GC DERIVATIZATION REAGENTS

Transcription

1 G DERIVATIZATI REAGETS

2 DERIVATIZATI Derivatization Derivatization is primarily performed to modify an analyte s functionality in order to enable chromatographic separations. For more than 30 years, Regis has been a leader in the manufacture of highly pure derivatization reagents for gas chromatography. The formation of chemical derivatives to facilitate meaningful analysis has long been a common practice in gas chromatography. For the analytical chemist, judicious use of derivatization can be the key to unlocking and simplifying a great many complex and perplexing separation problems. Derivatization, accomplished through alteration of functional groups, provides: Increased sample volatility Improved selectivity and chromatographic efficiency Enhanced detectability Additional procedures and references are available on our Web site at: 54

3 GAS RMTGRAPY (G) DERIVATIZATI Silylation Sample volatility or thermal stability is crucial in G applications. If a sample does not possess these important characteristics, G analysis is highly unproductive. Derivatization techniques have been developed to address these issues to insure successful separations. In G Derivatization, replacement of active hydrogen in functional groups, such as -, -, -, and -S, is the primary area of concern and is accomplished through either silylation, acylation or alkylation. Silylation is the most widely used derivatization procedure for sample analysis by G. Silylation reagents are popular because they are easy to use and readily form derivatives. In silylation, an active hydrogen is replaced by an alkylsilyl group, such as trimethylsilyl (TMS) or t-butyldimethylsilyl (t-bdms). ompared to their parent compounds, silyl derivatives are more volatile, less polar, and more thermally stable. As a result, G separation is improved and detection is enhanced. Silylation reagents are generally moisture sensitive, requiring them to be sealed under nitrogen to prevent deactivation. The derivatives of TMS reagents are also moisture sensitive. In response to this difficulty, t-bdms reagents were introduced, which enabled the formation of derivatives 10,000 times more stable to hydrolysis than the TMS ethers. Both TMS and t-bdms reagents are suitable for a wide variety of compounds, offer excellent thermal stability and can be used in a variety of G conditions and applications. Analysis by the popular combination of gas chromatography and mass spectrometry (GS/MS) often requires special sample derivatization. Particularly effective in these applications are MTBSTFA and deutero-mtbstfa-d. Acylation Acylation reagents offer the same types of advantages available from silylation reagents: creating less polar, more volatile derivatives. owever, in comparison to silylating reagents, the acylating reagents more readily target highly polar, multi-functional compounds, such as carbohydrates and amino acids. In addition, acylating reagents provide the distinct advantage of introducing electroncapturing groups, thus enhancing detectability during analysis. Generally, these reagents are available as acid anhydrides, acyl derivatives, or acyl halides. The acyl halides and acyl derivatives are highly reactive and are suitable for use where steric hindrance may be a factor. Acid anhydrides are supplied in a number of fluorinated configurations, which improve detection. These fluorinated anhydride derivatives are used primarily for Electron apture Detection (ED), but can also be used for Flame Ionization Detection (FID). Fluorinated anhydrides are often used in derivatizing samples to confirm drugs of abuse. Despite the special utility of these reagents, their acidic nature requires that any excess or byproducts be removed prior to analysis to prevent deterioration of the column. 55

4 GAS RMTGRAPY (G) DERIVATIZATI Alkylation As with other derivatization reagents, alkylation reagents reduce molecular polarity by replacing active hydrogens with an alkyl group. These reagents are used to modify compounds having acidic hydrogens, such as carboxylic acids and phenols. Alkylation reagents can be used alone to form esters, ethers, and amides or they can be used in conjunction with acylation or silylation reagents. A two-step approach is commonly used in the derivatization of amino acids, where multiple functional groups on these compounds may necessitate protection during derivatization. Due to the availability of reagents and their ease of use, esterification (the reaction of an acid with an alcohol in the presence of a catalyst to form an ester) is the most popular method of alkylation. Alkylation reagents are available in several configurations that enable the formation of a variety of esters. Alkyl esters are stable, and can be formed quickly and quantitatively. By altering the length of the substituted alkyl group, retention of the derivative can be varied. In addition to the formation of simple esters, alkylation reagents can be used in extractive procedures where biological matrices may be present. G hiral Derivatization G analysis of enantiomeric compounds on nonracemic or achiral stationary phases requires the use of enantiopure derivatization reagents. These reagents generally target one specific functional group to produce diastereomers of each of the enantiomeric analytes. From the resulting chromatograms, calculations are conducted to determine the enantiomeric concentration of the analyte. 56

