ASTM D3624-85a (R2015) pdf free.Standard Test Method for Low Concentrations of Mercury in Paint by Atomic Absorption Spectroscopy.
1.1 Assemble the various components, as illustrated in Fig.1 if an atomic absorption spectrophotometer is used, or prepare the instrument for operation if a commercial mercury analyzer is being used.NoTE 2- Be sure that all glassware has been thoroughly cleaned and rinsed with reagent water prior to use.
1.2 Operational instructions for atomic absorption spectrophotometers and commercial mercury analyzers vary with different models. Consult the manufacturer s literature for establishing optimum conditions for the specific instrument used.
1.3 With the apparatus empty, stabilize the recorder base line while maintaining a flowrate of 250 mL of nitrogen per minute.
1.4 Transfer 0, 5, 10, 15, and 20-mL aliquots of the working mercury standard (containing 0 to 2 ug of mercury) to a series of 250-mL gas washing bottles. Add enough water to each bottle to make a total volume of 100 mL. Add 5 mL of H2SO4 and 3 mL of HNO3 to each bottle and mix thoroughly. Make
dropwise additions of 0.1 N KMnO4 solution to each bottle in urn until a pink color persists for at least 30s (1 mL is usually sufficient). Add exactly 1 mL of NH2OH.HCl solution dropwise to each bottle and swirl until the pink color is discharged.
2.1 If the sample is a liquid coating， mix it until homogeneous, preferably on a mechanical paint shaker. Prepare at least two replicate specimens by weighing to 0.1 mg by difference from a dropping bottle or syringe, 100 to 200 mg of the mixed paint into the PTFE insert of the acid decomposition
vessel. Place the insert in an oven set at 60°C (140°F) for 1 h to remove all volatiles.
2.1.1 Caution- -If the solvent present in a sample is not removed prior to the digestion step as recommended, potentially dangerous pressures may result when the vessel is heated at 140°C.
2.2 If the sample consists of dried film, coarsely grind it and weigh 50 to 100 mg by difference from a weighing bottle into the digestion vessel.
NoTE 5- Recover dried paint films from previously coated substrates (being careful not to remove any underlying material from the substrate) or prepare in the laboratory from liquid samples. For the laboratory preparation, flow some of the well-mixed sample onto a clean glass plate.The use of a paint draw-down bar is recommended to obtain a uniform wet film thickness not exceeding 2 mils (50 um). Allow the film to dry in an oven at 60°C for a minimum of 1 Scrape the dried film off the glass plate, preferably with a single-edge razor blade.
2.3 Pipet 5 mL of concentrated H2SO4 and 3 mL of concentrated HNO3 into the decomposition vessel insert, using a fume hood for the operation. Seal the vessel tightly and place in the circulating oven at 140°C for 1/2 h. Remove the vessel from the oven and allow it to cool slowly to room temperature.ASTM D3624 pdf download.