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The simultaneous polarographic determination of the ternary mixture of captan-captafol and folpet is studied. The polarographic signals of these compounds in their mixture show a high overlapping. For this reason different chemometric methods such as PLS, PCR and artificial neuronal network (ANN) have been utilized for the simultaneous determination of these compounds in mixtures. The calibration model is built from solutions containing river water of known pesticide concentrations and the signals obtained by Sampled DC and DPP (differential pulse polarography) have been used. The analysis of both synthetic and real samples (river water) has been carried out by PLS with satisfactory results in most cases. It is possible to determine 0.25 ppm of each pesticide in river water samples after a preconcentration step by extraction into diethyl ether. ANN has also been applied to improve the results obtained by the PLS tool when the sampled DC current is recorded or when liquid-solid extraction with C18 cartridges is performed.
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PMID:Resolution by polarographic techniques of the ternary mixture of captan, captafol and folpet by using PLS calibration and artificial neuronal networks. 1151 36

Three methods are developed for the simultaneous determination of diprophylline (DP), phenobarbitone (PH) and papaverine hydrochloride (PP). The chromatographic method depends on a high performance liquid chromatographic (HPLC) separation on a reversed-phase C18 column with a mobile phase consisting of 0.02 M potassium dihydrogen phosphate, pH 3.5--acetonitrile (55:45 v/v). Quantitation was achieved with UV detection at 210 nm based on peak area. The other two chemometric methods applied were principal component regression (PCR) and partial least squares (PLS-1). These approaches were successfully applied to quantify the three drugs in the mixture using the information included in the UV absorption spectra of appropriate solutions in the range 215-245 nm with the intervals Delta lambda = 0.2 nm. The calibration PCR and PLS-1 models were evaluated by internal validation (prediction of compounds in its own designed training set of calibration), by cross-validation (obtaining statistical parameters that show the efficiency for a calibration fit model) and by external validation over laboratory-prepared mixtures and pharmaceutical preparations. The PCR and PLS-1 methods require neither any separation step, nor any priori graphical treatment of the overlapping spectra of the three drugs in a mixture. The results of PCR and PLS-1 methods were compared with HPLC method obtained in pharmaceutical formulation and a good agreement was found.
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PMID:HPLC and chemometric assisted spectrophotometric methods for simultaneous determination of diprophylline, phenobarbitone and papaverine hydrochloride. 1602 19

This paper demonstrates for the first time the power of a chemometric second-order algorithm for predicting, in a simple way and using spectrofluorimetric data, the concentration of analytes in the presence of both the inner-filter effect and unsuspected species. The simultaneous determination of the systemic fungicides carbendazim and thiabendazole was achieved and employed for the discussion of the scopes of the applied second-order chemometric tools: parallel factor analysis (PARAFAC) and partial least-squares with residual bilinearization (PLS/RBL). The chemometric study was performed using fluorescence excitation-emission matrices obtained after the extraction of the analytes over a C18-membrane surface. The ability of PLS/RBL to recognize and overcome the significant changes produced by thiabendazole in both the excitation and emission spectra of carbendazim is demonstrated. The high performance of the selected PLS/RBL method was established with the determination of both pesticides in artificial and real samples.
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PMID:Partial least-squares with residual bilinearization for the spectrofluorimetric determination of pesticides. A solution of the problems of inner-filter effects and matrix interferents. 1704 1

A new powerful algorithm (unfolded-partial least squares followed by residual bilinearization (U-PLS/RBL)) was applied for first time on second-order liquid chromatography with diode array detection (LC-DAD) data and compared with a well-known established method (multivariate curve resolution-alternating least squares (MCR-ALS)) for the simultaneous determination of eight tetracyclines (tetracycline, oxytetracycline, meclocycline, minocycline, metacycline, chlortetracycline, demeclocycline and doxycycline) in wastewaters. Tetracyclines were pre-concentrated using Oasis Max C18 cartridges and then separated on a Thermo Aquasil C18 (150 mm x 4.6mm, 5 microm) column. The whole method was validated using Milli-Q water samples and both univariate and multivariate analytical figures of merit were obtained. Additionally, two data pre-treatment were applied (baseline correction and piecewise direct standardization), which allowed to correct the effect of breakthrough and to reduce the total interferences retained after pre-concentration of wastewaters. The results showed that the eight tetracycline antibiotics can be successfully determined in wastewaters, the drawbacks due to matrix interferences being adequately handled and overcome by using U-PSL/RBL.
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PMID:Solving matrix effects exploiting the second-order advantage in the resolution and determination of eight tetracycline antibiotics in effluent wastewater by modelling liquid chromatography data with multivariate curve resolution-alternating least squares and unfolded-partial least squares followed by residual bilinearization algorithms II. Prediction and figures of merit. 1806 4

