Initial Calibration Verification Standards

An initial calibration verification standard should be measured after calibration and before measuring any sample. A calibration verification standard is a standard solution or set of solutions used to check calibration standard levels. The concentration of the analyte should be near either the regulatory level of concern or approximately at the midpoint of the calibration range. These standards must be independent of the calibration solutions and be prepared from a stock solution with a different manufacturer or manufacturer lot identification than the calibration standards. An acceptance criterion is set, usually as a maximum allowable percentage variation (e.g., 5%, 10%). The calibration can be continually verified using either a calibration standard or the initial calibration verification standard. Acceptance criteria must be set and action taken when results fall outside the limits (i.e., stop the analysis, investigate, correct the problem and rerun samples run between the verification standards that were not limits). 

After initial calibration has been completed, it must be verified with a second source standard, which has been prepared from material coming from a different source (different manufacturer or lot number). This QC measure, called the second source confirmation, allows detecting errors in the initial calibration standard solution preparation and prevents a systematic error in compound quantitation. Only after this initial calibration verification (ICV) standard has also met its own acceptance criteria may the analyst start analyzing samples. 

A continuing calibration verification standard at a concentration that is close to the midrange of the calibration curve may be prepared either from the same stock solution as the initial calibration standard or from a standard of a different source. This CCV standard is analyzed at a certain frequency throughout sample analysis. 

Initial calibration Initial calibration verification with a second source standard Continuing calibration verification... 

IATA ICAP ICP ICP-AES ICP-MS ICV ID IDL IDW ISO International Air Transportation Association inductively coupled argon plasma inductively coupled plasma inductively coupled plasma-atomic emission spectrometry inductively coupled plasma-mass spectrometry initial calibration verification identification instrument detection limit investigation-derived waste International Standardization Organization... 

Dilution of stock solutions to prepare the series of working calibration standards that are injected into the gas chromatograph mass spectrometer (GC-MS) to calibrate the instrument for each of the 100 or more semivolatile organics. This series of standards should also contain at least one initial calibration verification... 

Running one or more reference standards in at least triplicate as initial calibration verification (ICVs) standards throughout the calibration range. ICVs should be prepared so that their concentrations fall to within the mid-calibration range. 

Initial Calibration Verification (ICV) Standard prepared in a similar manner as for the working calibration standards, however, at a different concentration than any of the working standards. Used to evaluate the precision and accuracy for an interpolation of the least squares regression of the calibration curve. This standard is run immediately after the calibration of the working standards. 

To achieve good precision and accuracy (see Chapter 2) in quantitating trace concentration levels of various metals of interest. Robinson has suggested that unknown samples, whose residual metal content is of interest to TEQA, the calibration standards, and the initial calibration verifications (ICVs) should be as similar as possible (113). To achieve this similarity the following considerations to both FIAA and GFAA become important ... 

Prepare an initial calibration verification (ICV) standard which should have its concentration approximately near the mid-range of the calibration. You should prepare 100 mL of the ICV. 

Initial calibration verification (IC V) A multielement standard of known concentrations prepared to verify instrument calibration. This solution must be an independent standard prepared near the midpoint of the... 

Method 200.8 specifies a variety of quality control standards. The first of these are the ICV and ICB (initial calibration verification and blank, respectively) samples. These must be run immediately after calibration and must be prepared from an alternative source to the calibration solutions. This test is designed to check the accuracy of the calibration. The CCV and CCB (continuing calibration verification and blank, respectively) samples are a similar check... 

Initial and continuing calibration verifications and acceptance limits Raw data for each sample (including reanalysis and second column confirmation), blanks, LCS/LCSD, MS/MSD, and calibration standards Sample preparation bench sheets Gel permeation chromatography clean-up logs / (Summary only) ... 

Reporting iimit (RL) verification standard The minimum concentration that can be reported with a specified degree of confidence. The RL can be no lower than the concentration of the lowest initial calibration standard. Laboratory control sample (LCS) A multielement standard of known concentrations that is carried through the entire sample preparation and analysis procedure. This solution is used to verify method performance in an ideal sample matrix. 

The ICP was a Perkin-Elmer 3000DV with an AS90 Autosampler, which has an instrument detection limit of about 1 ppb (for most elements) with a linear calibration up to 100 ppm (for most elements). Solid samples were prepared via microwave digestion in concentrated nitric and hydrochloric acids, then diluted to volume. The ICP was calibrated and verified with two independent, certified standard sets. Spikes and dilutions were done for each batch of samples to check for and/or mitigate any matrix effects. The ICP process ran a constant pump rate of 1.5 mL/min for all samples and standards during analysis. A 3 mL/min rinse and initial sample flush were used to switch between each sample and standard. The plasma was run at 1450 W with argon flow. Trace metal-grade (sub-ppb) acids and two independently NIST-certified calibration standard sets were used for calibration and method verification. 

After installation and qualification the instrument requires regular maintenance and calibration. The instrument should be maintained on a preventive maintenance plan and calibrated periodically according to a documented schedule. The schedule for preventive maintenance and performance verification/recalibration will depend on the instrument, its environment, and its function. The proposed U.S.P. chapter on NIR spectrophotometry [6] suggests that The purpose of instrument qualification is to assure that an instrument is suitable for its intended application and, when requalified periodically, it continues to function properly over extended time periods. Performance verification includes a validation based on a quality of fit to an initial scan or group of scans included in the instrument qualification.. . . With such testing, it is expected that reference standard spectra collected on a new or newly repaired, properly operating instrument should be identical to spectra of those standards collected over... 

Obtaining absolute quantity or concentration of an analyte typically requires constmction of a calibration plot based on analyses of standard samples with different concentrations. When the number of analyzed samples is small, or when the separation is not perfect, and it does not completely eliminate interference, it is advised to carry out quantification using multiple-standard addition. In the case of the standard addition method, the sample is analyzed first, followed by analyses of the same sample supplemented with the chemical standard at different concentrations. If the amounts of added standards are chosen correctly, one can estimate the amount of target analyte initially present in the sample. When carrying out quantification by multiple standard addition, one still has to make sure that the peaks of the supplemented samples are not overloaded. Verification of this point may require conducting additional preliminary tests. 

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