Highly sensitive serum volatolomic biomarkers for pancreatic cancer diagnosis.

The discovery of new diagnostic tools for the early detection of diseases with poor prognosis such as pancreatic adenocarcinoma (PAC) is of high importance. The results from a control-case study (20 PAC patients, 19 healthy controls) for the search of new biomarkers of pancreatic cancer based in differences in the serum volatolome are presented in this work. Volatolomics were performed following a non-targeted HS-SPME-GC/MS approach, and a total of 433 volatile organic compounds (VOCs) was detected in the human serum samples. Of these, 125 VOC indexes showed a significant variation when controls and patients were compared (p-value < 0.05). Bonferroni corrected p-values < 0.05 were found for 40 features. PCA analysis showed the control-PAC discrimination capability of VOCs in serum, and PLS-DA was performed to select the best candidate biomarkers for the diagnosis of PAC. For the 40 selected VOCs, calculated areas under the curve (AUC) ranged from 0.98 to 0.85, and 11 of them were successfully validated using an independent set of samples (5 PAC patients, 5 healthy controls). Four of the proposed PAC biomarkers were identified as toluene, 2-ethyl-1-hexanol, pentylbenzene, and butoxymethylbenzene. Combinations of the identified PAC biomarkers were tested and showed AUC > 0.90, with the more promising candidate being butoxymethylbenzene (AUC = 0.98).

AuAg Nanoparticles Grafted on TiO2@N-Doped Porous Carbon: Improved Depletion of Ciprofloxacin under Visible Light through Plasmonic Photocatalysis.

TiO2 nanoparticles (NPs) were modified to obtain photocatalysts with different composition sophistication and displaying improved visible light activity. All of them were evaluated in the photodegradation of ciprofloxacin. The band gap of TiO2 NPs was successfully tailored by the formation of an N-doped porous carbon (NPC)-TiO2 nanohybrid through the pyrolysis of melamine at 600 °C, leading to a slight red-shift of the absorption band edge for nanohybrid NPC-TiO2 1. In addition, the in-situ formation and grafting of plasmonic AuAg NPs at the surface of NPC sheets and in close contact with TiO2 NPs leads to AuAg-NPC-TiO2 nanohybrids 2−3. These nanohybrids showed superior photocatalytic performance for the degradation of ciprofloxacin under visible light irradiation, compared to pristine P25 TiO2 NPs or to AuAg-PVP-TiO2 nanohybrid 4 in which polyvinylpyrrolidone stabilized AuAg NPs were directly grafted to TiO2 NPs. The materials were characterized by transmission electron microscope (TEM), High Angle Annular Dark Field­Scanning Transmission Electron Microscopy­Energy Dispersive X-ray Spectroscopy HAADF-STEM-EDS, X-ray photoelectron spectroscopy and solid UV-vis spectroscopy. Moreover, the active species involved in the photodegradation of ciprofloxacin using AuAg-NCS-TiO2 nanohybrids were evaluated by trapping experiments to propose a mechanism for the degradation.

An organometallic approach for the preparation of Au-TiO2 and Au-g-C3N4 nanohybrids: improving the depletion of paracetamol under visible light.

The photocatalytic degradation of paracetamol (a common analgesic also known as acetaminophen) in ultrapure water with different photocatalytic systems was performed under ultraviolet or visible irradiation. The photocatalysts employed were: commercial Degussa-P25 TiO2 and Au-TiO2 under UVA irradiation (365 nm) and g-C3N4 and Au-g-C3N4 under visible light irradiation (low-power (4 × 10 W) white light LEDs), improving the effectiveness of degradation rates when the gold nanoparticles (Au NPs) were combined with the semiconductors. The nanostructured photocatalysts were synthesised and characterised by transmission electron microscope (TEM), UV-vis diffuse reflectance spectroscopy and, in the case of g-C3N4 photocatalysts by X-ray photoelectron spectroscopy (XPS). The influence of the pH in the depletion of paracetamol with g-C3N4 and visible light was evaluated. In addition, the stability and lifetime of the photocatalyst g-C3N4 in the degradation of paracetamol were studied.

Combination of Au-Ag Plasmonic Nanoparticles of Varied Compositions with Carbon Nitride for Enhanced Photocatalytic Degradation of Ibuprofen under Visible Light.

