Plant Digests Research Articles

Analysis of sulfur in soil and plant digests using methane as a reaction gas for ICP-MS

Quantitation of sulfur (S) is vitally important for analysis of agricultural soil and plant samples due to the requirement of S in living organisms. Although inductively coupled plasma mass spectrometry (ICP-MS) is a commonly used and robust instrument for multi-elemental detection, S is usually analysed by ICP-optical emission spectroscopy (OES) since S quantitation poses a particular challenge for ICP-MS due to interferences on all S isotopes. The requirement for analysis by two instruments increases time and cost for sample analysis, hence analysis by one instrument is desirable. The use of reaction gases in ICP-MS can improve the performance by shifting S to a mass for detection where no interference is present. This work explored the potential of methane as a reaction gas for analysis of S in soil and plant samples to give users an alternative option to oxygen. The product ion clusters CH2SH+ were monitored (m/z 47 and 49 on ICP-MS and with mass shift of +15 from Q1 → Q2 using 32 → 47 and 34 → 49 on triple quadrupole ICP-MS). As expected, triple quadrupole ICP-MS performed better than single quadrupole ICP-MS containing a reaction cell due to the ability to preselect the m/z of choice and remove ions that may react with methane in the reaction cell. The method detection limit (MDL) was 150 mg kg−1 S for plants and 53 mg kg−1 S for soils which is fit for requirements. This is the first-time methane has been reported as a reaction gas for analysis of S and shows promising results for agricultural samples when using a triple quadrupole ICP-MS. Results compared well to those obtained via the more commonly used ICP-optical emission spectroscopy (OES) method with results <20 % for all samples. Interlaboratory comparison samples were within 2 Z-scores of the consensus mean. In the absence of ICP-MS/MS, Q-ICP-MS with detection of cluster m/z 47 was deemed to be suitable for detection of S in plant samples, with acceptable MDL (250 mg kg−1 S), acceptable precision (<20 % RSD) and <20 % variation to the reported ICP-OES result.

RISK ASSESSMENT OF HEAVY METALS LEVEL IN SOILS AND FOOD CROPS AROUND A CERAMICS COMPANY IN AJAOKUTA, KOGI STATE, NORTH CENTRAL NIGERIA

Some metals associated with ceramics emission were determined in agricultural soil and leaves of maize and cassava around the vicinity of a major ceramic company. These metals are released during production process into the environment. Soil samples were collected at depth of 0-15 cm and 15-30 cm at certain distance (100 m, 200 m, 300 m and 400 m). Leaves of maize and cassava were collected around the soil samples area. Samples were collected to make a composite of 24 for both soil and leaves of crops respectively. Soil and plant digest were analysed by atomic absorption spectrometry. Result showed the range of metal (mg/kg) in topsoil Cd (1.00-8.25), Mn (3.75-62.0), Ni (11.0-46.3) and Pb (5.50-101.2). Corresponding value in subsoil was not significantly different (p&gt;0.05). The concentration of Mn in leaves of cassava is of concern especially if it will be used in the formulation of animal feed. The geo-accumulation (Igeo) of metals in soil revealed that the soil is slightly polluted. Uptake of metals into crops was low except Mn in cassava leaves. A health risk index (HRI) value for the food crops was &lt;1 except for Mn were HRI&gt;1 for cassava. Overall food crop consumption of the study area does not pose a potential threat at the moment.

