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1.
Abstract

The trace element pollution hazard of the continuous and large scale application of fertilizers and other amendments to soils depends in part on the chemical composition of these materials. Complete sample dissolution is generally required prior to total elemental analyses. The objectives of this study were to evaluate closed vessel microwave digestion procedures, using HNO3, HF, H2O2, and H3BO3, for the total dissolution of fertilizers and soil amendments and to develop a general digestion guide for individual samples. Twenty‐six materials, including commercial fertilizers, rock phosphate, liming materials, organic sources, and a soil sample were studied. More than 99.5% of each of these materials could be dissolved. Commercial nitrogen (N) fertilizers, most of the ammonium phosphates, and a potassium chloride sample could be completely dissolved using exclusively HNO3. The other samples required HNO3 and HF, used either in mixtures or consecutively in a stepwise procedure. The sewage sludge materials, the soil sample, and one of the rock phosphates were the only samples that could not be totally dissolved. No improvement in the digestions was observed by including H2O2. No significant contamination was evident during the digestions and satisfactory recoveries of 14 trace elements were obtained in digests of 2 standard reference materials. The proposed dissolution procedures are simple and safe. The usual quickness of microwave procedures was partially sacrificed to obtain a more complete dissolution of the samples. Digests obtained with these procedures could be potentially analyzed for other analytes, with the obvious exceptions of N, fluorine (F), and boron (B).  相似文献   

2.
Abstract

Application of a microwave dissolution technique to soil materials aided by acid digestion procedures has many advantages, but the incomplete dissolution of sandy soils has been noted. The objectives of this study were to modify a microwave oven digestion technique to facilitate the determination of the total elemental content of soils and geologic materials containing greater than 45% sand and apply these data to determine natural separations in parent materials. A microwave dissolution technique using aqua regia (HNO3 and HCl) and hydrofluoric acid (HF) was modified such that the HF is added to the solid 16 hours prior to aqua‐regia addition and subsequent microwave heating. Elemental recoveries were validated using a NBS coal fly ash standard. This procedure was applied to soil core samples representing a wide range of geological and pedological weathering sequences and soil textural classes. Separations in the parent material were determined by observing natural breaks in the elemental concentrations and comparing them to soil morphology data.  相似文献   

3.
Abstract

A method is described in which total soil boron (B) was determined by inductively coupled plasma atomic emission spectrometry (ICP‐AES). The method is based on microwave‐assisted digestion of soil samples with nitric acid (HNO3), hydrofluoric acid (HF) and hydrogen peroxide (H2O2). Excess HF was eliminated by adding silicon (IV) oxide (SiO2). The B 208.959 nm line was chosen as the analytical line to avoid the spectral interferences of iron (Fe). A detection limit of 0.0045 mg L‐1 was obtained with the selected analytical line under the optimized operating conditions. Four National Institute of Standards and Technology (NIST) standard reference materials (three soils and one river sediment) and four different type of practical soils were analyzed to test the reliability of the method. The total B concentration in selected samples ranged from 19 to 76 mg kg‐1. The excellent recoveries of the spike (98.5–101%) indicate that the proposed procedure is effective and feasible for the determination of total B in soils.  相似文献   

4.
Abstract

Two commonly used methods of dissolution of heavy metals in soils and sediments for atomic absorption spectrophotomety (AAS) determination were compared. Dry ashing and subsequent dissolution with 3 N HCl in a block digestor was shown to give a better estimate of the aqua regia‐soluble fraction than wet ash digestion with a mixture of HNO3 and HClO4 acids using reference materials. But both methods extracted significantly less than the certified total contents of most metals.

In soils and sediments from SW Spain, the amounts extracted by the block heater method were generally greater than those obtained by wet ash digestion. In agricultural soils, highly significant differences were found between the amounts of Fe, Cu, and Zn extracted by both methods, but the significance decreases if both methods are used on soils or sediments from mining areas where metal contents are likely to be from recent deposits.  相似文献   

5.
Abstract

Increased incidence of sulphur (S) deficiency in crops has led to a greater need for S determination in plant tissues. Among the methods available for measurement of S, inductively coupled plasma atomic emission spectrometry (ICP‐AES) has been proved to be accurate and rapid. This paper compares digestion with HNO3‐HClO4, fuming HNO3‐KNO3 and alkaline NaOBr prior to the S measurement by ICP‐AES. Both HNO3‐HClO4 and fuming HNO3‐KNO3 were found to give satisfactory results for five certified plant materials, with high accuracy and precision. The HNO3‐HClO4 method involved a rigid temperature control, with slow ramp rates and a final temperature (190°C) lower than the boiling point of HClO4, to minimise the possibility of gaseous losses of S. Both methods can also be used for the simultaneous determination of phosphorus (P), calcium (Ca), magnesium (Mg), iron (Fe), zinc (Zn), copper (Cu), and manganese (Mn), and additionally potassium (K) with HNO3‐HClO4. In contrast, the alkaline NaOBr method was less suitable as a digestion procedure for S measurement by ICP‐AES, because it involved a large dilution factor and produced high blank values.  相似文献   

