Opposing responses of the rat pulmonary artery and vein to phenylephrine and other agents in vitro.

BACKGROUND: Different from current cognition, our study demonstrated that adrenergic receptors agonist phenylephrine significantly relaxed isolated pulmonary artery but constricted pulmonary veins. Through comparing differences in the effects of commonly used vasoactive drugs on pulmonary artery and veins, the study aimed to improve efficiency and accuracy of isolated pulmonary vascular experiments, and to provide experimental basis for clinical drug use. METHODS: The contractile responses of pulmonary arteries and veins from twelve-week-old Male Sprague-Dawley rats to phenylephrine, arginine vasopressin (AVP), U46619, endothelin-1, and potassium chloride (KCl) were recorded, as well as the relaxation in response to phenylephrine, AVP, acetylcholine. To further explore the mechanism, some vessels was also pre-incubated with adrenergic receptors antagonists propranolol, prazosin and nitric oxide synthesis inhibitor N[gamma]-nitro-L-arginine methyl ester (L-NAME) before addition of the experimental drugs. RESULTS: Phenylephrine constricted pulmonary veins directly, but constricted pulmonary artery only after incubation with propranolol or/and L-NAME. The pulmonary artery exhibited significant relaxation to AVP with or without L-NAME incubation. AVP more clearly constricted the veins after incubation with L-NAME. Changes in vascular tension also varied from pulmonary artery to veins for KCl stimulation. Different from phenomena presented in veins, acetylcholine did not relax pulmonary artery preconstricted by KCl, U46619, and endothelin-1. CONCLUSIONS: According to the results, phenylephrine, KCl, AVP, and acetylcholine could be used to distinguish pulmonary arteries and pulmonary veins in vitro. This also suggested that the pulmonary arteries and pulmonary veins have great differences in physiology and drug reactivity.

Nalbuphine on postoperative gastrointestinal tract dysfunction after laparoscopic surgery for gynaecological malignancies: A randomized controlled trial.

The aim of this study was to compare the effects of nalbuphine and sufentanil on the gastrointestinal (GI) tract after laparoscopic surgery for gynaecological malignancies. A total of 100 patients with American Society of Anesthesiologists (ASA) physical status I-II undergoing laparoscopic radical hysterectomy under general anaesthesia were enrolled. The patients were randomized to receive sufentanil (Group S) or nalbuphine (Group N) intraoperatively and postoperatively. The time to first passage of flatus, the time to first defaecation, the time to toleration of diet, the serum gastrin level, and the duration of hospital stay of the groups were compared. The Visual Analogue Scale (VAS) score for postoperative pain, the number of dispensed patient-controlled analgaesics (PCAs), and the prevalence of postoperative nausea, vomiting, and dizziness of the groups were also compared. The time to first passage of flatus (P = .551), time to first defaecation (P = .310), time to toleration of diet (P = .182), serum gastrin level (P = .397), prevalence of postoperative nausea (P = .920) and vomiting (P = .334), number of dispensed PCAs (P = .167), and the duration of hospital stay (P = .482) of the two groups were not significantly different. The VAS scores at 6 hours (P = .008), 12 hours (P = .002), and 24 hours (P = .013) postoperatively were lower in Group N than in Group S. In conclusion, nalbuphine was not associated with improved postoperative GI dysfunction after laparoscopic surgery for gynaecological malignancies, but it was associated with reduced postoperative pain.

The effect of Nd：YAG lasers used in root canal therapy： a Meta-analysis / 口腔疾病防治

Objective @#Meta-analysis was used to assess the effect of Nd: YAG Lasers used in root canal therapy. @*Methods @# A search of literatures about clinical effect of Nd:YAG lasers in root canal therapy in PubMed, Embase, Cochrane Library, CMCC, CNKI, VIP, Wanfang databases was conducted from 1997 to 2015. The quality of included studies was stringently evaluated and data was analyzed by the RevMan 5.3 software.@*Results@#8 studies were included in the Meta-analysis. Meta-analysis results showed that the ratio of the occurrence of endodontic interappointment emergencies (EIAE) of 24 ~ 48 hours and 1 week after the therapy was significantly lower in the Nd: YAG lasers group compared with the control group (24 h: OR = 0.27, 95％CI = 0.15 ~ 0.48; 1week: OR = 0.26, 95％CI = 0.13 ~ 0.54). The six months to one year failure rate of root canal therapy was lower in Nd:YAG lasers group compared with the control group, the differences were statistically significant (OR = 0.24, 95％CI = 0.06 ~ 1.00). @*Conclusion@# The use of Nd: YAG laser in root canal therapy relieves post-treatment pain response after the therapy and also reduces the long-term failure rate of root canal treatment.

