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Abstract
Cholesterol serves as a biomarker in clinical- and life-sciences. The determination of abnormal levels can indicate several types of human diseases. However, the low polarity of free cholesterol makes it hardly accessible by (nano) electrospray ionization mass spectrometry (nESI-MS). As novel approach, the flexible microtube plasma (FμTP) for post-ionization allows the determination of low-polar compounds like cholesterol in combination with nESI-MS. Focusing on the analytical performance, the activated post-ionization leads to an increased cholesterol signal by a factor of 22. The repeatability and long-term stability could be successful evaluated by using a complex liver extract. Via the method of standard addition, a linear dynamic range of 1.7 orders of magnitude, a minimum detectability of 3.71 mg/L and a high accuracy (deviation: − 8.11 %) is demonstrated proofing the FμTP-nESI-MS as an excellent approach for a derivatization-free determination of cholesterol without the necessity of high-resolution Orbitrap devices or enhanced MS acquisition-methods.
Supplementary materials
Title
Supporting Information
Description
Fig. S1: The long-term measurement of cholesterol at m/z 369.42 over 30 min and 10 microscans by using the nESI-FμTP-mode.
Fig. S2: Residual analysis of the regression of the long term observation. A gaussian fit to the calculated residues is added to the plot and indicates a normal distribution.
Tab. S1: Composition of the calibration series 1. Prepared for the evaluation of the linear dynamic range by the method of standard addition.
Fig. S3: Disproportional decreasing of the intensity of sample No. 7 are generated by droplet forming at the tip of the electrospray emitter.
Tab. S2: Composition of the calibration series 2. Prepared the determination of the accuracy by the method of standard addition
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