Library Reference 3.3

 Environment Canada Phosphorus and Mercury Proficiency Samples   Onondaga Lake  Ambient Monitoring Program 2011 

                               

  

Background Environment  Canada  provides  accredited  proficiency  testing  (PT)  studies  for  a wide  range  of inorganic  constituents  in  water.  The  purpose  of  the  program  is  to  identify  sources  of measurement uncertainties and variation among analytical results, and to provide  information on overall data quality and reliability. Laboratories from the U.S., Canada, and around the world participate  in  the  PT  studies;  results  were  evaluated  for  precision  and  systematic  bias (http://www.ec.gc.ca/inre‐nwri/default.asp?lang=En&n=7A20877C‐1)   The Environment Canada PT Program is comprised of two PT studies, offered on a semi‐annual basis, and scheduled  in  the summer and winter months. The samples are prepared  in natural background waters from  lakes, rivers or rainwater, and are fortified or preserved as necessary. The  trace  elements  in  water  samples  are  generally  divided  to  reflect  both  low  and  high concentration  ranges.  Participating  laboratories  submit  results  for  parameters  they  routinely analyze.   Since  the  fall  of  2002,  the  Onondaga  County  Environmental  Laboratory  has  routinely participated  in  the PT program  for  total phosphorus  in water.  In 2008,  the  laboratory began participating in the PT program for mercury in water. The County laboratory plans to continue to participate in the Environment Canada PT program.   

Results – Total Phosphorus In  2011,  the  Onondaga  County  Environmental  Laboratory  participated  in  PT  Studies  0097 (December  2010  to March  2011)  and  0098  (June  to  September  2011)  for  total  phosphorus analysis  (see  attached  copies  of  the  Environment  Canada  Proficiency  Testing  Program  Study 0097 and 0098).   The  performance  of  the  laboratory was  rated  as  “satisfactory”  for  PT  Study  0097,  and  “very good”  for PT Study 0098.   For PT Study 0097, one  (1) of  the  ten  (10) samples  for Phosphorus exceeded the warning limit and another sample exceeded the acceptance limit.  Included in this section is the result of the investigation and remedial plan that was conducted by the Onondaga County  Environmental  Laboratory,  as  a  follow‐up  to  this  Study  (memo  dated  April  4,  2011).  Previous proficiency testing (2005 through 2010) through the Environment Canada PT program has generally been “Good” to “Satisfactory”, based on the percent score per study.   

Results – Mercury  In 2011, Onondaga County participated in PT Study 0098 (June to September 2011) for mercury analyses.  The  performance  of  the  laboratory was  rated  as  “very  good”.  Previous  proficiency testing (2008 and 2009) for mercury through the Environment Canada PT program was “Poor” in 2008, “Good” in 2009, and “Good” in 2010, based on the percent score per study. 

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Onondaga County Department of

Water Environment Protection

Inter-Office Letter

Subject: AMP Proficiency Test Sample - Environment Canada Study # 0097 To: Janaki Suryadevara From: Mark Fowkes Date: Monday, April 4, 2011 CC: Jeff Noce, Jeanne Powers An investigation on the above noted PT set was conducted to check for possible error(s) as to why the acceptance criteria was exceeded on one of the ten samples from study # 0097. To briefly review, our laboratory received a set of ten samples at various concentration levels from Environmental Canada on December 7, 2010. All ten samples were tested for Total Phosphorous using a manual spectrophotometer method. One of the ten samples for Phosphorus exceeded the warning limit and another exceeded the acceptance limit. Standard laboratory practice is when a proficiency test result exceeds the warning limit but is within the acceptance limit, the laboratory is to check for possible errors, even though the result is acceptable. Samples that exceed the acceptance limit are unsatisfactory and an investigation must be conducted and action taken to correct the problem. Below are the results of that investigation, conclusions, and any remedial plan. 1. Review of digestions and analyses: (see attachments)

a. PT samples (Study 0097) were received as a double blind (unknown concentration levels to either the laboratory or the analyst) set and integrated into part of the regular analytical sample load. As part of our normal procedure, these samples were treated as regular samples and digested along with the rest of the week’s samples.

b. Samples were prepared on December 13, 2010 and analyzed on December 14, 2010 using one of the laboratory’s spectrophotometer following method reference Standard Methods 18th Edition, 4500-P E. All quality control solutions and results fell within the laboratory’s acceptance criteria as outlined in the section’s method SOP Document No. Wet-9 for total phosphorus.

c. The total phosphorus concentration on four samples exceeded the highest standard concentration of 0.300 mg/L. As per laboratory and NELAC protocol all samples must fall within the standard calibration range. Therefore, all four samples were manually diluted that same day and re-analyzed.

d. Review of all QA/QC batch analysis indicated compliance (see checklist below) for all quality control criteria.