Chlorination of bisphenol F and the estrogenic and peroxisome proliferator-activated receptor gamma effects of its disinfection byproducts.

The reaction kinetics and transformation pathways between bisphenol F (BPF) and sodium hypochlorite were investigated at pH values ranging from 6.5 to 8.5 and with different initial concentration ratios. The reaction rate was pH- and free available chlorine (FAC)-dependent: the reaction rate at pH 8.5 was almost 10 times than that at pH 6.5. A total of 40 compounds were tentatively identified as chloro-substituted BPF and polyphenolic compounds by liquid chromatography quadrupole time-of-flight mass spectrometry operating in electrospray ionization mode (LC-ESI-Q-ToF), and 4 main byproducts were confirmed by 1H and 13C nuclear magnetic resonance (NMR). Toxicity tests indicated that the estrogenic effects of chloro-substituted BPF decrease as the chlorine substitution increase. On the contrary, increasing numbers of chlorines on the phenolic rings of BPF enhanced the nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ) activity. Tetra-chlorinated BPF had an approximately 6.9-fold higher activity than BPF.

[In vitro Metabolism of Volatile Methyl Siloxanes].

Volatile methyl siloxanes (VMSs) are of great concern in the past few years due to their high production volume, ubiquitousness in the environment and toxicities. The bioaccumulation of VMSs is reported to be sensitive to their metabolism rates, however, little is known about their metabolic rates in aquatic organisms. The present study measured intrinsic clearance rates of 16 common VMSs (D3-D6 and L3-L14) incubated in liver microsomes of weever and quail. The intrinsic clearance rates of VMSs in weever microsomes were 0-0.031 mL·(h·mg)-1. The fact that D5 exhibited no significant decline trend in the incubations with liver microsomes of weever corresponded with its trophic magnification behaviour in aquatic food webs. L4-L14, similar to D5, were also persistent in microsomes, suggesting the high bioaccumulation potentials of the chemicals. The intrinsic clearance rates of VMSs incubated in quail microsomes [0.25-1.7 mL·(h·mg)-1] were significantly higher than those incubated in weever microsomes. The relatively high biotransformation rates of D3-D6 and L3-L14 suggested that these compounds may not exhibit high biomagnification potentials in birds. B[a]P was used as a benchmark chemical to normalize variations in determining the metabolism rates among batches, and the structure-activity relationships were explored for the normalized intrinsic clearance rates of quail microsomes. Hydrophobicity and electric properties were found to be major factors influencing the bird microsomal intrinsic clearance rates of VMSs.

Contribution of synthetic and naturally occurring organobromine compounds to bromine mass in marine organisms.

An extraction, separation, and purification method was developed for the identification and quantification of total bromine (TBr), extractable organobromine (EOBr), and five classes of identified EOBrs. Instrumental neutron activation analysis (INAA) was utilized to quantify EOBr and TBr. The method was then applied to liver samples of tuna, albatross, and polar bear collected from remote marine locations. Polybrominated biphenyls (PBBs), polybrominated diphenyl ethers (PBDEs), bromophenols (BRPs), hydroxylated (OH-) and methoxylated (MeO-) PBDEs were analyzed as identified EOBr. The majority of the bromine in these marine organisms was nonextractable or inorganic, with EOBr accounting for 10-28% of the TBr. Of the identified EOBr, in tuna and albatross, naturally occurring compounds, including MeO-PBDEs, OH-PBDEs, and BPRs, were prevalent. However, the identifiable EOBr in polar bears consisted primarily of synthetic compounds, including PBDEs and PBBs. Overall, 0.08-0.11% and 0.008-0.012% of EOBr and TBr, respectively, were identified. The proportion of EOBr that was identified in marine organisms was relatively small compared to the proportions for organofluorine and organochlorine compounds. This could be related to the great diversity of naturally occurring organobromine compounds in the environment. Naturally occurring brominated fatty acids were estimated to be the predominant compounds in the EOBr fraction.

