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General Questions |
| What
is the difference between accuracy and precision? Accuracy is a measure of how close a test result is to the actual value. Precision is a measure of how close a test result is to a repeat of the test. One way to look at this is as though you are target practicing. The pictures below help to illustrate the different ways that accuracy and precision can impact your test results. |
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| Precise-Accurate |
Precise-Inaccurate |
Imprecise-Accurate | Imprecise-Inaccurate |
| How
much quality control
over results does CRL have? CRL’s quality control program is extensive and is contained in our QA/QC (Quality Assurance/Quality Control) Manual. The Table of Contents can be found at http://chemrightlabs.com/QAQC.htm. Whether it is a soil sample or drinking water we estimate that 20-30% of the samples that we run are not customer samples but rather the extensive QA/QC program samples that are designed to give you and us the highest confidence in our data. Why should I use CRL instead of the lab I am currently using? Three reasons – 1) We are close – and that can mean a lot in terms of sample shipping costs and turn around time. You can stop in and visit the lab at any time. 2) Accuracy – we will not compromise the quality of data in order to keep our costs down. Our customer’s needs come first. 3) Trust, CRL is owned and operated locally. David Gossman, owner, is a local farm owner and was named 2004 Outstanding Woodland Owner by the Jackson Soil & Water Conservation District. How qualified are the people at CRL to perform soil, water and plant testing? CRL has a team of highly qualified chemists and other professionals please visit http://chemrightlabs.com/contacts.htm for more information on the qualifications of our staff. What equipment does CRL use for metal testing? How does that differ from other labs or from the test kits that are used in the field? There are numerous methods for testing for metals in soil and water. Some of these are simple field tests that are done with color comparative methods. We have some of these available for use when there are special needs but these tests frequently use toxic chemicals, and are not very sensitive or accurate. A farmer friend refers to these as “bathtub chemistry”. Another method that is used by many labs utilizes an ICP (inductively coupled plasma spectrophotometer). This method is fast and has the advantage of good detection limits and simultaneous testing of many metals all at once. It has the disadvantage of numerous interferences (many of which are found in soil). To often the results from the computer are provided to the customer without a close look by a chemist with the experience to spot and correct for these interferences. We have seen many errors over the years from numerous labs when using this test method – even from highly qualified commercial industrial labs. An older and somewhat more reliable technique utilizes an AA (atomic absorption spectrophotometer). This is the method that CRL uses for most samples because of the historic accuracy and reliability of the equipment. The most current and expensive option for metal testing is ICP-MS (inductively coupled plasma – mass spectroscopy). When this equipment is used by a skilled professional it produces the most accurate and sensitive results for most metals. As our business level develops there may be a time when CRL can afford such equipment. In the meantime we will stick with equipment we know can produce reliable results at a reasonable cost to our customers. Can you email my results to me? Yes. Just let us know your email address when you drop off your sample. We can send your results via email, regular mail, both or by fax. Why shouldn’t I use the lowest cost lab I can find for soil or water tests? Aren’t they all the same? No, they are not all the same – we have all heard the adage that “you get what you pay for”. This is as true for lab services as anything else. We have heard of operations that take the soil samples in the field and provide the results for less than $10/sample. It does not take a lot of thought to realize that corners are being cut somewhere. We can work with you to develop a quality sampling and testing program that will result in real cost savings and increased profits. Can I visit and tour the laboratory? Certainly! We love to have visitors and give tours of the lab. You are free to stop by any time but to get the “full tour” please call ahead so we can make sure someone is available to show you around. Do the tests that CRL performs on soil or water samples generate any hazardous wastes? No, although that is not the norm for many laboratories! We have extensive professional experience in the waste management industry and know the liabilities that our customers and we incur if hazardous waste is generated. We have specifically ruled out lab methods that generate hazardous waste, even if they are faster and cut lab costs. That is part of our commitment to the environment. Join us in this commitment – tell whichever lab you use that they are not to use any procedures that generate a hazardous waste requiring disposal. What are the important questions I should ask to help choose the right lab to do my soil or water testing? What are they doing to insure data quality? What are they doing to make sure that they do not generate hazardous waste and create an environmental burden? Are they certified by the state of Iowa? Does a professional directly supervise all testing and review all customer reports? What is the professional experience of the lab managers and owners? Can you review the standard operating procedures and methods that are used on your samples? Water Testing
