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1.
Abstract

A semi‐micro modification of perchloric acid digestion method for the determination of total P in soils, sediments, and organic materials is described. Samples are digested for 30 minutes with nitric acid at 115 °C and then for 2 hours with perchloric acid at 170 °C in an aluminum heating block. After dilution, samples are hydrolyzed at 100 °C for 1 hour in order to decompose pyrophosphate, and the liberated orthophosphate is determined without a neutralization step by the phosphomolybdate blue method of Murphy and Riley (1962). Comparability with the method of Sommers and Nelson (1972) is demonstrated using nine samples of different types. The same reaction conditions of digestion and color development as in the determination of total P in waters (Kopá?ek and Hejzlar, 1993) enable a comparable estimate of total P in solid and water samples in complex environmental studies.  相似文献   

2.
Abstract

Accurate and reproducible determinations of total sulphur can be made following digestion of plant samples with a nitric/ perchloric acid mixture containing dichromate and metavanadate. Care should be taken to control digestion temperatures. The occurrence of dense fumes of perchloric acid and the deposition of red chromium trioxide are not satisfactory indicators of the digestion endpoint. Digestion for lh. beyond the change in colour of the digest from green to olive‐brown was necessary, in our work, for consistent results.

Methods for reliable manual and automated determination of sulphate sulphur are described; the sulphur values obtained with our samples, were the same by both methods.  相似文献   

3.
Abstract

Inductively coupled plasma spectrometry (ICPS) was used for the simultaneous determination of P, K, S, Ca, Mg, Na, Al, Cu, Zn, Mn, Fe, Co, Mo and B in the nitric acid soluble portion of a variety of plant materials. Conditions for pre‐digestion, digestion and the requirement to grind cereal grain were investigated.

Digestion with nitric and perchloric acids caused loss of K (due to the low solubility of potassium perchlorate) and B (due to volatilization). The accuracy of Fe and Na determinations using nitric acid digestion was dependent upon the type of plant material.

The accuracy and precision of the proposed digestion and analytical procedure was confirmed by co‐operation in an interlaboratory quality assurance program using a variety of standard reference plant materials, and the analysis of National Bureau of Standards, Standard Reference Material 1571 (orchard leaves).  相似文献   

4.
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.  相似文献   

5.
Abstract

Total soil P was determined in six soils differing in pH, and in organic matter, total Fe, clay and sand contents. This study was undertaken to determine whether replacement of a sand bath.digestion procedure by an Al‐block digestion procedure affected the efficacy of an alkaline NaOBr method for determining total soil P. An Al digestion block was used for soil oxidation with NaOBr‐NaOH and the results were compared with a sand bath NaOBr method and a HC1O4 method. Temperature variability was very low in the digestion block (S.D.= ±1.4°C) when compared with the sand bath (S.D.= +20.1°C). The digestion block resulted in a greater precision in total P determination when compared to the sand bath (S.D.= ±3.7 vs. ±5.6, respectively). Linear relationships were obtained with the sand bath digestion technique (R2 = 0.981) and with the HC1O4 method (R2 = 0.982). Using an Al digestion block for NaOBr‐NaOH oxidation of soils for total P determination allows for a simple, precise alternative to sand bath digestion and to potentially hazardous HClO4 procedures.  相似文献   

6.
Abstract

The malachite green method was sometimes used to determine low concentrations of inorganic phosphate due to its high sensitivity. The aim of this work was to test the suitability of this method for the determination of phosphorus (P) extracted by various reagents, e.g., KCl 0.01–1.20M, CaCl2 0.01–0.1M, Na2SO4 0.01–0.40M, NaHCO3 0.1M at pH 8.5, and NaOH 0.1M+NaCl 1M. The malachite green method was also compared with the traditional molybdenum blue method on 35 soil extracts. Color development reached stability within 2 hrs and was stable for up to 24 hrs for dilute solutions. For concentrated solutions the stability was inversely proportional to the concentration of the reagent. Salt concentration appeared to have no effect on absorbance in KCl extracts of up to 1.2M and in Na2SO4 extracts of up to 0.05M. Higher concentrations of sodium sulfate induced flocculation and precipitation of the dye complex, as did CaCl2 above 0.04 M. A strong correlation was found between the malachite green and the molybdenum blue method. The malachite green method can be used for P determination in soil extracts when appropriate time of color development is provided and salt concentration is taken into account.  相似文献   

