METHOD 3052
MICROWAVE ASSISTED ACID DIGESTION OF SILICEOUS AND
ORGANICALLY BASED MATRICES
1.0 SCOPE AND APPLICATION
1.1This method is applicable to the microwave assisted acid digestion of siliceous matrices, and organic matrices and other complex matrices. If a total decomposition analysis (relative to the target analyte list) is required, the following matrices can be digested: ashes, biological tissues, oils, oil contaminated soils, diments, sludges, and soils. This method is applicable for the following elements:
Aluminum Cadmium Iron Molybdenum Sodium
Antimony Calcium Lead Nickel Strontium
Arnic Chromium Magnesium Potassium Thallium
Boron Cobalt Mangane Selenium Vanadium
Barium Copper Mercury Silver Zinc
Beryllium
Other elements and matrices may be analyzed by this method if performance is demonstrated for the analyte of interest, in the matrices of interest, at the concentration levels of interest (e Sec.
8.0).
Note: This technique is not appropriate for regulatory applications that require the u of leachate preparations (i.e., Method 3050, Method 3051, Method 1311, Method 1312, Method 1310, Method 1320, Method 1330, Method 3031, Method 3040). This method is appropriate for tho applications requiring a total decomposition for rearch purpos (i.e., geological studies, mass balances, analysis of Standard Reference Materials) or in respon to a regulation that requires total sample decomposition.
1.2This method is provided as a rapid multi-element, microwave assisted acid digestion prior to analysis protocol so that decisions can be made about the site or material. Digests and alternative procedures produced by the method are suitable for analysis by flame atomic absorption spectromet
ry (FLAA), cold vapor atomic absorption spectrometry (CVAA), graphite furnace atomic absorption spectrometry (GFAA), inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS) and other analytical elemental analysis techniques where applicable. Due to the rapid advances in microwave technology, consult your manufacturer's recommended instructions for guidance on their microwave digestion system and refer to this manual’s "Disclaimer" when conducting analys using Method 305
2.
1.3The goal of this method is total sample decomposition and with judicious choice of acid combinations this is achievable for most matrices (e Sec. 3.2). Selection of reagents which give the highest recoveries for the target analytes is considered the optimum method condition. CD-ROM3052 - 1Revision 0
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2.0SUMMARY OF METHOD
2.1 A reprentative sample of up to 0.5 g is digested in 9 mL of concentrated nitric acid and usually 3 mL hydrofluoric acid for 15 minutes using microwave heating with a suitable laboratory microwave system. The method has veral additional alternative acid and reagent combinations including hydrochloric acid and hydrogen peroxide. The method has provisions for scaling up the sample size to a maximum of 1.0 g. The sample and acid are placed in suitably inert polymeric microwave vesls. The vesl is aled and heated in the microwave system. The temperature profile is specified to permit specific reactions and incorporates reaching 180 ± 5 ºC in approximately less than 5.5 minutes and remaining at 180 ± 5 ºC for 9.5 minutes for the completion of specific reactions (Ref. 1, 2, 3, 4). After cooling, the vesl contents may be filtered, centrifuged, or allowed to ttle and then decanted, diluted to volume, and analyzed by the appropriate SW-846 method.
3.0INTERFERENCES
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3.1Gaous digestion reaction products, very reactive, or volatile materials that may create high pressures when heated and may cau venting of the vesls with potential loss of sample and analytes. The complete decomposition of either carbonates, or carbon bad samples,may cau e
nough pressure to vent the vesl if the sample size is greater than 0.25 g. Variations of the method due to very reactive materials are specifically addresd in ctions 7.3.4 and 7.3.6.1.
3.2Most samples will be totally dissolved by this method with judicious choice of the acid combinations. A few refractory sample matrix compounds, such as TiO 2, alumina, and other oxides may not be totally dissolved and in some cas may quester target analyte elements.