5 GUIDE T G DERIVATIZATI METDS/FUTIAL GRUPS G Derivatization Method Functional Group Silylation Acylation Alkylation Active ydrogens BSA, BSTFA, BSTFA/TMS, PFP/PFPA DMF Dialkylacetals, Deriva-Sil, ydrox-sil, TB MSTFA, MTBSTFA, TMSI arboxylic Acids BSTFA, ydrox-sil onc., PFP/PFPA BF3/Methanol, MTBSTFA, TMSI BF3/n-Butanol, DMF Dialkylacetals, TB Alcohols and Phenols: BSA, BSTFA/TMS, FBI, Fluorinated anhydrides DMF Dialkylacetals, unhindered and MDS, MTBSTFA/t-BDMS (FBA, PFPA, TFAA), PFB-Br/TBA--S4, moderately hindered MBTFA, MF* TB Alcohols and Phenols: BSTFA/TMS, Deriva-Sil, Fluorinated anhydrides DMF Dialkylacetals, highly hindered Deriva-Sil onc.(fba, PFPA, TFAA), PFB-Br/TBA--S4, FBI, PFBl TB Amines: BSTFA, MTBSTFA/t-BDMS Fluorinated anhydrides DMF Dialkylacetals, primary and secondary (FBA, PFPA, TFAA), FBI, TB MBTFA, PFBl, TP* Amides BSA, BSTFA, BSTFA/TMS, FBI DMF Dialkylacetals, Deriva-Sil onc.tb Amino Acids BSTFA, TMSI FBI (+ Silylation) DMF Dialkylacetals, TB atecholamines TMSI Fluorinated anhydrides (FBA, PFPA, TFAA), FBI arbohydrates and Sugars MDS, ydrox-sil AQ, TMSI MBTFA Inorganic Anions BSTFA, MTBSTFA itrosamines FBA Sulfonamides BSTFA Fluorinated anhydrides DMF Dialkylacetals, (FBA, PFPA, TFAA) PFB-Br/TBA--S4 Derivatization reagents are listed *For hiral Analysis Source: Knapp, D.R. andbook of Analytical in alphabetical order, not in order Derivatization Reactions; John Wiley and Sons: of preference. ew York,

6 SILYLATI REAGETS BSA,-Bis(trimethylsilyl)acetamide Forms highly stable TMS derivatives with most organic functional groups under mild reaction conditions. BSA 10 x 1 gm x 5 gm gm gm TMS + Y R TMS Y R + 3 TMS 3 TMS TMS = Si( 3 ) 3 Y =, S,, R 1, BSTFA-Regisil BSTFA +TMS (1%, 10%),-Bis(trimethylsilyl)trifluoroacetamide Reacts faster and more completely than BSA, due to presence of trifluoroacetyl group. The high volatility of BSTFA and its byproducts results in separation of early eluting peaks. ighly volatile and stable products result in low detector noise and fouling. Excellent solubility. Addition of TMS catalyzes reactions of hindered functional groups in secondary alcohols and amines. Regisil R-1 10 x 1 gm (BSTFA) 50 x 1 gm x 5 gm gm gm Regisil R-2 10 x 1 gm (BSTFA) +1% TMS 50 x 1 gm x 5 gm gm gm Regisil R-3 10 x 1 gm (BSTFA) +10% TMS 4 x 5 gm gm gm TMS + F 3 TMS TMS = Si( 3 ) 3 Y R TMS Y R + F 3 TMS Y =, S,, R 1, MDS examethyldisilazane Weak TMS donor, used for silylation of carbohydrates. Used as mixture with pyridine and trifluoroacetic acid. MDS 25 gm gm Si Si Y R 3 Si Y R Si Y =, S,, R 1, 3 3 MSTFA -Methyltrimethylsilyltrifluoroacetamide Most volatile of the TMS-acetamides. Useful in the analysis of volatile trace materials. MSTFA 10 x 1 gm gm gm gm F TMS TMS = Si( 3 ) 3 Y R TMS Y R + F 3 Y =, S,, R 1, 3 Regisil is a registered trademark of Regis Technologies, Inc. Product information and applications are available online at: 58

