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Background Volatile organic compounds (VOCs) in exhaled breath are closely associated with respiratory diseases and are linked to various metabolic reactions in the human body. A quantitative analytical method can provide technical support for studying VOCs related to various diseases. Objective To establish a thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) method for the determination of 27 VOCs in exhaled breath. Methods VOCs in exhaled breath were collected using a Bio-VOC sampler and enriched with Tenax TA thermal desorption tubes before TD-GC-MS analysis. Standards were collected using thermal desorption tubes and optimized for thermal desorption conditions as well as chromatographic and mass spectrometric conditions: The separation of the 27 VOCs was achieved by an optimized temperature program, the improvement of sensitivity by optimizing quantitative ions, and the increase of VOCs desorption efficiency by optimizing thermal desorption time and temperature. Limit of detection, limit of quantification, accuracy, precision, and stability of the proposed method were investigated by spiking with a blank gas bag, and exhaled breath samples from 20 healthy individuals were collected for an application study of the proposed method. Results The thermal desorption temperature was 280 ℃, and desorption time was 6 min. A VF-624ms chromatographic column was selected for the separation of target substances. The initial temperature of heating program was 35 ℃, maintained for 1 min, and then increased to 100 ℃ at a heating rate of 3 ℃·min−1 for 1 min, followed by increasing to 210 ℃ at a heating rate of 28 ℃·min−1 for 5 min. A quantitative analysis was conducted with a single ion monitoring (SIM) mode. Under these conditions, the 27 VOCs showed good linear relationships in their respective concentration ranges and the correlation coefficients were higher than 0.9990. The limits of detection of the method were in the range of 0.01-0.13 nmol·mol−1, the limits of quantification were in the range of 0.02-0.44 nmol·mol−1, and the spiked recoveries were in the range of 80.1%-120.5%, with intra-batch and inter-batch precision ≤ 18.8% and 17.9% respectively. All substances can be stored at room temperature (23-28 °C) for 7 d and at 4 °C for 14 d. The proposed method was applied to exhaled breath samples from 20 subjects with detection rates≥ 80% (except for trans-2-pentene and decane) and a concentration range of 0.00-465.50 nmol·mol−1. Conclusion The established TD-GC-MS method for quantification of VOCs in exhaled breath is characterized by high sensitivity and good accuracy, and is suitable for quantitative determination of VOCs in exhaled breath, which can provide technical support for the study of exhaled breath VOCs.
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Objective@#To develop a rapid detection method for 21 elements in urine with inductively coupled plasma mass spectrometry (ICP-MS) .@*Methods@#The urine samples were directly diluted 20 times by 1% HNO3, and detected by ICP-MS, Indium, Yttrium, and Lutecium were used as on-line internal standard. Fe was analyzed by Dynamic Reaction Cell (DRC) mode, As, Cr, V and Zn were analyzed by collision cell technology (CCT) mode, and Be, Mn, Ni, Cd, Sn, Bi, Pb, Re, Sb, W, Li, Cu, Se, Sr, Mo were analyzed by standard mode. Dynamic band-pass tuning (DBT) was used to eliminate interference for Fe.@*Results@#All the elements have good linearity in their determination range, with the correlation coefficient r>0.999 5. The limits of detection of the 21 elements were in the range of 0.017-11.14 μg/L. The inter-precision (relative standard deviation, RSD) was less than 9.96%, and the intra-precision was less than 13.90% (except As RSD<18.91%) . The spike recovery of all elements fell within 81.1%-116.4%.@*Conclusion@#The method was proved to be simple, fast, and accurate, and met the needs of testing requirements of large amounts of specimens.