JP2004085525A

JP2004085525A - Method for determining concentration of very small amount ammonia in air

Info

Publication number: JP2004085525A
Application number: JP2002349799A
Authority: JP
Inventors: Eriko Wakui; 涌井　絵里子; Takeshi Wakui; 涌井　健; Yukinari Takahashi; 高橋　幸成; Masayuki Ichino; 市野　雅之; Akio Sakae; 寒河江　昭夫; Yoshinobu Arai; 荒井　良延; Hiroaki Honma; 本間　弘明; Teruo Muramatsu; 村松　輝夫
Original assignee: Kajima Corp; Komyo Rikagaku Kogyo KK
Current assignee: Kajima Corp; Komyo Rikagaku Kogyo KK
Priority date: 2002-06-24
Filing date: 2002-12-02
Publication date: 2004-03-18

Abstract

<P>PROBLEM TO BE SOLVED: To enable every one to easily determine a very small amount of ammonia, in real time which is present in air in an art museum, a clean room, etc. and harms works of art, electronic devices, etc. <P>SOLUTION: A tube comprises an air inlet and an exhaust opening. A detecting agent, which is discolored by reaction with ammonia is filled in the tube in such a way as to be seen through from outside the tube to form an ammonia-detecting tube. When the concentration of ammonia is determined through the use of the ammonia detecting tube on air, in which ammonia of an amount of 50 μg/m<SP>3</SP>or less is present, the air inlet of the detecting tube is opened to a measuring space. The exhaust opening is connected to a suction means, to continuously pass the air in the space through the tube at a uniform quantity of flow between 200-600 mL/min at least for 30 minutes or longer. From the integrated value of the total amount of air, passed through the tube and the length of discoloration of the detecting agent, the concentration of ammonia in the air is determined in the method for determining the trace amount of ammonia in air. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は，空気中の極微量のアンモニアを簡易に定量できるようにした微量アンモニア濃度の定量法に関する。
【０００２】
【従来の技術】
美術館や博物館などでは，外気や，建築材料・入館者などに由来する微量のアンモニアによって，絵画や写真等の文化財が変色・劣化する危険にさらされている。また，電子デバイス製造施設等のクリーンルームにおいても，アンモニアが製品の歩留り低下を起こすことがある。後者の場合には，清浄空気中に微量に存在するアンモニア（通常２０μｇ／ｍ^３以下）がＳＯ_ｘと塩を作り_，これがウェーハ等の表面に付着することによって歩留り低下を起こさせると言われている。
【０００３】
このため，空気中のアンモニアの低減が必要となるが，それに伴い_，空気中の微量のアンモニア濃度の管理が必要である。そのためには，まず，空気中の微量のアンモニア濃度を定量できることが肝要である。
【０００４】
従来より，作業環境や悪臭及び工程管理などを対象として一定量のガス体を採集して数ｐｐｍ〜数％のアンモニア濃度を検出する方法が知られている。しかし，この方法では美術館や半導体工場等のクリーンルームのようにアンモニア濃度が５０μｇ／ｍ^３以下，場合によっては１０μｇ／ｍ^３以下の空気の場合にはアンモニア濃度を正確に定量できない。空気中の微量のアンモニア濃度の測定は現在のところ，インピンジャーを用いる液体捕集−イオンクロマトグラフィー法が主流となっており，この測定法は，微量なアンモニアを定量する方法としては非常に優れた方法であると言える。