6.
Abstract

Procedures for S determination involving digestion of plant material with HNO3/HClO4 mixtures gave lower values than those using oxygen flask combustion. Tests on a range of S compounds showed that the HNO3/HClO4 procedure underestimated S present in methionine, cysteine and glutathione but S in sulfate and the glucosinolate, sinigrin, was not underestimated.

Low recoveries using HNO3/HClO4 digestion procedures can be due both to incomplete oxidation of certain compounds and to gaseous losses during the vigorous boiling stage of digestion.  相似文献   

7.
An estimate of total potassium (K) contents of soils is required to assess the difficultly available fractions of soil potassium. Three digestion procedures were evaluated in terms of recovery of elemental K, precision, and simplicity in combination with analysis of K contents by inductively coupled plasma–optical emission spectroscopy (ICP-OES) in soils derived from contrasting parent materials. A hydrofluoric acid–perchloric acid (HClO4)–nitric acid (HNO3) mixture extracted the most K from 10 soils studied (4809.9 mg kg?1) followed by aqua regia (3180.89 mg kg?1) and HClO4–HNO3 mixtures (1206.75 mg kg?1). On average, aqua regia and HClO4–HNO3 digestion methods extracted 66.1% and 25.1% of the K extracted with the HF–HClO4–HNO3 mixture, respectively. Precision analysis as percentage of relative standard deviation showed excellent precision (<5%) for the HF–HClO4–HNO3 method (1.49%) compared to the HClO4–HNO3 mixture (10.72%). The present study concludes that the HF–HClO4–HNO3 digestion mixture is superior over both aqua regia and HClO4–HNO3 mixtures for total K estimation in the soils of Central Highland provinces of Papua New Guinea especially when ICP-OES is employed for analysis.  相似文献   

8.
A method for the simultaneous determination of aluminum (Al), arsenic (As), calcium (Ca), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), magnesium (Mg), manganese (Mn), phosphorus (P), lead (Pb), sulfur (S), selenium (Se), vanadium (V), and zinc (Zn) in organic soil amendments using microwave-assisted acid digestion and inductively coupled plasma optical emission spectroscopy (ICP OES) is proposed. Concentrated or diluted acids mixtures (HNO3, HF, HBF4, and H3BO3) combined or not with H2O2 were systematically evaluated in order to achieve the best digestion procedure for masses of around 150 mg of samples. Principal component analysis (PCA) was applied in order to choose the best acid mixture for digestion (3 mL HNO3 + 1 mL HBF4 + 2 mL H2O). The determined concentrations were in accordance with certified values of CRM 029 at the 95% confidence level, according to the Student-t test. This acid mixture was successfully applied for the digestion of four organic soil amendment samples (organic fertilizers, substrates, and soil conditioners) and element determination.  相似文献   

9.
Abstract

A two‐step digestion procedure using HNO3 and H2O2/UV irradiation is described. The samples are predigested with HNO3, succeeded by digestion in H2O2 under UV irradiation. The maximum temperature is 150°C. The digestion is performed without sample transfer during oxidation. The analytical data obtained by the new digestion method do not deviate from those obtained by HClO4 digestion. The macronutrient elements including P were measured.  相似文献   

10.
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.  相似文献   

11.
Abstract

The standard digestion method for total elemental analysis of soil material by the Soil Survey Laboratory (USDA Natural Resources Conservation Service) uses a 2‐mL clay suspension with hydrofluoric acid (HF) in a closed Teflon digestion vessel (method HF‐SUS). The accuracy and efficiency of elemental recovery by method HF‐SUS was compared to: (a) modification of HF‐SUS by use of a dried sample (method HF‐DRI); (b) modification of HF‐SUS by use of a dried sample and HF+aqua regia (method HF+AR); (c) sample digestion by Li metaborate fusion (method FUS); and (d) microwave digestion of samples with HF+aqua regia in Teflon bombs (method MICRO). Three replications of three standard reference materials (SRMs), fine‐earth (<2 mm) from 12 soils, and the clay (<2 urn) from 10 of those soils were analyzed. Method HF+AR shows the most consistent statistical agreement with the certified SRM values. Analysis of variance (ANOVA) indicates significant effects (α=0.05) for method of digestion, nonsignificant effects for method times SRM and method times clay, but significant effects for method times fine‐earth. Composition and/or variability of material are significant factors in the method of digestion. Method HF+AR yields significantly higher experimental means of A12O3, Fe2O3, and K2O contents and oxide recovery (summation of experimental means for oxides of all reported elements) than all other methods.  相似文献   

