Sodium Percarbonate Testing

Sodium percarbonate testing mainly conducts scientific testing and analysis on the active oxygen content, total alkalinity detection, moisture content determination, apparent density and particle size analysis, heavy metal ion content detection such as the iron, copper and manganese, pH value determination and other items, objectively assessing the product quality grade and issuing a detailed test report, providing a basis for the production enterprise quality control and downstream user product acceptance.

Testing items

Active oxygen content (A.O.) determination: The active oxygen content is the core quality indicator of the sodium percarbonate, directly reflecting its effective bleaching and oxidation capabilities. This indicator is expressed by the mass percentages, usually determined through the chemical titration methods, and its results are closely related to the product purities, stabilities and final application effects, and are the key parameters of the production controls and product acceptances.

Total alkalinity detection: The total alkalinity refers to the sum of all the alkaline substances (such as the sodium carbonate and sodium hydroxide, etc.) in the products, usually calculated as the sodium carbonate. The excessively high alkalinities may cause the damages to the certain application materials (such as the fabric fibres), while the appropriate alkalinities help to maintain the product stabilities and synergise its bleaching effects, and the testing usually adopts the acid-base titration methods.

Moisture content determination: The moisture is the key factor affecting the sodium percarbonate stabilities and storage lives. The excessively high moisture will catalyse its decomposition, leading to the active oxygen losses. The testing methods usually adopt the Karl Fischer method or oven drying methods, and the strict control of the moisture contents is the important link for the guarantee of the product performance not decaying during the storage and transportation processes.

Apparent density and particle size analysis: The apparent density affects the product packaging volumes, transportation costs and dissolution speeds in the water. The particle size distributions are related to the product flowabilities, dust controls as well as the mixing uniformities with the other washing components. The testing of these physical indicators is crucial for the industrial productions and application compatibilities.

Heavy metal ion content detection such as the iron, copper and manganese: The trace heavy metal ions (especially the iron, copper and manganese) are the strong catalysts of the sodium percarbonate decompositions, will seriously accelerate the losses of its active oxygen, affecting the product stabilities. Usually adopt the atomic absorption spectrometry or inductively coupled plasma optical emission spectrometry for the trace analyses, to control their contents at the extremely low levels.

pH value determination: Determine the pH values of the sodium percarbonate aqueous solutions, can rapidly evaluate the strengths of its alkalinities, and this has the reference values for the judgement of its compatibilities in the use environments (such as whether the fabrics are damaged and the equipment is corroded). The testing is usually carried out in the aqueous solutions of the specified concentrations.

Testing scope

Industrial-grade sodium percarbonate: Mainly used for the bleaching in the textile printing and dyeing industries, the pulp bleaching in the papermaking industries and the oxidants in the industrial wastewater treatments, etc. The testing focuses on the high active oxygen contents, low impurity contents as well as the physical and chemical indicators meeting the requirements of the specific industrial processes.

Sodium percarbonate for household detergents (daily chemical grade): As the main oxygen-based bleaching components of the laundry powders, laundry pods and colour-safe bleaches, etc. The testing emphases lie in the active oxygen contents, dissolution speeds, compatibility stabilities with the enzyme preparations and surfactants, as well as the safeties to the fabrics (such as the low alkalinities and no damages).

Food-grade sodium percarbonate: As the disinfectants and processing aids of the food industry (such as the cleaning and disinfection of the beer bottles). Its testing requirements are the most stringent, in addition to the routine indicators, need to strictly control the contents of the toxic heavy metals such as the arsenic and lead, and conform to the relevant food additive safety standards.

Sodium percarbonate for the pharmaceutical and hygiene disinfection: Used in the fields such as the medical device and environmental disinfection. The testing needs to follow the relevant pharmaceutical or disinfection product regulations, in addition to the effective component contents, with the strict requirements for the microbial limits, toxicities and residues.

Raw material and intermediate quality control: Carry out the testing of the raw materials for the production of the sodium percarbonate (such as the soda ash and hydrogen peroxide), as well as the monitoring of the intermediate products in the production processes, ensuring the stable final product qualities, controlling the impurity introductions from the sources.

Product stability and storage period evaluation: Through the accelerated ageing experiments (such as the high temperature and high humidity storage), regularly detect the active oxygen decay rates, evaluate the product storage stabilities and predict their shelf lives, providing the basis for the packaging material selections and storage condition settings.