3.3The u of veral digestion reagents that are necessary to either completely decompo the matrix or to stabilize specific elements may limit the u of specific analytical instrumentation methods. Hydrochloric acid is known to interfere with some instrumental analysis methods such as flame atomic absorption (FLAA) and inductively coupled plasma atomic emission spectrometry (ICP-AES). The prence of hydrochloric acid may be problematic for graphite furnace atomic absorption (GFAA) and inductively coupled plasma mass spectrometry (ICP-MS).Hydrofluoric acid, which is capable of dissolving silicates, may require the removal of excess hydrofluoric acid or the u of specialized non-glass components during instrumental analysis.Method 3052 enables the analyst to lect other decomposition reagents that may also cau problems with instrumental analys necessitating matrix matching of standards to account for viscosity and chemical differences.
4.0APPARATUS AND MATERIALS
4.1Microwave apparatus requirements.
4.1.1The temperature performance requirements necessitate the microwave
decomposition system n the temperature to within ± 2.5E C and automatically adjust the microwave field output power within 2 conds of nsing. Temperature nsors should be accurate to ± 2E C (including the final reaction temperature of 180E C). Temperature feedback control provides the primary control performance mechanism for the method. Due to the flexibility in the reagents ud to achieve total analysis, tempertuare feedback control is necessary for reproducible microwave heating.
Alternatively, for a specific t of reagent(s) combination(s), quantity, and specific vesl type, a calibration control mechanism can be developed similar to previous microwave methods (e Method 3051). Through calibration of the microwave power, vesl load and heat loss, the reaction temperature profile described in Section 7.3.6 can be reproduced.
The calibration ttings are specific for the number and type of vesl ud and for the microwave system in addition to the variation in reagent combinations. Therefore no specific calibration ttings are provided in this method. The ttings may be developed by using temperature monitoring equ
ipment for each specific t of equipment and reagent combination. They may only be ud if not altered as previously described in other methods such as 3051 and 3015. In this circumstance, the microwave system provides programmable power which can be programmed to within ± 12 W of the required power.
Typical systems provide a nominal 600 W to 1200 W of power (Ref. 1, 2, 5). Calibration control provides backward compatibility with older laboratory microwave systems without temperature monitoring or feedback control and with lower cost microwave systems for some repetitive analys. Older lower pressure vesls may not be compatible.
4.1.2The temperature measurement system should be periodically calibrated at an
elevated temperature. Pour silicon oil (a high temperature oil into a beaker and adequately stirred to ensure a homogeneous temperature. Place the microwave temperature nsor and a calibrated external temperature measurement nsor into the beaker. Heat the beaker to a constant temperature of 180 ± 5°C. Measure the temperature with both nsors. If the measured temperatures vary by more than 1 - 2°C, the microwave temperature measurement system needs to be calibrated. Consult the microwave manufacturer’s instructions about the specific temperature nsor calibration procedure.
CAUTION: The u of microwave equipment with temperature feedback control is
required to control the unfamiliar reactions of unique or untested reagent
combinations of unknown samples. The tests may require additional vesl
requirements such as incread pressure capabilities.
4.1.3The microwave unit cavity is corrosion resistant and well ventilated. All
electronics are protected against corrosion for safe operation.
爱情小作文CAUTION: There are many safety and operational recommendations specific to the
model and manufacturer of the microwave equipment ud in individual laboratories.
A listing of the specific suggestions is beyond the scope of this method and require
the analyst to consult the specific equipment manual, manufacturer, and literature for
proper and safe operation of the microwave equipment and vesls.
4.1.4The method requires esntially microwave transparent and reagent resistant
suitably inert polymeric materials (examples are PFA or TFM suitably inert polymeric polymers) to contain acids and samples. For higher pressure capabilities the vesl may be contained within layers of different microwave transparent materials for strength, durability, and safety. The vesls internal volume should be at least 45 mL, capable of withstanding pressures of at least 30 atm (30 bar or 435 psi), and capable of controlled pressure relief.
The specifications are to provide an appropriate, safe, and durable reaction vesl of which there are many adequate designs by many suppliers.
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CAUTION: The outer layers of vesls are frequently not as acid or reagent resistant
as the liner material and must not be chemically degraded or physically damaged to
retain the performance and safety required. Routine examination of the vesl
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materials may be required to ensure their safe u.
