Interpreting the Quality Control Report

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Interpreting Your
Lab Report
&
Quality Control Results
Your report contains all sample info
from sampling thru data reporting
It will contain up to 10 sections, if you
have requested that the Quality
Control Results be included in your
report package.
The 10 sections are as follows:

Cover Letter (General Information)

Report Contents (Content Index)

Definitions (Abbreviations you may see in the report)

Case Narrative (Important Information about the report )

Laboratory Results (Results for each sample in the Work Order)

Sample Summary (Lab and Client IDs, Matrix, Collection Dates)

Dates Report (Listing of important sample dates and times)

Quality Control Results (Listing of associated Quality Control
Indicators)

Receiving Check List (Sample acceptance criteria and Special
Notes)

Chain of Custody (Chain of Custody that accompanied the
samples)
The first 3 Pages
give some very
useful info
Definitions
(Abbreviations you may see in the report)
The 4th page the is a must read!
Here important abnormalities &
report revisions are Documented
Case Narrative
(Important
Information about the
report )
Locations and
Accreditations
(Our contact info )
(Our accreditation info )
The next pages contain the lab results for each sample
tested.
Reporting Limit
Smallest
Case NarrativeMeasurable Level
(Important Information
Method
about the report )
Used
Locations and Accreditations
(Our
contact info )
Analyte
(Our
accreditation info )
Measured
Data flags for
QC alerts
Result
Dilution Factor
Reporting Limits (RL)



The reporting limit (RL) is the smallest
accurately measureable number for the sample
as tested.
If we have to use a smaller sample size or dilute
the sample during the testing phase the RL will
be adjusted.
The RL is determined for each sample result by
multiplying the Practical Quantitation Limit (PQL)
by any Prep Factor (PF) or Dilution Factor (DF)
used to produce that result.
Following the Lab Results are a summaries of the
samples and the processing dates
Sample Summary
(Lab and Client IDs, Matrix, Collection Dates)
Dates Report
(Listing of important sample
dates and times)
Next we have the Quality Control Report – Each test is listed with its QC
Next – The Receiving Check List
When the samples arrive at the lab, this is
where any excursions from Teklab’s Sample
Acceptance Policy are recorded.
The Lab Report Ends with a Copy
of your Chain of Custody



The chain of custody is an important piece
in making your report legally defensible.
This copy also contains lab notes and
documents some conversations between
you and the lab.
You will also see the lab numbers added
next to each of your Sample ID’s
Quality Control Results



The following presentation will help you better
understand the Quality Control Results portion of
the report.
The Laboratory Results portion of the report and
the Quality Control Results work together to help
assess the data.
The column headings will be printed in light blue
in the explanations. Quality Control Indicators will
be printed in bold dark blue.
There are 3 basic things to look for
when reviewing the QC report.
1.
Contamination
2.
Accuracy
3.
Precision
Data Qualifier Codes are used in
the Qual column as Alerts
(commonly known as flagging the data)
B – Contamination in associated method blank
 S – Recoveries that are not within QC limits
 R – RPD of duplicate analysis exceeds QC limit
 J – Result is above the method detection limit,
but below the reporting limit
 E – Result is above the calibration range
 H – Sample analysis time exceeded holding
time listed for test within its method

Samples are Processed in a Batch



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Batch: Environmental samples that are prepared and/or
analyzed together with the same process and personnel,
using the same lot(s) of reagents.1
A preparation batch is composed of 1 to 20 environmental samples of the same
quality systems matrix, meeting the above mentioned criteria and processed within
24 hr from the start of the 1st to the start of the last sample.1
An analytical batch is composed of prepared environmental samples which are
analyzed together as a group. They can include prepared samples from various
matrices and can exceed 20 samples.1
As you review your data in the Laboratory Results
section of the report,
notice the Batch number listed for each analyte in the
far right column. Use this number to find the associated
Quality Control Indicators in the Quality Control Results
section of the report.
Notice the Batch Number in the
Example.


