Filter Organic Extractables: NVR vs TOC Test Methods Compared

NVR weighs non-volatile residue; TOC oxidizes and measures total carbon. They catch different things. This article explains both methods, regulatory specs, and the order-of-magnitude differences between PP and UPE.

Article Highlights · Key Points

NVR (Non-Volatile Residue) is measured by "weighing" — evaporate 100 mL of extract dry, and whatever remains on the dish is the result in mg/L
TOC (Total Organic Carbon) is measured by "burning" — oxidize all organics into CO₂ and measure the carbon content; sensitivity reaches the ppb level
The two methods catch different things: NVR catches non-volatile heavy components that TOC can't see; TOC catches small volatile molecules that NVR can't detect
Semiconductor UPW spec: TOC < 1 ppb (target); pharmaceutical WFI spec: TOC < 500 ppb (USP <643>); advanced process filter cartridges: NVR < 1 mg/L
This article delivers a complete test workflow, a comparison across four major materials, and a debunking of common marketing claims

Table of Contents

Why does the semiconductor industry measure NVR and TOC every single day?
NVR: weigh-based — "how much non-volatile residue is left"
TOC: burn-based — measuring carbon content
NVR vs TOC: they catch completely different things (with comparison table)
Detailed test workflow
Measured NVR / TOC performance comparison across four major materials
Spec quick-reference: semiconductor UPW, pharmaceutical WFI, semiconductor photoresist
Common errors and marketing claims
Frequently Asked Questions
References

Why does the semiconductor industry measure NVR and TOC every single day?

Cleaning baths, photoresist coaters, and UPW systems in wafer fabs are wrapped in a "filtration maze" of cartridges in series. These cartridges are themselves polymers, and the question is: do they leach a tiny bit of themselves into the fluid during operation, contaminating downstream wafers? — That's exactly what "extractables" testing is meant to answer.

Extractables fall into two camps: organic leachables (polymer oligomers, plasticizers, residual monomers, cleaning agent residues) and inorganic leachables (metal ions, TDS). This article focuses on the organic side, where the industry's two standard yardsticks are NVR and TOC.

< 1Semiconductor UPW TOC (ppb)

< 500Pharmaceutical WFI TOC (ppb)

< 1Semiconductor cartridge NVR (mg/L)

105NVR evaporation temperature (°C)

The difference between NVR and TOC is often blurred. But in practice, they are two yardsticks with completely different scales: NVR's smallest division is about 0.1 mg/L (100 ppb level), while TOC can measure down to 0.05 ppb — a difference of three orders of magnitude. But TOC misses the "uncombustible" ash, while NVR misses "volatile small molecules." One is heavy, the other is sensitive — each covers the other's blind spot.

NVR: weigh-based — "how much non-volatile residue is left"

NVR (Non-Volatile Residue) is the oldest and most brute-force method — take a fixed volume of extract, evaporate it dry, and weigh the residual solids.

Standard method (ASTM E1235)

Sampling: typically 100 mL of extract (more sample = more sensitive, but takes longer)
Container: platinum or stainless-steel evaporation dish, dried at 105 °C to constant weight beforehand and recorded as W₀
Evaporation: completely evaporate the solvent in a 105 °C oven or vacuum rotary evaporator (~4–6 hours for aqueous samples)
Constant weight: return to 105 °C oven for 30 min, cool in a desiccator, weigh as W₁
Calculation: NVR (mg/L) = (W₁ − W₀) × 10³ ÷ V (sample volume in L)

Why 105 °C? Because this temperature is high enough to fully evaporate water but low enough to retain most organic polymer oligomers, plasticizers, and silicone oils on the dish. Higher temperatures would burn off these heavy components, severely underestimating the result.

What does NVR catch?

Polymer oligomers (low-MW residual oligomers from PE, PP processes)
Plasticizers and antioxidants (DOP, Irganox 1010, and other additives)
Lubricants and mold release agents (silicone oils, PEG-based)
Cartridge cleaning agent residues (surfactants, mid-boiling-point IPA impurities)
Inorganic salts (also weighed in — a limitation of NVR)

What does NVR miss?

