Detector Composition And Method

Abstract

A colorimetric method and composition for detecting compounds containing ogens or aldehyde groups comprising the steps of contacting the compounds with an inert absorbent impregnated with a detecting composition comprising an amine, heating the absorbent with its contents and observing the visible color change in the absorbent.

Description

DEDICATORY CLAUSE

The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to us of any royalty thereon.

This invention is directed to a method of detecting aldehydes and halogenated compounds of aliphatic hydrocarbons, aldehydes, silanes or phosphates in their vapor state.

The object of this invention is the colorimetric detection of .alpha.-haloaldehydes.

A further object of the invention is the detection of compounds which do not interfere with the color signal for the .alpha.-haloaldehydes.

The detection of chloroaldehydes has been reported by several investigators. Fritz Feigl, Spot Tests in Organic Analysis, Sixth Edition, Elsevier Publishing Company, New York, 1960, describes the method of indicating the presence of trichloroacetic aldehyde by boiling the test sample in aqueous alkali containing pyridine, page 327, or saponifying the aldehyde in a phenol with subsequent condensation with hydrazine, page 355.

In view that there are no simple vapor detecting systems for the .alpha.-haloaldehydes, an investigation was instituted for demonstrating the presence of the aldehydes which are known air pollutants and may cause fatal lung injury.

As a result of our investigation it is now possible to detect .alpha.-haloaldehydes of trichloroacetic aldehyde or dichloroacetaldehyde in the range of at least 5 .mu.g. in the presence of a detector amine selected from the group consisting of aliphatic, aromatic and heterocyclic amines. In addition, other compounds which do not interfere with .alpha.-haloaldehydes detection can be detected alone but at higher concentrations based upon their vapor pressure, that is, these compounds possess relatively higher vapor pressures than the .alpha.-haloaldehydes. These noninterfering compounds include C.sub.3 to C.sub.4 aldehydes, propionaldehyde, n-butylaldehyde, halogenated aliphatic hydrocarbons, silanes or phosphates, for example dibromomethane, carbon tetrabromide, trimethylchlorosilane, 2,2-dichlorovinyl dimethylphosphate. The relative strength of the detecting signal based on the compounds is strong for .alpha.-haloaldehydes, medium for propionaldehyde and weak for the remaining compounds.

The various absorbents that may be employed in this invention are silica gel (28-100 mesh), silica gel powder, and alumina for chromatography (aneonic, cationic or neutral) taught by Brockmann and Schodder, Chem. Ber, Vol. 74, page 73, 1941.

The use of silica gel tubes and the detecting apparatus are well established in the open literature that may be employed according to our colorimetric methods, Shepard, Anal. Chem., 19, 77, 1947; Williams et al., Anal. Chem., 34, 255, 1962; Crabtree et al., Talanta, 14, 857, 1967.

In general the detecting tube containing the detecting mixture is constructed as follows: A glass tube about 4 inches in length 2.5 to 3.0 mm. i.d. containing the mixture which is placed between organdy plugs and then sealing off the glass ends. The filling operation is conventional in the art such as tamping the detecting mixture into the glass tube. Prior to using the filled tube, each sealed end of the tube is broken off and inserted into the sampling apparatus.

The detecting composition for the compounds described in this invention is a mixture comprising about 0.075 to 0.125 g. of an amine and 0.75 to 1.25 g. of an absorbent with subsequent air drying of the mixture. About 0.1 g. of the mixture is placed in the glass tube with proper sealing until the tube is required for use. The impregnation of the absorbent with an amine can be facilitated if desired by mixing the amine with a diluent prior to contacting the absorbent. The diluent may be diethyl ether or ligroin which is a volatile fraction of petroleum boiling in the range of 20.degree. - 135.degree. C.

