BIS Certification for Phthalic Anhydride (Technical) – IS 5158:2025 | Complete Guide for Manufacturers and Importers

BIS Certification for Phthalic Anhydride (Technical) – IS 5158:2025 | Complete Guide for Manufacturers and Importers

SEO Title: BIS Certification for Phthalic Anhydride – IS 5158:2025
Meta Title: IS 5158 BIS Certification | Phthalic Anhydride Technical
Meta Description: Complete guide to BIS certification for Phthalic Anhydride (Technical), covering IS 5158:2025, QCO requirements, testing parameters, GC analysis, documents, sample requirements and the BIS licensing process.
URL Slug: bis-certification-phthalic-anhydride-is-5158

Primary Keyword: BIS Certification for Phthalic Anhydride
Secondary Keywords: IS 5158:2025, IS 5158:1987, Phthalic Anhydride BIS Licence, BIS Certification for Chemicals, Phthalic Anhydride QCO, ISI Mark for Phthalic Anhydride, BIS Scheme-I Certification, Phthalic Anhydride Testing

Introduction

Phthalic Anhydride is an important industrial chemical used as a raw material in the manufacturing of plasticisers, unsaturated polyester resins, alkyd resins, coatings, paints and other chemical products. Its purity and impurity profile can directly influence the quality and performance of downstream products.

To regulate the quality of Phthalic Anhydride supplied in the Indian market, the Government of India introduced the Phthalic Anhydride (Quality Control) Order, 2020, requiring the product to conform to the applicable Indian Standard and bear the BIS Standard Mark under a valid licence.

The original specification was IS 5158:1987 – Specification for Phthalic Anhydride, Technical. However, an important revision has taken place: BIS revised the standard to IS 5158:2025 – Phthalic Anhydride, Technical – Specification.

According to BIS implementation guidelines dated 14 November 2025, the revised standard was required to be implemented by 24 January 2026, after which the 1987 edition was to be withdrawn.

Therefore, manufacturers and importers planning BIS certification in 2026 must understand both the original QCO reference and the revised standard applicable to current certification.

This guide explains the regulatory requirements, technical testing parameters, major changes in the revised standard, sample requirements, documentation and BIS certification process.

1. What Is IS 5158?

IS 5158 is the Indian Standard covering the specification for Phthalic Anhydride, Technical, intended for industrial applications.

The standard establishes quality requirements and test methods for evaluating the product’s physical and chemical characteristics.

Particular	Details
Product	Phthalic Anhydride, Technical
Original standard	IS 5158:1987
Revised standard	IS 5158:2025
Current edition	Third Revision
Certification scheme	Scheme-I – ISI Mark Scheme
Quality Control Order	Phthalic Anhydride (Quality Control) Order, 2020
Product category	Industrial chemical
HS Code listed in the Department’s QCO information	29173500

Important: The original QCO notification refers to IS 5158:1987. However, the QCO framework provides for the applicable standard as published and notified by BIS from time to time. BIS subsequently issued implementation instructions for IS 5158:2025. New certification and compliance planning should therefore be based on the revised edition.

2. What Is Phthalic Anhydride (Technical)?

Phthalic Anhydride is an organic chemical compound commonly used as an intermediate in the chemical and polymer industries.

It is commercially produced using suitable manufacturing routes, including oxidation processes involving:

• O-Xylene
• Naphthalene

The BIS Product Manual for the earlier edition identifies O-Xylene and Naphthalene as product sources.

Major Industrial Applications

Phthalic Anhydride is used in manufacturing:

1. Plasticisers for PVC applications.
2. Unsaturated polyester resins.
3. Alkyd resins.
4. Paints and coatings.
5. Synthetic resins.
6. Industrial chemicals and intermediates.
7. Other chemical formulations.

The quality of Phthalic Anhydride is important because impurities may affect product colour, processing performance, chemical reactions and the properties of downstream materials.