[Prokaryotic expression of human vitamin D receptor (hVDR) and its binding activities to Cd and Pb].

Human vitamin D receptor (hVDR) is a potential receptor channel for heavy metals to affect bone metabolism, while to date there is no report about the binding activity between heavy metals and hVDR. This study established a prokaryotic expression of hVDR system, by cloned hVDR-LBD into pGEX-4T-1 vector. Then according to the principle that the nuclear receptor binding with its ligand can be combined with nuclear receptor coactivator 2-bacterial alkaline phosphatase fusion protein (TIF2-BAP), we established a method of p-nitrophenylphosphate-alkaline phosphatase to analyse the effects of chemical on the binding activity between hVDR and TIF2-BAP. Using this method, we studied the binding activities between hVDR and TIF2-BAP after exposure of cadmium and lead. The results showed that the binding activities significantly increased to 3.95 and 4.39 times that of the control after exposure of 100 micromol/L and 1 000 micromol/L cadmium chloride (CdCl2), and the binding activities significantly increased to 2.29 and 3.52 times that of the control after exposure of 100 micromol/L and 1 000 micromol/L lead acetate (PbAc2), respectively. These results indicate that cadmium and lead can mimic the activity of 1,25-(OH)2D3, disrupt the normal function of hVDR receptor channel, which may be the underlying mechanism of abnormal bone metabolism and osteoporosis caused by cadmium and lead.

[Gene cloning, sequence analysis and tissue expression of estrogen-related receptor alpha (Erralpha) in Japanese medaka and its transcriptional responses after differential EDCs exposure].

Endocrine disrupting chemicals (EDCs) can bind or block nuclear receptors in the body and subsequently affect growth, development and reproduction of fish. Estrogen-related receptors (ERRs), belonging to the nuclear receptor superfamily, have been implicated in diverse physiological processes in estrogen signal pathway in mammals, while little is known about them in fishes. Complete mRNA sequence of ERRalpha from medaka (Oryzias latipes) was cloned, and the sequence is similar to those of other vertebrates, especially that the DNA-binding domain (DBD) of ERRalpha is highly conserved among the vertebrates (97.4%-100% sequence identities) and the ligand-binding domain (LBD) of medaka ERRalpha is 66.4%-67.0% sequence identities with those of mammals. The DBD of medaka ERRalpha is of the same length and has high sequence identity with those of estrogen receptor (ERalpha and ERbeta) and androgen receptor (ARalpha and ARbeta) of medaka, but much difference was found between the LBD of medaka ERRalpha with those of ERalpha, ERbeta, ARalpha and ARbeta. ERRalpha gene is located in chromosome 14 and is consisted of 5 exons. The expressions of ERRalpha in different tissues and the transcriptional responses of ERRalpha in testis of medaka exposed differential EDCs were studied by quantitative real-time RT-PCR. ERRalpha is expressed at apparently high levels in gonad, brain, eye, spleen and intestine, though it was broadly expressed in tissues. Significant transcriptional difference was found between testis and ovary, implying ERRalpha would be involved in sex differentiation and gonad development in fish. After 3 weeks exposure of medaka to 200 ng/L ethynylestradiol (EE2), 200 ng/L estrone (E1), 200 ng/L diethylstilbestrol (DES), 100 microg/L atrazine (AT) and 200 ng/L 17beta-estradiol (E2), transcripts of ERRalpha were significantly decreased to 0.54, 0.56, 0.61, 0.63 and 0.65 of control (p < 0.05) in the testes, respectively. And those in the 1 microg/L tributyltin (TBT) and 1 microg/L triphenyltin (TPT) exposure groups were up-regulated to 1.34 and 1.35 folds of control (p > 0.05), respectively. These results suggested that ERRalpha would take actions in the disruption of sex differentiation and gonad development in fish by EDCs. In addition, no multiple steroid hormone-response element half-sites was found in medaka, which were reported in the upstream of ERRalpha gene in mammals, indicating there would be different regulation patters of ERRalpha between teleost and mammal.

Vertical distribution of nonylphenol and nonylphenol ethoxylates in sedimentary core from the Beipaiming Channel, North China.