CAUTION: The cond safety concern relates to the u of aled containers without
pressure relief devices. Temperature is the important variable controlling the
reaction. Pressure is needed to attain elevated temperatures, but must be safely
contained. However, many digestion vesls constructed from certain suitably inert
polymerics may crack, burst, or explode in the unit under certain pressures. Only
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蝴蝶英语suitably inert polymeric (such as PFA or TFM and others) containers with pressure
relief mechanisms or containers with suitably inert polymeric liners and pressure
relief mechanisms are considered acceptable.
Urs are therefore advid not to u domestic (kitchen) type microwave ovens or
to u inappropriate aled containers without pressure relief for microwave acid
digestions by this method. U of laboratory-grade microwave equipment is required
to prevent safety hazards. For further details, consult Reference 3 and 6.
4.1.5 A rotating turntable is employed to insure homogeneous distribution of
microwave radiation within most systems (Ref. 1). The speed of the turntable should be a minimum of 3 rpm.
CAUTION: Laboratories should not u domestic (kitchen) type microwave ovens for
this method. There are veral significant safety issues. First, when an acid such as
nitric is ud to effect sample digestion in microwave units in open vesl(s), or
aled vesls equipment, there is the potential for the acid gas vapor relead to字迷
corrode the safety devices that prevent the microwave magnetron from shutting off
when the door is opened. This can result in operator exposure to microwave energy.
U of a system with isolated and corrosion resistant safety devices prevents this
from occurring.
4.2Volumetric ware, volumetric flasks, and graduated cylinders, 50 and 100 mL capacity or equivalent.
4.3 Filter paper, qualitative or equivalent.
4.4 Filter funnel, polypropylene, polyethylene or equivalent.
4.5Analytical balance, of appropriate capacity, with a ± 0.0001 g or appropriate precision for the weighing of the sample. Optionally, the vesl with sample and reagents may be weighed, with an appropriate precision balance, before and after microwave processing to evaluate the al integrity in some vesl types.
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刻薄成家December 19965.0REAGENTS
5.1All reagents should be of appropriate purity or high purity (acids for example, should be sub-boiling distilled where possible) to minimize the blank levels due to elemental contamination.All references to water in the method refer to reagent water (Ref. 7). Other reagent grades may be ud, provided it is first ascertained that the reagent is of sufficient purity to permit its u without lesning the accuracy of the determination. If the purity of a reagent is questionable, analyze the reagent to determine the level of impurities. The reagent blank must be less than the MDL in order to be ud.
6.0SAMPLE COLLECTION, PRESERVATION, AND HANDLING形容夏天的句子
6.1All samples must have been collected using a sampling plan that address the considerations discusd in Chapter Nine of this manual.
6.2All sample containers must be prewashed with detergents, acids, and water. Plastic and glass containers are both suitable. See Chapter Three, Sec. 3.1.3 of this manual, for further information.
6.3
Refer to Chapter Three for the appropriate holding times and storage conditions.7.0PROCEDURE
7.1Temperature control of clod vesl microwave instruments provides the main feedback control performance mechanism for the method. Control requires a temperature nsor in one or more vesls during the entire decomposition. The microwave decomposition system should n the temperature to within ± 2.5 C and permit adjustment of the microwave output o power within 2 conds.
7.2 All digestion vesls and volumetric ware must be carefully acid washed and rind with reagent water. When switching between high concentration samples and low concentration samples, all digestion vesls (fluoropolymer liners only) should be cleaned by leaching with hot (1:1)hydrochloric acid (greater than 80C, but less than boiling) for a minimum of two hours followed with o hot (1:1) nitric acid (greater than 80C, but less than boiling) for a minimum of two hours and rind o with reagent water and dried in a clean environment. This cleaning procedure should also be ud whenever the prior u of the digestion vesls is unknown or cross contamination from vesls is suspected. Polymeric or glass volumetric ware (not ud with HF) and storage containers should be cleaned by leaching with more dilute acids (approximately 10% V/V) appropriate for the specific plastics ud and then rind with reagent water and dried in a clean environment. To avoid precipitation of silver, ensure that all HCl has been rind from the vesls.
7.3Sample Digestion
7.3.1Weigh a well-mixed sample to the nearest 0.001 g into an appropriate vesl
equipped with a pressure relief mechanism. For soils, ash, diments, sludges, and siliceous wastes, initially u no more than 0.5 g. For oil or oil contaminated soils, initially u no more than 0.25 g.