7 SILYLATI REAGETS MTBSTFA MTBSTFA + 1% t-bdms -Methyl--(t-butyldimethylsilyl)trifluoroacetamide Replaces active hydrogens to form t-bdms derivatives. Derivatization is usually complete upon dissolution with this exceptionally strong, yet mild silylating reagent. MTBSTFA derivatives are 10 4 times more stable to hydrolysis than their corresponding TMS derivatives. Produces easily interpreted mass spectra for G/MS. Addition of t-bdms catalyzes reactions of hindered alcohols and amines. MTBSTFA 5 x 1 gm (+1% t-bdms) 10 x 1 gm x 5 gm gm MTBSTFA 5 x 1 gm (no t-bdms) 2 x 5 gm gm Si F 3 + Y R Y =, S,, R 1, Si Y R F 3 TMS Trimethylchlorosilane Used as a catalyst to increase reactivity of other silylation reagents. TMS 25 gm gm Si 3 l + Y R 3 Si Y =, S,, R Y R TMSI Trimethylsilylimidazole Potent, selective TMS donor that reacts with alcohols and phenols but not amines or amides. Derivatizes wet sugar samples, hindered hydroxyl groups in steroids, and amino acids in fluorinated acylation reagents. Used in the preparation of dual perfluoroacyl and TMS derivatives. TMSI 10 x 1 gm gm gm Si 3 + R 3 Si 3 3 R + SILYLATI FRMULATIS Deriva-Sil BSTFA:TMS:TMSI:Pyridine (3:2:3:10) formulation. Derivatizes sterically-hindered compounds. Reacts with carbohydrates, hydroxy- and keto-steroids, fatty acids, and some amines and amides. Derivatizations are complete in minutes. Deriva-Sil 10 x 1 ml BSTFA:TMS: 25 ml TMSI:Pyridine (3:2:3:10) Deriva-Sil oncentrate BSTFA:TMS:TMSI (3:2:3) concentrate formulation. Used for applications where pyridine is undesirable (i.e., 3-ketosteroids). Deriva-Sil oncentrate 25 ml BSTFA:TMS:TMSI (3:2:3) Product information and applications are available online at: 59

8 SILYLATI FRMULATIS ydrox-sil MDS:TMS:Pyridine (2:1:10) formulation for one-step derivatizations. Fast formation of the TMS derivatives of organic acids, unhindered alcohols and phenols, and some amines. ydrox-sil Reagent 10 x 1 ml MDS:TMS:Pyridine 25 ml (2:1:10) ydrox-sil AQ TMSI:Pyridine (21%w/v) formulation. Forms TMS derivatives of hydroxyl and polyhydroxyl compounds in the presence of water. ydrox-sil AQ 10 x 1 ml TMSI:Pyridine 25 ml (21% w/v) ydrox-sil oncentrate MDS:TMS (2:1) concentrate formulation. Suited for applications where pyridine in ydrox-sil is undesirable. ydrox-sil oncentrate 25 ml MDS:TMS (2:1) AYLATI REAGETS Fluorinated Anhydrides: FBA/PFPA/TFAA eptafluorobutyric Anhydride/Pentafluoropropionic Anhydride/Trifluoroacetic Anhydride Most commonly used for ED. Reacts with alcohols, amines, and phenols. Bases such as triethylamine and trimethylamine can be added to promote reactivity. Frequently used for the confirmation of drugs of abuse. FBA derivatives are the most sensitive to ED. PFPA derivatives require the lowest analysis temperatures. TFAA is the most reactive and volatile of the anhydrides. FBA PFPA FBA 10 x 1 gm gm PFPA 10 x 1 gm gm gm TFAA 10 x 1 gm gm F 7 2 F 5 3 F 7 + Y R 3 F 7 Y R + 3 F 7 2 F 5 + Y R 2 F 5 Y R + 2 F 5 TFAA F 3 F 3 + Y R F 3 Y R + F 3 Y =,, R 1 FBI eptafluorobutyrylimidazole Readily forms derivatives with phenols, alcohols and amines suitable for ED. Reactions are fast and mild. Imidazole is not acidic, so no decomposition or corrosion occurs on columns. FBI 5 x 1 gm gm F 7 + Y R 3 F 7 Y R + Y =,, R 1 60

