Genuine HORIBA ion standard solutions for calibrating ion-selective electrodes on LAQUA handheld and benchtop meters. Each 500 mL bottle is supplied at a certified concentration so you can build a two-point calibration across the range you actually measure.

Every ion is available in two strengths — 1000 mg/L (suffix SH, high) and 100 mg/L (suffix SL, low). Ion-selective electrodes respond logarithmically to concentration, so calibrating at two points a decade apart is what establishes the slope of that response. A single-point calibration only sets an offset and will give increasingly wrong answers the further your sample sits from that one point.

Available ions

• Ammonium (NH₄⁺) — 1000 and 100 mg/L
• Calcium (Ca²⁺) — 1000 and 100 mg/L
• Chloride (Cl⁻) — 1000 and 100 mg/L
• Fluoride (F⁻) — 1000 and 100 mg/L
• Nitrate (NO₃⁻) — 1000 and 100 mg/L
• Potassium (K⁺) — 1000 and 100 mg/L
• Sodium (Na⁺) — 1000 and 100 mg/L

Bracket your samples

Choose the pair of standards that spans your expected sample concentrations. If your samples typically fall between 5 and 50 mg/L, calibrate with the 100 mg/L standard and a dilution of it rather than with the 1000 mg/L standard — extrapolating well below the calibrated range is where ISE measurements most often go wrong. Prepare dilutions with deionized water and use them the same day.

Use an ionic strength adjustor

An ISE responds to ion activity, not total concentration, and activity depends on the ionic strength of the solution. Adding the matching ionic strength adjustor (ISA, or TISAB for fluoride) to both your standards and your samples in equal proportion brings them to a common ionic strength so the comparison is valid. Skipping this step is the most common cause of ISE results that look plausible but read consistently low. Adjustors are listed separately.

Applications

• Nutrient monitoring — nitrate and ammonium in surface water, groundwater and effluent
• Drinking water fluoride compliance monitoring
• Chloride determination in water, brines and process streams
• Calcium and hardness-related measurements in treatment and boiler water
• Sodium monitoring in high-purity water, boiler feed and condensate
• Potassium and nutrient analysis in agriculture, soil extracts and hydroponics
• Routine ISE verification under a laboratory quality system

Related items

Ion-selective electrode kits, replacement ISE cartridges and membranes, ionic strength adjustors and ISE filling solutions are all stocked — see the Horiba Parts & Accessories collection.

Browse all HORIBA instruments.