The Batch Number is located right below the Test Method on the QC
Report
Some tests and/or matrices do not have a preparation step before analysis and
do not require a preparation batch. These tests have a “R” at the beginning of
their batch number.
Method Blank – MBLK


MBLK – A clean matrix processed and analyzed with
the samples to check for batch contamination.
TNI 2009 definition - “Method Blank: A sample of a matrix similar to the
batch of associated samples (when available) that is free from the analytes
of interest and is processed simultaneously with and under the same
conditions as samples through all steps of the analytical procedure, and in
which no target analytes or interference are present at concentrations that
impact the analytical results for sample analysis.”
(TNI 2009)
SampType: MBLK



A analyte with a MBLK Result below the reporting limit (RL) indicates a
batch free from contamination. If the Result was above the RL, there would
be a B in the Qual column here and on the in the Laboratory Results section
of the report.
If the MBLK is above the reporting limit, the samples results that are below
the reporting limit (RL) are reportable.
If the MBLK is above the reporting limit, the sample results that are over 10
times the reporting limit (RL) are reportable, with comment.
Quality Control Indicators are Reported in the Quality
Control Results Section of the Report for each Batch
(any or all of the following may appear based on the method and the amount of sample supplied to the lab)

Method Blank (MBLK)

Laboratory Control Spike (LCS)

Laboratory Control Spike (LCSDUP)
Checks Batch for Contamination
Checks Batch for Accuracy
by Measuring Recovery
Checks for Accuracy and Checks for Reproducibility in place of MSD or DUP
Checks Accuracy by Measuring Recovery
in the Sample Matrix

Matrix Spike (MS)

Matrix Spike Duplicate (MSD)

Duplicate (DUP)

Surrogate (SUR)
Checks Accuracy &
Reproducibility in Sample Matrix
Checks for Sample Result Reproducibility
Checks Accuracy by Measuring Recovery
in Organic Methods.
Percent Recovery (%REC )
Measures the accuracy of the recovery for the
LCS, LCSDUP, MS, & SURR
 Accuracy – “The degree of agreement between an

observed value and an accepted reference value”. (TNI 2009)
This degree of agreement is measured in %REC.
The lab calculates the %REC as follows:
 Percent Recovery for LCS
 %REC = (LCS / Spike) x 100

Percent Recovery for MS & MSD
 %REC = ((MS – Sample / Spike) ) x 100
Laboratory Control Sample – LCS


LCS – A clean matrix spiked with the analyte(s) of interest
and processed and analyzed with the samples to determine
whether the measurement system is performing as
expected. Determines whether the laboratory is capable of
making accurate and unbiased measurements.
TNI 2009 definition – Laboratory Control Sample (however named, such as
laboratory fortified blank, spiked blank, or QC check sample): A sample
matrix free from the analytes of interest, spiked with analytes and taken
through all sample preparation and analytical steps of the procedure unless
otherwise noted in a reference method. It is generally used to establish intralaboratory or analyst specific precision and bias or to assess the performance
of all or a portion of the measurement system. (TNI 2009)
SampType: LCS

The LCS in the above example had a Spike of 0.050 mg/L and a
Result of 0.047. The %REC of 94.7 is within the LowLimit 85% and
HighLimit 115%.

The data is within the control limits; therefore, the sample results
that were associated with this batch are reportable.

You can find the associated sample Result in the Laboratory Results
section of the report by using the Batch number R164760.
LCS not within the Control Limits?

The test must be redone - all samples must be
reanalyzed with a new MBLK and LCS.

Exceptions:

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If the LCS recovered above the upper control limit, samples
that were below the RL can be reported.
If the LCS for the test has 11 or more analytes the Allowable
Marginal Exceedance rule may apply. (more on this later)
If there is insufficient sample for re-analysis, the
data must be reported with comments or more
sample must be collected upon client request.
SampType: LCS


The LCS in the above example had a Spike of 0.025 mg/L and a
Result of <0.005. The %REC of 0 is not within the LowLimit 90%
and HighLimit 110%. This QC failure is indicated with a Qual of S.
No data should be reported in the Laboratory Results section of the
report with a Batch number of 78992.
In the above example we see the LCS from the reanalysis of the
failed batch. The %REC of 104.0 is within the LowLimit 90% and
HighLimit 110%. All of the data for this analyte reported in the
Laboratory Results section should have a Batch number of 79059.
Allowable Marginal Exceedances in the LCS?

If a large number of analytes are in the LCS, it becomes
statistically likely that a few will be outside of the control limits.
(TNI 2009)
The number of allowable marginal exceedances is as follows:
Number of Analytes in LCS
Number Allowed as Marginal Exceedances
> 90
5
71 – 90
4
51 – 70
3
31 – 50
2
11 – 30
1
< 11
0
If the same analyte exceeds the LCS control limit consecutively, it is an indication of a
systemic problem. The source of the error shall be located and corrective action taken.