GEO- AND PHYTO-MONITORING OF ENVIRONMENTAL IMPACT OF SMELTING INDUSTRY IN IKIRUN, NIGERIA

This research monitored the level of some heavy metals in soil and a plant species around iron smelting industry. The soil in different depths D1 (0 -10 cm), D2 (10 – 20 cm) and D3 (20 -30 cm) and plant (Tithonia diversifolia) known as Mexican sunflower were sampled in four soil sampling points (SSP) and plant sampling points (PSP) which are 50, 100, 150 and 200 m away from the industry. The concentrations of Cr, Cu, Fe, Pb and Zn in the soil and plant digest were determined using Atomic Absorption Spectroscopy (AAS). Some physicochemical properties like pH, electrical conductivity and organic matter were also measured. The result of the analysis of the heavy metals in the soil was in the sequence Fe &gt; Zn &gt; Cu &gt;Pb&gt; Cr at SSP1 SSP2 and SSP4 while Fe &gt; Zn &gt; Cu &gt; Cr &gt; Pb at SSP3. In the plant, the result showed the presence of these heavy metals except Pb which was not present in any sampling points. The concentration of iron (Fe) in the plant decreased away from PSP1 to PSP4 around the industry. The physicochemical properties like pH which influenced the availability of metals in soil were found to increase away from SSP1 to SSP4 and consequently its effect on the concentration of these heavy metals in plants, particularly for Fe and Zn. Although, heavy metals monitored were within the permissible limit of WHO except Fe in soil, the trend of their presence in

Biopower and biofertilizer production from organic municipal solid waste: An exergoenvironmental analysis

In this study, the environmental performance of a genset-coupled anaerobic digestion plant is analyzed at component-level using an exergoenvironmental method. The plant digests organic municipal solid waste (MSW) while producing two main products, i.e., biopower and biofertilizer. A comprehensive exergoenvironmental modeling of the plant is conducted using actual operating data in order to highlight the main units consuming exergy and causing environmental burdens. The exergoenvironmental indicators of all units of the system are computed by integrating exergy and environmental impact balances. The unitary exegetic environmental impact of biopower and biofertilizer are determined at 11.10 and 0.36 mPts/GJ, respectively. This means that the biofertilizer generation causes less environmental burden over the biopower due to the ease of its production. The highest total environmental impact rate (37.05 mPts/h) is caused by the genset followed far behind by the digester (8.56 mPts/h). Although the genset has the highest operation-related environmental impact rate (36.97 mPts/h), the highest component-related environmental impact rate (7.87 mPts/h) is associated with the digester. Therefore, the exergoenvironmental performance of the plant can be boosted by minimizing the rate of exergy dissipation of the genset while mitigating the environmental impacts related to the development and construction of the digester.

A solid phase extraction flow injection spectrophotometric method for the zinc determination in plants

A solid phase extraction flow injection system for the spectrophotometric determination of total zinc in plant digests was developed. Solid phase extraction was chosen as a strategy for zinc preconcentration and removal of some interferences. The determination of zinc was based on the colorimetric reaction with Zincon. As detection system, a multi-reflection flow cell coupled with a light emitting diode was used. The analytical characteristics of the methodology such as pH of standard/sample solution, nitric acid concentration, the placement of SPE column within the manifold and preconcentration flow rate were studied. The interference of some metals present in plants was also assessed. The limits of detection and quantification achieved were 0.04mgL−1 and 0.12mgL−1, respectively. The corresponding Zincon consumption was 0.17mg for each determination. The developed system was applied to plant digests and the results obtained were in agreement with those obtained with reference procedure.

Bioaccessibility of barium from barite contaminated soils based on gastric phase in vitro data and plant uptake

Barite contamination of soil commonly occurs from either barite mining or explorative drilling operations. This work reported in vitro data for barite contaminated soils using the physiologically based extraction test (PBET) methodology. The existence of barite in plant tissue and the possibility of 'biomineralised' zones was also investigated using Scanning Electron Microscopy. Soils with low barium (Ba) concentrations showed a higher proportion of Ba extractability than barite rich samples. Barium uptake to spinach from soil was different between short term spiking studies and field weathered soils. Furthermore, Ba crystals were not evident in spinach tissue or acid digest solutions grown in barium nitrate spiked soils despite high accumulation. Barite was found in the plant digest solutions from barite contaminated soils only. Results indicate that under the conservative assumptions made, a child would need to consume extreme quantities of soil over an extended period to cause chronic health problems.

Determination of carbon in digested samples and amino acids by inductively coupled plasma tandem mass spectrometry

Inductively coupled plasma mass spectrometer with a triple quadrupole (ICP-MS/MS) was employed to determine carbon from different sources such as plant digests, amino acids and peptides. Adequate precision, accuracy and sensitivity were obtained when using either single quadrupole or mass shift mode. Recoveries for carbon determination in plant digests ranged from 96 to 100%. Limits of detection were 0.42 and 0.17mgL−1 for 12C+ and 12C16O+, respectively, with calibration curves generated by using solutions prepared with oxalic acid. The determination of carbon and sulfur in amino acids and peptides showed that accuracy was better when measuring in O2 reaction mode. Additionally, C and S were simultaneously determined in cystine and glutathione by ICP-MS/MS mass-shift mode. The determination of carbon simultaneously with trace elements and target elements by ICP-MS makes this concept quite promising. Results demonstrated the potential of ICP-MS/MS for carbon determination.

