Characterization of key odor-active compounds in sweet Petit Manseng (Vitis vinifera L.) wine by gas chromatography-olfactometry, aroma reconstitution, and omission tests.

Petit Manseng (Vitis vinifera L.) has become a popular variety in China for the production of semisweet and sweet wines. However, few studies focused on investigating the molecular odor code of its key odorants. In this study, the key odor-active compounds of Chinese sweet Petit Manseng wine were identified by gas chromatography-olfactometry (GC-O) and gas chromatography-mass spectrometry (GC-MS). Fifty-five odorous zones were sniffed and identified by application of aroma extraction dilution analysis on a distillate prepared by liquid-liquid extraction and solvent-assisted flavor evaporation. Among them, isoamyl alcohol, ethyl octanoate, isovaleric acid, (E)-ß-damascenone, and phenylethanol particularly displayed with highest flavor dilution factors above 1024. The quantification of volatiles by headspace solid-phase microextraction coupled with GC-MS and GC coupled with triple quadrupole MS/MS and a calculation of odor activity values (OAVs) indicated 23 volatiles with OAVs above 1. Ethyl hexanoate showed the highest OAV with 208.8, followed by (E)-ß-damascenone (189.0), 3-mercaptohexanol (60.3), isoamyl acetate (45.4), and furaneol (40.1). The aroma of the sweet wine was successfully reconstituted by combining 42 aroma compounds in a model wine solution. 3-Mercaptohexanol, (E)-ß-damascenone, furaneol, γ-octalactone + γ-decalactone + γ-hexalactone, and ethyl cinnamate had important influence on the aroma of sweet Petit Manseng wine assessed by omission tests. Moreover, the discrimination of wines from three regions was successfully achieved by partial least squares discriminant analysis based on quantitative results of key odorants. 3-Mercaptohexanol was considered as the most responsible for the region discrimination and had highest concentrations in Petit Manseng wines from Jiaodong Peninsula. PRACTICAL APPLICATION: Understanding of the knowledge in key odorants of Petit Manseng wines could be useful to improve wine quality through viticultural and enological practices.

Effect of polyvinylpolypyrrolidone treatment on rosés wines during fermentation: Impact on color, polyphenols and thiol aromas.

Fining treatment with polyvinylpolypyrrolidone (PVPP) is often used during winemaking of rosé wines. It can modulate the intensity and hue of their pink color and prevent some organoleptic degradations. In this paper, the effect of PVPP treatments on rosé wine during fermentation was investigated by measuring color, polyphenol content and thiol aromas. As expected, colorimetry results showed a decrease in color, indicating some adsorption of anthocyanins and other pigments. This was confirmed by UPLC-ESI-MS/MS analyses. Specific adsorption of certain families of polyphenols was evidenced. Flavonols, flavanols and anthocyanins, especially coumaroylated anthocyanins were preferentially adsorbed by PVPP. The thiol content (3-sulfanylhexyl acetate (3SHA) and 3-sulfanylhexan-1-ol (3SH)) was usually higher after PVPP treatments, in a dose dependent manner. A possible explanation is that the partial adsorption of some polyphenols at an early stage of fermentation would later limit the amount of quinone compounds able to trap thiol aromas.

Volatile organic compounds from pachyrhizus ferrugineus and pachyrhizus erosus (Fabaceae) leaves / Compuestos orgánicos volátiles de las hojas de pachyrhizus ferrugineus y pachyrhizus erosus (Fabaceae)

In México, Pachyrhizus erosus (Fabaceae) commonly called "jícama", is widely known for its edible tubers. It is cultivated since the pre-Columbian period, and the powdered seeds have been used for the treatment of mange, lice, and fleas, due to their content of rotenone, a well-known insecticidal compound. On the other hand, P. ferrugineus, a wild species can only be found in the Tropical Forests, and has no commercial value. It is known that plants release volatile organic compounds (VOCs) showing qualitative and quantitative differences if are wild or cultivated. VOCs are also involved as repelling or attracting chemical signals to insect herbivores, and their natural enemies. Until now, the VOCs of the leaves of P. erosus and P. ferrugineus have not been investigated. In the present contribution the VOCs of both species were characterized by headspace solid-phase (HS-SPME) extraction and gas chromatography-mass spectrometry (GC-MS-TOF). In P. erosus 21 VOCs were found, being the most abundant: cyclohexanone (32.8 percent), 3-hexen-1-ol (Z) (32.7 percent), 3-hexenal (Z) (10.5 percent). The majoritarian compounds were C6 or C5 derivatives In P. ferrugineus, the most abundant VOCs were: 5-hexene-1-ol acetate (51.5 percent), undecanal (22.4 percent), 2-hepten-1-al (14.5 percent). The majoritarian compounds were C6, C7 or C11 derivatives.

