目的 從水分活度（water activity，A_w）和水分子流動(dòng)性2個(gè)角度，考察中藥飲片全蝎的水分吸附特性和熱力學(xué)性質(zhì)，為其干燥和儲(chǔ)存提供指導(dǎo)。方法 通過(guò)靜態(tài)稱重法測(cè)定全蝎飲片在25、35、45 ℃下的吸附等溫線，采用6種常用的水分吸附數(shù)學(xué)模型（GAB、Peleg、BET、Smith、Henderson和Halsey）擬合試驗(yàn)數(shù)據(jù)，確定最佳模型，研究其吸附熱力學(xué)性質(zhì)，并結(jié)合低場(chǎng)核磁共振（low-field nuclear magnetic resonance，LF-NMR）技術(shù)對(duì)吸濕平衡狀態(tài)下全蝎飲片中各狀態(tài)的水分進(jìn)行表征，闡明其吸濕特性。結(jié)果GAB模型為全蝎飲片吸附的最佳擬合模型，在25、35、45 ℃條件下其相對(duì)安全含水量分別為22.72%、22.35%和23.06%，絕對(duì)安全含水量分別為13.21%、12.27%和11.71%。全蝎飲片的凈等量吸附熱（net equivalent adsorption，q_st）和微分熵（differential entropy，S_d）都隨著含水量的升高而降低。吉布斯自由能（Gibbs free energy，ΔG）為負(fù)，說(shuō)明吸濕過(guò)程是自發(fā)的放熱反應(yīng)。樣品在不同溫度吸濕平衡時(shí)，T₂₁、T₂₂、T₂₃、T₂₄均代表樣品水分子中質(zhì)子的峰，其中T₂₁、T₂₂和T₂₃還包含了飲片中醛類、酯類等親脂性成分中質(zhì)子的信號(hào)。T₂₁隨著A_w的升高不斷右移轉(zhuǎn)化為T₂₂、T₂₃、T₂₄，說(shuō)明飲片中水分子流動(dòng)性逐漸增大，存在結(jié)合水向自由水轉(zhuǎn)化。當(dāng)A_w＜0.6時(shí)結(jié)合水（A₂₁＋A₂₂）增加趨勢(shì)并不明顯，但當(dāng)A_w＞0.6時(shí)結(jié)合水（A₂₁＋A₂₂）大幅度增加。結(jié)論 結(jié)合吸附等溫線、吸附熱力學(xué)性質(zhì)和LF-NMR技術(shù)，建議以12%作為全蝎飲片的干燥終點(diǎn)含水量，研究結(jié)果可為其他中藥飲片安全儲(chǔ)藏含水量的確定提供參考。

Objective The water adsorption characteristics and thermodynamic properties of Scorpio were investigated from the perspectives of water activity (A_w) and water molecular fluidity, which provided guidance for their drying and storage. Methods The adsorption isotherms of Scorpio at 25, 35, and 45 ℃ were determined by static weighing method. Six commonly used moisture adsorption models (GAB, Peleg, BET, Smith, Henderson and Halsey) were used to fit the experimental data to determine the best model. The thermodynamic properties of the adsorption were studied. Combined with low-field nuclear magnetic resonance (LF-NMR), the moisture of each state in the Scorpio under the moisture absorption equilibrium state was characterized to clarify its moisture absorption characteristics. Results The GAB model was the best fitting model for Scorpio adsorption. At 25, 35, and 45 ℃, the relative safe water content was 22.72%, 22.35%, and 23.06%, and the absolute safe water content was 13.21%, 12.27%, and 11.71%, respectively. The net isosteric heat of sorption (q_st) and differential entropy (S_d) of Scorpio decreased with the increase of water content. The Gibbs free energy (ΔG) is negative, indicating that the moisture absorption process is a spontaneous exothermic reaction. When the samples were in moisture absorption equilibrium at different temperatures, T₂₁, T₂₂, T₂₃ and T₂₄ all represented the peaks of hydrogen protons in the water molecules of the samples, among which T₂₁, T₂₂ and T₂₃ also contained the signals of hydrogen protons in lipophilic components such as aldehydes and esters in the decoction pieces. With the increase of A_w, T₂₁ continuously shifted to the right and transformed into T₂₂, T₂₃ and T₂₄, indicating that the fluidity of water molecules in the decoction pieces gradually increased, and there was a conversion from bound water to free water. When A_w < 0.6, bound water (A₂₁ + A₂₂) did not increase significantly, but When A_w > 0.6, bound water (A₂₁ + A₂₂) increased significantly. Conclusion Combined with adsorption isotherms, adsorption thermodynamic properties and LF-NMR technology, it is recommended to use 12% as the drying end point water content of Scorpio. The research results can provide reference for the determination of safe storage water content of other traditional Chinese medicine decoction pieces.

R283.6

國(guó)家自然科學(xué)基金項(xiàng)目（81960715）；國(guó)家自然科學(xué)基金項(xiàng)目（82060715）；江西省重點(diǎn)研發(fā)計(jì)劃項(xiàng)目（20223BBG71001）