Anything with a boiling point below 105 °C — methanol, ethanol, acetone, IPA, dichloromethane, low-MW monomers — all evaporate during drying. So NVR cannot measure "volatile organic compounds (VOCs)". This is exactly where TOC steps in.

TOC: burn-based — measuring carbon content

TOC (Total Organic Carbon) takes the opposite approach — it doesn't matter whether you're volatile or non-volatile, molecule or ion: as long as you contain carbon, I'll burn you into CO₂, measure the CO₂ concentration with infrared (NDIR), and back-calculate the organic carbon content.

Three mainstream oxidation methods

High-temperature combustion

680–950 °C catalytic combustion

Sample is injected into a Pt/Co catalyst high-temperature furnace, and all carbon is oxidized to CO₂; suitable for high-TOC samples (wastewater, colored fluids), with detection limit ~50 ppb.

UV persulfate

UV + sodium persulfate oxidation

185 nm UV + persulfate radicals; designed for ultrapure water applications, with detection limit 0.05 ppb (Sievers M9, 500 RL).

Heated persulfate

Heating + persulfate

100 °C heating + persulfate radicals; sits between the other two, common in pharmaceutical WFI on-line monitoring.

Relationship between TC, IC, and TOC

TOC is not measured directly in one shot, but rather computed by subtraction: TOC = TC − IC:

TC (Total Carbon): all forms of carbon, including organic + inorganic (carbonates, dissolved CO₂)
IC (Inorganic Carbon): the CO₂ portion driven off after acidifying the sample
TOC: what remains after subtracting IC — the organic carbon

Practical tip: UPW systems typically have TOC < 5 ppb, with most IC already removed by reverse osmosis + EDI. So the NPOC (Non-Purgeable Organic Carbon) method can be used — directly purge IC with acid and gas, then measure TOC, avoiding the amplified error of subtracting two large numbers (TC − IC).

What is USP <643>?

USP <643> is the legally required method for TOC in pharmaceutical Water for Injection (WFI) and Purified Water (PW). Key requirements:

TOC limit: 500 ppb (same standard for PW and WFI)
System suitability test: 1.19 ppm sucrose + 0.75 ppm 1,4-benzoquinone as standard solutions, with 85–115% recovery
Both on-line and off-line modes are supported, but continuous monitoring is best practice

NVR vs TOC: they catch completely different things

Item	NVR (Non-Volatile Residue)	TOC (Total Organic Carbon)
Principle	Evaporation + gravimetric	Oxidation to CO₂ + NDIR infrared absorption
Units	mg/L, ppm	ppb, µg C/L
Detection limit	~0.1 mg/L (100 ppb)	0.05 ppb (online instruments)
Detects	Non-volatile organics + inorganic salts	All organic carbon (volatile + non-volatile)
Misses	Volatiles with bp < 105 °C	Carbon-free impurities (metals, silicates)
Standard methods	ASTM E1235, SEMI C72	USP <643>, SEMI C79
Instrument cost	Oven + microbalance (< NT$500K)	Dedicated TOC analyzer (NT$800K–2.5M)
Analysis time	4–8 hours / sample	3–10 min / sample
Main applications	Cartridge cleanliness, solvent purity	UPW, WFI, cleaning validation
Online monitoring	None	Standard practice (24/7 real-time)

One-line summary: NVR is a "scale" — looking at "what's left on the dish"; TOC is a "carbon analyzer" — looking at "total carbon present." For the same cartridge, the two numbers will not be equal — and shouldn't be, because they measure different things.

Detailed test workflow

Whether NVR or TOC, 80% of the cartridge testing essence is in sample preparation, and only 20% in the instrument. For typical semiconductor / pharmaceutical cartridge extractables testing, the standard steps are:

1. Pre-flushing (Flushing / Conditioning)

New cartridges always have an initial peak that won't wash out — manufacturing, packaging, and shipping cannot be perfectly clean. SEMI C72 spec: pre-flush with 18 MΩ·cm UPW for at least 30 min or 10 cartridge volumes. For pharmaceutical applications, follow each plant's SOP — typically IPA → WFI → repeated rinsing until TOC stabilizes.

