Multicollector Inductively Coupled Plasma–Mass
Spectrometry with 1013 Ω Faraday Cup Amplifiers for
Ultrasensitive Mg Isotopic Analysis of Cerebrospinal Fluid Microsamples
posted on 2020-11-23, 13:38authored byRosa Grigoryan, Marta Costas-Rodríguez, Patrick Santens, Frank Vanhaecke
Magnesium
isotopic analysis of cerebrospinal fluid (CSF) is a potentially
interesting approach for studies on neurodegeneration. However, this
type of analysis is challenging because of the invasiveness of the
sampling and small sample volume. In this work, a novel analytical
method was developed for ultrasensitive Mg isotopic analysis of CSF
microsamples via multicollector inductively coupled
plasma–mass spectrometry (MC-ICP-MS) using high-gain 1013 Ω Faraday cup amplifiers. The intermediate and internal
errors on the δ26Mg value were improved up to fourfold
using 1013 Ω resistors for the monitoring of both
the 24Mg and 26Mg isotopes and up to twofold
using a 1011 Ω resistor for the most abundant 24Mg isotope and a 1013 Ω resistor for the 26Mg isotope. Magnesium isotope ratios measured at a concentration
level of 7–10 μg L–1 were in good agreement
with those obtained using the conventional method at a concentration
level of 150 μg L–1. The expanded uncertainty
for the quality control CSF material obtained at the ultratrace level
was ±0.16‰. Ultrasensitive Mg isotopic analysis was carried
out for CSF from hydrocephalus patients using only 5 μL of sample.
δMg values thus obtained were not significantly different from
those obtained using the conventional method using a sample volume
of 400 μL instead (p ≤ 0.05). The Mg
isotopic composition of the CSF from hydrocephalus patients ranged
between −0.65 and 0.30‰, with a mean δ26Mg value of −0.14 ± 0.27‰.