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.

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.

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.