Comparison of MP AES and ICP-MS for analysis of principal and selected trace elements in nitric acid digests of sunflower (Helianthus annuus)

The use of nitrogen as plasma gas for microwave plasma atomic emission spectroscopy (MP AES) is an interesting development in analytical science since the running cost can be significantly reduced in comparison to the inductively coupled argon plasma. Here, we evaluate the performance of the Agilent 4100 MP AES instrument for the analysis of principal metals (Ca, K, Mg, and Na), lithogenic metals (Al, Fe, and Mn) and selected trace metals (As, Ba, Cd, Co, Cr, Cu, Mo, Ni, Pb, V, and Zn) in nitric acid plant digests. The digests were prepared by microwave-assisted dissolution of dry plant material from sunflower (Helianthus annuus) in concentrated nitric acid. Comparisons are made with analysis of the same solutions with ICP-MS (Agilent 7500cx) using the octopole reaction system (ORS) in the collision mode for As, Fe, and V.The limits of detection were usually in the low µgL−1 range and all principal and lithogenic metals were successfully determined with the MP AES and provided almost identical results with the ICP-MS. The same applies for the selected trace metals except for As, Co and Mo where the concentrations were below the detection limit with the MP AES. For successful analysis we recommend that (i) only atom lines are used, (ii) ionization is minimized (e.g. addition of CsNO3) and (iii) the use of internal standards should be considered to resolve spectral interferences.

Determination of macro- and micronutrients in plant leaves by high-resolution continuum source flame atomic absorption spectrometry combining instrumental and sample preparation strategies

A method for determination of B, Ca, Cu, Fe, K, Mg, Mn, Mo, P, S and Zn in plant tissues by high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS) is proposed. This method is based on special features of HR-CS-AAS, such as side pixel registration, wavelength integrated absorbance, and molecular absorption bands, for determining macro- and micronutrients in foliar analysis without requiring several different strategies for sample preparation and adjustment of the analytes concentration ranges. Plant samples were analyzed and results for certified materials were in agreement at a 95% confidence level (paired t-test) with reference values. Recoveries of analytes added to plant digests varied within the 82–112% interval. Relative standard deviations ( n = 12) were lower than or equal to 5.7% for all analytes in all concentration ranges.

Interference Problems with Phosphoantimonylmolybdenum Colorimetric Measurement of Phosphorus in Soil and Plant Materials

A critical evaluation of potential chemical interference on a molybdenum‐based phosphorus (P) colorimetric method that is used widely for soil, plant, and water research was conducted. A wide variety of elements and compounds [aluminum (Al), manganese (Mn), iron (Fe), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), nitrate (NO3), and ethylenediaminetetraacetic acid (EDTA)] commonly found in these materials or extracting solutions used on them were shown to cause interferences. The interferences were subtle but complex, with changes to the rate at which the color product was formed and its apparent final chemical composition. There were interactions between the type of element or compound involved and the concentration of P in the test solution. The effect of nitrate on the color product could not be distinguished from the effect of the cation (K versus Na) with the nature of salt used because of the complexity of interacting factors. Increasing the time and temperature allowed the final absorbance for the color product to develop and produce more stable values, but the final absorbance was changed by the interfering element. Significant errors in P by the colorimetric method were observed in soil extracts and plant digests, showing that the resulting values were not accurate. Historic data using values measured by this method need re‐evaluation. Alternative methods need examination to select for accurately measuring the P content to refine our knowledge of the role of this important element in soil, plant, and water studies.

