mL Of Aqua Regia Research Articles

The Impact of Galena Mining in North-Eastern Nigeria on Nearby Food Crops

Aims: To investigate and evaluate trace elements concentration in soils and bioaccumulation on food crops grown on agricultural fields around galena mine area, Wukari, north eastern Nigeria.
 Study Design: The studied area is situated in the northwestern part of Wukari Local Government Area of Taraba State, North-East Nigeria. The hydrology of the area is conducive for the cultivation of crops and fresh water for fishing. The soils and food crops samples were collected in the month of May, 2018.
 Methodology: Edible parts of plants such as leaf, stem and seed were collected from Soybeans (Glycine max), Guinea corn (Sorghum bicolor), Millet (Penniselum typhoides), Spinach (Amaranthus) and Tomato (Lycosipinus esculentum). A 1.00 g of the finely ground soil samples were digested with 10 mL of aqua regia (a mixture of 1:3 HNO3/HCl v/v) at 70°C on hot plate for 3 hours in a fume hood and 1.00 g of each sieved plant samples were digested with 10 mL mixture of HNO3: HCIO4 in the ratio 5:1 at 90°C for 30 minutes in a fume cupboard.
 Results: The concentrations (µg/g DW) of the trace elements in soil are in the order Mn > Fe > Se > Pb > Cr > Cu > Al > As. The bio-accumulation of trace elements in all food crops were in the range: Se (0.250 – 20.88 µg/g DW), Al (0.250 – 0.980 µg/g DW), As (0.070 – 0.620 µg/g DW) and Pb (0.020 – 0.090 µg/g DW). Cr, Cu, Pb, Mn concentrations in food crops were above FAO/WHO permissible limits of 2.30, 40.0, 0.30, 500 µg/g DW respectively.
 Conclusion: The Health Risk Index of As, Cr and Fe in spinach and Guinea corn were > 1. The study revealed that food crops grown on farmlands around mining areas are not safe for consumption.

Desarrollo y validación de un método ambientalmente amigable para determinación de metales pesados en pastos

Los metales pesados son peligrosos para los seres vivos y el medio ambiente, pues no pueden ser degradados y pueden llegar a los seres humanos a través la cadena trófica, por lo tanto, su determinación en diferentes matrices para consumo humano y animal, es de vital importancia. La metodología más utilizada para su extracción, es cenizas, la cual conlleva a tiempos largos de análisis y elevado consumo de energía, por esta razón, en el presente trabajo se desarrolló y validó un método ambientalmente amigable para la digestión y extracción de Cd+2 y Pb+2 en pastos, utilizando ultrasonido y espectroscopia de absorción atómica. Se evaluaron diferentes variables que afectan la digestión, como posición en el ultrasonido, peso de muestra, solvente, volumen del solvente, tiempo de sonicación y tipo de recipiente, en muestras de pastos dopadas con los metales, teniéndose como variable de respuesta, el porcentaje de recuperación. Las condiciones para extraer Cd+2 y Pb+2 en estas pasturas, fueron: 0,50g de tejido vegetal; 3,00mL de HCl:HNO3-3:1 expuestos 60min al ultrasonido, en tubos de vidrio cónicos. Este procedimiento mostró un comportamiento lineal en el rango de 0,50 - 8,00mg/Kg con R2 de 0,99 tanto para Cd como para Pb. Los límites de detección y cuantificación, fueron 0,25 y 0,43mg/Kg para Cd; 0,22 y 0,37mg/Kg para Pb. La metodología propuesta, se comparó con la técnica clásica y permitió determinar niveles trazas de estos metales tóxicos, en forraje proveniente del Magdalena medio, con porcentajes de recuperación de97,54 y 98,62%, respectivamente.