12.
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.  相似文献   

13.
An analytical procedure for the reliable determination of rare earth elements (REEs) in plant samples by inductively coupled plasma-mass spectrometry (ICP-MS) was developed. The influence of the main matrix elements was investigated first. It was established that moderate amounts (0.1–1.0%) of dissolved solids decreased the REEs signals significantly. Internal standardization with indium proved to be useful for obtaining correct results. Various digestion procedures were next applied to converting various solid plant samples to aqueous solution, namely dry-ashing, dry-ashing including a hydrofluoric acid (HF) step, and wet digestion using hydrogen peroxide (H2O2) and nitric acid (HNO3). Obtained results showed that the simple dry-ashing procedure was sufficient for plants. A certified reference material (BCR-670, aquatic plant) was used to validate the accuracy of the method. Relative standard deviations varied from 1% (holmium, gadolinium) to 4% (europium). Detection limits between 13 (lanthanum) and 0.02 ng L?1 (lutetium) were achieved.  相似文献   

14.
Abstract

High concentrations of lead in contaminated soils comprise a potential public health hazard. Limits between safe and dangerous levels are often based on total soil lead content. Current chemical procedures to determine total lead are unsuitable for routine soil analysis because they are time‐consuming and require highly trained personnel. This paper describes the effectiveness of three rapid extraction procedures to estimate total lead in a large number of lead arsenate‐contaminated orchard soils. Dissolution of soil lead in Kjeldahl flasks using a nitric acid‐perchloric acid mixture was virtually complete (98%) when compared to values for total lead measured by treatment with a mixture of HF, HNO3 and KClO4. Shaking of 5‐g samples in 50 ml of lN HCl or lN HNO3 for 1½ hours extracted 95 and 93 percent of the total lead, respectively. Regression equations were derived to allow estimation of total lead from values obtained in the HNO3‐HClO4, HCl, or HNO3 extracts. The HNO3‐HClO4 digestion procedure is preferred with atomic absorption spectrophotometry, while HCl extraction is suitable for routine soil analysis with inductively coupled argon plasma spectrophotometers or similar instrumentation.

Grinding of the soils to promote sample uniformity appeared unnecessary, at least in the silt loam soils tested.  相似文献   

15.
Abstract

Different plant analysis methods including varied incubation times with 0.5N and IN hydrochloric acid (HCl), diacid [nitric (HNO3) and perchloric (HClO4) acids], triacid [HNO3, sulfuric acid (H2SO4) and HClO4], H2SO4+hydrogen peroxide (H2O2) (Wolf method), and 0.5N and lN ammonium acetate (NH4OAc) were evaluated for measuring the potassium (K) concentration in straw and grain samples of cereal, legumes, oilseed crops, and fruit‐tree leaves. The average K concentration in nine plant materials indicated that K extracted by 0.5N and lN HCl for 5 minutes, 1 hour, and 17 hours contact periods did not differ significantly. But the amount of K extracted by these acidic solutions gradually decreased during incubation, possibly due to reabsorption of released K by the plant material. The amount of K released in to the 0.5N HCl and IN HCl extractants was in close agreement with that obtained with the standard triacid method. The IN NH4OAc extraction method slightly overestimated the K concentration in the materials compared to the other methods. Differences were observed among the methods in extracting K from different plant materials. In case of grain samples, the triacid method gave slightly higher values than that obtained by IN NH4OAc extraction. The results suggest that the 0.5N HCl and lN NH4OAc extraction methods can be used for the determination of K in plant tissues as these methods gave lower standard deviation and coefficient of variation values compared to the triacid method.  相似文献   

16.
Abstract

A method of digesting plant tissue samples for multi‐element analysis by inductively‐coupled plasma (ICP) emission spectroscopy was developed which does not require the use of HclO4. A substitute oxidant, H2O2, eliminated the hazards associated with hot, concentrated HClO4. Optimal conditions for pre‐digestion and digestion were investigated.