En México, Pachyrhizus erosus (Fabaceae) es llamada comúnmente "jícama" y es conocida por sus tubérculos comestibles. Se ha cultivado desde el período pre-Colombino y las semillas se han utilizado para el tratamiento tópico de la sarna, piojos, pulgas; las semillas contienen rotenona, un compuesto insecticida. Por otra parte, P. ferrugineus solo está presente en estado silvestre en los bosques tropicales y carece de valor comercial. Se sabe que las plantas liberan compuestos orgánicos volátiles (COV) y muestran diferencias cualitativas y cuantitativas dependiendo, si son silvestres o cultivadas. Los COV también son señales químicas atrayentes o repelentes de los insectos herbívoros y a sus enemigos naturales. Hasta ahora, los COV en las hojas de P. erosus y P. ferrugineus no han sido investigados. En el presente trabajo, los COV se identificaron mediante la microextracción (HS-SPME) en fase sólida, e identificados por cromatografía de gases acoplada a espectrometría de masas (GC-MS-TOF). En P. erosus se encontraron 21 COV, siendo los más abundantes: ciclohexanona (32.8 por ciento), 3-hexen-1-ol (Z) (32.7 por ciento) y 3-hexenal (Z) (10.5 por ciento). Los compuestos mayoritarios son C6 y C5. En P. ferrugineus los más abundantes fueron: 5-hexen-1-ol acetato (51.5 por ciento), undecanal (22.4 por ciento) y 2-hepten-1-al (14.5 por ciento). Los compuestos mayoritarios son C6, C7 o C11.

Direct immersion solid-phase microextraction with gas chromatography and mass spectrometry for the determination of specific biomarkers of human sweat in melted snow.

To provide a reliable tool for investigating diffusion processes of the specific components of the human odor 3-hydroxy-3-methylhexanoic acid and 3-methyl-3-sulfanylhexan-1-ol through the snowpack, we developed and optimized an analytical method based on direct immersion solid-phase microextraction followed by gas chromatography with mass spectrometry. Direct immersion solid-phase microextraction was performed using polyacrylate fibers placed in aqueous solutions containing 3-hydroxy-3-methylhexanoic acid and 3-methyl-3-sulfanylhexan-1-ol. After optimization, absorption times of 120 min provided a good balance to shorten the analysis time and to obtain suitable amounts of extractable analytes. The extraction efficiency was improved by increasing the ionic strength of the solution. Although the absolute extraction efficiency ranged between 10 and 12% for 3-hydroxy-3-methylhexanoic acid and 2-3% for 3-methyl-3-sulfanylhexan-1-ol, this method was suitable for analyzing 3-hydroxy-3-methylhexanoic acid and 3-methyl-3-sulfanylhexan-1-ol concentrations of at least 0.04 and 0.20 ng/mL, respectively. The precision of the direct immersion solid-phase microextraction method ranged between 8 and 16%. The variability within a batch of six fibers was 10-18%. The accuracy of the method provided values of 88-95 and 86-101% for 3-hydroxy-3-methylhexanoic acid and 3-methyl-3-sulfanylhexan-1-ol, respectively. The limit of detection (and quantification) was 0.01 ng/mL (0.04 ng/mL) for 3-hydroxy-3-methylhexanoic acid and 0.06 ng/mL (0.20 ng/mL) for 3-methyl-3-sulfanylhexan-1-ol. The signal versus concentration was linear for both compounds (r(2) = 0.973-0.979). The stability of these two compounds showed that 3-hydroxy-3-methylhexanoic acid was more stable in water than 3-methyl-3-sulfanylhexan-1-ol. We applied the method to environmental samples in correspondence with an olfactory target buried previously.

Identification of signature volatiles to discriminate Candida albicans, glabrata, krusei and tropicalis using gas chromatography and mass spectrometry.