Levels of selected essential and non-essential metals in seeds of korarima (Aframomum corrorima) cultivated in Ethiopia

SummaryThe levels of essential (Ca, Mg, Fe, Zn, Cu, Co, Cr, Mn and Ni) and non-essential (Cd and Pb) metals were determined by flame atomic absorption spectrometry in samples of korarima (Aframomum corrorima) seeds and the corresponding soils collected from southern and southwestern Ethiopia. A wet digestion procedure involving the use of 3 mL of HNO3 (69-72%) and 1 mL of HClO4 (70%) were used to solubilize the metals from the korarima seed samples, and a modified aqua regia (HCl:HNO3) reagent with added hydrogen peroxide (6 mL of aqua regia and 1.5 mL of H2O2) was used for the soil samples. The levels of the nutrients in the korarima seed samples were in the following ranges: Ca (1794-2181); Mg (1626-2067); Mn (141-180); Fe (37-46); Zn (12-18); Ni (6.6-8.5); Cu (5.8-8.3); Cr (3.8-5.8) and Co (2.0-2.3) in µg g–1, respectively. The concentration of non-essential cadmium was in the range from 0.9-1 µg g–1 while that of lead was below the detection limit of the method. There was good correlation between the levels of some metals (Ni, Fe, Cd, Ca, Cu, Mg) in the korarima seeds and soil samples but poor correlation between other metals (Cr, Zn, Mn, Co).

Phytochemical screening of some indigenous medicinal plant species used in the management of diabetes mellitus in Ghana

This study was conducted to screen the phytochemical constituents and determine the levels of the major and trace elements of three medicinal plants used for the treatment of diabetes mellitus namely; Bridelia ferruginea, Lagerstroemia speciosa and Morus Alba. The air dried leaves of the plants were subjected to soxhlet extraction using ethanol. The crude extracts obtained were subjected to screening for their phytochemical constituents such as alkaloids, tannins, terpenoids, reducing sugars, flavonoids, saponins, anthraquiones, coumarins, emodols, carotenoids and steroids using various standard methods and reagents. Trace metals in the three medicinal plants were also quantitatively analyzed using Flame Atomic Absorption Spectroscopy. A wet digestion procedure involving the use of 4 ml of perchloric acid and 10 ml of aquaregia was adopted to digest the medicinal plants. Anthraquinones, sterols, tannins, terpenoids, flavonoids, alkaloids, saponins, coumarins and reducing sugars were identified in the leaves of all the three plants. However, emodols were absent in all the plants but carotenoids were absent in only B. ferruginea. Elemental concentrations of some of the elements were obtained from the leafy materials in varying quantities. Ten heavy metals (Cd, Cr, Co, Cu, Fe, Pb, Mn, Ni, Zn, and V), two alkali metals (K and Na) and three alkaline earth metals (Ca, Mg and Al) and two halogens (Cl and Br) were quantitatively analysed. The anti-diabetic properties of the plant extracts could be attributed to the presence of steroids, triterpenes and alkaloids. In general the order of concentration of toxic metals in the medicinal plants was found to follow the order Fe > Mn > Zn > Cu > Ni > V > Pb > Co > Cr > Cd. Sodium content was found to be very high in L. speciosa while chlorine content was found to be very high in B. ferruginea.

Study on the Interference of Iron, Aluminium and Silicon on the Atomic Absorption Spectrometric Determination of Mangan in Laterite Mineral

Interference of iron, aluminum and silicon on the determination of mangan in laterite mineral by atomic absorption spectrometry has been investigated. Dissolution of laterite mineral into solution have been carried out by wet method destruction using combination of 7 mL of aquaregia, 7.5 mL of concentrated perchloric acid and 9 mL of fluoride acid 48% In sealed teflon flask heated at temperature of about 110 °C for 3 hours to determine the content of Mn element in laterite mineral directly. Interference of these three metals were carried out by evaluating the differences of Mn absorbance at wavelength 279.50 nm and slit width 0.2 nm between the solutions containing mangan only and those containing the some amount of mangan together with the interfering elements at those concentration range in laterite mineral. The result showed that both iron at concentration of 100 ppm until 500 ppm and aluminum at concentration at 3 ppm until 15 ppm caused significant and non-linear interference on the determination of Mn 2 ppm. Interference of iron was effectively eliminated by releasing action of aluminum. The signal depression reductional decrease due to 234 ppm of silicon on the determination of Mn 2 ppm can be eliminated by adding 2.30 mL of CaCl2 0.2% (m/v) into these solution. The content of Mn in the laterite mineral after and before adding of CaCl2 into solution were 2407.04 ± 59.26 μg g-1 and 2311.76 ± 23.61 μg g-1, respectively. This result was significantly different at confidence level 95% as shown by the value of tcalculated=4.91 that was higher than ttable=4.30.