Au-Ag/g-C3N4 nanohybrids 2-3 were synthesized by the one-pot self-reduction of the organometallic precursor [Au2Ag2(C6F5)4(OEt2)2]n in the presence of graphitic carbon nitride (g-C3N4), leading to two populations of alloyed Au-Ag nanoparticles (NPs) of different size and composition on the surface of g-C3N4, i.e., Ag-enriched Au-Ag NPs of smaller size and Au-enriched Au-Ag NPs of larger size. The combination of these two types of plasmonic NPs with g-C3N4 semiconductor displays enhanced photocatalytic properties towards the degradation of ibuprofen under visible light by the increased charge carrier separation provided by the inclusion of the plasmonic NPs on g-C3N4.

Study of intermediate by-products and mechanism of the photocatalytic degradation of ciprofloxacin in water using graphitized carbon nitride nanosheets.

The photocatalytic degradation of the antibiotic ciprofloxacin in water was carried out with nanosheets of graphitic carbon nitride (g-C3N4) as catalyst and visible light irradiation using low-power (4 × 10 W) white light LEDs. The aim of this study was to identify the intermediate by-products formed during the degradation and to propose a pathway for CIP degradation. To achieve this goal, photocatalytically degraded CIP solutions were analysed by liquid chromatography coupled to high-resolution mass spectrometry using a QTOF instrument. The accurate mass and the MS/MS data of the detected ions allowed us to determine the elementary composition of eight by-products and to propose the chemical structures for seven of them. Three of these by-products have been reported for the first time and the elementary composition of a fourth one that had been wrongly reported in the literature was accurately established. CIP degradation followed a pseudo-first order kinetics with a pseudo-first order kinetic constant of 0.035 min-1. In addition, a study of the influence of several scavengers showed that only the presence of triethanolamine dramatically reduced the pseudo-first order kinetic constant (0.00072 min-1), pointing out that the reactive species were the holes produced in the catalyst. Finally, the main pathway of CIP degradation seems to be the attack to the piperazine group by ·OH radicals, following heterocycle breakup and the subsequent loss of two of its carbon atoms as CO2 molecules, and then defluorination, oxidation and cleavage of the cycles of this intermediate.

Photocatalytic degradation of ibuprofen in water using TiO2/UV and g-C3N4/visible light: Study of intermediate degradation products by liquid chromatography coupled to high-resolution mass spectrometry.

The photocatalytic degradation of ibuprofen with TiO2 nanoparticles (NPs) and UV light and with graphitic carbon nitride (g-C3N4) 2D nanosheets and visible light are proposed and compared as advanced oxidation treatments for the removal of ibuprofen in water. By-products formed with both photocatalytic systems have been tentatively identified based on the results of ultra-high-performance liquid chromatography coupled to high-resolution mass spectrometry, using a quadrupole-time of flight mass spectrometer in positive and negative ionization modes, which allowed to obtain the elementary composition of their precursors and fragment ions. The removal of ibuprofen and the by-product formation were studied at three pH values. Ibuprofen depletion followed pseudo fist-order kinetics with rate constants of 0.04, 1.0 and 0.0006 min-1 at pH 2.50, 5.05 and 12.04 for TiO2/UV and 0.03, 0.007 and 0.0005 min-1 at pH 2.51, 5.05 and 11.33 for g-C3N4/vis, respectively. Around eighteen by-products have been detected with slight differences between the two photocatalytic systems studied. The evolution of the main common by-products (tentatively identified as 1-(4-ethylphenyl)-2-methylpropan-1-one, 1-(4-isobutylphenyl)ethan-1-ol, 1-(4-ethylphenyl)-2-methylpropan-1-ol and 1(-4-acetylphenyl)-2-methylpropan-1-one) were monitored and the results were consistent with reaction pathways based on hydroxyl radical attacks following/followed by decarboxylation. Moreover, some by-products have been reported for the first time in the photocatalytic oxidation of ibuprofen.

Determination of cinnamaldehyde, carvacrol and thymol in feedstuff additives by pressurized liquid extraction followed by gas chromatography-mass spectrometry.