What types of tests for bacteria does CRL use and why? ChemRight uses a variety of different methods. For request of bacteria Present or Absent, we use a product form IDEXX® called Colilert®. For quantitative analysis we use the IDEXX® reagent utilizing the quantitray technique or mColiblue 24® from Millipore®. These methods are EPA approved for drinking water and surface (ambient) water. We use these methods because they are so specific that they do not require confirmation tests, which allows us to provide faster feedback to our customers. Are there different methods for testing nitrate and fluoride in drinking water? Which ones does CRL use and why? There are a number of methods for both of these parameters. The most common is the use of an ion specific (or selective) electrode. While CRL has some of this equipment, we prefer to use ion chromatography for both fluoride and nitrate in drinking water. Ion chromatography is the most accurate and reliable method available. If I have drinking water from a well how often should I have my drinking water tested? The state of Iowa and the EPA recommend that users of well water have it tested for bacteria and other potential parameters of concern once per year. http://www.extension.iastate.edu/Publications/PM1563G.pdf . How long does it take to get water test results back? You results should be available within 2-3 days after you submit your water sample. Can I just grab a sample of water from my kitchen sink tap and bring it in to CRL for testing? You could but it is not likely to provide an accurate test – especially if you want to check for bacteria. Please visit http://chemrightlabs.com/Sampling Water and Wastewater.pdf for detailed instructions on proper drinking water sampling, or stop by the lab and we can give you a sterile container to take the water sample, along with complete instructions to make sure your results will be accurate. My current lab charges extra for 24 hour rush service for bacteria testing. Why doesn’t CRL provide this service? Proper bacteria testing should be started within a few hours of taking the sample and will generally be available the day after the sample is dropped off at the lab. There is no need to charge extra for a procedure that must be done in strict accordance with EPA and state time requirements. Why does CRL require that samples for bacteria testing be dropped off prior to 3pm Tuesday through Thursday? Why can’t I drop off a sample for bacteria testing on Friday? Bacteria tests need to be started within a few hours of arrival at the lab. Someone properly trained, must process the sample and then read the results 24 hours later. Having your samples here by 3pm provides us the necessary time to complete the sample prep and get the samples into the incubators prior to closing at 5pm. Normally we can not accept samples on Friday because the lab is not open on Saturday for someone to read the results. Why is it so important to use a local lab for bacteria testing? Bacteriological testing requires that the testing begin within a few hours of taking the sample in order to insure quality results. Overnight shipping of samples to a more distant lab could result in false positive or false negatives and is not an option recommended by EPA or the State of Iowa if it can be avoided. My dentist has suggested that I have my well water tested for fluoride – can CRL perform this test and provide the results to my dentist? Yes. Just let us know when you drop off the sample and we can provide an extra copy of the test report you can send to your dentist. That way your dentist can evaluate the naturally occurring fluoride you are getting in your drinking water and adjust your dental treatments accordingly. The water report that I received from ChemRight indicates that total coliform bacteria are present in my water. Now what do I do? Simple mistakes can often mean the difference between an accurate sample and an inaccurate one. For example, inadvertently touching the rim of the collection bottle with your hand or not properly flushing the water line can result in an "unsafe" reading, even though your water may be perfectly safe. At this point, you have two choices: take additional samples at strategic locations (i.e. at the well head; before and after water treatment devices) or contact your county sanitarian to complete a sanitary survey on your well and distribution system. What should I test my water for? If
you are concerned about the general health and safety of your
water, then the state of Iowa recommends testing for total coliform
bacteria
and nitrate - the two most common contaminants that Iowans are likely
to find
