The alkaline hydrolysis rate constants at 35°in 40% aqueous p-dioxane and the nmr chemical shifts have been measured for nine thiolacetates, CH3COSIV, nine methyl thiol esters, RCOSCHj, and seven disubstituted thiol esters, RCOSIV. Alkaline hydrolysis rate constants are controlled almost exclusively by steric effects of the R and R' groups. The nmr substituent chemical shifts (SCS) of thiol esters are controlled largely by steric and sixnumber effects of the R and IV groups. All of these correlations are discussed and compared with correlations previously reported for similar oxygen esters, RCOOR', on the basis of differences in various structural features of the two series. A contributing structure involving negative charge development at the sulfur atom is apparently not of importance for simple thiol esters.
An assay was developed for benzthiazide in plasma, urine and feces, using high performance liquid chromatography (HPLC). A reverse-phase column was employed, with quantitation af 280 nm, using polythiazide as an internal standard. In three of four human subjects who received a 50 mg benzthiazide tablet the plasma concentrations were below the 10 ng ml-1 sensitivity limit of the assay, and the urinary recovery averaged less than one per cent of the dose. One subject received a 50 mg dose as both a tablet and a solution; the urinary recoveries for these two doses were 1.7 and 10.4 per cent, respectively. Fecal samples, obtained from two subjects who received 50 mg tablets, were estimated to contain approximately 80 per cent of the administered dose.
A h i g h performance l i q u i d chromatographic method i s d e s c r i b e d f o r t h e d e t e r m i n a t i o n o f cefoperazone i n plasma, u r i n e and CSF samples. The procedure employs reversed-phase chromatography, u s i n g h y d r o c h l o r o t h i a z i d e as an i n t e r n a l s t a n d a r d . The a s s a y o n l y r e q u i r e s 100 pL o f sample, with d i r e c t i n j e c t i o n o f d i l u t e d u r i n e o r CSF, o r p r o t e i n p r e c i p i t a t e d plasma. S t ab i l i t y s t u d i e s i n d i c a t e t h e need f o r c a r e f u l a t t e n t i o n t o proc e s s i n g and s t o r a g e c o n d i t i o n s of t h e b i o l o g i c m a t e r i a l . The
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