Microwave Digestion for Colorimetric Determination of Total Si in Plant and Mineral Samples

A new method for determining the soluble silicon (Si) concentrations in nonliquid plant and mineral samples was developed using sodium hydroxide (NaOH)–hydrogen peroxide (H₂O₂) matrix for microwave digestion (MWD-Na) followed by colorimetric Si testing. MWD-Na was compared with autoclave-induced digestion and alkali fusion. The data have shown no significant difference between these three methods. HNO₃–H₂O₂ or HNO₃?–H₂O₂?–HF microwave technique results in Si loss. The reduction of the total Si can be realized via low solubility of Si in the acid solutions or silicon tetrafluoride formation. The Mullen and Riley method for colorimetric testing of Si in a solution that uses ascorbic acid to reduce the silicomolybdate complex formed under acid conditions to an intensely blue complex was modified using iron sulfate. The combination of MWD-Na and modified colorimetric blue method provides cheap and valid data on determining the total Si in both plant and mineral samples.     

Comparison of a microwave digestion system to other digestion methods for plant tissue analysis

Abstract

Most digestion procedures for the preparation for plant tissue for elemental analysis are often very laborious. Elemental contents of plant tissue prepared by microwave digestion were compared to those obtained by conventional dry ashing and sulfuric acid‐hydrogen peroxide wet digestion. All three digestion methods produced comparable quantitative values for the elements P, K, Ca, Mg, Fe, Mn, Zn, and Cu for all plant materials used. Thus, the microwave digestion technique was shown to be a viable rapid method for digesting relatively small numbers of samples prior to elemental analysis.     

Determination of aluminum in plant tissue digests using a catechol violet colorimetric method

Abstract

A procedure is described for the colorimetric determination of Al in acid digests of plant tissue using catechol violet as the chromogenic reagent. Components of plant tissue digests were examined for interference in the determination of Al using the described procedure. For highest accuracy, Al standards should contain macroelements, microelements, and acid at concentrations generally typical of those present in acid digests of the plant tissue being analyzed. Using the described procedure, recovery of Al added prior to digestion was 99.1% and 97.1% for National Bureau of Standards SRM 1571 (orchard leaves) and SRM 1572 (citrus leaves), respectively.     

Plant Alkaline Fusion Technique Followed by Colorimetric Procedure for the Detection and Quantification of Total Silicon in Ornamental Plants

Silicon (Si)–determination procedures currently available require expensive equipment and must be modified to assess Si concentrations in plant tissues. A Si-determination procedure referred to as the plant alkaline fusion technique, or PAFT, was developed to assess total Si concentrations, specifically in plant tissue. The procedure consists of dry-ashing the plant material, alkaline fusion, solubilization of the fusion cake, dilution, and colorimetric determination to quantify total Si content. The fusion technique for solubilizing plant Si can be performed using sodium hydroxide (NaOH), nickel crucibles, and Bunsen burners. Silicon concentrations of two National Institute of Standards and Technology (NIST) standard reference materials (SRM) [pine needles (SRM 1575) and peach leaves (SRM 1547)], a rice straw standard (LSU#5), an NIST soil standard (SRM 2709), and five ornamental plant species were all assessed using the PAFT procedure, and then these values were compared to two different inductively coupled plasma–optical emission spectroscopy (ICP-OES) procedures conducted by independent laboratories. The PAFT Si determination procedure typically reported the greatest value or was within 15% of the two ICP-OES procedures while costing significantly less than both ICP-OES procedures.     

Dry ashing of plant material and dissolution of the ash in HF for the colorimetric determination of silicon

Abstract

In the past, determination of silicates in plant material was laborious and/or difficult. In several research fields outside plant analysis, digestion of material was obtained with the use of HF, followed by a boric‐acid treatment to eliminate excess HF.

In the present study, this procedure was applied to plant material. Before digestion with HF, the plant sample is dry‐ashed. After suitable dilution, Si can be determined colorimetrically. The proposed method proved to be rapid and accurate.     

