Densitometry Of Thin-layer Chromatograms Research Articles

PLASMA PHENYLALANINE DETERMINATION BY QUANTITATIVE DENSITOMETRY OF THIN LAYER CHROMATOGRAMS AND BY HIGH PERFORMANCE LIQUID CHROMATOGRAPHY IN RELATION WITH MODERN MANAGEMENT OF PHENYLKETONURIA.

The modern management of phenylketonuria (PKU) consists of generalized newborn screening (NBS) for hyperphenylalaninemia (HPA), confirmation of HPA in children detected in the NBS, introduction of dietary treatment in the first weeks of life, followed by monitoring the treatment of PKU for decades to maintain phenylalaninemia within the limits that will not affect the brain. The present study aimed to evaluate the usefulness of two chromatographic methodologies for determination of plasma Phe level in the routine management of PKU: the two dimensional thin layer chromatography (2D - TLC) and the high performance liquid chromatography (HPLC) procedures, respectively. Samples of blood from 23 children with HPA detected by neonatal screening or with confirmed PKU who received treatment by low-Phe diet were analyzed to estimate the plasma Phe level by the two chromatographic procedures. In case of three subjects the very low concentrations of plasma Phe could not be detected by the 2D - TLC methodology, since the spot was not visible on the chromatogram. In four patients the differences between the values of plasma Phe determined by the two methodologies are not statistically significant, while in fifteen subjects the differences are highly statistically significant. This is due to the greater errors that appear in the case of 2D - TLC methodology. In the range of concentrations of plasma Phe higher than 360 μmol/L (which is the cut-off value for HPA), although in four cases there were statistically significant differences in the level of plasma Phe determined by the two methodologies, the value obtained by the 2D - TLC methodology was high enough to influence the decision of changing the diet so that HPA is kept under control. In addition, the intense spot of Phe on the 2D - TLC chromatogram may be detected even by un unexperienced laboratory specialist. The HPLC procedure for measurement of plasma Phe level is very suitable to be used in the routine management of PKU. The 2D - TLC procedure may be accompanied by relatively high errors; however, it detects patients with severe PKU.

Microdetermination of thiocyanate and selenocyanate by densitometry of thin-layer chromatograms

Microdetermination of thiocyanate and selenocyanate by densitometry of thin-layer chromatograms

Microdetermination of parmidin (pyridinol carbamate) in human blood serum and urine by the method of densitometry of thin-layer chromatograms

Microdetermination of parmidin (pyridinol carbamate) in human blood serum and urine by the method of densitometry of thin-layer chromatograms

Quantitative Determination of Tris-(2,3,-dibromopropyl) Phosphate by Densitometry of Thin Layer Chromatograms

The flame retardant tris-(2,3-dibromopropyl) phosphate (Tris) was chromatographed on silica gel thin layer plates, using ethyl acetate-hexane (30+70) as the developing solvent. Tris was visualized by spraying the chromatogram with 1% aqueous silver nitrate followed by exposure to ultraviolet light for 40 min. Tris appeared as dark gray spots on a white background; the spots were quantitated by densitometry at 660 nm. The lower level of sensitivity was 50 ng; calibration plots were linear from 50 to 800 ng. The procedure was developed to determine the levels of unmetabolized Tris remaining after exposure to sewage sludge suspensions. Recovery of Tris from 3 sewage sludge samples fortified at the 1.0 ppm level averaged 97%.

Determination of vitamins A, B1, B2, D3 and C by densitometry of thin-layer chromatograms

A method for densitometric determination of vitamins A, B1, B2, D3, and C separated by t. l. c. is described. A silica gel layer is used with a solvent system of acetone-methanol-benzene (1∶2∶8). The spots are evaluated by direct densitometric light emission measurements. Preliminary separation of the vitamins one from another or from other pharmaceuticals is not necessary. The accuracy of the method is about 6%. The accuracy for vitamin A is up to 12%.

Quantitative Determination of Carbaryl in Apples, Lettuce, and Water by Densitometry of Thin Layer Chromatograms

A method for the quantitative determination of carbaryl insecticide by in situ densitometry was developed. After separation on silica gel thin layer plates, carbaryl residues were detected by using p-nitrobenzenediazonium fluoborate reagent and quantitated by scanning the resultant blue spots with a fiber optics densitometer and comparing them with standards. The method was applied to water fortified with carbaryl at 8 ppb and apples and lettuce fortified at 0.10 ppm; all recoveries were greater than 89%. The 2 crop extracts were cleaned up by using the AOAC thin layer chromatographic method for visual estimation of carbaryl. Related carbamate insecticides were detected by using the same reagent, and the potential for quantitation was demonstrated.