The apparatus we employed for indicating the presence of the various compounds is disclosed by Crabtree et al., Talanta, 14, 857 (1967). The apparatus can be assembled from equipment readily available in the laboratory. In the following description, the lettered components correspond to the same component in the apparatus description in the aforementioned Talanta publication. A 2.times.9 cm. test tube B, with a capacity of about 12 ml. is fitted with 19/38 standard taper joint with an adopter C, supporting a sidearm air inlet A, length of glass tubing extending to about 5 to 10 mm. from the bottom of test tube. The glass tube D, containing detector mixture was connected by a short length of rubber tubing to the upper end of the glass tubing. The air sample through the air inlet is drawn through the detector mixture by compressing a rubber bulb E, fitted with a one-way valve. In the alternative the sample containing the compound is placed in the bottom of the test tube and air is taken in, by means of the bulb, passing over the sample and the vapors are entrapped in the detecting mixture. The tube is removed and heated in an oven at 110.degree. - 120.degree. C. in accordance with this invention.

The only requirement imposed on the sample is that the compounds be readily vaporizable.

There is a decrease in the sensitivity in the colorimetric determination of the chloroaldehydes resulting from the color masking effect of the aromatic amines. We found that this masking effect can be markedly diminished upon the addition of an equal proportion of dibromomethane, based on the amine, to the aromatic amines in preparing the detector mixture. There is an increase in sensitivity by at least a factor of 3 in view of the fact that the chloroaldehydes can be demonstrated in an amount of 5 .mu.g. as distinguished from 15 .mu.g. in the absence of the dibromomethane functioning as an antimasking agent.

We found that the addition of dibromomethane to the detection mixture comprising aliphatic amines did not produce any noticeable increase in sensitivity. This is probably in part due to the fact that there is not the high color masking effect of the oxidation products of the aliphatic amines as compared with the oxidation products of the aromatic amines.

Although the free base is preferred in the detection mixture, one can employ the salt of the amine with the sacrifice of sensitivity as illustrated in Example 1(c) of 5 .mu.g. o-anisidine and Example 2(c) of 25 .lambda.g. o-dianisidine HCl. This salt effect results in inhibiting the oxidation of the amine.

We found substantially the same color detection signal between the compounds on the various silica gels or alumina absorbents Table 1 sets forth the amine with its corresponding detection color of the trichloroacetic aldehyde on the various absorbents. --------------------------------------------------------------------------- TABLE 1

Color of the Amine Detection Signal Aniline Dark Brown-green N-Methylaniline Green-blue N,N-Dimethylaniline Green-blue 2,5-Diethoxyaniline Brown o-Anisidine Brown o-Dianisidine hydrochloride Light green Diethylamine Brown Cyclohexylamine Yellow Dicyclohexylamine Yellow Tricyclohexylamine Yellow Pyridine Yellow 3-Methyl-2-benzothiazolinone hydra- zone hydrochloride Yellow __________________________________________________________________________

EXAMPLE 1

a. An air sample of 10 to 20 cc. containing 15 .mu.g. of trichloroacetic aldehyde vapor was drawn through the air inlet arm of the apparatus, previously described, and contacting the vapors with about 0.1 g. of detecting mixture prepared from a composition comprising 0.075 to 0.125 g. aniline and 0.75 to 1.25 g. of silica gel (28-100 mesh) in the glass tube. The tube was removed and heated in an oven at 120.degree. C. for about 10 minutes whereby the silica gel turned a dark brown-green indicating the presence of the trichloroacetic aldehyde.

Similar results were obtained in utilizing silica gel powder for the 28-100 mesh silica gel.

b. The procedure in (a), supra, was repeated with the exception of 5 .mu.g. of trichloroacetic aldehyde and about 0.1 g. of detecting mixture prepared from a composition comprising 0.75 to 0.125 g. aniline, 0.075 to 0.125 g. dibromomethane and 0.75 to 1.25 g. of silica gel (powder or 28 to 100 mesh). Upon heating the detecting mixture, the silica gel turned brown-green color.

c. The procedure and proportions in (b), supra, was repeated with the exception of substituting aromatic amine members selected from the group consisting of N-methylaniline, N, N-dimethylaniline, 2,5-diethoxyaniline and o-anisidine for the aniline and giving rise to similar results, that is, 5 .mu.g. of the trichloroacetic aldehyde was demonstrated.

d. The procedure, proportions and components in (a), (b) or (c) were repeated with the exception of substituting the alumina, cationic, anionic or neutral, for the silica gel giving rise to similar results in sensitivity and color of the detection signal upon heating the detector mixture.

