Project topics and materials
Get Complete Project Material File(s) Now! »
PERFLUOROACYLANHYDRIDES
Heptafluorobutyric acid anhydride (HFBA) has been used to derivatize the primary amine on tocainide, an antiarrhythmic drug [160]. The derivative yield was 92% in toluene with a reagent concentration of only 0.01% v/v. However, the authors found that an excess of HFBA, and similarly for trifluoro- and propionic acid anhydride [161], degraded the formed derivatives [160]. A combination of HFBA and heptafluorobutanoyl chloride (HFBCl) 2:8 v/v, has been used to derivatize amphetamine-like drugs from urine [162]. A headspace in situ SPME derivatization reaction was used, as the rate at which the water hydrolyzed the reagent was much faster than the rate of the acylation reaction of the amines with the reagent. A glass insert, with 12 holes, containing the derivatizing reagents, was placed in the vial containing the urine sample. The SPME fibre was exposed to the headspace above the glass insert. While the vial was heated, the volatile amphetamine-like drugs diffused into the insert where they were simultaneously derivatized and absorbed by the PDMS SPME fibre. The detection limits of this method were in the range of 0.016–0.193 ng /ml [162].
Carbamate formation
2-(9-anthryl) ethyl chloroformate has been used, in an automated process, as a precolumn derivatization agent for determining amino acids. Both primary and secondary amines were converted to stable carbamate derivatives before being analysed by HPLC. The reaction occurred at room temperature in a buffered aqueous medium, after removal of excess reagent prior to injection. The anthracene chromophore provided lower UV and fluorescence detection limits of 0.5 pmol and 0.06 pmol, respectively, than the better-known 9-fluorenylmethyl chloroformate [168, 169]. For GC analysis, smaller molecular tags are used for carbamate formation, typically the methyl, ethyl and isobutyl chloroformates [112, 169]. Trichloro- and pentafluorobenzyl chloroformates have also been developed for ECD detection [169].
ACYL ACID ANHYDRIDES
Acetic acid anhydride (AAA) is by the far the most popular reagent for derivatizing phenols. The stable methyl ester derivatives form rapidly under aqueous alkaline conditions followed by extraction into an organic solvent or polymeric sorbent [122, 170].
AAA has been used to derivatize chlorophenols in tap water for analysis by plasma atomic emission detector [171], pentachlorophenol in leather using supercritical fluid extraction [172], phenol and methylphenol isomers in soil [173], bisphenol A in river water using liquid phase microextraction (LPME) [174] and alkylphenols in water by FIA and membrane introduction mass spectrometry [175]. There are several applications of in situ derivatization using AAA. These use stir bar sorptive extraction (SBSE) to extract and concentrate the formed derivatives followed by thermal desorption GC/MS analysis. Using this method, the following have been determined; estrone, 17b-estradiol and 17a- ethinylestradiol [55, 176], alkylphenols and bisphenol-A in human urine samples [51] and in river water [54, 177], chlorophenols in river and tap water as well as human urine [178], hydroxy-PAH’s in water [179], phenols in human urine [112], lake and ground water [180]. Detection levels were typically at the ppt level. 17a-Ethinylestradiol was extracted and derivatized by SBSE with AAA and BSTFA to convert both the phenolic and sterically hindered alkyl hydroxyl group. A multishot desorption of 5 stir bars resulted in a detection limit of 0.1 ng/L [181].
For improved detection trifluoroacetic (TFA) [182]-, pentafluoropropionic (PFP) and heptafluorobutyric (HFB) acid anhydrides have frequently been used [122]. Several haloacyl anhydrides were tested for the determination of 21 endocrine disrupting compounds, of which TFAA and HFBA proved most useful [62]. Unlike most other derivatization reactions described in the relevant literature, these reactions all proceeded to completion within 5 min [62].
Estrone, 17b-estradiol and 17a-ethinylestradiol have been concentrated and cleaned from sewage water using SPE. The extract was derivatized with PFPAA and analyzed by GC-MS (SIM). Detection limits were in the range of 5 – 10 ng/L [21, 183]. Estrone, 17b-estradiol, estriol, nonylphenol and bisphenol-A were determined from sediments. After ultrasonic extraction and silica gel fractionation, the extract was derivatized with PFPAA and analyzed by GC-MS (SIM). Detection limits were in the range of 0.1 – 1.5 ng/g [184].
CHAPTER 1 INTRODUCTION
1.1. Organic pollutants and human health
1.2. The role of liquid chromatography – mass spectrometry in pollution analyses
1.3. Gas chromatography-mass spectrometry and the need for derivatization
1.4. Sample enrichment and preparation
1.5. Aim of our study
1.6. Our approach
1.7. Arrangement and presentation
CHAPTER 2 CONCENTRATION TECHNIQUES
2. Introduction
2.1. Adsorption
2.2. Absorption – dissolution of analytes from gases and liquids
2.3. Dynamic and static equilibrium
2.4. Gas and Liquid phase PDMS extraction
2.5. Phase ratio and analyte capacity
2.6. Recovery
CHAPTER 3 DERIVATIZATION
3. Introduction
3.1. Classification
3.2. Derivatization of aldehydes
3.3. Derivatization of amines
3.4. Derivatization of alcohols and phenols
3.5. Derivatization and pre-concentration
3.6. Conclusions
CHAPTER 4 SAMPLE INTRODUCTION
4. Introduction
4.1. GC inlets
4.2. Thermal desorption units
4.3. Thermal modulator array (TMA)
CHAPTER 5 ON-LINE ANALYSIS OF ALDEHYDES AND AMINES USING OPEN TUBULAR AND MULTICHANNEL PDMS TRAPS
5.1. Loading the derivatizing reagent into the PDMS MCT by preparative gas chromatography
5.2. The approach for on-line concentration and derivatization
5.3. Derivatization reaction for “photo-ionization labelling” of amines and aldehydes
5.4. Setup for SPME GC-FID based testing of the PDMS mediated derivatization reactions
5.5. On-line derivatization setup
5.6. Resonance enhanced time-of-flight mass spectrometry (REMPI-TOFMS)
5.7. Experimental
5.8. Results and discussion
5.9. Conclusions
CHAPTER 6 DETERMINING ENDOCRINE DISRUPTORS FROM WATER BY CONCENTRATION AND DERIVATIZATION IN PDMS MULTICHANNEL TRAPS
6.1. Our approach
6.2. Derivatization
6.3. Extraction
6.4. Quantitative thermal desorption
6.5. Sampling
6.6. Experimental
6.7. Results and discussion
6.8. Limitations of this method
6.9. Spiked water samples
6.10. Real water samples
6.11. Conclusion
CHAPTER 7 CONCLUSIONS
7.1. On-line analysis of volatile aldehydes and amines from air using PDMS traps
7.2. Determining endocrine disruptors from water by concentration and derivatization in PDMS traps
REFERENCES
