
Hanna Instruments-70004P pH 4.01 Buffer Sachets, 25 x 20 mL sachets
Achieve accurate pH readings and check your meter and electrode is functioning correctly with Hanna buffer solutions. Available in convenient, ready-made pH values 4.01, 6.86, 7.01, 9.28 and 10.01, Hanna has a certified value calibration solution with an accuracy of +/- 0.01pH @ 25◦C for all requirements.
*For even greater accuracy, scroll down to read Hanna’s Technical and Millesimal Buffer range explained.
Hanna Instruments-70004P – 25 x 20ml sachets pH 4.01 buffer solution
The pH 4.01 buffer solution is available in quick and easy to use 20ml sachets, one of the most commonly used buffer solutions. It is extremely stable and represents the mid-way point in the acid range of the pH scale - ideal for those requiring an accurate acid reading, particularly those working in water purification plants, the food industry, and wherever the pH is expected to be acidic.
The single dose sachets are really handy with each sealed sachet holding just the right amount of solution. Each time a meter or electrode is calibrated using a Hanna sachets, it is like using a newly opened bottle of solution!
Benefits of individual packaging
- Ideal for users who do not calibrate frequently
- Ideal for field use due to portability
- Every sachet is as fresh as the day it was packaged
- Light block packaging prevents oxidation from UV light that could alter the buffer value.
Buffer solutions should be stored at 25 C, away from direct sunlight for accurate readings.
To correctly maintain your meter/electrode, we highly recommend use of a Hanna cleaning solution, as well as a buffer, for maximum performance every time. pH4, along with pH7, can also be used as an emergency storage solution.
Hanna buffer solutions are prepared, ready-to-use, according to precise formulas and standardised in accordance with the National Institute of Standards and Technology (NIST) to ensure quality and accuracy. All solutions show a batch number, an expiry date, and the correlation table between pH and temperature. A certificate of analysis is available on request. All bottled solutions are sealed with an air tight, tamper-proof seal to prevent any Carbon Dioxide from entering and causing a change in the pH buffer value.
Browse the Hanna complete range of solutions
- pH buffer solutions
- Standard solutions for conductivity, Total Dissolved Solids (TDS), turbidity, salinity and Ion-Selective Electrode (ISE) calibration
- Oxidation Reduction Potential (ORP) test and pre-treatment solutions
- Reference fill solutions for refillable electrodes
- General and specific cleaning solutions for electrodes
- Solutions for electrode maintenance and storage
- Solutions for sample preparation
Solutions are available in many sizes ranging from 20ml sachets for small users to 3.78L (1 gallon) containers for large quantity usage in laboratories.
For safety and traceability, all Hanna solutions are provided with a label showing the batch number and expiry date. A certificate of analysis is available on request in line with NIST standards.
Remember:
- Calibration only counts when using fresh solutions and properly cleaned electrodes every time.
- Routine maintenance will ensure accurate readings while extending the life of the electrode
Useful information:
Colour Coding for 1L and 1 gallon bottles:
pH 4.01 - Red
pH 7.01 - Green
pH 10.01 – Violet
All calibration buffers are made to a premium quality, produced in accordance with ISO 3696/BS3978 standards using high purity salts, deionised water, certified weight-checked balances, and Class A glassware in a temperature controlled environment monitored with certified thermometers.
All bottles meet with FDA Standards (US Food and Drug Administration).
*Millesimal and Technical Buffer solutions explained
Designed and manufactured for those where accuracy really is vital, Millesimal buffer solutions are produced to a premium quality for customers who require a greater resolution of 0.001 for pH measurements. Accuracy can be guaranteed at +/- 0.002 @ 25 C.
To achieve the more accurate results, Millesimal Buffer solutions are available in pH1.000, pH1.679, pH2.000, pH3.000, pH4.010, pH6.000, pH6.862, pH7.010, pH8.000, pH10.010, pH11.000, pH12.000, pH12.450, pH13.000.
For those requiring a greater spectrum, as well as increased accuracy to readings, Hanna also manufacture a Technical Buffer solution range which share the accuracy of standard buffers, +/- 0.01 @ 25 C, and feature two extra pH levels, pH1.00 and pH5.01, along with pH4.01, pH6.86, pH7.01, and pH10.01.
Both technical and Millesimal buffer solutions come with a certificate of analysis on purchase.

Frequently Asked Questions
Clear answers to help you choose the right water testing solution with confidence
Which brands of water testing kits do you supply?
Do you provide kits for both home and professional use?
Yes — whether you’re a pool or spa owner, aquarium keeper, utility company, or a university laboratory, we have the right solution for your needs.
Can I arrange servicing or calibration for my photometer?
Absolutely. We also provide servicing and calibration to keep your photometers accurate and reliable.
How quickly do you dispatch orders?
Orders placed before 2:30 pm (Monday–Friday) are dispatched the same day. We also ship on Saturdays for your convenience.
Which couriers do you use for delivery?
We deliver through UPS, DPD, and Royal Mail. You can also choose to upgrade to next-day delivery at checkout.
What is your return policy?
We accept returns within 14 days of delivery provided the items are unused, in their original packaging, and in resalable condition. Please contact our team before returning any items.
Can I place bulk or business orders?
Yes, we welcome bulk, trade, and institutional orders. For tailored pricing or large quantities, please get in touch with us directly.
How can I get help if I’m unsure which kit to buy?
You can call us at 📞 +44 (0)115888 2726 and our team will guide you in choosing the most suitable kit for your needs.