A handheld device provides for measuring the concentration of dialdehyde in a dialdehyde solution. The device comprises (a) an optically transparent first container being under vacuum whereby to draw in a first predetermined quantity of the dialdehyde solution; (b) a first light source positioned to transmit light in the range of 420 nm to 620 nm through the optically transparent first container; (c) a first sensor positioned to receive the transmitted light, wherein the first sensor is configured to measure an optical absorbance of the transmitted light and configured to transmit an electronic signal proportional to the optical absorbance; and (d) a microprocessor in electronic communication with the first sensor, wherein the microprocessor is configured to indicate the concentration of the dialdehyde in the dialdehyde solution based on the electronic signal received from the first sensor.