Fabrication of an Optical Cell Dryer for the Spectroscopic Analysis Cells

Summary

A protocol for fabricating a device for simultaneously drying multiple optical cells is presented.

Abstract

Optical cells, which are experimental instruments, are small, square tubes sealed on one side. A sample is placed in this tube, and a measurement is performed with a spectroscope. The materials used for optical cells generally include quartz glass or plastic, but expensive quartz glass is reused by removing substances, other than liquids, to be analyzed that adhere to the interior of the container. In such a case, the optical cells are washed with water or ethanol and dried. Then, the next sample is added and measured. Optical cells are dried naturally or with a manual hairdryer. However, drying takes time, which makes it one of the factors that increase the experiment time. In this study, the objective is to drastically reduce the drying time with a dedicated automatic dryer that can dry multiple optical cells at once. To realize this, a circuit was designed for a microcomputer, and the hardware using it was independently designed and manufactured.

Introduction

Optical cells are used as laboratory instruments in a wide range of fields. In life science research, biomolecules such as nucleic acids and proteins are often utilized for experiments, and spectroscopic methods are widely used for quantitative methods. Accurately quantifying the sample of the experiment is indispensable for obtaining more accurate and reproducible results. The absorption spectrum obtained by a spectrophotometer has often been used for the quantification of biomolecules such as nucleic acids and proteins^1,2,3,4. Research on oxidation-reduction characteristics caused by the change in the absorption spectrum and photoluminescence of a carbon nanotube (CNT) dispersed using DNA has also been conducted^5,6,7,8,9,10. Optical cells are used for these measurements, but accurate measurements cannot be made unless they are thoroughly washed and dried.

When measuring absorption spectra or photoluminescence, it is impossible to measure precisely in dirty optical cells^{11,12,13,14,15}. Economical disposable optical cells made of polystyrene and poly-methyl-methacrylate are also used to eliminate washing and contamination. However, when precise measurements are required, quartz glasses are often used, because they have extremely excellent optical properties such as light transmittance. In this case, the optical cells are washed after the measurement of the sample and repeatedly used. Usually, after washing optical cells with water or ethanol, they are dried naturally. When rapid drying is required, they are dried one by one by using hair dryers or similar equipment. Cleaning optical cells is one of the most unpleasant and time-consuming procedures in the experiment. As the number of samples increases, the drying time increases, which, in turn, increases the time required to conduct the experiment and research. In past studies, there have been no reports on peripheral devices of optical cells. This study aims to reduce the research time by drying multiple optical cells simultaneously.

We investigated whether other similar products exist. A box-type constant temperature dryer with a temperature control function and a timer function already exists; however, no commercial products with the same configuration can be found.

An outline of the production of this device is described. First, the box-type case is made using an acrylic plate. Nylon netting is attached to the top. A plastic grid is placed on it to fix the optical cell. The control circuit is stored inside the case, and the plastic plate is attached to protect the circuit from water droplets. The control circuit consists of a CPU and is controlled by software. Blowers are attached to the back of the case, and the wind supplied by the blowers enters the optical cells set upside down. The blowers are activated by a switch on the front, and they are automatically stopped by the timer. Depending on the number of optical cells to be dried, two or four blowers can be selected for operation. Water droplets dripping from the optical cells evaporate with the wind from the blowers. The quartz cells are washed with water or ethanol, and the drying time is compared with that of natural drying.

Protocol

1. Design See Figure 1 for details of the development drawing. Cut a 3-mm thick acrylic board to 210 mm in width x 60 mm in height x 104 mm in depth, bond with acrylic adhesive and assemble the case. Install as many as 30 optical cells of 12.5 x 12.5 mm. Attach switches and lamps for starting and stopping and a variable dial for the drying time setting on the front face of the casing. See Figure 2 for an extern…

Representative Results

As shown in Table 1, in the case of ethanol washing, the average drying time in natural drying was 426.4 s, and the average drying time in the optical-cell dryer was 106 s. In the case of water washing, the average drying time in natural drying was 1481.4 s, and the average drying time in the optical-cell dryer was 371.6 s. In both cases, the drying time was reduced to approximately one-fourth. The drying time distribution of the optical-cell dryer is shown in <strong cla…

Discussion

The optical cells can be dried simultaneously with the blowers, and the drying time can be considerably reduced. Even if the stop operation is not executed, it can be safely stopped by using the automatic stop function of the timer. From the measurement results of the drying time distribution, there was no significant difference in drying time because of the difference in the installation position of the optical cells.

A critical step of the protocol is the design of the casing. The challenge …

Materials

blower	ebm-papst	422JN	Mulfingen, Germany
Microcomputer	Atmel Corporation	ATmega 328 P	CA, USA
Blower selection button	Sengoku Densyo Co., Ltd.	MS-358 (red)	Tokyo, Japan
Blower operationg lamp	Akizuki Denshi Tsusho Co., Ltd.	DB-15-T-OR	Tokyo, Japan
Blower start button	Sengoku Densyo Co., Ltd.	MS-350M (white)	Tokyo, Japan
Timer	Akizuki Denshi Tsusho Co., Ltd.	SH16K4A105L20KC	Tokyo, Japan
Power supply switch	Marutsuelec Co., Ltd.	3010-P3C1T1G2C01B02BKBK-EI	Tokyo, Japan
Power supply lamp	Akizuki Denshi Tsusho Co., Ltd.	DB-15-T-G	Tokyo, Japan
OLED module	Akihabara Co., Ltd.	M096P4W	Tokyo, Japan