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During the analysis of the biological, geological, brines and seawater samples, the matrix can have a significant effect on the quality of the obtained results. Due to matrix effect, the reduction or enhancement of the instrument signal is observed, causing severe interferences, likely occurring both types of proportional and constant systematic errors. While factorial design is used in order to optimize technological processes, methodology, yield of different chemicals, rarely is found used in analytical chemistry for the assessment of matrix interferences. Normally, the study of interference is performed by univariate method, which is not economic and do not take into account the interaction between factors. Our experience has shown that factorial design is a very useful tool to point out the influence of constituents of the matrix on the instrumental signal of the solutes. The assessing of the effects of Cu, Cd and exposure period on metallothionein production in gills of mussel by this technique has been studied as well. In this work are shown applications of factorial design on study of matrix interferences in seawater, brines and soil samples. The aim of this research was to underline the philosophy of assessing effects of matrix constituents, which helps to get accuracy results. The techniques used for lithium determinations in brines samples were atomic absorption spectroscopy (emission mode). In brines major constituents of matrix are Na, K, Ca and Sr. In soil, in which Al and Fe are abundantly found, the determination of fluoride by ion selective electrode (ISE) was applied. The ratio of the constituents of the prepared samples have been according the concentrations found in natural samples. Previously, some hundreds natural samples of underground brines, in contact with oil from Albanian oilfield, have been analyzed for trace metals by AAS. The regression coefficients found in the models demonstrated a significant interference of Fe, with an even more pronounced interference for Al during ISE determination of fluoride. While for lithium determination by AAS, Na and Ca showed significant interferences. Following the application of standard addition method is found the source type of systematic error, constant or proportional. From the factorial design plans, applied for hard matrix samples, it is concluded, that the regression coefficients found in the models, demonstrated significant interferences of studied factors, including their interaction terms. Clearly factorial design has shown significant advantages over classical method of studying interferences. Therefore, we strongly recommend it in the analysis of complicated samples. [ABSTRACT FROM AUTHOR]

A simple, selective, highly sensitive and accurate procedure for the determination of trace amounts of copper has been developed based on solid-phase spectrophotometry. Copper reacts with 5-(2-benzothiazolylazo)-8-hydroxyquinoline (BTAHQ) to give a complex with high molar absorptivity (3.17 × 107 L mol−1 cm−1, 3.07 × 108 L mol−1 cm−1, 1.22 × 109 L mol−1 cm−1, and 1.80 × 109 L mol−1 cm−1), fixed on a Dowex 1-X8 type anion-exchange resin for 10 mL, 100 mL, 500 mL, and 1000 mL, respectively. The absorbance at 667 nm and 800 nm packed in a 1.0 mm cell was measured directly. Calibration is linear over the range 0.2–3.7 µg L−1 with RSD of < 1.28 % ( n = 10). The detection and quantification limits of the 500 mL sample method are 79 ng L−1 and 260 ng L−1 when using 60 mg of Dowex 1-X8. For a 1000 mL sample, the detection and quantification limits are 67 ng L−1 and 220 ng L−1 using 60 mg of the exchanger. Increasing the sample volume can enhance the sensitivity. The proposed method was applied to the determination of copper in different environmental water samples (tap, pit, spring, and river), food products (rice, corn flour, and tea), and mushrooms, using the standard addition technique. [ABSTRACT FROM AUTHOR]

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