Day 19 - 1 - Correction to "Day 18 Blog Posting"

Regarding Day 18's post, I made in error in the calculation of oxygen and moisture amounts in CERES high pressure gas tanks. The values reported in Day 18's post  (i.e. oxygen = 35L/tank and moisture = 50 g/tank) are likely overestimates. These values are important because they will be used to determine purifiers appropriate for CERES. I will report further on this later today. 

Day 18 - Instrument diagnosis and strategies for moving forward

I arrived at CERES at 8AM and departed at 5:15PM

Two techs from Technical House continued work on the GC-ECD today. Specifically, they investigated the health of the detectors.  After about 3 hours of work, they concluded that the back detector needed to be replaced and that the front detector was almost at the point of needing to be replaced. They also continued to emphasize the importance of supplying the instrument with gases low in oxygen and moisture. This work will not be carried out until CERES has developed a strategy for ensuring high purity gases will be delivered to the instruments at all times. I think that this is a wise decision.

Opened up instrument and a Technical House tech

Exposed electron capture detectors

I spent the remainder of the day looking through product catalogs for purifiers that could meet CERES' needs. I also consulted with Glenn Wilson and Kim Anderson of OSU for their opinions on the matter. Additionally, I took this opportunity to talk with Anna and Marie and teach them about how to properly instal in-line gas purifiers so that they worked effectively and reproducibly. Topics covered included: how to use an indicating purifier, proper sequence of purifiers, the purity of gases that the instrument requires, strategies for ensuring that purifiers are operating correctly. We will not be able to process anymore passive sampling device samples due to the limited amount of time remaining for my stay at CERES, . However, I will review how to use and fill out chromatography bench sheets with Anna tomorrow so that she can analyze the samples once the instrument has been set up correctly.

Day 17 - GC-ECD and purifiers

I arrived at the lab at 7:50AM and left around 4:45PM.

I investigated more into the gases that supply all CERES GC instruments (ECD and mass spectrometers). The purity of nitrogen and helium that CERES purchase is 99.995%. Agilent, the manufacturer of the instrument involved in this study, recommends using gases of >99.9995% purity with the GC-ECD. Gas specification sheets requested from CERES’ supplier (Air Liquide) report that nitrogen and helium gases at the grade that CERES purchase have <5ppm of both molecular oxygen and molecular water (i.e. moisture). Assuming the worst case scenario, that gases being supplied to instruments have 5ppm oxygen and water, EACH HIGH PRESSURE GAS TANK at 10m^3 should contain ~ 35 L of oxygen and ~ 50g of moisture (i.e. water). 

CERES currently has two nitrogen gas purifiers on their 1/8” gas lines: 1) an Agilent GMT-2HP moisture trap and 2) an Agilent Big Universal oxygen, moisture, and hydrocarbon combo-trap. The GMT-2HP and Big Universal moisture traps have moisture capacities of 20 g and 46 g respectively. They have been in place since Lucas Quarles’ (OSU) training session in 2009 and through > 5 tanks of nitrogen/year since then.  Additionally, I did some reading on different types of gas purification traps and learned about a type called “indicating traps”. This type of trap contains a band of reactive particles that turn colorful when in the presence of the gas they’re supposed to filter. The Agilent GMT-2HP moisture trap is an indicating trap and it currently displays a bright blue bland (See picture below). In regards to moisture, I conclude that both traps have exceeded their capacities and are not purifying nitrogen for moisture. The Agilent Big Universal trap has an oxygen capacity of 1.07L. Considering that EACH NITROGEN TANK maximally has 35L of oxygen, I’m confident that the trap’s capacity was also reached a very, veRY, VERY long time ago and that this trap is not purifying CERES' nitrogen of contaminant oxygen.

 Agilent GMT-2HP moisture indicator trap

 

Big Universal oxygen, moisture, and hydrocarbon combo-trap - Nitrogen Specific

On the helium line, CERES currently has a single helium specific Agilent Big Universal oxygen, moisture, and hydrocarbon combo-trap with the same capacities described earlier for the nitrogen version of the purifier. CERES helium has <5ppm of oxygen and moisture. Considering the argument provided above and that the purifier was also installed during Lucas Quarles’ (OSU) training session, I’m confident that this purifier also reached capacity a long time ago. In summary, CERES is not currently set up to deliver the purity of gases needed to effectively run the GC-ECD in a reproducible manner for this project or any other for that matter. Additionally, they have developed conditions that most surely have damaged internal components of the GC-ECD instrument, including but not limited to the analytical columns and the electron capture detector. 

 Big Universal oxygen, moisture, and hydrocarbon combo-trap - Helium Specific

The GC-ECD technician  from Technical House, mentioned yesterday, arrived around 3PM. He worked on the instrument detector for ~ 15 minutes and concluded that gas purity in combination with ineffective gas purification led to the current state of the ECD. He will be back tomorrow to work on the instrument. However, I was unable to decipher exactly what he’d be working on. Furthermore, Anna called around to local industries looking for gas purifiers that CERES could grab in a timely manner. The search was not successful and frankly I don’t think it wise for the lab to rush through this step. In contrast, I recommend that CERES should develop a well thought-out strategy for consistently maintaining laboratory instruments at a degree capable of conducting trace chemical analysis. 

