Technical Specification: Buffers & Solutions
1. Product Overview
Solarbio buffers and solutions are manufactured for molecular biology, cell culture, and biochemical applications. Each solution is prepared at ISO 9001:2015 certified facilities using USP/EP-grade raw materials and USP-grade water (18.2 MΩ·cm, <5 ppb TOC). All buffers are 0.1 µm filtered, DNase/RNase-free, and tested for endotoxin content.
2. Product Range
| Product |
SKU |
Concentration |
Package Size |
Key Feature |
| PBS (Phosphate Buffered Saline) |
P1010 |
1×, pH 7.4 |
500 mL, 1000 mL |
Cell culture grade, Ca²⁺/Mg²⁺-free |
| 10× PBS |
P1020 |
10× concentrate |
500 mL |
Dilute to 1× with sterile water |
| TAE (Tris-Acetate-EDTA) |
T1060 |
50× concentrate |
500 mL, 1000 mL |
DNA electrophoresis, 40 mM Tris-acetate |
| TBE (Tris-Borate-EDTA) |
T1050 |
10× concentrate |
500 mL |
Higher resolution for small DNA fragments |
| 20× SSC |
S1030 |
20× concentrate |
500 mL |
Southern/Northern blotting, 3 M NaCl |
| 10× Tris Buffered Saline (TBS) |
T1080 |
10×, pH 7.4 |
500 mL |
Western blot wash buffer |
| 1 M Tris-HCl pH 8.0 |
T1120 |
1 M |
500 mL |
Molecular biology grade |
| 1 M Tris-HCl pH 7.4 |
T1150 |
1 M |
500 mL |
Biochemical assay buffer |
| 1 M HEPES pH 7.5 |
H1080 |
1 M |
500 mL |
Cell culture buffer |
3.1 PBS (1×, pH 7.4) — SKU P1010
| Component |
mM (1×) |
MW (g/mol) |
g/L |
Role |
| NaCl |
137 |
58.44 |
8.006 |
Osmotic balance |
| KCl |
2.7 |
74.55 |
0.201 |
Ionic balance |
| Na₂HPO₄ |
8.0 |
141.96 |
1.136 |
Buffering component |
| KH₂PO₄ |
2.0 |
136.09 |
0.272 |
Buffering component |
Target values: pH 7.4 ± 0.1 at 25°C; Osmolality 280–315 mOsm/kg; Conductivity 15.0–16.5 mS/cm.
3.2 TAE (50× Stock → 1× Working)
| Component |
mM (1×) |
mM (50×) |
MW (g/mol) |
g/L (50×) |
Role |
| Tris base |
40 |
2000 |
121.14 |
242.28 |
Buffering agent |
| Acetic acid |
— |
— |
60.05 |
57.1 mL/L (glacial) |
Counter-ion |
| EDTA |
1 |
50 |
372.24 (Na₂) |
18.61 |
Chelating agent |
Target: 1× TAE pH 8.3 ± 0.1 at 25°C.
3.3 TBE (10× Stock → 1× Working)
| Component |
mM (1×) |
mM (10×) |
MW (g/mol) |
g/L (10×) |
Role |
| Tris base |
89 |
890 |
121.14 |
108.0 |
Buffering agent |
| Boric acid |
89 |
890 |
61.83 |
55.0 |
Counter-ion |
| EDTA |
2 |
20 |
372.24 (Na₂) |
7.44 |
Chelating agent |
Target: 1× TBE pH 8.3 ± 0.1 at 25°C.
3.4 SSC (20× Stock → 1× Working)
| Component |
mM (20×) |
g/L (20×) |
Role |
| NaCl |
3000 |
175.3 |
Ionic strength for hybridization |
| Na₃·citrate·2H₂O |
300 |
88.2 |
Buffering and Ca²⁺ chelation |
Target: 20× SSC pH 7.0 ± 0.2 at 25°C.
3.5 TBS (10× Stock) — SKU T1080
| Component |
mM (10×) |
g/L (10×) |
Role |
| Tris base |
200 |
24.23 |
Buffering agent |
| NaCl |
1370 |
80.06 |
Ionic strength |
Target: 10× TBS pH 7.4 ± 0.1 at 25°C.