【０００５】
【発明が解決しようとする課題】
イオンクロマトグラフィー法によるアンモニアの定量は，分析コストや専門知識を必要とし，結果の判定までに数週間を要することもある。このため，現場の管理者によって，アンモニア濃度の対応・評価が簡単には行えないという問題があった。なお，美術館の場合には，空気の酸・アルカリを判定するｐＨ試験紙などを用いて目視で判定する環境モニター方法もあるが，酸性物質とアルカリ性物質の総合的な影響による判定法なので，美術館で問題となるアンモニア単独での評価が困難であった。他方，クリーンルームでは１μｇ／ｍ^３程度まで，場合によってはそれ以下のアンモニア濃度を計測できることが求められるが，それをその現場でリアルタイムに且つ誰でも正確に測定できるのが望ましい。本発明はこのような要望を満たすことを目的としたものである。
【０００６】
【課題を解決するための手段】
本発明によれば，空気取入口および排気口を有する管内に，アンモニアと反応して変色する検知剤を管外部から透視可能に装填してなるアンモニア検知管を用いて５０μｇ／ｍ^３以下の量のアンモニアが存在する空気を測定対象としてアンモニア濃度を定量するにさいし，該検知管の空気取入口を測定空間に開放し，該排気口を吸引手段に連結して該空間内の空気を２００〜６００ｍＬ／ｍｉｎ内の一定流量で少なくとも３０分以上連続的に管内に通気させ，管内を通過した総空気量の積算値と該検知剤の変色長とから当該空気中のアンモニア濃度を定量することを特徴とする空気中の微量アンモニア濃度の定量法を提供する。ここで，検知管内に装填する検知剤としては，酸と　ｐＨ指示薬とからなる試薬を平均粒径が２５０μｍ〜３５０μｍのケイ砂の粒子表面にコーティングしてなる粉体を使用するのが好ましく，この粉体は，ＢＥＴ法による比表面積が０．０５〜０．１ｍ^２／ｇ　であるのがよく，また，その粉体ｐＨが４〜６に調整されたものであるのが好ましい。
【０００７】
【発明の実施の形態】
本発明者らは，リアルタイムで微量のアンモニアを簡易に検出すべく，種々の試験を繰り返した結果，管内に装填した所定の検知剤に対して所定の空気量を所定の時間をかけて連続的に通気させ，該検知剤の変色の程度を長さ変化で表示させると，微量のアンモニア濃度を適正に検出できることがわかった。具体的には，所定の検知剤を装填したペンシル形状の小さな管内にサンプリング空気を吸引ポンプによって２００〜６００ｍＬ／ｍｉｎ内の一定流量で少なくとも３０分以上連続的に管内に通気させ，その通気量がある一定に達した時の検知剤の変色の程度を長さ変化で検量して，空気中のアンモニア濃度を定量化するのである。
【０００８】
図１に本発明に従うアンモニア検知管の１例を示したが，この例では，透明のガラス管１の内部に検知剤２が装填してある。ガラス管１の全長は１３０ｍｍで内径はφ４ｍｍである。このガラス管１内において，検知剤２が，二つの気体透過性の栓３ａと３ｂによって位置決められている。検知剤２と各栓３ａおよび３ｂの間には，それぞれ非反応性の保護剤４ａと４ｂが介装され，これらの保護剤４ａと４ｂの間に，検知剤２が一定の長さＬをもって装填されている。そして，この長さＬにわたって，その管の長さ方向に目盛り７が付されている。
【０００９】
管１の両端は溶封してあるが，使用時に開口し，その一端は空気取入口５として，他端は排気口６として用いられる。前記のように，検知剤２は，空気取入口５から排気口６の方向に一定の長さＬをもって装填され，空気取入口５の側から測定用空気が導入されると，測定空気中の微量のアンモニアが検知剤２の試薬と反応し，その反応に消費された分の長さだけ，空気取入口５に近い方から変色することになる。
【００１０】
検知剤２は，各種のものが使用できるが，下式（１）
２ＮＨ_３＋Ａｃｉｄ＋　ｐＨ　Ｉｎｄｉｃａｔｏｒ　→　ｙｅｌｌｏｗ　ｒｅａｃｔｉｏｎ　ｐｒｏｄｕｃｔ　・・（１）
の原理に従って，　アンモニアが酸と反応して淡紫色から淡黄色を呈する呈色反応を利用するのが好適である。酸としてはリン酸が使用でき，この場合にはアンモニアがリン酸と下式（２）　に従って反応して，　ｐＨ指示薬が淡紫色から淡黄色に変色する。
２ＮＨ_３＋　Ｈ_３ＰＯ_４　→　（ＮＨ_４）_２ＨＰＯ_４　・・（２）
【００１１】
測定にさいしては，検知管８内に装填された検知剤２に対し，通過する空気中のアンモニアの実質的に全てが酸と反応して変色を起こし，しかもその変色が，検知剤２の長さ方向に（空気の入側から出側の方向に），通気量に対応して順序よく起きることが必要である。そして美術館やクリーンルームのように５０μｇ／ｍ^３以下の微量のアンモニアが存在する空気を測定対象とする場合には，測定時間中において検知剤２に対して測定空気がまんべんなく検知剤２と接触しつつ流れることが肝要である。換言すれば，空気の入側近くに存在する検知剤２が変色せずに，それより下流側に存在する検知剤２が先に変色したり，空気中のアンモニアが反応せずに検知剤２を通過したりすると，変色長さでアンモニア濃度を定量することが出来なくなるので，このような現象が起きないようにする必要がある。
【００１２】
アンモニア濃度が５０μｇ／ｍ^３以下の空気を測定対象とする場合の検知剤２としては，平均粒径が２５０μｍ〜３５０μｍのケイ砂の粒子表面に，前記（１）　式の酸とｐＨ指示薬をコーティングしてなる粉体であって，ＢＥＴ法による比表面積が０．０５〜０．１ｍ^２／ｇ　で，粉体ｐＨが４〜６に調整されたものを使用するのがよいことがわかった。とくに破砕されたケイ砂を分級して平均粒径が２５０μｍ〜３５０μｍのものに整粒したものは，各粒子表面は凹凸を有することもあって，これを検知管８内に装填したときに，空気が粒子の間を良好に分散しながら流れるようになり，空気の流れが粉体中で短絡したり偏流が発生するようなことが回避できる。
