Direct Spectrophotometric Analysis Research Articles

Zur standardisierung der direkten spektrophotometrischen auswertung von chromatogrammen : I. Simultane transmissions- und remissionsmessungen

Standardisation of the direct spectrophotometric quantitative analysis of chromatograms, I. Simultaneous transmittance and reflectance measurements An improved method for the direct spectrophotometric evaluation of thin-layer chromatograms is described. The simultaneous transmittance and reflectance measurement on the same track results in a constant baseline. The advantages of this new method are as follows; increased sensitivity and reproducibility, a linear relationship between the recorded peaks and the amounts present. The possibilities of further technical development and its significance for the research are discussed.

Direct spectrophotometric estimation of amniotic fluid volume

Coomassie's blue was used in the estimation of amniotic fluid volume in 13 patients prior to volumetric measurement at cesarean section. Amniotic fluid volume was calculated by dye dilution, determined by direct spectrophotometric analysis. The optimum time for sampling was found to be 30 minutes after injection. Results with the dilution method correlated to within ±15 per cent of the collected volume, indicating that this technique is sufficiently accurate as well as simple to be clinically useful.

Direct Spectrophotometric Determination of Fat and Moisture in Meat Products

SUMMARY— The near‐infrared spectral absorption properties of P‐mm‐thick samples of meat emulsions were measured by direct spectrophotometric techniques. The resulting spectra are interpreted in terms of absorptions from O‐H and C‐H stretching vibrations combined with scatter losses. Optical‐density differences are correlated with fat and moisture contents. The difference in optical density between 1.80 and 1.725 p gave a high correlation with moisture content and the difference between 1.725 and 1.65 P gave a high correlation with fat content. Direct spectrophotometric analysis predicted fat content within a standard error of ± 2.1% and moisture content within ± 1.4%. The possibilities of this technique are explored and the problems to be solved in developing a rapid, accurate method are discussed

Direct spectrophotometric analysis of ribonucleic acid fractionation by agar-gel electrophoresis

The fractionation of rat-liver RNA was studied by direct ultraviolet densitometry of dry agar electrophoregrams. Highly reproducible electrophoretic patterns of phenol extracted RNA and residual RNA were obtained. Phenol-extracted RNA was resolved into 3 main and 4–6 minor fractions. The main fractions accounted in most cases for 90 % of the absorbancy area and corresponded to the two components of ribosomal RNA and soluble RNA. Residual RNA extracted with phenol at 65° in the presence of sodium dodecylsulphate was resolved into 11–13 fractions, 3 of them being components of ribosomal RNA and low-molecular-weight RNA. A slow-moving region was also present in which the two slowest components are extracted only in the presence of sodium dodecylsulphate.

Determination of furan aldehydes. Reaction with aniline in acetic and hydrochloric acid solutions

Procedures are described for the spectrophotometric determination of 1–7 μg furfural, MF, and HMF per milliliter solution by a combination of several methods as follows: A, by direct spectrophotometry; B, by mixing equal volumes of sample solution and 10% aniline in 80% acetic acid (Reagent 1); C, by mixing equal volumes of sample solution and 10% aniline in approximately 0.9 N excess HCl (Reagent 2). Absorbances are determined at specified wavelengths, depending upon the type of sample analyzed. ( ̄ and λ max of furan aldehydes were as follows when determined under uniform conditions in 0.001 N HCl solution: furfural, 3,540 at 229 mμ and 15,375 at 277 mμ; MF, 2,980 at 228 mμ and 16,220 at 291.5 mμ; HMF, 3,605 at 229 mμ and 16,750 at 284 mμ. No significant differences were observed in 0.001-0.5 N HCl. Data were obtained under the same uniform conditions on furfuryl alcohol, furoic acid, furoin, furil, and the following carbonyl compounds, some of which may be present in distillates or extracts of sugar digests and biological systems: acetone, acetol, methylglyoxal, pyruvic acid, levulinic acid, α-ketoglutaric acid, diacetyl, acetylacetone, acetonylacetone. None of these compounds, even if present in equimolar concentration, except furoin and acetyl acetone, interferes significantly in the determination of furan aldehydes. However, reductic acid, if present in extracts, may interfere greatly: at pH 7.4, ε was 20,705 at λ max 281 mμ; in 0.0002-1.0 N acid, ε and λ max were essentially unchanged, 13,790 (average) at 263 mμ. Oxidation to dehydroreductic acid completely removes the possible interference; ε was 37 and λ max 302 mμ. Direct spectrophotometric analysis of unneutralized distillates from the Tollens method for determining pentosans is feasible, although this is not recommended unless the distillates are redistilled to remove HMF. The reaction with Reagent 1 is highly sensitive for all three aldehydes, not just for furfural as has been assumed in the past. ε and λ max were: for furfural, 30,100 at 513 mμ; for MF, 10,860 at 368 mμ; for HMF, 6,900 at 354 mμ. Furfural gave no absorption peak in the UV; ε was about 2,000 at 368 mμ. The reaction with Reagent 2 is also highly sensitive, especially for MF. ε and λ max were: for furfural, 7,575 at 352 mμ; for MF, 11,750 at 370 mμ; for HMF, 8,220 at 363 mμ. This reagent provides a new condition for determining furan aldehydes. A distillation procedure is described for separating furfural and MF from HMF in which 98–99% furfural and MF, and less than 1% HMF, was recovered in the distillate. Results of the application of Methods A, B, and C to the analysis of furfural and MF are given. The most consistent results were obtained with Method B, using Reagent 1, in which two observations were made: at 513 and at 368 mμ. Thus, the century-old aniline acetate method is useful for determining MF as well as furfural.

Extraction-Flame Photometric Determination of Boron.

Submilligram quantities of boron were completely extracted from aqueous solution into methyl isobutyl ketone as the tetrabutylammonium boron -- tetrafluoride ion association complex. The boron content of the separated organic phase was determined by direct flame spectrophotometric analysis, using an oxygen-sheathed oxyhydrogen flame as the excitation source. Of 30 metal ions studied, only five interfered at a l to 1 mole ratio to boron. Interfering anions were phosphate, perchlorate, and high levels of nitrate. Nitrate interference was eliminated by suifuric acid fuming prior to extraction. (auth)