USGS-NWQL: B-9001-95 (ICP-AES):  Trace Metals in Aquatic Biological Material by ICP-AES

  • Summary
  • Analytes
  • Revision
  • Data and Sites
Official Method Name
Preparation Procedure for Aquatic Biological Material Determined for Trace Metals
Current Revision
1996
Media
ANIMAL TISSUE
Instrumentation
Inductively Coupled Plasma - Atomic Emission Spectroscopy
Method Subcategory
Sampling/Preparation
Method Source
  USGS-NWQL
Citation
Hoffman, G.L., 1996, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory -- Preparation procedure for aquatic biological material determined for trace metals: U.S. Geological Survey Open-File Report 96-362.
Brief Method Summary
Up to 20 g of wet tissue is placed into a tared 200-mL Pyrex beaker and weighed. The sample is placed in a constant-temperature oven and dried at 65oC over several days until constant weight is obtained. The sample is digested by first heating it with nitric acid and then by the careful addition of 30% hydrogen peroxide. Insoluble material (silica or sediment) is removed by filtration. Trace metals determined in the solutions are reported in micrograms per gram (ug/g) of dry-tissue weight.
Scope and Application
This method provides sample-preparation procedures for the nitric acid digestion of biological tissue for the subsequent determination of trace metals. The method is applicable to aquatic biological tissue and aquatic plant material only and is not applicable to bivalve shells, bones, and sediment material contained in bivalves.
Applicable Concentration Range
> 0.01 ug/g
Interferences
Chloride concentrations greater than 0.01% can cause analytical problems for ICP-MS used to determine trace metals by this digestion method. Therefore, hydrochloric acid was not used during the digestion procedure. The digested samples also were evaporated to near dryness and reconstituted with 5% nitric acid to remove all chloride present in the digested samples.
A clean working environment is required (Katz, 1984). The use of a class-100 clean bench during all manipulations, including filtration, drying of cleaned glassware, and acid rinsing of filters, is mandatory.
Quality Control Requirements
QC for digestion procedure: Digest a synthetic biological material that is based on National Institute of Standards and Technology (NIST) Oyster tissue, SRM 1655a; NIST Bovine liver, SRM 1577a; and/or NIST Peach leaves, SRM 1547. Also digest a process blank consisting of all reagents used in the tissue-digestion procedure. QC for ICP-AES analysis: Analyze a quality-control sample immediately following calibration and after every tenth sample. Minimum quality-control requirements per set must include analysis of a laboratory reagent blank and quality-control samples, such as SRWS, and may include check standards, sample duplicates, and sample spikes. The sample set must also include a synthetic biological material that is based on an NIST SRM. The sample set must also include a process blank to verify the accuracy of the procedure. Correlation coefficients for calibration curves must be at least 0.999. QC samples must fall within 1.5 standard deviations of the mean value. If all of the data-acceptance criteria in the SOPs are met, then the analytical data are acceptable.
Sample Handling
Biological material must be frozen when received at the laboratory, packed with dry ice in an insulated cooler. Inspect all resealable bags to ensure the integrity of the bag and the condition of the samples. Record the condition of all compromised samples (torn bags or samples not frozen) in the sample preparation notebook. Inform the investigator who shipped the samples of their compromised condition. Double bag tissue samples in resealable polyethylene freezer bags and store in a freezer maintained at less than or equal to -10oC until sample preparation.
Maximum Holding Time
It is possible to maintain the inorganic chemical integrity of frozen biological samples for years provided the samples are not thawed and refrozen.
Relative Cost
$51 to $200
Sample Preparation Methods