Specific blends of essential oils (BEOs) are promising substitutes for antibiotics to promote livestock performance and to reduce the incidence of intestinal disorders. Microencapsulation of BEOs has shown to improve their stability, bioavailability and to control their release rate once they are added to the feedstuff. The development and validation of a method for determining essential oil components such as carvacrol, thymol and cinnamaldehyde in a microencapsulated material used as feed additive is presented. Analytes were extracted from feed additives and feedstuff by pressurized liquid extraction (PLE) with methanol at 50°C for 5min. Methanol provided good recovery values and cleaner extracts than other polar organic solvents tested. However, for certain kind of composite additives ethyl acetate showed to be a better option because trans-cinnamaldehyde undergoes chemical reaction in methanol. Then PLE extracts were analysed by gas chromatography coupled to ion trap mass spectrometry in selected ion storage (SIS) mode. The analyte stability and the absence of analyte losses during the PLE process was checked by a recovery study. Also, the matrix effect was studied to assess accuracy. Recovery values were between 85 and 115% in most cases. Intra- and inter-day relative standard deviation values were less than 4 and 14%, respectively. Finally, the developed method was applied to the analysis of a microencapsulated feed additive, several composite feed additive samples containing microencapsulated BEOs and a spiked feedstuff, for quality control and in stability studies.

Synthesis, Photochemical, and Redox Properties of Gold(I) and Gold(III) Pincer Complexes Incorporating a 2,2':6',2"-Terpyridine Ligand Framework.

Reaction of [Au(C6F5)(tht)] (tht = tetrahydrothiophene) with 2,2':6',2"-terpyridine (terpy) leads to complex [Au(C6F5)(η(1)-terpy)] (1). The chemical oxidation of complex (1) with 2 equiv of [N(C6H4Br-4)3](PF6) or using electrosynthetic techniques affords the Au(III) complex [Au(C6F5)(η(3)-terpy)](PF6)2 (2). The X-ray diffraction study of complex 2 reveals that the terpyridine acts as tridentate chelate ligand, which leads to a slightly distorted square-planar geometry. Complex 1 displays fluorescence in the solid state at 77 K due to a metal (gold) to ligand (terpy) charge transfer transition, whereas complex 2 displays fluorescence in acetonitrile due to excimer or exciplex formation. Time-dependent density functional theory calculations match the experimental absorption spectra of the synthesized complexes. In order to further probe the frontier orbitals of both complexes and study their redox behavior, each compound was separately characterized using cyclic voltammetry. The bulk electrolysis of a solution of complex 1 was analyzed by spectroscopic methods confirming the electrochemical synthesis of complex 2.

Determination of plastic additives in packaging by liquid chromatography coupled to high resolution mass spectrometry.

A simple and sensitive analytical method for the determination of several plastic additives in multilayer packaging based on solid-liquid extraction (SLE) and ultra-high performance liquid chromatography (UHPLC) coupled to variable wavelength (VWD) and time of flight mass spectrometry (TOF-MS) detectors is presented. The proposed method allows the simultaneous determination of fourteen additives belonging to different families such as antioxidants, slip agents and light stabilizers, as well as two oxidation products in only 9min. The developed method was validated in terms of linearity, matrix effect error, detection and quantification limits, repeatability and intermediate precision. The instrumental method showed satisfactory repeatability and intermediate precision at concentrations closed to LOQ with RSDs less than 7 and 20%, respectively, and LODs until 5000 times more sensitive than other GC-FID and HPLC-VWD methods previously reported. Also, focused ultrasound solid-liquid extraction (FUSLE) was optimized and evaluated to extract plastic additives from packaging. Extraction results obtained by FUSLE and SLE were compared to those obtained by pressurized liquid extraction (PLE). All extraction methods showed excellent extraction efficiency for slip agents, however quantitative recovery of all analytes was achieved only by SLE with just 5ml of hexane for 10h. Finally, the selected method was applied to the analysis of packaging samples where erucamide, Irgafos 168, oxidized Irgafos 168, Irganox 1076 and Irganox 1010 were detected and quantified.

Analytical method for the determination and a survey of parabens and their derivatives in pharmaceuticals.

Exposure of humans to parabens is a concern due to the estrogenic activity of these compounds. Parabens are widely used as preservatives in some personal care products, foodstuffs and pharmaceuticals owing to their low cost, high water solubility and broad spectrum antimicrobial properties. Despite this, little is known on the occurrence of parabens in pharmaceutical products. In this study, a method based on solid-liquid or liquid-liquid extraction (SLE or LLE), and high performance liquid chromatography (HPLC) coupled with triple quadrupole tandem mass spectrometry (QqQ or MS/MS) was developed for the determination of six most frequently used parabens and four paraben derivatives (methyl- and ethyl-protocatechuates, and mono- and di-hydroxybenzoic acids) in pharmaceuticals. A sample-purification step involving solid phase extraction (SPE) was optimized for the analysis of solid and lipid-rich pharmaceuticals. To our knowledge, this is the first comprehensive report on the occurrence of parabens in pharmaceuticals. The developed method was applied for the analysis of 128 liquid/syrup, cream, solid, prescription or over-the counter (OTC) drugs collected from the USA and a few other countries in Europe and Asia. Although majority of the drugs analyzed in the study did not contain parabens, concentrations as high as 2 mg/g were found in some drugs. Methyl- and propyl- parabens were the frequently detected compounds. 4-Hydroxybenzoic acid was the major metabolite found in pharmaceutical products.

