Exploratory analysis in the evaluation of stress due to aluminum presence in Physalis angulata L. and multielement determination by microwave-induced plasma optical emission spectrometry (MIP OES).

The present work aimed to analyze the mineral nutrition of Physalis angulata L. under stress by aluminum in the nutrient solution. The treatments consisted of five different concentrations of aluminum in the nutrient solution (0, 0.04, 0.08, 0.12, and 0.16 mmol L-1) in the AlCl3 form. The plants were exposed to Al for 30 days. Subsequently, nutritional and aluminum analyses were performed on plant tissue. The data were submitted to analysis of variance (p < 0.05), and, in case of significance, the regression study was performed as well as hierarchical cluster analysis (HCA) and principal component analysis (PCA) were used. The formation of four groups occurred, where we can observe the similarity and differences in the treatments between them. The separation of the treatments into groups reflected the heterogeneity of the treatments about the aluminum levels in the nutrient solution, evidencing its phytotoxicity level in Physalis angulata plants. Among the analyzed variables, P, K, Ca, Mg, Fe, Mo, and Zn were the most influential ones demonstrated by principal component analysis (PCA). The stress of 0.16 mmol L-1 of Al increased the phosphorus contents in the stems and roots and the potassium, copper, and molybdenum contents in all parts of the plants. In contrast, Al reduced the levels of calcium, magnesium, iron, and zinc in P. angulata plants. Iron being the micronutrient that showed the largest reduction, followed by zinc in the leaves. The highest levels of aluminum were found in the roots.

Determination of mercury in phosphate fertilizers by cold vapor atomic absorption spectrometry.

In this paper, a method for the determination of mercury in phosphate fertilizers using slurry sampling and cold vapor atomic absorption spectrometry (CV QT AAS) is proposed. Because mercury (II) ions form strong complexes with phosphor compounds, the formation of metallic mercury vapor requires the presence of lanthanum chloride as a release agent. Thiourea increases the amount of mercury that is extracted from the solid sample to the liquid phase of the slurry. The method is established using two steps. First, the slurry is prepared using the sample, lanthanum chloride, hydrochloric acid solution and thiourea solution and is sonicated for 20 min. Afterward, mercury vapor is generated using an aliquot of the slurry in the presence of the hydrochloric acid solution and isoamylic alcohol with sodium tetrahydroborate solution as the reducing agent. The experimental conditions for slurry preparation were optimized using two-level full factorial design involving the factors: thiourea and lanthanum chloride concentrations and the duration of sonication. The method allows the determination of mercury by external calibration using aqueous standards with limits of detection and quantification of 2.4 and 8.2 µg kg(-1), respectively, and precision, expressed as relative standard deviation, of 6.36 and 5.81% for two phosphate fertilizer samples with mercury concentrations of 0.24 and 0.57 mg kg(-1), respectively. The accuracy was confirmed by the analysis of a certified reference material of phosphate fertilizer that was provided by the National Institute of Standards & Technology (NIST). The method was applied to determine mercury in six commercial samples of phosphate fertilizers. The mercury content varied from 33.97 to 209.28 µg kg(-1). These samples were also analyzed employing inductively coupled plasma mass spectrometry (ICP-MS). The ICP-MS results were consistent with the results from our proposed method.