Multivariate spectrophotometric calibration and liquid chromatographic (LC) methods were applied to the determination of 2 multicomponent mixtures containing diprophylline, guaiphenesin, methylparaben, and propylparaben (Mixture 1), or clobutinol, orciprenaline, saccharin sodium, and sodium benzoate (Mixture 2). For the multivariate spectrophotometric calibration methods, principal component regression (PCR) and partial least-squares regression (PLS-1), a calibration set of the mixtures consisting of the components of each mixture was prepared in 0.1 M HCl. Analytical figures of merit such as sensitivity, selectivity, limit of quantitation, and limit of detection were determined for both PLS-1 and PCR. The LC separation was achieved on a reversed-phase C18 analytical column by using isocratic elution with 20 mM potassium dihydrogen phosphate, pH 3.3-acetonitrile (55 + 45, v/v) as the mobile phase and UV detection at 260 and 220 nm for Mixture 1 and Mixture 2, respectively. The proposed methods were validated and successfully applied to the analysis of pharmaceutical formulations and laboratory-prepared mixtures containing the 2 multicomponent combinations.
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PMID:New validated liquid chromatographic and chemometrics-assisted UV spectroscopic methods for the determination of two multicomponent cough mixtures in syrup. 1837 84

In this research, The functional components of vegetable oils were analyzed by near infrared (NIR) spectral technology. The optimum conditions of mathematics model of four components (C16 : 0, C18 : 0, C18 : 1, C18 : 2) were studied, including the sample set selection, chemical value analysis, the detection methods and condition. Chemical value was analyzed by HPLC. 52 samples were selected, 41 for modeling set and 11 for testing set. All samples were placed in 5mm thick sample pools and swept by near infrared (NIR) with discrimination factor 8 cm(-1) without any other disposal. Using PLS methods sated model. Data were processed by first derivative method and centering method. 5 000-9 000 cm(-1) spectral region was analyzed. Correlating index (r), RMSECV and RMSEP were chose as evaluation index. The result demonstrated that the correlation between the reference value of the modeling sample set and the near infrared predictive value were r(C16 : 0) = 0.891, r(C18 : 0) = 0.837, r(C18 : 1) = 0.982, r(C18 : 2) = 0.971, respectively. And the correlation between the reference value of the testing sample set and the near infrared predictive value were 0.921, 0.891, 0.946 and 0.949, respectively. It proved that the near infrared predictive value was linear with chemical value and the mathematical model established for components of vegetable oils was feasible. For validation, 8 unknown samples were selected to be analysis by infrared (NIR). The result demonstrated that error between predict value and chemical value was less than 10%. That was to say infrared (NIR) had a good veracity in analysis components of vegetable oil. Because infrared (NIR) spectral technology is convenient, rapid than HPLC in oil components analysis, moreover, infrared (NIR) can analyze many components at the same time. It must have great application prospect in vegetable oil components analysis.
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PMID:[The rapid analysis of fatty acids in vegetable oils by near infrared spectrum]. 1884 59

A novel liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for trace residue determination of bicozamycin (BZM) in livestock products and seafoods. BZM was extracted from a sample with acetonitrile-water (4 : 1), followed by a two-stage SPE enrichment and cleanup. The first stage involved a styrene-divinylbenzene copolymer cartridge (GL-Pak PLS-2), and the second stage involved a divinylbenzene-N-vinylpyrrolidone copolymer cartridge (Oasis HLB). The LC separation was performed on a C18 column using 0.01% formic acid-methanol (8 : 2) as the mobile phase and MS detection with negative ion electrospray ionization. The mean recoveries from swine muscle, liver, yellowtail, and milk fortified at the minimum residue limit (MRL) levels and 0.01 microg/g were >70%, and the relative standard deviations (RSDs) were <20%. Limits of quantitation (LOQs) ranged from 0.002 to 0.005 microg/g.
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PMID:[Determination of bicozamycin in livestock products and seafoods by liquid chromatography-tandem mass spectrometry]. 1943 51

