On-line trace enrichment for the simultaneous determination of microcystins in aqueous samples using high-performance liquid chromatography with diode-array detection.

The need for a rapid, sensitive and reliable analytical method for cyanobacterial toxins, microcystins, has been emphasized by the awareness of toxic cyanobacteria as a human-health risk through drinking water. A new high-performance liquid chromatographic method with column switching was developed for the determination of microcystin-LR, -RR and -YR from water samples without pre-purification. The filtered water sample was passed through a Zorbax CN precolumn at a flow-rate of 3 ml/min for on-line trace enrichment. After valve switching, concentrated analytes were eluted in back-flush mode and separated on a Luna C18 column with a gradient of acetonitrile -20 mM phosphate buffer (pH 2.5). The method showed excellent precision, accuracy and speed with detection limits of 0.02 microgram/ml from 100 ml of surface water. The total analysis time per sample was about 90 min. This method improves reliability, sensitivity and sample throughput, and shortens the analysis time compared to analysis methods using off-line solid-phase extraction.

[Hepatectomy in intrahepatic lithiasis]. / Hépatectomie dans la lithiase intrahépatique.

STUDY AIM: The aim of this study was to report the immediate results of a series of 65 hepatic resections for hepatolithiasis performed in Vietnam. PATIENTS AND METHOD: From 1986 to 1998, 44 men and 21 women (mean age: 40 years) underwent hepatic resection for hepatolithiasis. Fourty patients had previously undergone one or several operations for hepatolithiasis. The procedure was performed on emergency in 25 patients. Indications for hepatic resection were: angiocholitis and liver abscess in 22 cases, stones closely inserted in the biliary duct in 20 cases, hemobilia in 12 cases, stones located above a biliary stricture in 8 cases and stones associated with a postoperative biliary fistula in 3 cases. Liver resections (minor in 61 patients, including 55 left lobectomies, and major in 4 patients) were performed through transhepatic approach according to the Ton That Tung technique and followed by an external biliary drainage with a Kehr tube. RESULTS: There were 6 postoperative deaths (9%), 3 due to septic shock, 2 to cachexia, and 1 to liver failure. The 15 patients with complications recovered with conservative therapy. Bile infection was present in 93%, mostly with Escherichia coli and Enterobacter. Pigmented stones were usually found. CONCLUSION: Vietnam is a country with high incidence of hepatolithlasis. Hepatic resection is an adequate treatment for localized intrahepatic bile duct stones when the involved segment including biliary strictures and calculi can be completely removed. The procedure may be performed on emergency for liver abscess, or hemobilia.

On-line sample preparation of paraquat in human serum samples using high-performance liquid chromatography with column switching.

A new ion-pair high-performance liquid chromatographic method with column-switching has been developed for the determination of paraquat in human serum samples. The diluted serum sample was injected onto a precolumn packed with LiChroprep RP-8 (25-40 microm) and polar serum components were washed out by 3% acetonitrile in 0.05 M phosphate buffer (pH 2.0) containing 5 mM sodium octanesulfonate. After valve switching to inject position, concentrated compounds were eluted in the back-flush mode and separated on an Inertsil ODS-2 column with 17% acetonitrile in 0.05 M phosphate buffer (pH 2.0) containing 10 mM sodium octanesulfonate. The total analysis time per sample was about 30 min and mean recovery was 98.5+/-2.8% with a linear range of 0.1-100 microg/ml. This method has been successfully applied to serum samples from incidents by paraquat poisoning.