3. Is BIS Certification Mandatory for Phthalic Anhydride?

<badge color=”success”>Mandatory under QCO</badge>

Yes. Phthalic Anhydride is covered under the Phthalic Anhydride (Quality Control) Order, 2020, notified by the Department of Chemicals and Petrochemicals through S.O. 1402(E), dated 23 April 2020.

The QCO requires the specified product to:

• Conform to the applicable Indian Standard.
• Bear the BIS Standard Mark.
• Be manufactured or supplied under a valid BIS licence under Scheme-I of the BIS Conformity Assessment Regulations, 2018.

The original notification specifically identifies IS 5158:1987 for Phthalic Anhydride, Technical.

The QCO also provides an exception for goods or articles meant for export.

Important Regulatory Details

Particular	Details
QCO	Phthalic Anhydride (Quality Control) Order, 2020
Notification number	S.O. 1402(E)
Notification date	23 April 2020
Applicable Indian Standard	IS 5158, as revised and notified by BIS
Certification scheme	Scheme-I
Certification authority	Bureau of Indian Standards
HS Code listed	29173500
Export exception	Goods or articles meant for export are excluded under the original QCO

The Department of Chemicals and Petrochemicals also lists subsequent amendments to the Phthalic Anhydride QCO, including the amendments issued in 2022.

Manufacturers and importers should verify the applicable QCO amendments and any relevant exemptions before undertaking commercial supplies.

4. Important Update: IS 5158:1987 Revised to IS 5158:2025

One of the most important considerations for applicants is the revision of IS 5158.

BIS issued an implementation circular on 14 November 2025, bearing reference CMD-2/16:5158.

The circular confirms:

• IS 5158:1987 has been revised as IS 5158:2025.
• The last date for implementation of the revised standard was 24 January 2026.
• The old edition was to stand withdrawn after that date.
• No licence could be granted under the old edition beyond 24 January 2026.
• Existing licensees were required to implement the revised standard and provide evidence of conformity.

Major Changes Introduced in IS 5158:2025

The revised edition introduces important changes in the testing methodology and impurity requirements.

Parameter	Earlier edition – IS 5158:1987	Revised edition – IS 5158:2025
Purity determination	Titrimetric method	Gas Chromatography (GC) method
Maleic anhydride and other oxidisable impurities	Titrimetric method	GC method incorporated
Naphthaquinone	Maximum 5 ppm	Maximum 1 ppm
Naphthalene	Maximum 20 ppm	Maximum 1 ppm
Phthalimide	No corresponding new requirement identified in the BIS implementation circular	New requirement incorporated
Marking	Earlier marking requirements	Month and year of manufacture incorporated

The revised standard also introduces GC-based determination for purity and specified impurities, including maleic anhydride and other oxidisable impurities, naphthaquinone, naphthalene and phthalimide.

Why is this revision important?

Manufacturers relying on the previous titrimetric methods may need to upgrade their laboratory arrangements and testing procedures to demonstrate conformity with the revised requirements.

The revised impurity limits also require closer control over manufacturing conditions, purification and product quality.

5. Technical Requirements and Testing Parameters Under IS 5158:2025

The revised standard contains requirements for evaluating the quality of Phthalic Anhydride, Technical.

The BIS LIMS entry for IS 5158:2025 identifies the following testing parameters.

Sl. No.	Testing parameter
1	Description
2	Crystallization point
3	Colour of molten material
4	Colour of molten material after heat treatment
5	Free acidity
6	Purity by Gas Chromatography
7	Maleic anhydride and other oxidisable impurities
8	Ash
9	Iron content
10	Naphthaquinone
11	Naphthalene
12	Phthalimide

5.1 Description

The material is examined to verify that its physical appearance and characteristics conform to the product description specified in the standard.

5.2 Crystallization Point

The crystallization point is an important quality parameter for Phthalic Anhydride.

It helps assess the purity and consistency of the product and is evaluated using the method prescribed in the standard.

5.3 Colour of Molten Material

Colour evaluation is carried out to assess the appearance and quality of the molten material.

The revised BIS LIMS listing identifies the colour parameter using the Pt-Co scale.

