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Title: Determination of the Efficiency of Mixed-Acid Digestions of Sediments

Abstract

Mixed-acid digestion is a method often used for the determination of elemental analysis of sediment samples. It is crucial that efficiency details associated with the digestion method be well understood on an element by element basis. Battelle’s Marine Sciences Laboratory Standard Operating Procedure for Sediment Mixed-Acid Digestions was modified to identify conditions which produce optimal recovery of elements. The parameters that were adjusted for testing were mass of sediment, mixed-acid volume, mixed-acid composition and digestion time. Digestion involves treatment of the sediment sample with mixed-acid mixtures at 135º C ± 10º in a Teflon® digestion bomb. Typical analytical methods include Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) and Inductively Coupled Plasma – Mass Spectrometry (ICP-MS). Initial experiments involved determining the optimal ratio of acid volume to mass of sediment. Experiments were designed to identify the point at which insufficient acid was used to effectively digest a given mass of sediment. When the mass of sediment was varied between 0.2 and 1.0 gram using a 4 mL aqua regia acid mixture (3 mL hydrochloric acid and 1 mL nitric acid), there was no effect on the recovery of the elements Al, Ba, Ca, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb,more » Sr, Ti, V, and Zn. The next experiments focused on a time study to resolve the shortest digestive time for optimal elemental recovery. Two masses of sediment were investigated, 0.25 and 0.7 g, again utilizing aqua regia digestion (4 mL). Maximum recovery was reached after 4 hours of digestion; additional digestion time released no or only minimal amounts of elements from the sediments. The final set of experiments was designed to identify optimal conditions for the total digestion of sediment using a mixture of hydrochloric acid, nitric acid, hydrofluoric acid, hydrogen peroxide, and boric acid. These experiments were designed to determine the optimal volume of hydrofluoric acid needed to achieve a total digestion. Utilizing two masses of sediment 0.25 and 0.5 g and varying the volume of hydrofluoric acid and boric acid. Total digestion was achieved with a minimum volume of 0.5 mL hydrofluoric acid and a .25 g of sediment. Future experiments incorporating the findings in these experiments will be executed using a heated carbon block as the source for thermal energy.« less

Authors:
;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
993373
Report Number(s):
PNNL-SA-51400
TRN: US201023%%220
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Undergraduate Research, VII:150; Journal Volume: 7
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 54 ENVIRONMENTAL SCIENCES; SEDIMENTS; DISSOLUTION; AQUA REGIA; BORIC ACID; EFFICIENCY; HYDROFLUORIC ACID; HYDROGEN PEROXIDE; MIXTURES; PERFORMANCE TESTING; MULTI-ELEMENT ANALYSIS