【００１３】
このようなケイ砂の粒子表面に前記（１）　式の酸とｐＨ指示薬をコーティングしてなる粉体が，ＢＥＴ法による比表面積の値が０．０５ｍ^２／ｇ　未満では粒子表面の凹凸の程度が少なく，滑らかな表面をもつものが多くなって，検知管８に装填された検知剤２中を流れる空気流もなめらかになり，粉体中で短絡したり偏流したりして，良好な分散流れが得られない。他方，ＢＥＴ法による比表面積の値が０．１ｍ^２／ｇ　を超えるようなものでは，粒子表面の凹凸が多すぎて検知管８内への装填にさいして流動性が悪くなって粒子間同士でブリッジが発生したり均等な隙間を形成するのが困難となり，この場合にも，空気流れが短絡したり偏流したりするので好ましくない。また，該粉体の比表面積が０．０５ｍ^２／ｇ　より小さすぎる場合，或いは平均粒径が３５０μｍより大きすぎる場合には，反応密度が粗となって変色の境界が不明確となり，読み取りが困難となることがわかった。さらに，比表面積が０．１ｍ^２／ｇ　より大きすぎる場合，或いは平均粒径が２５０μｍより小さすぎる場合には，変色の境界は明確になるが，感度が落ちるようになり，目的の濃度を測定することが困難になる。したがって，平均粒径が２５０μｍ〜３５０μｍのケイ砂の粒子表面に，前記（１）　式の酸とｐＨ指示薬をコーティングしてなる，ＢＥＴ法による比表面積が０．０５〜０．１ｍ^２／ｇ　の粉体を検知剤２として使用することが望ましい。
【００１４】
この検知剤２を図１の検知管８に所定の長さＬだけ装填し，アンモニアが５０μｇ／ｍ^３以下で存在する空気を２００〜６００ｍＬ／ｍｉｎ内の一定流量で少なくとも３０分以上連続的に管８内に通気させた場合に，管８内を通過した総空気量の積算値と該検知剤２変色長とから当該空気中のアンモニア濃度を正確に定量できることがわかった。
【００１５】
図２は，図１のアンモニア検知管８の排気口６をチャック９に固定し，このチャック９から通気管１０を介して吸引ポンプ等の吸引手段１１に連結した状態を示しており，吸引手段１１の作動により，アンモニア検知管８の空気取入口５から測定対象空気がアンモニア検知管８内に通気する。通気管１０には流量計１２が介装されており，チャック９，通気管１０，吸引手段１１および流量計１２などは，流量積算計やタイマー等（いずれも図示せず）と共に一つのアセンブリ機器１３として持ち運び可能にセットすることができる。吸引手段１１は，その排気が測定結果に影響を与えように対処してある機器であるのが好ましい。
【００１６】
アンモニア濃度が５０μｇ／ｍ^３以下といった微量のアンモニア濃度の空気を対象として，そのアンモニア濃度を定量するには，検知剤２に触れる以前にアンモニアが吸着されてはならず，また，２００〜６００ｍＬ／ｍｉｎ内の一定流量で少なくとも３０分以上連続的に管８内に通気する必要がある。
【００１７】
以下に，図１のアンモニア検知管８を用いた測定例を挙げて，本発明をさらに説明する。
【００１８】
検知管８内に装填する栓３ａ，３ｂにはフッ素樹脂テフロン（登録商標）を使用し，吸引手段（連続吸引式ポンプ）１１による吸引流量を約４００ｍｌ／ｍｉｎの流量で１時間通気の設定とし，平均粒径が約３００μｍのケイ砂（粉体ｐＨが約５）にリン酸とｐＨ指示薬を担持させた検知剤２を管８（内径：φ４ｍｍ）内に長さＬ（３０ｍｍ）をもって装填した。この粉状検知剤２のＢＥＴ法による比表面積は０．０７ｍ^２／ｇ　である。この構成により，空気取入口５から管８内に導入する空気に同伴するアンモニアは，先ずリン酸と反応し，この中和反応が進行した分の長さだけｐＨ指示薬が淡紫色から淡黄色に変色する。すなわち，管８内に導入されたアンモニアの全てがリン酸との中和反応に消費されると仮定し，この中和反応の消費分を長さ変化で定量化する。具体的には，４００ｍｌ／ｍｉｎの流量で１時間通気したとき，ｐＨ指示薬の長さ（Ｌ＝３０ｍｍ）の全長が変色するアンモニア濃度が７０μｇ／ｍ^３となるように，リン酸量を調整し，この量のリン酸を均一にケイ砂に担持させると共に，ｐＨ指示薬も均一にケイ砂に担持させた。この例のものを「高感度型検知管」と呼ぶ。このものは，美術館等におけるアンモニア濃度の検出に適する。
【００１９】
これと同じように，４００ｍｌ／ｍｉｎの流量で１時間通気したとき，ｐＨ指示薬の長さ（Ｌ＝３０ｍｍ）の全長が変色するアンモニア濃度が７μｇ／ｍ^３となるように，リン酸量を調整し，この量のリン酸を均一に前記と同じケイ砂に担持させると共に，ｐＨ指示薬も均一にケイ砂に担持させた。この例のものを「超高感度型検知管」と呼ぶ。このものは，電子デバイス製造施設等のクリーンルームにおけるアンモニア濃度の検出に適する。
【００２０】
いずれの検知管とも，目盛り７を作成するために，動的校正方法（例えばパーミエーションチューブ法）などを用いて校正ガスを連続的に発生させて前記の条件で通気させ，校正ガスのアンモニア濃度と検知剤２の変色長さとの関係から，それぞれ図３（高感度型検知管）および図４（超高感度型検知管）の検量線を作成し，その検量線を基に目盛り７を検知管に付した。
【００２１】
このようにして得た「高感度型検知管」を美術館を対象とし，また「超高感度型検知管」をクリーンルームを対象として，それらのアンモニア濃度の測定を行った。計測対象に用いた建物の概要を表１に示した。
【００２２】
【表１】