in their water. How do you convert mg/L (milligrams per liter) to ppm (parts per million)? The measurements are identical: 1mg/L = 1ppm. What is the infant health advisory limit for nitrate? Is it safe for adults? The infant health advisory or MCL (maximum contaminant level) established by the Environmental Protection Agency is 10mg/L (as N) or 45mg/L (as NO3). An infant consuming high levels of nitrate may develop methemoglobinemia, also referred to as blue baby syndrome. Ingesting high levels of nitrates will not cause methemoglobinemia in adults. Just
because water has an off taste or is discolored does not
always mean that the water is unsafe for human consumption. There are
naturally
occurring bacteria and chemicals that can cause taste and odors that
aren't
harmful to you. My water has a very bad odor - like rotten eggs. Is it safe to drink? How can I get rid of the odor? Rotten egg odor is usually due to the presence of hydrogen sulfide. This contaminant can cause taste and odor problems in water, but the presence of hydrogen sulfide is not a health threat. I want to test for everything bad in my water. Can you do that and how much will it cost? Testing for EVERY possible contaminant in water is not only cost-prohibitive but also usually unnecessary. If you are concerned about the safety of your water, the best approach to take is to limit the testing to reasonable contaminants. The state of Iowa recommends testing for total coliform bacteria and nitrate, which are good indicators of water quality. However, if you are aware of a nearby chemical spill or that a chemical was accidentally back-siphoned into your well, be sure to request a test for the specific contaminant. Are iron bacteria harmful? Iron bacteria are common organisms found in groundwater. These organisms do not pose a health threat, but they are considered nuisance organisms because they can cause taste, odor and/or staining problems. I think my water is making my livestock sick. Can you test the water for this? If you are concerned that your livestock's health is at-risk, consult your veterinarian. S/he can determine if the illness is linked to the water or some other source. If it is determined that the cause for your animal's illness is linked to the water supply, then ChemRight will test for the specific contaminant recommended by your veterinarian. How do I convert gpg (grains per gallon) into mg/L (milligrams per liter)? Generally, mg/L is used by the scientific community and gpg is used by the water treatment industry. The conversion formula is: 1 gpg = 17.1 mg/L. What's that white stuff in my collection bottle? The "white stuff" found in some coliform sampling bottles is sodium thiosulfate, a chlorine neutralizing chemical that inactivates chlorine so that a valid total coliform bacteria test can be obtained. The sodium thiosulfate should NOT be rinsed from the bottle even if there is no chlorine residual in the system. What is the unsafe level of nitrate for adults? The effect of nitrate on adults is unclear and no unsafe level has been established. However, high levels of nitrates have been linked to certain types of cancer in adults although there has been no definitive cause and effect established. Where should I collect the water sample? Where you collect your water sample depends on your purpose for testing. Generally speaking, the sample should be taken from the faucet that is most frequently used for drinking purposes. My sample has total coliform bacteria. Will I get sick? Not
necessarily. By
themselves, total coliform bacteria are not a health problem. However,
the
presence of coliform implies that the system has been compromised and
harmful
organisms may already be present or have the opportunity to enter the
system. Since it is impossible to test for the presence
of all possible harmful microorganisms, if coliforms are found in the
drinking water, the water should be considered unsafe for human
consumption and
corrective measures taken.
If
I add chlorine to my
water, will it be safe to drink? Prior
to chlorination, any defects that allow total coliform
bacteria to enter your water distribution system should be fixed. To treat a total coliform bacteria problem
with shock chlorination, you must have both an adequate amount of
chlorine and
an adequate amount of contact time (between the water and the chlorine)
to
destroy the microorganisms. I have a family member with giardia; can you test for this? Collecting and testing specifically for giardia is difficult and therefore drinking water is screened for the possible presence of giardia (or other parasites) by first testing for total coliform bacteria. If the drinking water is free of total coliform bacteria, then it is extremely unlikely that giardia is present and no further testing is necessary. However, if total coliform bacteria are detected, consult your county sanitarian for additional guidance. What's a "chloroform?" "Chloroform" is a common way that coliform is incorrectly pronounced. It is also a chemical that can be found in drinking water as a byproduct of the chlorination process. I know I shouldn't drink bacterially unsafe water, but can I wash my dishes, take a shower, and brush my teeth with this water? There is some risk in using bacterially unsafe water for any of these activities. To ensure your safety, use water that falls within the limits of the MCLs (maximum contaminant levels).
