Industry Reference Material – 100 Silica
(IRM prepared according to ASTM D4678)
Approved by D11.20: June 17, 2015
IRM 100 is the designation for a special silica used for calibration and verification of test instruments according to the procedures as described in ASTM D1993/ISO 9277, ASTM D6845/ISO 5794-1, ISO 787-2, ISO 13320-1, ASTM D6739/ISO 787-9, ISO CD 19246, ISO 787-14, and ISO 3262-1. See page 3 of this Documentation Sheet for additional background on this IRM.
Properties for IRM 100
The testing conducted as part of the IRM 100 evaluation using ASTM D4678, generated accepted reference values, AR-values, for the given tests as defined below and 2 and 3 sigma limits on these values or on individual daily values as obtained by any laboratory using IRM 100. The 2 and 3 sigma limits apply to a single measurement of the listed test properties. Two times the 2 or 3 sigma limit equals the total 4 or 6 sigma range, respectively.
‘Accepted Reference Value’ or AR-value; this is the average, for the various tests listed below in Tables 1 and 2, obtained in an interlaboratory test program (ITP) for a large group of typical laboratories using samples taken from the lot. See page 3 for more details on the ITP.
‘Within Typical Laboratory’ 2 and 3 sigma value; (November-December 2014); this is the within laboratory +/- 2 and +/- 3 standard deviation (Sr) value (for single measurements) on the IRM 100 AR-values for the various tests, as obtained from the same group of typical ITP laboratories.
‘Between Typical Laboratory’ 2 and 3 sigma value (November-December 2014); this is the between laboratory +/- 2 and +/- 3 standard deviation (SR) value (for single measurements) on the IRM 100 AR-values for the various tests, as obtained from the same group of typical ITP laboratories.
Special consideration for bias: The ITP used data from five laboratories using their in-house instruments for the various tests. The statistical analysis of the data showed there was no statistically significant differences in the mean values between laboratories although a few values were declared to be outliers. Due to the small number of participating laboratories none were removed from the final data analysis. No more than one outlier was found for each data set and some data sets had no outliers. With only five laboratories with one instrument each participating is this ITP, there is insufficient data to make a conclusion on bias with any reasonable level of certainty. A determination of instrument linearity requires the use of several materials across the
range of instrument values. A laboratory that did not participate in the ITP may find that it cannot maintain control within the control limits due to factors unique to that laboratory causing bias in its values or increased variation. The laboratory should conduct an investigation to identify the causes of the bias and variation to eliminate them so that it is aligned with the ITP data. The five laboratories that participated in the ITP could use the data submitted for the ITP to establish the bias for each of their instrument and adjust the AR value and control limits accordingly to maintain the instrument in control. However, that does not address the need to eliminate the bias to bring the instrument into alignment with the ITP. Participation in a multi-laboratory precision study may help to identify the unique sources of bias and variation.
Background and Interlaboratory Test Program Details:
IRM 100 Silica
Background - Industry Reference Materials (IRMs), used for a number of test methods under the jurisdiction of ASTM Committee D11, are prepared according to D4678, "Preparation, Testing, Acceptance and Documentation for Industry Reference Materials (IRM)". Testing of the IRM lot produces four types of ‘lot properties’ for each type of test conducted as part of the IRM evaluation. This lot is a typical NB or non-blended IRM that requires an evaluation for lot uniformity or homogeneity as well as accepted reference or AR-value using D4678.
Evaluation of the IRM Lot - This first lot of silica IRM was produced by Evonik Industries, Germany, October 29, 2014 using their SIPERNAT® 160 lot no 194102939 material and packaged into 10 kg paper bags. Following testing and evaluation for uniformity by Evonik, an ITP was organized in November 2014 to determine lot uniformity or homogeneity.
Interlaboratory Test Program (ITP) - Five laboratories using their in-house instruments each tested IRM 100 for the eight designated test properties using the appropriate test methods. Each property was determined by one technician twice on each of three different days for a total of six measurements for each test method. The DOA results from one laboratory were not used for this ITP due to instrument failure during the testing period. The ITP testing was conducted in November – December 2014. The data was analyzed per D4678, annex A4.
Using IRM 100 – For the test methods listed in Table 1 it is strongly recommended that laboratories determine if they are operating in an “in control” manner, by the use of the +/- 2 sigma within-laboratory limits. Despite rigorous analysis of the ITP data for the AR-value(s) and associated standard deviation(s), the group of laboratories in this (and any) ITP do not represent a typical “in statistical control system” to which the usual 6 sigma limits are applied. All the assignable causes of variation that are typically eliminated to attain ‘statistical control’ have not and cannot be, eliminated for the AR testing.
The values listed in Table 2 are informational only and are not intended for use to calibrate the various instruments. However, these values can be used to validate the instruments for proper operation.
If the IRM 100 material is used for the validation of BET instruments, control charts should be prepared and checked regularly (quarterly or annually) using special traceable BET surface area standard materials. The target value in line with the given range should be updated, preferably annually, and at the latest after two years to incorporate the expected drift of the mean value.
Regarding the loss on drying test, the stated AR value/range is valid for fresh samples in sealed packaging. After opening the moisture level may vary depending on the storage conditions.
Loss on ignition is calculated based on dry substance so the accuracy of the AR value/range correlates with the accuracy of the measurement of loss on drying.
Supplementary Information – Since precipitated silica is porous and has a high specific surface area, there is the danger that it may absorb vapors or gases, thereby having a negative impact on the properties of the product. For this reason, always keep the product away from sources of contamination. As regards storage temperatures, there are no particular limits from a technical safety aspect. In general, temperatures up to 50°C have proved to be uncritical. Low temperatures such as severe frost also have no adverse effect on the silica. This IRM is expected to remain stable for a period of a minimum of 3 years. A full ‘Research Report’ documenting all the analysis for IRM 100 will be on file at ASTM headquarters (expected after June 2015), 100 Barr Harbor Dr., W. Conshohocken, PA 19428, USA; Phone 610-832-9500, Fax 610-832-9555.
 The current version of this document is available from Laboratory Standards and Technologies, Inc., 227 Somerset Street, Borger, TX, 79007, www.carbonstandard.com.