Spectrophotometric flow-injection determination of copper and nickel in plant digests exploiting differential kinetic analysis and multi-site detection

A novel strategy for implementing differential reaction-rate methods in flow-injection analysis is proposed and applied to the determination of copper and nickel in plant digests using 2-(5-brom-2-pyridylazo)-5-(diethylamino)-phenol (Br-PADAP) as the color-forming reagent. Multi-site detection is involved, therefore the flow cell is displaced between two monitoring sites, and the analytical signals refer to different conditions of sample dispersion, reaction development and timing. The system handles 20 samples h −1 and requires 0.32 mg Br-PADAP per determination. Signal additivity was evaluated within 98 and 102%, and linear responses ( r > 0.999; n = 6) were verified for both copper and nickel up to 0.80 mg l −1. Detection limits of 0.01 and 0.04 mg l −1 Cu and Ni were estimated by considering the highest concentration of the counter analyte. Results are precise (R.S.D. < 2%) and in agreement with ICP-OES (95% confidence level). Potentialities and limitations of the approach are discussed.

Fluidized beds in flow analysis: use with ion-exchange separation for spectrophotometric determination of zinc in plant digests

A novel strategy for utilization of solid reagents in flow analysis is proposed. Establishment of diffuse and reproducible geometry enables the solid particles to be maintained in constant floating, reflux, and circulating motion inside a mini-chamber. This is efficiently accomplished with pulsed flows, a characteristic of multi-pumping flow systems. Drawbacks inherent in solid-phase packed columns, for example backpressure, preferential pathways, swelling, etc., and some limitations inherent in immobilized reagents are minimised. Spectrophotometric determination of zinc in plants was selected as an application of the technique. Dowex 1-X8 anionic resin was kept freely inside a mini-chamber. Zinc chloro-complexes were adsorbed on the moving particles and derivatization with zincon was performed after elution. Analytical figures of merit and the potential and limitations of the approach are discussed.

Cloud-point extraction of molybdenum in plants and determination by isotope dilution inductively coupled plasma mass spectrometry

Molybdenum in plant digests was accurately determined by cloud point extraction and quantification by isotope dilution inductively coupled plasma mass spectrometry. Plant digests spiked with 98Mo received 8-hydroxyquinoline and the surfactant Triton X-100, attaining an enrichment factor close to 70. The 98Mo/95Mo measurements were characterized by RSDs from 0.5 to 1%. Instrumental mass discrimination of 1.4% was experimentally determined and used to correct the results. Concentrations found in plant reference materials were in agreement at the 95% significant level with certified values. A limit of detection of 0.8 ng g−1 was calculated based on the blank uncertainties and calibration curve on both isotopes.

Bioaccumulation of Elements in Bryophytes from Serra da Estrela, Portugal and Veluwezoom, the Netherlands (9 pp)

Pollution by heavy metals over large areas and long periods of time may cause chronic damage to living organisms and must be carefully controlled. One way to determine the extent of environmental contamination is by measuring the levels of contaminants in plants. The use of mosses as biomonitors is a convenient method to determine levels of (atmospheric) deposition, as terrestrial mosses obtain most of their supply of mineral elements from precipitation and dry deposition of airborne particles. Mosses have therefore received increasing attention as a suitable tool for monitoring regional patterns of elemental deposition from the atmosphere in large-scale studies in various countries, in areas close to industrial installations as well as in areas not expected to be contaminated. Although this technique is widely known, ecological studies of this type have rarely been done in Portugal. The aim of this paper is to evaluate and compare the spatial distribution of heavy metals in Hypnum cupressiforme, Pleurozium schreberi, Dicranum scoparium and Polytrichum piliferum collected from the Serra da Estrela natural park in Portugal and in the Veluwezoom natural park in the Netherlands. The selected species are the most widely used bryophytes for biomonitoring in the boreal region. The popularity of these species for this purpose is due to their wide ecological amplitude and distribution. At 54 sampling sites in both nature parks, samples of Hypnum cupressiforme, Pleurozium schreberi, Dicranum scoparium and Polytrichum piliferum were collected. Plant digests were analysed for Al, Ba, Ca, Cr, Fe, K, Mg, Mn, Ni, Sr, V, Zn, Pb, Cu, Cd, N and P. Differentiations between sampling sites in terms of concentrations of elements in mosses were evaluated by ANOVA and the least significant difference was calculated. The normality of the analysed features was checked with the chi square test. After standardization, the matrix of 54 samples and 10 heavy metals was subjected to numerical classification to detect groups of samples with similar patterns of metal concentrations. The clustering algorithm was prepared with Ward's method, and the City Block Manhattan method was used for the similarity measure. Metals and samples were also subjected to ordination to reveal possible gradients of heavy metal levels, using PCA. Correlations were calculated between concentrations of metals and factors 1 and 2, allowing the dependence between the concentration of metals and factors (factor loading) to be estimated. All species examined in both areas contained elevated levels of Mn and Pb. For each particular species, concentrations of N, P and Pb were significantly higher at Serra da Estrela, while concentrations of Cu were significantly higher at the Veluwezoom. Mosses from Portugal and the Netherlands differed significantly mainly in the concentrations of Al, Ba, Cr, Fe, Mn, Ni, Pb and V. This differentiation did not exceed that within the mosses from Portugal. Mosses from Portugal and the Netherlands differ significantly mainly in the concentrations of Al, Ba, Cr, Fe, Mn, Ni, Pb and V. This differentiation does not exceed the differentiation within the mosses from Portugal. Further research is required into the origin and deposition of the polluting elements in other environmental compartments.