【００２３】
表１の「空気質ラボ」は，化学物質を極限まで低減した研究施設（空気質評価室）である。
【００２４】
試験においては，本発明の検知管の評価を行うために，計測対象建物内の空気中のアンモニアをインピンジャーによる液体捕集でサンプリング後，イオンクロマトグラフィーでアンモニウムイオンを定量した（以下「精密法」という）。美術館における精密法のサンプリングは１〜２時間とし，クリーンルームではアンモニア濃度がさらに微量であるため，精密法のサンプリングは２４時間行った。
【００２５】
高感度型検知管および超高感度型検知管とも，定量に要する検知管の吸引時間は１時間（流量４００ｍｌ／ｍｉｎの一定）とし，吸引・計測後ただちに検知管の目盛り７を読みとった。
【００２６】
まず，高感度型検知管と超高感度型検知管との整合性を評価するために，両者を同時に用いて，計測対象建物内の計測場所Ａ〜Ｅで測定した。その結果を図５に示した。図５に見られるように，アンモニア濃度が３．５μｇ／ｍ^３から２７μｇ／ｍ^３の範囲でほぼ同様の結果が得られており，両者の検知管による測定結果には大きな差は見られないことがわかる。
【００２７】
次に，高感度型検知管を用いて美術館のアンモニア濃度を測定した。その結果を，精密法による計測値と対比して図６に示した。図６の結果から，１２μｇ／ｍ^３から８６μｇ／ｍ^３までの範囲で検知管の計測値は精密法に比べて若干高めを示すものの，精密法と検知管の計測値には強い相関があり（相関係数＝０．９６），本発明による検知管はその検量線の適正な校正によって正確なアンモニア定量器となることがわかる。
【００２８】
他方，超高感度型検知管を用いてクリーンルームのアンモニア濃度を測定し，その結果を，精密法による計測値と対比して図７に示した。図７の結果から明らかなように，超清浄濃度から通常のクリーンルーム濃度範囲で，本発明による検知管によるアンモニア濃度の測定結果と精密法との間で良い相関が得られた（相関係数＝０．９９５）。
【００２９】
以上の試験は，４００ｍＬ／ｍｉｎの流量で６０分間の通気を行ったものであるが，本発明はこの条件にこれに限られるものではない。本発明に従う検知剤２に対して，２００〜６００ｍＬ／ｍｉｎ内の一定流量で少なくとも３０分以上連続的に管８内に通気させることによって同様の結果を得ることができる。これにより，少なくとも６Ｌの空気量を連続的に検知剤２と接触させることになる。本発明者らの経験によると２００ｍＬ／ｍｉｎ以上，６００ｍＬ／ｍｉｎ以下の流量で，３０分以上連続的に通気した場合に，前記の試験と同等の測定結果が得られることが確認された。この流量以外の範囲では外乱が生ずることがあり，また連続的に通気する総空気量が６Ｌ未満では，５０μｇ／ｍ^３以下のアンモニア濃度を正確に測定するには，サンプリング量が不足することがわかった。
【００３０】
なお前記の試験は，図１〜２に示した形状の検知管８を用いたものであるが，検知管８の形状・寸法は図示のものに限られるものではない。例えば検知管８内に装填する栓３ａ，３ｂはフッソ樹脂に限られるものではなく，検知剤２の担体についても，ケイ砂以外に例えばゼオライトやシリカゲル等を使用することができ，また，酸としてリン酸に代えて硫酸等の非揮発性の酸を使用することもできる。さらに，管８の全体を透明ガラスとする代わりに，検知剤２の装填箇所だけを透明部材で構成してもよいし，ガラスに代えてアクリル樹脂等の透明プラスチック材料を使用してもよい。
【００３１】
【発明の効果】
以上説明したように，本発明に従うアンモニア検知管によれば，美術館やクリーンルーム等の空気中に存在する微量のアンモニアを，リアルタイムで誰でも簡単に定量的に計測することができるので，美術品の保存管理・電子デバイスの歩留り管理に多いに貢献することができる。
【図面の簡単な説明】
【図１】本発明のアンモニア検知管の１例を示した略断面図である。
【図２】図１のアンモニア検知管を用いて空気中アンモニア濃度の測定状態を示した機器配置系統図である。
【図３】本発明に従う高感度型検知管の検量線を示す図である。
【図４】本発明に従う超高感度型検知管の検量線を示す図である。
【図５】本発明に従う高感度型検知管と超高感度型検知管を同時に用いて，計測場所Ａ〜Ｅで測定したアンモニア濃度の測定結果を示した図である。
【図６】本発明に従う高感度型検知管を用いて美術館のアンモニア濃度を測定した結果を，精密法による計測値と対比して示した図である。
【図７】本発明に従う超高感度型検知管を用いてクリーンルームのアンモニア濃度を測定した結果を，精密法による計測値と対比して示した図である。
【符号の説明】
１　ガラス管
２　検知剤
３　栓
４　保護剤
５　空気取入口
６　排気口
７　目盛り（検量線）
８　アンモニア検知管
９　チャック
１０　通気管
１１　吸引手段
１２　流量計
１３　アセンブリ機器[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for quantifying a trace amount of ammonia so that a trace amount of ammonia in the air can be easily determined.
[0002]
[Prior art]
In art museums, museums, etc., there is a risk that cultural properties such as paintings and photographs will be discolored and deteriorated by the open air and trace amounts of ammonia derived from building materials and visitors. Also, in a clean room such as an electronic device manufacturing facility, ammonia may cause a reduction in product yield. In the latter case, it is said that a small amount of ammonia (usually 20 μg / m ³ or less) present in the clean air forms a salt with SO _x _, which is attached to the surface of a wafer or the like _, thereby lowering the yield. I have.
[0003]
Therefore, it is necessary to reduce the ammonia in the air, _accordingly, it is necessary to manage the ammonia concentration of trace amounts of air. For that purpose, first, it is important to be able to quantify the trace ammonia concentration in the air.
[0004]
2. Description of the Related Art Conventionally, there has been known a method of collecting a certain amount of a gaseous substance for a work environment, an odor, a process control, and the like and detecting an ammonia concentration of several ppm to several%. However, this method cannot accurately quantify the ammonia concentration in the case of air having an ammonia concentration of 50 μg / m ³ or less, and in some cases 10 μg / m ³ or less, as in a clean room such as an art museum or a semiconductor factory. At present, the measurement of trace ammonia concentration in the air is mainly conducted by liquid collection-ion chromatography using an impinger, and this measurement method is very excellent as a method for quantifying trace ammonia. It can be said that it is a method.
