The present invention relates to a portable arsenic detection system and a method of detecting the presence of arsenic in an aqueous sample more particularly for measuring the arsenic concentration in quantitative measurements. Based on these and other discoveries, the present invention is directed to an improved method for the analysis of arsenic, that beneficially can provide a higher percentage of arsine gas production in a comparable or significantly shorter (for example, ten minutes) time period. Furthermore, because of relatively increased arsine gas production, the inventive method can provide increased sensitivity for low levels of arsenic. Thus, this method is useful for low levels of arsenic in the range of about 10 ppb, as well as for higher levels of arsenic up to 50 or 100 ppb or more, even in excess of 500 ppb. Moreover, in a preferred aspect, the inventive method relies upon a non-corrosive type acid reagent. Also in accordance with the inventive method, the arsenic reduction reaction may be controlled whereby, for instance, undesired splashing of the reaction mixture is reduced. In addition, the inventive method can provide greater reproducibility of results. The portable arsenic detection system has been developed to provide more accurate results as the output is digital value which overcome the false positive problems preparation procedures for quantitative detection of low levels of arsenic contamination in water. The portable arsenic detection system is designed for convenience of use in the field. The chemical reagents selected for the portable arsenic detection system are widely available.