Accurate quantification of creatinine in serum by coupling a measurement standard to extractive electrospray ionization mass spectrometry.

Ming Li,Mengwan Li,Xiang Fang,Keke Huang,Hongmei Li,You Jiang

doi:10.1038/srep19283

Abstract

Ambient ionization (AI) techniques have been widely used in chemistry, medicine, material science, environmental science, forensic science. AI takes advantage of direct desorption/ionization of chemicals in raw samples under ambient environmental conditions with minimal or no sample preparation. However, its quantitative accuracy is restricted by matrix effects during the ionization process. To improve the quantitative accuracy of AI, a matrix reference material, which is a particular form of measurement standard, was coupled to an AI technique in this study. Consequently the analyte concentration in a complex matrix can be easily quantified with high accuracy. As a demonstration, this novel method was applied for the accurate quantification of creatinine in serum by using extractive electrospray ionization (EESI) mass spectrometry. Over the concentration range investigated (0.166 ~ 1.617 μg/mL), a calibration curve was obtained with a satisfactory linearity (R2 = 0.994), and acceptable relative standard deviations (RSD) of 4.6 ~ 8.0% (n = 6). Finally, the creatinine concentration value of a serum sample was determined to be 36.18 ± 1.08 μg/mL, which is in excellent agreement with the certified value of 35.16 ± 0.39 μg/mL.

Highlights

That samples have high complex matrix and high quantitative accuracy is required[32]
Sodium ion adducts are very common in MS36, and sodiated creatinine was observed in ambient ionization mass spectrometry such as DESI19, EESI30, and contactless atmospheric pressure ionization[37]
Matrix effects are a current obstacle on the quantitative analysis of ambient mass spectrometry because of ion suppression, and distribution of ion current between protonated and sodiated molecules

Summary

Introduction

That samples have high complex matrix and high quantitative accuracy is required[32]. A standard addition method or/and isotope dilution MS were coupled to ambient ionization technique to improve the analytical accuracy[33,34]. In this case, samples were prepared by spiking a series of stock solutions before being analyzed. At least five spiked samples had to be prepared, and at least five MS analysis had to be performed[33,34]. It is still tedious, time- and cost-consuming to prepare and to analyse the spiked samples, especially for the high throughput analysis.

Methods

Results

Conclusion