Evaluating the Efficiency of Magnetic Treatment for Feed Water in Reverse Osmosis Processes

The paper presents a new methodology for short-term (5-25 min) benchtop tests to evaluate the effectiveness of magnetic treatment of feed water for reducing mineral scaling on a reverse osmosis (RO) membrane. Scale deposition is measured at a controlled level of salt supersaturation in water flowing through an RO unit in once-through mode. A magnetic water conditioner is tested in a transient flow regime when variations of the permeate flux along the flow path are insignificant. Scale formation under these conditions is governed by salt crystallization on the membrane surface. The proposed method was implemented to investigate the influence of magnetic treatment on gypsum deposition on RO membranes in supersaturated aqueous CaSO₄/NaCl solutions. The effects of magnetic water treatment on scale formation under our experimental conditions were found to be statistically insignificant with a confidence level of 95%. However, this outcome should not be considered to negate the potential efficiency of magnetic water treatment in specific applications. The proposed methodology of testing under a controlled level of salt supersaturation will also be useful for evaluating the efficiency of other water treatment technologies.

Pharmacologic, metabolic, and toxicologic profile of spirapril (SCH 33844), a new angiotensin converting inhibitor

Spirapril (SCH 33844; 7-N-[1(S)-ethoxycarbonyl-3-phenylpropyl]-(S)-alanyl-1,4-dithia- 7-azaspiro[4,4]-nonane-8(S)-carboxylic acid) is a new angiotensin-converting enzyme (ACE) inhibitor. SCH 33844 diacid inhibited hydrolysis of hip-his-leu by rabbit lung ACE in a potent (Ki = 0.74 nM), selective, and noncompetitive fashion. SCH 33844 (0.03-1 mg/kg p.o.) produced dose-related inhibition of angiotensin I (AI) pressor responses in conscious rats with a duration of 24 h at the higher dose. SCH 33844 (0.3-30 mg/kg p.o.) reduced blood pressure in a dose-related manner in conscious SHR with a 24-h duration. Antihypertensive activity was enhanced in the presence of hydrochlorothiazide. The drug (1-10 mg/kg p.o.) also lowered blood pressure in conscious hydrochlorothiazide-treated normotensive dogs. In anesthetized dogs, SCH 33844 (1 mg/kg i.v.) reduced blood pressure and total peripheral vascular resistance and slightly increased cardiac output and stroke volume. These results suggest that peripheral vasodilation is the primary mechanism of the antihypertensive action. The metabolic profile of SCH 33844 was evaluated in dogs and rats. The compound was absorbed in a dose-proportional manner and excreted primarily as the diacid form. In contrast to captopril and enalapril, most of the drug (67%) was excreted into the feces following i.v. dosing. Chronic toxicological evaluation in dogs and rats demonstrated that the drug was relatively devoid of toxicity at oral doses as high as 400 and 450 mg/kg/day, respectively. Slight decreases in heart weight (rats) and increases in granularity of the juxtaglomerular apparatus were observed.(ABSTRACT TRUNCATED AT 250 WORDS)

High-performance liquid chromatographic assay for labetalol in human plasma using a PRP-1 column and fluorometric detection

A high-performance liquid chromatographic assay for the determination of labetalol, a novel antihypertensive agent, in human plasma was developed. Reversed-phase separation of labetalol and the internal standard was accomplished on a 150 X 4.1 mm column commercially packed with a spherical (8-12 micron particle size) macroporous co-polymer (PRP-1). Unlike silica-based columns, the unique properties of PRP-1 permit operation at pH extremes. Based on this advantage, a mobile phase which was sufficiently basic (pH 9.5) to optimize the fluorescent yield of analyte and provide the necessary specificity was selected. Detector response (peak area ratio) was linear from 4 to 500 ng/nl. Following a simple extraction procedure, samples were automatically injected and analyzed using micro-processor-controlled equipment. No interferences were observed in the extracts obtained from drug-free plasma which were processed under the conditions described for unchanged drug. The limit of quantitation using 0.5 ml of plasma was validated to 4 ng/ml. The inter-assay precision (coefficient of variation) was less than 4.6% at all concentrations evaluated from 4 to 300 ng/ml. This method is suitable for the routine quantitation of labetalol or its RR isomer (dilevalol) in plasma (0-24 h) following the administration of therapeutically effective doses to man.