Ammonium dihydrogenphosphate

Pockels cells consist of potassium- or ammonium-dihydrogenphosphate which are very sensitive to humidity and temperature changes. The problem here is to get good adhesion to these difficult materials. The area resistance required is 1-10 kQllF1. 

Catanac SP is stearamidopropyl-dimethyl-P-hydroxyethyl-ammonium dihydrogenphosphate ... 

Ammonium dihydrogenphosphate. Thallium hydrogenphosphate. Commercial names of multilayer systems. 

For the library samples that contain very polar by-products, excess reagents, or impurities, an ion-pair reagent may be added to the mobile phase to improve retention of the polar components on the reversed-phase HPLC column. For small polar basic components such as amines, 0.1-1% of heptafluorobutyric acid can be added into the mobile phase containing acetonitrile or methanol in water. For small polar acidic components such as carboxylic acids, 5-20 mM of tetrabutyl-ammonium dihydrogenphosphate can be added into the mobile phase containing acetonitrile or methanol in 50 mM phosphate buffer (pH 7.4). 

Liau et al. (76) compared amperometric and UV detection for ascorbic acid analysis. Their chromatographic system consisted of a C18 column and ammonium dihydrogenphosphate buffer with 0.015% MPA. For electrochemical detection they adjusted the pH of the mobile phase to 2.55 and for UV detection to 2.95. The amperometric detector was set at 700 mV versus Ag/AgCl reference electrode. The UV detector was set at 245 nm. They preferred relatively simple mobile phase without ion-pairing reagents which tended to precipitate with MPA that was present in mobile phase as well as in plasma sample for stabilization. Ascorbic acid was weU measurable with both detectors. The detection limit for electrochemical detection was 0.3 ng and for UV detection 1.2 ng per injection. The coefficient of variation (CV) for the between-day assay was <12% using electrochemical detection and <5% using UV detection. They conclude that UV detection is apparently a better choice for fast, routine measurements of ascorbic acid concentrations. Electrochemical detection takes more time to stabilize, but is more sensitive. 

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