Aldehyde formaldehyde, derivatized

Kovacs-Hadady and Kiss [27] studied the chromatographic characteristics of thia-zolidinecarboxylic acid derivatives, formed by reaction of (i>) and (L)-penicillamine with various substituted benzaldehydes and heterocyclic aldehydes in order to evaluate the aldehydes as derivatizing agents for separation of the penicillamine enantiomers. The TLC method of Martens et al. [28] was used. Transformation to thiazolidine carboxylic acids with benzaldehyde and substituted benzaldehydes was not complete, so formaldehyde is still the preferred reagent for separation of the enantiomers. 

The principal side reaction to epoxide coupling is hydrolysis. Particularly at acid pH values, the epoxide ring can hydrolyze to form adjacent hydroxyls. This diol can be oxidized with periodate to create a terminal aldehyde residue with loss of one molecule of formaldehyde (Chapter 1, Section 4.4). The aldehyde then can be used in reductive amination reactions. The reaction of an epoxide group with an ammonium ion generates a terminal primary amine group that also can be used for further derivatization. 

Aldehydes. The aldehydes studied in this program include acetaldehyde, chloroacetaldehyde, formaldehyde, furfural, crotonalde-hyde, and acrolein. Because of the instability of the aldehydes, they are best collected by derivatizing during sample collection. 

Derivatization is a procedure in which analyte is chemically modified to make it easier to detect or separate. For example, formaldehyde and other aldehydes and ketones in air, breath, or cigarette smoke25 can be trapped and derivatized by passing air through a tiny cartridge containing 0.35 g of silica coated with 0.3 wt% 2,4-dinitrophenylhydrazine. Carbonyls are converted into the 2,4-dinitrophenylhydrazone derivative, which is eluted with 5 mL of acetonitrile and analyzed by HPLC. The products are readily detected by their strong ultraviolet absorbance near 360 nm. 

Liquid absorption is a common technique for enriching compounds in reactive liquids like solutions of dinitrophenylhydrazine (DNPH) (for aldehydes), acetyl acetone (for formaldehyde) or aqueous carbonate solutions (for organic acids), both procedures which combine trapping and derivatization of the target compound. Another possibility is the use of dissolved alkali or acids to trap certain substances by the formation of salts in the solution. 

Simple aldehydes, such as formaldehyde or acrolein may be analyzed by derivatizing into a suitable derivative for GC-FID or -NPD determination (Methods 2502, 2501, NIOSH 1984). The derivatizing agents for these compounds are 2-(benzylamino)ethanol and 2-(hydroxymethyl)piperidine, respectively, coated on a support. Formaldehyde may also be determined using colorimetry and polarography (Methods 3500 and 3501, NIOSH 1984). See Part 3 of this book. 

Use of pure thiazolidine standards to prepare standard curves and evaluate derivatization and extraction efficiency. The exact purity of commercial aldehyde reagents (particularly formaldehyde) is difficult to determine. Thiazolidines can either be purchased commercially (with exactly known purity) or easily synthesized and purified and would provide improved precision in preparing the standard curve and calculating concentrations. 

Of course, derivatization methods can also be used for the identification of organic acids. For example, volatile fatty acids in urine and plant protein hydrolysates were esterified with phenyldiazomethane and the resulting benzyl esters were separated by glass capillary GC [254]. Janos et al. [255] described a method for the analysis of dimedone derivatives of formaldehyde and other aliphatic aldehydes on capillary columns. Phenolic amines, 3-methoxycatecholamines, indoleamines and related amines can be determined as their N,0-ethyloxycarbonyl derivatives [256]. The reaction of dithiols and certain monothiols with phenylarsine oxide was used for derivatization prior to GC [257]. Destructive GC methods for the identification of microorganisms were described in refs. 258-261. 

Brunnemann et al. (500) detemiined several volatile aldehydes and ketones in tobacco headspace and tobacco smoke by derivatization with 2,4-dinitrophenylhydrazine. Tobacco smoke carbonyl components identified included Formaldehyde, acetaldehyde (1000 pg/cig), propionaldehyde (propanal), acrolein (propenal), isobutyraldehyde (2-methylpropanal), crotonaldehyde (2-butenal), methacrolein (2-methylpropenal), benzaldehyde (1 pg/cig), and acetone. 

Igawa et al. (1989) have reported analysis of formaldehyde and other aldehydes in cloud and fogwater samples by HPLC with a postcolumn reaction detector. The aldehydes were separated on a reversed-phase C18 column, derivatized with 3-methyl-2-benzothiazolinone hydrazone, and detected at 640 mn. 

Heterocyclic compounds. Thiazolidine-4-carboxylic acid and 5,6-dimethylthiazolidine-4-car-boxylic acid are formed by formaldehyde condensation from cysteine and penicillamine, respectively. The derivatization of penicillamine has been published (195). Table 14 and Fig. 15 present a summary of these results. The chromatographic characteristics of the thiazolidine carboxylic acids formed by the reaction of D,L-peniciIlamine with various substituted benzaldehydes and heterocyclic aldehydes have also been studied (177). 3-Carboxy-morpholine was separated by Gunther et al. (102). 

Other potential markers for lipid peroxidation include straight-chain, low-molecular weight aldehydes, such as formaldehyde, acetaldehyde, and propanal, and o,p-unsaturated carbonyls, such as acrolein. Acrolein and other a,p-unsaturated carbonyls can be derivatized to form N-methylpyrazolines, while the aldehydes are converted to... 

Special Condensation Products.—Several of the most common carbonyl compounds (formaldehyde, acetaldehyde, and acetone) are derivatized best by means of condensation reactions other than those discussed above the two aldehydes may be condensed with jS-naphthol according to the directions outlined by Alulliken, I, pages 23-25. 

The derivatizing reagent is prepared by dissolving 124 g 2,4-dinitrophenylhydrazine in 100 mL CH3CN and adding 2 mL 2 M HCl. DNPH derivatives of formaldehyde, acetaldehyde, and propionaldehyde are used as standards. They are prepared by reaction of the aldehydes with 2M HCl saturated with 2,4-dinitrophenylhydrazine, separated from the reaction mixture by filtration, washed with water and 2 M HCl, air-dried, and stored in a desiccator. 

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