For sample injection valves, switching valves, automatic injection valves, and accessories...
MOST MAJOR GC& LC MANUFACTURERS USE That's right. Valco is the Source selected by almost every major manufacturer for their gas and liquid chromatograph switching valves, sample injection valves, multifunction valves, and automatic sampling valves. Our new electronics including sequence programmers and temperature controllers, and our zero volume fittings are appearing on more and more new instruments. The reason is simple. No other supplier comes close to Valco in quality, reliability, performance, and overall capabilities. Whether you're planning replacement of your present valves or accessories, or upgrading your gas or liquid chromatograph, it makes sense to come to Valco.
VALCO
VALCO instruments co P O Box 19032 Houston. Tx 77024 713-688-9345 TWX: 910-881-5500 Telex: 79-0033
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ions have to satisfy separate and stringent requirements of both momentum and kinetic energy, thus offsetting the above S/N loss, at least with respect to chemical noise. Sensitivity and Quantitation The sensitivity of the MIKES technique has previously been estimated as 1 0 - 9 - 1 0 - n g from the S/N characteristics of peaks in the energy spectrum taken at known sample flux rates (28). This determination has now been repeated using total sample sizes in the nanogram range and measuring the S/N characteristics of selected peaks in the energy spectrum. Figure 7 shows results for cocaine, the determinations being made on the (M + H) + ion undergoing loss of C6H fi C0 2 H to yield the (M + H - 122)+ fragment ion. Even with total sample sizes on the order of 1 0 - 9 g, this and adjacent peaks in the MIKE spectrum can be recorded. The best sensitivity, and correspondingly the least specificity, in GC/MS is obtained by single ion monitoring. In this procedure the compound of interest is characterized by a single ion in its mass spectrum and by retention time data. A corresponding procedure of single reaction monitoring can be employed in MIKES. In this method the compound is characterized by the fact that it yields a particular ion (often the protonated molecule) which in turn
Rustrak miniature multichannel recorders
Record Volts, Amps, Pressure, Temperature, Events, More. Or any c o m b i n a t i o n s of these and many other parameters. You can record f r o m t w o up to eight channels of analog data, or up to four channels of analog and eight channels of event information. A wide variety of useful options and accessories
are available as well. Attention OEM's. C u s t o m m o u n t i n g arrangements, colors, nameplates, chart paper and scales available. New 32 Page Catalog. Provides details on DC, A C , Temperature, Servo, Multichannel, Event and a variety of special recorder types. Figure 7. Determination of sensitivity of MIKES using protonated cocaine by scanning the region of energy spectrum that includes collision-induced dissociation by loss of elements of benzoic acid Total sample placed on probe and multiplier voltage indicated
gulton® M e a s u r e m e n t & Control Systems Division Gulton Industries Inc., East Greenwich Rhode Island 02816 401 884 6800 · TWX 7 10 387 1 500
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90 A · ANALYTICAL CHEMISTRY, VOL. 50, NO. 1, JANUARY
1978
