Contents

Inorganic Quality Control

Effective Date: 07/2008
Point of Contact: Quality Engineer for Regulatory Programs

Inorganic preparative techniques and inorganic analytical techniques are described below.

Inorganic Preparative Techniques

Preparative techniques are those operations used to prepare a sample for analysis. Preparative techniques may include digestion, dissolution, extraction, and/or leaching of a sample material. Separation and/or isolation techniques may also be considered preparative if performed to facilitate the analysis. Simple dilution is not considered a preparative technique. The Inorganic Preparative Quality Control Requirements exhibit provides the frequency and acceptance criteria requirements for inorganic preparative quality control (QC).

The Hanford Analytical Services Quality Assurance Requirements Documents (HASQARD) considers the use of either Contract Laboratory Program protocols or associated EPA SW-846 protocols to be acceptable.

Batch

A batch is a group of samples, of similar matrix type, processed through the preparative techniques at the same time. For each batch, a set of preparative QC shall be processed. A batch shall not exceed 20 samples, excluding the preparative QC samples (e.g., preparation blank [PB], laboratory control sample [LCS], blank spike [BS], matrix spike [MS], duplicate). If the client does not specify project-specific QC, the laboratory may combine up to 20 samples of similar matrix type for preparation with only one set of preparative QC. In the case of process testing or unique client requirements, QC elements such as a sample duplicate (or matrix spike duplicate [MSD]) and MS may be performed for every 20 client-specific samples received. However, the PB and LCS or BS requirement would apply to each batch of samples prepared at one time. Unique client requirements shall be documented and agreed upon by the project and the client before work begins.

Preparation Blank

The PB is used to monitor contamination resulting from the sample preparation process. The PB is generally distilled or deionized water that is subjected to the same processing as the samples, including all reagent additions. The PB volume or weight shall be approximately equal to the sample volume or weight being processed. If addition of even a small quantity of distilled or deionized water is not recommended, only the solvents or reagents used to prepare the sample should be added to the blank. A matrix more closely related to the actual samples processed may be used provided the matrix is free of contamination from analytes of interest. Interferences produced by the blank matrix should be similar to that of the sample. PB acceptability shall be demonstrated by the concentration of the target analytes in the blank meeting one of the following requirements:

Laboratory Control Sample or Blank Spike

The LCS or BS is used to monitor the effectiveness of the sample preparation process. A LCS is a material similar in nature to the sample being processed, containing the analyte(s) of interest (e.g., standard reference material such as NIST or independent standard material similar in matrix to that of samples). The BS is distilled or deionized water spiked with the analyte(s) of interest (normally similar to MS material). A BS is normally used when an appropriate LCS is unavailable.

LCS or BS control is demonstrated by target analytes being within established control limits. Control limits are established by one of the following:

For CN and Hg if the ICV is prepared with the samples and similar in matrix, then the ICV can be also used as the LCS.

Matrix Spike

The MS is used to monitor method performance in a specific matrix. A MS is a sample that has been spiked with the analyte(s) of interest and processed similarly to the original sample.

Spiking is typically performed at a level that equals one of the following:

If the concentration of the analyte in the original, intact sample is greater than 0.1%, no MS is required unless specified otherwise in client work-authorizing document. Sample concentrations exceeding 5 times the spike concentration render recovery data meaningless for assessing data usability.

If the MS recovery is outside established limits, the analyst shall evaluate the MS recovery information against client data quality requirements. The analyst shall discuss any limitations on the data in the report to the client.

MS control is demonstrated when target analytes are within established control limits. Control limits are established by one of the following:

Sample Duplicate or Matrix Spike Duplicate

Duplicates are used to assess the precision of the preparation process. Specifically, the duplicate indicates matrix homogeneity. Duplicates are two aliquots of the same sample that are taken through the entire sample preparation and analytical process. MSDs are two spiked aliquots of the same sample that are taken through the entire sample preparation and analytical process. Precision is estimated by calculating the relative percent difference (RPD) of the duplicate results.

Inorganic analyses typically employ a sample and duplicate. Inorganic duplicate RPD criteria are normally 20%; these criteria shall only be applied to analyte concentrations greater than 10 times the instrument detection limit (IDL).

Inorganic Analytical Techniques

Analytical techniques are considered those operations that permit the measurement of a parameter of interest. Analysis can be considered the measurement of some property for which there is an instrument response that can be related to the concentration or amount of the substance of interest in a sample or in some material prepared from the sample. The QC requirements presented below are designed to verify and document proper instrument operation and to give the analyst information regarding the precision, accuracy, and sensitivity of the analytical process. The Inorganic Analytical Quality Control Requirements exhibit provides frequency and acceptance criteria requirements of analytical QC.

The Hanford Analytical Services Quality Assurance Requirements Documents (HASQARD) considers the use of either Contract Laboratory Program protocols or associated EPA SW-846 protocols to be acceptable.

Analytical Run or Sequence

An analytical run or sequence is defined as a group of samples analyzed together that may include one or more batches. Analytical QC is used to define the boundary of each analytical run. The analytical run typically starts with either calibration or confirmation that the calibration is still valid using a calibration verification. For most inorganic analyses, the run ends with a continuing calibration performance. The order in which samples and QC are analyzed shall be traceable to the analytical sequence.

