE 100 g − 1 ); antioxidant capacity in DPPH and ABTS assays (5.22–5.62 and 17.63–18.74 TEAC·100 g − 1 DW, respectively) were also determined, and can be related to the diverse range of phenolics detected. The results (TPC and TFC) for most green samples were higher than for ripe samples. There were no significant differences for antioxidant activity between the samples analyzed. Applying Pearson correlation test, the results indicate a significant positive correlation between the variables. The exploratory evaluation of guava samples was performed through Principal Component Analysis (PCA). The bioactive phenolics that most contributed to the variability between green and ripe fruits were: rutin, catequin, and: elagic, syringic, cafeic, transcinamic and p-coumaric acids. Neural Network Analysis (NNA) was applied for more insights about cluster separation and the influence of each variable. The parameters evaluated for NNA indicated good separation in two clusters: green and ripe fruits.

Submitted by Gisele Mara Hadlich (gisele@ufba.br) on 2019-01-14T01:47:21Z No. of bitstreams: 1 Determination and evaluation of the mineral composition of breadfruit (Artocarpus altilis) using multivariate analysis technique.pdf: 533500 bytes, checksum: 2126fa71b9fb9c9133a217f866568538 (MD5) Approved for entry into archive by Jessica Alves (alves.jessica@ufba.br) on 2019-03-20T13:47:47Z (GMT) No. of bitstreams: 1 Determination and evaluation of the mineral composition of breadfruit (Artocarpus altilis) using multivariate analysis technique.pdf: 533500 bytes, checksum: 2126fa71b9fb9c9133a217f866568538 (MD5) Made available in DSpace on 2019-03-20T13:47:47Z (GMT). No. of bitstreams: 1 Determination and evaluation of the mineral composition of breadfruit (Artocarpus altilis) using multivariate analysis technique.pdf: 533500 bytes, checksum: 2126fa71b9fb9c9133a217f866568538 (MD5) Breadfruit is a fruit originated from South Pacific and afterward it was widespread in rest of Oceania. In Brazil it is known as “fruta pão” and has been consumed mainly by humble people. In home use, breadfruit has been consumed cooked, fried or roasted. Industrially, it has been employed to prepare breads and flours. In the present paper, the mineral composition of breadfruit (Artocarpus altilis) was determined and evaluated. Raw breadfruit samples and cooked using domestic methods as boiling and microwave heating were digested in acid media and the elements potassium, calcium, phosphor, magnesium, iron, sodium and manganese were determined employing inductively coupled plasma optical emission spectrometry (ICP OES). Cadmium and lead were also determined using graphite furnace atomic absorption spectrometry (GFAAS), but the concentrations found were lower than the limits of quantification for these elements. Eleven samples were acquired in several cities from Bahia state, Brazil. All these samples were analyzed in triplicate. The data obtained were evaluated employing the multivariate analysis techniques: Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA). Both techniques showed that the cooking methods using microwave heating and boiling cause loss of the nutrients. PCA also evidenced that the element concentrations in the samples cooked using microwave heating are higher than in the samples cooked by boiling using stove. The average concentrations of the determined elements (expressed as mg 100 g−1 of sample) in raw samples were as follows: 269.4 for potassium, 40.97 for phosphorus, 26.32 for calcium, 24.35 for magnesium, 1.41 for sodium, 0.1891 for iron and 0.0381 for manganese. Microchemical Journal

This review covers the application of multivariate designs and mathematical-statistical techniques to establish optimal conditions of the analytical methods for elemental analysis using inductively coupled plasma optical emission spectrometry (ICP OES) as a detection technique. The main experimental designs, such as two level factorial design, central-composite design, Box Behnken design, Doehlert design and mixtures designs are presented and discussed in connection to the method stage, in which multivariate designs were used in the instrumental variable optimization related to plasma, sample decomposition, preconcentration stage and sample introduction technique.

