Determination of BTEX in Water Samples with an SPME Hollow Fiber Coated Copper Wire

Rapid determination of volatile benzene derivatives and chlorobenzenes in goat's milk by HS-SPME-GC-MS/MS

A method for the determination of eight benzenes (BTEXs) and twelve chlorobenzenes (CBs) in goat's milk by headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS/MS) was developed. The study investigated the impact of various factors such as extraction fiber type, salt amount, equilibrium conditions, and desorption conditions on the outcomes. Target analytes were separated on a DB-HeavyWAX column and quantified using the external standard method. The results showed that the target compounds had a good linear relationship in the range of 0.01 ∼ 50 μg/L (R2 > 0.997), the limit of detection (LOD) was 0.003 ∼ 0.150 μg/L, and the limit of quantification (LOQ) was 0.01 ∼ 0.50 μg/L. The average recoveries were 82%-116% and the relative standard deviation (RSD) was 0.8%-17.3% under the three addition levels of 1×, 2×, and 10 × LOQ. In a survey of twenty goat's milk samples, only ethylbenzene, xylenes, cumene, chlorobenzene, and 1,4-dichlorobenzene were detected at levels exceeding their respective limits of quantification. The method was evaluated using two ecological scales (Eco-Scale), GAPI and AGREEN, to verify its environmental friendliness and applicability. This method is simple, green, and efficient, which provides a certain theoretical basis for the production and quality safety evaluation of dairy products.

Metabolic Profiling and Quantitative Analysis of Cerebrospinal Fluid Using Gas Chromatography-Mass Spectrometry: Current Methods and Future Perspectives

Cerebrospinal fluid is a key biological fluid for the investigation of new potential biomarkers of central nervous system diseases. Gas chromatography coupled to mass-selective detectors can be used for this investigation at the stages of metabolic profiling and method development. Different sample preparation conditions, including extraction and derivatization, can be applied for the analysis of the most of low-molecular-weight compounds of the cerebrospinal fluid, including metabolites of tryptophan, arachidonic acid, glucose; amino, polyunsaturated fatty and other organic acids; neuroactive steroids; drugs; and toxic metabolites. The literature data analysis revealed the absence of fully validated methods for cerebrospinal fluid analysis, and it presents opportunities for scientists to develop and validate analytical protocols using modern sample preparation techniques, such as microextraction by packed sorbent, dispersive liquid-liquid microextraction, and other potentially applicable techniques.

Determination of Monoaromatic Hydrocarbons in Water Samples by Nano-Liquid Chromatography using a Composite Carbon Nanotubes- Lauryl Polymethacrylate Capillary Monolithic Column

Background:

This work reports a green analytical method for the determination of organic environmental pollutants using nano-liquid chromatography with a self-made column for rapid, sensitive, inexpensive and efficient analysis of BTX pollutants in water. The applications of monolithic nanoscale columns for quantitative analysis of environmental real samples are very limited in the literature.

Methods:

A capillary column containing a composite of multi-walled carbon nanotubes incorporated into a lauryl methacrylate-co-ethylene dimethacrylate porous monolithic polymer was fabricated for the determination of BTX pollutants in real water samples.

Results:

Baseline separation was accomplished at 0.4 µL/min flow rate with UV-detection set at 208 nm. Under the optimum conditions, the calibration curves were validated over the range of 1.0-500 µg/L with R2 more than 0.9992. The detection limits of benzene, toluene, o-xylene and m/p-xylene were 0.25, 0.05, 0.075 and 0.05 µg/L, respectively. After a simple extraction process with a theoretical preconcentration factor equal to 200, the recovery values in Milli-Q, tap and sea water samples were found to be ranged from 84.85 to 97.84% with %RSD less than 7.5. Furthermore, we reported a comparison between our prepared composite column with a commercial C18 silica based column which is the most used in such analytical field. Each column demonstrated its advantages from different analytical aspects.

Conclusion:

The application of monolithic columns and nano-scale LC for routine analysis of environmental samples is very promising as the use of monolithic capillary columns offers several advantages over conventional scale particulate packed columns.

Use of flat-sheet membrane extraction with a sorbent interface for solvent-free determination of BTEX in water

An analytical method for solvent-free determination of benzene, toluene, ethylbenzene, and xylenes (BTEX) in water using flat-sheet membrane extraction with a sorbent interface (MESI) coupled to GC-MS was established by optimizing the flow rates of the donor (20 ml water) and acceptor (helium) phases and extraction temperature. BTEX compounds permeated through a nonporous silicone membrane and evaporated into the acceptor phase were purged into a cryofocusing trap (-30 °C) with helium gas. Enriched compounds were thermally desorbed into a capillary gas chromatograph and detected with a mass spectrometer. The optimum flow rates of the donor and acceptor phases were set at 1.5 and 55 ml min(-1), respectively, and the temperature of the membrane extraction module was maintained within the 28-30 °C range. The method as established showed low method detection limits (MDLs:∼0.1 μg l(-1)) and highly linear calibration curves (r(2)>0.998) for all of the four compounds. High repeatability (relative standard deviation <∼5%) and a reasonably high extraction recovery (62-78%), after a single pass of the sample through the extraction module, also were established. Further, the method's high compatibility with the purge and trap (P&T) method indicates its applicability to field measurement. Other advantages include rapidity, simplicity, and a ready extendibility to automated on-line monitoring.