Qualitative and Quantitative Analysis of Three-Dimensional Fluorescence Spectra by Improved Parallel Factor Analysis with Internal Standard Sample Embedding.

The strategy of parallel factor analysis, combined with the internal standard method, has been increasingly applied to the qualitative and quantitative analysis of three-dimensional fluorescence spectra of unknown mixed fluorophores. Nevertheless, the disparity in the number of fluorophores included in the internal standard sample set and the number included in test samples may impact the qualitative and quantitative outcomes of parallel factor analysis. In this work, we systematically established the framework of the parallel factor analysis with internal standard sample embedding (ISSE-PARAFAC) strategy.

Rapid determination of benzo[a]pyrene by membrane enrichment coupled with solid-phase constant-wavelength synchronous fluorescence spectrometry.

Normal methods for benzo[a]pyrene (BaP) determination, including gas chromatography-mass spectrometry and liquid chromatography with fluorescence detection, involve expensive instruments and complex separation and purification processes. Based on membrane enrichment, coupled with solid-phase constant-wavelength synchronous fluorescence spectrometry, a simple, fast, sensitive method was proposed for the determination of BaP in water samples. A Nylon membrane was used as the solid-phase extraction material for enrichment.

[Influence of sample annum and distribution of chemical values on NIR veracity].

The influence of sample annum and the distribution of sample component on NIR veracity was studied with homemade grating diffuse NIR instrument using Yunnan flue-cured tobacco. Results showed that sample annum had an obvious influence on the total sugar and nicotine models, but had an unconspicuous influence on the total-nitrogen model. Models set up by samples, whose component content distribution was normal school, was better than those set up by even distribution.

[Influence of sample loading and test conditions on NIR veracity and study of analysis error source].

The influence of sample test conditions on the NIR veracity was studied with homemade grating diffuse NIR instrument using Yunnan flue-cured tobacco. Deducing analysis error was achieved by model self-emendation when a global NIR model was set up. Without regarding the influence of loading samples and test conditions, the test repetition error, re-loading error and samples tightness error, which were brought by instrument S/N, accounted for 50%, 30% and 20% of the total error, respectively.

[Influence of spectrometer scanning requirements in homemade grating diffuse NIR instrument on NIR veracity].

The influence of instrument parameters, such as scan internal, length of instrument run, frequency of scan background etc, on NIR veracity was studied with a homemade grating diffuse NIR instrument using Yunnan flue-cured tobacco. Results showed that scan interval, such as 8 nm or 16 nm, had no evident influence on NIR quantitative analysis. To improve scan speed, the scan interval the authors decided to use was 16 nm.

[Influence of LPLS algorithm parameters on NIR veracity].

The theory of local partial least square (LPLS) algorithm was described based on locally weighted regression algorithm (LWR). The influence of data processing parameters, such as principal component numbers and local set-up sample number in LPLS mode, on the NIR veracity was studied with homemade grating diffuse NIR instrument using Yunnan flue-cured tobacco. Results showed that for nicotine model, the principal component number decided by cross validation was not the best choice, and better results could be achieved by reducing the principal component number; using 30-50 samples to set up NIR model, the veracity of total sugar, total nitrogen, and nicotine could be improved by 7%, 14% and 10%, respectively.