The present work reports the development of an analytical method for the determination of trace amounts of Cd and Pb in crude palm oil using graphite furnace atomic absorption spectrometry (GF AAS) after extraction induced by emulsion breaking (EIEB). The method was based on an oil-in-water emulsion preparation to promote a high contact area between the sample drops and the acid extractant solution. Emulsification was assisted by ultrasound energy using HNO3 and Triton X-114 surfactant solutions to increase the efficiency of the extraction. Afterwards, the emulsion was broken by heating, and the acid aqueous phase in the bottom of conical glass tubes was collected for the determination of metals by GF AAS. Cadmium and lead extraction was simultaneously optimized using Doehlert design and desirability function. The best extractions were achieved using a sonication time of 18 min, a HNO3 concentration of 2.0 mol L−1 and a surfactant concentration of 4.4% (v v-1) at a breaking temperature of 90 °C. The developed method presented quantification limits of 0.17 and 0.13 μg kg−1 and precisions (repeatability,%RSD, 10.8 μg kg−1) of 1.8 and 5.4% for Cd and Pb, respectively. Addition/recovery tests gave results between 88.5% and 112%. The amounts of Cd and Pb in the analyzed samples ranged from 1.5–2.5 and 2.53–6.76 μg kg−1, respectively.

In this work, a homogeneity study of a corn flour reference material candidate for inorganic analysis is presented. Seven kilograms of corn flour were used to prepare the material, which was distributed among 100 bottles. The elements Ca, K, Mg, P, Zn, Cu, Fe, Mn and Mo were quantified by inductively coupled plasma optical emission spectrometry (ICP OES) after acid digestion procedure. The method accuracy was confirmed by analyzing the rice flour certified reference material, NIST 1568a. All results were evaluated by analysis of variance (ANOVA) and principal component analysis (PCA). In the study, a sample mass of 400 mg was established as the minimum mass required for analysis, according to the PCA. The between-bottle test was performed by analyzing 9 bottles of the material. Subsamples of a single bottle were analyzed for the within-bottle test. No significant differences were observed for the results obtained through the application of both statistical methods. This fact demonstrates that the material is homogeneous for use as a laboratory reference material.

Cassava leaves (Manihot esculenta) are used to prepare “manicoba”. Of indigenous origin, this dish is considered of high nutritional value for Brazilian cuisine. However, the leaves should be processed in order to eliminate the hydrocyanic acid that they contain. In this work, the centesimal composition, physical-chemical characteristics, micro (Cu, Mn, and Zn) and macronutrients (Ca, K, and Mg) were evaluated in cassava leaves cultivates in the State of Bahia, Brazil, according to different types of processing the leaves. The centesimal composition and physical-chemical characteristics were determined employing methodologies described by Adolfo Lutz Institute. The determination of the mineral composition was performed employing ICP OES, after microwave-assisted acid decomposition procedure of leaves samples. The accuracy of the method was confirmed by the analysis of spinach and apple leaves certified reference materials (NIST 1570a and NIST 1515) from the National Institute of Standards and Technology (NIST). Residual carbon content was evaluated by ICP OES. The samples were evaluated raw and after the cooking and fermentation processes. Losses of nutrients occurred after the cooking and fermentation processes. Average mineral concentrations in raw, cooked and fermented samples (in mg 100 g−1) were: 502.0, 487.6 and 458.4 for Ca; 40.1, 37.6 and 29.1 for Cu; 781.2, 180.9 and 57.8 for K; 150.3, 133.2 and 111.4 for Mg; 20.3, 18.8 and 15.7 for Mn; and 5.01, 4.64 and 4.02 for Zn. Average centesimal composition concentrations in raw, cooked and fermented samples (in % m m−1) were: 29.9, 12.2 and 11.1 for moisture content; 2.03, 0.66 and 0.54 for ashes; 10.2, 4.66 and 4.64 for proteins; 1.64, 1.88 and 1.07 for lipids; 56.3, 80.6 and 82.6 for carbohydrates; and 281, 358 and 359 for calorific value. Average physical-chemical characteristics values in raw sample were: 0.16–1.17% (titratable acidity); 5.91–6.41 (pH); 2.75–3.27 °Brix (soluble solids); 2.75–3.27 (ratio) and 4.53–38.7 mg 100 g−1 (vitamin C). The results were evaluated using multivariate analysis (PCA and HCA), in which there is a tendency of separation of the samples in groups, according to the treatment type that the samples were submitted.