Statistical Comparison of Wet and Dry-Ashing Digestion Methods for the Determination of Copper and Iron Species in Orange Peel,Flesh and Tree Leaves by Flame Atomic Absorption Spectroscopy

In this study, two methods of wet digestion and dry-ashing digestion are performed and compared statistically for the determination of iron (Fe) and copper (Cu) species in the orange peel, flesh and leaves by means of flame atomic absorption spectroscopy (AAS). In wet digestion, the effects of two reagents and their mixtures were studied. In dry digestion, various factors affecting the digestion were studied and optimal condition established. Based on the average concentration (mg L^?1), standard deviation (n = 5) and relative standard deviation (RSD)%, the best conditions of dry digestion and wet digestion to extract Fe and Cu were chosen. Finally, some 12 measurements were performed based on the optimum conditions of dry and wet digestions and the best method was selected with regard to the obtained results. In orange tree leaves because t_exp (0.016) is smaller than t_theorical (2.18), it shows that there is no difference between the two methods for analysis of Fe. However, the determination of Cu in orange tree leaves was practical with wet digestion in that t_{exp (57.14)}? t_{theorical (2.18)} shows there is a difference between the two methods and wet digestion is more suitable than dry-ashing due to obtaining less RSD%. In flesh orange, it is seen that for both t_exp ? t_theorical, showing there is a difference between the two methods and wet digestion is more suitable than dry-ashing one. Furthermore, in both Fe and Cu species, the t_exp ? t_theorical, indicating that the two digestion methods are different and wet digestion was selected as a suitable method because of obtaining smaller values of RSD%. Finally, after comparison of the results, the wet digestion vessel for Fe and Cu extraction in the samples was suggested. The developed digestion methods were validated with certified reference materials.     

Rapid,Wet Oxidation Procedure for the Estimation of Silicon in Plant Tissue

Abstract

The quantification of silicon (Si) in plant samples is being requested more frequently, especially in agricultural laboratories associated with the determination of nutritional requirements of sugarcane (Saccharum officinarum L.) and rice (Oryza sativa L.). The analysis of plant material for Si can be protracted, especially if laboratories do not have access to X‐ray flourescence (XRF) instrumentation and large numbers of samples are involved. A simplified procedure using equipment considered standard in most agricultural laboratories is reported. Dry, ground plant material is subjected to nitric acid/peroxide oxidation in a low‐pressure laboratory microwave digestion system. The hydrated silica liberated from the organic matrix is dissolved in a small volume of sodium hydroxide solution also using the microwave digestion system. Silicon is measured by inductively coupled plasma atomic emission spectrometry (ICP‐AES). This method gives results that are linearly correlated with the much slower conventional techniques and avoids using hazardous chemicals (hydrofluoric acid) sometimes employed in other microwave methods.     

Sodium hypobromite digestion for boron analysis of plant and soil materials

Abstract

A sodium hypobromite digestion procedure was developed for total boron content of plant tissue. The method completely released total plant boron and took much less time than a dry ash method. The sodium hypobromite digestion was compatible with a modified curcumin colorimetric method. The sodium hypobromite digestion eliminated interference by nitrate, fluoride and iron, which were previously shown to be potential problems with the colorimetric method. Aluminium eliminated the interference of fluoride on boron analyses by the modified curcumin method without the sodium hypobrornite digestion step.

The sodium hypobromite digestion procedure was applied to a number of different soils after the volume of sodium hypobromite to soil sample weight ratio was optimized to release a constant amount of boron. The boron measured did not appear to be total boron in every soil. However, two other methods (sodium carbonate fusion and hydrofluoric acid treatment) recommended for total boron were not entirely successful either for the same soils. Correlations of soil boron values with selected soil chemical and physical measurements suggested that the hydrofluoric acid method was more successful in measuring boron associated with soil organic matter while the sodium hypobromite and sodium carbonate methods were more successful in measuring boron associated with the mineral portion, especially the silt fraction. The sodium hypobromite digestion appeared to be less efficient than sodium carbonate fusion in determining “total”; boron with increasing pH of the soil. The sodium hypobromite digestion boron values of soils may be useful as a boron fraction measurement but should not be considered as total boron.     

