A Complete Insight into Filter In Biochemistry Analyzer: Technical Specifications, Grades, and Applications

Types of Filters in Biochemistry Analyzers

A biochemistry analyzer is a critical instrument in clinical diagnostics and research laboratories, used to measure the concentration of various biomarkers, enzymes, electrolytes, and metabolites in biological samples such as blood, serum, and urine. Central to its operation is the optical system, which relies on specialized filters to isolate specific wavelengths of light for accurate photometric analysis.

These filters play a pivotal role in ensuring measurement precision by eliminating unwanted light interference and enhancing signal-to-noise ratios. By selectively transmitting or blocking certain wavelengths, filters enable the detection of color changes in reagent-sample reactions—key to quantifying substances like glucose, cholesterol, and bilirubin. The performance, sensitivity, and reliability of a biochemical analyzer are heavily dependent on the quality and type of optical filters used.

Bandpass Filters

Designed to transmit a narrow, specific range of wavelengths while blocking those above and below the target band.

Primary Function: Isolate precise wavelengths for absorbance measurements in colorimetric and enzymatic assays.

Advantages

• High spectral selectivity for accurate readings
• Minimizes interference from adjacent wavelengths
• Essential for multi-analyte testing panels
• Improves data consistency across repeated tests

Limitations

• Narrow bandwidth may reduce light intensity
• Sensitive to angle of incidence
• Higher cost for precision-grade filters

Best for: Routine clinical chemistry, enzyme kinetics, immunoassays

Interference Filters

Utilize thin-film coatings on glass substrates to reflect unwanted wavelengths and transmit only the desired spectrum via constructive and destructive interference.

Primary Function: Achieve extremely narrow wavelength transmission with high out-of-band rejection.

Advantages

• Exceptional wavelength accuracy and stability
• Very high transmission efficiency within passband
• Long operational lifespan with minimal degradation
• Ideal for high-precision diagnostic platforms

Limitations

• Performance can shift with temperature changes
• More expensive than absorption-based filters
• Requires precise alignment in optical path

Best for: High-end analyzers, research applications, quantitative spectrophotometry

Optical Filters (Absorption & Dichroic)

Broad category including both absorption-type filters (which use dyed glass or gelatin to block light) and dichroic filters (which reflect unwanted wavelengths).

Primary Function: Reduce stray light and improve contrast by eliminating non-analytical wavelengths.

Advantages

• Versatile application across different analyzer designs
• Absorption filters are cost-effective and stable
• Dichroic variants offer excellent heat resistance
• Effective in multi-wavelength detection systems

Limitations

• Absorption filters may degrade under prolonged UV exposure
• Less precise than interference filters
• Glass-based versions can be fragile

Best for: Entry-level to mid-range analyzers, general lab use, fluorescence detection

Low-Pass Filters

Allow transmission of shorter wavelengths while blocking longer (higher) wavelengths, effectively cutting off infrared or red light interference.

Primary Function: Eliminate long-wavelength noise, such as scattered light or thermal radiation, that could distort readings.

Advantages

• Prevents spectral overlap in multi-filter systems
• Reduces background interference in colorimetric assays
• Protects detectors from IR-induced heating
• Improves signal clarity in turbid samples

Limitations

• Limited use in isolation—typically supplementary
• May require additional filtering layers
• Not suitable for assays requiring long wavelengths

Best for: Assays sensitive to scattered light, hemolyzed or lipemic samples, UV-visible spectroscopy prep

Filter Type	Wavelength Control	Precision Level	Common Applications	Durability
Bandpass	Narrow, defined range	High	Colorimetry, enzyme assays	Very Good
Interference	Ultra-narrow, sharp cutoff	Very High	Precision diagnostics, research	Excellent
Optical (Absorption/Dichroic)	Moderate to broad filtering	Moderate	General lab testing, fluorescence	Good
Low-Pass	Blocks long wavelengths	Specialized	Noise reduction, sample prep	Good

Expert Tip: For optimal performance, regularly inspect and clean optical filters using lint-free wipes and reagent-grade solvents. Dust, moisture, or coating damage can significantly affect absorbance readings and lead to inaccurate patient results.

Application Insight: Modern automated biochemistry analyzers often use filter wheels containing 6–10 different filters, enabling simultaneous testing of multiple parameters. Selecting the right combination of bandpass and interference filters ensures maximum accuracy across diverse assays—from liver function tests to cardiac markers.