Okra ( Abelmoschus esculentus L .) is a plant native to Africa. It was introduced to Brazil with the slave trade and spread to all regions, including the state of Bahia, northeastern Brazil. In this work, the mineral content of raw and cooked okra marketed in the state of Bahia, of both conventional and organic cultivars was determined. The results were evaluated using multivariate analysis. The samples were digested in a heating block using nitric acid and hydrogen peroxide, and analysed using inductively coupled plasma optical emission spectrometry (ICP OES). The accuracy of the method was confirmed using a standard reference material, tomato leaves (NIST 1573a). Average mineral concentrations in raw and cooked okra (in mg/100 g), were: 366 to 325 (Ca); 0.102 to 0.052 (Cu); 267 to 97.7 (K); 45.3 to 18.3 (Mg); 18.3 to 7.00 (Na); 44.5 to 25.8 (P); and 0.233 to 0.094 (Zn). Raw and cooked samples tended to separate in principal component analysis (PCA) and hierarchical cluster analysis (HCA). The elements that contributed most for the variability between raw and cooked samples are: K, P, Mg, Cu, Na and Zn, with minor contributions from Ca.

This paper describes the determination and evaluation of the mineral composition (calcium, magnesium, iron, manganese and zinc) of kale (Brassica oleracea L. var. acephala DC.) grown in soils within four cities in Bahia State, Brazil. The sampling process was performed during the summer and winter. Samples were digested with concentrated nitric acid and a digestion pump. Analyses were performed with inductively coupled plasma optical emission spectrometry (ICP OES) and the accuracy was confirmed with a certified reference material of apple leaves furnished by the National Institute of Standard and Technology. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) revealed different mineral compositions of the samples collected in the summer and winter. Samples collected in the winter have a higher concentration of micronutrients (iron, zinc and manganese) and macronutrients (calcium and magnesium). The average contents (wet weight and mg per 100 g) for the winter and summer were 551 and 535 for calcium; 117 and 106 for magnesium; 2.13 and 1.48 for iron; 2.63 and 1.95 for zinc and 2.05 and 1.34 for manganese, respectively. These results are in agreement with values previously reported in the literature.

The development of a homogeneity study during the preparation of a wheat flour laboratory reference material (LRM) for use in the quantification of metals and metalloids is reported. Inductively coupled plasma optical emission spectrometry (ICP OES) was used with validation performed using a certified reference material of wheat flour furnished by the National Institute of Standards and Technology (NIST). Copper, iron, manganese, phosphor, strontium and zinc were studied in a within-bottle homogeneity test whereas barium, copper, iron, zinc, manganese, strontium, phosphor and calcium were included in a between batch homogeneity study. Standard univariate analysis of variance (ANOVA) was performed for all analytes. Furthermore an alternative multivariate analysis for homogeneity is proposed by performing ANOVA of principal component scores and by inspection of principal component score graphs and hierarchical cluster analysis dendrograms. The ANOVA F -tests performed on both, the univariate and multivariate parameters, were not significant at the 95% confidence level and indicated homogeneous wheat flour samples. A 10 kg amount of material was processed, which was distributed in 100 bottles, each containing 100 g. For the between-bottle homogeneity test, three replicates were taken from each of 10 bottles selected of the 100 bottles obtained. The results were evaluated using an F-test , which demonstrated no significant difference for the between-bottle results. It is indicative that this material is homogeneous. Afterwards, the influence of the sample mass on the homogeneity of the material was also evaluated by quantification of the elements for 100, 300, 500, 700 and 1000 mg sample masses with all the experiments being performed in triplicate. The F -test was also used for evaluation of these results and demonstrated that the material is homogeneous for masses taken in the 100 to 1000 mg range. All these results were further evaluated employing the principal component analysis (PCA) and hierarchical cluster analysis (HCA) multivariate techniques. Both techniques also demonstrated that the material is perfectly homogeneous for use as laboratory reference material.