HPLC Dark Current Measurement via Light Blocking Means
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Solution Overview
Problem
Conventional HPLC systems with photodiode array detectors face challenges in measuring dark current quickly enough to avoid missing sample components due to reduced sample separation times, leading to incomplete detection of sample components.
Innovation Solution
An analysis system with an automatic sample feeding apparatus and optical measuring apparatus that includes light blocking means to measure dark current simultaneously with sample selection or change, allowing for independent dark-current and normal measurement operations, ensuring dark current measurement is completed before sample introduction into the column.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a mechanical shutter is used to block light for dark current measurement, then dark current can be measured, but the measurement time becomes too long (6-7 seconds) causing sample components to reach the detector before measurement completion
Solution Approach 1:
The patent replaces the mechanical shutter system with an optical solution. A dummy sample (light-blocking substance) is placed in the sample holder to block light from reaching the photodiode array detector during dark current measurement. This eliminates the need for mechanical shutter movements, reducing measurement time from 6-7 seconds to under 10 seconds while maintaining measurement accuracy.
Solution Approach 2:
The system performs dark current measurement during the sample preparation phase, specifically during the period when the automatic sampler is selecting and preparing the next sample. By utilizing this idle time for dark current measurement, the system ensures that dark current data is ready before the actual sample analysis begins, preventing any loss of sample components.
2Reliability
If dark current measurement is performed after sample injection, then the detector is ready for sample detection, but sample components may be missed due to reduced separation times
Solution Approach 1:
The system performs dark current measurement in advance during sample preparation, before the sample is injected into the chromatography column. This preliminary action ensures that the detector is fully ready and dark current data is obtained without delaying sample analysis, thereby maintaining both reliability and productivity.
Solution Approach 2:
The system maintains continuous operation by overlapping dark current measurement with sample preparation activities. The automatic sampler selects and prepares samples while the detector simultaneously measures dark current, ensuring that no time is wasted and sample components are never missed regardless of separation speed.
3Productivity
If the time period from sample injection to component elution is reduced for higher throughput, then productivity increases, but dark current measurement cannot be completed before sample components reach the detector
Solution Approach 1:
Dark current measurement is performed in advance during the sample preparation phase, before sample injection occurs. This preliminary action decouples the dark current measurement time from the sample analysis time, allowing both to occur in parallel and eliminating any conflict with reduced separation times.
Solution Approach 2:
The system achieves continuous productive operation by utilizing the sample preparation time for dark current measurement. While the automatic sampler is selecting and preparing the next sample, the detector simultaneously completes dark current measurement, ensuring that all processes occur in parallel without interfering with the reduced separation time needed for high throughput.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables reliable detection of sample components without missing any parts, even with rapid sample elution, by completing dark current measurement before sample introduction, thus providing accurate absorption spectra.
Implementation Method 1
light blocking means adapted to be selectively interposed in a light path between the light source means and the light detection means to block off the light emitted from the light source means
Implementation Method 2
wavelengths of transmitted light which has undergone absorption during passing of the emitted light through the sample are spectrally dispersed by a spectral dispersion device, such as a diffraction grating
Implementation Method 3
an intensity of the light with the wide wavelength is concurrently detected by the photodiode array detector. This type of spectrophotometer is capable of measuring an absorption spectrum in a given wavelength band
Data Source
AI summary
Analysis system including a central control section for generally controlling the analysis that sends a command to perform a pre-injection operation, to an automatic sampler together with information designating a sample to be selected, such as an identification number, and simultaneously sends a command to perform an operation of measuring a dark current in a photodiode array (PDA) detector, to a multi-channel spectrophotometer. Thus, the automatic sampler performs the pre-injection operation, such as an operation of moving a needle to a position of a designated vial container to suck a sample, and the spectrophotometer performs the dark-current measurement operation during a time period of the pre-injection operation. After the sample is actually introduced into the column, in response to a command to perform a normal measurement operation, an operation of acquiring absorption data of an eluate from the column is started without performing the dark-current measurement operation.