Batch QC Checklist

1. Calibration Correlation Coefficient equal to or greater than 0.955: Yes 2. Initial Calibration Verification (secondary source standard) within acceptance criteria: Yes 3. Continuous Blank below MRL: Yes 4. Laboratory Reagent Blank below MRL: Yes 5. Laboratory Fortified Blank below MRL: Yes 6. Continuous Calibration Verification(s) with acceptance limits: Yes 7. Laboratory Fortified Sample(s) within acceptance criteria: Yes 8. Duplicate Difference(s) within acceptance criteria: Yes

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Table 1 QC Solution 1st Run 2nd Run Acceptable result or range LOQ - Limit of Quantitation 130 % 110 % 60-140 LFB - Lab Fortified Blank 106 % 99.8 % 88 - 111 ICV - 2nd Source Standard 112 % 100.2 % 85 - 115 LFS - Laboratory Fortified Sample 102 % 100 % 82 - 116 CCV1 - Continuous Calibration Verification 107.2 % 102.1 % 85 - 115 CCV2 - Continuous Calibration Verification 106.1 % 98.8 % 85 - 115 LRB - Lab Reagent Blank <0.003 <0.003 <0.003 Duplicate RPD 4.4. % 2.0 % < 10 % 1st run analysis was performed on 12/14/10. Prepared on 12/13/10 2nd run analysis was performed on 12/28/10. Prepared on 12/27/10 Table 2 PT Samples Assigned Value 1st Run (mg/L) 2nd Run (mg/L) PT97-5 0.003 0.007 0.005 PT97-6 0.022 0.027 0.023 PT97-7 0.002 0.005 <0.003 PT97-9 0.008 0.010 0.007 2. Review Of Method(s):

a. A review was conducted of analytical SOP Doc. No. “Wet-9”, which also details the preparation procedures for treatment of samples before analysis of total phosphorous. The review with the technicians indicates that all procedures were conducted properly.

b. A review was conducted of analytical SOP Doc. No. “Wet-9”, which details the general procedures for TP determinations of total phosphorus using spectroscopy. The review with analyst indicates that all procedures were conducted properly.

3. Discussion:

a. Total phosphorous is routinely performed using Standard Methods 18th Edition, 4500-P E on the laboratory’s spectrophotometer instrument. The laboratory has been using this approved EPA method for over twenty years. Additionally, the laboratory has successfully achieved acceptable NYS certification PT results for this method when determining total phosphorous.

b. The samples were integrated into the laboratory’s normal workload and analyzed by the same methods as our routine ambient water samples. They were taken through a preliminary digestion using sulfuric acid and ammonium persulfate. All samples were heated and taken down to a volume of approximately 5-10 mL. The samples were cooled and pH was adjusted using 1N NaOH drop wise to just below the phenolphthalein endpoint (sample pH is taken to the endpoint and then back down using one drop of 1M H2SO4 acid. All samples are then brought back to 50 mL solution volume.

c. All batch quality control solutions (see table 1) during the analysis of the PT samples (Study 0097) were acceptable and performed according to the stated procedures.

d. The PT set was first analyzed on 12/14/10 and results reported from this batch. A second analyzes was performed on the PT set on 12/28/10 to verify results.

e. One of the ten PT samples exceeded the high acceptance limit and the result was beyond 3 standard deviation of the calculated mean resulting in a flag of “AH” for acceptance high. One phosphorous sample showed a flag of “WH” indicating that the laboratory result exceeded the warning limits on the high side. This means that the results were between two and three standard deviation above the assigned value.