2. Extract collection

Use a standard cleaning fluid (semiconductor: UPW; pharma: WFI; chemical cartridges: corresponding solvent in use) to collect extract via "static soaking" or "dynamic recirculation":

Static soaking: cartridge submerged in solvent, sampled at fixed time (24–72 hr) + fixed temperature (25–70 °C)
Dynamic recirculation: recirculate at a constant flow rate through the cartridge, taking outlet samples at intervals for analysis

3. Analysis

NVR: 100 mL sample → evaporate at 105 °C → weigh on microbalance
TOC: 5–10 mL sample (typically auto-injected) → oxidation → NDIR → calculate ppb

4. Identification (optional)

When NVR or TOC is abnormally elevated and contamination needs to be traced, further analysis is performed using GC-MS (volatile species) or LC-MS (polar / non-volatile species) to fingerprint specific molecules in the dried residue or concentrated extract. Advanced semiconductor manufacturers also run ICP-MS for metal extractables to build a complete extractables profile.

Easy mistake: if sampling containers are ordinary glass bottles, Na, K, and Si will continuously leach into and contaminate the sample. TOC requires low-TOC glass / PFA bottles (pre-cleaned with UPW and dried) — otherwise the background starts at 50–100 ppb, making it impossible to accurately measure the cartridge itself.

Measured NVR / TOC performance comparison across four major materials

Putting four cartridge materials — PP, Nylon, UPE, PTFE — through identical extractables testing (SEMI C72 conditions, UPW 25 °C dynamic recirculation) yields large differences. Below are typical industry-disclosed ranges:

Material	NVR (mg/L)	TOC (ppb)	Notes
PP (polypropylene)	2.0–8.0	200–1500	Contains antioxidants + oligomers
Nylon-6,6	1.5–5.0	150–800	Caprolactam monomer residue
UPE (ultra-high-molecular-weight PE)	0.05–0.3	5–50	No additives, extremely low leaching
PTFE	0.05–0.2	3–30	Chemically inert, low TOC

TOC extractables across four materials (ppb, after SEMI C72 30 min flush)

~800

Nylon

~400

UPE

~25

PTFE

~15

The table reveals two things:

PP / Nylon are inherently "high background" materials — it's not that the manufacturer has poor quality, but that the materials themselves contain process additives. So PP prefilters are well suited for coarse filtration — cheap and durable — but should never sit in the last filter position of a UPW system.
UPE and PTFE are inherently "low-leaching" materials — their molecular chains are inert, with no antioxidants, plasticizers, or residual monomers. This is why semiconductor advanced-process final filters (point-of-use) are almost exclusively UPE or PTFE.

Spec quick-reference: semiconductor UPW, pharmaceutical WFI, semiconductor photoresist

Application	Key parameter	Limit (target)	Source
Semiconductor UPW (advanced process)	TOC	< 1 ppb	SEMI F63, ITRS
Semiconductor UPW (general process)	TOC	< 5 ppb	ASTM D5127 Type E-1
Pharmaceutical WFI	TOC	< 500 ppb	USP <643>, EP 2.2.44
Pharmaceutical Purified Water (PW)	TOC	< 500 ppb	USP <643>
Semiconductor cartridge (point-of-use)	NVR	< 1 mg/L	SEMI C72, plant-specific spec
Semiconductor cartridge (UPE high-end)	TOC extractables	< 50 ppb (after 30 min flush)	Entegris / Pall specifications
Photoresist / developer cartridges	Metal extractables	< 0.5 ppt (single element)	SEMI C79, fab spec
Injectable filters	Non-volatile extractables	Validation + chemical identification required	USP <1663>, <1664>

Practical tip: the specs look intimidating, but most are system-level targets — UPW system effluent must be < 1 ppb TOC, which doesn't mean each individual cartridge must be < 1 ppb. Cartridge supplier specs are typically "outlet TOC after 30 min flushing under SEMI C72 conditions" — a different thing from the system spec.