5.4 Colour After Heat Treatment

The colour of the material after heat treatment is another important parameter for evaluating the quality and thermal behaviour of the product.

5.5 Free Acidity

Free acidity is determined and reported as phthalic acid, represented by the chemical formula C6H4(COOH)2.

This parameter helps evaluate the presence of free acid in the material.

5.6 Purity by Gas Chromatography

The revised IS 5158:2025 incorporates Gas Chromatography for purity determination.

This is an important change from the titrimetric approach prescribed in the earlier edition.

GC analysis also supports the determination of specified impurities in the product.

5.7 Maleic Anhydride and Other Oxidisable Impurities

The revised standard incorporates GC-based determination of maleic anhydride and other oxidisable impurities.

These impurities are relevant to product quality and downstream chemical applications.

5.8 Ash Content

Ash determination helps evaluate the inorganic residue remaining after the prescribed test procedure.

5.9 Iron Content

Iron is an important impurity parameter in Phthalic Anhydride. The product must meet the applicable iron-content requirement.

5.10 Naphthaquinone

The revised standard has tightened the specified requirement for naphthaquinone from 5 ppm to 1 ppm.

5.11 Naphthalene

The revised standard has tightened the specified requirement for naphthalene from 20 ppm to 1 ppm.

5.12 Phthalimide

The revised edition introduces a specific requirement for phthalimide.

Manufacturers should ensure that this parameter is included in their quality control and testing arrangements.

Note: The exact acceptance limits, test methods and reporting requirements must be checked against the complete text of IS 5158:2025. The above section summarises the parameters and changes identified in BIS implementation and laboratory records.

6. Laboratory Testing Requirements for BIS Certification

Testing is a critical part of the BIS certification process.

Manufacturers must demonstrate that their product complies with the requirements of the applicable standard through testing at an appropriate BIS-recognised laboratory.

Testing Facility Requirements

For the revised IS 5158:2025, the laboratory arrangement should be capable of covering the applicable testing parameters, including:

• Crystallization point testing.
• Colour determination.
• Free acidity.
• Gas Chromatography analysis.
• Maleic anhydride and other oxidisable impurities.
• Ash determination.
• Iron content.
• Naphthaquinone.
• Naphthalene.
• Phthalimide.

Importance of Gas Chromatography

Since the revised standard incorporates GC for purity and specified impurity determination, manufacturers should evaluate whether their existing laboratory has suitable GC equipment and validated analytical procedures.

The laboratory should also have:

• Suitable analytical instruments.
• Appropriate reference materials and reagents.
• Trained technical personnel.
• Calibration and maintenance records.
• Documented testing procedures.
• Suitable environmental and safety arrangements.

The exact equipment specifications and test methods must be followed as prescribed in the current standard.

7. Sample Requirements for BIS Certification

The BIS Product Manual PM/IS 5158/1, May 2019, for IS 5158:1987 specified the following sampling information:

Particular	Requirement in the earlier product manual
Product	Phthalic Anhydride, Technical
Sample quantity	25 kg
Raw material requirement	No specific requirement identified
Product grouping	Not applicable (NA)

However, this is the 2019 product manual for the withdrawn 1987 edition.

Manufacturers should not automatically rely on the old 25 kg sample requirement for certification under IS 5158:2025. The current sample quantity and preparation instructions should be confirmed with BIS and the applicable revised product manual or certification instructions before dispatching samples.

Sample Preparation Considerations

Before arranging sample dispatch, manufacturers should confirm:

1. The current sample quantity.
2. The prescribed sampling method.
3. Sample container and packaging requirements.
4. Sample identification and batch details.
5. Required test parameters.
6. Laboratory acceptance and handling requirements.

Correct sample preparation helps avoid testing delays and unnecessary repeat sampling.

8. BIS Product Manual and Inspection Requirements

The earlier BIS Product Manual, PM/IS 5158/1, May 2019, provides guidance for certification under Scheme-I of the BIS Conformity Assessment Regulations, 2018.