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f. The phosphorous PT samples were evaluated for possible bias using a standard “Z-Score”. If a laboratory is concluded to show bias, the results are flagged accordingly. The evaluation report did not find any bias for the phosphorous.

g. A performance rating was also provided for phosphorous. The phosphorous results received a “satisfactory” rating. The “satisfactory” scored is given when 2 up to 5 results have been flagged. In this case there were 2 samples flagged.

h. A total of 38 laboratories participated in the study. Assigned values for each sample was calculated using reported lab results that were not below or less than their reporting limit.

4. Conclusions: Sample PT97-5 was flagged "AH" and exceeded the acceptance limit. The calculated assigned value for this sample was 0.003 mg/L and the acceptance range is from zero to a high of 0.0068 mg/L. The laboratory reported a value of 0.007 mg/L which means that the result exceeded the limit by 0.0002 mg/L. Sample PT97-6 was flagged "WH" and exceeded the warning limit. The calculated assigned value for this sample was 0.022 mg/L and the high warning limit is 0.02636 mg/L. The laboratory reported a value of 0.027 mg/L which means that the result exceeded the limit by 0.00064 mg/L.

A review of the QC data from the analysis date of 12/14/10 shows that all quality control samples had acceptable recoveries but it also shows there was a slightly high bias (see table 1 above) since all recoveries were above the mean. A second set of analysis was performed on 12/28/10 for the PT set and quality control data was better in that the recoveries were both above and below the 100% mean value. In addition, the second set of analysis had results slightly lower (see table 2 above) then the first run.

Since the first set of analysis had all QC data that was acceptable, results were reported from this determination. However, taken as a whole, the QC data shows a slight bias high and appears to have affected the sample results by about 0.002 or 0.003 mg/L. Just enough for the low level PT samples to either pass or fail the acceptance criterion. 5. Remedial Plan:

Laboratories which have test results fall outside established control limits is expected to occur occasionally regardless of how well a laboratory performs. Such data are evaluated in comparison with control chart characteristics including the width of the acceptance limits and the degree of departure of the value from acceptance limits. The goal of including any PT samples is to be able to help identify and control errors that may occur during the sample preparation and analytical processes. Therefore, I think that PT samples from Environmental Canada are useful in closely examining our processes especially at the lower range of detection. For this particular set of PT samples, the laboratory results were internally deemed acceptable since all analytical quality control was acceptable. However, these PT samples showed that when the laboratory has analysis at very low levels, the level of uncertainty can be increasing and further examination of all QC results is necessary.

Therefore, interpreting and evaluating analytical QA/QC results is critical in meeting AMP and laboratory quality objectives. I have recently written and distributed a document to the laboratory staff with the intent of helping analysts and supervisors examine how best to evaluate QA/QC results and what actions can be taken to determine if analytical errors may have occurred or the level of uncertainty is increasing. I have also taken time to discuss this document with each laboratory section and answer questions related to their routine analysis. Regular review and instruction of these guidelines should help control these issues in the future.

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PT Study 0097 Results PT Sample TP97-1 TP97-2 TP97-3 TP97-4 TP97-5 TP97-6 TP97-7 TP97-8 TP97-9 TP97-10 Lab Sample# 201014972 2010014974 2010014978 2010014979 2010014980 2010014981 2010014982 2010014983 2010014984 2010014985 Result (mg/L) 0.292 0.314 0.178 0.540 0.007* 0.027# 0.005 0.864 0.010 0.705

Assigned Value (mg/L)

0.273 0.315 0.168 0.546 0.00300 0.0220 0.00200 0.869 0.00800 0.713

Hi Warning Limit

0.3026 0.3458 0.1854 0.5982 0.005538 0.02636 0.008224 0.953 0.012308 0.783

Hi Acceptance Limit

0.3174 0.3612 0.1941 0.6243 0.006807 0.02854 0.011336 0.995 0.014462 0.818

SD 0.0148 0.0154 0.0087 0.0261 0.001269 0.00218 0.003112 0.0420 0.002154 0.0350 N 38 38 38 38 22 37 10 37 33 37 Note: #Exceeded high warning limit: between 2 and 3 standard deviations (SD) of the assigned value. *Exceeded high acceptance limit: greater than 3 standard deviations (SD) away from the assigned value. N value is the number labs where the results were used to calculate the assigned value.