Common errors and marketing claims

Claim 1: "Our cartridge has TOC = 0." No polymer cartridge can have zero TOC — even ultra-high-purity UPW itself has 0.5–1 ppb TOC background. When you see this kind of number, first ask "after how many flush volumes" and then "what's the instrument detection limit."

Claim 2: "Lower NVR = better quality." NVR is heavily affected by material type. A PP cartridge at 1 mg/L NVR and a PTFE cartridge at 1 mg/L NVR are two different worlds. The former is excellent for PP; the latter is a serious defect for PTFE. Always check the material before comparing.

Claim 3: "TOC spec < 5 ppb" without flushing conditions. TOC numbers without a conditioning protocol are meaningless. Ask explicitly: 30 min flush, 60 min flush, or 24 hr soak? At what flow rate?

Mistake 4: substituting NVR for TOC in pharmaceutical regulatory reports. USP <643> explicitly mandates TOC — you cannot convert from NVR to fudge it. Pharma audits will fail it on the spot.

Mistake 5: treating system TOC as cartridge TOC. System TOC includes UPW background + piping leaching + cartridge leaching. If TOC rises by 10 ppb after replacing the cartridge, that's a system phenomenon, not necessarily a cartridge defect — a differential analysis is needed.

Frequently Asked Questions

Doing both NVR and TOC — isn't that redundant?

It's not redundant — they're complementary. NVR catches heavy components (plasticizers, oligomers), TOC catches all carbon-containing species (including small volatile molecules). High-end semiconductor cartridge manufacturers typically report both; pharma focuses on TOC, with NVR used as manufacturing QC. If budget forces a choice, look at the target fluid: pure-water applications prioritize TOC; solvent / chemical applications prioritize NVR.

Why does TOC spike high then drop after a new cartridge is installed?

That's called extractables peak. During manufacturing, shipping, and aseptic packaging, the cartridge surface and pores adsorb low-MW species, which are flushed out in the first wave once on-line. So the SOP must specify "flush to TOC stable" — typically 30 min – 2 hr to settle into spec. Advanced fabs do "conditioning recipes" after cartridge replacement, only releasing to production once TOC drops back to baseline.

Which has lower NVR — UPE or PTFE?

Both measure extremely low (< 0.3 mg/L) in practice — the gap is small and easily masked by instrument noise. The real difference is chemical resistance: PTFE maintains low leaching even in strong acids/bases and strong oxidizers; UPE is best in neutral / weakly alkaline conditions and degrades under strong oxidizers (O₃, persulfate). So choose UPE for photoresist and developer, PTFE for HF / SC1.

Are portable TOC analyzers (under NT$1M) sufficient?

It depends on the use case. Pharmaceutical WFI (500 ppb spec): portable models often carry compliance certification, sufficient for routine QC. Semiconductor UPW (< 1 ppb spec): requires UV-persulfate ultra-low TOC online instruments (Sievers 500 RL, M9, Anatel A1000 class) — portable units don't have the detection limit.

Must extractables testing always use UPW as the solvent?

It depends on the actual fluid the cartridge will contact. Principle: use the actual operating fluid for extraction. Photoresist cartridges should be extracted with PGMEA; HF cartridges with diluted HF; pharmaceutical aqueous cartridges with WFI. Using UPW as a "universal test" only reflects leaching behavior under aqueous conditions and cannot represent solvent scenarios.

How do I convert mg/L on an NVR report to g/cm²?

You can't convert directly — you need to know the cartridge area and extraction volume. Area loading (mg/m²) = NVR (mg/L) × extraction volume (L) ÷ effective cartridge area (m²). For a 0.6 m² cartridge with 1 L extract at NVR 0.5 mg/L, that's 0.83 mg/m² area loading. International comparisons typically use area loading or mg/cm³ media volume loading.

References

Unsure how to interpret your extractables test report?

Send your application context (semiconductor / pharmaceutical / chemical), current cartridge model, and extractables spec to JIUNYUAN engineers. We'll help interpret NVR / TOC data, compare material compatibility, and recommend lower-leaching alternatives.

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