Wet Ashing Techniques Research Articles

Effects of rice-straw derived phytoliths on the surface charge properties of paddy soils

Straw of rice (Oryza sativa), a high Si-accumulating plant, is typically composed of amorphous silica bodies (namely phytoliths) that are deposited within the plant tissues. Recycling of rice straw is a traditional agricultural practice that introduces phytoliths into soil in many paddy regions. While the role of phytoliths as a carrier for nutrients, e.g., K, P, or terminal sink of Si, has been reported, it remains unclear to what extent phytolith can carry charges and act as a charge-interchange constituent in soils. Therefore, it was hypothesized that soil phytoliths can be involved in charge-related interactions e.g., pH buffering, multivalent cation exchange, polymerization, colloid stability or reactive transports. Based on a polyelectrolyte titration technique, our study evaluated surface charge (SC) dynamics of straw-derived phytoliths and paddy soils in the Mekong river and Red river deltas to characterize the possible contribution of phytoliths to soil SC properties. Phytoliths were extracted by both dry and wet ashing techniques and the SC of the obtained phytoliths were measured in the pH range from 3.5 to 8.0. The SC was detected to vary from slightly positive at low pH to –78.5 mmolc kg−1 at slightly alkaline pH, suggesting that these materials carry variable charges and could be a significant source of charge when they are returned to soil in relatively large quantities. Multiple regressions indicated that phytoliths, to some extents, can together with other soil constituents such as clay minerals, organic matter and iron oxides, regulate the SC of paddy soils. Despite phytoliths being more or less soluble, their SC properties suggest that the annual recycling of rice straw to paddy soils, particularly after burning, can contribute to the negative SC system. The phytolith-derived charge in turn might affect soil cation exchange capacity (CEC), dispersibility of clay particles and transport of solutes.

EFFECTS OF CENTELLA ASIATICA (L.) LEAF EXTRACT ON BONE CALCIUM AND PHOSPHATE LEVELS OF OVARIECTOMIZED RATS

Objective: This study aimed to evaluate the efficacy of Centella asiatica leaf extract in maintaining calcium and phosphate levels in the bone forpreventing osteoporosis in postmenopausal women.Methods: The obtained C. asiatica leaf extract was administered to ovariectomized rats at the doses of 60, 120, and 180 mg/kg body weight (BW)for 30 days. Subsequently, the rats were euthanized by ether overdose, and bone calcium and phosphate levels were determined by the wet ashingtechnique and spectrophotometry.Results: The results showed no significant differences in the bone calcium and phosphate levels among rats administered with different doses ofC. asiatica leaf extract.Conclusion: Our results indicate that C. asiatica leaf extract cannot be used as a source of phytoestrogens to maintain calcium and phosphate levelsin the bones.

Determining phytolith-occluded organic carbon sequestration using an upgraded optimized extraction method: indicating for a missing carbon pool.

Phytolith-occluded organic carbon (PhytOC) is considered one of the most promising terrestrial carbon (C) sinks. Different methods are used for phytolith extraction from wet-ashing techniques and the subsequent determination of PhytOC content from soil. This is in order to optimize the wet-ashing techniques and to improve estimation accuracy of C sequestration potential of phytoliths from soil. Results show that the organic matter removal and carbonate removal protocol, applying sonication, has a significant effect on phytolith extraction. Namely, the sequential removal of first organic matter and then carbonates applied to such methods could eliminate greater than 17.14, 46.68, and 26.17% extraneous material compared to other methods. Moreover, phytoliths extracted using methods that apply sonication eliminated 7.49, 42.70, and 17.57% more extraneous material than methods that did not. Additionally, the procedure associated with the second oxidation step significantly influenced the determination of PhytOC content, that is, 29.34, 33.75, 26.41, and 64.64% of excess organic C were oxidized during this step. The upgraded optimal method we recommend for phytolith extraction in association with wet-ashing techniques and the subsequent determination of PhytOC content is therefore to first apply sonication, then the second oxidation step, and finally the removal of organic matter. Using this optimal upgraded method, we estimated the C sequestration potential of phytoliths from the soil of slash pine in China at 0.51 Mt. C. Furthermore, using this upgraded optimal method increased the precision of the carbon sequestration potential of phytoliths from soil by up to 63.83%.

Investigation of heavy metal content of Turkish tobacco leaves, cigarette butt, ash, and smoke

A procedure for the determination of cadmium, copper, manganese, and zinc in Turkish tobaccos, which were of different origins, years, and grades, and in the butt, ash, and smoke, which were obtained by smoking the cigarettes that were prepared manually from the said tobaccos in a smoking apparatus, was devised as proposed. The collected samples were digested by wet ashing technique by using HNO3-HClO4 and were analyzed by flame atomic absorption spectrometry with satisfactory recoveries (94% to 98%). The regression coefficients were above 0.99, and the detection limits were in the range of 0.03-0.12 mg/L(-1). The performance and accuracy of the method was tested by analyzing "Certified Reference Material GBW 08501-Peach Leaves." The determined values were in agreement with the standard values for the heavy metals analyzed. Thus, it was concluded that the developed method could offer a wide range of application for establishing a relationship between the makeup and composition of tobacco plant, products, ash, smoke, and smoking.