[0005]
[Problems to be solved by the invention]
The determination of ammonia by ion chromatography requires analytical costs and expertise and may require several weeks to determine the results. For this reason, there has been a problem that the manager of the site cannot easily handle and evaluate the ammonia concentration. In the case of art museums, there is also an environmental monitoring method that visually determines the acidity and alkalinity of air using a pH test paper, etc. However, it was difficult to evaluate ammonia alone, which is a problem. On the other hand, in a clean room, it is required that the ammonia concentration can be measured up to about 1 μg / m ³ , and in some cases, lower than that, but it is desirable that anyone can accurately measure the ammonia concentration in real time at the site. The present invention is intended to satisfy such a demand.
[0006]
[Means for Solving the Problems]
According to the present invention, an amount of 50 μg / m ³ or less is obtained by using an ammonia detection tube in which a detection agent that reacts with ammonia and changes color is loaded into a tube having an air inlet and an exhaust port so as to be visible through the outside of the tube. In quantifying the ammonia concentration using the air in which ammonia exists as the measurement object, the air inlet of the detection tube is opened to the measurement space, and the exhaust port is connected to the suction means to remove the air in the space from 200 to A constant flow rate within 600 mL / min is continuously passed through the tube for at least 30 minutes, and the ammonia concentration in the air is determined from the integrated value of the total amount of air passing through the tube and the discoloration length of the detection agent. The present invention provides a method for determining trace ammonia concentration in air. Here, as the detection agent to be charged into the detection tube, it is preferable to use a powder obtained by coating the surface of silica sand particles having an average particle size of 250 μm to 350 μm with a reagent composed of an acid and a pH indicator. The powder preferably has a specific surface area of 0.05 to 0.1 m ² / g according to the BET method, and preferably has a powder pH adjusted to 4 to 6.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
The present inventors have repeated various tests in order to easily detect a trace amount of ammonia in real time, and as a result, a predetermined amount of air has been continuously applied over a predetermined time to a predetermined detection agent loaded in the pipe. It was found that a small amount of ammonia concentration could be detected properly by allowing the air to pass through and displaying the degree of discoloration of the detection agent by a change in length. Specifically, sampling air is continuously ventilated into a small pencil-shaped tube loaded with a predetermined detection agent at a constant flow rate of 200 to 600 mL / min for at least 30 minutes by a suction pump. The degree of discoloration of the detection agent when it reaches a certain level is calibrated by length change, and the ammonia concentration in the air is quantified.
[0008]
FIG. 1 shows an example of an ammonia detection tube according to the present invention. In this example, a detection agent 2 is loaded inside a transparent glass tube 1. The total length of the glass tube 1 is 130 mm and the inner diameter is 4 mm. In the glass tube 1, the detection agent 2 is positioned by two gas-

