CARBON AND SULPHUR ANALYSES

Carbon and sulfur content in geological samples can appear in ppm to percent range. Determining these two elements simultaneous or as single determination can provide valuable information on mineralogy, metallurgy, and environmental issues pre and post project evaluation. These 2 elements can also be added to lithogeochemistry analytical methods.

Accelerator material is added to a 0.2g sample. The inductive elements of the sample and accelerator couple with the high frequency field of the induction furnace. The pure oxygen environment and the heat generated by this coupling cause the sample to combust. During combustion, carbon-bearing elements are reduced, releasing the carbon, which immediately binds with the oxygen to form CO and CO2, the majority being CO2. A small amount of carbon monoxide is converted to carbon dioxide in the catalytic heater assembly. Carbon is measured as carbon dioxide in the IR cell as gases flow through the IR cells. Carbon dioxide absorbs IR energy at a precise wavelength within the IR spectrum. Energy from the IR source is absorbed as the gas passes through the cell, preventing it from reaching the IR detector. All other IR energy is prevented from reaching the IR detector by a narrow bandpass filter. Because of the filter, the absorption of IR energy can be attributed only to carbon dioxide (CO2). The concentration of CO2 is detected as a reduction in the level of energy at the detector. The analysis is performed using ELTRA Instruments.

AnalysisMethodReporting Limit
4F-C TotalIR0.01%

4F – C Organic (calc)

The C-Organic is calculated according to the following:

C-Organic = Total C – CCO2 – CGraphitic
Carbon analysis is performed by the absorption of IR energy which can be attributed only to carbon dioxide (CO2) which absorbs IR energy at a precise wavelength within the IR spectrum. The concentration of CO2 is detected as a reduction in the level of energy at the detector. It can be measured in either an inert atmosphere or an oxygen atmosphere (binding carbon species with the oxygen to form CO (converted to CO2 prior to detection) and CO2, the majority being CO2, and is measured as carbon dioxide in the IR cell as gases flow through the IR cells. Energy from the IR source is absorbed as the gas passes through the cell, preventing it from reaching the IR detector. All other IR energy is prevented from reaching the IR detector by a narrow bandpass filter. Because of the filter, the absorption of IR energy can be attributed only to carbon dioxide (CO2). The concentration of CO2 is detected as a reduction in the level of energy at the detector. The Total C and CGraphitic analyses are performed using ELTRA Instruments. The descriptions of these methods are found in the website.

Reporting Limit
4F-C Organic (calc)0.5%

A 0.5 g sample is subjected to a multistage furnace treatment to remove all forms of carbon with the exception of graphitic carbon. Either a resistance or induction furnace is used for analysis. The inductive elements of the sample and accelerator couple with the high frequency field of the induction furnace. The pure oxygen environment and the heat generated by this coupling cause the sample to combust. During combustion, carbon-bearing elements are reduced, releasing the carbon, which immediately binds with the oxygen to form CO and CO2, the majority being CO2. Carbon is measured as carbon dioxide in the IR cell as gases flow through the IR cells. Carbon dioxide absorbs IR energy at a precise wavelength within the IR spectrum. Energy from the IR source is absorbed as the gas passes through the cell, preventing it from reaching the IR detector. All other IR energy is prevented from reaching the IR detector by a narrow bandpass filter. Because of the filter, the absorption of IR energy can be attributed only to carbon dioxide (CO2). The concentration of CO2 is detected as a reduction in the level of energy at the detector. The analysis is performed using ELTRA Instruments.

AnalysisMethodReporting Limit
4F-C GraphiticIR0.05%

Accelerator material is added to a 0.2g sample. The inductive elements of the sample and accelerator couple with the high frequency field of the induction furnace. The pure oxygen environment and the heat generated by this coupling cause the sample to combust. During combustion, carbon-bearing elements are reduced, releasing the carbon, which immediately binds with the oxygen to form CO and CO2, the majority being CO2. A small amount of carbon monoxide is converted to carbon dioxide in the catalytic heater assembly. Sulphur-bearing elements are reduced, releasing sulphur, which binds with oxygen to form SO2. Carbon is measured as carbon dioxide in the IR cell as gases flow through the IR cells, and sulphur is measured as sulphur dioxide in the infrared cell. Both carbon dioxide and sulphur dioxide absorb IR energy at precise wavelengths within the IR spectrum. Energy from the IR source is absorbed as the gas passes through the cell, preventing it from reaching the IR detector. All other IR energy is prevented from reaching the IR detector by a narrow bandpass filter. Because of the filter, the absorption of IR energy can be attributed only to carbon dioxide (CO2) or sulphur dioxide (SO2). The concentration of CO2 and SO2 are each detected as a reduction in the level of energy at the individual detectors. The analysis is performed using ELTRA Instruments.

