Nitric AcidGastric AcidSpectrophotometry, AtomicNeodymiumDecalcification TechniqueHydrofluoric AcidPentagastrinHydrochloric AcidSulfuric AcidsGastric JuiceGastrinsTrace ElementsNitratesGastric MucosaMicrowavesAcid-Base EquilibriumCalibrationGastric Acidity DeterminationEnvironmental MonitoringParietal Cells, GastricAcid-Base Imbalance