Trace Element Analysis, Positive Material Identification & More
Instrumental chemistry, also called instrumental analysis or instrumental chemical analysis, provides valuable information about the make-up of a test sample, often with trace element analysis capabilities. Instrumental analysis can provide qualitative results by identifying individual elements or groupings of elements in the sample and/or quantitative information by determining the amount of each included element.
Instrumental Chemistry Results Have Many Applications
- Verification of conformance to a standard or specification (ASME, MIL, ASTM)
- Positive material identification
- Evaluation of raw materials
- Detection of impurities
- Identification of the alloy used to make a specific component
- Trace element analysis
- Determination of moisture content in flux coated wire, ores, ferroalloys and chemical samples
Variety of Analytical Chemistry Techniques
Analytical chemistry is performed with instruments that provide automated and computerized processing and reporting of results including:
- Atomic Emission Spectroscopy
- ICP Analysis (ICP-MS, ICP-AES)
- Positive Material Identification
- Combustion Furnace Method for Sulfur & Carbon Analysis
- Inert Gas Fusion for Oxygen, Hydrogen & Nitrogen Determination
- Moisture Analysis
- FTIR Analysis
Laboratory Testing Inc. offers complete element analysis with quantitative and qualitative results, including trace element analysis performed by ICP spectrometers with detection limits in the “parts per trillion” range for some elements.
The most appropriate method of instrumental analysis often depends on:
- Type of sample
- Quantity of material available for analysis
- Desired result
- Cost constraints
The Instrumental Chemistry Processes
Atomic Emission Spectroscopy
Atomic Emission Spectroscopy (AES) is one of the most useful analytical chemistry techniques for direct analysis of elemental composition in solid metal samples. LTI’s AES spectrometers can analyze all common elements in metal and alloy samples, including soft metals such as tin, lead and zinc. Both qualitative and quantitative information can be reported. Read more about the AES Analysis process.
Inductively Coupled Plasma (ICP) Atomic Emission Spectroscopy (AES) and Mass Spectrometry (MS) analyses are performed at LTI with fully computerized, top-of-the-line spectrometers. ICP-AES is a technique that can detect most of the elements in the periodic table and can determine elemental concentrations of trace to major. Reliable results can be obtained for about 70 elements with detection limits in the parts per billion range. The ICP-MS can determine a range of metals and several non-metals and is highly sensitive and capable of trace multi-element analysis, often at the parts-per-trillion level. Read more about these ICP Analysis processes.
Positive Material Identification
Positive Material Identification is performed at LTI by a nondestructive technique called portable X-ray Fluorescence Spectroscopy. The equipment provides direct analysis of solid metal samples for major elements, thin metal films, and can be used for RoHS screening of metallic and non-metallic samples. An X-ray tube is used to irradiate the sample with a primary beam of X-rays. Some of the X-rays are absorbed by the sample elements causing excitation, then fluorescence occurs as X-rays are emitted with an energy that is characteristic of the element from which it was emitted. The fluorescence X-rays are collimated and directed to an X-ray detector. The energy of each X-ray and number of X-rays at each energy level are recorded. The intensities of these X-rays are compared to values for known standards for positive material identification of the unknown specimen and semi-quantitative information.
Combustion Method for Sulfur and Carbon Analysis
High temperature combustion is used for sulfur and carbon analysis to determine their content in a variety of metal and inorganic materials. The test begins by heating a sample in a high-temperature furnace which is flooded with oxygen, causing the combustion of the carbon and sulfur in the sample. The gases are passed through a series of traps, absorbers and converters to remove interfering elements and to ensure the gases have the proper structure for detection. Infrared detection is used to determine the concentration of the carbon or sulfur. The infrared absorption detector measures the absorption of the infrared wavelengths characteristic of carbon and sulfur. The amount of energy absorbed is related to the amount of the carbon or sulfur in the test sample.Lower detection limits for carbon range from 0.1 to 10 parts per-million with upper detection limits of 2.5 – 3.5 %. Lower detection limits for sulfur range from 1. to 50 parts per-million with upper detection limits of 0.2 – 2.5 %.
Inert Gas Fusion
Inert gas fusion is a quantitative instrumental chemistry technique for determining the concentrations of gases (nitrogen, oxygen, and hydrogen) in ferrous and nonferrous materials. These gases are found in materials as a result of melting processes and subsequent hot and cold working methods. Managing the gas contents at low levels minimizes their adverse effects on the materials’ mechanical properties.
The inert gas method heats the sample to a molten state in a fusion furnace with an inert gas atmosphere and reverses the bonding between the gases and metals, causing the dissociation of the gases. The fusion gases are separated and carried to a detector. An infrared detection system is used at LTI to detect oxygen, and a thermo-conductivity system is used to detect nitrogen and hydrogen.
Moisture analysis reveals the percentage of moisture in a wide variety of inorganic materials including welding flux, ores, ferroalloys and chemical samples. The analyzer uses radio frequency to heat the sample to the specified temperature in order to separate the moisture from the rest of the sample. An infrared detection process quantifies the moisture as compared to a reference material. Moisture is stated as a percentage of the total weight. The analysis is valuable in preventing weld rejection due to porosity and in informing material buyers about the percentage of weight attributed to moisture.
FTIR Analysis or FTIR Spectroscopy can identify organic, polymeric, and some inorganic materials in solid, liquid and powder samples. This method can assess purity, reveal the molecular structure of the sample and identify additives, contaminants and basic type of material if unknown.
Providing Samples for Instrumental Analysis
To save time and money and to assure that the results are as accurate as possible, we ask customers to provide us with as much information as possible about samples submitted for analytical chemistry. The information will help us choose the most appropriate and cost-effective testing methods, and may eliminate the need to run preliminary tests that could delay results and increase costs.
Whenever any of the following information is available, please include it on your purchase order or with your test sample:
- Sample Composition - Since LTI performs analyses on a relatively large number of metal alloys, when a customer asks for the analysis of only one component of the alloy without giving us the approximate composition of the sample, it is possible that errors could result due to unknown interferences. These errors can be related to interference of one of the elements with others in the alloy due to the analytical chemistry method used.
- Standards & Specifications - When testing is performed to determine if a sample conforms to a standard or specification (e.g. ASME, ASTM, MIL), it is important to know the alloy or grade that is being tested because some standards refer to more than one alloy or grade.
To ensure that we receive an adequate sample size to perform the required instrumental analysis, we provide the following guidelines:
- Sample Size
- AES solid samples - 1/8” thick and 1” x 1” square
- AES Analysis for gases – carbon and sulfur (minimum of 2 grams); nitrogen and oxygen (minimum of 1½ grams); hydrogen (minimum of 2 grams)
- ICP Analysis – weight a minimum of 5 grams
Note: For comparison, a dime weighs about 2½ grams and a nickel weighs about 5 grams.
- AMS 4081
- AMS 4083
- ASME Sect. IX
- ASTM A751
- ASTM B328
- ASTM D1976
- ASTM E1019
- ASTM E1086
- ASTM E1251
- ASTM E1252
- ASTM E1409
- ASTM E1447
- ASTM E1476
- ASTM E1508
- ASTM E1613
- ASTM E415
- AWS A4.4 M
- EB 4906 Rev A
- MIL Specifications