A simple, inexpensive sample preparation procedure, based on the matrix solid-phase dispersion (MSPD) technique, for the determination of six UV filters: 2-ethylhexyl salicylate (EHS), 3,3,5-trimethylcyclohexyl salicylate (Homosalate, HMS), 3-(4-methylbenzylidene) camphor (4-MBC), isoamyl-p-methoxycinnamate (IAMC), 2-ethylhexyl-p-methoxycinnamate (EHMC) and octocrylene (OCR), in dust from indoor environments is presented and the influence of several operational parameters on the extraction performance discussed. Under the final working conditions, sieved samples (0.5 g) were mixed with the same amount of anhydrous sodium sulphate and dispersed with 2 g of octadecyl bonded silica (C18) in a mortar with a pestle. This blend was transferred to a polypropylene solid-phase extraction cartridge containing 2 g of activated silica, as the clean-up co-sorbent. The cartridge was first rinsed with 5 mL of n-hexane and the analytes were then recovered with 4 mL of acetonitrile. This extract was adjusted to 1 mL, filtered and the compounds were determined by gas chromatography combined with tandem mass spectrometry (GC-MS/MS). Recoveries for samples spiked at two different concentrations ranged between 77% and 99%, and the limits of quantification (LOQs) of the method between 10 and 40 ng g(-1). Analysis of settled dust from different indoor areas, including private flats, public buildings and vehicle cabins, showed that EHMC and OCR were ubiquitous in this matrix, with maximum concentrations of 15 and 41 microg g(-1), respectively. Both UV filters were also quantified in dust reference material SRM 2585 for first time. EHS, 4-MBC and IAMC were detected in some of the analyzed samples, although at lower concentrations than EHMC and OCR.
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PMID:Determination of selected UV filters in indoor dust by matrix solid-phase dispersion and gas chromatography-tandem mass spectrometry. 1953 93

Near infrared spectroscopy as a new method was proposed for rapid and non-destructive measurement of fatty acid composition in intramuscular fat of packed pork loin. Gas chromatography was used as a reference method for the spectral analysis of fatty acid composition. The fiber optic in interactance mode was adopted to measure the spectra of packed pork loins by low density polythene. The original spectra were pretreated by smoothing and 2nd derivative, and then PLS calibration model was builtby using software of Unscrambler 9.6. A total of eighty two samples were used in the experiment. The samples were divided into calibration set and validation set after removing the outliers. The calibration set was used to set up calibration model and then the model was adopted to predict the samples of validation set. The results show that the correlation coefficient for C14 : 0, C15 : 1, C16 : 0, C16 : 1, C18 : 0, C18 : 1, C18 : 2, C18 : 3, C20 : 1, C20 : 4, SFA, MUFA, PUFA is 0.57, 0.76, 0.71, 0.77, 0.62, 0.81, 0.86, 0.91, 0.85, 0.91, 0.67, 0.81 and 0.95, respectively. It means that evaluating fatty acid using near infrared spectroscopy in interactance mode has higher precision. Near infrared spectroscopy technique is a feasible and rapid method for nondestructive detection of fatty acid composition in intramuscular fat of packed pork loin.
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PMID:[Detection of fatty acid composition in intramuscular fat of packed pork loin by near infrared spectroscopy]. 1983 12

This paper presents a novel approach for the simultaneous determination of two widely used fungicides in a very interfering environment, combining the advantage of a spectrofluorimetric optosensor coupled to a flow-injection system and the selectivity of second-order chemometric algorithms. The sensor is based on the simultaneous retention of thiabendazole and fuberidazole on C18-bonded phase placed inside a flow-cell. After the arrival of the analytes to the sensing zone, the flow is stopped and the excitation-emission fluorescence matrix is read in a fast-scanning spectrofluorimeter. Parallel factor analysis (PARAFAC) and unfolded and multidimensional partial least-squares coupled to residual bilinearization (U- and N-PLS/RBL) were selected for data processing. These algorithms achieve the second-order advantage, and are in principle able to overcome the problem of the presence of unexpected interferences. The power of U-PLS/RBL to quantify both fungicides at parts-per-billion levels, even in the presence of high concentrations of spectral interferences such as carbaryl, carbendazim and 1-naphthylacetic acid, is demonstrated. Indeed, U-PLS/RBL allowed us to reach selectivity using a commercial but non-selective sensing support. To the best of our knowledge, this is the first time the potentiality of the 'second-order advantage' is evaluated on a flow-injection system, using an unspecific supporting material and in the presence of three real interferences. Using a sample volume of 2 mL, detection limits of 4 ng mL(-1) and 0.3 ng mL(-1) for thiabendazole and fuberidazol were respectively obtained in samples without interferences. In samples containing interferences, the limits of detection were 17 and 1 ng mL(-1) for thiabendazole and fuberidazol, respectively. The sample frequency, including excitation/emission fluorescence matrix measurements, was 12 samples h(-1). The sensor was satisfactorily applied to the determination of both analytes in real water samples.
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PMID:Second-order advantage with excitation-emission fluorescence spectroscopy and a flow-through optosensing device. Simultaneous determination of thiabendazole and fuberidazole in the presence of uncalibrated interferences. 2039 35


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