7.
Abstract

Samples of vegetation and faeces from heavily grazed pastures are likely to be contaminated with soil to some extent. The determination of total potassium on these samples will result in low recoveries if a wet oxidation procedure normally used for vegetation analysis is employed. However, data are presented which show that for the sites studied satisfactory recoveries of total potassium are obtained following a sulphuric acid‐hydrogen peroxide digestion, providing the ash content of the sample does not exceed 25%. For ash contents greater than 25%, alkaline fusion or hydrofluoric/perchloric acid decomposition procedures are required to obtain full recovery.  相似文献   

8.
Abstract

Procedures for determination of fluoride (F) in plant material employing acid digestion and solution analysis by ion specific electrode (ISE) were compared to alkali fusion using a range of plant materials. The efficiency of the methods were assessed using standard reference plant material (SRM) not previously available for plant F analysis. All acid digestion procedures tested failed to obtain the certified value for F in the SRM. This was due to failure of the acids to liberate F bound strongly within silicate minerals found in the plant materials. Acid digestion is therefore not recommended for determination of total F, but could be used to determine labile F in plant materials. During investigation of the acid digestion procedures, it was also found that F concentrations determined in solution using the ISE are sensitive to solution pH, even at solution pH values where complexation of F with hydrogen ions (H+) can be discounted. It is therefore recommended that both ionic strength and pH of sample and standard solutions be matched when determining F concentrations in solution using the F‐ISE.  相似文献   

9.
Abstract

Malachite green method has been evaluated for estimating minute quantities of phosphorus (P) in water, 0.01M calcium chloride (CaCl2), and Olsen [sodium bicarbonate (NaHCO3)] extracts often soils of varying properties. The precision and accuracy of the malachite green method was better than that of the ascorbic acid method to estimate P in these three extracts. The recovery of added P ranged from 95.3–99.3% in water, 96–100% in 0.01M CaCl2, and 96.7–100% in Olsen extracts. The ascorbic acid method underestimated the amounts of 0.01M CaCl2‐P and its precision was also lower than the malachite green method. It is possible to predict the P concentration in the three extracts equal to malachite green method from the ascorbic acid P values by using regression equations.  相似文献   

10.
Abstract

A wet digestion method for plant tissue analysis for use with Inductively Coupled Plasma ‐ Atomic Emission Spectrometry has been developed. This procedure uses only nitric acid and eliminates the use of perchloric acid and subsequently eliminates the danger of HClO4. explosions, and the problem of KClO4 precipitation. Analysis of National Bureau of Standards plant materials ‐ orchard, tomato, and spinach leaves ‐ digested with nitric‐perchloric acid or nitric acid compared very well with the NBS certified values. The analytical results for eight other plant species were comparable for the two methods of digestion.

A summary of the recommended procedure for use with ICP is given below: 1. Weigh 0.5 to 1.0 g of plant tissue into a 50 ml Taylor tube.

2. Add 10 ml conc, nitric acid. Let stand overnight.

3. Heat samples at 125° C for 4 hours. Let cool.

4. Dilute to 12.5 ml with conc, nitric acid. Dilute to 50 ml with distilled water. Mix and let amorphous silica settle.

5. Aspirate directly into plasma for ICP analysis of P, K, Cu, Mg, Na, Fe, Zn, Ca, Mn.

  相似文献   

11.
Abstract

A two‐step digestion with hydrogen peroxide (H2O2)/boiling sulfuric acid (H2SO4) ("peroxy treatment") in the absence of heavy metals catalysts is proposed as an alternative to the copper (Cu)/selenium (Se) catalyzed digestion process for the routine determination of soil Kjeldahl‐nitrogen (N). Sixty‐eight samples from pedotypes representative of the Mediterranean environment, with contrasting features and use, were chosen in order to ensure the largest variability of total N and organic carbon (C) contents. The average soil N content was 0.223 g/100g for the H2O2 treatment, and 0.196 g/100g for the Cu/Se one, with significant difference between the means and with limits ranging from 0.042 to 0.678 and from 0.025 to 0.696 g/100g for H2O2‐N and Cu/Se‐N, respectively. The amounts of soil N determined by the contrasted procedures were strictly dependent on the respective organic C contents, and they correlated each other by the highly significant linear regression: Cu/Se‐N = ‐0.017 + 0.955/H2O2‐N, R2 = 0.910***. The goodness of fit of this equation was not significantly improved when the organic C and the Al‐Oxa contents were introduced as accessory explanatory variables in multiple regression models. This should allow an easy and quick data conversion with no need of additional laboratory analyses. Altogether, the achieved results clearly show that the tested methods work with homogeneous performance under a range of soil properties, providing evidence that the current digestion procedure by heavy metals catalysts could be conveniently replaced by the less hazardous “peroxy”; treatment. This really represents an attractive innovative procedure for routine determination of soil Kjeldahl‐N with reference to the environment safety concerns.  相似文献   

12.