Use of microextraction by packed sorbents following selective pressurised liquid extraction for the determination of brominated diphenyl ethers in sewage sludge by gas chromatography-mass spectrometry.

In this work, a method based on selective pressurised liquid extraction followed by microextraction by packed sorbents (MEPS) for the determination of brominated diphenyl ethers (BDEs) in sewage sludge is presented. The factors affecting the MEPS procedure were optimised. Acetone:water (25:75) sPLE extracts were drawn-ejected 10 times through C18 cartridges at 5 µL s(-1). The cartridge was dried five times with 250 µL of air and the BDEs were eluted at 25 µL s(-1) with 100 µL of n-hexane that were directly injected at 13 µL s(-1) in the GC-MSMS system. Under these conditions, there were no carry-over effects. The method was characterised in terms of limits of detection, repeatability, intermediate precision and accuracy. The use of MEPS for the determination of BDEs in sewage sludge means an improvement of the limits of detection due to the preconcentration and clean-up performed before the injection of the whole elute in the PTV injector. The GC-MSMS LODs (25 pg mL(-1)) were improved with MEPS to less than 3 pg mL(-1). RSD less than 7% and recovery values from 92% to 102% were shown. Finally, the method was applied to the sPLE extract analyses of sewage sludge from several wastewater treatment plants in La Rioja. To our knowledge, this is the first time that the MEPS technique has been applied to the analysis of BDEs, and the first time that it has been used for the analysis of extracts from a solid sample.

Determination of perfluorinated alkyl acids in corn, popcorn and popcorn bags before and after cooking by focused ultrasound solid-liquid extraction, liquid chromatography and quadrupole-time of flight mass spectrometry.

An analytical method is proposed to determine ten perfluorinated alkyl acids (PFAAs) [nine perfluorocarboxylic acids (PFCAs) and perfluorooctane sulfonate (PFOS)] in corn, popcorn and microwave popcorn packaging by focused ultrasound solid-liquid extraction (FUSLE) and ultra high performance liquid chromatography (UHPLC) coupled to quadrupole-time of flight mass spectrometry (QTOF-MS/MS). Selected PFAAs were extracted efficiently in only one 10-s cycle by FUSLE, a simple, safe and inexpensive technique. The developed method was validated for microwave popcorn bags matrix as well as corn and popcorn matrices in terms of linearity, matrix effect error, detection and quantification limits, repeatability and recovery values. The method showed good accuracy with recovery values around 100% except for the lowest chain length PFAAs, satisfactory reproducibility with RSDs under 16%, and sensitivity with limits of detection in the order of hundreds picograms per gram of sample (between 0.2 and 0.7ng/g). This method was also applied to the analysis of six microwave popcorn bags and the popcorn inside before and after cooking. PFCAs contents between 3.50ng/g and 750ng/g were found in bags, being PFHxA (perfluorohexanoic acid) the most abundant of them. However, no PFAAs were detected either corn or popcorn, therefore no migration was assumed.

Fast determination of perfluorocompounds in packaging by focused ultrasound solid-liquid extraction and liquid chromatography coupled to quadrupole-time of flight mass spectrometry.

A focused ultrasound solid-liquid extraction (FUSLE) and liquid chromatography (HPLC) coupled to quadrupole-time of flight mass spectrometry (QTOF-MS/MS) based method is proposed to determine six perfluorocarboxylic acids (PFCA) and perfluorooctane sulfonate (PFOS) in food-contact packaging. FUSLE, a simple, inexpensive and fast extraction technique, has been carried out with just 8mL of ethanol in one cycle of only 10s. The whole method presented good repeatability and intermediate precision, with RSDs below 11% and 15%, respectively; limits of detection, with values between 0.5ng/g and 2.2ng/g, and successful recovery values, around 100% in all cases. The developed method has been validated and applied to the analysis of real food-contact packaging samples. FUSLE results have been compared to those obtained with pressurized liquid extraction (PLE) and no significant differences between them have been found. PFAA were detected in all the packaging samples analyzed, in a concentration range between 4ng/g and 29ng/g, being PFHpA (perfluoroheptanoic acid) the most abundant of them.