3.6 Tris-HCl (1 M) — SKUs T1120 (pH 8.0), T1150 (pH 7.4)
| Component |
Concentration |
MW (g/mol) |
g/L |
| Tris base |
1 M |
121.14 |
121.14 |
| HCl |
Titrate to target pH |
36.46 |
Variable |
3.7 HEPES (1 M, pH 7.5) — SKU H1080
| Component |
Concentration |
MW (g/mol) |
g/L |
| HEPES (free acid) |
1 M |
238.30 |
238.30 |
| NaOH |
Titrate to pH 7.5 |
40.00 |
Variable |
4. pH vs Temperature Coefficient
Buffer pH values shift with temperature — a critical parameter for reproducible results.
| Buffer |
ΔpH/°C |
pH at 4°C |
pH at 25°C |
pH at 37°C |
| Tris-HCl (nominal pH 8.0 at 25°C) |
−0.028 |
8.59 |
8.00 |
7.66 |
| Tris-HCl (nominal pH 7.4 at 25°C) |
−0.028 |
7.99 |
7.40 |
7.06 |
| HEPES |
−0.014 |
7.64 |
7.30 |
7.09 |
| PBS |
−0.0028 |
7.42 |
7.40 |
7.38 |
| Phosphate buffer (50 mM) |
−0.0028 |
— |
7.00 |
6.97 |
Note: Tris buffers exhibit a large negative coefficient. A Tris buffer prepared at pH 8.0 at 25°C will read pH 8.59 at 4°C and pH 7.66 at 37°C. Always adjust pH at the intended working temperature. HEPES has half the temperature sensitivity of Tris and is preferred for cell culture work at 37°C.
5. Storage After Opening — Stability Periods
| Product |
Unopened Stability (RT) |
After Opening (RT) |
After Opening (2–8°C) |
Notes |
| PBS, 1× |
24 months |
6 months |
12 months |
Discard if turbid |
| PBS, 10× |
24 months |
12 months |
24 months |
Concentrate more resistant |
| TAE, 50× |
24 months |
6 months |
12 months |
EDTA may precipitate if chilled |
| TBE, 10× |
24 months |
6 months |
6 months |
Borate may crystallize at 4°C |
| SSC, 20× |
24 months |
12 months |
18 months |
Stable concentrate |
| TBS, 10× |
24 months |
12 months |
24 months |
Stable concentrate |
| TBS-T (with Tween 20) |
18 months |
3 months |
6 months |
Tween 20 may hydrolyze over time |
| 1 M Tris-HCl |
24 months |
12 months |
12 months |
Discard if precipitate forms |
| 1 M HEPES |
24 months |
12 months |
18 months |
Stable; light-sensitive over long storage |
6. Application-Specific Guidance
| Buffer |
Recommended For |
Not Recommended For |
Reason |
| TAE |
Standard agarose gel electrophoresis (0.7–2% agarose); DNA recovery from gels |
High-resolution separation of <300 bp fragments |
Lower buffering capacity than TBE; bands blur in long runs |
| TBE |
High-resolution gel electrophoresis; small DNA fragments (100–500 bp); native PAGE |
Preparative gel purification |
Borate inhibits ligation; remove by ethanol precipitation |
| PBS |
Cell washing, immunofluorescence, immunohistochemistry, ELISA washing |
Long-term cell incubation (lacks nutrients, Ca²⁺, Mg²⁺) |
Only for wash steps; use DMEM/RPMI for incubation |
| SSC |
Southern blot, Northern blot, colony hybridization |
Cell culture |
High salt interferes with biological systems |
| TBS |
Western blot wash, ELISA, protein purification (ion exchange) |
Immunofluorescence (may cause background) |
Use PBS for IF |
| Tris-HCl |
Biochemical enzyme assays, DNA/RNA solubilization, protein purification |
Cell culture medium preparation (low buffering at 37°C) |
Use HEPES or carbonate for culture |
| HEPES |
Cell culture medium (37°C), live-cell imaging, electrophysiology |
Electrophoresis running buffers |
Poor conductivity for gels |
7. Buffer Selection Guide by Downstream Application
| Downstream Application |
Recommended Buffer |
Alternative Buffer |
Key Selection Criteria |
| DNA agarose gel electrophoresis |
1× TAE |
0.5× TBE |
TAE for DNA recovery; TBE for fine resolution |
| Native PAGE |
1× TBE |
1× TAE |
TBE gives sharper bands in polyacrylamide |
| Western blot — transfer |
1× Transfer buffer (Tris-glycine-SDS) |
1× TBS |
Dedicated transfer buffer required |
| Western blot — wash |
1× TBS-T |
1× PBS-T |
TBS-T preferred for reduced background |
| ELISA — coating |
50 mM carbonate-bicarbonate pH 9.6 |
1× PBS |
Carbonate for alkaline pH coating |
| ELISA — wash |
1× PBS-T |
1× TBS-T |
PBS-T is standard for ELISA |
| Immunofluorescence |
1× PBS |
1× TBS |
PBS standard; TBS if phosphate interferes |
| Cell culture medium |
HEPES-buffered DMEM/RPMI |
CO₂-bicarbonate system |
HEPES for atmospheric CO₂ experiments |
| Southern/Northern blot |
20× SSC |
20× SSPE |
SSC is more widely established |
| Chromatin immunoprecipitation (ChIP) |
ChIP lysis buffer + 1× PBS |
— |
Use dedicated shearing buffers |
| Protein purification (IMAC) |
50 mM Tris, 300 mM NaCl, pH 8.0 |
50 mM phosphate, 300 mM NaCl |
Tris for imidazole gradient elution |
| Protein purification (IEX) |
20 mM Tris (anion) or 50 mM MES (cation) |
— |
Match buffer to pI of target protein |
8. Quality Release Specifications
Every lot of Solarbio buffer and solution undergoes quantitative release testing against the following specifications.