Desenvolvimento de um micro-aquecedor para sistemas de análise química em fluxo: determinação espectrofotométrica de manganês em plantas

In this work a micro-heater device to be used as an integral part of the flow analysis manifold is described. The usefulness of the device was demonstrated using it in the development of a multicommutated flow analysis procedure for the spectrophotometric determination of manganese in plant digest. The method was based on the manganese oxidation by periodate in phosphoric acid medium to form the permanganate anion. The reaction development is dependent on the temperature and it was observed that at 25 °C a time interval of ca. 15 min was necessary for the reaction to attain equilibrium. Setting the temperature to 70 oC, this time interval could be decreased to ca. 30 s. This condition was easily attained employing the proposed micro-heater device coupled to the manifold. The procedure was applied to manganese determination in soybean digests and results compared with those obtained by inductively coupled argon plasma optical emission spectrometry (ICP-OES). No significant difference at 90% confidence level was observed. A linear response for sample concentrations ranging from 5.0 to 30.00 mg L-1 Mn2+; a relative standard deviation of 1.3% (n = 6) for a typical sample containing 6.3 mg L-1 Mn2+; a sampling rate of 22 determinations per hour; a low reagent consumption, of 12.0 mg NaIO4 per determination; and a detection limit of 1.2 mg L-1 were achieved.

Spectrophotometric flow-injection determination of zinc in plant digests based on a spot test

A spot test was implemented in a flow-injection system for the spectrophotometric determination of zinc in digests of plant materials. It is based on the influence of Zn2+ on the oxidation rate of 1-naphthylethylenediamine (NED) by hexacyanoferrate(III) under acidic conditions. In order to control the precipitate formation and to maintain the resulting suspension, a micellar medium was established by adding Triton X-100. The proposed system handles about 65 samples per hour, meaning 72μg NED and 9.0mg K3[Fe(CN)6] per determination. Baseline drift is usually <0.01 absorbance per hour and the analytical signals for 0.5–2.5mgl−1 Zn range within ca. 0.07–0.45 absorbance. Linearity of the analytical curve is fair (r>0.999, n=6) and detection limit was estimated as 0.2mgl−1 Zn. Results are precise (R.S.D.<1%, n=10) and in agreement with flame atomic absorption spectrometry and with certified values of standard reference materials.

SULFURIC ACID–SELENIUM DIGESTION FOR MULTI-ELEMENT ANALYSIS IN A SINGLE PLANT DIGEST

At the ICRISAT soil chemistry laboratory, a sulfuric acid–selenium (Se) digestion method has been used for several years for determination of nitrogen (N) and phosphorus (P) in a single plant digest. The method is simple and was evaluated for determining N, P, potassium (K), Calcium (Ca), and magnesium (Mg) in plant samples using a single digest. Finely ground plant materials of pigeonpea (Cajanus cajan L.) and rice (Oryza sativa L.) plant samples were digested at 370°C. Digestion completed in about 2.5 h when the digests were clear and colorless. Results with plant samples having a wide range in elemental concentrations, showed that there was an excellent agreement in the values of various elements determined by the proposed digestion procedure and the routinely used Kjeldahl and triacid acid digestion methods. These results suggest that sulfuric acid–Se mixture can be used for preparing plant digests for determination of N, P, K, Ca, and Mg in a single digest. In addition, this method is adapted for preparing plant digests for automated determination of N and P in plant samples using a Technicon Autoanalyser II.