A method is described for the determination of total lead in soil by atomic absorption spectrophotometry. The sample is digested with hot nitric acid. The dry residue is taken up in hydrochloric acid and excess iron is removed by extraction with acetylacetone‐chloroform. Lead is then extracted using the system DDC‐MIBK. The organic phase can be sprayed directly into the flame.

The method is not affected by elements occurring in contaminated soils. Iron is removed because a slow‐forming precipitate of the Fe‐DDC‐complex blocks the nebuliser system. The method is an improvement on other methods because no sulfuric acid is used for digestion, and therefore losses of lead by precipitation or occlusion are avoided. Tests confirm that the recommended method gives complete recovery of lead.

Lead can be determined in the range from 4 to 240 ppm in the soil. A standard soil sample has been analyzed, yielding a mean value of 125 μg Pb/g soil with a relative standard deviation of 2.4%.  相似文献   

13.
Abstract

Six different methods for measuring total sulphur concentrations in plant material were applied to orchardgrass samples derived from three cuts of a field trial with combinations of sulphur and nitrogen fertilizer applications. The results from the methods were grouped into three pairs of high, intermediate and low measured total sulphur concentrations. Highest concentrations were obtained using an oxygen flask and the LECO CNS‐2000 automated dry combustion methods, intermediate concentrations with an alkaline digestion and the Fisher automated dry combustion instrument, and lowest with two perchloric acid digestion methods. The low results with the two perchloric acid methods likely occurred from sulphur volatilization and incomplete organic sulphur compound destruction. The results from the pairs of methods with similar total concentrations did not yield the same significant cut, sulphur and nitrogen main and interaction effects when analysis of variance was applied to the treatment results. The two dry combustion methods agreed reasonably closely regarding the main and interaction effects, but calculated recovery of applied sulphur varied. It is apparent that current methods do not agree precisely in their ability to measure total sulphur in plant material types, and for the same type of plant grown under different climate conditions and fertilizer treatments. It was concluded that values by LECO CNS‐2000 instrument provided the best measurement of total sulphur for fertilizer response trials.  相似文献   

14.
The ignition method and the perchloric acid (HClO4) digestion method for the determination of total phosphorus (P) content in 65 agricultural soils of Taiwan were compared. The average amount of total P obtained by the ignition method was 4.3% less than that obtained by the HClO4 method. There was a wide range of variation, from 37% less to 21% more in the ignition method than those results obtained by the HClO4 digestion method. Because the ignition method can also be used for the estimation of soil organic P and is thus worthy of further study, it should be adopted as a routine procedure.  相似文献   

15.
Abstract

Rapid and accurate determination of low‐level (0.01 to 1.0 mg L?1) phosphorus (P) concentrations in farm canal water is important in evaluating water quality in the Everglades Agricultural Area (EAA) canals in south Florida. Two U.S. Environmental Protection Agency methods, persulfate digestion (365.1) and Kjeldahl digestion with mercury oxide (365.4), were used to analyze total P (TP) and total dissolved P (TDP) in two sets of representative canal water samples collected at low‐flow conditions in 2003 and high‐flow conditions in 2004. Quality assurance samples (blanks, duplicates, and spikes) were included to evaluate differences between the two digestion methods. Precision analysis had a mean of less than 5% for both TP and TDP using both methods. The high coefficient of correlations (r>0.98) indicated that the two methods were significantly correlated in determining TP and TDP of the samples. Low detection limits (0.004 mg L?1) were achieved by the persulfate method. This method offers many other advantages over the mercury digestion: it produces no toxic mercury waste, uses less time, and uses a lower temperature. High suspended solids in canal water samples were not proven to be a problem when using the persulfate digestion, though lower spike recoveries were observed than those when using the mercury digestion. We conclude that persulfate digestion is a more sensitive and environmentally responsible alternative to and is, as precise as, the mercury method for routine determination of TP and TDP in water samples. This information is useful to environmental laboratories in monitoring P concentrations in surface and groundwater.  相似文献   