permeable plugs

3a and 3b. Non-reactive

protective agents

4a and 4b are interposed between the detecting agent 2 and the

stoppers

3a and 3b, respectively, and the detecting agent 2 has a certain length L between these

protective agents

4a and 4b. Is loaded. A scale 7 is provided over the length L in the length direction of the tube.
[0009]
Although both ends of the tube 1 are sealed, they are opened at the time of use, and one end is used as an air inlet 5 and the other end is used as an exhaust port 6. As described above, the detecting agent 2 is loaded with a certain length L in the direction from the air inlet 5 to the exhaust port 6, and when the measuring air is introduced from the air inlet 5 side, the detecting agent 2 A small amount of ammonia reacts with the reagent of the detecting agent 2 and changes its color from the side closer to the air inlet 5 by the length consumed by the reaction.
[0010]
As the detecting agent 2, various types can be used.
2NH ₃ + Acid + pH Indicator → yellow reaction product (1)
According to the principle described above, it is preferable to use a color reaction in which ammonia reacts with an acid to give a pale purple to pale yellow color. Phosphoric acid can be used as the acid. In this case, ammonia reacts with phosphoric acid according to the following formula (2), and the pH indicator changes from pale purple to pale yellow.
2NH ₃ + H ₃ PO ₄ → (NH ₄ ) ₂ HPO ₄ ... (2)
[0011]
In the measurement, substantially all of the ammonia in the passing air reacts with the acid to cause a change in the color of the detection agent 2 loaded in the detection tube 8, and the color change is caused by the change of the detection agent 2. In the length direction (from the air entry side to the air exit side), it is necessary to occur in order according to the ventilation rate. In the case where air containing a trace amount of ammonia of 50 μg / m ³ or less is to be measured, such as in an art museum or a clean room, the measurement air uniformly contacts the detection agent 2 during the measurement time. Flowing is essential. In other words, the detecting agent 2 existing near the air entry side does not change color, the detecting agent 2 existing downstream therefrom changes color first, or the detecting agent 2 does not react with ammonia in the air. , It becomes impossible to quantify the ammonia concentration by the discoloration length. Therefore, it is necessary to prevent such a phenomenon from occurring.
[0012]
As the detecting agent 2 when measuring the air having an ammonia concentration of 50 μg / m ³ or less, the acid and the pH indicator of the above formula (1) are coated on the surface of silica sand particles having an average particle size of 250 μm to 350 μm. It has been found that it is preferable to use a powder having a specific surface area determined by the BET method of 0.05 to 0.1 m ² / g and a powder pH adjusted to 4 to 6. In particular, when the crushed silica sand is classified and sized to have an average particle diameter of 250 μm to 350 μm, each particle surface may have irregularities. The air flows while dispersing well between the particles, and it is possible to prevent the air flow from short-circuiting or drifting in the powder.
[0013]
If the powder obtained by coating the surface of the silica sand particles with the acid and the pH indicator of the above formula (1) has a specific surface area value of less than 0.05 m ² / g by the BET method, the degree of unevenness of the particle surface is reduced. And the air flow flowing through the detecting agent 2 loaded in the detecting tube 8 becomes smooth, and short-circuiting or drifting occurs in the powder, resulting in good dispersion. No flow. On the other hand, when the value of the specific surface area by the BET method is more than 0.1 m ² / g, the surface of the particles has too much unevenness and the fluidity becomes poor when the particles are loaded into the detection tube 8. In this case, it is difficult to form a bridge or to form a uniform gap. In this case, too, the air flow is undesirably short-circuited or drifted. If the specific surface area of the powder is smaller than 0.05 m ² / g, or if the average particle size is larger than 350 μm, the reaction density becomes coarse and the boundary of discoloration becomes unclear, and the reading becomes difficult. It turned out to be difficult. Further, if the specific surface area is larger than 0.1 m ² / g or the average particle size is smaller than 250 μm, the boundary of discoloration becomes clear, but the sensitivity decreases, and the target concentration is measured. It becomes difficult to do. Therefore, the surface of silica sand having an average particle diameter of 250 μm to 350 μm is coated with the acid and the pH indicator of the above formula (1), and has a specific surface area of 0.05 to 0.1 m ² / g by the BET method. It is desirable to use powder as the detecting agent 2.
[0014]
This detection agent 2 is charged into the detection tube 8 of FIG. 1 by a predetermined length L, and air in which ammonia is present at 50 μg / m ³ or less is continuously supplied at a constant flow rate of 200 to 600 mL / min for at least 30 minutes. It was found that when the air was passed through the tube 8, the ammonia concentration in the air could be accurately determined from the integrated value of the total amount of air passed through the tube 8 and the discoloration length of the detection agent 2.
[0015]
FIG. 2 shows a state in which the exhaust port 6 of the ammonia detection tube 8 of FIG. 1 is fixed to a chuck 9 and connected from the chuck 9 to a suction means 11 such as a suction pump via a ventilation pipe 10. By the operation of 11, the air to be measured flows into the ammonia detection tube 8 from the air inlet 5 of the ammonia detection tube 8. A flow meter 12 is interposed in the ventilation pipe 10. The chuck 9, the ventilation pipe 10, the suction means 11, the flow meter 12, and the like are provided together with a flow integrator, a timer, and the like (all not shown) as one assembly device. 13 can be set to be portable. It is preferable that the suction means 11 is a device in which the exhaust gas has an effect on the measurement result.
[0016]
In order to quantify the ammonia concentration in air having a very small ammonia concentration of 50 μg / m ³ or less, the ammonia must not be adsorbed before touching the detecting agent 2 and 200 to 600 mL / m 3 It is necessary to continuously ventilate the pipe 8 at a constant flow rate within min for at least 30 minutes.
[0017]
Hereinafter, the present invention will be further described with reference to a measurement example using the ammonia detection tube 8 in FIG.
[0018]
Fluororesin Teflon (registered trademark) is used for the

