Simple and rapid determination of phthalates using microextraction by packed sorbent and gas chromatography with mass spectrometry quantification in cold drink and cosmetic samples

A simple and rapid method using microextraction by packed sorbent coupled with gas chromatography and mass spectrometry has been developed for the analysis of five phthalates, namely, diethyl phthalate, benzyl‐n‐butyl phthalate, dicyclohexyl phthalate, di‐n‐butyl phthalate, and di‐n‐propyl phthalate, in cold drink and cosmetic samples. The various parameters that influence the microextraction by packed sorbent performance such as extraction cycle (extract–discard), type and amount of solvent, washing solvent, and pH have been studied. The optimal conditions of microextraction using C₁₈ as the packed sorbent were 15 extraction cycles with water as washing solvent and 3 × 10 μL of ethyl acetate as the eluting solvent. Chromatographic separation was also optimized for injection temperature, flow rate, ion source, interface temperature, column temperature gradient and mass spectrometry was evaluated using the scan and selected ion monitoring data acquisition mode. Satisfactory results were obtained in terms of linearity with R² >0.9992 within the established concentration range. The limit of detection was 0.003–0.015 ng/mL, and the limit of quantification was 0.009–0.049 ng/mL. The recoveries were in the range of 92.35–98.90% for cold drink, 88.23–169.20% for perfume, and 88.90–184.40% for cream. Analysis by microextraction by packed sorbent promises to be a rapid method for the determination of these phthalates in cold drink and cosmetic samples, reducing the amount of sample, solvent, time and cost.     

Measurement of bisphenol A in human serum by gas chromatography/mass spectrometry

The purpose of this study is to establish an easy and accurate method for the determination of bisphenol A (BPA) in the human serum. The samples were applied to the C₁₈ solid phase extraction (SPE) column for clean up of samples. The BPA is conjugated with tetrabutylammonium hydrogen sulfate as the counter ion in alkali solution. The ion paired BPA is moves from the aqueous phase to the organic phase as an ion paired extraction. BPA extracted from human serum were derivatized with pentafluorobenzyl bromide (PFBBr). The derivative was analyzed by gas chromatography (GC)/mass spectrometry (MS) using negative chemical ionization (NCI). The instrumental detection limit of BPA was 5 pg/ml (10 fg). The instrumental response between 0.01 and 100 pg/ml of BPA standards was linear (r²=0.998). The recovery of BPA spiked into human serum was 101.0±4.63 (1 pg/ml) and 100.9±3.75 (10 pg/ml), respectively. The concentration of BPA in the human serum from 20 individuals was 0.54 pg/ml.     

Fatty acid profiling of blood cell membranes by gas chromatography with mass spectrometry

Fatty acids, which are well‐known for their influence on human metabolism and signal transduction, are also a substantial component of cellular membranes and regulate the basic properties and functions of membranes. Owing to their multiple functions, fatty acid profiles of cell membranes are of great interest to those who are studying the relationship between membrane biochemical compositions and functions. A HCl‐catalyzed derivation method and a gas chromatography with mass spectrometry analysis method were developed to accurately profile the fatty acids in cell membranes of erythrocytes, leukocytes, and platelets. The detection limits of all 35 fatty acids ranged from 0.58 to 22 ng/mL and the limits of quantitation were between 2.1 and 72 ng/mL. Finally, the established method was used to profile the membrane fatty acids of 44 healthy volunteers from the north and south of China. Results revealed significant differences in the fatty acid profiles from the two regions, particularly those of the erythrocytes. This technique may be applied to cell membrane studies to generate new biological hypotheses concerning fatty acid composition and membrane functions as well as to construct related disease profiles.     

Analysis of pesticide residues in tobacco with online size exclusion chromatography with gas chromatography and tandem mass spectrometry

An ultrasensitive method for the simultaneous analysis of pesticides residues in tobacco was developed with online size exclusion chromatography with gas chromatography and tandem mass spectrometry. Tobacco samples were extracted with the solvent mixture of cyclohexane and acetone (7:3, v/v) and centrifuged. Then, the supernatant liquors were injected directly into the online size exclusion chromatography with gas chromatography and tandem mass spectrometry without any other purification procedures after being filtered with a 0.22 μm organic phase filter. The matrix interferences were effectively removed and recoveries of most pesticides were in the range of 72–121%. Especially, for chlorothalonil, the analysis efficiency of this method was much more favorable than that of the general method, in which dispersive solid‐phase extraction was used as an additional purified procedure. In addition, the limits of quantitation of this method were from 1 to 50 μg/kg. Therefore, a rapid, cost‐effective, labor‐saving method was proposed in the present work, which was suitable for the analysis of 41 pesticide residues in tobacco.     