Initial Calibration Verification

The initial calibration verification (ICV) is a standard used to confirm the acceptability of the calibration. Acceptable performance of the ICV demonstrates that both the standards used and the instrument are functioning properly. The ICV is prepared from a lot other than that used to prepare the calibration standards, when available. Analytical measurement systems that are calibrated frequently and for which calibration standards are routinely prepared normally follow calibration with an ICV.

Failure of the ICV indicates instrument and/or standard problems that shall be evaluated and corrected before any samples are analyzed.

Continuing Calibration Verification

The CCV is used to monitor instrument stability over time for the analyses of interest. Acceptable performance indicates that the measurement system is still in control. The CCV may be prepared from any reliable source and need not be nationally or internationally traceable; however, the CCV may be the same as the ICV.

Each inorganic analytical system shall include periodic checks on the stability of the instrument for the analyses of interest. These checks shall be performed every 10 samples and at the end of the analytical run. Failure indicates that the analytical system has drifted out of control and requires corrective action for the analytes of interest. All samples analyzed after the last acceptable CCV shall be reanalyzed; reanalysis applies to specific analyte failure. In limited cases, isolated analyte failures may be tolerated if sample results still meet the client data quality requirements. Reporting results in such cases requires justification in the report to the client.

Initial and Continuing Calibration Blanks

An initial calibration blank (ICB) and a continuing calibration blank (CCB) monitor for contamination, cross contamination, and instrument drift. The ICB and CCB are reagent blanks, prepared similarly to the standards but not subjected to preliminary sample preparation except when the preparation is an integral part of the analysis. In these cases, the PB can be considered the equivalent of the ICB or CCB. The acceptance criteria for an ICB and a CCB are that they are below the EQL for each analyte of interest. When an analyte exceeds these criteria, the analysis shall be investigated for potential impact. Samples with concentrations exceeding the blank contamination level by a factor of 20 or more can normally be reported unless client requirements dictate otherwise. In limited cases, analyte failures may be tolerated if sample results still meet the client data quality requirements. In all other cases, the client shall document the requirements.

Internal Standards

An internal standard is an analyte that is similar to the analyte(s) of interest in chemical composition and behavior but which is not normally expected to be found in the sample. Internal standards are added after sample preparation and before analysis. Selecting appropriate internal standards shall be method- and compound-list specific, because all results are normalized based on internal standard performance. The technical procedures shall specify acceptance criteria, unless otherwise specified in this QA Plan. Sample results are normalized against the internal standards.

Low-Level Standard

The low-level standard (LLS) is used to monitor instrument performance in the region at or just above the EQL and is routinely applied to inorganic systems to monitor sensitivity in the EQL region.

For inductively coupled plasma spectrometer (ICP) systems, the LLS should be prepared at approximately 2 times the EQL. The majority of other inorganic techniques employ a LLS that is equivalent or close to but above the EQL. When the LLS concentration is included in the instrument calibration, a separate LLS is not required.

Interference Check Standards

Interference check standards are typically applied in ICP spectrometry systems. The interference check normally consists of two standards. The first standard contains known concentrations of the interfering elements that will provide an adequate test of interelement correction factors. The second standard contains both the major interferents and the majority of other analytes tested. The major interferents are spiked into the standards at significant concentrations to produce an interference effect. All other analytes are spiked at relatively low levels. Data from both standards, when corrected, should recover between 80% and 120% for all analytes tested or the interelement correction is inadequate. The standard that contains only the primary interferents of concern should produce no analyte concentrations in excess of the EQL. Instruments capable of showing negative results do not require the second standard that contains both interferents and additional analytes tested.

Post-Digestion Spike

For inorganic compounds, a post-digestion spike is a spike added to the sample after preliminary preparation, usually just before analysis. The post-digestion spike technique is normally used when an MS fails. Therefore, the sample spiked would be that sample on which an MS was originally performed. The post-digestion spike provides the analyst with information regarding matrix-related interferences on the analytical system that may still be present in the sample following digestion. This technique is typically used for ICP spectrometry analysis but is appropriate to other techniques as well.

Serial Dilution

Serial dilution is a 5-fold dilution of a sample followed by analysis. This technique is an indicator of potential matrix-related interferences associated with analysis. Serial dilution is only performed when a sufficient number of analyte concentrations exceeds 50 times the IDL. Therefore, the sample concentration should be a minimum of 10 times the EQL before performing the 1-to-5 dilution. A percent difference of 10% or less for the original and diluted results indicates acceptable performance. If the sample analyte concentration is less than 50 times the IDL, an analytical spike (AS) should be performed instead of a serial dilution

Method of Standard Additions

The Method of Standard Additions (MSA) involves adding known amounts of a blank and standard to aliquots of the sample. The MSA is meant to compensate for a sample effect that enhances or depresses the analyte signal. The MSA consists of a blank and at least three standards to which aliquots of the sample are added. The standards used should be approximately 50%, 100%, and 150% of the expected sample concentration.

When the MSA is employed, instrument calibration and periodic calibration verification using standards and blanks is not required. The MSA is performed on all associated matrix QC when employed on the sample (i.e., when MSA is performed on the sample, it shall also be applied to that samples duplicate and sample spike when such QC is applied).