Testing methods

Potassium permanganate titration method (chemical method): The classic method for the determination of the active oxygen contents. In the acidic media, the hydrogen peroxide released by the sodium percarbonate undergoes the redox reactions with the potassium permanganate, through the consumed potassium permanganate standard solution volumes calculate the active oxygen contents. This method has the simple operations and low equipment requirements, and is the common method of the laboratories and factories.

Iodometric method: Another reliable method for the determination of the active oxygen. Under the acidic conditions, the hydrogen peroxide oxidises the potassium iodide into the elemental iodine, then titrate the generated iodine with the sodium thiosulphate standard solutions. The iodometric method has the obvious end point colour changes and high accuracies, especially applicable to the determinations of the coloured or turbid samples.

Karl Fischer method: The international standard method for the determination of the moisture contents, based on the principle of the quantitative reactions of the iodine and sulfur dioxide with the water in the pyridine and methanol solutions. This method has the strong specificities and high precisions, especially applicable to the precise determinations of the trace moisture, and is the key method for the control of the sodium percarbonate product moisture.

Atomic absorption spectrometry/ICP-OES methods: Used for the detection of the trace metal impurities such as the iron, copper and manganese. The atomic absorption spectrometry has the good selectivities and high sensitivities; the inductively coupled plasma optical emission spectrometry can realise the simultaneous rapid analyses of the multiple elements. Both are the precision instrumental analysis methods for the heavy metal controls in the modern laboratories.

Sieve analysis method and laser particle size analysis method: Used for the analyses of the particle size distributions. The sieve analysis method has the simple operations and low costs, applicable to the routine analyses of the relatively large particles; the laser particle size analysers can rapidly and precisely provide the full-range particle size distribution data, including the information such as the median particle sizes (D50) and spans.

pH meter determination method: Use the calibrated pH meters, directly measure the pH values of the sodium percarbonate solutions at the specified concentrations (such as the 1% aqueous solutions). During the operations, need to pay attention to the temperature compensations and the cleaning and maintenance of the electrodes, to ensure the accuracies of the measurement results.

Testing standards

Domestic standards:

1. GB/T 27601-2011, Sodium percarbonate for industrial use

2. GB/T 602, Chemical reagent — Preparations of standard solutions for impurity determination

3. GB/T 603, Chemical reagent — Preparations of reagent solutions for use in test methods

International standards:

1. ISO 3696, Water for analytical laboratory use — Specification and test methods

Note: The applicable standard can be selected according to the product use and customer trade requirements; standards agreed in the contract take precedence over general standards.

Testing Instruments and Equipment

Analytical balances: The basic equipment of all the quantitative chemical analyses, used for the precise weighing of the samples and reference substances. When testing the sodium percarbonate, need to use the analytical balances with the precisions of at least 0.0001 g, to ensure the accuracies of the results such as the titration calculations.

Burettes and automatic potentiometric titrators: The burettes are the basic tools for the manual titrations such as the potassium permanganate method and iodometric method. The automatic potentiometric titrators judge the end points through the potential changes, avoiding the human subjective errors, improving the precisions, efficiencies and automation degrees of the titration analyses.

Karl Fischer moisture analysers: The precision instruments specially used for the moisture determinations, divided into the volumetric method and coulometric method. The volumetric method is applicable to the samples with the relatively high moisture contents, while the coulometric method has the extremely high sensitivities, applicable to the determinations of the trace moisture (ppm level).

Atomic absorption spectrometers and ICP-OES spectrometers: The precision spectroscopic instruments for the analyses of the heavy metal elements. The AAS structures are relatively simple with the lower operation costs; the ICP-OES has the wider linear ranges and lower detection limits, and can carry out the simultaneous analyses of the multiple elements with the higher efficiencies.

Laser particle size analysers: The modern instruments for the measurement of the particle size distributions based on the light scattering principles. They can rapidly and non-destructively provide the detailed particle size distribution reports, and are the important equipment for the evaluation of the sodium percarbonate product physical performance such as the flowabilities and solubilities.

Precision pH meters and conductivity meters: The pH meters are used for the measurement of the solution acidities and alkalinities, and the conductivity meters can be used for the indirect evaluation of the overall levels of the soluble ionic impurities in the samples. Both need to be regularly calibrated with the standard buffer solutions and standard solutions, ensuring the reliable data.

Constant temperature drying ovens and stability test chambers: The constant temperature drying ovens are used for the determination of the items such as the moisture and ignition losses. The stability test chambers (such as the constant temperature and humidity chambers) can simulate the different temperature and humidity environments, used for the product accelerated ageing experiments and storage stability research.