Erythromycin series : V. Quantitative analysis of cladinose and methylcladinoside by densitometry of thin-layer chromatograms

A direct, quantitative, thin-layer chromatographic method is described for the determination of sugar cladinose and methylcladinoside in the presence of other acid-degradation products of the antibiotics erythromycin oxime and erythromycylamine. Cladinose and methylcladinoside are separated from compounds which cause interference on pre-coated silica gel F 254 plates, and are measured directly on the thin-layer plate using a densitometer. Standard graphs obtained for cladinose and methylcladinoside show a linear relation between the square root of the peak area and the logarithm of the amount of substance present in the spot, as well as between the square of the area and the logarithm of the amount. This method is very successful in stability studies on the antibiotics erythromycin oxime and erythromycylamine in an acid medium. The technique seems to be particularly useful in instances in which the usual analytical methods either cannot be applied or can be applied only with difficulty.

Quantitative determination of triterpenoids of the dammarane series by the densitometry of thin-layer chromatograms

Using the optical densitometry of thin-layer chromatograms, the amounts of triterpenoids of the dammarane series have been determined in the unsaponifiable fractions of ethereal extracts from the leaves of Far Eastern species of birch:Betula costata, B. mandshurica, B. dahurica, B. platyfolia, andB. kamtschatica.

Studies on Thin-Layer Chromatography of Inorganic Compounds. XIII. : Determination of Metallic Dithizonates by Densitometry of Thin-Layer Chromatograms

Separation and determination of eight inorganic ions by thin-layer chromatography were examined. The metallic ions of Hg2+, Cu2+ and Pd2+ were extracted with dithizone chloroform solution at pH 0-1 (1 N HCl solution) and those of Ni2+, Co2+, Zn2+, Bi3+ and Pb2+ at pH 7-8. These dithizonates were separated on MN-silica gel layer by using carbon tetrachloride-methylene-chloride-benzene (1 : 7 : 4) as a developer. The chromatogram of each dithizonate was determined by densitometry. The coefficient of variation of these determined dithizonates was 0.89-9.81%. This method seemed to be applicable to a simplified determination.

Quantitative analysis of metallic ions by densitometry of thin layer chromatograms

鉛,クロム,マンガン,ニッケル,銅,コバルト,水銀,亜鉛,ビスマス,鉄,バリウム,ストロンチウムの普通金属イオン12種につき,薄層クロマトグラフィーにより得られるクロマトグラムのデンシトメトリーによる定量を行ない,3～12%程度の誤差範囲内で半定量ができることがわかった.なお,クロマトグラムの面積法による定量も検討したが,一般的には試量の対数と面積の平方根との間に比較的直線性のある場合が多かった.

Quantitative determination of bufo-steroids by densitometry of thin-layer chromatograms

ブホステロイドのアルミナによる薄層クロマトグラフィーと濃度計による定量法を検討し,その結果に基づき,各種市販センソの成分定量を試みた.アルミナは既報のシリカゲルよりさらによい分離能を与え,展開剤にアセトン-クロロホルム-シクロヘキサン(3:3:4)および酢酸エチル-エーテル(1:1)を使用することにより,全ブホステロイドを1枚のプレート上に分離検出することができた.また薄層クロマトグラムの濃度計による定量において,吸着剤の層厚(0.5mm),試料のつけ方,展開距離(14cm),発色剤の噴霧,測定時間(5分以内)などの条件を常に一定に保つことにより,5～10μgにおいてほぼ直線性の検量線を得た.本法をセンソ成分の定量に応用して,偏差5%以内の精度で各ブホステロイドを迅速に測定するとともに,その測定結果から,センソの種類により各ブホステロイドの含量に差のあることを知った.

Quantitative determination of bile acids by direct densitometry of thin-layer chromatograms.

Abstract A method was developed for quantitative analysis of bile acids by chromatography and densitometry. Within the range of experimental error, the results of cholic and chenodesoxycholic acid determinations on biological samples agreed with those obtained by the spectrophotometric method of Ganshirt1. Reproducibility was influenced by the uniformity of the plate-coating and of the spraying, by width of channels, and by spot size. Since several samples may be run simultaneously and it is unnecessary to locate and remove them from the plates for spectrophotometric analysis, this method has advantages over methods currently employed for bile acid analysis.