Spectrophotometric flow-batch determination of aluminum in plant tissues exploiting a feedback mechanism

The feasibility of flow-batch systems to carry out procedures exploiting feedback mechanisms is discussed, and a flow-batch analyzer is proposed for spectrophotometric determination of aluminum in plant digests. As eriochrome cyanine R (ECR) was used as chromogenic reagent and considering the pronounced pH dependence of absorbance of the Al-ECR, in-line individual pH conditioning was performed. For pH matching, the m-cresol purple indicator was monitored in order to reach the required acidity for every assayed sample. The proposed system handles about 15 samples per hour, requires only 60 μg ECR per determination, and yields reproducible results (R.S.D.<1.0%). A quadratic correlation ( r>0.999, n=6) was achieved within 0.25 and 6.00 mg l −1 Al (dry basis). Results are in agreement with inductively coupled plasma atomic emission spectrometry.

Minimization of lead and copper interferences on spectrophotometric determination of cadmium using electrolytic deposition and ion-exchange in multi-commutation flow system

A new strategy for minimization of Cu 2+ and Pb 2+ interferences on the spectrophotometric determination of Cd 2+ by the Malachite green (MG)–iodide reaction using electrolytic deposition of interfering species and solid phase extraction of Cd 2+ in flow system is proposed. The electrolytic cell comprises two coiled Pt electrodes concentrically assembled. When the sample solution is electrolyzed in a mixed solution containing 5% (v/v) HNO 3, 0.1% (v/v) H 2SO 4 and 0.5 M NaCl, Cu 2+ is deposited as Cu on the cathode, Pb 2+ is deposited as PbO 2 on the anode while Cd 2+ is kept in solution. After electrolysis, the remaining solution passes through an AG1-X8 resin (chloride form) packed minicolumn in which Cd 2+ is extracted as CdCl 4 2−. Electrolyte compositions, flow rates, timing, applied current, and electrolysis time was investigated. With 60 s electrolysis time, 0.25 A applied current, Pb 2+ and Cu 2+ levels up to 50 and 250 mg l −1, respectively, can be tolerated without interference. For 90 s resin loading time, a linear relationship between absorbance and analyte concentration in the 5.00–50.0 μg Cd l −1 range ( r 2=0.9996) is obtained. A throughput of 20 samples per h is achieved, corresponding to about 0.7 mg MG and 500 mg KI and 5 ml sample consumed per determination. The detection limit is 0.23 μg Cd l −1. The accuracy was checked for cadmium determination in standard reference materials, vegetables and tap water. Results were in agreement with certified values of standard reference materials and with those obtained by graphite furnace atomic absorption spectrometry at 95% confidence level. The R.S.D. for plant digests and water containing 13.0 μg Cd l −1 was 3.85% ( n=12). The recoveries of analyte spikes added to the water and vegetable samples ranged from 94 to 104%.

Rapid sequential determination of arsenic and selenium in waters and plant digests by hydride generation inductively coupled plasma-mass spectrometry

A synchronised flow system with hydride generation coupled to ICP-MS is proposed for the sequential determination of As and Se in natural waters and plant digests. The alternated mixing of the sample solution with thiourea or HCl for the determination of As or Se under optimized conditions was achieved using a flow commutator before the reaction with NaBH 4. The on-line addition of thiourea promoted the quantitative reduction of As(V) to As(III), thus enhancing sensitivity and precision. The selenium pre-reduction from Se(VI) to Se(IV) was produced by heating the sample with HCl, and the hydride generation was performed in 4 mol l −1 HCl, thus avoiding interference from thiourea. The system allowed the analysis of 20 samples h −1 with LOD values of 0.02 μg l −1 As and 0.03 μg l −1 Se. Results were in agreement with the certified values at the 95% confidence level for reference waters from the Canadian National Water Research Institute and plant samples from the National Institute of Standards and Technology (NIST).