Material & Durability of Filters in Biochemistry Analyzers

The performance, reliability, and longevity of optical filters in biochemistry analyzers are directly influenced by their material composition and structural durability. These filters play a critical role in ensuring accurate detection and quantification of biochemical reactions by selectively transmitting or blocking specific wavelengths of light. Choosing the right filter material is essential to maintain precision across varying experimental conditions, including exposure to harsh chemicals, intense light sources, and fluctuating temperatures.

Key Filter Materials and Their Properties

Glass

Optical Clarity and Chemical Resistance: Glass is the most widely used substrate for optical filters due to its exceptional transparency across both visible and ultraviolet (UV) spectra. This makes it ideal for applications requiring high spectral accuracy, such as fluorescence detection and absorbance measurements.

Borosilicate Glass: A specialized form of glass, borosilicate is highly resistant to thermal shock and chemical corrosion, making it particularly suitable for environments exposed to acids, bases, and organic solvents commonly found in biochemical assays. Its low coefficient of thermal expansion ensures dimensional stability under temperature fluctuations.

Limitations: While glass offers superior optical performance, it is more brittle than alternative materials. Care must be taken during handling and installation to avoid chipping or cracking, especially in high-vibration environments.

Polymer Materials

Lightweight and Flexible Design: Polymers such as acrylic (PMMA) and polycarbonate are increasingly used in filter manufacturing due to their low density and mechanical flexibility. These properties help reduce the overall weight of the analyzer, which is beneficial in portable or handheld devices.

Cost-Effective Production: Polymer filters can be mass-produced using injection molding, offering a cost-effective solution for disposable or single-use diagnostic platforms.

Durability Concerns: However, polymer-based filters are less durable than glass. They are prone to scratching and may degrade under prolonged exposure to UV radiation—a phenomenon known as photodegradation. Additionally, some solvents can cause clouding or swelling, compromising optical integrity over time. As such, they are typically reserved for low-intensity or short-term applications rather than routine clinical use.

Coated Filters

Enhanced Optical Performance: Many glass filters are enhanced with thin-film coatings to improve functionality. Anti-reflective (AR) coatings minimize light loss due to surface reflection, increasing transmission efficiency and signal-to-noise ratio—critical for sensitive detection systems.

Bandpass and Dichroic Coatings: Advanced deposition techniques allow the creation of interference filters that precisely control which wavelengths pass through. These are essential in multi-channel analyzers where specificity is paramount.

Biopolymer Functionalization: In cutting-edge applications, filters may be coated with biorecognition layers (e.g., antibodies or enzymes) to create active sensing surfaces. This integration enhances assay resolution by enabling on-filter biomolecular interactions, reducing cross-contamination and improving reaction kinetics.

Longevity Boost: Properly coated filters exhibit improved resistance to environmental stressors and are better suited for continuous operation in clinical laboratories.

Nickel and Metal Alloys

Mechanical and Thermal Resilience: Nickel and other metal alloys (e.g., stainless steel or Invar) are employed in structural components of filter assemblies, particularly in ruggedized or industrial-grade analyzers. These materials offer exceptional strength, dimensional stability, and resistance to mechanical stress.

High-Temperature Applications: Metal filters or housings are ideal for instruments utilizing intense light sources (e.g., xenon lamps or lasers) that generate significant heat. Their high thermal conductivity and stability prevent warping or misalignment under prolonged operation.

Photochemical Stability: Unlike polymers, metals do not degrade under high-irradiance conditions, making them reliable for long-term use in high-throughput systems. While not typically used as optical transmission media, metal components provide critical support and shielding for delicate filter elements.

Material	Optical Performance	Chemical Resistance	Durability	Typical Use Case
Optical Glass (e.g., Borosilicate)	Excellent (UV-Vis)	High	Medium-High	Standard lab analyzers, fluorescence detection
Polymer (Acrylic, Polycarbonate)	Good (Visible only)	Low-Moderate	Low	Portable devices, disposable kits
Coated Glass (AR, Bandpass)	Superior (Wavelength-specific)	High	High	Clinical analyzers, multiplex assays
Metal Alloys (Nickel, Stainless Steel)	N/A (Structural)	Very High	Very High	High-temperature instruments, rugged environments

Best Practices for Ensuring Filter Longevity

Handle with Care: Always use gloves and avoid touching optical surfaces to prevent oil transfer and micro-scratches, especially with glass and coated filters.