Environmental and biological samples analyzed by inductively coupled plasma emission spectrometry

A number of closely related acid digestion procedures are proposed for the accurate analysis of animal tissue, plant tissue, sediment and particulate samples. A closed teflon vessel is employed to reduce contamination and to speed up digestion. Procedures which minimize evaporations should be employed where applicable. Hydrofluoric acid is essential when plant tissue, sediment and particulate material are to be dissolved. Accuracy and precision is assessed using standard reference samples.     

Rapid gravimetric determination of Si in rice straw

Abstract

The Si content of rice straw is used as a measure of the Si status of rice plants, the growth and grain production of which are reduced when plant Si is low. Straw Si often is determined gravimetrically following digestion of plant tissue. A new, rapid gravimetric procedure has been developed for determining Si in rice straw. The straw is oxidized, washed free of various components, and SiO₂is developed and weighed in fritted glass Gooche crucibles. The rapid method reduces the analysis time, reduces glassware requirements, and eliminates analyte transfers.     

Comparison of four methods of digestion for the determination of total phosphorus content in hen droppings

Abstract

The objective of this study was to compare four methods of digesting for the determination of total phosphorus (P) content in hen droppings by colorimetric spectrometry. For this comparison, we used an homogeneous and oven‐dried sample of hen droppings and made 19 analyses with each method on this same sample. Method 1 was a dry and complete digestion with addition of calcium carbonate before ashing at 550°C for 12 h. Method 2 was a dry simplified digestion without the addition of calcium carbonate. Method 3 was a wet and complete digestion with sulfuric acid and successive addition of nitric acid and heating. Method 4 was a wet simplified digestion with sulfuric and nitric acids added at once and heating for 30 min. We obtained P levels of 1.93±0.049%, 1.93±0.047%, 1.96±0.079%, and 1.98±0.143% for the four methods, respectively. There was no statistical difference among those four methods, and therefore we recommend Method 2 since it requires the use of less concentrated acids, and in addition, the standard deviation is the lowest.     

不同前处理方法对秸秆金属元素原子吸收光谱分析结果的影响

秸秆中金属元素是关系农作物秸秆科学利用的重要组成部分,目前还没有统一的秸秆中金属元素原子吸收光谱(atomic absorption spectroscopy,AAS)测定方法标准,该研究采用原子吸收光谱测定黄芪(GBW10028)标准物质、玉米秸秆、小麦秸秆和棉花秸秆中金属元素含量,比较了不同前处理方法对样品中K、Cu、Fe、Zn和Mg分析结果的影响。结果表明:微波消解、干法灰化和湿法消解测定黄芪(GBW10028)标准物质中金属元素含量差异性显著(P<0.05),微波消解比干法灰化、湿法消解准确度高。微波消解对玉米秸秆、小麦秸秆和棉花秸秆中各金属元素的影响与黄芪(GBW10028)标准物质趋于一致。微波HNO3与微波HNO3-H2O2测定结果差异性不显著(P>0.05),微波HNO3比微波HNO3-H2O2和微波HNO3-H2SO4测定结果稳定。微波HNO3是进行秸秆样品金属元素含量测定时较准确简便的前处理方法。     

植物硫素营养诊断技术的研究进展

作物缺S的状况在世界范围内呈现扩大的态势.作物和土壤的S素分析有助于作物获得高产.本文综述了植物可见症状、植物组织分析和土壤分析诊断技术的研究进展.植物组织分析诊断技术包括全S、硫酸盐-S、N/S比、苹果酸盐/硫酸盐比、种子含S量及小麦籽粒戊二醛浸泡比色法.分析种子的S含量是诊断大豆S素状况一个简单而又可靠的方法.这种方法是诊断植物S素营养状况的新方向,因为它可以在作物播种前确定作物的S素状况.土壤分析作为诊断土壤S状况时,还应考虑深层土壤的S含量、硫酸盐淋溶指数、环境条件及田间管理历史.     