Oral candidiasis is the most frequent fungal infection of the oral cavity. Clinical diagnoses require mycological confirmation, which is time-consuming in case of culture testing. The aim of the study was to identify signature volatiles to develop a chairside breath test to diagnose oral candidiasis. Headspaces above Candida albicans, glabrata, tropicalis, krusei cultures, and growth media as control were analysed after eight and 24 h using offline gas chromatography and mass spectrometry. The identification of signature volatiles was assisted using various microbial databases. Retrieved volatile patterns enabled Candida species discrimination in vitro. For C. albicans 3-methyl-2-butanone and styrene and for C. krusei a combination of p-xylene, 2-octanone, 2-heptanone and n-butyl acetate were found to be specific. 1-hexanol was found in C. tropicalis, but is emitted by a variety of other microorganisms. C. glabrata was characterised through the absence of these volatiles. The development of a breath test is a promising approach in confirming suspicions of oral candidiasis. To confirm the retrieved results in vivo, breath tests in affected and healthy subjects have to be performed.

Derivatization of pinacolyl alcohol with phenyldimethylchlorosilane for enhanced detection by gas chromatography-mass spectrometry.

A derivatization procedure for the qualitative gas chromatography-mass spectrometry (GC-MS) analysis of pinacolyl alcohol (PA) that employs phenyldimethylchlorosilane (PhDMClS) and the promoter N-methylimidazole is described. While PA, underivatized, can be detected using conventional gas chromatographic methods, its polarity and low boiling point make its detection in complex matrices challenging. The silylation procedure described herein generates a PA-derivative exhibiting an increased on-column retention time, thus shifting its GC-MS signal away from commonly encountered, volatile, interfering analytes. Derivatized PA could be distinguished from other PhDMClS-derivatized isomeric alcohols by its unique retention time and mass spectrum. The derivatization was demonstrated to perform well in the GC-MS analysis and identification of PA in samples from Proficiency Tests administered by the Organisation for the Prohibition of Chemical Weapons (OPCW).

Investigation of volatile organic metabolites in lung cancer pleural effusions by solid-phase microextraction and gas chromatography/mass spectrometry.

Headspace solid-phase microextraction (HS-SPME) combined with gas chromatography/mass spectrometry (GC/MS) method was applied for the investigation of low molecular weight volatile organic metabolites (VOMs) in pleural effusion samples. Three important HS-SPME experimental parameters that influence extraction efficiency (fiber coating, extraction time and temperature of sampling) were optimized by a univariate optimization design. The highest extraction efficiency was obtained when sampling was performed at 50°C for 10min under agitation using a carboxen/polydimethylsiloxane (CAR/PDMS) fiber. A total of 36 volatile metabolites belonging to nine distinct chemical classes were identified in 40 pleural effusion samples (20 malignant effusions from lung cancer patients and 20 benign effusions from inflammatory patients). Ketones, alcohols, and benzene derivatives were the main chemical classes for the metabolomic profile of malignant effusions. The average peak areas of ketones and alcohols were much higher in malignant group compared to benign group. Together with phenols, they exhibit significant differences (P<0.05) between the two groups. Particularly, the average peak areas of cyclohexanone and 2-ethyl-1-hexanol in malignant effusions were significantly higher than those in benign ones. Furthermore, of the 36 identified metabolites, 5 compounds including cyclohexanone and 2-ethyl-1-hexanol were found to be statistically different (Student's t-test, P<0.05) between the two groups by statistical analysis based on the peak areas of all identified metabolites. Among them, cyclohexanone and 2-ethyl-1-hexanol might be considered as candidate biomarkers of lung cancer to differentiate malignant from benign effusions. The results show that HS-SPME-GC/MS is a simple, rapid, sensitive and solvent-free method for the determination of VOMs in pleural effusion samples. Pleural effusion is a valuable sample source for observation of changes in VOMs for differentiation between lung cancer patients and inflammatory individuals.

Purification and gas chromatography-combustion-isotope ratio mass spectrometry of aroma compounds from green tea products and comparison to bulk analysis.