It includes:

• Product sampling guidelines.
• Sample size.
• List of test equipment.
• Scheme of Inspection and Testing.
• Product scope of licence.
• Manufacturing and inspection controls.

The earlier manual identifies O-Xylene and Naphthalene as product sources.

It also requires the manufacturer to maintain a suitably equipped and staffed laboratory and prepare a calibration plan for testing equipment.

However, because the product standard has been revised, the old product manual should be used only as historical reference. Applicants must follow the revised BIS product manual and implementation instructions applicable to IS 5158:2025.

9. Documents Required for BIS Certification of Phthalic Anhydride

Manufacturers should prepare the following documents before applying for BIS certification.

A. Company Documents

• Certificate of Incorporation, where applicable.
• PAN Card of the company.
• GST Registration Certificate.
• Details of directors or partners.
• Authorisation letter for the authorised signatory.
• Factory address proof.
• Registered office address proof.

B. Manufacturing Facility Documents

• Factory layout plan.
• Manufacturing process flow chart.
• List of manufacturing machinery.
• Details of reactors and process equipment, as applicable.
• Raw material details.
• Product manufacturing process.
• Storage and handling arrangements.
• Details of packaging and dispatch facilities.

C. Laboratory Documents

• List of testing equipment.
• Details of Gas Chromatography equipment.
• Equipment calibration certificates.
• Equipment maintenance records.
• Laboratory layout, where applicable.
• Testing procedures.
• Details of laboratory personnel.
• Internal test reports.
• Quality control records.

D. Product and Quality Documents

• Product specification.
• Technical Data Sheet (TDS).
• Safety Data Sheet (SDS).
• Raw material specifications.
• Batch-wise test reports.
• Product identification and traceability records.
• Quality control procedures.
• Non-conforming product control procedure.
• Customer complaint and corrective action records.
• Proposed licence scope.

E. Other Documents

• Factory ownership or rent documents.
• Electricity bill or other premises proof.
• Details of installed manufacturing capacity.
• Details of technical personnel.
• Applicable statutory approvals.
• Other documents requested by BIS.

The final checklist should be confirmed against the current BIS application requirements and revised product manual.

10. Step-by-Step BIS Certification Process for Phthalic Anhydride

BIS certification for Phthalic Anhydride is processed under Scheme-I of the BIS Conformity Assessment Regulations, 2018.

The general certification process is explained below.

Step 1: Applicability Assessment

The first step is to establish whether the product falls within the scope of the Phthalic Anhydride QCO.

The applicable standard, current QCO provisions and relevant product description should be reviewed.

Step 2: Manufacturing Facility Assessment

The manufacturer’s manufacturing process, production capacity, raw materials, laboratory infrastructure and quality control arrangements are reviewed.

Step 3: Preparation of Documents

The required business, manufacturing, laboratory and product-related documents are prepared.

The proposed product scope and applicable testing requirements should be clearly identified.

Step 4: Application Submission

The manufacturer submits the BIS application through the applicable online application process and pays the prescribed government fees.

Step 5: Factory Inspection

BIS may conduct a factory inspection to assess:

• Manufacturing infrastructure.
• Quality control arrangements.
• Laboratory facilities.
• Calibration records.
• Production and batch records.
• Implementation of the applicable standard.

Step 6: Sample Drawal and Testing

Samples are drawn and tested according to the applicable requirements of IS 5158:2025.

The testing should cover the relevant characteristics specified in the revised standard.

Step 7: Compliance Review

BIS reviews the inspection findings, test reports and other applicable documentation.

Any identified deficiencies or non-conformities must be addressed.

Step 8: Grant of BIS Licence

After satisfactory completion of the applicable assessment, BIS may grant the licence to use the Standard Mark within the approved scope.

Step 9: Marking and Ongoing Compliance

After obtaining the licence, the manufacturer must comply with the marking requirements, maintain quality control records and follow applicable BIS surveillance and renewal requirements.