The procedure adopted consists of a pre‐digestion in concentrated HNO3 from room temperature to 60°C in 30 min followed by digestion at 90°C for 90 min with the addition of 30% H2O2 Analysis of NBS standard tissue samples by the proposed method gave results in good agreement with analysis following digestion in HNO3,‐HClO4 and with certified values, except for Fe.  相似文献   

17.
Determining the total elemental concentrations of soils requires a total dissolution method, in which hydrofluoric acid (HF) is commonly used. However, this method is tedious and risky due to the dangerous reagent HF. This study compared a single acid extraction technique using a nitric acid (HNO3) extraction method to total dissolution (HF + microwave assisted aqua regia) for evaluating the total elemental concentrations in soils and sediments. The two methods were used to analyze the elemental content of soils and sediments from the Oostanaula Creek and Pond Creek watersheds in East Tennessee. Twenty-one elements (Al, Ba, Ca, Co, Cr, Cu, Fe, K, La, Li, Mg, Mn, Nd, P, S, Si, Sr, Ti, V, Zn, and Zr) were subsequently measured using inductively coupled plasma optical emission spectrometry (ICP-OES). The extraction efficiency for HNO3 relative to the total was compared and discussed. In general, HNO3 can extract the elements in absorbed phases and those residing in non-silicate minerals. Six elements (Ba, Co, Fe, Ca, Mn, and P) generated significant correlations between total and HNO3 in both OC and PC watersheds. Finally, the elements were grouped according to the interrelationships of their total elemental concentrations based on the dendrogram plots, suggesting their geochemical association in soils and sediment forming minerals.  相似文献   

18.
The relationships between the concentrations of zinc (Zn), lead (Pb), copper (Cu), nickel (Ni) and chromium (Cr) as measured by X-ray fluorescence analysis (XRF), aqua regia, and HNO3 pressure digestion were studied in soil samples covering a wide range of heavy metal concentrations. The soils were contaminated by sewage sludge, exhaust depositions, river sediments of mining residues, and dump material. The question was addressed whether the source of heavy metals or other soil properties affect the relationship between these three methods. The aqua regia-digestible fraction of the five heavy metals reached on average 64% of the XRF-detectable content. The pressure accelerated HNO3-digestible fraction of the five heavy metals was on average 71% of the XRF-detectable content; the respective phosphorus (P) fraction reached a median of 75%. This suggests that HNO3 pressure digestion can also be used for characterizing the total P content of soils. Aqua regia extraction and HNO3 pressure digestion gave similar values for Zn, Pb, and Cu, which dominate the heavy metal load of most contamination sources. Significantly higher Cr values were obtained by HNO3 pressure digestion than by aqua regia extraction. Additionally, the Cr contents were affected by the source, e.g. sewage sludge had relatively high contents of aqua regia and HNO3 pressure extractable contents in comparison to the XRF values. The element-specific relationships between the three methods were all highly significant. However, the respective multiple linear regression models were in most cases affected by soil organic carbon (C), in some cases by clay or soil pH.  相似文献   

19.
Abstract

Different extraction reagents were studied in soils and the results obtained were compared with copper (Cu) contents of seven type fruits grown in these soils. For fruits, wet and dry ashing methods were applied and acceptable results were obtained by using dry ashing. The speciation is based on the dissolution of the soil samples in HNO3/H2O2, oxalic acid, acetic acid, EDTA and citric acid as extraction reagents at hot and cold conditions. Mean total Cu concentrations for all fruits studied were (mg kg‐1) in the range of 3.0–7.0 (dried weight basis). Significant positive correlations have been found between Cu contents of various fruits and different extractants studied. Flame atomic absorption spectrometry was used for determination of Cu in digestions. Probable chemical forms of Cu in soils were evaluated.  相似文献   

20.
Abstract

Microwave digestion of soils for elemental analysis commonly uses hydrofluoric acid (HF) because of insolubility of aluminosilicate minerals in other acids. Boric acid is added following digestion to complex F in solution. Low recoveries of calcium (Ca), aluminum (Al), and magnesium (Mg) of soil reference materials led to this investigation of a secondary heating of the boric acid with digested soil. The objectives were to evaluate boric acid (H3BO3) concentrations needed to complex F from 4 mL HF and to evaluate soil characteristics that may contribute to the formation of metal‐fluoride complexes that decrease recovery following digestion. Four standard soil reference materials and a variety of soil samples (n=75) were evaluated. Heating 20 mL 2.5% H3BO3 with a digested standard reference soil produced recoveries of 94, 98, and 99% for Al, Ca, and Mg, respectively, compared to 46% for Al and Mg and 37% recovery for Ca in extracts where H3BO3 was added but not heated. Two other concentrations of H3BO3 were tested with slightly improved recoveries, and results suggest that 20 mL of a 4.5% H3BO3 solution was sufficient to maximize recoveries. Digestion of soil samples by both the nonheated and heated H3BO3 methods showed that recovery difference between the two methods ranged from 0 to 100% for Al and Ca. Assuming that this difference in recovery was related to the formation of metal fluorides, correlation with clay and C in soils may reflect the positive or negative influence of these constituents on the formation of these complexes, respectively.  相似文献   

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