ASTM D7111 Standard Test Method for Determination of Trace Elements in Middle Distillate Fuels by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES)
7. Apparatus
7.1 Inductively-Coupled Plasma Atomic Emission Spectrometer - Any commercial sequential or simultaneous ICP-AES instrument capable of measuring emission intensities of the elements of interest (and listed in Table 1). A vacuum or inert gas optical path is required for analysis of any element at wavelengths below 190 nm.
7.2 Nebulizer - For samples without particulates, a concentric nebulizer is recommended to provide higher sensitivity for low concentrations and for low sensitivity elements. For unknown samples, a Babington-type high solids nebulizer is recommended to reduce the possibility of clogging from particulate.
7.3 Spray Chamber, suitable for organic materials.
7.4 Peristaltic Pump - A peristaltic pump is required to provide a constant flow of liquid to the ICP. Viton pump tubing is recommended for use with fuels and kerosine.
7.5 Membrane Filter, 47 mm diameter, 0.8 µm or 1.0 µm pore size.
7.6 Membrane Filter Holder Assembly, for 47 mm diameter filters, with filtration flask.
7.7 Pipette, 1000 µL.
7.8 Volumetric Flasks, 25 mL and 50 mL, glass.
7.9 Glass or High Density Polyethylene (HDPE) Bottles, 125 mL, round.
7.10 Analytical Balance, measuring to 0.0001 g.
8. Reagents and Materials
8.1 Purity of Reagents - Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all reagents conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society where such specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use without lessening the accuracy of the determination.
8.2 Organometallic Standards, single element and multielement organometallic standards, nominal 100 mg/kg of each element of interest.
8.3 Internal Standard, fuel soluble yttrium, cobalt, scandium or other single element organometallic standard, not a component of the fuel test specimen or calibration standard, nominal 5000 mg/kg.
8.4 Kerosine, with analyte concentrations below the detection limits of the instrument. The kerosine can be screened for the presence of analytes as detailed in 12.1 by performing a wavelength scan for analyte wavelengths.
8.5 Argon Gas, 99.995 % minimum purity. (Warning - Argon may be a compressed gas under high pressure.)
8.6 Nitrogen Gas, 99.999 % minimum purity. (Warning - Nitrogen may be a compressed gas under high pressure.)
8.7 Nitric Acid, 10 % aqueous solution. (Warning - Nitric acid may cause severe burns.)
8.8 Quality Control (QC) Samples, preferably are portions of one or more fuel or kerosine materials that are stable and representative of the samples of interest. These QC samples can be used to check the validity of the testing process as described in Section 18. If a suitable QC fuel is not available, obtain a stable QC concentrate, and dilute it with kerosine on the day ofthe QC check to the trace level required as described in 12.3. Use HDPE plastic bottles to contain concentrated organometallic solutions and for sodium analysis.
9. Hazards
9.1 Gases under high pressure and corrosive acid are used in this method. Wear appropriate personal protective equipment when working with nitric acid. Use only apparatus rated for handling the high gas pressures that occur in this test method.
10. Sampling and Test Specimens
10.1 Samples shall be taken in accordance with procedures described in Practice D4057. Suitable sample containers for aviation fuels are described in Practice D4306. Use HDPE plastic containers for sodium analysis.
10.2 Samples shall be thoroughly mixed in their containers immediately prior to testing.
10.3 If particulate matter is observed in the sample, filter it through a 0.8 µm or 1.0 µm (nylon, TFE-fluorocarbon, cellulose acetate/cellulose nitrate, or other compatible material) membrane filter into an acid-cleaned flask and retain the filtrate for analysis. Follow the same filtration procedure for the kerosine blank material used for the analysis of these samples.
