ASTM D4951 for additive elements in lubricating oils by ICP-AES
ASTM D4951 standard test method for determination of additive elements in lubricating oils by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES)
APPENDIXES
(Nonmandatory Information)
X1. GENERIC QUALITY CONTROL STATEMENT FOR D02 TEST METHODS
X1.1 Confirm the performance of the instrument or the test procedure by analyzing a quality control (QC) sample that is, if possible, representative of the samples typically analyzed.

X1.2 Prior to monitoring the measurement process, the user of the method needs to determine the average value and control limits of the QC sample (see Practice D 6299 and MNL78).

X1.3 Record the QC results and analyze by control charts or other statistically equivalent techniques to ascertain the statistical control status of the total test process (see Practice D6299 and MNL78). Any out-of-control data should trigger investigation for root cause(s). The results of this investigation may, but not necessarily, result in instrument recalibration.

X1.4 In the absence of explicit requirements given in the test method, the frequency of QC testing is dependent on the criticality of the quality being measured, the demonstrated stability of the testing process, and customer requirements. Generally, a QC sample should be analyzed each testing day with routine samples. The QC frequency should be increased if a large number of samples is routinely analyzed. However, when it is demonstrated that the testing is under statistical control, the QC testing frequency may be reduced. The QC sample precision should be periodically checked against the ASTM method precision to ensure data quality.

X1.5 It is recommended that, if possible, the type of QC sample that is regularly tested be representative of the sample routinely analyzed. An ample supply of QC sample material should be available for the intended period of use, and must be homogeneous and stable under the anticipated storage conditions.

X1.6 Refer to relevant documents (see Practice D6299 and MNL7) for further guidance on QC and control charting techniques.

X2. AIDS TO THE ANALYST
X2.1 Check the temperature control of the ICP and ensure stable environmental conditions. This can include temperature control of the spray chamber.

X2.2 Employ adequate mixing and sampling procedures. Ultrasonic homogenizers and vortex mixers are recommended.

X2.3 Use the analytical wavelengths and background correction option specified in the test method. When there is a choice of analytical wavelengths, choose sensitive lines. Ensure that the selected lines are not subject to spectral interferences.

X2.4 When spectral interferences cannot be avoided, determine and implement accurate interference correction factors.

X2.5 When sulfur is to be determined, be apprised that many commercially-available standards contain non-certified levels of sulfur. Separate sulfur standards can be advantageous.

X2.6 When preparing multi-element standards, ensure that the various reagents are mutually soluble.

X2.7 Before use, check the accuracy of element concentrations of commercially-obtained standards. Either compare

X2.8 Ensure that all glassware, and so forth, that contacts samples and standards does not contaminate.

X2.9 Select solvents and other reagents that do not contain significant levels of the analytes. Wavelength scanning can indicate contaminated reagents.

X2.10 By experiment, determine the frequency of standards preparation. Then, prepare fresh, as needed.

X2.11 Periodically, as needed, determine the linearity of the calibration curves. Perform quantitative analyses with linear curves only.

X2.12 Inspect the torch for cracks. Discard defective torches.

X2.13 Use clean torches that do not have carbon accumulation.

X2.14 After initially igniting the plasma, allow the instrument to warm up a minimum of 30 min.

X2.15 Inspect the peristaltic pump tubing daily, and replace deteriorating tubing. Daily replacement is recommended.

X2.16 Prepare and analyze reagent blanks. When blank values are significant, correct for the blank or select alternative reagents that give insignificant blank values.

X2.17 To minimize memory effects, allow sufficient solvent rinse time (minimally, 60 s) between determinations.

X2.18 Report results using the number of significant figures specified in the test method.

X2.19 Dilute the standard oils and sample oils by the same factor. This factor shall be in the range specified by the test method.

X2.20 Implement internal standardization as specified by the test method.

X2.21 When carbon build-up in the torch is problematic, adjust experimental conditions to eliminate the problem. Such adjustments can include (1) reducing the sample uptake rate, (2) increasing the intermediate argon gas flow rate, (3) use a jacketed, chilled spray chamber, (4) lowering the torch, relative to the RF load coil.

SUMMARY OF CHANGES
Subcommittee D02.03 has identified the location of selected changes to this standard since the last issue (D4951-00) that may impact the use of this standard.
(1) Updated the requirements for the specimen solution containers in 6.5 to account for container sizes that fall out of the range previously specified, due to instrument or auto-sampler requirements.

(2) Updated the requirements for the base oil specified in 7.2.

(3) Updated the requirements in 11.2.1 and 11.2.2.1 to provide flexibility in the amount of oil or additive package that needs to be weighed for the analysis.

(4) Corrected errors in Table 4 concerning the repeatability value cited for P at 0.1 mass %, as well as the reproducibility value cited for P at 0.05 mass %.