Knowledge
Method notes, standards analysis and practical guidance on constant-weight testing and barrier performance — written by LabStone engineers.
Oxygen Transmission Rate by Coulometric Sensor: Inside ASTM D3985
ASTM D3985 is the standard test method for the oxygen transmission rate (OTR) of plastic films, sheeting and laminates using a coulometric sensor, with the current edition D3985-24. This article walks through the working principle based on Faraday's law, the standard test condition of 23 °C, 0% RH and a 50 cm² specimen with at least 48 hours of dry preconditioning, carrier and oxygen flow parameters, the OTR calculation, NIST-traceable calibration, the metal-foil leak check, typical interlaboratory precision data, and how the equal-pressure method compares with differential-pressure procedures and ISO 15105-2.
2026-11-04Packaging Mechanics TestingPlastic Laminated Films and Pouches: What the 2026 General Standard Changes
China's general standard for plastic laminated films and pouches was published on 30 July 2026 and takes effect on 1 February 2027, replacing the 2007 edition. The revision classifies products by service temperature, grades six mechanical properties on a five-point scale with grade 5 now highest — the reverse of the old convention — grades WVTR and OTR on five levels with named arbitration methods, and requires retort grades to keep peel and seal strength at or above grade limits after heat treatment. What changes, what stays, and how QC labs should prepare.
2026-11-02Packaging Mechanics TestingPeel Strength Testing of Flexible Laminated Plastics: Method, Specimens and Speeds
How peel strength is measured on flexible laminated plastics: a constant-speed T-peel on pre-stripped 15 mm specimens, with the average force over the peel curve expressed per unit width. The 2026 revision of China's peel method standard adds a parallel peel mode, widens specimens to six sizes from 10 to 50 mm, sets five speed steps from 100 to 500 mm/min and upgrades equipment requirements — what QC labs for food, pharma and battery laminates need to know, including the pharmaceutical limit of 8.0 N per 15 mm.
2026-10-30Constant Weight TestingAsh Content Testing of Pharmaceutical Rubber Closures: Method, Temperature and Limits
How ash content is determined for pharmaceutical rubber closures: 1.0 g of cut sample carbonized gently, then ignited at 800 °C ± 25 °C to constant weight, with the ash percentage calculated from the residue mass. Sample preparation, the 0.3 mg constant-weight criterion, a draft revision moving to a fixed 2-hour ignition, the boundary against residue-on-ignition and ISO 247, plus what automation changes for the QC lab.
2026-10-28Constant Weight TestingNon-Volatile Residue Testing of Pharmaceutical Packaging Films: Extraction Methods and Limits Explained
How non-volatile residue is determined for pharmaceutical packaging films: 600 cm² extraction in water, 65% ethanol and n-hexane with a 30.0 mg residue-versus-blank allowance for general laminated films, and a far tighter 2.5 mg limit after 121 °C autoclave extraction for infusion-grade co-extruded film and bag materials. Sample preparation, the 105 °C drying step, constant-weight criteria and companion metrics, plus what automation changes for the QC lab.
2026-10-26Packaging Mechanics TestingPackage Seal Integrity Testing: Underwater Bubble and Vacuum Decay Methods Explained
How package seal integrity is tested: the underwater bubble method for locating leaks under vacuum, and the quantitative, non-destructive vacuum decay method (decay rate Q in Pa/s) recognised by ASTM F2338. Method principles, pass criteria, instrument requirements and selection logic.
2026-10-23Barrier PerformanceHow Is Pharmaceutical Packaging Barrier Tested? WVTR and Gas Transmission Methods Explained
How pharmaceutical packaging films are tested for water vapour and oxygen barrier: gravimetric cup, electrolytic and infrared WVTR methods (23 °C/90 % RH, high-barrier sheets ≤2.5 g/(m²·24h)), differential-pressure gas transmission (≤30 cm³/(m²·24h·0.1 MPa)), with conditions, limits and instrument selection.
2026-10-21Constant Weight TestingHow Is Total Migration and Non-Volatile Residue Measured? The 105 °C Water-Bath Gravimetric Workflow
The full standard procedure for overall migration and non-volatile residue, the difference between the 0.5 mg and 0.3 mg constant-weight criteria, the precision clause, the olive oil part and the chloroform extract decision rule, with the underlying Chinese food contact standards.
