Separation of Phenothiazine Derivatives on Basic Aluminum Oxide TLC Plates
Phenothiazine salts migrate little, if at all, on acid aluminum oxide plates. On layers of neutral and more particularly basic Aluminum Oxide TLC layers, good migration is achieved by virtue of exchange processes (similar to those with alkaloid salts on aluminum oxide layers). Benzene is a suitable developing solvent with the addition of 5% acetone. Dragendorff reagent is used as a developer. If the acetone content is increased, the Rf-value becomes greater.

Phenothiazine Pure Substance Rf-value Drops Rf-value Ampoules Rf-value
Megaphen 0.51 0.54 0.53
Verophen 0.31 0.36 0.40
Atosil 0.58 0.56 0.61
Lorusil 0.22 - 0.24
Randolectil 0.23 - 0.23
Neurocil 0.71 - 0.71
Latibon 0.84 - 0.85
Andantol 0.42 - 0.48

Identification of Methaquallone in tissue and Blood via TLC and Mass Spectrometry
It is difficult to distinguish between methaqualone and substances with similar Rf-values only via thin-layer chromatography. If this problem arises, methaqualone may be identified by the mass spectrum of the substance adhering to the adsorbent.

Chromatographic examination of autopsy-blood extract contaminated with decomposition products of hemoglobin, was carried out on Silica Gel F TLC, using chloroform/acetone 9 + 1 (v/v) and Dragendorff reagent, and showed a substance spot at Rf = 0.80-0.83.

The reference substances showed the following Rf values:
Methaqualone = 0.84
Glutethimide = 0.78

For improved differentiation, the spot detected on the plate under UV-light was scraped off, the sample was extracted with diethyl ether, decanted, enriched in a small amount of silica gel, and placed directly into the ion-source of the mass spectrometer. The attached figure shows the mass spectra of the sample and of the pure substance methaqualone.

Quantities of about 15-20 ug. of methaqualone can be reliably detected by means of this procedure.

After filtration, the tartaric filtrate is extracted with ether and is dried over sodium sulfate and evaporated. Urine, after addition of hydrochloric acid (pH 3-4), is exhaustively extracted by ether. The ether is dried over sodium sulfate, treated with a small amount of active carbon and Aluminum Oxide Neutral, Act. 1, for a short time, and finally evaporated.

The residue is chromatographed on Silica Gel GF TLC (Cat#: 83111) with the solvent chloroform/acetone 9:1. For the detection of the substance spots the thin-layer chromatograms are sprayed with mercurous-(I)-nitrate, Zwikkers reagent, and mercurous-(II) sulfate/diphenylcarbazone.

Two samples each of the test material are spotted adjacent to each other. Both samples are primarily evaluated under UV-light. One sample is used for a color test and the corresponding zones of the second sample for the mass spectrometry. For this purpose the single spots are scraped off, extracted by ether, and the ether is decanted and evaporated. The enriched substances are brought directly into the ion source of the mass spectrometer. They allow mass spectra, which can be reliably evaluated.

Detection of Barbituric Acid Derivatives by TLC and Mass Spectrometry in Autopsy Material
The following substances could be identified:

Barbital Crotylbarbital
Secbutabarbital Vesperone
Pentobarbital Carbromal
Phenobarbital Bromisoval
Vinylbitalum Cyclobarbital
Secobarbital Heptabarbum
Butalbital Hexobarbital

The identification of about 20-25 ug of 12 barbiturates as well as Carbromal and Bromisoval, which are often present in pharmaceutical specialties together with 4 barbituric acids, is possible by means of a combination of thin-layer chromatography and mass spectrometry.

Autopsy material is extracted with a solution of tartaric 5 acid in ethanol after homogenization. The ethanol is evaporated and the residue dissolved by warm water.

Identification of Selected Pesticides via Thin-Layer Chromatography
For the detection of pesticide residues in food many methods are published, which in most cases require a considerable amount of apparatus, reagents and time. The separation technique should allow quick detection of the quantity of pesticide residue without much expenditure, and only with small amounts of solvents. This preliminary data will then dictate whether a precise determination of the identified pesticide should follow or whether the approximate value obtained by spot comparison is sufficient.

