Auswertung von Dünnschicht-Chromatogrammen mit internem Standard

J. High Resol. Chromatogr.

Glaser

1979

Self Cite

Thin-Layer Chromatography, TLC, HPTLC Error analysis for quantitation chromatographic and sampling error often largest SummaryThe paper describes the measurement and calculation of the primary statistical errors in the evaluation of TLC or HPTLC using in situ reflectance measurements. The primary errors are the errors of the sample volume spotted onto the plate, errors caused by the chromatographic process itself, the positioning error of the plate with respect to the centre of the light beam and the error in the light measurement. By scanning the same spot, the same track or the same plate under different conditions, the various errors can be determined.When scanning a TLC-plate using a spectrophotometer for quantitative in situ analysis, there will be some errors caused by different parameters. The main sources of errors in scanning are:0" the error in the sample volume spotted to the plate, (sc the error due to chromatographic causes, for example deviation of the plate from the vertical during development and/or the error in migration distance.the error of positioning the spot in the centre of the light beam, and the error in the measurement of the sample spot, for example the error in the peak area using an integrator.Since the error propagation law is only valid for statistical errors, all parameters causing systematic errors e. g. errors due to spots near the solvent front when using a single beam spectrophotometer, and spots near a so-called pfront, have to be omitted from consideration here. For the same reason measurements have been confined to spots which are sufficiently far from the edge of the plate to prevent systematic errors caused by differences in the layer thickness near the edge. The error in the measurement, a' , , can be determined experimentally by repeatedly scanning one track of the developed TLC-plate without changing any of the other relevant parameters. Typical results are shown in Table 1. In this case the peak heights of the recorded peaks were used. From measurements of a large number of different scans and plates, a mean standard deviation of 0.315 mm has been found and all further calculations will be done with this value. The standard deviation must be the same for all peaks, whereas the relative standard deviation depends on the real peak height. It will be noted that in all the tables the calculated approximate standard deviations are given to one more digit than necessary; this is only done to avoid rounding off errors when subtracting the sauares.The error of positioning the spot in the centre of the light beam may now be evaluated. In this case the same track of the TLC-plate has to be repeatedly measured and the light beam has to be repositioned with respect to the first spot each time. While in the first experiment, in which the position of the plate was held constant, the error in the measurement of the spot size was determined, in this case the error in measurement and in positioning will infkence the result, i.e. the error is given by equation (2), and the positioning e...

“…The error in the sample volume spotted onto the plate can be eliminated by the internal standard technique [6,7]. The factor to be used in the internal standard method is given by eq.…”

Section: Journal Of High Resolution Chromatography and Chromatography Cmentioning

confidence: 99%

“…The factor to be used in the internal standard method is given by eq. (7). Since vx = Vi (both substances are spotted in the same sample volume), eq.…”

Section: Journal Of High Resolution Chromatography and Chromatography Cmentioning

confidence: 99%

Systematic and statistical errors in quantitative evaluation in TLC and HPTLC. 3. The determination of the primary statistical errors

J. High Resol. Chromatogr.

Glaser

1979

Self Cite

Auswertung von Dünnschichromatogrammen mit internem Standard, 3. Mitt.: Zweiwellenlängenmeßtechnik im zigzag Scan

Herold

1976

Archiv der Pharmazie

Ebel und Herold Arch. Pharm. w i d gelb, nach einiger Zeit wird eingeengt und man Wt in der Kdte ausbistallisieren; gelbes Kristallpulver, nach Umkristallisation aus wiiBrigem xthanol gelbe Bliittchen. Schmp. 239' (Zers.); Ausbeute: 2,0 g = 56 % d. Th. C14H16Cl N306 (357,75) Ber.: C 47.(Zc) 0.55 g (2,s mMol) 1 werden in 30 ml siedendem Benzol aufgeschliimmt. Dazu wird eine Losung von 0,s g (2,s mMol) 2,4-Dinitro-phenyl-hydrazin in 110 ml Benzol getropft. Nach Erhitzen unter Ruckflu5 iiber Nacht haben sich hellgelbe Kristak gebildet, nach Umkristallisation aus Xthanol schwach gelb gefiirbte Kristalle. Schmp. 270-271O (Zers); Ausbeute: 500 mg = 50 % d. Th. C1~HISCI N408 (402,8) Ber.: C 41,75 H 3.75 N 13.91; Gef.: C 41,85 H 3,80 N 14.08. Anschrift: Prof. Dr. R. Neidlein, 69 Heidelberg, Im Neuenheimer Feld 364 [Ph 6261 Abb. 1: Zweiwellenliingentechnik h zig-zag-Scan, = 270, = 300 nm. Remisionwad-Ortskuwe des Gemisches Coffein, Paracetamol, Acetylsalicylsiiure,

Über die Bestimmung des Metamizols und seines Hydrolyseproduktes durch quantitative Auswertung von Dünnschichtchromatogrammen

Rost

1978

Archiv der Pharmazie

Ebel und RostArch. Pharm. 4-Methylphenyl-bis-(4-trimethylsilyl-phen yl)-methan (6d)SC: El; leicht gelbliche, amorphe, zahe Mass mit Rf = 0,67 (El Metamizol and its degradation product, 4-methylaminophenazone, were determined by TLC and in situ measurement of their reflectances. In metamizol solutions, used for injections, hydrolysis reaches 3.6 to 4.0 %. This degradation is independent of the storage time.