A method for carbon isotope ratio (δ(13)C) analysis was developed for compound-specific isotope analysis of tea volatiles, and the values were compared with the δ(13)C value from bulk isotope analyses. The δ(13)C value of 2-phenylethanol liberated via enzymatic hydrolysis of the 2-phenylethyl ß-primeveroside standard was examined first. Isotope fractionations for 2-phenylethyl ß-primeveroside from preparative high-performance liquid chromatography (HPLC) were also analyzed. The enzymatic treatment and the preparative HPLC process did not cause carbon isotope fractionations, substantiating the strategies available for δ(13)C analysis of volatile compounds. On the basis of the gas chromatography-combustion-isotope ratio mass spectrometry data from 2-phenylethanol, it was possible to derive the conditions for enzyme treatment and preparative HPLC of the glycoconjugates of 2-phenylethanol, (Z)-3-hexenol, and benzyl alcohol isolated from green tea leaves. Larger variations in δ(13)C were found for individual volatile compounds compared with bulk analytical data from the leaves, indicating the potential to utilize this strategy in assigning the geographical origin of green tea.

[Indoor air guide values for 2-ethylhexanol]. / Richtwerte für 2-Ethylhexanol in der Innenraumluft.

The German Ad-hoc Working Group on Indoor Guidelines of the Indoor Air Hygiene Committee and of the Supreme State Health Authorities is issuing indoor air guide values to protect public health. 2-Ethylhexan-1-ol (EH) is used amongst others as an intermediate in the production of plasticisers or as a flavouring agent in food, cosmetics and cleaning agents. EH is detectable in nearly all indoor air samples. Indoor air concentrations in Germany were reported to be in the range of 0.002 to 0.006 mg/m3 (median), the 95-percentiles were in the range of 0.009 to 0.03 mg/m3. Toxicity after acute exposure to EH is low. EH is irritating to skin and eyes after direct contact. Acute exposure of humans to 54 mg EH/m3 caused sensory irritation (NOAEC 8 mg EH/m3). In a subchronic inhalation study in rats, neither local nor systemic effects were detectable up to the highest concentration tested (638 mg/m3). EH is not genotoxic and not carcinogenic in rats and male mice after oral application. There is no evidence that EH impairs fertility. Developmental toxicity was only observed at doses, which already caused maternal toxicity (650 mg/kg bw/d). Sensory irritation is the most relevant effect for the derivation of indoor air guide values. Based on a LOAEC of 54 mg/m3 and a NOAEC of 8 mg/m3 in a short time (4 h) inhalation study with volunteers, and applying an intraspecies extrapolation factor of 10 and a factor of 6 for time extrapolation, a preliminary hazard-based guide value of 1 mg EH/m3 and a preliminary precautionary value of 0.1 mg EH/m3 have been derived.

Determination of the thermal and physical properties of black tattoo ink using compound analysis.

Despite the widespread use of laser therapy in the removal of tattoos, comparatively little is known about its mechanism of action. There is a need for an improved understanding of the composition and thermal properties of the tattoo ink in order that simulations of laser therapy may be better informed and treatment parameters optimised. Scanning electron microscopy and time-of-flight secondary ion mass spectrometry identified that the relative proportions of the constituent compounds of the ink likely to exist in vivo are the following: carbon black pigment (89 %), carvacrol (5 %), eugenol (2 %), hexenol (3 %) and propylene glycol (1 %). Chemical compound property tables identify that changes in phase of these compounds lead to a considerable reduction in the density and thermal conductivity of the ink and an increase in its specific heat as temperature increases. These temperature-dependent values of density, thermal conductivity and specific heat are substantially different to the constant values, derived from water or graphite at a fixed temperature, which have been applied in the simulations of laser therapy as previously described in the literature. Accordingly, the thermal properties of black tattoo ink described in this study provide valuable information that may be used to improve simulations of tattoo laser therapy.

Chemical composition and antimicrobial activity of the essential oil of Linum pubescens growing wild in Jordan.

The volatile constituents of the aerial flowering parts of Linum pubescens were collected by hydro-distillation and analysed by GC and GC/MS. Analysis allowed the identification of 68 components of which, geranyl isovalerate (18.93%), lauric acid (12.07%), germacrene D (10.61%), decanoic acid (8.07%), 6,10,14-trimethyl-2-pentadecanone (5.02%) and 1-hexanol (4.99%) were detected as major constituents. The isolated essential oil of the plant exhibited high antimicrobial activity against Gram-positive bacteria (Bacillus cereus ATCC11778, Enterococcus faecalis ATCC 29212 and Staphylococcus aureus ATCC 2923) and showed moderate antimicrobial activity against Gram-negative bacteria (Escherichia coli ATCC 25922, Enterococcus faecalis ATCC 13048 and Klebsiella pneumoniae ATCC 10031).