2026-10-19Barrier PerformanceWhat Is Water Vapor Transmission Rate (WVTR)? Definition, Units and Test Methods
Water Vapor Transmission Rate (WVTR) is the mass of water vapor passing through a unit area of packaging material per unit time under specified temperature and humidity conditions, commonly expressed in g/(m²·24h). WVTR is the core indicator of moisture-barrier performance: the lower the value, the better the moisture barrier and the longer the shelf life of moisture-sensitive products (biscuits, milk powder, effervescent tablets, traditional medicine). The reference test method is the gravimetric cup method per ASTM E96/E96M-24a, ISO 2528:2017 and GB/T 1037-2021; instrument methods include the modulated infrared sensor method (ASTM F1249, ISO 15106-2) and the electrolytic sensor method (ISO 15106-3).
2026-10-19Barrier PerformanceWhat Is Electrolytic WVTR Testing? Principle and Applications of ISO 15106-3
The electrolytic method is one of the instrumental methods for water vapor transmission rate: the specimen splits the test cell into a wet side and a dry side, water vapor passing through the specimen is carried by dry carrier gas into an electrolysis cell, where it is absorbed by a phosphorus pentoxide (P₂O₅) film and electrolyzed; per Faraday's law the electrolysis current is directly proportional to the transmission rate and converts straight into WVTR. The reference standards are ISO 15106-3:2003 and ASTM F3299. The method is extremely sensitive (commercial instruments reach detection limits on the order of 0.001 g/(m²·24h)) and suits high-barrier materials: pharmaceutical blister foil, metallized film, PVDC/EVOH laminates, solar backsheets and OLED encapsulation films.
2026-10-19Barrier PerformanceGravimetric Cup Methods for WVTR: Gain or Loss? Key Points of ASTM E96 and ISO 2528
The gravimetric cup method is the reference method for water vapor transmission rate: the specimen is sealed over a cup containing a desiccant or water, the assembly is held in a controlled climate, and the cup is weighed periodically; the slope of the mass–time curve gives the WVTR. The Desiccant Method (gain, dry cup) keeps the inside near 0% RH — vapor enters and the cup gains mass; the Water Method (loss, wet cup) keeps the inside near 100% RH — vapor escapes and the cup loses mass. ASTM E96/E96M-24a specifies both procedures; ISO 2528:2017 is the corresponding international dish method. It suits mid-to-high transmission materials (about 1–1000 g/(m²·24h)) and underpins inter-laboratory comparison and arbitration testing.
2026-10-16Barrier PerformanceWhat Is Oxygen Transmission Rate (OTR)? Definition, Units and Coulometric Testing
Oxygen Transmission Rate (OTR) is the amount of oxygen passing through a unit area of packaging material per unit time under specified temperature, humidity and oxygen concentration gradient, commonly expressed in cm³/(m²·24h). OTR is the core indicator of oxygen-barrier performance: the lower the value, the better the barrier and the longer the shelf life of oxygen-sensitive products (fatty foods, infant formula, oxidation-prone pharmaceuticals). The reference test method is the coulometric (electric) method per ASTM D3985 and ISO 15105-2.
2026-10-16Barrier PerformanceWhat Is Gas Transmission Rate (GTR)? Definition and Differential-Pressure Testing
Gas Transmission Rate (GTR) is the volume of gas passing through a unit area of specimen per unit time under specified temperature and pressure differential, commonly expressed in cm³/(m²·24h·0.1MPa). It measures a packaging material's gas-barrier capability: the lower the value, the better the barrier. The classic test method is the differential-pressure method ( 1038, ASTM D1434, ISO 2556), which handles oxygen, carbon dioxide, nitrogen, hydrogen, helium, air and more — one instrument covers many gases.
2026-10-16Barrier PerformanceHow Many Names Does Oxygen Transmission Have? OTR, Permeance and Permeability Coefficient Explained
One oxygen transmission tester can report OTR, permeance, permeability coefficient, transmission rate and gas transmission rate. This article explains each term, its unit and how the standards ASTM D3985, ASTM D1434, ISO 15105-2 and ISO 2556 define them, so you can read a test report with confidence.
