Abstract Humic-like substances (HULIS) constitute a significant fraction of the water-soluble organic compounds in the environment and influence many properties of atmospheric aerosols. In this study, three solid phase extraction (SPE) methods that involve the use of hydrophilic/lipophilic balanced (HLB) resin with pure methanol (HLB-M), HLB resin with 2% (v/v) ammonia/methanol (HLB-N), and Bond Elut PPL (Priority PolLutant) resin with methanol (PPL), were compared for the isolation of HULIS from atmospheric aerosols. The HLB-N and PPL methods efficiently recovered Suwannee River fulvic acid (SRFA) and were excellent for quantifying HULIS at low levels in aerosols. All three SPE methods were favorable for the elution of aromatic and strongly UV-absorbing compounds. However, the chemical structures and molecular compositions of the HULIS isolated by the three methods showed some differences. The HULISHLB-N and HULISPPL fractions contained higher concentrations of aliphatic and aromatic C–H groups than did the HULISHLB-M fraction, indicating that relative higher content of weak polar organic species in HULIS fractions isolated by the HLB-N and PPL methods than those isolated by the HLB-M method. Moreover, the HULISHLB-N and HULISPPL were both characterized by having lower relative abundance-weighted modified aromaticity index values and higher concentrations of S-containing compounds than the HULISHLB-M, as indicated by Fourier transform ion cyclotron resonance mass spectrometry. Some N-containing structures were identified only in the HULISHLB-N, suggesting that some of HULIS molecules were changed during the HLB-N treatment. Based on these comparisons of the three methods, we found that the PPL method serves equally good as compared to other two methods, and therefore, one can utilize PPL method also for HULIS isolation and characterization.

中文翻译：

---

用于测量大气颗粒中类腐殖质 (HULIS) 的固相萃取方法比较

摘要 类腐殖质 (HULIS) 是环境中水溶性有机化合物的重要组成部分，并影响大气气溶胶的许多特性。在本研究中，三种固相萃取 (SPE) 方法涉及使用亲水/亲油平衡 (HLB) 树脂与纯甲醇 (HLB-M)、HLB 树脂与 2% (v/v) 氨/甲醇 (HLB- N) 和 Bond Elut PPL（Priority PolLutant）树脂与甲醇 (PPL) 进行比较，以从大气气溶胶中分离 HULIS。HLB-N 和 PPL 方法有效地回收了 Suwannee 河富里酸 (SRFA)，非常适合量化气溶胶中低水平的 HULIS。所有三种 SPE 方法都有利于洗脱芳香族化合物和强紫外吸收化合物。然而，三种方法分离的 HULIS 的化学结构和分子组成存在一定差异。HULISHLB-N 和 HULISPPL 馏分比 HULISHLB-M 馏分含有更高浓度的脂肪族和芳香族 C–H 基团，表明通过 HLB-N 和 PPL 方法分离的 HULIS 馏分中弱极性有机物质的含量相对高于那些HLB-M 法分离。此外，与 HULISHLB-M 相比，HULISHLB-N 和 HULISPPL 均具有较低的相对丰度加权修正芳香性指数值和较高浓度的含硫化合物，如傅立叶变换离子回旋共振质谱所示。一些含氮结构仅在 HULISHLB-N 中被识别，表明一些 HULIS 分子在 HLB-N 处理期间发生了变化。基于对这三种方法的这些比较，我们发现 PPL 方法与其他两种方法相比同样好，因此，也可以利用 PPL 方法进行 HULIS 隔离和表征。