stoppers

3a and 3b to be loaded into the detection tube 8, and the suction flow rate by the suction means (continuous suction type pump) 11 is set at about 400 ml / min and the air flow is set for 1 hour. A detecting agent 2 having phosphoric acid and a pH indicator carried on silica sand having an average particle size of about 300 μm (powder pH is about 5) was loaded into a tube 8 (inner diameter: φ4 mm) with a length L (30 mm). . The specific surface area of this powdery detection agent 2 measured by the BET method is 0.07 m ² / g. With this configuration, ammonia accompanying air introduced into the pipe 8 from the air inlet 5 first reacts with phosphoric acid, and the pH indicator changes from pale purple to pale yellow by a length corresponding to the progress of the neutralization reaction. Discolor. That is, it is assumed that all of the ammonia introduced into the tube 8 is consumed in the neutralization reaction with phosphoric acid, and the amount consumed in the neutralization reaction is quantified by the change in length. Specifically, the amount of phosphoric acid is adjusted so that the ammonia concentration at which the entire length of the pH indicator (L = 30 mm) changes color when aerated at a flow rate of 400 ml / min for 1 hour is 70 μg / m ^3. This amount of phosphoric acid was uniformly supported on silica sand, and the pH indicator was also uniformly supported on silica sand. This example is called a “high-sensitivity detector tube”. This is suitable for detecting ammonia concentration in museums and the like.
[0019]
Similarly, when aerated at a flow rate of 400 ml / min for 1 hour, the amount of phosphoric acid was adjusted so that the ammonia concentration at which the entire length of the pH indicator (L = 30 mm) discolored was 7 μg / m ^3. This amount of phosphoric acid was uniformly carried on the same silica sand as above, and the pH indicator was also uniformly carried on the silica sand. This example is referred to as an “ultra-sensitive detector tube”. This is suitable for detecting the concentration of ammonia in a clean room such as an electronic device manufacturing facility.
[0020]
In any of the detector tubes, in order to create the scale 7, a calibration gas is continuously generated using a dynamic calibration method (for example, a permeation tube method) or the like, and is ventilated under the above-described conditions. 3 (high-sensitivity type detection tube) and FIG. 4 (ultra-high-sensitivity type detection tube), respectively, based on the relationship between the color and the discoloration length of the detection agent 2, and the scale 7 is detected based on the calibration lines. Attached to the tube.
[0021]
The ammonia concentration was measured for the "high-sensitivity detector tube" obtained in this way for museums and for the "ultra-high-sensitivity detector tube" for clean rooms. Table 1 shows the outline of the building used for the measurement.
[0022]
[Table 1]

[0023]
The “air quality lab” in Table 1 is a research facility (air quality evaluation room) that minimizes chemical substances.
[0024]
In the test, in order to evaluate the detector tube of the present invention, ammonium in the air in the building to be measured was sampled by liquid collection using an impinger, and ammonium ions were quantified by ion chromatography (hereinafter referred to as “precision method”). "). The sampling by the precision method in the art museum was performed for 1 to 2 hours, and the sampling by the precision method was performed for 24 hours because the ammonia concentration in the clean room was even smaller.
[0025]
For both the high-sensitivity detector tube and the ultra-high-sensitivity detector tube, the suction time of the detector tube required for quantification was 1 hour (flow rate was constant at 400 ml / min), and the scale 7 of the detector tube was read immediately after the suction and measurement.
[0026]
First, in order to evaluate the consistency between the high-sensitivity detector tube and the ultra-high-sensitivity detector tube, measurements were taken at measurement locations A to E in the measurement target building by using both at the same time. The results are shown in FIG. As seen in FIG. 5, the ammonia concentration is obtained almost the same results in the range of 27 [mu] g / m ³ from 3.5 ug / m ^3, no significant difference was observed in measurement results of both the detecting tube You can see that.
[0027]
Next, the ammonia concentration in the museum was measured using a high-sensitivity detector tube. The results are shown in FIG. 6 in comparison with the measured values by the precision method. From the results of FIG. 6, although the measurement value of the detector tube in the range from 12 [mu] g / m ³ up to 86μg / m ³ shows a slightly higher than the precision method, there is a strong correlation measurement precision methods and detector tube (Correlation coefficient = 0.96), it can be seen that the detection tube according to the present invention becomes an accurate ammonia quantifier by proper calibration of its calibration curve.
[0028]
On the other hand, the ammonia concentration in the clean room was measured using an ultra-sensitive detector tube, and the result is shown in FIG. 7 in comparison with the measured value by the precision method. As is clear from the results of FIG. 7, a good correlation was obtained between the measurement result of the ammonia concentration by the detector tube according to the present invention and the precision method in the range from the ultraclean concentration to the ordinary clean room concentration (correlation coefficient = 0.995).
[0029]
In the above test, ventilation was performed at a flow rate of 400 mL / min for 60 minutes, but the present invention is not limited to this condition. A similar result can be obtained by continuously ventilating the detecting agent 2 according to the present invention into the tube 8 at a constant flow rate of 200 to 600 mL / min for at least 30 minutes or more. As a result, at least 6 L of air is brought into contact with the detection agent 2 continuously. According to the experience of the present inventors, it has been confirmed that the same measurement result as in the above-described test can be obtained when air is continuously ventilated at a flow rate of 200 mL / min or more and 600 mL / min or less for 30 minutes or more. Disturbances may occur in a range other than this flow rate, and when the total air volume to be continuously ventilated is less than 6 L, the sampling volume may be insufficient to accurately measure the ammonia concentration of 50 μg / m ³ or less. all right.
[0030]
In the above test, the detection tube 8 having the shape shown in FIGS. 1 and 2 is used, but the shape and dimensions of the detection tube 8 are not limited to those shown in the drawings. For example, the