Regular Cleaning: Clean filters using recommended solvents (e.g., isopropyl alcohol and lint-free wipes). Avoid abrasive materials that could damage coatings or polymer substrates.

Environmental Control: Store and operate filters in controlled environments—limit exposure to humidity, extreme temperatures, and direct UV light when not in use.

Inspection Schedule: Periodically inspect filters for clouding, delamination, or physical damage. Replace immediately if optical performance degrades.

Use OEM Components: Replace filters only with manufacturer-approved parts to ensure compatibility and maintain calibration integrity.

Important: The choice of filter material should align with the analyzer’s operational demands. Using substandard or incompatible filters can lead to inaccurate readings, increased maintenance costs, and potential instrument downtime. In clinical settings, compromised filter performance may affect diagnostic accuracy, posing risks to patient outcomes. Always consult technical specifications and application guidelines before selecting or replacing filters.

Commercial Use Cases of Filters in Biochemistry Analyzers

In clinical diagnostics, pharmaceutical research, food safety, and environmental science, biochemical analyzers are essential tools for measuring the chemical composition of biological and environmental samples. At the heart of their precision lies the optical filter system—critical components that isolate specific wavelengths of light to enable accurate photometric detection. By allowing only targeted light spectra to pass through, filters enhance measurement specificity, reduce interference, and improve the reliability of analytical results. Below are key commercial applications where optical filters play a transformative role in biochemical analysis.

Clinical Diagnostics

Biochemical analyzers are the backbone of modern clinical pathology laboratories, enabling rapid and automated assessment of blood, serum, urine, and other bodily fluids. These instruments measure critical biomarkers such as enzymes (e.g., ALT, AST), electrolytes (e.g., sodium, potassium), lipids (e.g., cholesterol), and proteins (e.g., albumin), providing physicians with vital information for diagnosing diseases like diabetes, liver dysfunction, and kidney disorders.

• Optical filters isolate precise wavelengths needed for colorimetric assays, where reagents react with analytes to produce measurable color changes
• They minimize spectral interference from hemolysis, lipemia, or icterus, improving diagnostic accuracy
• Multi-wavelength filtering supports simultaneous measurement of multiple parameters in a single sample run
• High-transmission bandpass filters increase sensitivity for low-concentration biomarkers

Key impact: Enhanced diagnostic precision leads to earlier disease detection and better patient outcomes.

Pharmacology and Drug Development

In pharmaceutical R&D, biochemical analyzers equipped with advanced optical filters are indispensable for drug discovery, pharmacokinetic studies, and toxicity screening. Researchers use these systems to monitor enzyme activity, receptor binding, and metabolic pathways in response to novel compounds.

• Filters enable fluorescence and absorbance-based assays (e.g., ELISA, enzyme kinetics) by selecting excitation and emission wavelengths
• They improve signal-to-noise ratios in high-throughput screening (HTS), accelerating the identification of promising drug candidates
• Narrow-band filters allow differentiation between parent drugs and metabolites in complex biological matrices
• Temperature-stable filters maintain performance during extended assay runs

Innovation driver: Faster, more accurate screening reduces time-to-market for new therapeutics.

Food and Beverage Testing

The food and beverage industry relies on biochemical analyzers to ensure product safety, nutritional accuracy, and regulatory compliance. From detecting allergens to verifying vitamin content, these instruments help manufacturers meet strict quality standards.

• Filters enable precise quantification of nutrients such as vitamins (A, C, D), amino acids, and sugars using spectrophotometric methods
• They support detection of contaminants like mycotoxins, pesticides, and antibiotic residues in raw materials and finished products
• Specific wavelength selection improves sensitivity in alcohol and drug residue testing in consumables
• Durable, chemically resistant filters withstand exposure to solvents and cleaning agents in production environments

Quality assurance: Reliable filter performance ensures accurate labeling and consumer safety.

Environmental Monitoring

Biochemical analyzers are widely used in environmental testing labs to assess water quality, soil health, and air pollution. These applications demand high selectivity due to the complexity and variability of environmental samples.