Identification and quantitation of 3-S-cysteinylglycinehexan-1-ol (Cysgly-3-MH) in Sauvignon blanc grape juice by HPLC-MS/MS.

Precursors to varietal wine thiols are a key area of grape and wine research. Several such precursors, in the form of odorless conjugates, have been closely studied in recent years. A new conjugate has now been identified as 3-S-cysteinylglycinehexan-1-ol (Cysgly-3-MH), being the dipeptide intermediate between cysteine and glutathione precursors of tropical thiol 3-mercaptohexan-1-ol (3-MH). Authentic Cysgly-3-MH was produced via enzymatic transformation of the glutathione conjugate and used to verify the presence of both diastereomers of Cysgly-3-MH in Sauvignon blanc juice extracts. Cysgly-3-MH was added into our HPLC-MS/MS precursor method, and the validated method was used to quantify this new analyte in a selection of Sauvignon blanc juice extracts. Cysgly-3-MH was found in the highest concentrations (10-28.5 µg/L combined diastereomer total) in extracts from berries that had been machine-harvested and transported for 800 km in 12 h. This dipeptide conjugate was much less abundant than the glutathione and cysteine conjugates in the samples studied. On the basis of the results, the new cysteinylglycine conjugate of 3-MH seemingly has a short existence as an intermediate precursor, which may explain why it has not been identified as a natural juice component until now.

[Analysis of essential oil extracted from Lactuca sativa seeds growing in Xinjiang by GC-MS].

OBJECTIVE: To analyze the components of essential oil from Lactuca sativa seeds growing in Xinjiang. METHODS: The components of essential oil from Lactuca sativa seeds were analyzed by gas chromatography-mass spectrometry (GC-MS). RESULTS: 62 components were identified from 71 separated peaks,amounting to total mass fraction 95.07%. The dominant compounds were n-Hexanol (36.31%), n-Hexanal (13.71%), trans-2-Octen-l-ol (8.09%) and 2-n-Pentylfuran (4.41%). CONCLUSION: The research provides a theoretical basis for the exploitation and use of Lactuca sativa seeds resource.

[Analysis of essential oil from Mahonia duclouxiana].

OBJECTIVE: To analyze the compositions of essential oil from Mahonia duclouxiana. METHODS: The essential oil was extracted by steam distillation, its chemical components were analyzed by GC-MS, and principal component was confirmed by GC. RESULTS: 80 peaks were detected and 41 components have been identified, which made up more than 90% of total essential oil. The major component was 4-Terpineol (43.73%), the other high content components were alpha-Terpineol (5.23%), (Z)-3-Hexen-1-ol (4.78%), Linalool (4.04%), etc. CONCLUSION: The chemical components of essential oil of from Mahonia duclouxiana by GC-MS for the first time. This study provided science basis for further research development of Mahonia duclouxiana.

Immunotoxicity activity of the major essential oil of Filipendula glaberrima against Aedes aegypti L.

The aerial parts of Filipendula glaberrima were extracted and the composition and immunotoxicity effects of major essential oils were studied. The analyses conducted by gas chromatography and mass spectroscopy (GC-MS) revealed the essential oils of F. glaberrima. The F. glaberrima essential oil (FGEO) yield was 0.046%, and GC/MS analysis revealed that its major constituents were ß-farnesol (2.96%), l-α-terpineol (2.43%), benzenemethanol (2.87%), (Z)-3-hexen-1-ol (5.23%), and 2,6-bis(1,1-dimethylethyl)-4-methylphenol (1.91%). The essential oil had a significant toxic effect against early fourth stage larvae of Aedes aegypti L with an LC(50) value of 28.43 ppm and an LC(90) value of 76.21 ppm. The results could be useful in search for newer, safer, and more effective natural immunotoxicity agents against A. aegypti.

Quantification of cysteine S-conjugate of 3-sulfanylhexan-1-ol in must and wine of petite arvine vine by stable isotope dilution analysis.