Advanced analytical techniques for the extraction and characterization of plant‐derived essential oils by gas chromatography with mass spectrometry

In recent years, essential oils have received a growing interest because of the positive health effects of their novel characteristics such as antibacterial, antifungal, and antioxidant activities. For the extraction of plant‐derived essential oils, there is the need of advanced analytical techniques and innovative methodologies. An exhaustive study of hydrodistillation, supercritical fluid extraction, ultrasound‐ and microwave‐assisted extraction, solid‐phase microextraction, pressurized liquid extraction, pressurized hot water extraction, liquid–liquid extraction, liquid‐phase microextraction, matrix solid‐phase dispersion, and gas chromatography (one‐ and two‐dimensional) hyphenated with mass spectrometry for the extraction through various plant species and analysis of essential oils has been provided in this review. Essential oils are composed of mainly terpenes and terpenoids with low‐molecular‐weight aromatic and aliphatic constituents that are particularly important for public health.     

Identification of oxygenated polycyclic aromatic hydrocarbons in diesel particulate matter by capillary gas chromatography and capillary gas chromatography/mass spectrometry

Summary Using a two-step liquid chromatographic separation on normalphase cartridges, crude extracts of diesel particulate matter can be separated without time-consuming sample handling into special fractions which mainly contain slightly-polar oxygenated polycyclic aromatic hydrocarbons (oxy-PAH) and nitrated polycyclic aromatic hydrocarbons (nitro-PAH). Subsequent analysis was by fused-silica capillary gas chromatography on a SE54 column along with flame-ionisation (GC/FID) and positive-ion electron-impact mass spectrometric detection (GC/MS) respectively. A number of individual oxy-PAH belonging to four different chemical classes (ketones, quinones, anhydrides and aldehydes) and several individual nitro-PAH were characterized by their retention times and mass spectra. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

A novel quantitation method for phthalates in air using a combined thermal desorption/gas chromatography/mass spectrometry application

In this study, a novel quantitation method was developed to facilitate the simple and effective sampling and analysis of phthalates in air based on a sorbent tube-thermal desorption-gas chromatography-mass spectrometry system combination. The performance of the thermal desorption-based analysis was assessed using three different sorbent combinations [1]: quartz wool (QW) [2], glass wool (GW), and [3] quartz wool plus Tenax TA (QWTN) in terms of relative recovery in reference to a direct injection method. There was no significant difference in the average recovery rate for seven target phthalates based on sorbent tube type (QW, 70.2 ± 4.28; GW, 73.2 ± 8.8; and QWTN, 72.5 ± 5.02%). However, the recovery rate of phthalates in each sorbent tube type was distingusihed by physicochemical properties of the target compound (e.g., molecular weight and boiling point). The recovery rate of the QW tube was high for dimethyl phthalate and diethyl phthalate compared to other sorbent tubes, while that of the GW tube exhibited greater values for dibutyl phthalate, benzyl butyl phthalate, di(2-ethylhexyl) adipate, di(2-ethylhexyl) phthalate, and di-n-octyl phthalate. The simple sorbent tube-thermal desorption approach is feasible for the quantitation of seven phthalates present at 0.45–24.5 ng m⁻³ levels in actual air samples (20 L).     

Identification of 19 phthalic acid esters in dairy products by gas chromatography with mass spectrometry

A detection method for 19 kinds of phthalic acid ester compounds analyzed by n‐hexane/ether/acetonitrile 1:7:8 v/v/v mixed solvent extraction, quick, easy, cheap, effective, rugged, and safe purification and internal standard method of quantitative gas chromatography with mass spectrometry was established. This method can effectively remove interfering materials, such as lipids, fatty acids, and pigments, from dairy products. The 19 kinds of phthalic acid ester compounds were within a 0.025–0.2 mg/kg range, the recovery rate was 65.2–125.7%, relative standard deviation was 7.9–15.4% (n = 6), and the limit of detection was 0.005–0.02 mg/kg. Concentrations of the 19 kinds of phthalic acid ester compounds ranged between 0.01 and 0.12 mg/kg in ten dairy materials and 20 dairy products. The established method is simple, rapid, accurate, and highly sensitive.     