• Optical filters enable detection of heavy metals (e.g., lead, mercury) through colorimetric or enzymatic assays
• They facilitate measurement of organic pollutants such as polycyclic aromatic hydrocarbons (PAHs) and endocrine disruptors
• Filters improve accuracy in monitoring algal toxins and microbial contaminants in drinking water
• Robust filtering systems support field-deployable analyzers used in remote or harsh environments

Public health role: Accurate pollutant detection supports regulatory compliance and ecological protection.

Technical Insight: The performance of a biochemical analyzer is only as good as its optical filtering system. High-quality interference filters with sharp cut-on/cut-off edges, minimal autofluorescence, and excellent thermal stability are essential for reproducible results. When selecting analyzers or replacement components, prioritize systems with certified optical filters that meet ISO 15198 standards for clinical chemistry instruments.

Industry	Primary Analytes Measured	Filter Function	Impact of Filter Quality
Clinical Diagnostics	Glucose, creatinine, bilirubin, enzymes	Wavelength selection for colorimetric assays	Directly affects diagnostic accuracy and false-positive rates
Pharmaceuticals	Drug metabolites, enzyme inhibitors, biomarkers	Fluorescence and absorbance specificity	Improves hit detection in screening; reduces false negatives
Food & Beverage	Vitamins, allergens, contaminants	Spectral isolation in complex matrices	Ensures label accuracy and regulatory compliance
Environmental Science	Heavy metals, pesticides, toxins	Interference reduction in turbid samples	Enhances detection limits and measurement reliability

Emerging Trends and Future Applications

• Miniaturized Filters: Development of micro-optical filters enables portable and point-of-care biochemical analyzers for field use
• Smart Filtering: Integration with AI-driven software allows dynamic wavelength adjustment based on sample characteristics
• Multi-Analyte Platforms: Advanced filter arrays support simultaneous detection of dozens of biomarkers in a single test
• Sustainability: Long-lasting, recyclable filter materials reduce waste in high-volume testing facilities
• Regulatory Alignment: Compliance with CLIA, FDA, and EU IVDR standards increasingly depends on documented optical performance, including filter specifications

How To Choose Filter in Biochemistry Analyzer

Selecting the appropriate optical filter is a critical step in ensuring accurate and reliable results from a biochemistry analyzer. These instruments rely on photometric detection to measure the concentration of biomarkers in blood, serum, urine, and other biological fluids. The filter plays a key role in isolating specific wavelengths of light that interact with chemical reactions in the sample. Choosing the wrong filter can lead to inaccurate readings, reduced sensitivity, or interference from background signals.

Important Note: Always match the filter specifications to your assay's absorbance peak. Using a mismatched filter can result in poor linearity, low sensitivity, and false results—potentially compromising patient diagnosis or research outcomes.

1. Application Requirements

The primary factor in filter selection is the specific application and type of assay being performed. Different biochemical assays generate color changes at distinct wavelengths due to chromogenic or fluorogenic reactions.

• Colorimetric Assays: Require precise bandpass filters to isolate the wavelength where the reaction product absorbs light most strongly (e.g., 540 nm for hemoglobin, 600 nm for alkaline phosphatase with p-nitrophenol).
• Enzyme-Linked Immunosorbent Assays (ELISA): Often use filters around 450 nm (for TMB substrate) or 620–650 nm (reference wavelength) to correct for optical imperfections.
• Interference Filters: Ideal for high-selectivity applications where narrow bandwidths are needed to distinguish between closely spaced absorbance peaks.
• Fluorescence Detection: May require excitation and emission filters if the analyzer supports fluorescent probes.

Understanding the spectral characteristics of your reagents and analytes ensures optimal signal-to-noise ratio and measurement accuracy.

2. Filter Material and Construction

The material and manufacturing method significantly influence filter performance, durability, and compatibility with laboratory environments.

• Optical Glass Filters: Made from borosilicate or fused silica, these offer excellent photochemical stability and resistance to thermal shock. Commonly used in bandpass filters due to their ability to maintain consistent transmission over time.
• Thin-Film Interference Filters: Constructed by depositing multiple layers of dielectric or semiconductor materials (e.g., titanium dioxide, silicon monoxide) onto glass substrates. These provide very narrow bandwidths and high out-of-band rejection, making them ideal for sensitive assays.
• Polymeric (Plastic) Filters: Lightweight and cost-effective, but prone to degradation under prolonged exposure to UV or visible light. Not recommended for long-term or high-intensity applications due to fading and reduced optical clarity.
• Chemical Resistance: Glass-based filters are highly resistant to common solvents, acids, and biological fluids, ensuring longevity in routine clinical use.