2026-10-14Barrier PerformanceWhat Is ASTM F1249? Water Vapor Transmission Rate by Modulated Infrared Sensor
ASTM F1249, 'Standard Test Method for Water Vapor Transmission Rate Through Plastic Film and Sheeting Using a Modulated Infrared Sensor,' is the reference method for measuring water vapor passing through plastic films and sheets up to 3 mm thick. The specimen separates a humidified wet chamber (37.8°C ± 0.5°C, 90% RH ± 2%) from a dry nitrogen-purged side; permeated vapor is carried to a modulated infrared sensor (~1.94 µm) and quantified, results in g/m²·day. This note explains scope, principle, test conditions, steady-state criteria, comparison with other WVTR methods and the LabStone solution.
2026-10-14Constant Weight TestingWhat Is Loss on Drying (LOD)? Definition, Formula and the 0.3 mg Constant-Weight Endpoint
Loss on Drying (LOD) is the mass a sample loses after being dried to constant weight under specified temperature and time, expressed as a percentage. It measures total volatiles – not just water but also organic solvents such as ethanol driven off by heat – and is a key purity and stability test for pharma, food and chemical products.
2026-10-14Constant Weight TestingWhat Is Moisture Content? How It Differs from Loss on Drying and How It Is Measured
Moisture content refers only to the percentage of water by mass in a sample, excluding volatile organic compounds such as ethanol. It differs from Loss on Drying (LOD): LOD includes all volatiles, moisture targets H₂O specifically. It is measured by Karl Fischer titration (coulometric or volumetric), oven drying, or a trace moisture meter.
2026-10-14Constant Weight TestingWhat Is Constant Weight? The Pharmacopoeia Endpoint, the 0.3 mg Criterion and Drying Time
Constant weight is the state where the mass difference between two successive weighings does not exceed the allowed value (pharmacopoeia: usually 0.3 mg). It is not a time concept but a stability endpoint: re-weigh at ≥ 1 h intervals until two consecutive values differ by < 0.3 mg.
2026-10-14Constant Weight TestingWhat Does 0.3 mg Constant Weight Mean? Origin, Operating Detail and Balance Selection of the Two-Run Criterion
0.3 mg constant weight is the rule that a sample is considered to have reached its endpoint when two successive weighings, after drying or ignition, differ by 0.3 mg or less. It quantifies constant weight: the pharmacopoeia requires two weighings to differ by no more than 0.3 mg, with at least 1 h between drying cycles and 30 min between ignition cycles.
2026-10-14Constant Weight TestingWhat Is a Crucible? Material, Heat Resistance, Uses and the Difference from an Evaporating Dish
A crucible is a laboratory vessel for high-temperature ignition and fusion, usually made of porcelain, quartz or corundum. Porcelain resists about 1200 °C, quartz 1100–1300 °C, corundum up to 1700 °C. Tests needing muffle-furnace high-temperature treatment — ash, residue on ignition, loss on ignition — use a crucible to hold the sample.
2026-10-14Constant Weight TestingWhat Is Residue on Ignition? Definition, ChP 0841 Method and Calculation
Residue on Ignition (ROI) is the non-volatile inorganic residue left after a sample is charred and ignited to constant weight at 600–800 °C (typically 700–800 °C). It mainly consists of sulfated ash and metal oxides, and reflects the total inorganic impurities in a drug or sample. It is a routine limit test in pharmacopeias (ChP 0841, USP 733, EP 2.4.14).
2026-10-14Constant Weight TestingWhat Is Calcination Residue? How It Relates to Residue on Ignition
Calcination residue is a colloquial or alternative name for residue on ignition. Both refer to the same test: the non-volatile inorganic residue left after a sample is charred and ignited to constant weight at 600–800 °C. The standard pharmacopeial term is residue on ignition (ChP 0841); calcination emphasizes the high-temperature burning step.
