ASTM D7303-17 PDF

1.1 This test method covers the determination of a number of metals such as aluminum, antimony, barium, calcium, iron, lithium, magnesium, molybdenum, phosphorus, silicon, sodium, sulfur, and zinc in unused lubricating greases by inductively coupled plasma atomic emission spectrometry (ICP-AES) technique.

1.1.1 The range of applicability for this test method, based on the interlaboratory study conducted in 2005,2 is aluminum (10 to 600), antimony (10 to 2300), barium (50 to 800), calcium (20 to 50 000), iron (10 to 360), lithium (300 to 3200), magnesium (30 to 10 000), molybdenum (50 to 22 000), phosphorus (50 to 2000), silicon (10 to 15 000), sodium (30 to 1500), sulfur (1600 to 28 000), and zinc (300 to 2200), all in mg/kg. Lower levels of elements may be determined by using larger sample weights, and higher levels of elements may be determined by using smaller amounts of sample or by using a larger dilution factor after sample dissolution. However, the test precision in such cases has not been determined, and may be different than the ones given in Table 1.

Note 1: X is the mean concentration in mg/kg.

Element

Range,
mg/kg

Repeatability

Reproducibility

Aluminum

10-600

0.2163 X0.9

6.8156 X0.9

Antimony

10-2300

0.3051 X0.8191

4.6809 X0.8191

Barium

50-800

0.3165 X0.7528

2.9503 X0.7528

Calcium

20-50 000

2.2853 X0.7067

3.0571 X0.7067

Iron

10-360

0.8808 X0.7475

2.5737 X0.7475

Lithium

300-3200

0.0720 X1.0352

0.1476 X1.0352

Magnesium

30-10 000

0.6620 X0.6813

2.6155 X0.6813

Molybdenum

50-22 000

0.1731 X0.9474

0.4717 X0.9474

Phosphorus

50-2000

1.2465 X0.6740

4.0758 X0.6740

Silicon

10-15 000

1.3859 X0.9935

4.8099 X0.9935

Sodium

30-1500

6.5760 X0.5

11.571 X0.5

Sulfur

1600-28 000

1.0507 X0.8588

1.5743 X0.8588

Zinc

300-2200

0.1904 X0.8607

0.5912 X0.8607

1.1.2 It may also be possible to determine additional metals such as bismuth, boron, cadmium, chromium, copper, lead, manganese, potassium, titanium, etc. by this technique. However, not enough data is available to specify the precision for these latter determinations. These metals may originate into greases through contamination or as additive elements.

1.1.3 During sample preparation, the grease samples are decomposed with a variety of acid mixture(s). It is beyond the scope of this test method to specify appropriate acid mixtures for all possible combination of metals present in the sample. But if the ash dissolution results in any visible insoluble material, the test method may not be applicable for the type of grease being analyzed, assuming the insoluble material contains some of the analytes of interest.