Focused ultrasound solid-liquid extraction of perfluorinated compounds from sewage sludge.

A method for the determination of perfluorocarboxylic acids (PFCAs) and perfluorooctanesulfonic acid (PFOS) in sewage sludge based on focused ultrasound solid-liquid extraction (FUSLE) and reverse-phase ultra-performance liquid chromatography (UPLC) coupled to quadrupole-time of flight mass spectrometry (QTOFMS) has been developed. FUSLE is a fast, low-cost and efficient extraction technique based on the application of high power focused ultrasonic waves using a micro-tip immersed directly in the extraction mixture. For the method development, the extraction solvent was studied and afterwards the factors affecting the extraction efficiency were optimised by means of a central composite design. Optimal FUSLE conditions were: 8 mL of acetonitrile as extraction solvent and an ultrasonic irradiation power of 65% for only 20s. Two extraction cycles were enough for the quantitative extraction of PFCs from sewage sludge. Limits of detection below 0.2 ng g(-1) (dry sewage sludge), relative standard deviation values less than 8% and recovery values between 69 and 104% were found for the target analytes. Finally, the method was applied to the analysis of sewage sludge samples from several wastewater treatment plants of La Rioja.

Determination of perfluorocompounds in popcorn packaging by pressurised liquid extraction and ultra-performance liquid chromatography-tandem mass spectrometry.

The development and characterisation of a method based on reverse-phase ultra-performance liquid chromatography (UPLC) coupled to a quadrupole-time of flight mass spectrometer (Q-TOF-MS) with negative electrospray ionisation (ESI) to determine perfluorinated compounds (PFCs) in packaging is presented in this paper. Analytes were quantitatively recovered from packaging with methanol in only one PLE cycle of 6 min at 100 °C. The UPLC allowed the successful separation of the studied PFCs in less than 4 min. The whole method presented good precision, with RSDs below 8%, LODs from 0.6 to 16 ng g(-1); and excellent recovery values, around 100% in all cases, were achieved. The PLE-UPLC-MS method was applied to the analysis of popcorn packaging for microwave cooking. Besides the most commonly studied PFCs: PFOA and PFOS, the presence of other perfluorocarboxylic acids (PFCAs) in popcorn packaging is evidenced in this work.

Determination of bisphenol-type endocrine disrupting compounds in food-contact recycled-paper materials by focused ultrasonic solid-liquid extraction and ultra performance liquid chromatography-high resolution mass spectrometry.

Focused ultrasonic solid-liquid extraction (FUSLE) and reverse-phase ultra performance liquid chromatography (UPLC) coupled to a quadrupole-time of flight mass spectrometer (Q-TOF-MS) was applied to the determination of bisphenol-type endocrine disrupting compounds (EDCs) in food-contact recycled-paper materials. Recycled paper is a potential source of EDCs. Bisphenol A (BPA), bisphenol F (BPF) and their derivatives bisphenol A diglycidyl ether (BADGE) and bisphenol F diglycidyl ether (BFDGE) are used for the production of epoxy resins employed in the formulation of printing inks. The FUSLE of bisphenol-type EDCs from packaging is reported for the first time. First, different extraction solvents were studied and methanol was selected. Then, the main FUSLE factors affecting the extraction efficiency (solvent volume, extraction time and ultrasonic irradiation power) were studied by means of a central composite design. The FUSLE conditions selected for further experiments were 20 ml of methanol at ultrasonic amplitude of 100% for 5s. Finally, the number of extraction cycles necessary for complete extraction was established in two. The analysis of the FUSLE extracts was carried out by UPLC-Q-TOF-MS with electrospray ionization and the determination of the four analytes took place in only 4 min. The FUSLE and UPLC-ESI-QTOF-MS method was validated and applied to the analysis of different food-contact recycled-paper-based materials and packaging. The proposed method provided recoveries from 72% to 97%, repeatability and intermediate precision under 9% and 14%, respectively, and detection limits of 0.33, 0.16, 0.65 and 0.40 µg/g for BPA, BPF, BADGE and BFDGE, respectively. The analysis of paper and cardboard samples confirmed the presence of EDCs in these packaging.

Focused ultrasound solid-liquid extraction and gas chromatography tandem mass spectrometry determination of brominated flame retardants in indoor dust.