2026-10-14Constant Weight TestingWhat Is Loss on Ignition (LOI)? Definition, Formula and Measurement
Loss on Ignition (LOI) is the percentage of mass a sample loses after being ignited at a specified high temperature (e.g., 550 °C, 950 °C or 1000 °C). The loss mainly comes from bound water, CO2 released by carbonate decomposition, and volatile organics. It is widely used for refractories, ceramics, cement, resin-bonded sand, and solid waste, similar in principle to residue on ignition but different in temperature and purpose.
2026-10-14Constant Weight TestingWhat Is Ash Determination? Total Ash, Methods and Formula
Ash determination is the analytical procedure that measures the inorganic residue (ash) remaining after a sample is incinerated at high temperature. By treatment it is divided into total ash, acid-insoluble ash, water-soluble ash and others; pharmacopeia and food/feed standards usually determine total ash by ashing at 550–600 °C. It is a basic indicator for quality control and adulteration screening.
2026-10-14Constant Weight TestingWhat Is Acid-Insoluble Ash? Definition, Test and Significance
Acid-insoluble ash is the residue of total ash that is not dissolved after treatment with dilute hydrochloric acid (or a specified acid) and is recovered by filtration. It consists mainly of acid-insoluble inorganic impurities such as silica. Pharmacopeias use it to control external inorganic contamination like soil and sand in drugs and herbs.
2026-10-14Constant Weight TestingWhat Is Crude Ash? Definition and Determination in Feed and Food
Crude ash is the inorganic residue remaining after a feed or food sample is directly incinerated at about 550 °C. It is one item in proximate analysis (alongside crude protein, crude fat, etc.) and is approximately equal to total ash. It reflects the total mineral content and is used for nutrition labeling and quality control.
2026-10-14Constant Weight TestingWhat Is Volatile Matter? Definition and Proximate Analysis
Volatile Matter (VM) is the percentage of gaseous or vaporizable products (hydrocarbons, tar, moisture, etc.) released when a sample is heated in the absence of air (e.g., 900 °C plus or minus 10 °C for 7 minutes). It is a core item of proximate analysis of coal and biomass (moisture, ash, volatile matter, fixed carbon) and is the opposite of non-volatile matter.
2026-10-14Constant Weight TestingWhat Is Non-Volatile Matter? Definition, Total Migration and Evaporation Residue
Non-volatile matter (non-volatile residue) is the residue that remains and does not evaporate after a sample is evaporated or subjected to a migration test. It mainly includes salts, polymers and additives. It is the core analyte of total migration and evaporation residue tests for food-contact materials, and is also used in quality checks of purified water and reagents.
2026-10-14Constant Weight TestingWhat Is Non-Volatile Fraction? Relation to Non-Volatile Matter
Non-volatile fraction is an alternative name for non-volatile matter: the part of a sample that does not evaporate and remains after evaporation or high-temperature treatment (residues such as salts, polymers and additives). In food-contact-material and purified-water quality control the two terms usually denote the same measured quantity, reported as non-volatile matter or fraction.
2026-10-14Constant Weight TestingWhat Are Extractables? Extractables Content and Leachables
Extractables (leachables) are substances transferred into a solvent or medium after a sample (herbal material, environmental sample, packaging, etc.) is extracted with solvent or contacted over time. Extractables content is common in herbal medicines (water/ethanol extract), environmental monitoring (leaching toxicity) and packaging safety evaluation. It relates to non-volatile matter but emphasizes the carried out by solvent process.
2026-10-14Constant Weight TestingWhat Is Vacuum Drying? Principle, Equipment and vs Reduced-Pressure Drying
Vacuum drying is a method of heating a material to dry it under reduced (vacuum) pressure. At low pressure the boiling point of water drops, so the material dehydrates quickly at a lower temperature, ideal for heat-sensitive, easily oxidized, or inherently volatile samples. The LabStone DCT-A atmospheric/reduced-pressure constant-weight analyzer is built on this principle for automatic constant weight.
2026-10-14Constant Weight TestingWhat Is Reduced-Pressure Drying? vs Vacuum Drying
Reduced-pressure drying means drying below atmospheric pressure and is essentially the same as vacuum drying; the wording only emphasizes the lowered pressure. It uses low pressure to lower the boiling point and speed dehydration, suited to heat-sensitive and volatile samples. Pharmacopeias refer to this method as dry in a reduced-pressure desiccator to constant weight.
