MEMO
To: Soils and Geology Faculty, Staff, and Students
From: Dan Strawn
Date: 6/19/2009
Subject: ICP USE
The new iCAP- ICP is running well. It has much lower detection limits (at least 100 times lower for most elements) than the old IRIS-ICP, and runs samples much faster. The instrument is for research purposes, and it is our goal to make it available to students and researchers within UI soils and geology. Other users may also submit samples if Anita and Leslie are willing to run them. Below the cost and sample details are provided for you to consider. If you prefer a more routine analysis of water samples then inquire at the Analytical Sciences Laboratory, which can run samples and may be cheaper. The ICP web site has information for helping users planning to run samples: http://soils.ag.uidaho.edu/icp/ICP_rules.htm
ICP Cost
Based on the gas cost, instrument maintenance, and proposed usage of 12 hrs/month, the hourly cost for ICP time is $80/hr. This is a significant increase from the old rate of $45/hr, which has been in place for the past several years. The increase in cost is primarily because the cost of gases has significantly increased in the past two years, and because the new instrument requires more expensive high-purity gases. In addition, instrument usage has decreased and with it, efficiencies of scale. User time fluctuates with grants for soils and geology faculty, and demand by outside users. The good news is that the new iCAP is much more efficient than the old IRIS, so the same number of samples can be run in a fraction of the time previously needed. A budget number should be given before samples are run on the iCAP-ICP.
ICP Scheduling
To maximize cost efficiency we need to schedule runs to be done together. The timing will vary, but hopefully not more than 2 weeks will pass before samples can be analyzed. If you have several samples that will take at least 4 hours, then we can schedule the run when it is convenient for Anita or Leslie and user. Shorter run times that need to be run sooner will have to purchase the tanks of gas (currently $210) and pay the hourly charge (less gas).
Samples
Only aqueous samples can be run by iCAP-ICP. Solid samples must be dissolved or extracted to produce solutions for analysis. Leslie may be contacted about appropriate digestion methods for samples. All aqueous samples, whether natural waters or extracts of solid samples, must be filtered before being run on the iCAP-ICP. Users are required to provide their own filters (0.45 micron or finer) or will be charged $1 per filter for use of our filters. If samples have particles in them that clog nebulizer (rare it makes it that far, but it has happened), the user may be charged to purchase a new nebulizer (~$1200). Make sure samples are well mixed prior to running. Occasionally precipitates form in solution even after filtration. These samples will have to be re-filtered or preserved to prevent precipitation.
Standard Preparation
Good results depend on good standards. Making a good set of standards is notoriously a problematic task for students (and occasionally more experienced users). Poorly made or incorrectly labeled standards have been the most common source of problems with ICP analysis in our laboratory. If the user makes the standards and QC erroneously it can take several hours of ICP time, caused by trouble shooting, required purging, making new standards while instrument is running, and rerunning the samples. This time is charged to the user’s budget. Leslie and Anita have prepared a sheet outlining methods for making standards and can work with users on correct preparation and storage of standard solutions. We have commercial stock solutions for many elements which may be used, at a cost of 65¢ per ml, to prepare standards.
Matrix
High concentrations of salts or organics in the matrix are difficult to run and may cause an increase in run time and troubleshooting. The user will pay for the increased time usage, including troubleshooting. Some matrices damage the center (sample injector) tube, which costs $600 to replace, or the torch itself, which costs $800 too replace. Thus we request that matrices be diluted to less than 0.05 M if possible. Solutions high in organics should be diluted 1:10 at least. Anita or Leslie can advise on sample dilution requirements. For high concentrations of backgrounds the standards, QC, and blank must be matrix matched.
Operation
Anita and Leslie are the instrument operators and in charge of the maintenance for the iCAP-ICP. However, students should participate with the operation; it is not a sample drop-off lab. This includes being present during set-up and available during sample run (unless otherwise arranged with Anita or Leslie). Regular users can be trained to use the instrument independently. For example, if a user anticipates more than 5 runs over a 6 month period, they can be trained to run samples themselves. In this event, the operation should take place only during normal working hours when Anita and Leslie are available to help, if needed.