EXAMPLE 2

a. The procedure in Example 1(a), was repeated with the exception of 25 .mu.g. of trichloroacetic aldehyde vapor and substituting diethylamine for the aniline and giving rise to the detector mixture turning brown upon after heating.

b. The procedure in (a), supra, was repeated with the exception of utilizing a detector mixture comprising an amine and absorbent, the amine is selected from the group consisting of o-dianisidine HC1, cyclohexylamine, dicyclohexylamine, tricyclohexylamine, pyridine and 3-methyl-2-benzothiazolinone hydrazone hydrochloride and the absorbent is a member selected from the group consisting of anionic alumina, cationic alumina and neutral alumina, giving rise to the corresponding color detection signal.

EXAMPLE 3

The procedures and proportions in Example 1 (a to d) and Example 2 (a to b) were repeated with the substitution of dichloroacetaldehyde for the trichloroacetaldehyde and giving rise to the corresponding color signal.

EXAMPLE 4

a. The procedure in Example 1(a) was repeated with the exception of the air sample saturated with trimethylchlorosilane for the trichloroacetic aldehyde and giving rise to green color detection signal.

b. The procedure in (a), supra, was repeated with the exception of utilizing a detector mixture comprising an amine and absorbent, the amine is selected from the group consisting of o-dianisidine HC1, cyclohexylamine, dicyclohexylamine, tricyclohexylamine, pyridine and 3-methyl-2-benzothiazolinone hydrazone hydrochloride and the absorbent is a member selected from the group consisting of anionic alumina, cationic alumina and neutral alumina, giving rise to the corresponding color detection signal.

c. The procedure in (a) and (b), supra, was repeated with the substitution of saturated air sample selected from the group consisting of propionaldehyde, n-butylaldehyde, dibromomethane, carbon tetrabromide, and 2,2-dichlorovinyl dimethylphosphate and giving use to a corresponding color detection signal.

Claims

We claim:

1. A colorimetric method comprising the steps of passing a gaseous sample selected from the group consisting of haloaldehydes, haloaliphatics, halosilanes, halophosphates and aldehydes through a container containing a mixture comprising an inert absorbent impregnated with a composition containing a substantially dry residue of an amine selected from the group consisting of aliphatic, aromatic and heterocyclic amines, said sample contacting said amines, heating the container and its contents between 110.degree. - 120.degree. C. producing a visible color band in the absorbent.

2. The method according to claim 1, wherein the gaseous sample is haloaldehydes, haloaliphatics, halosilanes, and halophosphates.

3. The method according to claim 2, wherein the amine is aliphatic.

4. The method according to claim 2, wherein the amine is aromatic.

5. The method according to claim 2, wherein the amine is heterocyclic.

6. The method according to claim 1, wherein the gaseous sample is an aldehyde.

7. The method according to claim 6, wherein the aldehyde is propionaldehyde or n-butylaldehyde.

8. A method according to claim 1, wherein the absorbent is silica gel, cationic alumina, anionic alumina or neutral alumina.

9. A method according to claim 1, wherein the amines are aniline, N-methylaniline, N,N-dimethylaniline, 2,5-diethyoxyaniline, o-anisidine, o-dianisidine hydrochloride, diethylamine, cyclohexylamine, dicyclohexylamine, tricyclohexylamine, pyridine or 3-methyl-2-benzothiazolinone hydrazone hydrochloride.

10. A method according to claim 1, wherein the sample is selected from the group consisting of trichloroacetic aldehyde, dichloroacetaldehyde, dibromomethane, trimethylchlorosilane, carbon tetrabromide, and 2,2-dichlorovinyl dimethylphosphate.

11. A method according to claim 1, wherein the absorbent is impregnated with a composition comprising a substantially dry residue of an amine and dibromomethane as an antimasking compound.

12. A method according to claim 11, wherein the sample is haloaldehydes of trichloroacetic aldehyde or dichloroacetaldehyde and the amine is an aromatic amine.

13. The method according to claim 1, wherein the container is a transparent tube.