The vertical profiles of nonylphenol (NP) and nonylphenol ethoxylates (NPEOs) were investigated in a sediment core from the Beipaiming Channel, North China using high sensitive LC-MS and GC-MS methods. In this core, relatively high concentrations of NP and NPEOs occurred in the surface sediment (< or = 40 cm), with the maximum value of NP and NPEOs reaching 3539 and 12735 ng/g, respectively, whereas, no NP or NPEOs were detected in deeper sediments (> 40 cm). The high concentrations of NP and NPEOs in the surface layers suggested recent inputs in this area. NPEOs with short ethoxy chains (NPnEO, n = 0-3) were dominant in the NPEO mixture with percentages from 54% to 78%, which were similar to the distribution of homolog NPEO in effluents from nearby sewage treatment plants (STPs), indicating that the channel received the effluents from these STPs. The sewage treatment ratio was quite similar to that found in North America before the 1980s. Finally, the concentrations of NP and NPEOs were related to the total organic carbon (TOC) (p < 0.001), suggesting that TOC was an important factor for vertical distribution of NPEOs and NP from the Beipaiming Channel.

[Evaluation of estrogenic activity for nonylphenol using quantitative real-time RT-PCR method].

It has been demonstrated that nonylphenol (NP) exerts estrogenic activity. Quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR) was used to study the VTG-I , VTG-II , CHG-H and CHG-L genes expression in the liver of juvenile medaka exposed to NP at 1, 10, 50, 100 microg/I. for 60 days. The results show that the VTG-I , VTG-II, CHG-H and CHG-L genes expression in the liver of juvenile medaka are induced even at 1 microg/L, significantly. It should be noted that the lowest-observed-effect concentration (LOECs) based on the hepatic vitellogenin (VTG) induction is about 1 microg/L, suggesting that quantitative real-time RT-PCR can detect the estrogenic activity of NP at relatively low concentration, and there is a potential application in evaluating the estrogenic activity of NP in aquatic environment.

A method of assessing ecological risk to night heron, Nycticorax nycticorax, population persistence from dichlorodiphenyltrichloroethane exposure.

This paper first introduces a probabilistic method for quantitatively evaluating the effects of chemical pollutants in the environment on a wildlife population, which was applied to assess the ecological risk to night heron (Nycticorax nycticorax) population persistence from dichlorodiphenyltrichloroethane (DDE) exposure in Tai Lake, China. Intrinsic rate of population increase (r) calculated with a population age-structured matrix model was used to measure the adverse effect on population. To perform a probabilistic analysis of risk, lost intrinsic rate of population increase (deltaZ) because of DDE exposure was applied to express the exact extent of risk. The result showed that the risk (i.e., the expectancy of deltaZ of the night heron population exposed to DDE in Tai Lake) was 0.0259, indicating a decrease in gross population size of 2.56% every year compared with that of the previous year without DDE exposure.

[Improvement of concentration method for detecting genotoxic activities of drinking water using umuC-test].

umuC-test is an effective method to determine the genotoxic activity. In this study, the highest genotoxic activity was found exactly at 37 degrees C by modifying original condition of umuC test. Effects of concentration methods on the genotoxic activity was studied, and it was found that the HLB solid phase extraction is most effective to extract the genotoxic chemicals from a drinking water when using acetone as eluant. The fate of genotoxic activity in drinking water treatment process was also studied, and chlorination promoted the induction of genotoxic activity.

[Loss of life expectancy analysis for cancer risk in Tianjin area].

Loss of Life Expectancy was proposed as the single metric for health risk assessment. Based on the statistical data of population in Tianjin, it was calculated that the unit cancer risk (10(-5)) equivalents to 58.47 and 66.82 minutes of life expectancy loss for male and female, respectively. The results depend strongly on the background rate of cancer, with little response for associated parameters.

[Modification and application of recombinant yeast bioassay for measuring the AhR ligand activity].

A recombinant yeast bioassay, a yeast Saccharomyces cerevisiae, in which the human AhR and ARNT complex are coexpressed, is one of the methods to screen the active AhR agonist. In this study, the original agonist test was modified. The exposure time was reduced from 18 to 8 hours when experiment was under the following conditions: (1) the yeast was cultured in 0.2% glucose medium for 24 hours; (2) chemical exposure was carried in 2% galactose medium in glass tube. Finally, the AhR acitivity of hexachlorobenzene and pentachlorobenzene were assessed, and their toxicity equivalent factors were found to be 0.018629 and 0.000294, respectively.