Specific points:

1. CERES should investigate other high pressure gas suppliers to evaluate options and compare prices
2. CERES needs to purchase gas purifiers capable of meeting instrument needs relative to the purity of purchased gases. They are generally <$300 each and would save on laboratory down time, column replacement, detector degradation, equipment replacement, and service appointments with contractors. They should also have extra purifiers on hand for quick replacement. Achieving this objective would increase CERES workflow substantially across ALL projects.  
3.  Many of the concepts that I have discussed with CERES personnel seem to be familiar, but they do not carry them autonomously. CERES needs more training on the basics of instrument set-up and maintenance – specifically the “WHY THIS IS IMPORTANT” portion of that lesson.
4. CERES currently has their indicator traps positioned before their high capacity purification filter. This defeats the purpose of the indicating trap – to indicate when contaminant break through has occurred. CERES should plumb indicating traps after high capacity traps.
5. CERES have several extra traps, but they have been stored ineffectively and are suspect for contamination – for instance open to the ambient environment (see below and notice the uncapped ends of connections and tubing). CERES should store ALL non-used traps as per manufacturer recommendations and sealed from the ambient environment.

Day 16 - GC-ECD continued...

I arrived at CERES around 8AM and left at 4:30PM.

 

Inspection of the instrument revealed that the detector baselines did stabilize, however both were significantly higher than before! Front = 870 +/- 1 Hz, Back = 1920 +/- 2.5 Hz. They were previously around 650 and 1200 Hz. I decided to run blanks to evaluate the baseline over the run. They both looked really cruddy… high baselines, continuous large saw tooth pattern, random systematic signal dips, and a step up and back down 2/3 of the way into the run. See below.

                                              Front Detector - n-Hexane Blank

                                                 Front detector zoomed in - n-Hexane Blank

                                            

                                            Back detector - n-Hexane blank

                                                 Back detector zoomed in - n-Hexane blank

 Everything that I’ve been reading points to low purity gases, saturated gas purifiers, and worn-out detectors; it wouldn’t surprise me if CERES has all three working together against them. Anna and I discussed this, I suggested she contact a technician, and she subsequently scheduled an appointment with a local Senegalese technician from a company called Technical House (not sure of the spelling). She told me that they will be here tomorrow morning, though not sure what time – they said that they would call and let us know tomorrow… Instrumental analysis continues to be on hold until instrument capability has been restored.

In spite of this set back, I’m still finding plenty of things to work on with CERES staff. For instance, I looked over the post deployment cleaning bench sheets that CERES should have filled out during the execution of the process before my arrival. However, no information was filled in for:

1)      The chemists that performed the activity

2)      Completion date and initials

3)      Solvents used (i.e. Isopropanol and HCl)

4)      Chemist review signature and date

I had Anna fill in the information right then and there and again communicated the importance of keeping tidy notes and completing project documentation for ease of reference later on in the project. I also helped Ann with some injection port maintenenace on CERES’ GC-MS. She handled new injection port liners with her bare hands, set them down on non-cleaned surfaces, and packed them with way too much wool using a pair of large tweezers – less than ideal. So I used the opportunity to discuss the importance of maintaining clean liners for achieving low baselines, showed her how to use a glass wool packing tool, and how to use acetone on a swab to clean out the injection port. I helped Anna organize GC tools and components into a small tool box for ease of locating. Also, I assembled a list of solvents used in this study and included chemical company name and purities for Kim Anderson (OSU). 

Day 15 - GC-ECD investigations

I arrived at CERES at 8AM and left at 3:30PM. Anna left around 11:30AM to defend her masters thesis; Woooohoooo Anna!!!!!

Anna and I investigated the portion of the instrument where the capillary columns connect to the make-up gas adapter today. Upon unscrewing the Swagelok nuts that fasten the make-up gas adapter/capillary columns to the detectors we found that both front and back detector 1/4" graphite vespel ferrules were in extremely poor condition; actually they crumbled apart inside the nut. Additionally, we found that both nuts were loose. However, both fused silica liners were in good working shape and were not replaced.

Columns were then re-installed, all other connections inside the GC oven were tightened, and then we purged the system with carrier and make-up gases for 15 minutes to remove oxygen. Anna and I then began to equilibrate the system with the GC-oven at 30C in case thier were air leaks. After 4 hours, the baselines stabilized (Front at 880 +/- 1Hz, Back at 2630 +/ 2.5 Hz), I loaded the GC-oven operating temperature for our analytical method, and that steady consistent baseline we had just obtained began to wander across the real-time display like the Mississippi river, similar to what was seen last Friday. At this point, I figured that the only variables still in my control that I had not tampered with were the columns. So I ramped up the GC oven to 310C and let is cook for 20 minutes. See below and notice the scale on the y-axis for the back detector, the front column was ~3-4 times lower than this:

Front Detector

 Back Detector

Once the big nasty stuff had abated, I dropped the GC-oven down to operating temperature - 110C and let it sit. This is what was found:

Front Detector

Back Detector

By 3:45 PM, detector background readings were continuing to plummet with no sign of stopping anytime in the near future. I concluded that it would take several hours for the system to re-equlibrate and decided to let it work towards this end until morning. I'll report back tomorrow.