2026-10-14Constant Weight TestingWhat Is Moisture Content? Relation to Water Content
Moisture content is a synonymous expression for water content: both mean the mass percentage of water (H2O only) in a sample, excluding volatile organic solvents such as ethanol. The two terms are used interchangeably in industry and standards; for the fuller method and formula see the water content entry (Karl Fischer, oven method, ChP 0832).
2026-10-12Packaging Mechanics TestingWhat Is ASTM F88? Seal Strength Testing for Flexible Barrier Materials
ASTM F88/F88M is the standard method for measuring the seal strength of flexible barrier packaging: a 25.4 mm wide strip is cut across the seal and peeled at a constant 200–300 mm/min, reporting the peak force and the average force over the central 80% of the peel. This note explains scope, specimen preparation, the A/B/C support techniques, result calculation and heat-seal curve applications.
2026-10-12Constant Weight Testing105°C Oven Method for Moisture: Step-by-Step GB 5009.3 Direct Drying
The 105°C oven (atmospheric drying) method is the reference Method I 'direct drying' of GB 5009.3 'Determination of Moisture in Foods': moisture is driven off at 101.3 kPa and 101–105°C, and the content is calculated from the mass lost on drying. Constant weight is reached when two consecutive weighings differ by no more than 2 mg; it applies to foods with moisture not below 0.5 g/100 g.
2026-10-12Constant Weight TestingWhat Is the Typical Range of Ignition Residue? Interpreting ChP 0841
Ignition residue (residue on ignition) is the pharmacopoeial limit test for non-volatile inorganic impurities in organic drugs. Under Chinese Pharmacopoeia Method 0841, 1.0–2.0 g of sample is ignited at 700–800°C to complete ashing and constant weight. The typical limit is 0.1%–0.2%; common specifications are 0.1%, 0.2%, 0.5% and 1.0%, as set by the individual monograph.
2026-10-12Constant Weight TestingResin Sand Loss on Ignition: Method and Standards (GB/T 2684)
Resin sand loss on ignition (LOI) reflects binder and volatile content and is a key quality indicator for foundry sand reclamation. Under GB/T 2684 'Testing method for foundry sand and mixtures', the sample is ignited in a muffle furnace at 850–1000°C to constant weight; LOI = (mass before − mass after) / mass before × 100%. Reclaimed resin sand is typically controlled at 2.0%–3.5%, and above 4.0% reclamation must be intensified.
2026-10-12Packaging Mechanics TestingWhat Is ASTM D882? Tensile Testing of Thin Plastic Sheeting
ASTM D882 is the standard uniaxial tensile method for plastic films and sheeting up to 1.0 mm thick: 25.4 mm wide strips with a 250 mm gauge length are pulled at a constant crosshead speed until failure, reporting tensile strength, yield strength and strain, elongation at break and modulus of elasticity. This note explains scope, specimen preparation, conditioning, speed selection and MD/TD anisotropy.
2026-10-12Packaging Mechanics TestingWhat Is ASTM D1894? Coefficient of Friction Testing of Plastic Film
ASTM D1894 is the standard test method for static and kinetic coefficients of friction (COF) of plastic film and sheeting: a 200 g sled with a 63.5 mm base is drawn across a horizontal plane at 150±30 mm/min, the static COF taken from the initial peak force and the kinetic COF from the average force over at least 130 mm of steady sliding, both divided by the ~1.96 N normal force. This note covers scope, specimen preparation, procedure, slip-additive effects and the key differences from ISO 8295.
2026-10-10Barrier PerformanceWhat Is EN 1931? Water Vapour Transmission Testing for Flexible Roof Waterproofing Sheets
EN 1931 is the European standard for determining the water vapour transmission properties of flexible roof waterproofing sheets (bitumen, plastic and rubber) using the desiccant cup gravimetric method at 23°C and 75% RH. This note explains its scope, apparatus, test conditions, result parameters (g, µ, sd) and instrument selection.
