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Subcritical water
 
引言

在傳統正相或逆相高效液相層析法中,移動相常需使用大量有機溶劑,如︰正己烷、乙酸乙酯、甲醇、與乙腈等。逆相高效液相層析法所用的沖提液通常是以水與甲醇及乙腈等有機溶劑依需要以不同比例混合而成,甲醇或乙腈加入水中後改變水溶液的極性、黏度和表面張力等特性。極性的下降增加沖提液對中低極性有機物的溶解度,使得這些分析物之滯留因數降低。由於液相層析法對於溶劑的純度要求較高,因此所用有機溶劑的價格也較為昂貴。此外,有機溶劑都具有某些程度的毒性與易燃性,除對環境會造成污染外,也對使用接觸者的健康造成威脅。水的極性及介電常數在超臨界狀態下(T>374 ℃,P>22.1 MPa)均下降,增大其對中極性和非極性有機物的溶解度,在超臨界萃取層析方法中已有應用[1]。由於產生超臨界水的實驗條件比較難以控制,以及超臨界水具有腐蝕性,容易使某些有機化合物分解,使其應用性受到限制。在適度的壓力下,只要使水保持為液體狀,此時液體狀水的極性會隨溫度的變化而改變。將水加熱至沸點以上,臨界點以下,並控制系統壓力使水保持為液態,這種狀態的水被稱為次臨界水(subcritical water),在文獻中也有稱它為超熱水和高溫水[2]。在1994年首次有人採用次臨界水進行次臨界流體萃取研究[3],1997年開始有次臨界水液相層析法的研究報告[4-6]。以次臨界水替代傳統的甲醇-水或乙腈-水等動相體系,不僅減少有機溶劑的使用、降低分析成本、減少環境污染,而且也有特殊的層析功效。

  1. S.B. Hawthorne, Yu Yang and D.J. Miller, “Extraction of Organic Pollutants from Environmental Solids with Sub- and Supercritical Water,” Anal. Chem., 1994, 66, 2912-2920.
  2. Yu Yang, Maya Belghazi, Steven B. Hawthorne, and David J. Miller, “Elution of Organic Solutes from Different Polarity Sorbents Using Subcritical Water conditions,” J. Chromatogr. A, 1998, 810, 149-151.
  3. Steven B, Yu Y. David J, et al. “Extraction of Organic Pollutants from Environmental Solids with Sub- and Supercritical Water,” Anal Chem, 1994, 66, 2912-2920.
  4. Yu Y, Seren B. “Subcritical Water Extraction of Polychlorinated Biphenyls from Soil and Sediment,” Anal Chem, 1995, 67, 4571.
  5. Roger M, Robert J. “Superheated Water as an Eluent for Reversed-phase High-performance Liquid Chromatography,” Journal of Chromatography A, 1997, 785, 49.
  6. Trna MP, Colin FP. “Salvation Characterristics of Pressurized Hot Water and its use in Chromatography,” Anal Common, 1999, 38, 71.
Review
Current Use of Pressurised Liquid Extraction and Subcritical Water Extraction in Environmental Analysis (Journal of Chromatography A, Volume 975, Issue 1, 25 October 2002, Pages 3-29) 2002年pressurised liquid extraction與 subcritical water extraction於環境分析之論文回顧
Sub- and Supercritical Fluid Extraction of Functional Ingredients from Different Natural Sources: Plants, food-by-products, algae and microalgae: A review• (Food Chemistry, Volume 98, Issue 1, 2006, Pages 136-148) subcritical water 應用於天然物萃取
   
Articles
Extraction
Subcritical Water Extraction of Essential Oils from Thymbra Spicata — Food Chemistry, Volume 82, Issue 3, August 2003, Pages 381-386
Coupling Continuous Subcritical Water Extraction, Filtration, Preconcentration, Chromatographic Separation and UV Detection for the Determination of Chlorophenoxy Acid Herbicides in Soils — Journal of Chromatography A, Volume 959, Issues 1-2, 14 June 2002, Pages 25-35
Continuous Subcritical Water Extraction as a Useful Tool for Isolation of Edible Essential Oils — Food Chemistry, Volume 75, Issue 1, October 2001, Pages 109-113
Separation
High-performance Liquid Chromatography at Elevated Temperatures: Examination of Conditions for the Rapid Separation of Large Molecules. — J. Chromatogr. 1988, 435, 1-15
Subcritical Water Chromatography with Flame Ionization Detection — Anal. Chem., 1997, 69(4): 623-627.
Effect of Mobile Phase Additives in Packed-Column Subcritical and Supercritical Fluid Chromatography.Anal. Chem. 1997, 69(3), 409-415.
Superheated Waer as an Eluent for Reversed-phase High-performance Liquid Chromatography. — J. Chromatogr. A 1997, 785, 49.
Salvation Characterristics of Pressurized Hot Water and Its Use in Chromatography.Anal Common, 1999, 38, 71.
Method for Determining the Solubilities of Hydrophobic Organics in Subcritical Water.Anal. Chem. 1998, 70 (8), 1618—1621
High-temperature Liquid Chromatography.J Chromatogr. A 2003, 1000, 743-755
Subcritical Water Extraction Coupled to High-Performance Liquid Chromatography.Anal. Chem. 1999, 71(8), 1491-1495.
Temperature Effect on Peak Width and Column Efficiency in Subcritical Water Chromatography.J. Chromatogr. Sci. 2002, 40(2), 107-112.
Flame Ionization Detection after Splitting the Water Effluent in Subcritical Water Chromatography. — J. Chromatogr. A 2002, 942(1-2), 231-236.
Separation of Polar and Nonpolar Analytes Using Dimethyl Sulfoxide-modified Subcritical Water. Anal. Chim. Acta, 2002, 460(2), 185-191.
Studies on the Long-term Thermal Stability of Stationary Phases in Subcritical Water ChromatographyJ. Chromatogr. A, 2003, 989(1), 55-63.
Off-line Coupling of Subcritical Water Extraction with Subcritical Water Chromatography via a Sorbent Trap and Thermal Desorption.Anal. Chem, 2003, 75(10), 2237-2242.
On-line Coupling of Subcritical Water Extraction with High-performance Liquid Chromatography via Solid-phase Trapping.J. Chromatogr. A, 2000, 873(2), 175-84.
Separation of Nonpolar Analytes Using Methanol-water Mixtures at Elevated Temperatures.Anal. Chim. Acta, 2003, 485(1), 51-55.
Retention Behavior of Phenols, Anilines, and Alkylbenzenes in Liquid Chromatographic Separations Using Subcritical Water as the Mobile Phase.Anal. Chem, 1999, 71(17), 3808-3813.
Comparison of Elution Strength, Column Efficiency, and Peak Symmetry in Subcritical Water Chromatography and Traditional Reversed-phase Liquid Chromatography.Anal. Chim. Acta, 2003, 494(1-2), 157-166.