11. BIS Marking Requirements for Phthalic Anhydride

Products covered under the applicable QCO must bear the BIS Standard Mark under a valid licence.

The marking provisions must be followed as prescribed in the current standard and BIS licence.

An important change introduced by IS 5158:2025 is the incorporation of the month and year of manufacture in the marking clause.

Manufacturers should therefore update their packaging, product identification and marking procedures to comply with the revised requirements.

The exact marking format and licence details should be confirmed from the current standard and applicable BIS licence conditions.

12. BIS Testing Charges and Certification Cost

The total cost of BIS certification depends on the manufacturing facility, testing requirements, application category and other applicable certification expenses.

Laboratory Testing Cost

The BIS Laboratory Information Management System (LIMS) currently displays a testing charge of ₹14,000 excluding applicable taxes for IS 5158:2025 at the listed laboratory.

The displayed breakup includes the testing parameters under the revised standard, such as:

Testing parameter	Listed charge (₹)
Description – first entry	500
Description – second entry	500
Crystallization point	1,500
Colour of molten material	1,000
Colour after heat treatment	1,000
Free acidity	1,000
Purity by GC	2,500
Maleic anhydride and other oxidisable impurities	1,000
Ash	1,000
Iron	1,000
Naphthaquinone	1,000
Naphthalene	1,000
Phthalimide	1,000
Total displayed testing charge	₹14,000

<text color=”secondary” size=”xs”>This is a laboratory-specific LIMS listing, not a universal BIS testing tariff or a complete certification quotation. Charges, taxes, availability and laboratory scope should be reconfirmed before sample submission.</text>

Other Certification Expenses

The overall project cost may also include:

• BIS application fee.
• Factory inspection charges.
• Licence fee.
• Minimum marking fee and applicable marking charges.
• Sample preparation and transportation.
• Additional testing, if required.
• Laboratory equipment and calibration expenses.
• Consultancy and documentation charges, where applicable.

A complete project quotation should be prepared after reviewing the proposed manufacturing facility and certification scope.

13. Common Challenges in BIS Certification for Phthalic Anhydride

Manufacturers may face several technical and procedural challenges during the certification process.

1. Transition From IS 5158:1987 to IS 5158:2025

The revised standard requires manufacturers to update their testing and quality control arrangements.

Continuing to rely on the withdrawn edition can result in non-compliance.

2. Gas Chromatography Facility

The revised standard incorporates GC-based purity and impurity determination.

Manufacturers need to ensure that the required analytical testing is available through an appropriate laboratory.

3. Tighter Impurity Limits

The revised limits for naphthaquinone and naphthalene require tighter process control and monitoring.

4. New Phthalimide Requirement

The addition of phthalimide as a specified impurity requires manufacturers to incorporate this parameter into their quality control programme.

5. Sample Preparation

Incorrect sample preparation or insufficient quantity can lead to delays in testing.

6. Incomplete Documentation

Missing manufacturing details, calibration records or batch-wise quality documents may result in queries during inspection.

7. Laboratory Selection

Before dispatching samples, manufacturers should verify that the selected laboratory can perform the complete applicable testing scope.

14. How Qualitance India Can Help With BIS Certification

Qualitance India provides BIS certification consultancy and regulatory compliance support to chemical manufacturers and industrial businesses.

For Phthalic Anhydride certification under IS 5158:2025, our support can include:

• Product applicability assessment under the QCO.
• Review of IS 5158:2025 requirements.
• Assessment of the manufacturing process.
• Identification of testing and laboratory requirements.
• Review of Gas Chromatography testing arrangements.
• Preparation of BIS application documentation.
• Review of laboratory equipment and calibration records.
• Guidance on sample preparation and testing.
• Laboratory coordination support.
• Factory inspection preparation.
• Assistance in addressing non-conformities.
• Guidance on marking and post-licence compliance.

Our objective is to help manufacturers understand the revised technical requirements and prepare their facilities and documentation for BIS certification.