16.
Abstract

Wet acid digestion on a heat block or in a closed‐vessel microwave digestion system normally use half a gram to 1 gram of organic samples, but it is difficult to take a small quantity of representative sample from animal waste materials due to their heterogeneity. This study investigated an alternative microwave digestion system to prepare animal manure samples for plant nutrient analysis. Two types of solid animal manure and two reference plant samples were digested with an open‐vessel microwave digestion system and with the conventional nitric/perchloric acid block digestion, and analyzed for macro‐and micronutrients. Results of the open‐vessel microwave digested samples were comparable to those digested by conventional block digester and in high agreement with the certified values of reference materials. The open‐vessel microwave can reduce digestion time from about 4 hours to about 30 minutes. Fresh samples up to 10 grams can be completely digested directly by the open‐vessel microwave without sample drying and grinding. Sample representation of bulk manure should be better when sample size increased from 1 to 10 grams. Eliminating drying and grinding before digestion improves lab efficiency.  相似文献   

17.
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   

18.
An earlier acid digestion determination of iodine in foods was modified to provide an improved detection limit and to allow for the analysis of a greater variety and larger amounts of foods. The organic material in the sample was oxidized overnight by concentrated nitric acid, followed by digestion in a mixture of concentrated sulfuric and 70% perchloric acid. The iodine was determined by an automated colorimetric method based on the iodide-catalyzed reduction of Ce+4 by As+3. The method had an average relative standard deviation of 3.1% for the samples analyzed, and a detection limit of 0.1 ng/mL in the digested solution and 5 ng/g in a 2 g sample prior to digestion. The recovery of added iodine ranged from 90.3 to 101.3%, using external standards. Samples analyzed included NBS Standard Reference Material 1549, and composites of a variety of dairy products, meat, eggs and fish, cereals, and potatoes. The iodine detected in these samples ranged from 9 ng/g for the potato group to 3360 ng/g for the standard reference material.  相似文献   

19.
The objective of this study was to obtain an indicator of labile nitrogen (N) through a cost- and time-saving procedure by evaluating the relationships among potentially mineralizable N (N0), particulate organic matter N (POM-N) and soil organic N extracted through partial soil digestion with different concentrations of sulfuric acid (H2SO4). Soil sampling (0–20 cm) was from nine fields under no-tillage. The N0 and POM-N were determined by long-term aerobic incubation and soil physical fractionation, respectively. A simple chemical method was developed by soil digestion at 100°C for 4 h with different concentrations of H2SO4 (0.1, 0.5, 1, 6, 12, and 24 mol L?1). All acid concentrations showed significant relationships with N0 as POM-N; however, the best prediction was resulted for 0.5 mol L?1 (R2 = 0.90–0.94, respectively), thus using this methodology as soil labile N indicator. This method would optimize N0 and POM-N estimation in short term and at a low cost.  相似文献   

20.
Thermal utilization of sewage sludge through mono‐incineration or gasification results in phosphorus (P) rich sewage sludge ash (SSA) that must be returned to agricultural production systems to fulfill the need for recycling of P resources contained in wastewater streams. As the plant‐availability of P contained in SSA is low, we propose feeding SSA directly into the production of superphosphate fertilizers, thereby opening a further pathway for the recycling of phosphorus (P) from wastewater streams to agricultural production systems by using available technologies. We carried out laboratory‐scale production of superphosphate test‐products, in which rock phosphate (RP) was partially replaced with SSA (gasification) before digestion with concentrated sulfuric acid, and evaluated these products with regard to the solubility of P in H2O and neutral ammoniumcitrate solution. We further carried out a growth‐chamber experiment (28 d) using maize (Zea mays L. cv. Sulano) as a model plant on a low P (0.4 mg PCAL 100g?1), high pH (7.6) substrate to evaluate plant P availability of the test products. Our laboratory‐scale results show that at least 8% of P from RP can be replaced by P from SSA while maintaining both the high solubility of P in the fertilizer product and the growth of maize compared to pure RP digested with concentrated sulfuric acid. Further substitution of RP through SSA decreased the total P concentration of the test products, as well as the relative amounts of P soluble in H2O and neutral ammoniumcitrate solution, which affected early plant development of maize.  相似文献   

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