2026-10-10Constant Weight TestingWhat Is EU 10/2011? Overall Migration (OML) Testing for Food Contact Plastics Explained
EU 10/2011 is the EU regulation on plastic materials and articles intended to come into contact with food. It sets an overall migration limit (OML) of 10 mg/dm², tested with food simulants A–E under defined time-temperature conditions using the EN 1186 gravimetric methods. This note explains the limit system, simulant selection, OM conditions and instrumentation.
2026-10-08Constant Weight TestingWhat Is Constant Weight? What "Weigh to Constant Weight" Really Means
In test reports, "constant weight" is often misread as "dried until no water remains". This plain-language note explains the strict definition, why we look at the difference between two consecutive weighings, common limits (0.3 mg / 0.5 mg), and how manual weighing differs from automated constant-weight systems.
2026-10-08Constant Weight TestingWhy Food-Contact Materials Must Be Tested for Total Migration and Evaporation Residue
Plastics, coatings and rubber used in food contact can release chemicals into food. Total migration measures "how much is released"; evaporation residue measures "what is left behind". This note explains the compliance meaning of both indicators in plain language, and how gravimetric instruments perform the test.
2026-10-08Constant Weight TestingAsh, Ignition Residue and Loss on Ignition: The Difference Between Three "Weigh After Burning" Indicators
Ash, ignition residue and loss on ignition are all obtained by "burn hot, weigh the residue" and are easily confused. This note uses a comparison table to clarify their definitions, applicable standards, temperatures and calculation direction — one looks at "how much ash remains", one at "what won't burn away", and one at "how much burned off".
2026-10-08Barrier PerformanceHow to Choose Among the Three WVTR Methods: Cup, Electrolytic and Infrared
Water vapour transmission rate (WVTR) measures how readily a packaging film lets water vapour through. The cup method, electrolytic method and infrared method are three mainstream approaches with very different principles and best-fit scenarios. This note uses a comparison table to help you choose quickly by material, precision and efficiency.
2026-10-08Barrier PerformanceWhat Is Oxygen Transmission Rate (OTR)? Why Packaging Fears "Leaking"
Oxygen is the invisible driver of food oxidation, drug degradation and electronic corrosion. Oxygen transmission rate (OTR) measures how fast a packaging film lets oxygen through. Using chips, coffee and tablets as examples, this note explains the OTR–shelf-life cause-and-effect relationship and how the coulometric method measures it.
2026-10-08Barrier PerformanceA Beginner's Guide to Packaging Barrier Testing: Starting with Why Chip Bags Are Puffy
Why are chip bags puffy, coffee flushed with nitrogen, and tablets kept dry? They all point to "packaging barrier". Using everyday examples, this guide helps you grasp the three core indicators — WVTR, OTR and GTR — and how they decide a product's shelf life.
2026-08-07Constant Weight TestingLoss on Drying Is Not Water Content: A Compliance Note on Gravimetric Testing
In food-contact material, pharmaceutical packaging and pharma testing, "loss on drying" and "water content" are routinely confused. Drawing on the Chinese Pharmacopoeia and national standards, this note separates their definitions, their methods and the compliance risk of conflating them — and explains where automated constant-weight systems fit in evaporation-residue and moisture control.
2026-08-07Constant Weight TestingWhy Does HJ 51-2024 Total-Salt Testing Require Repeated Weighing?
In gravimetric total-salt determination the time is not spent evaporating the water but reaching constant weight afterwards. This note breaks down the two constant-weight stages HJ 51-2024 requires — empty dish and sample residue — analyses the bottleneck in batch operation, and explains where automated constant-weight systems fit.
2026-08-07Constant Weight TestingWhat Does Constant Weight Mean in HJ 51-2024, and How Is the 0.5 mg Limit Met?
HJ 51-2024 defines constant weight as two consecutive drying-and-weighing results differing by no more than 0.5 mg. This note explains the logic of that definition, examines the weighing errors caused by hygroscopic calcium and magnesium chlorides and by sulfate water of crystallisation, and shows how automation cuts manual error without altering the conditions the standard specifies.
2026-08-07Constant Weight TestingHJ 51-2024 Water Quality Total-Salt Determination: Gravimetric Procedure and Constant-Weight Requirements
HJ 51-2024 replaced HJ/T 51-1999 on 1 July 2025. This note sets out the complete gravimetric chain — filtration, evaporation, hydrogen peroxide treatment, drying, constant weight and calculation — and explains why constant weight of the empty dish cannot be skipped.
