Determination of loss on ignition
By: S. Christie
Weight-loss-on-ignition is a common, widely-used method of approximating
the organic and carbonate content of sediment samples (Heiri et al. 2001).
LOI is rapid, inexpensive and easy to perform (Dearing 1986). LOI is based
on weighing samples before and after sequential heating and measuring
weight loss between reactions, and yields estimates of organic and carbonate
content with comparable precision and accuracy to more sophisticated geochemical
analysis methods (Heiri et al. 2001).
Problems with LOI analysis have recently been reported. According to
Heiri et al. (2001), recent paleolimnological studies show that there
is wide variation among the LOI methods used by different laboratories.
These differences become more important as paleolimnological studies become
more popular, as they make interlaboratory comparison of results problematic.
It is recommended by Heiri et al (2001) to carefully record the parameters
of ignition temperatures, ignition exposure times, and sample sizes in
the LOI methodology.
Following the recent call for a standardization of LOI methods, we are
following the LOI method cited by Heiri et al. (2001). Where this method
differs from the method formerly used at the Laboratory for Paleoclimatology
and Climatology, the old method (from Gale and Hoare, 1991) will be cited
- Prepare the core to be analyzed. Carefully unwrap the core, being
sure not to confuse which end is the top. Split the core, if necessary,
and rewrap the archive section.
- Measure the length of the core in centimeters, and consult the field
notes to verify the original length. It is common for the core to be
longer or shorter than it was originally, due to water loss and/or expansion
or contraction due to wrapping and rewrapping and time elapsed since
collection. If there is a discrepancy in length, you must compensate
for the difference in length by adjusting the intervals from which you
will sample. Instead of taking a sample every centimeter, you will compensate
for shrinkage/expansion by calculating what each centimeter in the core
has shrunk/expanded to. Correction is done by NEW LENGTH ÷ OLD
LENGTH. This will give a ratio, which can be rounded to 2 decimal places
(to facilitate measuring with reasonable accuracy). You will then sample
at intervals of the calculated ratio.
- Mark the sampling intervals on the core by scratching a line or mark
into the sediment with an instrument. Wipe all sediment off the instrument
before marking the next interval to avoid contaminating the core.
- Clean a series of crucibles by wiping them with paper towels. Weigh
the clean, empty crucibles and record this weight (CRUCIBLE WEIGHT)
by hand or directly on the computer using the Balink program. It is
important from this point on to only move the crucibles using tongs
to avoid contaminating and potentially altering the weight with oils
etc. from your fingers, and to avoid static which can cause "drifting"
weights on the balance. It is useful to record the crucible numbers
and weights in order and assign an interval to each before you start
subsampling the core. This way, you just have to check the crucible
number before depositing your sample, you don't have to stop sampling
to record which crucible corresponds to which interval.
- Take a 1 cm³ sample of sediment from each interval and place
the sample in the appropriate crucible. Be sure to rinse all instruments
with deionized water and dry them completely before taking the next
sample to avoid contamination. You may be asked to take additional samples
for future analysis. If so, place them in vials clearly labeled with
the Core and Drive Numbers, the interval, the sample size, and what
the sample is to be used for (if known).
- Weigh the sample and crucible to obtain the WET WEIGHT.
- Dry the sample overnight (14-24 hours) at 105°C. To avoid overheating,
place the crucibles in the oven after the desired temperature has been
reached. (The past method used required drying overnight at 95°C).
- Remove the samples from the drying oven using tongs and place in a
dessicator until they have cooled to room temperature. This should take
- Weigh the dry samples obtain the DRY WEIGHT/DW105.
- Place the crucibles in the muffle furnace, keeping about a crucible
width away from all sides. Ignite the samples at 550°C for 4 hours.
It will take approximately 20-40 minutes for the furnace to attain this
temperature, but you should begin timing as soon as the furnace is turned
on. (The past method used required ignition at 500°C for 3 hours)
- Carefully remove the crucibles from the muffle furnace and place them
in a dessicator until they cool to room temperature (30-40 minutes).
- Weigh the samples to obtain the IGNITION WEIGHT/DW550.
- Place the crucibles in the muffle furnace, again ensuring they are
not too close to the sides of the furnace. Ignite the samples at 950°C
for 2 hours. Note that for the furnace to attain this temperature, you
must set the temperature dial to the highest possible temperature and
only reduce the temperature in small increments once a temperature of
950°C has been attained. The furnace will take 2-2.5 hours to attain
a temperature of 950°C, and you should therefore start timing the
2 hour ignition time once the furnace has reached 950°C. (The past
method used required optional ignition at 925°C for 4 hours).
- Carefully remove the crucibles from the furnace once it has cooled
enough (the filaments are no longer red). Place the crucibles in a dessicator
and allow them to cool to room temperature (35-45 minutes).
- Weigh the samples to obtain the CARBONATE WEIGHT/DW950.
- The samples may now be discarded. Wipe any dust out of the crucibles
with a dry paper towel.
- Import or record your intervals, crucible numbers and weights into
Excel to facilitate the computation of organic matter and carbonate
contents of your samples.
Beaudoin, A. 2003. A comparison of two methods for estimating the organic
matter content of sediments. Journal of Paleolimnology 29 :387-390.
Boyle, J. 2001. Inorganic geochemical methods in paleolimnology. Pages
83-141 in W. M. Last and J. P. Smol, editors. Tracking Environmental
Change Using Lake Sediments. Volume 2: Physical and Geochemical Methods.
Boyle, J. 2004. A comparison of two methods for estimating the organic
matter content of sediments. Journal of Paleolimnology 31 :125-127.
Dean, W. E., Jr. 1974. Determination of carbonate and organic matter
in calcareous sediments and sedimentary rocks by loss on ignition: Comparison
with other methods. Journal of Sedimentary Petrology 44 :242-248.
Dearing, J., 1986. Core correlation and total sediment influx. In Berglund,
B. (ed.) Handbook of Palaeoecology and Palaeohydrology, JohnWiley and
Sons, NewYork: 247–270.
Gale, S.J., and Hoare, P.G. 1991, Quaternary sediments: Petrographic
methods for the study of unlithified rocks: New York, Belhaven Press,
Heiri, O., A. F. Lotter, and G. Lemcke. 2001. Loss on ignition as a method
for estimating organic and carbonate content in sediments: Reproducibility
and comparability of results. Journal of Paleolimnology 25 :101-110.