Summary of 15 substances to be detected include:

  1. Chlorinated hydrocarbons:
    DDT, dieldrin, aldrin, lindane, endsulfan (I and II) as well as pentachloronitrobenzene (PCNB) and tetrachloronitrobenzene (TCNB)
  2. Phosphoric acid esters
    Parathion, dimethoate, bromophos
  3. Fungicides:
    Pentachloronitrobenzene (PCNB), tetrachloronitrobenzene (TCNB), dichlofluanid as well as its metabolite DMSA
  4. Bacteriaostatics:
    IPC (N-phenyl isopropyl carbamate; propham)
  5. Herbicides:
    N-(3-chloro-4-methylphenyl) -2-methylpentanamide(solan)

The plant material is macerated with hexane-isopropyl alcohol(70:30); active substances are transferred into the hexane phase. After drying and removal of pigments a combination column (Alumina Basic, Activity V, and Na2SO4 on top) the yellow extract yield is directly spotted on a thin layer plate. Length of run always 17 cm. - If too much wax is present, it should first be treated with acetonitrile. The sensitivity is usually at 2-6 ug of each active substance, but with DDT even 0.5 ug can be detected.

  1. Chlorinated hydrocarbons are separated on Silica Gel G TLC (Cat#: 83101) in hexane/chloroform (9:1). Detection by spraying with Ag/NO3.
    Aldrin Rf 0.83
    PCNB Rf 0.71
    DDT Rf 0.64
    Lindane Rf 0.22
    Endosulfan Rf 0.15
    Dieldrin Rf 0.08
  2. Phosphoric acid esters are separated on Silica Gel G TLC (Cat#: 83101) or on TLC-plates, pre-coated with Silica Gel F-254 (Cat#: 84111) in hexane/acetone (4:1).
    Parathion Rf 0.45
    Bromophos Rf 0.70
    Dimethoate Rf 0.66
  3. Fungicides, bacteriostatics, and herbicides are separated in the same way as P-esters on TLC plates, pre-coated with Silica Gel F-254 (Cat#: 84111), then diazotised, coupled, and the color products evaluated in UV and visible light.
    PCNB Rf 0.97
    TCNB Rf 0.97 reddish
    Solan Rf 0.49 blue
    IPC Rf 0.52 yellowish
    Dichlofluanid Rf 0.39
    DMSA Rf 0.19 violet red

Thin-Layer Chromatography of Selected Indanol Derivatives of Pharmaceutical Interest

7-Chloro-4-hydroxy Indan, 4-hydroxy-1,5,7-trimethyl Indan, and other indanol derivatives demonstrate excellent bactericidal, fungicidal, and amebicidal properties. Thin-layer chromatography was found to be ideal for qualitative and quantitative control of these substances in pharmaceutical specialties.

Silica Gel GF TLC (Cat# 83111)

Solvent Systems

I Water-saturated chloroform
II Benzene/chloroform/abs,alcohol 4
III Chloroform/abs. alcohol 4:1:1
IV Benzene
V Carbon tetrachloride

After development, the thin-layer plates should be dried. Under UV 254nm the substances appeared as dark spots against the greenish fluorescent background. If the fluorescent indicator is not available, the plates should be sprayed with an aqueous potassium permanganate solution (1%): yellow spots indicate the position of the various compounds on violet brown background.

Substances Rf- Values with various Solvent systems on Silica Gel GF
4-Hydroxy Indan 0.31 0.84 0.78 0.25 Start
5-Hydroxy Indan 0.22 0.82 0.72 0.18 Start
7-Chloro-4-hydroxy Indan 0.28 0.78 0.72 0.23 Start
5,7-Dichloro-4-hydroxy Indan 0.69 0.89 0.91 0.63 0.31
7-Chloro-4-hydroxy Indan-on(1) 0.60 0.91 0.94 0.44 0.08
5-Acetyl Indan 0.60 0.92 0.94 0.34 0.05
5-Amino Indan 0.79 Front 0.94 0.83 0.38
4-Hydroxy-1,5,7 - trimethyl Indan 0.59 0.89 0.84 0.44 0.07

Back to Top