3. Durability and Maintenance Requirements

Filters must withstand repeated use, cleaning, and environmental stress without compromising optical performance.

• Metal-Housed Filters (e.g., Nickel Alloys): Provide superior mechanical strength and protection against scratches, making them ideal for high-throughput labs or portable analyzers subject to vibration.
• Low-Pass and High-Pass Filters: Often used in combination with bandpass filters to block unwanted UV or IR radiation. These require regular inspection and cleaning to prevent dust accumulation or coating damage.
• Maintenance Schedule: Inspect filters every 3–6 months for clouding, scratches, or contamination. Clean only with lens-grade materials and isopropyl alcohol to avoid surface damage.
• Replacement Frequency: Replace filters showing signs of degradation every 2–3 years, or sooner in high-use settings, to maintain photometric accuracy.

Consider your lab’s workflow, usage frequency, and technical support capabilities when selecting filters with varying maintenance needs.

4. Wavelength Range and Bandwidth

Precision in wavelength selection is essential for accurate quantification of biochemical analytes.

• Wavelength Range: Must align with the maximum absorbance (λ_max) of the reaction product. For example:
  • 340 nm – NADH/NADPH detection (dehydrogenase assays)
  • 405 nm – Protease assays using chromogenic substrates
  • 505 nm – Bilirubin measurement
  • 570 nm – Total protein (Biuret method)
  • 600 nm – Bacterial growth monitoring
• Bandwidth (Full Width at Half Maximum - FWHM): Typically ranges from 5 nm to 10 nm for high-precision analyzers. Narrower bandwidths improve selectivity but may reduce signal intensity; wider bandwidths increase throughput but risk spectral overlap.
• Out-of-Band Rejection: Should be greater than OD 4 (99.99% blocking) to minimize stray light interference, especially in multi-analyte panels.

Always verify that the filter’s spectral profile matches your assay requirements using manufacturer datasheets or spectrophotometric validation.

Filter Type	Typical Use Case	Wavelength Range	Bandwidth (FWHM)	Recommended For
Bandpass (Glass)	Colorimetric assays	340–800 nm	5–10 nm	Routine clinical testing
Interference (Thin-Film)	High-specificity assays	400–700 nm	3–6 nm	Research & multiplex panels
Longpass	Blocking UV light	Cut-on at 320+ nm	N/A	Protecting detectors
Shortpass	Blocking IR radiation	Cut-off at 750 nm	N/A	Enhancing visible range accuracy
Polymeric	Low-cost screening	Limited range	10–15 nm	Point-of-care devices

Expert Tip: When upgrading or replacing filters, always cross-reference the part number with the analyzer manufacturer’s specifications. Third-party filters may appear compatible but can differ in spectral performance, leading to calibration drift or failed QC checks.

Additional Selection Tips

• Ensure filter dimensions match the optical path of your analyzer (common sizes: 12mm, 25mm diameter).
• Choose filters with anti-reflective coatings to minimize light loss and internal reflections.
• For multi-channel analyzers, confirm that all filters are calibrated to the same optical axis to prevent alignment errors.
• Keep spare filters on hand for critical assays to minimize instrument downtime.
• Document filter installation dates and performance during quality control runs.

Selecting the right filter for your biochemistry analyzer is not just about compatibility—it's about ensuring diagnostic accuracy, reproducibility, and regulatory compliance. By carefully evaluating application needs, material properties, durability, and spectral characteristics, laboratories can optimize their analytical performance and maintain confidence in their results.

Frequently Asked Questions About Filters in Biochemical Analyzers

Q1: What role do filters play in chemical analyzers?

Filters are essential components in biochemical analyzers, serving a critical function in photometric detection. They selectively transmit specific wavelengths of light while blocking others, enabling precise interaction between light and the sample containing bioreagents. This spectral selectivity ensures that only the relevant wavelengths reach the detector, minimizing background noise and interference from unwanted light. The resulting photometric signal is then used to quantify the concentration of analytes in the sample, such as enzymes, proteins, or metabolites, thereby enhancing measurement accuracy and reliability in diagnostic and research applications.

