Trace determination of fifteen free amino acids in drinking source water via solid-phase extraction coupled with liquid chromatography tandem mass spectrometry.

Amino acids (AAs) are important nitrogen-containing organics in water, and a large number of reports have proven that they were the precursors of many nitrogen-containing disinfection by-products, some of which have cytotoxicity and carcinogenicity. However, little has been done on their occurrence in drinking source water. Therefore, a trace determination method via solid-phase extraction coupled with ultra-high pressure liquid chromatography tandem mass spectrometry (UPLC-MS/MS) for 15 free AAs (FAAs) was developed, which was successfully applied for drinking source water samples. For sample preparation, strong cation-exchange stationary solid-phase extraction (SPE) cartridge showed better extraction performance to that of reverse phase stationary oasis HLB SPE cartridge. The optimal water pH was determined to be 2.8 before extraction. Strong matrix effects for most FAAs were observed in this work; thus, sample extraction with SPE was recommended to eliminate the matrix effects. The developed method showed excellent linearity (R2 > 0.991), low limits of detection (LODs, 0.01-0.27 nmol/L), and good recoveries of 69.8-117.9% in drinking source water with low relative standard deviations (RSDs, 0.3-13.2%). The developed method was finally applied to eight drinking source water samples, and the top five FAAs were found to be serine, glycine, leucine, alanine, and isoleucine.

[Study of symbolic element in roasting slag of pyrite by inductively coupled plasma mass spectrometry].

In the present paper, the correlations between sixteen elements from the dry method roasted dust-slag of pyrite and sixteen elements from the soil layer near and far from the store area were studied by ICP-MS. Similar radio and outstanding different radio of the elements between the dust-slag and the soil were studied too. It was discovered that in the pollution soil layer Tl, Cd, Cs, Cu, Zn, Mn, Pb and Ni were easy to be identified and had similar radio with the elements in the dust-slag. But only Tl, Cd, Zn and Ni are suitable for criterion of element similar properties. In dust-slag and soil, distinct composition element radios of Tl, Cs, Co, Mo, Zn, Cr, V, Sr, Sb, Pb, Rb, Mn and Ni had striking differentiation. Only Tl, V, Sb and Cu corresponded to both the uncorrelated elements analysis of surface layer and middle-base layer soil. Tl could be used as an inspection target of similar elements and outstanding different elements between the dust-slag and the soil in the meanwhile. So we suggested that Tl can be used as a symbolic element in the roasting dust-slag of pyrite to find the dust-slag of pyrite in dust-recognition and to differentiate the metallurgy dust of pyrite and soil dust.

Study on oxidation of pyrite by in situ absorption spectroscopy.

Pyrite is one of the common natural mineral. It is easily oxidized and brings heavy metal contaminations, therefore it is the main source of acidity mine drainage. The study on the dynamics of pyrite is helpful to comprehending the mechanism of its pollution. In the present paper, an experimental method was designed that phenanthroline reacts with Fe2+ that is released from pyrite in solution, and produces stable orange-red complex compound. It can be detected by absorption spectroscopy. In-situ characterization of oxidation of pyrite can be achieved by this method. The results showed that the method is reliable and accurate, and it has high sensitivity and little interference; the reaction rate of oxidation increased linearly with time, corresponding to the characterization of zero-order reaction; oxidation of pyrite belongs to the surface reaction and the process of surface reaction is rate determining step.

[Determination of trace mercury in hair by hydride generation atomic fluorescence spectrometry].