Determination of Se in biological samples by axial view inductively coupled plasma optical emission spectrometry after digestion with aqua regia and on-line chemical vapor generation

A simple and fast method for the determination of Se in biological samples, including food, by axial view inductively coupled plasma optical emission spectrometry using on-line chemical vapor generation (CVG–ICP OES) is proposed. The concentrations of HCl and NaBH 4, used in the chemical vapor generation were optimized by factorial analysis. Six certified materials (non-fat milk powder, lobster hepatopancreas, human hair, whole egg powder, oyster tissue, and lyophilised pig kidney) were treated with 10 mL of aqua regia in a microwave system under reflux for 15 min followed by additional 15 min in an ultrasonic bath. The solutions were transferred to a 100 mL volumetric flask and the final volume was made up with water. The Se was determined directly in these solutions by CVG–ICP OES, using the analytical line at 196.026 nm. Calibration against aqueous standards in 10% v/v aqua regia in the concentration range of 0.5–10.0 µg L − 1 Se(IV) was used for the analysis. The quantification limit, considering a 0.5 g sample weight in a final volume of 100 mL − 1 was 0.10 µg g − 1. The obtained concentration values were in agreement with the total certified concentrations, according to the t-test for a 95% confidence level.

An ultrasound-assisted digestion method for the determination of toxic element concentrations in ash samples by inductively coupled plasma optical emission spectrometry

A method of ultrasound-assisted digestion followed by inductively coupled plasma optical emission spectrometry (ICP-OES) used for the determination of toxic element concentrations (arsenic, barium, cobalt, copper, lead, nickel, strontium, vanadium and zinc) in ash samples was developed. All the measurements were performed in robust plasma conditions which were tested by measuring the Mg(II) 280.270 nm/Mg(I) 285.213 nm line intensity ratios. The highest line intensity ratios were observed when a nebulizer gas flow of 0.6 L min −1, auxiliary gas flow of 0.2 L min −1 and plasma power of 1400 W were used for radially viewed plasma. The analysis of SRM 1633b showed that the ultrasound-assisted method developed is highly comparable with the microwave digestion method standardized by the United States Environmental Protection Agency (EPA-3052). The ultrasound-assisted digestion with a digestion solution of aqua regia and hydrofluoric acid (HF) resulted in recovery rates of over 81%. One exception is arsenic which resulted in recoveries of about 60% only; however, it could be digested with good recovery (>90%) using a digestion solution of 5 mL of water and 5 mL of aqua regia. The major advantage of the ultrasound-assisted digestion over microwave digestion is the high treatment rate (30 samples simultaneously with a sonication time of 18 min).

Determination of trace amounts of platinum in manganese nodules by solvent extraction/graphite furnace AAS.

A rapid and precise method for the determination of Pt in manganese nodules and crusts is presented. The sample of 0.1 g was decomposed with 8 ml of aqua regia and filtered. The filtrate was evaporated to dryness, then dissolved in 20 ml of 20% tartaric acid with heating. After the addition of 0.5 ml iron (III) chloride solution (20 mg Fe/ml) and 0.5 ml of 1% 1, 3-diphenylthiourea in acetone, the mixture was heated for 5 min at about 100°C. The solution was extracted with 1 ml of 1, 2-dichloroethane for 5 min. Platinum in the organic phase was determined by graphite furnace AAS. The limit of detection is 0.05 ppm, and the relative standard deviation in the determination of 0.01 μg to 1.0 μg of Pt is 4 to 16%. The method is satisfactorily applied to USGS manganese nodule reference samples and the manganese nodules and crusts collected from the Central Pacific Ocean, Antarctic Ocean and Ogasawara Plateau.

