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Aldrich Logo Number AL-145

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CAS No. 1750125
Molecular formula: 2H6N6S
Formula weight: 146.18
Melting point: 230-231 °C (dec.)
Appearance: white powder

AL-145 Image 1

Dickinson and Jacobsen1 have described the exceedingly specific and sensitive (to 10-4 M sensitivity) reaction of aldehydes with Purpald® (1) to yield purple-to-magenta-colored 6-mercapto-s-triazolo-[4,3-b]-s-tetrazines (2). Ketones, esters, formic acid, amides, hydroxylamines, quinones, uric acid, hydrazines and aminophenols do not react with 1 to yield purple products.

AL-145 image 2

Procedure for Detection of Aldehydes

One drop of the aldehyde is added to 10-20mg of Purpald dissolved in 2ml of 1N sodium hydroxide. Aeration of the reactants produces the intense color within a few minutes. Very hindered aldehydes may require longer reaction times. Table 1 lists some representative aldehydes and reaction times necessary for color changes.


Table 1*

Aldehyde Color Time
5-Hydroxypentanal purple < 30 sec.
Crotonaldehyde purple -
Benzaldehyde purple < 1 min.
2-Nitrobenzaldehyde purple-brown < 30 sec.
trans-Cinnamaldehyde purple < 5 min.
a-Methylcinnamaldehyde purple < 10 min.
ß-Phenylcinnamaldehyde purple -
4-Acetamidobenzaldehyde purple-brown < 5 min.
2-Chloro-6-nitrobenzaldehyde purple < 5 min.
10-Methylanthracene-9-carboxaldehyde purple very slow
* Tests were performed in the Aldrich Quality Control Laboratories



Since the original work by Dickinson and Jacobsen, 1a variety of methods and applications have been developed for the detection of aldehydes with Purpald. The reagent has been used in conjunction with enzymatic systems for the colorimetric detection of creatinine,2 free fatty acids3 and uric acid.4 Also, triglycerides have been determined in biological samples.5-8

Other applications from current literature include the detection of:

  • formaldehyde in periodate-oxidized glycols,9 air,10 vaccines,11 urea/formaldehyde resins12,13 and plastic products;14
  • acetaldehyde in liver tissue sections15 and on the surface of spoiling fruit;16 
  • formaldehyde generated from alkyl 2-cyanoacrylate vapor in air.17

Purpald is also used in TLC spray reagents,18 filter paper test strips,19 and phase-transfer catalysis.20

Storage and Stability

Purpald should be stored in well closed containers at room temperature. It is relatively stable under normal laboratory conditions.

Toxicity and Handling

To the best of our knowledge, the chemical,physical and toxicological properties have not been thoroughly investigated. The usual safe laboratory precautions and procedures should be observed when handling this material.

® Registered trademark of Aldrich Chemical Co., Inc.


  1. Dickinson, R.G.; Jacobsen, N.W. Chem.Commun. 1970, 1719.
  2. Morishita, Y. et al. Eisei Kensa 1980, 29, 811; Chem. Abstr. 1981, 94, 61043d.
  3. Kosaka, K.; Kikuchi, T.; Mitsuhida, N.; Kawaguchi, A. J. Biochem. (Tokyo) 1981, 89, 1799.
  4. Watanabe, T.; Suga, T. Chem. Pharm. Bull. 1978, 26, 1945.
  5. Fujiwara, M. et al. Rinsho Byori 1981, 29, 1151; Chem. Abstr. 1982, 96, 65147e.
  6. Nishimura, T. et al. ibid. 1973, 21, 839; Chem. Abstr. 1974, 80, 142625h.
  7. Pen, C.-H. Chung-hua I Hsueh Chien Yen Tsa Chih, 1978, 1, 93; Chem. Abstr. 1980, 92, 90266t.
  8. Miyashita, Y. et al. Japan Kokai 74 23 693, 1974; Chem. Abstr. 1974, 81, 60501w.
  9. Avigad, G. Anal. Biochem. 1983, 134, 499.
  10. Lambert, J.; Chiang, Y. U.S. Patent 4 511 658, 1985; Chem. Abstr. 1985, 103, 10756k.
  11. Fujiwara, M.; Tomita, S.; Nishimura, T.Nippon Saikingaku Zasshi 1982, 37, 789; Chem. Abstr.1982, 97, 188351v.
  12. Schriever E. Holz Roh-Werkst 1981, 39, 227; Chem. Abstr. 1981, 95, 99568n.
  13. Harkin, J.; Obst, J.; Lehmann, W. Forest Prod. J. 1974, 24, 27.
  14. Shimada, H.; Tamura, M. Japan Kokai 75 62 694, 1975; Chem. Abstr. 1975, 83, 132542b.
  15. Ryvarden, G.; Kaeferstein, H. Acta Histochem. 1974, 49, 151.
  16. Agatsuma, M.; Ohshima, E. Fr. Demande 2 513 377, 1983; Chem. Abstr. 1983, 99, 18094n.
  17. Walker, R.; Guiver, R. Am. Ind. Hyg. Assoc. J. 1981, 42, 559; Chem. Abstr. 1981, 95, 174473h.
  18. Rahn, C.; Schlenk, H. Lipids 1973,8, 612.
  19. Fischer, W.; Langkau, H. Ger. Offen. 2 809 475, 1979; Chem. Abstr. 1979, 91, 203901w.
  20. Durst, H.D.; Gokel. G.W. J. Chem. Ed.1978, 55, 206.

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