PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 16307890

Quantitative spectrophotometry using integrating cavities.

Tamás Jávorfi·János Erostyák·József Gál·Andrea Buzády·László Menczel·Gyozo Garab·K Razi Naqvi
View original source ↗Export metadata ↓

Abstract

Absorption spectrophotometry, a standard tool for quantitative analysis, suffers from two major drawbacks: lack of sensitivity and vulnerability to scattering. It has been pointed out earlier that the solution to these problems lies in using a reflecting cavity as a sample holder. Due to multiple reflections at the cavity wall, the effective pathlength becomes considerably larger than the diameter of the cavity, and scattering losses are eliminated because scattered light is prevented from escaping the detector. Though much effort has been spent in analysing and improving the performance of such a device, often called an integrating cavity absorption meter (ICAM), a simple strategy for deducing the absorbance of the sample is still lacking. It is shown here that the absorbance A' measured by using an ICAM exhibits a sublinear increase with the solute concentration C. The physical reason for this departure from linearity is explained, and a straightforward procedure for converting A' to the true absorbance A (proportional to C) is established. The reliability of the procedure is demonstrated by comparing the ICAM absorption spectrum of dilute dye solutions with the spectra of more concentrated solutions recorded in a conventional spectrophotometer. The ability of the device to cope with scattering was tested by filling the ICAM with a suspension of chloroplasts, and the spectrum was found, as expected, to be free from scattering artefacts.

Explore related subjects

CalibrationChloroplastsEquipment DesignFluorescent DyesReproducibility of ResultsRosaniline DyesRose BengalSpectrophotometryJournal ArticleResearch Support, Non-U.S. Gov't

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Tamás Jávorfi, János Erostyák, József Gál, Andrea Buzády, László Menczel, Gyozo Garab, K Razi Naqvi. 2005-11-22. Quantitative spectrophotometry using integrating cavities.. https://doi.org/10.1016/j.jphotobiol.2005.10.002

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2007

Fermentation process tracking through enhanced spectral calibration modeling.

The FDA process analytical technology (PAT) initiative will materialize in a significant increase in the number of installations of spectroscopic instrumentation. However, to attain the greatest benefit from the data generated, there is a need for calibration procedures that extract the maximum information content. For example, in fermentation processes, the interpretation of the resulting spectra is challenging as a consequence of the large number of wavelengths recorded, the underlying correlation structure that is evident between the wavelengths and the impact of the measurement environment. Approaches to the development of calibration models have been based on the application of partial least squares (PLS) either to the full spectral signature or to a subset of wavelengths. This paper presents a new approach to calibration modeling that combines a wavelength selection procedure, spectral window selection (SWS), where windows of wavelengths are automatically selected which are subsequently used as the basis of the calibration model. However, due to the non-uniqueness of the windows selected when the algorithm is executed repeatedly, multiple models are constructed and these are then combined using stacking thereby increasing the robustness of the final calibration model. The methodology is applied to data generated during the monitoring of broth concentrations in an industrial fermentation process from on-line near-infrared (NIR) and mid-infrared (MIR) spectrometers. It is shown that the proposed calibration modeling procedure outperforms traditional calibration procedures, as well as enabling the identification of the critical regions of the spectra with regard to the fermentation process.

Calibration↗
PubMed2007

Simultaneous determination of seven active components of Fufang Danshen tablet by high performance liquid chromatography.

A high-performance liquid chromatography method was established for simultaneously determining seven major components, i.e. protocatechuic aldehyde, notoginsenoside R(1), ginsenoside Rg(1), salvianolic acid B, ginsenoside Rb(1), cryptotanshinone and tanshinone IIA in Fufang Danshen tablet, a commonly used traditional Chinese medicinal combined prescription mainly derived from the roots of Salvia miltiorrhiza and Panax notoginseng. These seven compounds, belonging to the chemical types of phenolic acids, diterpenoid quinones and saponins, were simultaneously separated on Zorbax C(18) column (250 x 4.6 mm, 5.0 microm) with the column temperature at 30 degrees C. The mobile phase was composed of (A) aqueous phosphoric acid (0.1%, v/v) and (B) acetonitrile using a gradient elution of 7-17% B at 0-10 min, 17-20% B at 10-12 min, 20-21% B at 12-16 min, 21% B at 16-32 min, 21-29% B at 32-40 min, 29-35% B at 40-55 min, 35-65% B at 55-65 min and 65-80% B at 65-80 min; the flow rate was 1.0 mL/min. Detection wavelengths were set at 203 nm for notoginsenoside R(1), ginsenoside Rg(1) and ginsenoside Rb(1), 281 nm for protocatechuic aldehyde, salvianolic acid B, and 270 nm for cryptotanshinone and tanshinone IIA. All calibration curves showed good linear regression (r(2) > 0.9992) within test ranges. The established method showed good precision and accuracy with overall intra-day and inter-day variations of 0.15-4.35 and 0.61-5.17% respectively, and overall recoveries of 94.8-102.1% for the seven compounds analyzed. The developed method has been successfully applied to simultaneous evaluation of the intrinsic quality of both Danshen and Sanqi in Fufang Danshen tablets from different pharmaceutical companies.

Calibration↗
PubMed2007

Pesticide multiresidue analysis in Panax ginseng (C. A. Meyer) by solid-phase extraction and gas chromatography with electron capture and nitrogen-phosphorus detection.

An analytical multi-residue method using gas chromatography coupled with electron capture and a nitrogen-phosphorus detector was investigated for the simultaneous determination of 18 commonly used insecticides and fungicides in Korean ginseng (Panax ginseng C. A. Meyer). Samples were previously extracted with an acetonitrile and cleaned up by solid-phase extraction (SPE). The calibration curves were linear, with determination coefficients higher than 0.989. Recoveries at concentrations between 0.01 and 14.9 ppm ranged from 72.3 to 117.2%, with precision, which was expressed as relative standard deviation (RSD), at values lower than 5%. The proposed method was applied to the determination of pesticide levels from 12 ginseng samples, taken from four different agricultural areas of Jeonnam province, where several insecticides and fungicides were applied. Except in one sample, tolclofos-m was the only pesticide contained at a level lower than the maximum residue limits (MRL) authorized by the Korea Food and Drug Administration (KFDA) in real ginseng samples grown for 4, 5 and 6 years.

Calibration↗