plugs

3a and 3b to be loaded into the detection tube 8 are not limited to fluorocarbon resin. For the carrier of the detection agent 2, for example, zeolite or silica gel can be used besides silica sand. A non-volatile acid such as sulfuric acid can be used instead of phosphoric acid. Further, instead of using the entirety of the tube 8 as a transparent glass, only the portion where the detecting agent 2 is loaded may be formed of a transparent member, or a transparent plastic material such as an acrylic resin may be used instead of the glass.
[0031]
【The invention's effect】
As described above, according to the ammonia detector tube according to the present invention, anyone can easily and quantitatively measure a small amount of ammonia present in the air of an art museum, a clean room, or the like in real time. It can greatly contribute to storage management and yield management of electronic devices.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing one example of an ammonia detection tube of the present invention.
FIG. 2 is a device arrangement system diagram showing a measurement state of an ammonia concentration in air using the ammonia detection tube of FIG. 1;
FIG. 3 is a diagram showing a calibration curve of a high-sensitivity detection tube according to the present invention.
FIG. 4 is a diagram showing a calibration curve of an ultrasensitive detection tube according to the present invention.
FIG. 5 is a diagram showing measurement results of ammonia concentration measured at measurement places A to E by simultaneously using a high-sensitivity detector tube and an ultra-high-sensitivity detector tube according to the present invention.
FIG. 6 is a diagram showing a result of measuring an ammonia concentration in a museum using a high-sensitivity detector tube according to the present invention, in comparison with a measurement value obtained by a precision method.
FIG. 7 is a diagram showing a result of measuring an ammonia concentration in a clean room using an ultra-sensitive detection tube according to the present invention, in comparison with a measurement value obtained by a precision method.
[Explanation of symbols]
1 Glass tube 2 Detecting agent 3 Plug 4 Protective agent 5 Air intake 6 Exhaust port 7 Scale
8 Ammonia detection tube 9 Chuck 10 Vent tube 11 Suction means 12 Flow meter 13 Assembly equipment

Claims

An air in which an amount of ammonia of 50 μg / m ³ or less is present in a tube having an air intake port and an exhaust port using an ammonia detection tube in which a detection agent that reacts with ammonia and changes its color is transparently loaded from the outside of the tube. To determine the ammonia concentration as a measurement object, the air inlet of the detection tube is opened to the measurement space, and the exhaust port is connected to the suction means to allow the air in the space to reach a constant pressure of 200 to 600 mL / min. Aerating the concentration of ammonia in the air from the integrated value of the total amount of air that has passed through the tube and the discoloration length of the detection agent at a flow rate of at least 30 minutes or more; Determination of trace ammonia concentration.

The method according to claim 1, wherein the measurement space is a clean room or an art museum.

The detection agent is a powder obtained by coating a surface of silica sand particles having an average particle diameter of 250 μm to 350 μm with a reagent consisting of an acid and a pH indicator, and has a specific surface area of 0.05 to 500 μm according to the BET method. The method for quantifying a trace amount of ammonia according to claim 1, wherein the concentration is 0.1 m ² / g.

The method according to claim 3, wherein the silica sand has a powder pH of 4 to 6.

A detecting agent that changes color by reacting with ammonia is loaded in a pipe having an air inlet and an exhaust port so as to be visible from the outside of the pipe, the air inlet is opened to a measurement space, and the exhaust port is suctioned. The ammonia detection tube used in the quantitative method according to any one of claims 1 to 4, wherein the tube is connected to a tube to allow air in the space to flow through the tube.