Q2: What are the most common types of filters used in biochemical analyzers?

Biochemical analyzers rely on several specialized optical filter types, each designed for distinct performance characteristics:

• Bandpass Filters: Allow a specific range of wavelengths to pass through while blocking those above and below the designated band. These are widely used in absorbance and fluorescence measurements where high spectral precision is required.
• Optical Glass Filters: Made from colored glass that inherently absorbs certain wavelengths, these are cost-effective and commonly used in basic spectrophotometric applications.
• Long-Pass (Low-Pass) Filters: Transmit longer wavelengths and block shorter ones, often used in fluorescence detection to eliminate excitation light and allow only emission signals to pass.
• Interference Filters: Utilize thin-film coatings to reflect unwanted wavelengths and transmit desired ones through constructive and destructive interference. These offer superior wavelength selectivity and are ideal for high-performance analytical instruments.

The choice of filter type depends on the analyzer’s detection method, required sensitivity, and target analytes.

Q3: What materials are used to make filters in chemical analyzers?

The construction of biochemical analyzer filters involves materials chosen for their optical clarity, durability, and compatibility with various light spectra:

• Optical Glass: The most common substrate due to its excellent transparency across UV, visible, and near-infrared ranges. It provides thermal stability and resistance to environmental degradation.
• Polymeric Materials: Used in lower-cost or disposable filter applications. Polycarbonate and acrylic offer good transmission in the visible range but may degrade under prolonged UV exposure.
• Coated Filters: Feature advanced thin-film coatings applied to glass or polymer substrates to achieve precise spectral performance. These include dielectric or metallic coatings (e.g., aluminum, silver, or nickel alloys) that enhance reflectivity or transmission at specific wavelengths.

High-end analyzers often use multi-layer coated glass filters to ensure long-term stability, minimal autofluorescence, and resistance to chemical exposure during cleaning and operation.

Q4: What factors should be considered when selecting a filter for a biochemical analyzer?

Selecting the right filter is crucial for optimal analyzer performance. Key considerations include:

• Application Requirements: Different assays (e.g., ELISA, enzyme kinetics, immunoassays) require specific wavelength bands. Matching the filter to the absorption or emission peak of the chromophore or fluorophore is essential.
• Filter Material: Glass is preferred for high-precision applications due to its durability and optical consistency, while polymers may suffice for less demanding uses.
• Durability and Maintenance: Filters must withstand repeated exposure to light sources, temperature fluctuations, and cleaning agents. Coated filters should resist delamination and scratching.
• Bandwidth and Wavelength Range: Narrow bandwidths increase specificity but reduce signal intensity; wider bands improve sensitivity but may allow spectral overlap. The center wavelength must align precisely with the assay’s requirements.
• Blocking Efficiency (OD Rating): High optical density (OD) in the blocking range ensures minimal stray light interference, which is critical for low-concentration detection.
• Angle of Incidence Sensitivity: Some interference filters shift wavelength transmission based on incident angle, which must be accounted for in optical design.

Proper selection ensures accurate, reproducible results and extends the lifespan of the analyzer’s optical system.

Q5: What are the ideal applications of filters in biochemical analyzers?

Filters play a pivotal role in enhancing the accuracy and reliability of measurements across a wide range of scientific and industrial fields:

• Clinical Pathology: Used in automated analyzers for blood tests (e.g., glucose, cholesterol, liver enzymes), where precise wavelength selection enables accurate quantification of biomarkers in serum and plasma.
• Drug Discovery: Facilitate high-throughput screening by isolating fluorescence or absorbance signals from compound libraries, supporting early-stage pharmaceutical development.
• Food and Beverage Testing: Enable detection of contaminants, additives, and nutritional content (e.g., protein, sugar levels) through colorimetric assays that rely on consistent light filtering.
• Environmental Monitoring: Support water and air quality analysis by detecting pollutants like nitrates, phosphates, and heavy metals using spectrophotometric methods with tailored filter sets.
• Research Laboratories: Used in enzyme kinetics, DNA quantification, and cell viability assays where reproducibility and sensitivity are paramount.

In all these applications, high-quality optical filters improve signal-to-noise ratios, reduce false positives, and contribute to regulatory compliance in diagnostic and analytical testing.