Spectrophotometric determination of copper (II) with 6, 8, 15, 17-tetramethyl-dibenzo-5, 9, 14, 18-tetraazacyclotetradecen

6, 8, 15, 17-Tetramethyl-dibenzo-5, 9, 14, 18-tetraazacyclotetradecen was used to the determination of copper(II). The molar absorptivity of the 1: 1 copper chelate was 4.65×104l mo1-1 cm-1 at 381 nm. 3 ml of copper solution {(0.55)×10-5 M} was taken in a 10-ml volumetric flask, and 6 ml of 1.05×10-4 M reagent solution and 1 ml of 0.1 M acetate buffer solution (pH 4.7) were added. The mixture was filled up to 10 ml with water. After standing for 40 min at room temperature, the absorbance was measured at 381 nm against the reagent blank. Beer's law holds up to 1.8×10-5 M of copper. The presence of nickel (>10-6 M) and cobalt, iron (II) (_??_10-7 M) causes an error. By using the reagent, copper in aluminum alloy was determined. Aluminum samples {(20300)mg} were dissolved in 5 ml of aqua regia. Iron must be removed preliminary by extraction with MIBK at 6 M hydrochloric acid. Analytical results of copper in No. 1 AV859 (4.5%), No. 8 BV808 (2.7%), High power Al(D), Nikkei 1970 and HKI were 4.26%, 2.61%, 3.75%, 2.78% and 0.147%, respectively. And their recovery were 98.0%, 102.0%, 98.6%, 96.9% and 98.8%, respectively.

Masking of copper and tungsten in photometric determination of molybdenum in iron and steel

A method for the masking of copper and tungsten in the photometric determination of molybdenum in iron and steel with thiocyanate has been studied.The interfering copper is masked with thiourea solution and tungsten with phosphoric acid, although the former is unsuccessful in cases of stannous chloride reduction. The established method using L-ascorbic acid as a reducing agent is as follows. The sample (0.10.5g) is decomposed by treatment with perchloric acid, and evaporated to vigorous fumes. After cooling, it is diluted exactly to 100 ml with water, and an aliquot containing not more than 300μg of molybdenum is transfered to a 50 ml of volumetric flask. To it are added 10 ml of perchloric acid, 2 ml of sodium thiocyanate solution (30%), 10 ml of L-ascorbic acid solution (5%) and 5 ml of thiourea solution (10%) and it is diluted exactly to 50 ml with water. The absorbance is measured at 460 mμ against water.Samples containing large amounts of tungsten (for example, high speed steel) are decomposed by using 20 ml of aqua regia, 5 ml of phosphoric acid and 0.5 g of ammonium bifluoride, and evaporated to fumes with 20 ml of perchloric acid.

Photometric determination of phosphorus in niobium steel with molybdenum blue method

A photometric determination of phosphorus in niobium steel with molybdenum blue has been studied. The established procedure is as follows: 0.5 to 1 g of sample is decomposed with 10 ml of aqua regia, to this is added 10 to 15 ml of perchloric acid and it is evaporated until nitric acid is removed fuming perchloric acid vigorously.After cooling, the solution is diluted to approximately 50 ml with hot water, to this 10 ml of hydrofluoric acid (1+4) is added. It is then heated, and 4 g of boric acid is added and mixed.After masking interfering niobium, Fe3+ is reduced. by sodium bisulfite, and subsequently, a mixture of hydrazin sulfate and ammonium molybdate is added to the solution and finally it is colored by heating on either a water bath or a hot plate. The absorbance is measured at 825 mμ. The time required for the analysis is about 40 minutes.