Contaminated Extracts

We viewed the chromatograms before performing the PSD cleaning and found severe contamination in the last extraction. The hexane blank that had been removed from the reagent bottle and placed on the GC was clean. However, the reagent blank that had been through the PSD method (dialysis, blow down, transfers, etc.) was very contaminated. A chromatographic comparison between the reagent blank and the lab spike (which also went through the method) is shown below (lab spike consists of 200 uL of a 1ppm dilution of Chemservice organochlorine pesticides mixture #1 – 508 in MTBE, cat # OCP508-1JM spiked into 100 mL hexanes, then extracted by the PSD method). Note that retention times, compound labels, and baselines have been removed for clarity.

A discussion with the CERES staff resulted in a careful evaluation of the entire extraction process. As this contamination occurred in the reagent blank, it could not be from the field extraction and therefore must have occurred during the dialysis, blow down, or transfer.

Today we are extracting a new reagent blank, a blank LFT, and the acetone from the wash bottle (used to clean the Rotavap-RBF joint between samples). Dirty glassware is suspected, however, several measures are being taken to rectify the situation. All glassware for the CERES/OSU split extraction is being cleaned again. The split extraction will not proceed until the situation is satisfactorily remedied.

In contrast, the standards appear much better. Below is an example.

Retrieval 2

Oct 8th

The electricity failed soon after the GC run was initiated (and we had left) on Friday afternoon. As described to me by Cheikh, the incoming grid electricity is of poor condition and the UPS uses battery power to compensate thus draining the UPS batteries. When the batteries are drained the grid power is insufficient to maintain the equipment and the UPS shuts down. The backup generator does not turn on because it still recognizes the grid power input regardless of quality.

Therefore, we have no data from last week’s extraction.

We are attempting to run the GC entirely off the backup generator while we are in Saint Louis in hopes that the clean signal from the generator will allow the GC to complete its run.

I am of the opinion that CERES needs a power conditioning unit to prevent abuse of the UPS and maintain instrument operation. Or a replacement UPS that is capable of better power conditioning.

Seraphim Dorego joined us to perform GIS work at the site then we left for St. Louis about 2:30 pm.

Oct 9^th

We arrived at Site 1 at about 8:15 and proceeded to retrieve two sets of PSDs, one set for CERES extraction and analysis and one set for OSU extraction and analysis. CERES staff in attendance were: Cheikh, Makhfousse, Anna, Marie, Adama, Sokhna, Madame Ndaiye. Abdoulaye Djiop again assisted with retrieval. CERES staff performed all work with minimal oversight and field bench sheets were competed in detail.

When we approached Site 1 we found the cages were lying horizontally on the bottom of the concrete canal. The PSD had significant fouling, but some may be rust from the non-stainless steel portions of the cages.

An interesting observation of the PSD is the increasing amount of fouling with increasing distance from the river. Site 3 cages are positioned in the Goron-Lamspar tributary and are very clean after two weeks, Site 2 in the main irrigation canal shows some fouling, while Site 1 at the drainage pump station shows the most severe fouling. It is not clear, however, if the fouling is rust, sediment, or biological.

From left to right: Site 3 in the river, Site 2 in the irrigation canal,

and Site 1 at the drainage pumping station.

In addition to the four PSD sites, we visited the drainage area south of the pumping station to allow Seraphim to collect GIS data. We observed livestock drinking at this site.

We observed bathing, washing of utensils and household water collection, as well as fishing at Site 1, and household water collection at Sites 2 and 3.

October 10^th

We left St. Louis too late to get back to Dakar early enough to perform the PSD cleaning, but we received word that the GC had successfully run all the loaded samples.