Allowable Marginal Exceedances will be flagged with an S in the Qual
column and will have a comment in the Lab Results section of the report
that looks like this:

Allowable Marginal Exceedances in the LCS verified per 2009 TNI Standard (Volume 1,
Module 4, section 1.7.4.2).
Matrix Spike – MS


MS – A sample spiked with the analyte(s) of interest and
processed and analyzed with the samples to determine
whether the measurement system is performing as expected in
that particular sample matrix.
TNI 2009 definition – A sample prepared, taken through all sample
preparation and analytical steps of the procedure unless otherwise noted in
a referenced method, by adding a known amount of target analyte to a
specified amount of sample for which an independent test result of target
analyte concentration is available. Matrix spikes are used, for example, to
determine the effect of the matrix on a method’s recovery efficiency. (TNI 2009)
When a MS or MSD does not recover within the
Control Limits (and the LCS did) we know
there is a matrix or composition problem.

Matrix Spikes (MS & MSD) are intended to
let the client know how well the test
method is working in their particular
matrix.
SampType: MS

The MS in the above example had a Spike of 0.025 mg/L and a Result of
0.022. The %REC of 88.0 is not within the LowLimit 90% and HighLimit 110%.

Notice the Qual of S to alert us that there is a matrix interference that caused a
the spike not to recover within the limits.

By looking for the Batch number of 79059, we find the associated sample
Result in the Laboratory Results section of the report . Notice the S to alert you
about the recovery problem and the comment with the results to explain.
Relative Percent Difference (RPD)
Measures the Precision or Reproducibility between the
MS & MSD, the Sample & DUP, or the LCS & LCSDUP

Precision – “The degree to which a set of
observations under similar conditions, conform
to themselves”. (TNI 2009)
This degree is express as RPD.
The lab calculates the RPD as follows:

RPD for LCS and LCSDUP or Sample and DUP

RPD = | ((A – B) / ((A + B) / 2)) X 100 |


Where: A = first result
B = duplicate result
Notice the absolute value signs in the equation. The
RPD will always be a positive number.
Matrix Spike Duplicate – MSD
 MSD
– An additional matrix spiked
sample used to determine both
precision and accuracy of the test
method in that particular matrix.

TNI 2009 definition – A replicate matrix
prepared in the laboratory and analyzed to
obtain a measure of precision. (TNI 2009)
SampType: MSD

The MSD in the above example is the duplicate analysis of the MS that we just
viewed. Notice the Result of the MS is listed under the RPD Ref Val.

The MSD has a Spike of 0.025 mg/L and a Result of 0.024. The %REC of 97.0
is within the LowLimit 90% and HighLimit 110%; therefore, no S Qualifier.


Notice the RPD Limit of 15 listed in the top line. The %RPD must be below 15
to pass the duplicate test. The %RPD of 10.32 falls below the limit; therefore,
the duplicate analysis passes. If the %RPD had been above 15 there would be
a R in the Qual column and a comment with the Laboratory Results.
In this case we have the MS slightly below the control limit, the MSD within
the limit and the %RPD passing.
DUP & LCSDUP


DUP – a duplicate preparation and analysis of
the sample. Used to determine reproducibility of
the test when the method does not require an
matrix spiking.
LCSDUP – a duplicate preparation and analysis
of the LCS. Used to determine reproducibility of
the test when there is insufficient sample
provided to perform an MSD or DUP.
Surrogates - Surr
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

Surr - Used in organic analysis to evaluate the method in each
sample matrix.
Surrogates spiked into all of the QC and samples to monitor the
efficiency of the test method. They mimic the analytes of interest
and are compounds unlikely to be found in environmental samples.
Notice that the Control Limits for the surrogate recovery are listed
under the RL column heading. Surrogates that are not within the
limits will have a S flag in the Qual column and a comment in with
the lab results.
3 Basic Evaluations of the QC Report
Contamination, Accuracy & Precision

The batch number is your reference key to the
associated QC in the QC Report.

The MBLK checks for contamination ( B flags )

The LCS & LCSD check for Accuracy of the Test Method
( S flags)

The MS & SURR check for Accuracy of the Test Method
in the sample matrix ( S flags )

The MSD & DUP check for Precision or Reproducibility
of the sample matrix ( R flags )

The LCSDUP checks for Precision of the Method
( R flags )
We work very hard to give you everything
you need to understand your Lab Report –
If you need further assistance, your project
manager will be happy to assist you!
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