A manual colorimetric procedure for measuring ammonium nitrogen in soil and plant Kjeldahl digests

Abstract

The measurement of NH4⁺‐N in soil, and plant digests is one of the greatest needs in laboratories conducting agricultural and environmental research. Many laboratories do not have access to automated equipment for colorimetric analysis of soil and plant digests. The objective of this research was to modify an automated colorimetric analysis procedure for determining NH₄+‐N in soil and plant digests for manual use, and compare the proposed technique with the standard distillation‐titration technique. The modified procedure is based on the color reaction between NH₄ ⁺‐ and a weakly alkaline mixture of Na salicylate and a chlorine source in the presence of Na nitroprusside. Wavelength scans indicated a very well defined peak for determinations at 650 nm. Time scans showed that color development in the manual procedure was rapid, 12 to 40 minutes depending on temperature, and that the color development remained stable for at least 120 minutes. Regression analysis of the results from 18 soil and 20 plant tissue sample determinations by distillation‐titration and the proposed method indicated NH₄ ⁺ ‐N recoveries of 99% or higher. The results obtained using the colorimetric procedure were very similar to the values obtained by distil ling and titrating the digests for both soil and plant samples as indicated by the large coefficients of determination (R² = 0.99).     

A field method for the determination of total nitrogen in plant tissue

Abstract

While studying sward quality in Kenya, East Africa, we established a field laboratory for the determination of total nitrogen. Using Kjeldahl digestion procedures and an indophenol colorimetric method, we successfully analyzed over 900 plant and fecal samples while living in a tent camp. Variation from one digestion to the next was corrected for by using a grass standard with each digestion. Independent tests by other laboratories verified the accuracy of our methods.     

Leaf‐tissue silicon content of sugarcane genotypes grown on everglades histosols 1

On soils low in plant‐available silicon (Si), fertilization of sugarcane (Saccharum spp.) with calcium silicate slag increases plant Si content and sugar yield. However, Si fertilization is costly. Plants which are more efficient in accumulating available Si may have an economic advantage, and selection for genotypes with greater Si content may be warranted. The purpose of this study was to determine if there was genetic variability for plant‐tissue Si content in selected populations of commercial‐type sugarcane clones in the Canal Point (CP), Florida breeding program. A total of 52 sugarcane genotypes from the third and fourth stages of the sugarcane breeding program were evaluated for Si content in leaves. Clones were evaluated as plant cane in randomized complete‐block experiments at four sites which varied in plant‐available Si. Soils at three sites were organic Histosols; the fourth was a sand. The locations and the forty Stage HI clones varied significantly (P<0.01) in plant‐tissue Si. Stage P7 test sites also varied significantly, but the 12 clones, which were of a narrower genetic base, did not. In both tests, ‘CP 72–1210’, a very popular and high‐yielding commercial cultivar, had the greatest mean Si content. Results indicated that genotypic variability for Si content exists in elite, commercial‐type sugarcanes. A greater range of Si content might be found in a more diverse array of genotypes. A study to investigate the heritability and stability of plant tissue Si content should be feasible.     

Determination of molybdenum in plant tissue by graphite furnace atomic absorption spectrophotometry (GFAAS)

Abstract

The analysis of molybdenum in plant tissue using graphite furnace atomic absorption spectrophotometry (GFAAS) is described. The method involved wet digestion using a mixture of sulphuric, nitric and perchloric acids followed by a solvent extraction procedure. Molybdenum was extracted into di‐iso butyl ketone (DIBK) as the iron‐thiocyanate complex. The extract was then analysed for molybdenum by GFAAS.