By measuring soil nutrient levels with representative sampling, quality testing and quality results you can better gauge the amount of nutrient that needs to be added to the soil each growing season. A good or bad growing season one year can significantly alter the nutrient requirements the next year. Don't leave dollars on the table by over fertilizing or under fertilizing. Margins are tight enough without working in the blind. A little money spent on obtaining quality data is like a good insurance policy designed to make certain that you maximize your return on the investment of money and time that you risk each crop season. How can some soil testing laboratories charge such a low price for soil testing? Many soil testing labs are forced to compete for business from fertilizer companies who provide them with thousands of samples each testing season. In order to compete for this work they are forced to use low cost seasonal labor with minimal training. Obviously, under those circumstances, corners can be cut and the quality of the data can suffer. CRL prefers to market our independent services directly to the farmer or crop consultant rather than work through middlemen where low bids are preferred, data quality can suffer, and farmers may end up paying a marked up price any way - either directly or indirectly in fertilizer costs. Why do I not get the same results for soil samples sent to different laboratories? There are a number of reasons that you may not see the same results from samples sent to different labs. First and foremost is that what was sent was likely two different samples. Soil is not a very homogeneous material. It is very difficult to mix and blend a sample of soil to the point where it can be split and have the same results. Professionally, this is done by drying and grinding the sample. Even if the sample is professionally dried and ground prior to being split the two labs are likely using different test procedures. Talk to both labs and make sure that you are not making an “apples and oranges” comparison. Finally, no matter how much the sample and testing is the same there will be some inherent variability that will vary from sample to sample and test to test. If you still have concerns meet with someone from the labs to review and explain your data. The most important question to ask is “does the differences in data result in different recommendations for nutrient application based on state and university guidance?” My fertilizer supplier already samples and tests my soil – why should I bother with CRL? Can I assume for the moment that we have all heard the one about the fox guarding the hen house? Seriously, the whole purpose of testing your soil is to determine how much fertilizer is really needed – not how much someone wants to sell you. Given today’s high cost of fertilizer can you afford to not have an independent check? A number of CRL farm customers have found that they had been over fertilizing fields and have saved considerable money since getting CRL soil tests. If you want your local fertilizer company to continue to take the samples just tell them to send the samples to us so you can get an independent report directly from CRL. Don’t forget, they are not providing those results free of charge. Whether they are a separate line item, or figured in the price of your fertilizer, you are still paying for them. Why can’t CRL give me advise about micro-nutrient requirements for my fields? – my current lab provides this information. Either your lab is not certified in the state of Iowa or they are breaking Iowa law! From http://www.state.ia.us/government/ag/working_for_farmers/advisories/micro_nutrients.html the state attorney general’s office states “Iowa's soil testing laboratory certification program prohibits participating laboratories from making any recommendations regarding the application of soil micro-nutrients other than zinc.” CRL can provide micronutrient data but based on Iowa law cannot make recommendations. To date, samples we have tested for micronutrients have not shown any significant deficiencies based on university recommendations. Soil labs seem to do lots of different tests for phosphorous – which one should be used? The state of Iowa has an excellent article on this issue at http://www.ipm.iastate.edu/ipm/icm/2003/11-17-2003/mehlich.html. CRL uses the standard Melich 3 spectrophotometric test, not the ICP method. While there is convenience and lower costs to the lab by using the ICP method we do not consider this method to be accurate enough. Instead we use the colorimetric method enhanced to produce more accurate results by using a high resolution UV/VIS spectrophotometer. Inaccurate phosphorous results can result in significant costs to a farmer – either in wasted fertilizer or lost production. CRL uses the most accurate and best validated method available. What does the Cation Exchange Capacity (CEC) measure? Essentially it is a measure of the ability of soil to hold nutrients. Think of it like a bucket. The bigger the bucket, the more it will take to move from one level of fullness (say half full) to another level (say 3/4 full). So, for instance, a soil with a lower CEC will take fewer nutrients or less time to make a certain degree of change compared to a soil with a high CEC. Because of this, high CEC soils have what we call a greater buffering capacity, which means that we can do more acid forming things to it, for instance, before it moves from 6.9 clear down to 6.5. Why does it cost so much less for soil tests when I have 5 or more samples? Each soil test that CRL runs requires extensive sample preparation. If we can process a group of samples together there is considerable cost savings and we pass that savings on to you, our customer. |