Raman, infrared and XPS study of bamboo phytoliths after chemical digestion

Raman, infrared and X-ray photoelectron spectroscopies have been used to examine the effect of various chemical digestion methods on the composition of bamboo phytoliths. Intact bilobate phytoliths, suitable for interrogation by Raman microprobe analysis, were isolated by a microwave wet ashing technique using hydrogen peroxide with nitric and hydrochloric acids. The occluded phytolith carbon presented evidence of cellulose, lignin and carboxylic acids. Nitrate from the nitric acid used in the digestion was observed in homogenized samples of the isolated phytoliths; in addition to nitrogen of plant origin occluded within the phytolith, which was observed as amine nitrogen and ammonia. Intact bilobate phytoliths were not observed following an exothermic hydrogen peroxide/sulfuric acid digest, suggesting that these structures ruptured during this digestion procedure. The silicate network was significantly altered during isolation using the exothermic hydrogen peroxide/sulfuric digest, with surface hydroxyls undergoing condensation to form a SiO 3 ring structure.

Evaluation of triacid and dry ashing procedures for determining potassium, calcium, magnesium, iron, zinc, manganese, and copper in plant materials

Dry ashing and wet ashing techniques are routinely used for preparing plant materials for elemental analysis. The two techniques generally give similar results for the analysis of plant materials but differences have been observed in results using the two methods for elements such as calcium (Ca), iron (Fe), and zinc (Zn). We made a study to compare the dry ashing and triacid digestion procedures for determining potassium (K), Ca, magnesium (Mg), Fe, manganese (Mn), copper (Cu), and Zn in sorghum and rice plant samples having a range in concentration of these elements. For sorghum, the two procedures gave similar results for the determination of K, Mg, Mn, and Zn, the dry ashing procedure gave higher values for Ca, Fe, and Cu than those obtained using the triacid digestion procedure. For rice, the two procedures gave similar results for all nutrient elements except Ca for which the values were higher by the dry ashing procedure than with the triacid digestion procedure. Our results suggest that dry ashing technique provides more reliable results for the analysis of sorghum and rice plant materials for Ca and may be preferred over the triacid digestion procedure. Also, for sorghum plant samples dry ashing seemed more reliable for determination of Fe and Cu. Both dry ashing and triacid digestion methods appeared satisfactory for the determination of K, Mg, Mn, and Zn.

A Comparative Analysis of Wet and Dry Ashing Techniques for the Extraction of Phytoliths from Plant Material

Two methods are commonly used for the extraction of phytoliths from plant material to be used as reference in the analysis of archaeological phytolith samples: (1) spodograms or dry ashings; and (2) acid digestions or wet ashing. It has been suggested that these techniques may modify the resultant samples in different ways. Dry ashing, in particular, has been implicated as a cause of shrinkage and warping in phytolith assemblages when incineration occurs at ≥450°C. The results of a morphometric comparative analysis between the dry ashing and wet ashing methods do not support these claims. This study establishes that differences in patterns of dimension and curvature of short bilobate phytoliths and of elongate phytoliths both subjected to dry and wet ash preparation are not statistically significant. There is, therefore, no detectable evidence of morphological impact as a result of these methods. This finding implies that any differences that do occur in phytolith size and curvature are typical, possibly random permutation within assemblages, or that they are the result of variation in leaf cell structure rather than the consequence of a particular extraction procedure. This suggests that the practice of using different methods of preparation of reference samples for fossil analysis can be reliably continued.

Serum concentrations of zinc and copper in Bull Terriers with lethal acrodermatitis and tail-chasing behavior

Abstract Objective To establish similarities or differences in tissue concentrations of zinc, copper, and iron in Bull Terriers with lethal acrodermatitis (LAD) and tail-chasing behavior (TCB) and to confirm the suspicion that copper is involved in the etiopathogenesis of LAD. Samples Serum samples from 29 Bull Terriers (9 control dogs, 6 dogs with LAD, 14 dogs with TCB), and liver and kidney specimens from 2 dogs and 1 and 4 dogs with LAD or TCB, respectively. Procedure Serum, liver, and kidney mineral (zinc, copper, and iron) concentrations in Bull Terriers with LAD or TCB and in a group of control dogs were analyzed, using flame atomic absorption after wet ashing technique. Results Serum zinc and copper concentrations were lower (P < 0.05) in dogs with LAD, compared with values for control dogs and dogs with TCB. Liver zinc and copper concentrations were similar to serum values. Kidney zinc and copper concentrations were similar among the 3 groups. Serum, liver, and kidney iron concentrations had a wide range of variability within all 3 groups. Conclusion Copper deficiency is associated with LAD. The primary cause of LAD may be copper deficiency, with zinc involved secondarily, or combined zinc and copper deficiencies. The role of ion deficiency in TCB was not clarified. Clinical Relevance Serum zinc and copper concentrations should be determined when LAD is suspected. (Am J Vet Res 1997;58:808–810)