A method for determination of trace mercury in hair by hydride generation atomic fluorescence spectrometry under normal or high temperature and high humidity condition was described. The ways of samples pretreatment, analysis and rapid clearing up bad memory were researched. The results showed: that the effect of instability of mercury can be cushioned under high temperature and high humidity condition by choosing much negative high pressure and control long the fluorescence intensity of standard blank. There weren't evident differences in the measure results of standard graph, standard and sample between normal and high temperature and high humidity conditions. When the reducer concentration was more than 2.5 percent or less than 1.5 percent the fluorescence signal was often overrun or disappeared. The sensitivity and stability of instrument weren't easily balanced. Due to sulfuric acid remainder, the fluorescence intensity of sample blank was higher than that of standard blank, especially under high temperature and high humidity, so in the proceed of sample pretreatment sulfuric acid was used scarcely. The bad memory effect can be cleared up rapidly by correction of negative high pressure and correction of of timized standard graph. The method was rapid and accurate. The relative standard deviation (RSD) was equal to or small than 1.1%. The detection limit of the method was 0.006 ng x mL(-1).

[Application of ICP-MS in evaluating element contamination in soils].

The Yunfu pyrite was the second biggest pyrite bed in the world. Plants using industrial ore of the Yunfu pyrite are distributed in many sections across the country. In the present paper, elements V, Cr, Co, Cu, Zn, Mo, Cd, Sb, Rb and Cs in soil profiles in slag disposing area of a sulfuric acid plant using industrial ore of theYunfu pyrite were studied. A method for simultaneously determination of metals and some reference elements in soils by ICP-MS was developed. The correlations between the metals and their reference elements were fast found. Enrichment factors were applied for evaluating the degree of soil contamination, and the problem about choosing contamination elements background values was pointed out. The results indicated that element V showed apparent and serious pollution, The Co showed middle degree pollution, and there has been a trend of apparent pollution. The Cr, Mo and Cd showed pollution between light degree and middle degree. The Zn and Sb showed light degree pollution, and there was a latent trend of middle degree pollution. The Cu showed light degree pollution. The high enrichment points of the V and the Cr were observed in the upper part (4.0-10.5 cm) and deep part of soil profiles (44.0-75.5 cm). Those of Co and Mo were found in the surface of soil profiles (0-5.0 cm), middle-upper part (9.5-10.5 cm) and middle part (29.5-46.0 cm), while those of Cd and Cu occurred just in the middle of soil profiles (29.5-46.0 cm). The formation of highly enrichment points of contamination elements in the soil profiles was the result of leaching and accumulating effect of the metals released from slag and the residual metals of highly weathered red soils. Most of pollution of V in the soil was contributed by the V in soil bed. Part of the V pollution in the soil was supplied by leaching and accumulating effect of the V which came from catalyst with lost activity in sulfuric acid production volatilizing into slag.

Characteristics of basal cell carcinoma amongst Asians in Singapore and a comparison between completely and incompletely excised tumors.

BACKGROUND: Most published series of basal cell carcinomas (BCCs) are based on Caucasian populations. Very little is known about the characteristics of incompletely excised BCCs in Asians. OBJECTIVES: This study examines the characteristics of BCCs in Asian residents in Singapore, and compares incompletely with completely excised tumors after conventional surgical excision. PATIENTS AND METHODS: A retrospective study was conducted using the case records of patients who had a primary BCC excised at the National Skin Centre between 1991 and 1995. RESULTS: A total of 185 histologically confirmed BCCs were recorded in 166 patients (male to female ratio, 0.95; mean age, 70.9 years). The highest proportion (27.1%) was in the 81-90-year age group. Compared with census data, a significantly higher proportion of patients with BCCs were Chinese (P < 0.001). The tumors averaged 12.0 mm in diameter and the majority (84.3%) were located on the head and neck. In 28 lesions (15.1%), the tumors were incompletely excised, with those on the nose and nasolabial folds being most frequent. Incompletely excised BCCs were more likely than completely excised lesions to be located on the mid-face and trunk (P = 0.003), but there was no significant correlation with tumor size, tumor duration, or patient age, race, and gender. The overall recurrence rate was 1.6% over a mean follow-up time of 74 months. CONCLUSIONS: BCCs are more common amongst Chinese in Singapore and occur chiefly in the elderly. Conventional surgical excision with margin control achieves a satisfactory tumor clearance rate of 84.9%. Incomplete excision is associated with tumor location on the mid-face and trunk rather than tumor size or duration.

