A fast and sensitive high performance liquid chromatography with atmospheric pressure chemical ionization tandem mass spectrometry (HPLC-APCI-MS/MS) method to identify and quantify oxysterols, phytosterols and non-cholesterol sterols at the pico-molar concentration level in human serum in only one run was developed in this study. This method allows the simultaneous separation and quantitation of individual phytosterols, cholesterol precursors and oxidized derivatives of cholesterol without a derivatization step in a single run, thus providing a more confident quantitation of sterols in serum. After saponification, solid-phase extraction (SPE) used as a clean-up step and HPLC separation, detection by MS was developed using APCI and multiple ion monitoring modes. This method employs reversed-phase C₁₈ SPE cartridges and serum calibrators, as well as isotopically labelled cholesterol as an internal standard added before sample processing. The time consumed for a single sample is reduced from the 4 hours of conventional sterol analysis to 1 hour including the chromatographic run time. The method has been evaluated by analyzing a certified cholesterol sample as well as by comparison to other two methods used as reference, based on GC and enzymatic reaction, respectively. Serum from 14 individuals was successfully analyzed. Detection limits for oxysterols, phytosterols and non-cholesterol sterols, all determined in a single run in small serum volumes, were between 0.47 and 1.69 pM. Intra-day precision was <7% for all sterols in in-house-made lipoprotein-deficient serum. The limits of detection showed high sensitivity with very good intraday- and interday-precision for all sterols. The recoveries of the phytosterols, cholesterol precursors and cholestanol ranged from 77% to 92%. These analytical parameters provide a reliable and reproducible method for the identification and quantitation of human sterols.

An automated method for analyzing free non-cholesterol sterols in human serum using online solid phase extraction-liquid chromatography-mass spectrometry is proposed herein. The method allows the determination of three phytosterols (sitosterol, stigmasterol and campesterol) and two cholesterol precursors (desmosterol and lanosterol). The analysis of sterols in human serum is critical in the study of cholesterol-related disorders, such as inherited familial hypercholesterolemias. Special effort was made to isolate the analytes from the serum lipoproteins, their natural conveyance through the bloodstream. The sample treatment consisted of a Bligh-Dyer extraction followed by dilution of the extract. This treatment allowed the sample to be injected into the online system and ensured the correct detection of the analytes, while avoiding the matrix effects commonly related to serum samples. The analytical performance showed linear ranges that covered two orders of magnitude, with correlation coefficients above 0.99. Limits of detection and quantification ranged from 0.2 ng/mL to 13 ng/mL and from 1.0 ng/mL to 43 ng/mL, respectively. Recovery when spiking serum with a half or a tenth of the average concentration reported in human serum ranged from 99% to 111% and from 102% to 120%, respectively. Intra-day precision and inter-day precision were below 20%.

Organochlorine compounds were measured in the air of two different sites. In the air of a Spanish National Park in the Pyrenees Mountains (Ordesa and Monteperdido) and in the surroundings of an industrial waste dump (Sabiñánigo near to Huesca). The air sampling was carried out with a high volume air sampler, using polyurethane foam (PUF) and glass fiber filters (GFF) to collect both the gas phase and the particulate phase of these compounds. Recovery data of the analytical procedure as well as breakthrough values are shown. γ-HCH. á-HCH, á-endosulfan and hexachlorobenzene were found in all National Park samples in the range from 70 to 3076 pg/m³. The chlorobenzenes had the highest concentrations ([Sgrave]CB=1551–3512 ng/m³) in the dumping site. α-HCH and y-HCH were found in the range from 28 to 78 ng/m³.

Different clean‐up procedures for PCB analysis are compared. Sulphuric acid‐silica gel column was the most effective clean‐up procedure to determine PCBs in mineral waste oils.

The aim of this work is to develop and optimize a non-targeted screening (NTS) method based on Arrow SPME for the characterization of volatile and semi-volatile compounds in recycled polyethylene terephthalate (PET) and polyolefins (POs). Both, solid materials and migration extracts obtained with food simulants (ethanol 10 %, ethanol 95 %, and acetic acid 3 %) were studied. The method development considered both headspace and direct immersion extraction modes to assess their relative performance and applicability depending on the sample type. To achieve robust optimization, a RSM based on CCD was employed, allowing the evaluation of the effects and interactions of key variables such as extraction time, temperature, and sample amount. Separate designs were constructed for each sample type, acknowledging their distinct behaviour and matrix effects. A mixture of 15 selected Food Contact Materials (FCM) analytes showed that SPME Arrow improved sensitivity, with response factors 7-14 % higher than traditional SPME. It also demonstrated superior linearity (R² > 0.990 for all analytes) and lower variability, whereas conventional SPME showed acceptable linearity for only a limited number of compounds.