Qualitance India – Improving Quality & Competence

For professional assistance with BIS certification for Phthalic Anhydride, contact us:

Website: https://qualitanceindia.com
Email: info@qualitanceindia.com
Phone / WhatsApp: +91 93106 15170

Frequently Asked Questions (FAQs)

Q1. What is the Indian Standard for Phthalic Anhydride?

The original Indian Standard was IS 5158:1987. It was revised to IS 5158:2025, the Third Revision, which is the current edition following BIS implementation of the revised standard.

Q2. Is BIS certification mandatory for Phthalic Anhydride in India?

Yes. Phthalic Anhydride is covered under the Phthalic Anhydride (Quality Control) Order, 2020. The specified product must conform to the applicable Indian Standard and bear the BIS Standard Mark under a valid licence.

Q3. What is the latest standard for Phthalic Anhydride?

The latest edition is IS 5158:2025 – Phthalic Anhydride, Technical – Specification. BIS prescribed implementation by 24 January 2026, after which IS 5158:1987 was to be withdrawn.

Q4. What are the major changes in IS 5158:2025?

Major changes include the introduction of GC methods for purity and specified impurity determination, reduction of the naphthaquinone limit from 5 ppm to 1 ppm, reduction of the naphthalene limit from 20 ppm to 1 ppm, introduction of a phthalimide requirement and changes to product marking.

Q5. Is Gas Chromatography required under IS 5158:2025?

Yes. The revised standard incorporates Gas Chromatography for determining purity and specified impurities, including maleic anhydride and other oxidisable impurities, naphthaquinone, naphthalene and phthalimide.

Q6. What is the sample quantity required for BIS certification?

The earlier BIS Product Manual for IS 5158:1987 specified a sample size of 25 kg. Applicants seeking certification under IS 5158:2025 should confirm the current sample quantity and sampling procedure with BIS before dispatch.

Q7. What tests are required under IS 5158:2025?

The revised standard includes description, crystallization point, colour, free acidity, purity by GC, maleic anhydride and other oxidisable impurities, ash, iron, naphthaquinone, naphthalene and phthalimide.

Q8. What is the BIS testing charge for Phthalic Anhydride?

A BIS LIMS listing displays ₹14,000 excluding taxes for testing under IS 5158:2025 at the listed laboratory. This is laboratory-specific and should not be treated as a universal certification cost.

Q9. Can an existing BIS licensee under IS 5158:1987 continue using the old standard?

No. BIS implementation guidelines required existing licensees to implement the revised standard by 24 January 2026. BIS also instructed that licences should not remain in operation under the old standard after that date.

Q10. Is Phthalic Anhydride meant for export covered under the QCO?

The original Phthalic Anhydride QCO, 2020, excludes goods or articles meant for export. Exporters should verify the applicable notification conditions and documentary requirements for their specific transaction.

Q11. What is the HS Code for Phthalic Anhydride?

The Department of Chemicals and Petrochemicals lists HS Code 29173500 for Phthalic Anhydride in its QCO information. Importers and exporters should independently verify the correct tariff classification for their product.

Q12. Can Qualitance India assist with BIS certification for Phthalic Anhydride?

Yes. Qualitance India can assist with product applicability, revised standard review, documentation, laboratory coordination, sample planning, factory inspection preparation and certification-related compliance support.

Conclusion

BIS certification for Phthalic Anhydride is an important regulatory requirement for businesses manufacturing or supplying the product in the Indian market.

Although the original QCO referred to IS 5158:1987, the standard has now been revised to IS 5158:2025. Manufacturers must therefore ensure that their production, testing and quality control arrangements comply with the revised requirements.

The introduction of Gas Chromatography, tighter impurity limits, the new phthalimide requirement and updated marking provisions make the revision particularly important for chemical manufacturers.

A proper review of the revised standard, laboratory capability, manufacturing controls and BIS documentation can help businesses prepare for certification and maintain re

Free PDF Download

BIS Certification Readiness Checklist 2026

• Documents, testing & factory requirements in one place
• Covers ISI Mark, CRS, FMCS & Hallmarking
• Tick-box format — share it with your team