Absorption chromatogram

Figure 5. HPLC absorption chromatogram (254 nm) of a contaminated two component mixture separated isocratically...

Figure 12 shows the 254 nm absorption chromatogram of a complex mixutre of PAH s extracted from a marine diesel fuel and separated on a reverse-phase C-18 column using a methanol/ water gradient. For this analysis the OMA 2 system was program-... 

Figure 12. HPLC absorption chromatogram of a marine diesel fuel oil...

Figure 15. Three HPLC absorption chromatograms lower is trace enrichment chromatogram of clean (uncontaminated) sea water middle chromatogram is a methanol extract of a Bunker C oil upper chromatogram is a trace enrichment chromatogram of sea water after 1 day contact with Bunker C oil.

Within the front-end processor is an integrator that will integrate the output of the log-ratio-amplifier over the period between the beginning and end-of-scan pulses. This is the equivalent of total ion current in GC/MS the value in LC/UV,VIS is termed a total absorption chromatogram or TAC. 

Figure 4 shows the UV absorption chromatogram for a 1-ml urine sample containing 20 ng of the deuterated analogs of A9-THC, ll-OH-A9-THC, and ll-nor-A9-THC-car-boxylic acid, and 1 yg of a marker compound. In this case the marker compound is 2-methylnaphthalene which... 

Figure 5.4 Refractive index (—) and ultraviolet absorption (—) chromatograms for three ethylene-propylene copolymers grafted by styrene-acrylonitrile (PSAN) copolymers and PSAN contents (O,, x) as a function of retention volume [46].

This effect, which can also be produced if fluorescent substances are applied to the chromatogram by spraying or dipping after development, is an absorption effect and not a quenching process in the true sense of the word. It is correct to refer to fluorescence or phosphorescence diminishing. The more absorbant sample molecules there are present in the zone the darker this will appear (Fig. 4B). 

Photomultipliers are appreciably more sensitive sensors than the eye in their response to line or continuum sources. Monochromators are fitted to the light beam in order to be able to operate as substance-speciflcally as possible [5]. Additional filter combinations (monochromatic and cut-off filters) are needed for the measurement of fluorescence. Appropriate instruments are not only suitable for the qualitative detection of separated substances (scanning absorption or fluorescence along the chromatogram) but also for characterization of the substance (recording of spectra in addition to hR and for quantitative determinations. 

When recording excitation and fluorescence spectra it must be ensured that monochromatic light falls on the detector This can best be verified in instruments built up on the kit principle or in those equipped with two monochromators (spectrofluonmeters) The majority of scanners commercially available at the moment do not allow of such an optical train, which was realized in the KM3 chromatogram spectrometer (Zeiss) So such units are not able to generate direct absorption or fluorescence spectra for the charactenzation of fluorescent components... 

Fig. 1 Absorption curve of a chromatogram track with 4 pg of each substance per chromatogram zone. Rhamnose (1), xylose (2), arabinose (3), fructose (4).

In situ quantitation The absorption photometric scan in reflectance was made at 2 = 435 nm (detection limit 20—30 ng per chromatogram zone). Fluorimetric scanning was performed at 2 c = 436 nm and 2n > 560 nm (detection limit < 10 ng per chromatogram zone). 

Note In the case of HPTLC plates the detection limit for the visual recognition of the violet = 530 nm) colored chromatogram zones was 20 ng per chromatogram zone. With the exception of the two tetrahydrosteroids the cor-ticosteriods could be detected on TLC plates with fluorescent indicators by reason of fluorescence quenching (Fig. 1 A). Figure 2 illustrates the absorption scans of the separations illustrated in Figures 1A and 1B. 

In situ quantitation The absorption-photometric quantitation was carried out in reflectance at 2 = 540 nm. The detection limit was 5 ng substance per chromatogram zone. 

Fig. 1 Absorption scan of a chromatogram with 10 pg ( ) per chromatogram zone of the carboxylic acids tartaric acid (1), malic acid (2), lactic acid (3), succinic acid (4), fumaric acid (5), stearic acid + front (6).

Fig. 1 Absorption scan of a chromatogram track (A) of a gentamycin standard (600 ng gentamycin C complex) and of an accompanying blank (B). Start (1), gentamycin Ci (2), gentamycin C2 and 2. (3), gentamycin Ci, (4), solvent front (5).

In situ quantitation The quantitative analysis is performed by measuring the absorption of the chromatogram zone in reflectance at 2 = 440 nm (Fig. 1). 

Fig. 1 Absorption scan of a chromatogram containing 200 ng dehydroascorbic acid per chromatogram zone.

Fig. 1 Absorption scan (A) and fluorescence scan (B) of a chromatogram track with 200 ng sugar per chromatogram zone raffmose (1), lactose (2) sucrose (3), glucose (4) and fructose...

Fig. 1 Absorption scan of a chromatogram track with 150 ng of each substance per chromatogram zone 1 = demeton-S-methylsulfone, 2 = dimethoate, 3a = transmevinphos,...

Fig. 2 Absorption scans of chromatograms with 50, 100 and 200 ng dibutyltin dichloride per chromatogram zone.

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