Gas chromatography with mass spectrometry for the quantification of ethylene glycol ethers in different household cleaning products

A rapid and simple procedure is reported for the determination of six ethylene glycol ethers in cleaning products and detergents using gas chromatography with mass spectrometry. The analytes were extracted from 2.0 g samples in acetonitrile (3 mL) and the extract was submitted to a clean‐up step by QuEChERS method, using a mixture containing 0.3 g magnesium sulfate, 0.15 g primary/secondary amine, and 0.05 g C₁₈. The clean acetonitrile extract (1 μL) was injected into the chromatographic system. No matrix effect was observed, so the quantification of the samples was carried out against external standards. Detection limits were in the range 3.0–27 ng/g for the six ethylene glycol ethers. The recoveries obtained, using the optimized procedure, were in the 89.4–118% range, with relative standard deviations lower than 14%. Twenty‐three different household cleaning products, including glass cleaner, degreaser, floor, softeners, and clothes and dishwashing detergents, were analyzed. Large interindividual variations were observed between samples and compounds.     

Determination of phthalate esters in Chinese spirits using isotope dilution gas chromatography with tandem mass spectrometry

Phthalate esters are additives used in polyvinylchloride and are found as contaminants in many food products. An isotope dilution mass spectrometry technique has been developed for accurate analysis of 16 phthalate esters in Chinese spirits by adopting the 16 corresponding isotope‐labeled phthalate esters. The ethanol in the spirit sample was first removed by heating with a water bath at 100°C with a stream of nitrogen, after which the residue was extracted with n‐hexane twice. The phthalates collected were identified and quantified by gas chromatography with tandem mass spectrometry in multiple reaction monitoring mode. The spiking recoveries of 16 analytes ranged from 94.3 to 105.3% with relative standard deviation values of <6.5%. The detection limits for 16 analytes were <10.0 ng/g. The expanded relative uncertainties were from 3.0 to 14%. A survey was performed on Chinese spirits from the market. Six of the nine analyzed samples were contaminated by phthalates. Di‐n‐butyl phthalate and di‐2‐ethylhexyl phthalate showed higher detection frequency and concentrations. This isotope dilution gas chromatography with tandem mass spectrometry method is simple, rapid, accurate, and highly sensitive, which qualifies as a candidate reference method for the determination of phthalates in spirits.     

Headspace solid-phase microextraction of oil matrices heated at high temperature and phthalate esters determination by gas chromatography multistage mass spectrometry

A solvent-free analytical approach based on headspace solid-phase microextraction (SPME) of oil matrices heated at high temperatures coupled to gas chromatography with mass spectrometry detector (GC-ion trap) has been developed for the determination of phthalic acid esters (PAEs) in oil matrices without sample manipulation. For this study, three fibers, i.e., 85 μm-polyacrylate (PA), 50/30 μm-divinylbenzene-carboxen-polydimethylsiloxane (DVB/CAR/PDMS) and 100 μm-polydimethylsiloxane (PDMS) were tested. Variables affecting the SPME headspace composition such as incubation sample temperature, sample incubation time and fiber exposition time were optimized. The optimal values found were 250 °C for sample incubation temperature and 30 min for incubation and extraction time. PA fiber was not suitable for the lightest polar phthalates which showed poor extraction and repeatability values. PDMS fiber had very poor response for some of the heavier and non-polar phthalates, whereas DVB/CAR/PDMS fiber showed the best response and repeatability values for the majority of the phthalates studied. The main benefit of the analytical method proposed is the absence of sample manipulation and hence avoidance of possible contamination coming from glassware, environment, solvents and samples.     