This study presents a focused ultrasound solid-liquid extraction (FUSLE) and gas chromatography tandem mass spectrometry method for the determination of brominated diphenyl ethers (BDEs), from mono- to hexa-congeners, in indoor dust. This approach provided a simple, fast, and economical method. After the solvent extraction selection, the FUSLE conditions were studied using a central composite design. Finally, the number of extraction cycles was studied. The selected conditions were 8 mL of 3:1 n-hexane-acetone mixture as extraction solvent, at a power of 65% for 20 s. The proposed method allowed accurate determination of BDEs, with recovery values around 100% and detection limits between 0.05 and 0.8 ng g(-1). It also has advantages over other existing methods in terms of simplicity, analysis time, and solvent consumption. The analysis of several indoor dust samples showed high concentration values of BDEs 47, 99, 100, 153, and 154 in some of the samples, moreover, BDEs 47 and 99 were found in all samples.

Determination of UV filters in packaging by focused ultrasonic solid-liquid extraction and liquid chromatography.

A focused ultrasonic solid-liquid extraction (FUSLE) and high performance liquid chromatography (HPLC) with a diode array detector (DAD) is proposed for the determination of ten fat-soluble UV filters in packaging. FUSLE technique is relatively new and has been used for the extraction of a few analytes; such as polycyclic aromatic hydrocarbons and other organic pollutants. In this work, it has been demonstrated that FUSLE is a useful, fast and simple extraction methodology for UV filters because the complete extraction was carried out with just 6ml of tetrahydrofuran and in only one cycle of 30s. The developed method has been validated and applied to the analysis of polyethylene-based multilayer packaging samples. The FUSLE-based method allows the sensitive detection of most of the UV-filters in polyethylene, with limits of detection between 0.4 and 8.5ngmg(-1) (except for BDM). Intra and inter-day relative standard deviation values were below 5 and 14%, respectively, except for MBP. In addition, the proposed method was more efficient than tetrahydrofuran extraction under reflux for 2.5h for all the analytes except for EMT and BDM. Therefore, the developed method can be used to establish the absorption capability of different types of packaging and this information will be very useful in packaging selection.

Determination of brominated diphenyl ethers (from mono- to hexa- congeners) in indoor dust by pressurised liquid extraction with in-cell clean-up and gas chromatography-mass spectrometry.

This study presents a selective pressurised liquid extraction (PLE) and gas chromatography-mass spectrometry/mass spectrometry method for the determination of brominated diphenyl ethers (BDEs) in indoor dust. Selective PLE consisted of the addition of Florisil mixed with the sample in order to perform an in-cell clean-up. This approach provided a cleaner and almost colourless extract, ready to be injected in the gas chromatograph. The PLE conditions were studied using an experimental design, firstly a 4 x 3 x 2 multifactor categorical design to screen sorbent, solvent and temperature and then a central composite design to optimise sorbent mass, temperature and time. Finally, the number of extraction cycles was studied. The selected conditions were 4 g of Florisil all mixed with the sample and no additional clean-up sorbent layer, 1:1 n-hexane-dichloromethane, 60% flush volume, 40 degrees C, 1,500 psi, 2-min static time and one cycle. The proposed method allowed accurate determination of BDEs, with recovery values between 82% and 101% and detection limits between 0.06 and 0.24 ng g(-1). It also has advantages over other existing methods in terms of simplicity, automation, analysis time and solvent consumption.

Microwave-assisted oxidation of phosphite-type antioxidant additives in polyethylene film extracts.

Two oxidation methods for reducing the analysis time required to determine Irgafos 126 and Irgafos 168 by pressurised liquid extraction (PLE) and high-performance liquid chromatography (HPLC) were optimised and compared. Analyte oxidation was performed using sodium peroxodisulphate (SPD) as oxidation agent and two different heating methods: with a hotplate and a reflux apparatus; and with a microwave oven. The influence of variables, such as oxidation time, temperature and sodium peroxodisulphate concentration was studied using a central composite design in order to optimise experimental conditions. A temperature of 68 degrees C for 2.5h and a SPD concentration of around 6 x 10(-4)M were required for conventional oxidation, while a temperature of 120 degrees C for 30 min and a SPD concentration of 4 x 10(-4)M were found to be the best for microwave-assisted oxidation. After optimising the methods, their repeatability values were calculated and the two methods were applied to a solution containing other additives in order to check that they were not affected by the oxidation treatment and thus confirm that the methods could be used for oxidation of I126 and I168 in pressurised liquid extracts of polyethylene film samples before their determination by HPLC. Finally, the methods were applied to the analysis of antioxidants in polyethylene film samples.