Modeling energy transfer in a focused microwave digestor

A physical model has been developed for studying microwave energy transfer and to predict temperature evolution of a liquid sample placed in an open microwave heating digestor. The thermal system was considered as involving three different media having different properties, i.e., the liquid sample, the glass flask and the microwave cavity. Energy balance equations were written taking into account conduction, convection and radiation heat transfer. The resolution of the differential equation set obtained gave the predicted temperatures. Experimental measurements of temperature were carried out with a thermocouple probe for several types of reagents classically used in wet ashing techniques. They were compared to predicted temperatures, and a Chi-squared parameter was used to estimate the fit of the model. The good results obtained demonstrated that this model can predict correctly the temperature of reagent heating in the presence of a microwave field. The addition of organic material did not significantly modify the results. It also produces abaci for predicting the time necessary to heat a reagent up to a given temperature. The model also gives a numerical estimation of the microwave energy loss during the transfer from the magnetron to the sample. It is then possible to explain some major differences observed between microwave ashing technique and conventional heating ashing technique, mainly the important reduction of time.

Analysis of trace elements in biological materials by microwave induced plasma-mass spectrometry

Analytical conditions have been established for determination of trace elements in biological materials by microwave induced plasma-mass spectrometry (MIP-MS). Possible elemental contaminants were checked in the water and reagents used, and during the wet-ashing process. Among 72 elements tested, contamination by Na, Mg, K, Ca, Fe, Ba, and Pb were observed. This contamination was estimated to occur mainly during the process of preparing samples due to the water, reagents and surroundings. Contamination by Ca, Mg, Zn and Pb from tubes for storage was also observed. Adequate conditions for multielement analyses in plasma and bone samples were evaluated. Both plasma and bone samples were digested by the wet-ashing technique before applying MIP-MS. The recovery rates of elements added were decreased depending on the contents of plasma or bone samples in the measuring solutions. The interfering effects of matrix modification due to organs were improved by correction with an internal standard. Recovery rates of elements added, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rb, Sr, Mo, Cd, Sn, Ba, Pb and fourteen lanthanide elements (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) were within 100 +/- 5% in analytical samples containing 1% volume of human plasma when Ga or Tl was used as the internal standard. Recoveries of Sn and Zn in the bone samples containing 0.1% bone as the original bone material, however, were 100 +/- 10% even after correction by the internal standard, suggesting the necessity of combined use of standard addition methods. The concentrations of V, Cr, Mn, Fe, Cu, Zn, Rb, Sr, Mg, and Ca in plasma from two healthy women were determined by MIP-MS. The data were consistent with the values reported elsewhere, and agreed very closely with those obtained by atomic absorption spectrometry. The accuracy of the values obtained by this method was confirmed using standard reference materials. These results indicate that MIP-MS is a useful method for multielement determination of biological materials.

The determination of platinum in biological materials by electrothermal atomic absorption spectroscopy

Methods for determination of platinum in body tissues and fluids by electrothermal atomic absorption spectroscopy are described. Serum and urine could be analyzed without pretreatment or dilution. Wet and dry ashing techniques for tissue digestion were compared. Dry ashing tissues in a furnace resulted in significant and unexplained losses of analyte, whereas there was complete recovery of platinum added to the tissues when the tissues were wet ashed. The wet ashing technique is fast and convenient and requires minimal sample treatment.

Dry- and wet-ashing techniques compared in analyses for zinc, copper, manganese, and iron in hair.

Preparation of hair specimens for trace-metal analyses is routinely done by wet- or dry-ashing. Wet-ashing is more time consuming than dry-ashing and can be dangerous. We wished to determine if dry-ashing was a suitable alternative to wet-ashing with HClO4:HNO3 or HNO3 alone in preparing hair for measurement of zinc, copper, iron, and manganese by atomic absorption spectroscopy. Concentrations of Zn, Cu, and Mn were not differently affected in hair that was dry- or wet-ashed. Analytical recovery of these elements added to hair samples ranged from 102 to 108%; day-to-day CVs were less than 5%. Fe was lost during dry-ashing of hair, and wet-ashing with HNO3 produced results for Fe comparable with those obtained with HClO4:HNO3. Therefore we recommend dry-ashing of hair to be analyzed for Zn, Cu, and Mn, but wet-ashing with HNO3 for assays of Fe.

