Direct multi-elemental analysis of cerebrospinal fluid samples by LA-ICP-MS employing an aerosol local extraction cryogenic ablation cell

A novel method for direct high-throughput analysis of multi-elements in cerebrospinal fluid (CSF) samples by laser ablation inductively coupled plasma mass spectrometry with an aerosol local extraction cryogenic ablation cell (ALEC-LA-ICP-MS) was developed. Microliter-level CSF samples were frozen by a designed cryogenic ablation cell and directly analyzed by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) without time-consuming pretreatment. Compared with the precision obtained at room temperature (20℃), that obtained at low temperature (- 25℃) was significantly improved; the RSDs were reduced from 8.3% (Zn) to 32.6% (Mn) to 2.2% (Pb) to 6.5% (Mn) with six times parallel determination. To meet the analytical requirement of the micro-volume CSF samples, the laminar flow aerosol local extraction strategy was adopted to improve the transmission efficiency of aerosols, and the signal intensity was increased by four times compared with the standard commercial ablation cell. The standard solution with 0.4% bovine serum albumin (BSA) matrix was used as matrix-match external standard, and Rh was added into the samples as internal standard. The limits of detection (LODs) ranged from 0.17 μg·L-1 (Mn) to 8.67 μg·L-1 (Mg). Standard addition recovery experiments and the determination of CRM serum L-1 and L-2 were carried out to validate the accuracy of the method; all results indicated there were excellent accuracy and precision in the proposed method. The matrix-scanning function in the GeoLas software combined with the microwell plate realizes the high-throughput automatic analysis. Twenty-four CSF samples from different patients were determined; the results showed that there might be a correlation between the metal elements in CSF and the diseases, which means that the proposed method has potential in the diagnosis of neurological diseases.

Multicollector Inductively Coupled Plasma-Mass Spectrometry with 1013 Ω Faraday Cup Amplifiers for Ultrasensitive Mg Isotopic Analysis of Cerebrospinal Fluid Microsamples

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‰.