# Presentation: 491009

## HPLC Pigment Analysis at HPL

- Crystal S. Thomas
- Laurie Van Heukelem
- VIIRS/MODIS Science Team Meeting
- May 14, 2008

**Notes:**
Analytical Services-Horn Point Laboratory, I’ve been conducting HPLC pigment analysis for over 10 years
We have held a contract with NASA to analyze HPLC pigment samples for the last ~1.5 years
We have a proven track record of our ability to produce quality data, as supported by our clients and intercalibrations, particularly the SeaHARRE round-robins, coordinated by Stan Hooker

## Outline

- QA/QC
- Progress report
- What I need from PIs

**Notes:**
I’m going to 1. touch on some of our QA/QC procedures and data-don’t have nearly enough time to go into all of it
                  2. give an update as to where we are in sample processing right now
                  3. a few suggestions on what help us when we are analyzing HPLC samples

## Chl a calibration 1999-2007

**Notes:**
This is a graph plotting data from 40 sets of chl a calibration standards that were analyzed over a period of 8 years on the same method. This documents our performance over the entire time we’ve been using our current method. You can see that from these injections that we know that we have larger uncertainties with results that are below 3 ng/inj (circles in blue represent concentrations in our working range).

## Calculation Equation for Pigment Concentration

- Our QC measurements check every variable in our calculation equation

**Notes:**
This is an example of a calculation equation to determine pigment concentration. We make sure we have QC measurements that touch on every variable in our calculation equation. That way we can isolate sources of uncertainties and quantify the magnitude of that uncertainty

## Examples of Daily QC Measurements

- Injector precision
-     Avg CV%=0.4%, WL=0.8%, CL=1.3%
- Accuracy of chl *a* standard
-     Avg=-0.75%,WL=4.1%, CL=5.3%
- Calibration of solvent delivery device
-     Avg CV%=0.34%, WL=0.57%, CL=0.83%
- Retention time variability (on average no more than 0.07% within a sequence)
- Peak resolution documentation (Rs> 1.0)
- Carryover (no more than 0.1%)

**Notes:**
These are some examples of our daily QC measurements-all of these are checked at least once a day
WL=95% confidence limits, CL=99% confidence limits. If 3 sequential injections fall outside the WL or one injection falls outside CL, corrective action is taken

## Analysis precision v. method precision

- Daily analysis precision:  Replicate injections of sample extracts (min and max residence time)
- Daily method precision:  Duplicate filters

|  | Analysis precision
(CV%) | Method filter precision for HPL clients (CV%) |
| --- | --- | --- |
| TChl a | 0.4 (WL=1.6%,CL=2.2%) | 4 (1-10) |
| PPig | 1.8
(WL=4.7%,CL=6.2%) | 7 (2-11) |

**Notes:**
A few more of our daily QC measurements
Replicate extract-reinject 1st sample of the day at the end of the sample batch (injector precision, monitor for any effects of residence time in the autosampler compartment)
Compared to duplicate filter precision, ideally we should have about 5% of our samples should be duplicates
-if PI falls too far outside of this norm, they should investigate revisions to field sampling procedures

## Control Charts

**Notes:**
We use control charts to document behavior of all QC measurements for which it is feasible to do so, makes it quicker and easier to determine if method is in control

## Looking at QC Measurements in Context

**No analysis**

**= ISTD measurements**
**= chl a QC measurements**

**Notes:**
But QC measurements and control charts are more useful when multiple observations are observed in the context of one another. This example shows Chl a QC measurements, ISTD precision, and information about column and standard age. All of this information is considered together in order to more completely assess the condition of the HPLC and determine what corrective actions need to be taken if the method is out of control.

## Progress Report

- This year we will analyze 3700 pigment samples for NASA
- So far:
- Received 1205 samples
- Analyzed 575 samples
- Have 630 samples still in the queue
- Know of ~300 more samples to be shipped soon

**Notes:**
We’ve received about a 1/3 of the total samples for the year and have analyzed about 1⁄2 of those so far.
Its helpful when PIs let us know about future sampling plans as soon as they have details about them them so we can plan our analysis schedule and don’t get backed up

## What I need from PIs submitting pigment samples

- Duplicate filters-at least 5%
- Completed, correct sample information forms
- Communication, please contact me!

**Notes:**
Important part of our quality assurance plan, provides information to us and the PI
I waste a lot of time dealing with problems that shouldn’t be issues
Had to kind of fly through a lot of information, if anyone wants more details I am happy to provide