ASTM D5708 Method for Nickel, Vanadium, and Iron in Crude Oils and Residual Fuels
ASTM D5708 Standard Test Methods for Determination of Nickel, Vanadium, and Iron in Crude Oils and Residual Fuels by Inductively Coupled Plasma (ICP) Atomic Emission Spectrometry
5. Purity of Reagents
5.1 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.

5.2 When determining metals at concentrations less than 1 mg/kg, use ultra-pure reagents.

5.3 Purity of Water - Unless otherwise indicated, reference to water shall be understood to mean reagent water conforming to Type II of Specification D1193.

6. Sampling and Sample Handling
6.1 The objective of sampling is to obtain a sample for testing purposes that is representative of the entire quantity. Thus, take samples in accordance with the instructions in Practice D4057 or D4177. Do not fill the sample container more than two-thirds full.

6.2 Prior to weighing, stir the sample and manually shake the sample container. If the sample does not readily flow at room temperature, heat the sample in a drying oven at 80°C or at another safe temperature.