Identification of ubiquinones and menaquinones in activated sludge by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry.

A sensitive analytical method has been developed for identification of ubiquinones (UQ-n(Hx)) and menaquinones (MK-n(Hx)) in activated sludge by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry in negative mode (LC-NI-APCI-MS). Extraction and clean-up of samples were carried out on Sep-Pak Plus Silica solid-phase extraction cartridges. Complete separation of quinones was achieved with an ODS analytical column and using isopropyl ether-methanol (17:83, v/v) as the mobile phase. The compositions of ubiquinones and menaquinones were determined directly using combined information on retention time, the molecular ion mass and fragment ion masses. The lowest instrument quantitative detection limits (LODinst) for UQ-6, UQ-10, and Vitamin K1 were estimated to be 0.4, 4 and 0.12 ng (S/N = 10) using LC-NI-APCI-MS in SIM mode, and the lowest method detection limits (LODmeth) achieved by spiking experiment were estimated to be 0.2, 2 and 0.06 microg/g for UQ-6, UQ-10 and Vitamin K1, respectively. On the other hand, the LODinst for UQ-6, UQ-10, and Vitamin K1 were estimated to be 10, 100 and 2 ng (S/N = 10) using LC-NI-APCI-MS in full-scan mode, and the LODmeth were estimated to be 7, 60 and 1.2 microg/g for UQ-6, UQ-10, and Vitamin K1, respectively. Both LC-NI-APCI-MS and LC-UV/DAD were applied in the analysis of an activated sludge extract. UQ-n (n = 6-10), MK-n (n = 6-10), MK-n(H2) (n = 7-10), MK-n(H4) (n = 8-9) and MK-8(H6) were detected by LC-NI-APCI-MS, while UQ-6, UQ-7, MK-7(H), MK-9 and MK-10(H2) were not found by LC-UV/DAD. These results suggest that LC-NI-APCI-MS is more sensitive than LC-UV/DAD for the analysis of quinones in environmental samples such as sediment, activated sludge and bio-film in biological processes and other aquatic environments.

Quantitative structure-activity relationships for estrogen receptor binding affinity of phenolic chemicals.

The estrogen receptor (ER) binding affinities of 25 compounds including 15 industrial phenolic chemicals, two phytoestrogens, three natural steroids and one man-made steroid were detected by a binding competition assay. The 17 industrial phenolic chemicals were selected as objective compounds because they are possibly released from epoxy and polyester-styrene resins used in lacquer coatings of concrete tank and lining of steel pipe in water supply system. A quantitative structure-activity relationship (QSAR) for structurally diverse phenols, nine alkylphenols with only one alkyl group, four hydroxyl biphenyls, bisphenol A and four natural and man-made estrogens was established by applying a quantum chemical modeling method. Logarithm of octanol-water coefficient (logPow), molecular volume (V(m)), and energies of the highest occupied molecular orbital ( epsilon (HOMO)) and lowest unoccupied molecular orbital ( epsilon (LUMO)) were selected as hydrophobic, steric (V(m)), and electronic chemical descriptors, respectively. Chemicals capable of ER binding had large V(m) and high epsilon (HOMO), while the effects of logPow and epsilon (LUMO) on the binding affinity could not be identified. The QSAR made successful predictions for the three phytoestrogens. Also, the successful prediction of ER-binding affinity for biochanin A, another phytoestrogen, two indicators of pH (phenolphthalin and phenolphthalein) and one alkylphenolic chemical with three alkyl groups (4-methyl-2,6-di-butyl-phenol), by amending the V(m) in the above-mentioned QSAR according to the electron-density distribution (or HOMO density) is an additional step in the elucidation of chemical steric and electronic parameters for predicting the binding affinities of phenolic compounds.

Products of aqueous chlorination of 4-nonylphenol and their estrogenic activity.

