FLD Method Research Articles

Determination of zearalenone in traditional Chinese medicinal plants and related products by HPLC–FLD

A HPLC–FLD method has been developed and validated for zearalenone (ZON) in 107 widely consumed Chinese medicinal herbs and related products collected from different regions of China. Samples were extracted with methanol/water (80 : 20, v/v), and the extracts were cleaned-up through immunoaffinity columns (IAC). ZON was quantified by HPLC with fluorescence detection. Recoveries from three different medicinal herbs spiked with ZON at levels ranging from 30 to 600 µg kg−1 were from 80.8 to 98.3%. The limit of detection was 9.5 µg kg−1, based on a signal-to-noise ratio of 3 : 1. Naturally occurring ZON was only found in coix seed medicinal herb (all nine samples), with levels ranging from 18.7 to 211.4 µg kg−1. Positive results were confirmed by UV spectrum and LC–ESI–MS/MS. This is the first report of ZON contamination of a Chinese medicinal herb.

Face recognition by generalized two-dimensional FLD method and multi-class support vector machines

This paper presents a novel scheme for feature extraction, namely, the generalized two-dimensional Fisher's linear discriminant (G-2DFLD) method and its use for face recognition using multi-class support vector machines as classifier. The G-2DFLD method is an extension of the 2DFLD method for feature extraction. Like 2DFLD method, G-2DFLD method is also based on the original 2D image matrix. However, unlike 2DFLD method, which maximizes class separability either from row or column direction, the G-2DFLD method maximizes class separability from both the row and column directions simultaneously. To realize this, two alternative Fisher's criteria have been defined corresponding to row and column-wise projection directions. Unlike 2DFLD method, the principal components extracted from an image matrix in G-2DFLD method are scalars; yielding much smaller image feature matrix. The proposed G-2DFLD method was evaluated on two popular face recognition databases, the AT&T (formerly ORL) and the UMIST face databases. The experimental results using different experimental strategies show that the new G-2DFLD scheme outperforms the PCA, 2DPCA, FLD and 2DFLD schemes, not only in terms of computation times, but also for the task of face recognition using multi-class support vector machines (SVM) as classifier. The proposed method also outperforms some of the neural networks and other SVM-based methods for face recognition reported in the literature.

Development and validation of an HPLC–FLD method for milbemectin quantification in dog plasma

Milbemectin is a widely used veterinary antiparasitic agent. A high-performance liquid chromatography with fluorescent detection (HPLC–FLD) method is described for the determination of milbemectin in dog plasma. The derivative procedure included mixing 1-methylimizole [MI, MI-ACN (1:1, v/v), 100 μL], trifluoroacetic anhydride [TFAA, TFAA-ACN (1:2, v/v), 150 μL] with a subsequent incubation for 3 s at the room temperature to obtain a fluorescent derivative, which is reproducible in different blood samples and the derivatives proved to be stable for at least 80 h at room temperature. HPLC method was developed on C18 column with FLD detection at an excitation wavelength of 365 nm and emission wavelength of 475 nm, with the mobile phase consisting of methanol and water in the ratio of 98:2 (v/v). The assay lower limit of quantification was 1 ng/mL. The calibration curve was linear over concentration range of 1–200 ng/mL. The intra- and inter-day accuracy was >94% and precision expressed as % coefficient of variation was <5%. This method is specific, simple, accurate, precise and easily adaptable to measure milbemycin in blood of other animals.

A simple HPLC–FLD method for the diagnostic of heroin abuse

A simple HPLC–FLD method for the diagnostic of heroin abuse

An improved HPLC method with fluorescence detection for the determination of pyrene in rat plasma and its pharmacokinetics

A high-performance liquid chromatographic method with fluorescence detection (HPLC–FLD) for the determination of pyrene in rat plasma was developed and validated. The method used fluorene as internal standard (IS), following a single-step protein precipitation, the analyte and internal standard were separated on a C18 column with a mobile phase containing methanol–water (90:10, v/v) at a flow rate of 1 ml/min. The analytes were detected by using fluorescence detection at an excitation and emission wavelength of 265 and 394 nm, respectively. Two calibration curves were constructed in the range of 2–100 ng/ml and 0.1–5 μg/ml for pyrene with a lower limit of quantitation (LLOQ) of 2 ng/ml. Both intra-day and inter-day precision were less than 6% except at LLOQ, for which the precision was 10.6 and 9.8, respectively. Accuracy ranged from 98.3 to 103.6%, except at LLOQ, for which the accuracy was about 85%. The recovery ranged from 84.7 to 95.0% at the low, medium and high concentrations. The present HPLC–FLD method was rapid, sensitive, and reliable. The method described herein had been successfully applied for the pharmacokinetic studies in female Wistar rats after administration of 10 mg equivalent pyrene/kg dose of solution of pyrene and 1 mg equivalent pyrene/kg dose of pyrene-loaded nanoparticle.

Diagonal Fisher linear discriminant analysis for efficient face recognition

In this paper, a novel subspace method called diagonal Fisher linear discriminant analysis (DiaFLD) is proposed for face recognition. Unlike conventional principal component analysis and FLD, DiaFLD directly seeks the optimal projection vectors from diagonal face images without image-to-vector transformation. The advantage of the DiaFLD method over the standard 2-dimensional FLD (2DFLD) method is, the former seeks optimal projection vectors by interlacing both row and column information of images while the latter seeks the optimal projection vectors by using only row information of images. Our test results show that the DiaFLD method is superior to standard 2DFLD method and some existing well-known methods.

Comparison of liquid chromatography with fluorescence detection to liquid chromatography–mass spectrometry for the determination of fluoxetine and norfluoxetine in human plasma

A comparison study on fluoxetine (FL) and norfluoxetine (NORFL) quantitation in human plasma was carried out between the recently developed liquid chromatographic method with fluorescence detection (LC-FLD) and an earlier established liquid chromatography-mass spectrometry (LC-MS) laboratory procedure. Comparative method evaluation was based on the analysis of plasma samples obtained from Parkinsonian patients receiving 20mg of FL per day. The LC-FLD method involves a two-step liquid extraction procedure without any derivatization, followed by direct chromatography on a Zorbax C8 reversed-phase column. The analytical results are discussed in terms of the method validation and the corresponding experimental protocol (r>/=0.998; CV<9%; LOQ 20 microg/l). There was good correlation between FL, as well as NORFL, plasma levels as determined by the LC-MS and LC-FLD techniques (r=0.9597, N=16 and r=0.9852, N=14 for FL and NORFL, respectively). The results confirm that direct FL/NORFL fluorimetric determination is acceptable for routine use in pharmacokinetic and clinical studies.

(2D) 2 FLD: An efficient approach for appearance based object recognition

In this paper, a new technique called 2-directional 2-dimensional Fisher's Linear Discriminant analysis ((2D) 2 FLD) is proposed for object/face image representation and recognition. We first argue that the standard 2D-FLD method works in the row direction of images and subsequently we propose an alternate 2D-FLD which works in the column direction of images. To straighten out the problem of massive memory requirements of the 2D-FLD method and as well the alternate 2D-FLD method, we introduce (2D) 2 FLD method. The introduced (2D) 2 FLD method has the advantage of higher recognition rate, lesser memory requirements and better computing performance than the standard PCA/2D-PCA/2D-FLD method, and the same has been revealed through extensive experimentations conducted on COIL-20 dataset and AT&T face dataset.