Reference
Laboratory Reference Tables
Traceable bench reference values — physical constants, absorbance factors, purity ranges, SI prefixes, concentration and dilution forms, and common conversions. Every table names its source and its evidence tier.
Source evidence tiers — T1: international standards and national metrology institutes. T2: peer-reviewed literature and consensus method standards. T3: authoritative laboratory manuals and textbooks. T4: secondary compilations and practitioner references.
Physical constants
Exact and CODATA-recommended values used in molecular calculations.
| Name | Value | Unit / note |
|---|---|---|
| Avogadro constant (Nₐ) | 6.02214076 × 10²³ | mol⁻¹ — Exact by SI definition (2019). |
| Elementary charge (e) | 1.602176634 × 10⁻¹⁹ | C — Exact by SI definition. |
| Boltzmann constant (k) | 1.380649 × 10⁻²³ | J·K⁻¹ — Exact by SI definition. |
| Gas constant (R) | 8.314462618 | J·mol⁻¹·K⁻¹ — Derived: R = Nₐ·k. |
| Planck constant (h) | 6.62607015 × 10⁻³⁴ | J·s — Exact by SI definition. |
| Faraday constant (F) | 96485.33212 | C·mol⁻¹ — Derived: F = Nₐ·e. |
| Atomic mass constant (u) | 1.66053906892 × 10⁻²⁷ | kg — CODATA 2022 recommended value. |
| Molar volume of an ideal gas (Vₘ) | 22.71095464 | L·mol⁻¹ — Ideal gas at 0 °C and 100 kPa; Vₘ = R·T / p. |
Nucleic acid & protein absorbance factors
Concentration represented by one absorbance unit (A₂₆₀/A₂₈₀) in a 1 cm path length.
| Name | Value | Unit / note |
|---|---|---|
| Double-stranded DNA | 50 | µg/mL per A260 |
| Single-stranded DNA | 33 | µg/mL per A260 |
| RNA | 40 | µg/mL per A260 |
| Oligonucleotide (per mole) | ≈ 10,000 × n | M⁻¹·cm⁻¹ — Rough ε from base count; use nearest-neighbour for precision. |
| Pure protein (typical) | 0.7–1.4 | E(1 mg/mL) — Varies with Trp/Tyr/Cys content — use the protein's own coefficient. |
A260/A280 purity ranges
Indicative ranges for uncontaminated nucleic acid preparations.
| Name | Value | Unit / note |
|---|---|---|
| Pure dsDNA | 1.8 | Typical acceptable range 1.7–2.0. |
| Pure ssDNA | 1.9 | Typical acceptable range 1.8–2.0. |
| Pure RNA | 2.0 | Typical acceptable range 1.9–2.1. |
| Protein contamination | < 1.7 | Low ratio suggests protein/phenol carryover. |
SI prefixes
Metric prefixes most used at the bench.
| Name | Value | Unit / note |
|---|---|---|
| giga (G) | 10⁹ | |
| mega (M) | 10⁶ | |
| kilo (k) | 10³ | |
| hecto (h) | 10² | |
| deca (da) | 10¹ | |
| deci (d) | 10⁻¹ | |
| centi (c) | 10⁻² | |
| milli (m) | 10⁻³ | |
| micro (µ) | 10⁻⁶ | |
| nano (n) | 10⁻⁹ | |
| pico (p) | 10⁻¹² | |
| femto (f) | 10⁻¹⁵ | |
| atto (a) | 10⁻¹⁸ | |
| Added in 2022 (Q, R, r, q) | 10³⁰, 10²⁷, 10⁻²⁷, 10⁻³⁰ | quetta, ronna, ronto and quecto — CGPM Resolution 3 (2022). |
Common laboratory conversions
Frequently-needed equivalences.
| Name | Value | Unit / note |
|---|---|---|
| Volume | 1 mL = 1000 µL = 1 cm³ | |
| Mass | 1 g = 1000 mg = 10⁶ µg | |
| Mass of water | 1 µL H₂O ≈ 1 mg (4 °C) | |
| Molarity | 1 M = 1 mol/L = 1000 mM | |
| Molar subunits | 1 mM = 1000 µM; 1 µM = 1000 nM | |
| Temperature | °C = (°F − 32) × 5/9 | |
| Absolute zero | 0 K = −273.15 °C | |
| Pressure | 1 bar = 10⁵ Pa; 1 atm = 101 325 Pa |
Concentration expressions
How each bench concentration form is defined.
| Name | Value | Unit / note |
|---|---|---|
| Molar (c) | 1 M = 1 mol·L⁻¹ | Amount of solute per litre of solution. |
| Mass per volume (% (w/v)) | 1 % (w/v) = 10 g·L⁻¹ | Grams of solute per 100 mL of solution. |
| Volume per volume (% (v/v)) | 1 % (v/v) = 10 mL·L⁻¹ | Millilitres of solute per litre of solution. |
| Mass fraction (% (w/w)) | 1 % (w/w) = 10 g·kg⁻¹ | Grams of solute per kilogram of solution. |
| Dilution factor (DF) | C₁V₁ = C₂V₂ | Amount conserved across a dilution step. |
Serial dilution reference
Cumulative dilutions used when plating samples and preparing assay series.
| Name | Value | Unit / note |
|---|---|---|
| Single 1:10 step (10⁻¹) | DF = 10 | 1 volume of sample into 9 volumes of diluent. |
| Two 1:10 steps (10⁻²) | DF = 100 | |
| Three 1:10 steps (10⁻³) | DF = 1000 | |
| Four 1:10 steps (10⁻⁴) | DF = 10 000 | |
| Five 1:10 steps (10⁻⁵) | DF = 100 000 | |
| Six 1:10 steps (10⁻⁶) | DF = 1 000 000 | |
| Two-fold step (½) | DF = 2 | 1 volume of sample into 1 volume of diluent. |
| Countable plate range | 30–300 | CFU/plate — Convention for aerobic plate counts. |
Normal quantile reference
Standard-normal values used for significance and power.
| Name | Value | Unit / note |
|---|---|---|
| Two-sided 95 % limit (z(0.975)) | 1.959964 | Bounds the central 95 % of a standard normal distribution. |
| One-sided 5 % limit (z(0.95)) | 1.644854 | Upper-tail critical value for a one-sided test. |
| 80 % power (z(0.80)) | 0.841621 | The 80th percentile of the standard normal distribution. |
| 90 % power (z(0.90)) | 1.281552 | The 90th percentile of the standard normal distribution. |
Reference values for research and educational use. Verify against the cited primary source before use in critical applications.