Impact of gas chromatography and mass spectrometry combined with gas chromatography and olfactometry for the sex differentiation of Baccharis articulata by the analysis of volatile compounds

The Baccharis genus has more than 400 species of aromatic plants. However, only approximately 50 species have been studied in oil composition to date. From these studies, very few take into consideration differences between male and female plants, which is a significant and distinctive factor in Baccharis in the Asteraceae family. Baccharis articulata is a common shrub that grows wild in south Brazil, northern and central Argentina, Bolivia, Paraguay and Uruguay. It is considered to be a medicinal plant and is employed in traditional medicine. We report B. articulata male and female volatile composition obtained by simultaneous distillation–extraction technique and analyzed by gas chromatography with mass spectrometry. Also, an assessment of aromatic differences between volatile extracts was evaluated by gas chromatography with olfactometry. The results show a very similar chemical composition between male and female extracts, with a high proportion of terpene compounds of which β‐pinene, limonene and germacrene D are the main components. Despite the chemical similarity, great differences in aromatic profile were found: male plant samples exhibited the strongest odorants in number and intensity of aromatic attributes. These differences explain field observations which indicate differences between male and female flower aroma, and might be of ecological significance in the attraction of pollinating insects.     

Accurate quantification of endogenous androgenic steroids in cattle's meat by gas chromatography mass spectrometry using a surrogate analyte approach

Determination of endogenous steroids in complex matrices such as cattle's meat is a challenging task. Since endogenous steroids always exist in animal tissues, no analyte-free matrices for constructing the standard calibration line will be available, which is crucial for accurate quantification specially at trace level. Although some methods have been proposed to solve the problem, none has offered a complete solution. To this aim, a new quantification strategy was developed in this study, which is named “surrogate analyte approach” and is based on using isotope-labeled standards instead of natural form of endogenous steroids for preparing the calibration line. In comparison with the other methods, which are currently in use for the quantitation of endogenous steroids, this approach provides improved simplicity and speed for analysis on a routine basis. The accuracy of this method is better than other methods at low concentration and comparable to the standard addition at medium and high concentrations. The method was also found to be valid according to the ICH criteria for bioanalytical methods. The developed method could be a promising approach in the field of compounds residue analysis.     

气质联用法测定医用橡皮塞中防老剂BHT

橡胶具有高弹性,可获得良好的密封性能和再密封性能。通常在橡胶中加入少量的防老剂如2,6-二叔丁基对甲酚(BHT)来延缓其氧化过程,延长使用寿命。目前,化妆品、食品、塑料等制品中BHT的含量已受到严格的控制。在注射药剂的过程中,医用橡皮塞中的BHT会随着药液直接流人人体静脉,过量的BHT会给人体健康带来隐患。本文采用气质联用法测定了医用橡皮塞中的BHT。含量,采用总离子流图给出的质谱图进行定性,以m／z205作为选择离子,选择离子法(SIS)定量。     

Determination of priority pesticides in baby foods by gas chromatography tandem quadrupole mass spectrometry

A gas chromatography-tandem quadrupole mass spectrometry (GC-MS/MS) method for the determination of twelve priority pesticides, and transformation products (e.g. metabolites) specified in the EU Baby Food Directive 2003/13/EC is described. Prior to GC-MS/MS analysis, co-extractives were removed from acetonitrile extracts using dispersive solid phase extraction with octadecyl (200 mg) and primary secondary amine (50 mg) sorbents. The clean up proved essential for the satisfactory long-term chromatographic performance during the analysis of a range of representative commercially pre-prepared baby food samples. Extracts spiked with pesticides at 1-8 microg kg(-1), yielded average recoveries in the range 60-113% with relative standard deviations less than 28%.     

Determination of phthalate esters in vegetable oils using direct immersion solid-phase microextraction and fast gas chromatography coupled with triple quadrupole mass spectrometry

Phthalates are a group of synthetic compounds mainly used as plasticizers, which have been classified as endocrine-disrupting chemicals and potential human-cancer causing agents. They can be found in high amounts in foods, deriving mainly from plastic packaging. The analytical determination of these compounds is very challenging since they are ubiquitous. Therefore, minimization of sample manipulation is highly desirable.     

