Development of an on-line lab-on-valve micro-solid phase extraction system coupled to liquid chromatography for the determination of flavonoids in citrus juices.

An on-line lab-on-valve system for renewable micro-solid phase extraction coupled with high performance liquid chromatography with photodiode array detection was developed for the determination of hesperidin and diosmin in natural and commercial citrus samples. The method is based on the automatic loading of 8 mL of sample into the C resin, followed by matrix clean-up and elution of the analytes with 0.27 mL of acetonitrile.

Estrogens determination exploiting a SIA-LOV system prior in-port derivatization-large volume injection-programmable temperature vaporization-gas chromatography.

In this work, we present a method for the clean-up, preconcentration and quantification of the four most widely found estrogens (estrone E1, estradiol E2, estriol E3 and ethynyl estradiol EE2) in seawater samples. A sequential injection analysis-lab on valve system (SIA-LOV) has been developed to perform the microsolid phase extraction (µSPE) of the analytes in a fully automated way. After testing different resins and solvents, C18 resin with acetonitrile (ACN) as eluent have been chosen as they provided the best results.

Chemical and bioactivity screening of subcritical water extracts of chokeberry (Aronia melanocarpa) stems.

Subcritical water extracts of chokeberry (Aronia melanocarpa) stems were chemically and biologically characterised. Chemical profile was defined by GC-MS analysis whereas anti-oxidant, anti-diabetic and tyrosinase-inhibitory activities of the extracts were investigated by in vitro assays. Antioxidant activity assays revealed strong activity against DPPH radical (IC = 0.

Simultaneous dispersive liquid-liquid microextraction derivatisation and gas chromatography mass spectrometry analysis of subcritical water extracts of sweet and sour cherry stems.

Cherry stems have been used in traditional medicine mostly for the treatment of urinary tract infections. Extraction with subcritical water, according to its selectivity, efficiency and other aspects, differs substantially from conventional extraction techniques. The complexity of plant subcritical water extracts is due to the ability of subcritical water to extract different chemical classes of different physico-chemical properties and polarities in a single run.

Determination of herbicides in environmental water samples by simultaneous in-syringe magnetic stirring-assisted dispersive liquid-liquid microextraction and silylation followed by GC-MS.

An on-line, fast, simple, selective, and sensitive method has been developed for the determination of three herbicides belonging to the following families: triazines (atrazine), chloroacetamide (alachlor), and phenoxy (2,4-dichlorophenoxyacetic acid) in water samples. The method involves an in-syringe magnetic stirring-assisted dispersive liquid-liquid microextraction along with simultaneous silylation prior to their determination by gas chromatography with mass spectrometry. Extraction, derivatization, and preconcentration have been simultaneously performed using acetone as dispersive solvent, N-methyl-N-tert-butyldimethylsilyltrifluoroacetamide as derivatization agent and trichloroethylene as extraction solvent.

Use of multiresponse statistical techniques to optimize the separation of diosmin, hesperidin, diosmetin and hesperitin in different pharmaceutical preparations by high performance liquid chromatography with UV-DAD.

A new method for the separation and determination of four flavonoids: hesperidin (HES), diosmin (DIO), hesperitin (HTIN), and diosmetin (DTIN) in pure form and pharmaceutical formulations has been developed by using high performance liquid chromatography (HPLC) with UV-DAD detection. Multivariate statistics (2 full factorial and Box Behnken Designs) has been used for the multiresponse optimization of the chromatographic separation, which was completed in 22min, and carried out on a symmetry® C18 column (250×3mm; 5µm) as stationary phase. Separation was conducted by gradient elution mode using a mixture of methanol, acetonitrile and water pH: 2.

In-syringe magnetic stirring-assisted dispersive liquid-liquid microextraction and silylation prior gas chromatography-mass spectrometry for ultraviolet filters determination in environmental water samples.

A novel online approach involving in-syringe magnetic stirring assisted dispersive liquid-liquid microextraction and derivatization coupled to gas chromatography-mass spectrometry has been developed for the determination of seven UV filters extensively used in cosmetic products in environmental water samples. The effect of parameters such as the type and volume of extraction solvent, dispersive solvent and derivatization agent, pH, ionic strength and stirring time, was studied using multivariate experimental design. Extraction, derivatization and preconcentration were simultaneously performed using acetone as dispersive solvent, N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) as derivatization agent and trichloroethylene as extraction solvent.

On-line in-syringe magnetic stirring assisted dispersive liquid-liquid microextraction HPLC--UV method for UV filters determination using 1-hexyl-3-methylimidazolium hexafluorophosphate as extractant.

An environmental friendly and fully automated method using in-syringe magnetic stirring assisted dispersive liquid-liquid microextraction coupled with high-performance liquid chromatography has been developed for the determination of UV filters in environmental water samples. The main "green" features on this method are the use of an ionic liquid as extracting solvent, avoiding the use of chlorinated solvents, and the on-line microextraction, preconcentration, separation and detection minimizing the use of reagents and so the waste generation. After sample treatment, 20 µL of the organic droplet was injected onto the HPLC-UV system.

Development of a MSFIA sample treatment system as front end of GC-MS for atenolol and propranolol determination in human plasma.

An on-line solid-phase extraction (SPE) method coupled to gas chromatography-mass spectrometry (GC-MS) has been developed for the determination of atenolol (ATN) and propranolol (PRO) in human plasma. The hyphenation of SPE with multisyringe flow injection analysis (MSFIA) allows the simultaneous GC-MS determination of ATN and PRO with high selectivity and sensitivity. On-line preconcentration and derivatisation of the analytes were carried out by means of using restricted access materials (RAM) and microwave (MW) assisted derivatisation reactions with N-methyl-N-(trimethylsilyl) trifluoroacetamide (MSTFA)+1% trimethylchlorosilane (TMCS).

In-syringe-assisted dispersive liquid-liquid microextraction coupled to gas chromatography with mass spectrometry for the determination of six phthalates in water samples.

A fully automated method for the determination of six phthalates in environmental water samples is described. It is based in the novel sample preparation concept of in-syringe dispersive liquid-liquid microextraction, coupled as a front end to GC-MS, enabling the integration of the extraction steps and sample injection in an instrumental setup that is easy to operate. Dispersion was achieved by aspiration of the organic (extractant and disperser) and the aqueous phase into the syringe very rapidly.

Analysis of cocaine and benzoylecgonine in urine by using multisyringe flow injection analysis-gas chromatography-mass spectrometry system.

In this paper, a method was described to determine cocaine (COC) and benzoylecgonine (BZE) in human urine samples by GC-MS detection. The extraction of analytes from urine samples was achieved in an Oasis hydrophilic-lipophilic balance column (20 mmx3.9 mm id, dp=25 microm; Waters, USA), incorporated in a multisyringe flow injection system, used for the sample treatment.

Determination of losartan, telmisartan, and valsartan by direct injection of human urine into a column-switching liquid chromatographic system with fluorescence detection.

Column-switching high-performance liquid chromatographic (HPLC) method has been developed and validated for quantification of losartan, telmisartan, and valsartan in human urine. Urine samples were diluted on the extraction mobile phase (1:4, v/v) and a volume of 20 microL of this mixture were directly injected onto the HPLC system. The analytes were extracted from the matrix using an on-line solid-phase extraction procedure involving a precolumn packed with 25 microm C(18) alkyl-diol support (ADS), and a solution 2% methanol in 5mM phosphate buffer (pH 3.