A comparative survey of the Erpobdella octoculata (L.) populations in the Afon Crafnant, N. Wales, above and below an input of zinc from mine-waste

The life-cycle, growth, and reproductive success of a stream-dwelling Erpobdella octoculata (L.) were studied over a 19-month period at two sites, one above and one below an input of zinc pollution from mine-waste. Samples were collected monthly using quadrats. The blotted wet weight of all leeches was measured. An histological technique was employed to determine sexual maturity. Reproductive success was measured by estimating the numbers of cocoons and number of eggs per cocoon at each site. A wet ashing technique, followed by analysis using flame atomic absorption spectrometry, was used to determine the extent of bioaccumulation of zinc. ‘Total’ zinc and other metals in the waters were similarly analysed.

Determination of Radium-228 in Foods and Water

A procedure was developed for the rapid determination of 228Ra by measuring its decay product 228Ac. The method is applicable to a variety of types of samples such as food and water. Food samples can be prepared by dry- or wet-ashing techniques. The 228Ac is precipitated with lanthanum carrier, dissolved, purified by solvent extraction, and finally decontaminated on anion and cation exchange resins. The 228Ac is counted in a thin-window, low-level gas flow beta counter. It may be necessary to count the sample several times to follow the 6 h half-life of 228Ac so that its purity is ensured. The method is sensitive to 1 pCi/sample of food ash and to 1 pCi/L of water.

Precautions in Ashing Techniques for Lead Determination in Food

In determining lead in food, the matrix must be destroyed before quantitation by atomic absorption spectrophotometry. Wet or dry ashing techniques are generally used. Dry ashing assisted by ultrapure H2SO4 or K2SO4 has the advantages of safety, low reagent blanks, rapidity, and good recoveries of added lead. These techniques are also less labor-intensive than wet ashing.

Trace mercury analysis in biological material: use of 203Hg-labelled methylmercury chloride for in vivo labelling of fish to study the efficacy of various wet ashing procedures

Several wet ashing techniques for trace mercury analysis by cold vapour atomic absorption have been evaluated with radiotracer mercury, and in particular fish labelled in vivo with 203Hg-tagged methylmercury chloride. Partial digestion methods suffer from strong matrix effects; these include incomplete extraction from the sample, hold-back of mercury in the extraction solution during the reduction/aeration step, and alteration of the aeration release pattern so as to cause low results if measurement is based on peak height. A complete digestion method is outlined; this gives good results and is tentatively recommended pending further tests with other types of biological samples.

Collaborative Study of Wet and Dry Ashing Techniques for the Elemental Analysis of Plant Tissue by Atomic Absorption Spectrophotometry

Abstract Seven laboratories participated in a collaborative study of wet ashing of plant material with a nitric-perchloric acid mixture and dry ashing at 500°C in order to determine the elements calcium, copper, iron, magnesium, manganese, potassium, and zinc by atomic absorption spectrophotometry. Five different homogeneous leaf tissue samples were analyzed and a synthetic standard solution containing all of the elements studied was included to evaluate sample preparation errors independent of instrument errors. The results indicated that plant tissue preparation by either wet or dry ashing gave similar elemental composition results for the tissues analyzed. The wet and dry ashing techniques have been adopted as official first action.

Cell wall-associated inorganic substances from Pseudomonas aeruginosa.

Cell walls of Pseudomonas aeruginosa were digested by a wet-ashing technique and analyzed for 12 different cations. The results indicated that these cell wall-associated inorganic substances can be classed broadly into major, minor, and trace elements. Phosphorus, K+, Mg2+, and Ca2+ were considered major elements since they are present in relatively high concentrations; Na+ and Fe3+ were considered minor elements; and, Zn2+, Pb2+, Co2+, Cu2+, Mn2+, and Sr2+ were considered trace elements.

Determination of chelated iron in the urine.

A simplified wet-ashing technique is described for the determination of chelated iron in the urine, with special reference to DTPA-bound iron. The procedure dispenses with the need for quantitative transfer, and gives corresponding economy in time, labour, and glassware without loss of precision. The standard error of the mean estimate of a triplicate determination, using four reference standards, is +/- 4 mug/100 ml; precision may be further increased by the use of a calibration curve based on many standards.

A dry ashing method for the determination of blood lead using cathode ray polarography. Comparison with a wet ashing technique.

A dry ashing method is described for the determination of lead in whole blood. Within the range of 16-200 μg. lead per 100 ml. blood recoveries were 82 to 100%. The method agreed with a standard wet method and is more convenient. Possible sources of error and the uses of the ashing aid are discussed.