| Parameter |
PBS (1×) |
TAE (50×) |
TBE (10×) |
Tris-HCl (1 M) |
HEPES (1 M) |
Test Method |
| pH at 25°C |
7.40 ± 0.10 |
8.30 ± 0.10 |
8.30 ± 0.10 |
8.00 ± 0.05 / 7.40 ± 0.05 |
7.50 ± 0.05 |
Three-point calibrated pH meter |
| Conductivity |
15.8 ± 0.8 mS/cm |
— |
— |
— |
— |
Conductivity meter, ±2% |
| Osmolality |
298 ± 15 mOsm/kg |
— |
— |
— |
— |
Freezing point depression |
| Absorbance 260 nm |
<0.05 AU |
<0.10 AU |
<0.10 AU |
<0.05 AU |
<0.05 AU |
UV-Vis, 1 cm path |
| Absorbance 280 nm |
<0.05 AU |
<0.10 AU |
<0.10 AU |
<0.05 AU |
<0.05 AU |
UV-Vis, 1 cm path |
| Endotoxin |
<0.5 EU/mL |
<1.0 EU/mL |
<1.0 EU/mL |
<0.5 EU/mL |
<0.5 EU/mL |
LAL chromogenic (USP <85>) |
| DNase |
Not detectable |
Not detectable |
Not detectable |
Not detectable |
Not detectable |
Fluorogenic substrate assay |
| RNase |
Not detectable |
Not detectable |
Not detectable |
Not detectable |
Not detectable |
Fluorogenic substrate assay |
| Protease |
Not detectable |
Not detectable |
Not detectable |
Not detectable |
Not detectable |
Resorufin-casein assay |
| Sterility |
0.1 µm filtered |
0.1 µm filtered |
0.1 µm filtered |
0.1 µm filtered |
0.1 µm filtered |
Membrane filtration, 14-day |
Acceptance criteria: A lot passes only when all parameters fall within specification. Failed parameters trigger a formal OOS investigation and lot rejection.
9. Common Mistakes and Troubleshooting
| Problem |
Likely Cause |
Solution |
| White precipitate in PBS after refrigeration |
K⁺/phosphate crystallization at low temperature; concentration error |
Warm to RT and swirl to redissolve. Recheck osmolality before use. |
| pH drift >0.2 units after 24 h |
Wrong storage temperature; container not sealed; CO₂ absorption (PBS/TBS) |
Always seal tightly. For alkaline Tris buffers, minimize exposure to air. pH can drift 0.1–0.3 units over days if left open. |
| TAE buffer overheats during electrophoresis |
EDTA concentration too low; insufficient buffering capacity |
Use fresh 1× TAE. Do not reuse running buffer more than 2–3 times. For long (>2 h) runs, recirculate or use 1.5× TAE. |
| No bands visible on gel (TBE) |
Borate inhibition of enzymatic downstream steps |
Borate can inhibit ligation, restriction digestion, and sequencing. Ethanol precipitate DNA after TBE electrophoresis before downstream steps. |
| High background in Western blot (TBS-T) |
Tween 20 concentration too high; blocking insufficient |
Use 0.1% Tween 20 (not 0.5%). Increase blocking time to 1 h at RT or overnight at 4°C. |
| HEPES buffer turns yellow on storage |
Exposure to light — HEPES photodegradation products |
Store in amber bottle. Use fresh buffer for critical cell culture experiments. |
| SSC buffer supports bacterial growth |
Contamination introduced during handling |
Filter-sterilize (0.22 µm) after preparation. Add 0.02% sodium azide for long-term storage (note: toxic). |
| Tris-HCl precipitate forms at 4°C |
Tris base crystallizes at low temperature when concentrated (>0.5 M) |
Warm to 37°C and mix. Do not use heat above 50°C. |
| Osmolality out of range |
Pipetting error in NaCl or sugar component |
Re-measure osmolality. ±5% is acceptable. If outside ±10%, discard and prepare fresh. |
| pH meter calibration errors |
Electrode aged; calibration buffers expired |
Calibrate with fresh pH 4.0, 7.0, and 10.0 standards daily. Use temperature compensation at 25°C. |
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