2026-08-05Constant Weight TestingCommon Errors in Ash Determination and How to Control Them
Even when the standard procedure is followed exactly, ash results still vary between batches and between operators. This note traces three error sources — incomplete charring, moisture uptake during cooling, and residual-heat interference — and shows how ramped temperature control, controlled-atmosphere cooling and automatic constant-weight judgement move error control from operator-dependent to system-dependent.
2026-08-05Constant Weight TestingConstant-Weight Control in LOI Testing: Data Quality for Solid-Waste Loss on Ignition
Loss on ignition (LOI) is a key indicator of combustion completeness and organic removal efficiency in solid-waste treatment and environmental monitoring. Standards such as HJ 1024 require constant-weight control here as well — but solid-waste samples have high calorific values, widely differing hygroscopicity and demanding temperature uniformity, making constant weight harder to reach than in routine ash determination.
2026-08-05Constant Weight TestingWhy Ash Determination Needs Constant Weight: From the Science to a Rigorous Automated Endpoint
Ash determination standards (the Chinese Pharmacopoeia, GB 5009.4 and others) all require repeated drying, ignition, cooling and weighing until constant weight is reached. This article explains the science behind constant weight — why one weighing is never enough — and how automated constant-weight systems make endpoint judgement more rigorous and traceable.
2026-08-05Constant Weight TestingCommon Errors in Acid-Insoluble Ash Determination: Controlling the Acid Treatment and Weighing Steps
Acid-insoluble ash determination adds an acid-treatment step (usually hydrochloric or sulfuric acid) on top of total ash, so the sources of error are more complex. This article examines the main errors — losses during acid treatment, corrosion by acidic fumes and transfer residue — and how automated instruments avoid them through corrosion-resistant design, programmed heating and enclosed weighing.
2026-07-31Constant Weight TestingNon-Volatile Matter in Pharmaceutical Packaging Extractables: The Key Compliance Steps
Determination of non-volatile matter in pharmaceutical packaging extractables is a mandatory safety screening for packaging that contacts the drug directly. Based on YBB 00342004, this article walks through the key compliance steps — choice of extraction medium, water-bath evaporation, drying at 105 °C to constant weight — and how fully enclosed automated constant weight avoids high blanks and sample spatter.
2026-07-29Barrier PerformanceHow to Improve High-Barrier Gas Transmission Rate Testing Efficiency: Seven Core Levers
Gas transmission testing of EVOH, PVDC and aluminium–plastic composites can take over ten to dozens of hours, becoming a delivery bottleneck. This article breaks down seven levers — vacuum speed, sealing, pressure control, temperature stability, automatic desorption, automatic calibration and automatic data processing — to shorten the test cycle without sacrificing accuracy.
2026-07-29Barrier PerformanceGTR, Permeability, Diffusion and Solubility Coefficients: Meanings and Differences of Four Core Parameters
Why does one film's gas-permeation report show four values at once — gas transmission rate, permeability, diffusion and solubility coefficients? Starting from the three-step dissolution–diffusion–desorption permeation model, this article explains the definitions, units, calculations and use cases of the four parameters, and illustrates the differences with PE, PET, EVOH, PA and PVDC.
2026-07-29Barrier PerformanceWhy Does High-Barrier Gas Transmission Rate Testing Take So Long?
An ordinary film's gas test yields results in hours, yet EVOH takes a full day, PVDC longer, and aluminium–plastic composites are almost unmeasurable. This article explains the underlying reasons — permeation physics, vacuum, desorption and temperature stability — and the key practices for shortening the cycle while keeping accuracy.
2026-07-29Barrier PerformanceDifferential-Pressure vs Equal-Pressure (Coulometric) Gas Transmission Rate Testing: Differences and How to Choose
The differential-pressure and equal-pressure (coulometric) methods are the two mainstream GTR techniques. This article compares them across working principle, suitable materials, precision, speed, measurable gases and pharmacopoeia preference, helping laboratories pick the right method for their industry and get reliable data.