AnalysisMethodReporting Limit
Total CIR0.01%
Total SIR0.01%

Accelerator material is added to a 0.2 g sample. The inductive elements of the sample and accelerator couple with the high frequency field of the induction furnace. The pure oxygen environment and the heat generated by this coupling cause the sample to combust. During combustion, sulphur-bearing elements are reduced, releasing sulphur, which binds with oxygen to form SO2. Sulphur is measured as sulphur dioxide in the infrared cell. ELTRA instruments are used for analysis.

Sulphide sulphur is calculated from the difference between measurements at 550 oC and 1450 oC using combustion/IR, pyrolysis loss sulphur as described in ASTM E1915.
An interpretation of the calculated sulphide value must be made in reference to the mineralogy of the sample.
According to ASTM E1915 in regards to sulphide sulphur, “In the absence of sulphate forms of sulphur, total sulphur may be used to estimate the sulphide sulphur concentration. The pyrolysis loss sulphur may be the best estimate of sulphide sulphur, particularly where the acid generation potential due to iron sulphides is desired. The nitric acid loss method may be appropriate where the sulphide forms are primarily pyrite and marcasite and pyrrhotite is absent, since pyrrhotite may react with acid. The sodium carbonate residual sulphur method is most appropriate where the concentrations of metal sulphide minerals in addition to iron are desired in the absence of barite, alunite, jarosites, orpiment and realgar.”
Sulphide S = Total S – Measured SSO4

A 0.2g sample is first combusted in a resistance furnace at 550 °C in a pure oxygen environment to remove sulphide sulphur, although this is dependent on mineralogy (see 4F – Sulphide method description and below from ASTM). A catalyst is added to the sample and the temperature of the resistance furnace is increased to 1450 °C. During combustion, sulphur-bearing elements are reduced, releasing sulphur, which binds with oxygen to form SO2. Sulphur is measured as a SO2 in the infrared cell. ELTRA instruments are used for analysis.

According to ASTM E1915 in regards to sulphate sulphur, “In the absence of sulphide forms of sulphur, total sulphur may be used to estimate the sulphate sulphur concentration. The pyrolysis residual sulphur may be the best estimate of sulphate sulphur, in the presence of barite, alunite, jarosites, since these sulphate forms are not dissolved by sodium carbonate and in the presence of orpiment and realgar, since these sulphide minerals are soluble in sodium carbonate. The sodium carbonate sulphur loss may be the best estimate of sulphate sulphur in the presence of metal sulphide minerals other than iron, which may not be lost by pyrolysis and the absence of barite, alunite, jarosites, orpiment and realgar. ”

AnalysisMethodDetection Limit
SO4Infrared0.3%

0.2 g sample is thermally decomposed in a resistance furnace in a pure nitrogen environment at 1000 °C, using an ELTRA instrument, directly releasing CO2. H2O is removed in a moisture trap prior to the detection of carbon dioxide in the IR cell. Carbon dioxide absorbs IR energy at a precise wavelength within the IR spectrum. Energy from the IR source is absorbed as the gas passes through the cell, preventing it from reaching the IR detector. All other IR energy is prevented from reaching the IR detector by a narrow bandpass filter. Because of the filter, the absorption of IR energy can be attributed only to carbon dioxide (CO2). The concentration of CO2 is detected as a reduction in the level of energy at the detector.

 

AnalysisMethodDetection Limit
CO2Infrared0.01%

The pre-ignited crucible is weighed before adding a 2g sample to the crucible. After addition of samples, the crucibles are weighed prior to combustion at 450˚C for four hours. After cooling and in a moisture controlled environment, samples are re-weighed to determine the loss of weight from the sample upon combustion. The % LOI at 450˚C is reported. Sample duplicates are performed every 20th sample and reference material are weighed and reported with each tray of samples. An in-house control is run every 30 samples. Reference material is run every 70 samples. After every 15 samples, a laboratory duplicate is analyzed.
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