Citation Formats

Huerta Vazquez, Alejandra I., and Gill, Gary A. Determination of the Efficiency of Mixed-Acid Digestions of Sediments. United States: N. p., 2007. Web.
Huerta Vazquez, Alejandra I., & Gill, Gary A. Determination of the Efficiency of Mixed-Acid Digestions of Sediments. United States.
Huerta Vazquez, Alejandra I., and Gill, Gary A. Mon . "Determination of the Efficiency of Mixed-Acid Digestions of Sediments". United States. doi:.
@article{osti_993373,
title = {Determination of the Efficiency of Mixed-Acid Digestions of Sediments},
author = {Huerta Vazquez, Alejandra I. and Gill, Gary A.},
abstractNote = {Mixed-acid digestion is a method often used for the determination of elemental analysis of sediment samples. It is crucial that efficiency details associated with the digestion method be well understood on an element by element basis. Battelle’s Marine Sciences Laboratory Standard Operating Procedure for Sediment Mixed-Acid Digestions was modified to identify conditions which produce optimal recovery of elements. The parameters that were adjusted for testing were mass of sediment, mixed-acid volume, mixed-acid composition and digestion time. Digestion involves treatment of the sediment sample with mixed-acid mixtures at 135º C ± 10º in a Teflon® digestion bomb. Typical analytical methods include Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) and Inductively Coupled Plasma – Mass Spectrometry (ICP-MS). Initial experiments involved determining the optimal ratio of acid volume to mass of sediment. Experiments were designed to identify the point at which insufficient acid was used to effectively digest a given mass of sediment. When the mass of sediment was varied between 0.2 and 1.0 gram using a 4 mL aqua regia acid mixture (3 mL hydrochloric acid and 1 mL nitric acid), there was no effect on the recovery of the elements Al, Ba, Ca, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Sr, Ti, V, and Zn. The next experiments focused on a time study to resolve the shortest digestive time for optimal elemental recovery. Two masses of sediment were investigated, 0.25 and 0.7 g, again utilizing aqua regia digestion (4 mL). Maximum recovery was reached after 4 hours of digestion; additional digestion time released no or only minimal amounts of elements from the sediments. The final set of experiments was designed to identify optimal conditions for the total digestion of sediment using a mixture of hydrochloric acid, nitric acid, hydrofluoric acid, hydrogen peroxide, and boric acid. These experiments were designed to determine the optimal volume of hydrofluoric acid needed to achieve a total digestion. Utilizing two masses of sediment 0.25 and 0.5 g and varying the volume of hydrofluoric acid and boric acid. Total digestion was achieved with a minimum volume of 0.5 mL hydrofluoric acid and a .25 g of sediment. Future experiments incorporating the findings in these experiments will be executed using a heated carbon block as the source for thermal energy.},
doi = {},
journal = {Journal of Undergraduate Research, VII:150},
number = ,
volume = 7,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • The determination of acid-volatile sulfide (AVS) and simultaneously extracted metals (SEMs) in sediment by treatment with dilute HCl shows promise as a tool for predicting the potential for metal toxicity to sediment-dwelling organisms. Effective quality control measures must be developed if this method is to become a reliable procedure and to ensure comparability of data. However, establishing quality control measures that assess procedural errors for an operationally defined method can be problematic. For example, preextraction spikes added for assessing the accuracy of AVS and SEMs may be poorly recovered due to adsorption or reaction with sediment constituents. For a varietymore » of sediment types, the authors found preextraction spikes of sulfide, mercury, and copper to be prone to variable recoveries for the AVS/SEM procedure; recoveries averaged 76.3% (SD, 20.9) for sulfide, 61.9% (39.6) for Hg, and 90.1% (12.7) for Cu. The average recovery was near 100% for preextraction spikes of sediments for Cd, Ni, Pb, and Zn, and the recoveries of preextraction blank spikes for all analytes were consistently 95 to 105%. Binding of Cu or Hg with sulfides is sufficiently strong that 1 N hydrochloric acid will not necessarily keep the spiked metal in the dissolved state. This does not mean that the SEM procedure is invalid for these metals, only that the quality control of procedural error is difficult to assess. However, Hg will generally not be detected when measured as an SEM because of its tendency to adsorb onto sulfide minerals even at extremely low pH. Some reference sediments may be useful for assessing consistency of AVS determinations; they measured 5.97 {+-} 0.65 {micro}mol/g in NIST 1645 and 1.34 {+-} 0.14 {micro}mol/g in NIST 2704 for repeated determinations conducted over the past 3 years. Apparently, some sediments may contain an oxidation-resistant sulfide component that can release low to moderate AVS when treated with dilute HCl.« less
  • The /sup 27/Al NMR line width and the spin-spin relaxation rate of the hexaaquoaluminum ion in aqueous perchloric acid and mixed acetone/aqueous perchloric acid solutions are summarized. The noted increase in the line width of the Al(H/sub 2/O)/sub 6//sup 3+/ resonance with the addition of acetone is interpreted as being due to a decrease in the molecular tumbling rate of the Al(H/sub 2/O)/sub 6//sup 3+/ ion in a more viscous solvent medium. The estimated and calculated values of the quadrupole coupling constant for Al(H/sub 2/O)/sub 6//sup 3+/ have been confirmed by experimental values reported herein. Data in mixed acetone/water solventmore » mixtures indicate that the integrity of Al(H/sub 2/O)/sub 6//sup 3+/ is preserved and acetone does not compete effectively with H/sub 2/O for coordination sites on the Al/sup 3+/(aq) cation.« less
  • Niobium(V) was determined as a mixed ligand complex with gallic acid and 1,2-diaminocyclohexanetetraacetic acid in tartrate medium by a spectrophotometric method at 470 nm around pH 2.5, 40 minutes after preparation of the solution and at 25/sup 0/C. The system conforms to Beer's law for an optimum range of 0.38 to 8.92 ..mu..g/ml of niobium with relative standard deviation of 2 to 5 percent. Sensitivity (A = 0.001 and 1-cm path length) is 0.015 ..mu..g/ml of niobium. The behavior of many ions was studied for their interference in determination of niobium and, in a few synthetic cation mixtures, niobium wasmore » estimated. (auth)« less