SWAGELOK® Tube Fittings conditions during thermospray vaporization change in < 1 s from 25 °C to > 200 °C. If thermal decomposition is suspected, it is often helpful to clarify the situation by using HPLC to separate electrochemically generated spe cies prior to their encounter with the thermospray interface (EC/HPLC/ MS) (25). The thermospray LC/MS interface normally generates backpressures of —900 psi at a flow rate of 1.5 mL/min. Because an additional 1000-2000 psi of backpressure can be added to the system by placing an HPLC column between the electrochemical cell and the thermospray interface, the cell must be capable of withstanding operating pressures as high as 2000-3000 psi. In F i g u r e 10 we can see how EC/HPLC/MS can be used to separate and identify electrochemical oxidation products of 6-thiopurine (6-TP). Five peaks are detected eluting off the HPLC column. (Several electrochemical products thermally decompose to yield ions of the same mass-to-charge ratio.) These peaks correspond to purine-6-sulfinic acid (RS0 2 H), which thermally decomposes within the thermospray probe to purine ([M + H] + at m/z 121) before detection; hypoxanthine ([M + H] + at m/z 137); purine-6-sulfinamide (RSONH 2 , [M + H] + at m/z 184); pur i n e - 6 - sulfonic acid ( R S 0 3 H , [M + H] + at m/z 201); and 6-thiopurinedisulfide (6-MP disulfide, [M + H ] + a t m/z 3 0 3 ) . R S 0 3 H , RS0 2 H, and 6-MP disulfide form in solution following electron transfer (25). H y p o x a n t h i n e and R S O N H 2 originate in solution from 6-thiopurine sulfenic acid, RSOH, which is a 2e oxidation product of 6-TP and which decomposes rapidly before separation. Purine is a decomposition product of RSONH 2 and R S 0 2 H . Hypoxanthine is also a decomposition p r o d u c t of R S O N H 2 ; h o w e v e r , RSONH 2 , unlike RS0 2 H, can still be detected by MS despite the decomposition. Extensive thermal decomposition of the disulfide is also clear from the results in Figure 10. These products were identified by comparing the mass spectra and chromatographic retention times of electrochemically generated products with those of standards (25). E C / H P L C / M S can be especially valuable in providing information about reaction pathways, because individual products can be monitored as a function of applied potential. In contrast to bulk electrolysis, in which results can sometimes be misleading
...your widest selection of sizes, shapes, and materials leak-tight performance, low in-service cost m fractional sizes 1/16" to 2" • metric sizes 2mm to 25mm (male and female connectors available in tube to NPT or BSP/ISO threads) • all machinable metals and plastics • locally available from Authorized Sales & Service Representatives
Male Connector
Union Tee
SAE/MS Positionable Male Elbow
Bulkhead Male Connector
SAE/MS Male Connector
Union Cross
Male Elbow
SAE/MS Positionable Male Run Tee SWAGELOK to AN Union
45° Male Elbow
SWAGELOK to AN Bulkhead Union
45° SAE/MS Positionable Male Elbow
Male Run Tee
Reducer
SAE/MS Positionable Male Branch Tee
Male Branch
Tee
Bulkhead Reducer
Cap
Plug
Female Connector SWAGELOK to AN Adapter
Heat Exchanger
Tee Bulkhead Female Connector Port Connector
Bore-Through Male Connector Used As Thermocouple Connector
Female Elbow Reducing Port Connector
Female Run Tee
KN Tube Fittings For Use on Polyethylene Tubing
SWAGELOK to Tube Socket Weld Union SWAGELOK to Tube Socket Weld Elbow
CHROMATOGRAPH FITTINGS Female Branch Tee
SWAGELOK to Male Pipe Weld Connector
SWAGELOK to Male Pipe Weld Elbow
Union
Union Union Tee O-Seal Male Connector Pipe Thread
Reducing Union
O-Seal Straight Thread Connector Zero Volume Column End Fitting Bulkhead Union © 1989 SWAGELOK Co., all rights reserved PF-2-087
Union Elbow
Swagelok® TUBE
FITTINGS
SWAGELOK to Female SWAGELOK Union
SWAGELOK Co., Solon, Ohio 44139 / SWAGELOK Canada Ltd., Ontario CIRCLE 130 ON READER SERVICE CARD
ANALYTICAL CHEMISTRY, VOL. 64, NO. 1, JANUARY 1, 1992 · 31 A