A randomized, placebo-controlled trial of thymosin-alpha1 and lymphoblastoid interferon for HBeAg-positive chronic hepatitis B.

Combination therapy between two immunomodulators used for treatment of chronic hepatitis B was explored based on reported therapeutic efficacy of interferon-alpha, and thymosin-alpha1 as monotherapeutic agents to determine if combination therapy was superior to interferon alone. This double-blinded, randomized, placebo-controlled trial compares the addition of thymosin-alpha1, 1.6 microg taken three times per week (combination therapy) or thymosin placebo (monotherapy) to lymphoblastoid interferon (Wellferon), 5 million international units (MIU) taken three times per week, for 24 weeks. Entry criteria included positive hepatitis B e antigen (HBeAg); alanine aminotransferease (ALT) > or = 1.5 x upper normal limit, but < or = 10 x upper normal limit; positive HBV DNA; absence of cirrhosis; treatment naivety and no co-morbid factors. A total of 98 HBeAg-positive patients were recruited, of which 48 were randomized to combination therapy and 50 to monotherapy. The primary endpoint was the loss of HBeAg at 72 weeks. The secondary endpoints were HBeAg seroconversion, normalization of ALT, loss of HBV DNA and improvement in histology. The HBeAg loss was 45.8% and 28.0% for combination therapy and monotherapy, respectively (difference, 17.8%; 95% CI -1.2%-35.3%, P = 0.067). There was a trend towards HBeAg loss when using combination therapy. There were also no statistically significant differences between the different therapies with respect to the secondary endpoints of HBeAg seroconversion, changes in histology, normalization of ALT or loss of HBV DNA. In conclusion, this trial showed a 17.8% improvement in HBeAg loss rates using combination therapy over interferon monotherapy. This could clinically indicate a potential important difference that would need confirmation in subsequent trials.

Acute primary angle closure: configuration of the drainage angle in the first year after laser peripheral iridotomy.

PURPOSE: To evaluate the changes in the configuration of the drainage angle in the first year after acute primary angle closure (APAC). DESIGN: Prospective observational case series. PARTICIPANTS: Forty-four Asian subjects with APAC. METHODS: Acute primary angle closure cases were treated with medical therapy followed by laser peripheral iridotomy (LPI). Static and dynamic gonioscopies were performed in APAC-affected and fellow eyes before LPI (baseline) and then at 2 weeks, 4 months, and 12 months after presentation. The angles were graded in each quadrant according to the Shaffer scheme, and the number of clock hours of peripheral anterior synechiae (PAS) was recorded. Patients who underwent intraocular surgery at any point during follow-up were excluded from the study. Intraocular pressure (IOP) and medical treatment were documented at each visit, and gonioscopic changes were correlated with the development of elevation in IOP requiring medical treatment. MAIN OUTCOME MEASURES: Average Shaffer grade and the number of clock hours of PAS. RESULTS: The majority of subjects were Chinese (84%) and female (64%), and the mean age was 60.2+/-10.7 years. At presentation, 73% of both affected and fellow eyes had very narrow angles (average Shaffer grade < or = 1), with affected eyes having more extensive PAS (P<0.001), a third of whom had > or =8 clock hours of PAS. In APAC eyes, there was a significant increase in angle width from baseline to 2 weeks after LPI (P = 0.045), but no change in angle width subsequently. Fellow eyes showed a widening of the angle between baseline and week 2 (P = 0.01) and from week 2 to month 4 (P = 0.001). There was no significant change in PAS in either affected or fellow eyes over the 12 months of follow-up. Of the 44 subjects, 19 (41.3%) subsequently developed IOP elevation during follow-up that required treatment. However, there was no difference in angle width or amount of PAS between eyes with and without a subsequent rise in IOP, and the angle configuration did not change significantly in either group over 1 year. CONCLUSION: In Asian eyes with APAC, the angle widened in the first 2 weeks after LPI, but did not change thereafter over 1 year, and the amount of PAS remained stable throughout. The results indicate the effectiveness of LPI in preventing progressive closure of the angle in the first year after APAC.