Identification of volatiles from pineapple (Ananas comosus L.) pulp by comprehensive two-dimensional gas chromatography and gas chromatography/mass spectrometry

Combining qualitative data from the chromatographic structure of 2-D gas chromatography with flame ionization detection (GC×GC-FID) and that from gas chromatography-mass spectrometry (GC/MS) should result in a more accurate assignment of the peak identities than the simple analysis by GC/MS, where coelution of analytes is unavoidable in highly complex samples (rendering spectra unsuitable for qualitative purposes) or for compounds in very low concentrations. Using data from GC×GC-FID combined with GC/MS can reveal coelutions that were not detected by mass spectra deconvolution software. In addition, some compounds can be identified according to the structure of the GC×GC-FID chromatogram. In this article, the volatile fractions of fresh and dehydrated pineapple pulp were evaluated. The extraction of the volatiles was performed by dynamic headspace extraction coupled to solid-phase microextraction (DHS-SPME), a technique appropriate for slurries or solid matrices. Extracted analytes were then analyzed by GC×GC-FID and GC/MS. The results obtained using both techniques were combined to improve compound identifications.     

Determination of three kinds of banned drugs in milk powder by hybrid solid‐phase extraction purification combined with gas chromatography and mass spectrometry

A gradient clean‐up method for the quantification of five kinds of banned drugs (two hormones, two sedatives, and one chloramphenicol) in milk powder was developed. We used the combination of solid‐phase extraction purification with gas chromatography and mass spectrometry. Milk powder was initially hydrolyzed by β‐glucuronidase/arylsulfatase, and then the hydrolyzed solution was concentrated and purified using a C₈ and cation resin solid‐phase extraction column. To isolate hormones and chloramphenicol drugs, products from the previous step were diluted with methanol and further purified using a silica and diatomite solid‐phase extraction column. After derivatization, the drugs were analyzed by gas chromatography with mass spectrometry, and the hydrolyzed solution was diluted with 5% ammoniated methanol to purify sedatives before gas chromatography with mass spectrometry analysis. Results showed that after adding the banned drugs at concentrations of 0.3–10.0 μg/kg, the average recovery range was 78.2–97.3% with relative standard deviations of 5.3–12.5%. The limit of quantification of the banned drugs (S/N ≥ 10) was 0.3–5.0 μg/kg, whereas the limit of detection (S/N ≥ 3) was 0.1–2.0 μg/kg. The solid‐phase extraction gradient purification system was simple, rapid, and accurate, and could satisfy the detection requirements of hormone, sedatives, and chloramphenicol drugs when used together with gas chromatography and mass spectrometry.     

Determination of gaseous carbonyl compounds by their pentafluorophenyl hydrazones with gas chromatography/mass spectrometry

A sensitive and reliable method has been developed for the simultaneous determination of 20 airborne carbonyl compounds in the C₁-C₁₀ range. The carbonyls were collected onto solid sorbent coated with pentafluorophenyl hydrazine (PFPH), followed by solvent extraction and gas chromatographic (GC)/mass spectrometric (MS) analysis of the PFPH derivatives. The sorbent is packed into two separate sections in a glass sampling tube. The two-section design allows convenient checking of collection efficiency and breakthrough. The sampling tube, with a coating amount of 971 nmol PFPH per 100 mg Tenax TA and operated at a sampling flow rate of 80 mL min⁻¹, collects the 20 carbonyls with efficiencies above 95%. Hexane extracts the collected carbonyls in their PFPH derivatives in the sampling tube with better than 95% extraction efficiency. It is necessary to let the sampling tube sit at ambient temperature for 3 days before solvent extraction to ensure complete derivatization of the carbonyls. The limits of detection (LODs) of the tested carbonyls are in the range of 3.7-11.6 ng per sample. The method has been field-tested both in ambient environment and in an indoor environment from burning mosquito-repellent incense. Eighteen carbonyls were detected in the ambient air samples with the exception of o-tolualdehyde and m-tolualdehyde, while all the 20 target carbonyls were found in the incense smoke. Compare field test with classical DNPH-HPLC/UV method, good agreement exited between the two methods for lower molecular carbonyls but PFPH method is found to be a better analytical method for determination of high molecular weight carbonyls.     

固相萃取-气相色谱-质谱联用法测定水中的硝基苯类有机污染物的分析方法研究

建立了固相萃取、毛细柱气相色谱-质谱、内标标准曲线法使用选择离子(SIM)监测采集数据定量分析水中硝基苯类有机化合物的分析方法.通过对固相萃取柱的选择、固相萃取条件(样品溶液的pH、上样速率、上样体积、洗脱液选择及配比)的优化,得出了最佳实验条件.始漏体积达1.5 L.回收率大于80%.检出限为0.015～0.045 μg/L.RSD在1.1%～5.9%之间.