The results of analyses of the reference plant materials (orchard leaves and citrus leaves) of the National Bureau of Standards (NBS) compared very well with the certified values. Other types of plant tissue were also analysed and the results correlated well with those obtained by an alternative method.     

Mixed-Effects Estimation in Dynamic Models of Plant Growth for the Assessment of Inter-individual Variability

Modeling inter-individual variability in plant populations is a key issue to understand crop heterogeneity and its variations in response to the environment. Being able to describe the interactions among plants and explain the variability observed in the population could provide useful information on how to control it and improve global plant growth. We propose here a method to model plant variability within a field, by extending the so-called GreenLab functional-structural plant model from the individual to the population scale via nonlinear mixed-effects modeling. Parameter estimation of the population model is achieved using the stochastic approximation expectation maximization algorithm, implemented in the platform for plant growth modeling and analysis PyGMAlion. The method is first applied on a set of simulated data and then on a real dataset from a population of 34 winter oilseed rape plants at the rosette stage. Results show that our method allows for a good characterization of the variability in the population with only a limited number of parameters, which is a key point for plant models. Results on simulated data show that parameters associated with a low sensitivity index are inaccurately estimated by the algorithm when considered as random effects, but a good stability of the results can be obtained by considering them as fixed effects. These results open new ways for the analysis of inter-plant variability within a population and the study of plant–plant competition.Supplementary materials accompanying this paper appear online.     

Simple and Inexpensive Water Extraction Method for Assaying Potassium Concentration in Tobacco Plant Tissue

Potassium (K) in plant tissue is not bound to organic compounds and occurs in soluble forms, thus indicating the ease of its extractability. The conventional methods of plant-sample preparation for K determination are often tedious, time-consuming, and/or require chemicals, making the analysis expensive. In this investigation, we propose a water extraction method for assaying K concentration in tobacco leaf tissue and evaluate it for analytical accuracy and precision in comparison to the established methods, namely, triacid digestion, 1 N ammonium acetate (NH₄OAc) extraction, and 0.5 N hydrochloric acid (HCl) extraction. The proposed method entails extracting K from 0.5 g finely ground plant tissue (<0.5-mm sieve) with distilled water at a 1:100 ratio (sample weight to water volume, w/v) by shaking for 20 mins and filtering before K measurement by flame photometry. Results with 25 tobacco leaf samples having a wide range in K concentrations showed very close agreement between the values of K determined by the proposed water extraction method and the established methods. The mean K concentration obtained with water extraction method was within 3 to 6% of those measured by established methods. The correlations between the K values obtained by the established methods and the water extraction method were highly significant (P?=?0.01), and the relationships are best described by linear regression equations with high values of R² (>0.99). The standard errors (SEs) and coefficient of variation (CV) for K measurements by different methods followed the order water extraction < HCl extraction < triacid digestion < NH₄OAc extraction. The results suggest that the water extraction method is comparable in accuracy and superior in precision to the established methods for K determination. Being simple, rapid, and inexpensive, the water extraction method could be used as an alternative to the most commonly employed standard, triacid digestion, for routine analysis of K in tobacco plant tissue.     

Determination of boron in fresh and in dried plant material by plasma emission spectrometry after extraction with HF‐HCL

Abstract

The boron content of plant material was determined by ICP‐AES after a simple extraction with a mixture of HF and HC1. The method gave excellent agreement with the colorimetric determination by Azomethine H after dry‐ashing and with ICP‐AES after dry‐ashing. No significant interferences were found from 17 elements with ICP‐AES. A digestion procedure with only HNO₃, followed by ICP‐AES determination, gave low results at higher B levels. The HF‐HC1 extraction was applied to both fresh and dried material; the boron values thus obtained compared very well, which indicates that no loss of boron compounds occurs during drying.