Making use of a convenient synthetic approach to prepare the deuterated S-3-(hexan-1-ol)-cysteine by a Michael addition reaction, an analytical method was developed to measure the presence of the cysteine S-conjugate, precursor of 3-sulfanylhexan-1-ol (3-mercaptohexan-1-ol), in must and wine from Petite Arvine vine. The method uses a stable isotope dilution assay with a suitable one-step sample preparation and HPLC-MS detection. The method has limits of detection and quantification of 3 and 10 microg/L, respectively. A correlation between the increase of the precursor concentration and the increase of the degree of rot has been established.

Comparison of odor-active volatile compounds of fresh and smoked salmon.

The odorant volatile compounds of raw salmon and smoked salmon have been investigated by two gas chromatography-olfactometry methods (frequency detection and odorant intensity) and gas chromatography-mass spectrometry. After simultaneous steam distillation-solvent extraction with diethyl ether and the recovery of the aromatic extract in ethanol, qualitative olfactometric characterization and identification followed by a quantitative assessment of the odorant volatile compounds were carried out. The origin of many odorant compounds of smoked salmon can be attributed to wood smoke. Another part of smoked salmon aroma is due either to the odorant compounds of the raw fish flesh or to an evolution of fish flesh aroma thanks to the smoking process conditions. Forty-nine odorant compounds have been identified in fresh salmon and 74 in smoked salmon. Carbonyl compounds, such as heptanal or (E,Z)-2,6-nonadienal, show a high detection frequency and odorant intensity in unsmoked fish, giving the flesh its typical fishy odor. For smoked salmon, phenolic compounds, such as cresol or guaiacol, and furanic compounds seem to be responsible for the smoked odor.

[Study on the chemical constituents of the volatile oil from aerial parts of Isodon eriocalyx var. laxiflora].

OBJECTIVE: To study the chemical constituents of the volatile oil from the aerial parts of Isodon eriocalyx var. laxiflora. METHOD: The oil was obtained by hydrodistillation. The chemical compositions were separated and identified by GC-MS. The relative contents in the oil were determined by area normalization. RESULT: 163 peaks were separated and 105 compounds were identified, constituting 85.68% of the total peak area. CONCLUSION: 105 compounds characterized by GC-MS analysis were found from I. eriocalyx var. laxiflora for the first time.

[Analysis of volatile fragrant components in hawthorn tincture by gas chromatography-mass spectrometry].

The volatile fragrant components in hawthorn tincture were analyzed by GC/MS. 38 components were identified. The relative content of these constituents were determined with area mormalizing method and the identification ratio was 97.19%. The main components were 3-Hexen-1-ol(370.59 micrograms/g), Eugenol(320.95 micrograms/g), Butanedioic acid hydroxy, diethyl ester(191.25 micrograms/g), 2-Methyl-pentenoic acid(164.83 micrograms/g) and citric acid(80.87 micrograms/g) etc. The method is simple, rapid and highly sensitive and suitable for routine analysis and quality control.

Characterization of estrogenic compounds in medical polyvinyl chloride tubing by gas chromatography-mass spectrometry and estrogen receptor binding assay.

BACKGROUND: In 2001, the U.S. Food and Drug Administration (FDA) convened to conduct a safety assessment of a plasticizer, di(2-ethylhexyl) phthalate (DEHP), released from polyvinyl chloride (PVC) medical devices. Hospitalized patients may be exposed to high concentrations of plasticizers, antioxidants, and chemical contaminants in PVC medical devices during blood transfusion or hemodialysis, thus, making them vulnerable to more potentially adverse effects of these chemicals than healthy people. At the same time, recently, the effect of endocrine-disrupting chemicals on hospitalized patients has attracted a great deal of attention. This study aims to investigate the harmful effects of estrogenic compounds in medical PVC tubing by two approaches of gas chromatography-mass spectrometry (GC-MS) and estrogen receptor (ER) binding assay. METHODS: Residual plasticizers, antioxidants, and chemical contaminants in PVC tubing were subjected to GC-MS in the full-scan mode with an original library for plastic additives. Such residual compounds in PVC tubing were screened at very low concentrations (10(-2)-10(5) nmol/l) to determine whether they competed with fluorescein-labeled estradiol for ER (alpha). RESULTS: DEHP, 2-ethylhexanol, butylated hydroxytoluene, and 4-nonylphenol (NP) were detected in medical PVC tubing. In addition, only NP in PVC tubing was found to bind with ER. CONCLUSIONS: The current study proves that the main residual chemical for estrogenic effect was NP in medical PVC tubing.