Nitrate calibration solution or calibration standard is needed to calibrate nitrate meters for extra precision.
Nitrate 150 ppm calibration solution that will last up to 300 calibrations of LAQUAtwin meters. Equivalent solution of HORIBA calibration solution Y045L. 
We recommend calibrating your LAQUAtwin Nitrate meter daily (if you measure daily) or after every 10 measurements within a single day if you are testing more intensively.
 
⚫ Volume: 60 ml bottle with a twist top cap
⚫ Standard solution concentration: 150 ppm (150 mg/L) of Nitrate (NO3-)
⚫ Can be used to calibrate the meter at 450 ppm of NO3-N
⚫ Compatible with HORIBA LAQUAtwin NO3-11 and B-743
⚫ Made in USA