A Branch of Ecological Services
Select one of the links below to display the method descriptions associated with AWH.
Tissue Sample Preparation
We possess an array of Tissumizers for homogenization and well as ceramic, stainless steel and titanium knives that are used for filleting and dissecting.Back to the Top
Inductively Coupled Plasma-Mass Spectrometry
Solid samples (approximately 1g) were digested by hot plate or microwave according to EPA Method 3050 (hot plate) or EPA Method 3051 (microwave). An aliquot of digestate was nebulized into a spray chamber where a stream of argon carried the sample aerosol through a quartz torch and injected it into the radio frequency inductively coupled plasma. The ions produced in the plasma were introduced to the mass spectrometer for quantification against a multi-level initial calibration.Back to the Top
Mercury via Cold Vapor Atomic Absorption Spectroscopy
Solid samples (approximately 1g) were digested in a diluted potassium permanganate solution, and heated for 30 minutes. Mercury in the digested sample was reduced to elemental mercury and aerated from solution in a closed system. Mercury vapor passed through a cell positioned in the light path of the atomic absorption spectrophotometer. The absorbance was measured and was compared to a multi-level initial calibration for quantification.Back to the Top
Mercury via cold Vapor Atomic Fluorescence Spectroscopy
Tissue samples (approximately 1g) are digested according to Method 3051. Soil/sediment samples (approximately 1 g) are digested by hot plate in aqua regia. An aliquot of the digest is then prepared with HCL/BrCl and hydroxylamine hydrochloride solution. Mercury in the digested sample is reduced to elemental mercury, aerated from solution and introduced into the spectrophotometer. The emission is measured and compared to a multi-level initial calibration for quantification
Total Organic Carbon
Solid samples are dried, acidified with phosphoric acid, loaded into an aluminum tin, and introduced into a furnace for combustion in a pure oxygen environment. CO 2 is produced in the combustion zone and non-target elements are removed by scrubbing reagents. The resulting CO 2 gas is de-pressurized through a column where it is detected as a function of its thermal conductivity. The amount of CO 2 derived from the sample is directly proportional to the concentration of organic carbonaceous material in the sample.
Particle Size is determined according to ASTM Method D422-63 (Re-approved 1998) by the distribution of particle sizes larger than 75 mm retained on the number 200 sieve, determined by sieving, while the distribution of particle sizes smaller then 75 mm was determined by using a hydrometer. Sediment samples are dried and homogenized, and separated it into two fractions using a number 10 sieve (2 mm). The fraction that remained on the number 10 sieve is washed with tap water, dried in an oven and mechanically sieved with an array of sieve sizes that separate the sample into the various gravel and course fractions. The fraction of sample that passes through the number 10 sieve is subjected to a two part process. First, a hydrometer test is performed which defines the fraction of sample that is silt and clay. Second, the sample from the hydrometer test is transferred to a number 200 sieve and washed with tap water to remove all particles less than 75 mm. The sample remaining on the number 200 sieve is then dried in an oven and mechanically sieved with an array of sieve sizes that defined the medium and fine sands present in the sample
Water content is determined by weighing a representative sample aliquot and drying the aliquot in an oven at 110°C to a constant mass. The loss of mass due to the sample drying expressed as a percentage is considered to be percent moisture
Inorganic Anions by Ion Chromatography in Aqueous samples and aqueous extracts of solid/sediment samples.
A five ml aliquot of sample is injected into a stream of carbonate-bicarbonate eluant and passed through three different ion exchange columns. The first two columns are packed with a low-capacity, strongly basic anion exchanger. The anions elute at different rates based on their affinity for the exchange sites on the anion exchange resin. The anions are then directed into a third column, which is a suppressor column that reduces the carbonate-bicarbonate eluant to weakly conductive carbonic acid and also converts the anions to their corresponding highly conductive acid form. The anions are qualitatively identified based on their retention times in comparison to the retention times of anions in standards. The separated anions in their acid form are measured quantitatively by conductivity. Peak height s or peak areas are used to calculate the anion concentration.