9 AYLATI REAGETS MBTFA -Methyl--bis(trifluoroacetamide) Reacts rapidly under mild conditions with primary and secondary amines. Reacts more slowly with alcohols, phenols, and thiols. Works well in the analysis of sugars. MBTFA 10 x 1 gm gm gm gm F 3 F 3 + Y R F 3 Y R + 3 F 3 3 Y =, S,, R 1 PFP 2,2,3,3,3-Pentafluoropropanol Used in combination with PFPA to make derivatives of the most common functional groups, especially polyfunctional bio-organic compounds. Formed derivatives are highly suitable for ED. PFP 5 gm gm R 1 R 1 2 F PFPA 2 F 5 2 R 2 R 1, R 2 =, Alk, Ar R F 5 DERIVATIZATI GRADE SLVETS Derivatization Grade Solvents igh purity reagents packaged under nitrogen. Sealed with Teflon -coated septa, allowing easy access to sample without exposure to moisture and oxygen. Acetonitrile 2 x 25 ml Dimethylformamide 2 x 25 ml Pyridine 2 x 25 ml Tetrahydrofuran 2 x 25 ml G IRAL AD SPEIALTY DERIVATIZATI REAGETS TP -Trifluoroacetyl-L-Prolyl hloride ouples with amines to form diastereomers which can be separated on G columns. Provides sample volatility. Used for confirmation of drugs of abuse testing. TP 25 ml F 3 l + R 1 2 R 2 R 3 R 1, R 2, R 3 =, Alk, Ar F 3 R 1 R 2 R 3 MF (1R, 2S, 5R)-(-)-Menthylchloroformate Resolves enantioenriched alcohols. MF 25 ml l + R 1 R 2 R 3 R 1, R 2, R 3 =, Alk, Ar 3 3 R 1 R 2 R 3 Teflon is a registered trademark of DuPont ompany. 61

10 G IRAL AD SPEIALTY DERIVATIZATI REAGETS FIP 1,1,1,3,3,3-exafluoro-2-Propanol Esterification reagent for the determination of aromatic acids in tissue by G and electron capture detection. FIP 10 gm gm x 25 gm gm L in n-butanol Most commonly used for rapid diagnosis of neonatal blood spots by Tandem Mass Spectrometry. 3.0 L in n-butanol 4 x 25 ml ml ml ol-treet Silylating mixture designed for conditioning gas chromatography columns. Eliminates peak tailing, peak broadening and residues which may reduce column efficiency. ot to be used with any hydrogen bonding stationary phases such as ARBWAX or phases with active hydrogen sites. ol-treet 10 x 1 ml x 5 ml Glas-Treet Used to deactivate active sites found in glassware, chromatography columns, and glass wool. Does not coat glass; renders it inactive chemically. Glas-Treet 100 ml ARBWAX is a registered trademark of Union arbide orp. For additional information on G Derivatization Reagents, check our Web site at contact Regis directly at: (800) ext. 649 (847) ext us at: sales@registech.com. 62