Quantification of polybrominated diphenyl ethers by means of GC-ICP-MS

Trace and ultra-trace elemental analysis is most often based on the use of inductively coupled plasma-mass spectrometry (ICP-MS). The inductively coupled plasma (ICP) is a powerful and robust atomizer and ionization source that due to its high temperature (>6000 K) destroys molecules nearly quantitatively. On one side, this is a disadvantage with respect to molecular information that is totally lost. On the other side this is releasing the elements from the compounds irrespectively of their structure, allowing for compound-independent calibration (CIC). Using CIC, compounds can be quantified by using one of their elements as target analytes without having a standard for each compound. Also, the ICP is relatively robust against matrix effects influencing the ion yield. This opens the possibility to quantify compounds in real samples by using one compound with the same target element as calibrant. However, since the molecular information is lost in the ICP, compounds must be separated before entering the ICP. Such can be done by hyphenating the ICP-MS with a separation module such as gas chromatography (GC) or high-performance liquid chromatography (HPLC).

A Chinese group of researchers investigated whether CIC was applicable for the quantification of polybrominated diphenyl ethers (PBDEs) by using GC-ICP-MS.

PBDEs are organobromine compounds used as flame retardants. The family of PBDEs consists of 209 possible substances, which are called congeners (PBDE = C₁₂H_(10−x)Br_xO (x = 1, 2, ..., 10 = m + n)). The number of isomers for mono-, di-, tri-, tetra-, penta-, hexa-, hepta-, octa-, nona-, and decabromodiphenyl ethers are 3, 12, 24, 42, 46, 42, 24, 12, 3 and 1, respectively.

The researchers tested the influence of the matrix, the GC  conditions and parameters of sample introduction on the response of 11 PBDEs.  The researchers found that under optimized conditions using pulsed splitless injection, the elemental response of bromine of each PBDE becomes very close to each other, alloying CIC at least for tri- to hepta-brominated compounds. The elemental response of bromine in PBDEs decreases with increasing boiling point because the analyte is not completely transferred to the ICP from the GC system.

When analysing real samples such as fish tissue, a pronounced matrix effect reduced the elemental response for bromine to about 68 to 98 % related to the reference standard. However, this effect could be reduced to 99-106% by using an isomer for calibration.   

The original study:

Chi Zhang, Xiuqin Li, Yanling Chen, Chao Wei, Xiaomin Li, Qinghe Zhang, The compound-independent calibration of polybrominated diphenylethers isomers using gas chromatography-inductively coupled plasma mass spectrometry, J. Chromatogr. A, 1576 (2018) 120-130. DOI: 10.1016/j.chroma.2018.09.035

Agilent 8800 Triple Quad ICP-MS

Agilent GC 7890 B

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May 14, 2017: Multielement speciation analysis

last time modified: September 22, 2024