Seven reaction products (2-chloro-4-nonylphenol [NP], 2,6-dichloro-4-NP, trichlorophenol, 4-propyl-2'-hydroxyphenol, 4-isobutyl-2'-hydroxyphenol, 4-isoamyl-2'-hydroxyphenol, and 4-isopentyl-2'-hydroxyphenol) were identified by gas chromatography/mass spectrometry (GC/MS) in order to assess the estrogenic activity originated from 4-nonylphenol (4-NP) in drinking water. The estrogenic activities of the aqueous chlorinated 4-NP solution at 10, 60, and 120 min chlorination time were assessed by a yeast two-hybrid system based on the ligand-dependent interaction of two proteins, a human estrogen receptor (ER), and a coactivator. It was found that all three solutions inhibited transcriptional activation induction by 4-NP. Further experiments showed that these solutions also inhibited beta-galactosidase induction by 17beta-estradiol. For the solution at 10 min, the inhibition was found to be due to its toxicity, with an inhibition concentration (IC50) of about 10-fold of concentration of chlorinated 4-NP solution, suggesting the existence of some products with higher yeast toxicity than that of the parent 4-NP. Similar inhibition trends were also found in the dose response of the two solutions at 60 and 120 min, with an IC50 of 10-fold concentration. In these cases, the effects were considered to result from their antagonist action because the two solutions show lower yeast toxicity of which IC50 is 45-fold concentration. This suggests that some products in the chlorinated 4-NP solution elicit the antiestrogenic activities.

Products of aqueous chlorination of bisphenol A and their estrogenic activity.

To assess the estrogenic activity potentially stemming from bisphenol A (BPA) in drinking water, APCI/LC/MS and NMR were used to identify the products of its aqueous chlorination under the following conditions: 500 microg/L bisphenol A and 1.46 mg/L sodium hypochlorite (pH 7.5) at 25 degrees C. The 13 products (4-chloro-BPA; 2,6'-dichloro-BPA; 2,6-dichloro-BPA; 2,2',6'-trichloro-BPA; 2,2',6,6'-tetrachloro-BPA; trichlorophenol; 4-isopropyl-2'-hydroxylphenol; and six kinds of polychlorinated phenoxyphenols (PCPPs)) were found in the chlorinated BPA solution. Three main pathways are proposed: (1) chlorine-substitution reactions on the aromatic ring, followed by dehydration to form the chlorine-substituted BPA, (2) chlorine substitution reactions followed by cleavage of the alpha-C on the isopropyl moiety with positive partial charge and beta'-C on the benzene moiety with a negative partial charge to form trichlorophenol and 4-isopropyl-2'-hydroxylphenol, and (3) the formation of PCPPs. Especially for pathway 2, the reaction mechanism was clarified based on semiempirical quantum mechanical calculations. The reaction proceeded by attack of the OH and Cl (from HOCl) on the alpha-C on the isopropyl moiety with a positive partial charge and on the beta'-C with a negative partial charge on the benzene moiety. The activation energies forthe HOCl/4-chloro-BPA and 2,2',6,6'-tetrachloro-BPA reactions were 0.14 and 0.15 kcal/mol, respectively. Finally, the estrogenic activity of the aqueous chlorinated BPA solution was assessed by an estrogen receptor binding assay and a yeast two-hybrid system. It was found that the binding affinity of the chlorinated aqueous BPA at 60 min was 24 times that before chlorination. The transcriptional activation-induced by products were detected by a yeast two-hybrid system based on the ligand-dependent interaction of two proteins, a human ER and a coactivator, suggesting that the chlorinated BPA solution elicits an ability to mimic the effect of the estrogen hormone.

Determination of nonylphenol ethoxylates in the aquatic environment by normal phase liquid chromatography-electrospray mass spectrometry.

A comprehensive analytical method based on normal-phase liquid chromatography-electrospray ionization mass spectrometry (NPLC-ESI-MS) has been established for determination of nonylphenol ethoxylates (NPEOs) in the aquatic environment. Extraction and cleanup of samples were performed on graphitized carbon black (GCB) solid-phase extraction cartridges. Complete separation between each individual NPEOs was achieved by combining a C18 pre-column with a silica analytical column and using acetonitrile-water as eluent. Quantitative determination by LC-ESI-MS was achieved in the positive ionization (PI) mode at a ramped cone voltage for NPEOs using selected ion monitoring. Recoveries for NPEOs ranged between 91.9 and 117.5%, and the limits of detection varied between 0.5 and 2 ng/l for individual NPEOs with n longer than 2, and between 5 and 0.5 microg/l for NPIEO and NP2EO. This method was successfully applied to the investigation of residual NPEOs with n>2 in the Chongqing area of the Changjiang river. NPEOs with n ranging from 1 to 22 were found to vary between 0.1 and 2900 ng/l with a distribution depending on the depth of water.